Equipment FAQ

Claus Kleesattel's invention, the Ultrasonic Contact Impedance (UCI) method, has been employed in the metal-processing industry for over half a century.

The UCI hardness testing method is a non-destructive testing technique that uses ultrasonic contact impedance to measure the hardness of materials. It is particularly useful for testing metals and alloys, as it provides accurate and reliable results without damaging the test specimen. The UCI method is based on the principle that the frequency shift of an ultrasonic wave is proportional to the indentation size produced by a Vickers diamond indenter. This relationship allows for the determination of the Vickers hardness value, which is a measure of a material's resistance to penetration under a specific load.

Principles of UCI Hardness Testing

The UCI hardness testing method works by exciting a metal rod with a Vickers diamond indenter attached to its end into longitudinal oscillation at a frequency of approximately 70 kHz using piezoelectric transducers. When a test load is applied, a frequency shift occurs as the diamond penetrates into the material, with the frequency shift being greater for larger indentations and smaller for harder materials. The frequency shift is proportional to the size of the indentation produced by the Vickers diamond, which is described by equation:

The frequency shift (f) is proportional to the area of indentation (A) generated by the Vickers diamond, the force applied in the test (F), and the Young's Modulus of the material (E elastic).

Variations in Young's modulus among materials lead to distinct sets of curves. It's noteworthy that certain steel alloys, like Cr-Mn steels, belong to the same material class due to their consistent Young's modulus. However, materials such as austenitic stainless steels, duplex steels, or Inconel may necessitate individual calibration against an appropriate reference. Furthermore, adjustments may also need to account for surface roughness. Thus, maintaining similarity in material processing is crucial.

Advantages of using portable equipment for UCI hardness testing

Portable hardness testing equipment, such as those using the UCI (Ultrasonic Contact Impedance) method, offers several advantages over traditional benchtop hardness testers:
1. On-site assessment: Portable devices allow for in-situ hardness measurements, which can be particularly useful for inspecting components that cannot be moved or are difficult to access, complex geometries such as gears and pipe bends.
2. Flexibility: Portable equipment allows for measurements in difficult-to-reach locations and during the production, manufacturing, or assembly process, as it is not limited to the vertical position like conventional stationary hardness testing machines
3. Quick and economical: Portable UCI hardness testers can perform the test procedure relatively quickly, making them suitable for use in production environments and maintenance tasks.
4. Non-destructive: Unlike traditional hardness testing methods, such as Rockwell, Brinell, or Vickers tests, which require the test piece to be brought to the testing device, UCI hardness testing is non-destructive, as it does not require the removal of material from the test specimen.
5. Accuracy: The UCI method provides accurate hardness measurements, especially on fine-grain, homogeneous materials that are of sufficient mass and thickness to negate the effects of sympathetic oscillations and flexural waves produced by probe tip vibrations.
6. Versatility: The UCI method is suitable for testing small parts, thin-walled products, components with difficult access to the testing area, and surface-hardened layers.

UCI hardness testing using TEQTO’s TQ-4C series

Application of the UCI method

The UCI hardness testing method, based on ultrasonic contact impedance, finds applications in various industries due to its portability, speed, and reliability. Some extended applications of the UCI method include:
1. Incoming goods inspection: UCI hardness testing is suitable for inspecting incoming goods to ensure they meet the required hardness specifications.
2. Mix-up checks: The method can be used to verify the hardness of components to prevent mix-ups in manufacturing processes.
3. Heat-affected zone (HAZ) testing: UCI is valuable for testing the heat-affected zone of welds, providing insights into the hardness changes in these critical areas.
4. Testing of difficult-to-reach areas: UCI is effective for testing areas that are challenging to access, such as gear teeth, bearings, and other confined spaces.
5. Automated applications: Due to its simplicity and speed, UCI is a preferred solution for automated hardness testing applications, enhancing efficiency in production environments.
6. Surface processing inspection: UCI can be used to assess the hardness of components after surface treatments to ensure the desired hardness properties are achieved.
7. Weld inspection: The method is suitable for inspecting welds to verify the hardness of the welded joints, ensuring structural integrity.
8. Coat hardness measurement: UCI can be utilised to measure the hardness of coatings, such as those on gravure cylinders, providing crucial information on coating quality and durability.

Types of materials

The UCI (Ultrasonic Contact Impedance) method is versatile and suitable for testing various types of materials. According to the provided sources, the UCI method can be used to test the hardness of:

1. Fine-grained materials of any shape and size, especially where material properties need to be processed with narrow tolerances, such as for determining strain hardening on drop forged parts.
2. Small parts, thin-walled products, and components with difficult access to the testing area, including surface-hardened layers.
3. Serial parts after heat treatment, after surface processing, welds, and coat hardness measuring on gravure cylinders.
4. Materials with different values of Young's modulus, as the frequency shift in the UCI method depends on this material constant.
5. Components where classic hardness testing methods like Vickers, Rockwell, or Brinell are not practical or possible, such as in incoming goods inspection, production control, or maintenance on integrated components.

Industries

Some extended industries where the UCI method is commonly used include:

1. Aerospace: In the aerospace industry, the UCI method is used to test the hardness of critical components like turbine blades, landing gear, and structural elements to ensure their integrity and durability under extreme conditions.
2. Automotive: Automotive manufacturers use the UCI method to assess the hardness of engine components, gears, shafts, and other parts subjected to high stress and wear, ensuring quality and performance.
3. Manufacturing: The UCI method is valuable in manufacturing industries for testing the hardness of machined parts, tools, dies, and moulds to maintain quality standards and optimise production processes.
4. Oil and gas: In the oil and gas sector, the UCI method is employed to evaluate the hardness of pipelines, valves, and drilling equipment to prevent failures and ensure safety in harsh operating environments.
5. Medical devices: The UCI method is applied in the medical device industry to test the hardness of implants, surgical instruments, and medical equipment to meet regulatory requirements and ensure patient safety.
6. Electronics: Electronics manufacturers use the UCI method to assess the hardness of components like circuit boards, connectors, and housings to guarantee reliability and longevity of electronic devices.
7. Mining: In the mining industry, the UCI method is used to test the hardness of materials used in mining equipment, tools, and infrastructure to withstand abrasive and high-impact conditions.
8. Construction: The UCI method finds applications in the construction industry for testing the hardness of structural steel, concrete, and building materials to ensure compliance with safety and quality standards.
9. Railway: Railway companies utilise the UCI method to assess the hardness of rail tracks, wheels, and components to maintain operational efficiency and safety in rail transportation systems.
10. Marine: In the marine industry, the UCI method is employed to test the hardness of ship components, propellers, and marine structures to withstand corrosion and harsh marine environments.
11. Power generation: Hardness testing is crucial for assessing the integrity and residual life of in-service components in power generation equipment, such as gas turbines, steam turbines, and generators.
12. Metalworking: Portable UCI hardness testers are used in the metalworking industry to measure the hardness of screws, bolts, and other components.
13. Maintenance and production: Portable UCI hardness testers are used in maintenance tasks and production control to ensure the quality and durability of components.

Limitations

While UCI hardness testing offers many advantages, there are some limitations to consider:
1. User-dependent: The accuracy of UCI hardness testing can be influenced by the skill and experience of the operator, as the method may become more user-dependent if the test is not performed in a steady location orthogonal to the test surface.
2. Indentation size: The method may be less accurate for tiny indentations, as even a slight probe movement during the test can significantly impact the reading.
3. Calibration: Proper calibration is required to ensure the accuracy of the test results, and calibration samples with known hardness values should be used to achieve accurate results for specific materials.
4. Best suited for homogeneous materials: The UCI method is best suited for materials having a homogeneous microstructure. The small size of the sampled area is unable to provide consistent and dependable results on most cast and forged materials

In conclusion, the UCI hardness testing method using portable equipment offers a non-destructive and quick solution for measuring the hardness of metals and alloys in various industries. While there are limitations to consider, the advantages of on-site assessment and the ability to test in-situ make UCI hardness testing a valuable tool for maintaining the integrity and durability of components in power generation, metalworking, and other industries.

TEQTO’s answer to portable UCI hardness testing:  TQ-4C series

The TQ-4C is a high-precision handheld instrument designed for demanding production and field conditions. Operating on the Ultrasonic Contact Impedance (UCI) method, this tester is specifically tailored for measuring the hardness of carbon construction steels across fundamental hardness scales such as Brinell (HB), Rockwell (HRC), and Vickers (HV). It is suitable for a wide range of materials, including heat-proof, corrosion-proof, and non-corrosive steels, as well as plated coatings and items with complicated configurations.

The TQ-4Combi is a high-precision handheld instrument equipped with brand-new software, designed for non-destructive testing of production quality. It combines the advantages of both UCI and Leeb methods for precise control of metals and alloys hardness. Suitable for a wide range of applications, including carbon and structural steels, hard-surfaced items, heat-resistant and corrosion-resistant steels, non-ferrous metals and alloys, electroplated coatings, items of complex configuration, thin-walled and small-sized items, and large items and heavy-duty equipment.

The Leeb rebound hardness test method was developed in 1975 is one of the four most used methods for testing metal hardness. This portable method is mainly used for testing sufficiently large workpieces, mainly above 1 kg. It is well-suited for testing ferrous and non-ferrous materials and can be converted to various hardness scales like Vickers, Brinell, Rockwell C & B, and Shore.

Principles of Leeb hardness testing method

The Leeb method employs a dynamic technique where the hardness of a material is determined by the ratio of the rebound velocity to the impact velocity of a moving impact body. This method is particularly suitable for solid parts like castings and forgings.

The test involves the impact of a specimen body on the surface being tested, followed by the measurement of the rebound velocity in comparison to the incident velocity. The results obtained are directly related to the hardness of the material being tested, with higher hardness leading to increased hardness values and rebound speeds.

A – Peak value of the approach phase. B – Peak value of rebound phase. t – Time. U – Voltage

Advantages of using portable equipment for Leeb hardness testing method

• Portability and accessibility: Portable hardness testing equipment offers the advantage of being easily transportable and accessible for on-site testing without the need to move large or heavy components to a laboratory. These portable devices allow measurements to be taken directly on the spot, eliminating the need to cut samples or transport them to a testing facility, enhancing convenience and efficiency.

• Versatility and application range:Portable hardness testers provide versatility in testing various materials, including steel, cast iron, stainless steel, bronze, aluminium alloys, brass, and copper, making them suitable for a wide range of applications. The ability to measure hardness in different positions and directions, along with the capability to test a variety of materials, enhances the versatility and applicability of portable hardness testing equipment.

• Cost-effectiveness and efficiency:Portable hardness testers offer a cost-effective solution for hardness testing, especially for large components that are challenging to test using conventional benchtop methods. These devices provide a quick, economic, and non-destructive testing solution, allowing for efficient hardness measurements in a matter of seconds, saving time and resources.

• Ease of use and technology: Portable hardness testing equipment is designed to be user-friendly, with features like high contrast LCD screens, automatic angle adjustment systems, internal data storage, USB connectivity for data transfer, enhancing ease of use and data management.

Leeb hardness testing using TEQTO’s TQ-3C series

Application of the Leeb method

The application of portable Leeb hardness testers is diverse and includes various industries and scenarios. Here are the key applications based on the provided sources:

1. Failure analysis: In failure analysis of pressure vessels, steam turbine generator sets, and other equipment, portable Leeb hardness testers play a crucial role in assessing the hardness of components to identify potential weaknesses or defects. By conducting hardness tests on critical parts, these devices help in diagnosing failures, determining material properties, and ensuring the integrity and safety of equipment in various industrial settings.
2. On-site testing: Portable Leeb hardness testers are designed for on-site testing of heavy, large, or installed parts, making them ideal for applications where moving the test samples to a laboratory is impractical or impossible. These devices allow for quick and convenient hardness testing directly at the location of the component, eliminating the need for sample transportation and reducing testing time and costs.
3. Mechanical assembly parts: Portable Leeb hardness testers are widely used in installed mechanical assembly parts for hardness testing. They provide a practical solution for assessing the hardness of various components in mechanical assemblies, ensuring quality and reliability. The ability to measure hardness directly on assembled parts without disassembly makes portable Leeb hardness testers valuable tools for quality control and maintenance in mechanical applications.
4. Material sorting: Portable Leeb hardness testers are used for material sorting in metal material warehouses, where quick and accurate hardness measurements are essential for categorising materials based on their hardness properties. These devices enable efficient sorting of metal materials based on their hardness levels, ensuring proper material selection for specific applications and enhancing material management processes in warehouses.
5. Heavy workpieces and limited spaces: Portable Leeb hardness testers are suitable for testing heavy workpieces with very limited space, where traditional benchtop testers may not be practical or feasible. The compact size and portability of these devices allow for hardness testing in confined spaces or on large workpieces where access is restricted, providing flexibility in testing various components.

Types of materials

The Leeb hardness testing method is versatile and applicable to a wide range of materials. Here are the key types of materials suitable for Leeb hardness testing:

1. Metals: Leeb hardness testing is commonly used for testing various metal materials, including alloy steel, stainless steel, grey cast iron, ductile iron, steel, iron, aluminium, and copper. This method is particularly effective for measuring the hardness of steel products, cast steel, and cast iron, making it a valuable tool for assessing the hardness of metallic components in different industries.
2. Alloys: The Leeb hardness tester is suitable for testing alloys, which are combinations of metals or a metal with other elements. Alloys like alloy tool steel, copper, bronze, and other metal alloys can be effectively tested using the Leeb hardness testing method. The ability to measure the hardness of alloys accurately is essential for quality control and material characterization in industries where alloy components are prevalent.
3. Ceramics: While not explicitly mentioned in the provided sources, the Leeb hardness testing method can also be applied to ceramics. Ceramics are materials that can undergo hardness testing to evaluate their resistance to deformation and scratching, making them suitable candidates for Leeb hardness testing. The hardness of ceramics is crucial in applications where surface integrity and resistance to scratching are essential factors for performance and longevity, highlighting the importance of hardness testing in this material category.
4. Other materials: The Leeb hardness testing method can also be used for testing materials beyond metals and alloys. The versatility of the Leeb hardness tester allows for testing a wide range of materials, including elastomers, polymers, plastics, films, rocks, and minerals, depending on the specific application requirements and material characteristics.

Industries

Here are the industries that commonly use the Leeb hardness testing method:

1. Manufacturing industry: The manufacturing industry extensively uses the Leeb hardness testing method to measure the hardness of materials like steel, iron, aluminium, and copper. This industry relies on hardness testing for quality control and ensuring that components meet specified hardness requirements. Hardness testing is fundamental in manufacturing processes to assess the durability, strength, and quality of materials used in producing a wide range of products across different sectors within the manufacturing industry.
2. Mechanical engineering: In mechanical engineering, Leeb hardness testers are employed for testing installed mechanical assembly parts, bearings, screws, bolts, and other mechanical components. This application ensures that mechanical parts meet hardness standards for performance and reliability. The ability to measure hardness in various mechanical components is crucial for maintaining quality standards and ensuring the integrity of mechanical systems in industries such as automotive, aerospace, and machinery manufacturing.
3. Construction industry: The construction industry utilises Leeb hardness testing for inspecting stationary structures like bridge halls and pipes used for oil and gas transport. Hardness testing in this industry helps ensure the structural integrity and safety of construction materials and components. By assessing the hardness of construction materials, the construction industry can verify material quality, durability, and suitability for specific applications in building infrastructure projects.
4. Heavy machinery and equipment: Industries dealing with heavy machinery and equipment benefit from Leeb hardness testing for analysing failure in pressure vessels, steam turbine generator sets, and other equipment. This application helps diagnose failures and determine material properties critical for equipment safety. The ability to conduct hardness tests on heavy workpieces with limited space is particularly valuable in industries where large machinery components need to be tested for hardness properties.
5. Metal material warehouses: Metal material warehouses use Leeb hardness testers for material sorting based on hardness levels. This application ensures proper categorization of metal materials according to their hardness properties, facilitating efficient material management processes within warehouses. By employing Leeb hardness testing for material sorting, metal material warehouses can streamline inventory management and ensure that materials are used appropriately based on their hardness characteristics.

Limitations

The Leeb hardness testing method, while widely used for assessing material hardness, has certain limitations that users should be aware of.

1. Sample weight and rigidity: One of the key limitations of the Leeb hardness testing method is related to the weight and rigidity of the sample being tested. If the sample lacks sufficient weight and rigidity, it can absorb much of the impact, leading to inaccurate results. The ideal sample weight for accurate testing is ≥5kg (10lbs), and samples below this weight may require additional support or coupling with a heavier material.
2. Sample preparation: The preparation of the sample surface is crucial for accurate hardness testing. Samples should have a flat, clean, and metallic shine surface without oxide layers, rust, or other contaminants. Any alterations to the sample through cold processing or thermal processing can affect the accuracy of the hardness test results.
3. Surface roughness and curvature: The surface roughness of the sample at testing points must meet specific requirements (Ra ≤ 1.6), and the curvature radius of the testing and nearby surface should be larger than 30mm. If the sample surface is not flat, appropriate supporting rings should be used, and the tester probe must be as close to perpendicular to the test surface as possible throughout the test.
4. Sample Thickness and Absorption Layer: Samples must be thick enough and have a sufficient surface absorption layer for accurate hardness measurement. The thickness of the sample and the surface absorption layer requirements vary based on the type of impact device used. Samples that do not meet these thickness requirements may lead to inaccurate hardness measurements.
5. Magnetization and temperature: Samples should not be magnetised, as the magnetic field can interfere with the impact device signal, leading to inaccurate results. Additionally, the surface temperature of the sample should be less than 250°F (120°C) to ensure accurate hardness testing
6. Test location and edge distance: The test location should be a minimum distance from the edge of the part to avoid edge effects. It is recommended to test a minimum of 5mm (0.2 inches) from the edge, with 10mm (0.5 inches) or greater distance being preferable for accurate hardness measurements.

In conclusion, the Leeb hardness testing method offers a portable, efficient, and versatile solution for assessing the hardness of a wide range of materials across various industries. While the method provides numerous advantages such as portability, cost-effectiveness, and ease of use, it also comes with certain limitations that users should consider for accurate and reliable hardness measurements.

 Understanding the principles of the Leeb hardness testing method, its application range, and the types of materials suitable for testing is essential for utilising this technique effectively. Industries such as manufacturing, mechanical engineering, construction, heavy machinery, and metal material warehouses benefit from the practicality and convenience of Leeb hardness testing in ensuring material quality, structural integrity, and equipment safety.

By acknowledging the limitations related to sample weight, rigidity, surface preparation, roughness, curvature, thickness, magnetization, temperature, test location proximity to edges, users can optimise their hardness testing processes and enhance the accuracy of their results. Proper sample handling and adherence to testing guidelines are crucial for mitigating these limitations and obtaining precise hardness measurements.

 Overall, the Leeb hardness testing method remains a valuable tool for quality control, material characterization, failure analysis, and material sorting in diverse industrial settings. By balancing its advantages with an awareness of its limitations and best practices, users can leverage the benefits of Leeb hardness testing to ensure the reliability and performance of materials and components in their respective applications.

TEQTO’s answer to portable Leeb hardness testing:  TQ-3C series

The TQ-3C is another high-precision handheld instrument engineered for demanding production and field conditions. Operating on the Leeb method, this tester provides robust control over the hardness of various materials, including structural, tool, corrosion-proof, heat-proof, and non-corrosive steels and alloys, as well as alloys of nonferrous metals, cast iron, aluminium, bronze, and brass. It is suitable for measuring the hardness of components with surface hardening and high-frequency current hardening, as well as complex-shaped items.

Here are two different physical methods which are particularly recognized in the practical field: the static Ultrasonic Contact Impedance (UCI) method and dynamic rebound hardness testing (Leeb). The decision as to which method is to be used mainly depends on the testing task. For selecting the suitable method of measuring, primarily user has to know two main parameters of the tested object: Weight and Wall thickness. If testing object mass is more than 5 kg and it’s wall thickness is more than 10 mm this is the case to use dynamic rebound hardness testing.

The Leeb method creates quite a large short duration force at the moment of the impact. Thin and lightweight materials flex causes erroneous values. A solution for testing small simple shaped objects is a machined support that matches the contour of the back surface of it. The support reinforces the object to make it ridged.

The UCI method is recommended for testing fine grained material having any shape and size. It is especially used where material properties are to be processed with narrow tolerances, e.g. for determination of strain hardening on drop forged parts. With the small indent of the UCI probes, determination of the hardness can be made on welded parts in the critical area of the weld, the heat affected zone (HAZ).

Magnetic Particle Inspection (MPI) is a widely used nondestructive testing technique designed to detect surface and near-surface discontinuities in ferromagnetic materials like iron, nickel, cobalt, and their alloys. This method works by introducing a magnetic field into the object being tested. If there are any cracks or flaws, they disrupt the magnetic field, causing magnetic flux leakage. To visualize these imperfections, small ferrous particles (either dry powder or suspended in a liquid) are applied to the object's surface. These particles gather at the areas of flux leakage, forming visible indications that mark the location of the defects.

MPI can use two different magnetization methods: direct and indirect. In direct magnetization, an electric current passes directly through the test object, creating a magnetic field within the material. Indirect magnetization uses an external magnetic source to magnetize the object without passing current through it. The type of electrical current used for magnetization also plays a crucial role. Alternating current (AC) is often used for detecting surface defects due to its shallow penetration. For subsurface flaws, full-wave direct current (FWDC) or half-wave direct current (HWDC) is preferred, as these currents penetrate deeper into the material, providing more comprehensive inspection.

Types of electrical currents used in MPI

The selection of the right electrical current for MPI depends on the geometry of the part, the type of material, the depth of the discontinuity, and the required magnetic field penetration. Each type of current has specific characteristics that make it suitable for certain applications:

• Alternating Current (AC): Best for detecting surface-level defects, AC creates a magnetic field that remains mostly on the surface of the object due to a phenomenon called the "skin effect." The current alternates polarity rapidly (50-60 cycles per second), meaning it does not penetrate deep into the material. This limits its use for subsurface detection but makes it ideal for identifying surface discontinuities.

• Full-Wave Direct Current (FWDC): FWDC is used when deeper penetration is required to find subsurface discontinuities. Unlike AC, FWDC can magnetize thicker cross-sections of material, making it more suitable for larger or thicker parts where surface inspection is insufficient.

• Half-Wave Direct Current (HWDC): HWDC provides a balance between surface and subsurface detection. Its pulsating current helps move the magnetic particles during inspection, increasing the likelihood of detecting surface cracks. This mobility of particles, combined with deeper penetration than AC, makes HWDC effective for both surface and shallow subsurface inspection.

An AC electromagnet is most effective for detecting surface-breaking indications, while some form of DC, such as FWDC or HWDC, is better suited for identifying subsurface defects. MPI is a versatile inspection method used in industries such as aerospace, automotive, and construction, where the integrity of metal components is critical.

TEQTO’s answer to portable MPI inspection: Teqtoflow series

Eddy current testing (ECT) is a widely-used non-destructive testing (NDT) method that employs electromagnetic induction to detect surface and subsurface flaws in conductive materials. This technique works by passing an alternating current through a coil, generating a magnetic field. When the coil is placed near a conductive material, such as metals, it induces eddy currents within the material. These eddy currents mirror the magnetic field of the coil and flow in closed loops. Any disruptions in the material, such as cracks or changes in material properties, alter the flow of the eddy currents. These changes are detected by monitoring the impedance variations in the coil, signaling the presence of flaws or discontinuities.

ECT has a wide range of applications across industries like aerospace, power generation, and petrochemical, and is primarily used for surface inspections and tubing examinations. It is particularly sensitive to small cracks and defects, especially in non-ferromagnetic materials. For instance, it is extensively used in inspecting steam generator tubes in nuclear plants and heat exchangers in petrochemical facilities. Additionally, ECT can measure the thickness of coatings and detect corrosion or pitting in materials. However, the method is best suited for conductive materials and its depth of penetration is limited by the material's properties, such as conductivity and permeability.

Applications and variations of eddy current testing

ECT is highly versatile, with numerous variations tailored for specific applications. For surface inspections, ECT is ideal for detecting small surface flaws, even through coatings or paint, and is especially useful for ferromagnetic and non-ferromagnetic materials. Advanced variations, such as full saturation ECT, allow for inspecting partially magnetic materials by suppressing variations in permeability through an applied magnetic field. This variation is used in specialized inspections of materials like duplex alloys or thin ferromagnetic materials.

For subsurface flaws, remote-field eddy current testing is commonly used in carbon steel tubing to detect general wall loss or corrosion, though it is less sensitive to small cracks or pits. Additionally, ECT can be used for measuring electrical conductivity and coating thickness in various industries. Despite its limitations, such as depth penetration and the requirement for conductive materials, ECT remains an essential tool for maintaining safety and structural integrity in critical infrastructure.

TEQTO’s answer to portable eddy current testing: Eddy-current flaw detector ED-45

Ultrasonic testing or ultrasonic flaw detection is a type of non-destructive Testing that employs high-frequency ultrasound waves to perform inspections and measurements. Ultrasonic inspection is often used to discover and evaluate flaws, measure dimensions, characterize materials, and more.

Sound waves with a frequency greater than 20 kHz and a 1.9 cm or less wavelength at atmospheric pressure are known as ultrasound waves. In simpler words, ultrasounds are sound waves having frequencies greater than the human hearing limit. 

Ultrasonic Flaw Detection uses these ultrasonic sound waves to detect flaws inside a solid metal or concrete object without causing any damage to its original structure. 

In most conventional UT applications, ultrasonic pulses with center frequencies ranging from 0.1 to 15 MHz and border frequencies up to 50 MHz are transmitted through materials to discover internal defects or characterize materials. One typical example is ultrasonic thickness measurement, which measures the test object’s thickness by monitoring pipe corrosion.

Ultrasonic Flaw Detection is most typically done on steel and other metals and alloys, although it may also be used with poorer resolution on concrete, wood, and composites. Steel and aluminum construction, metallurgy, manufacturing, aviation, vehicles, and other forms of transportation are among the industries that use it.

Theory behind ultrasonic flaw detection

Ultrasonic Flaw Detection is based on the principle that sound waves produce mechanical vibrations in different media such as liquids, solids, or gas. The common modes of propagation of sound waves in solids are shear waves and longitudinal waves. This technique utilizes the flow of ultrasound in solid metal, concrete, or wood objects.

When any soundwave passes through a medium, it has a particular frequency, wavelength, and velocity. If the wave encounters the edge of a different medium (i.e. a flaw), it is immediately transmitted back to the same end where it can be detected. This is the fundamental theory behind Ultrasonic Flow Detection.

Principles Of ultrasonic flaw detection

Ultrasonic Flaw Detection is broadly based on three principles, i.e. frequency, velocity, and wavelength.

1. Frequency (f)

Frequencies ranging between 500 kHz and 10 MHz per second are used in most ultrasonic fault detection applications. Sound energy flows effectively through most common solids and liquids at higher frequencies. 

2. Wavelength (λ)

It is the distance between two successive points as a wave travels in a medium and forms a wave cycle. The minimal detection limit for the ultrasonic flaw detection technique is 1/2 wavelength.

3. Velocity (c)

The speed of a sound wave varies depending on the medium through which it travels and is influenced by the density and elasticity of the medium. Sound waves move at varying speeds. The specific velocity of ultrasounds is detected in ultrasonic flaw detection.

Reflection at the edge of the flaw

When ultrasounds traveling through a material hit a barrier with another medium, a portion of the energy is reflected back, and a fraction of it will be transmitted. The reflection coefficient, or quantity of energy reflected, is proportional to the relative acoustic impedance of the two materials.

Acoustic impedance is a material attribute defined as density times sound speed in a specific material. The reflection coefficient as a percentage of incident energy pressure may be computed for any two materials using the formula.

              Z2 – Z1

R =      ——————       

             Z2 + Z1

In this formula,

R = reflection coefficient representing the percentage of energy reflected 

Z1 = acoustic impedance of 1st material

Z2 = acoustic impedance of 2nd material

Procedure of the ultrasonic flaw detection

Ultrasonic flaw detection is essentially a comparison method. A trained operator performing ultrasonic flaw detection identifies specific echo patterns corresponding to the echo-response from good parts and from representative flaws using appropriate reference standards, knowledge of sound wave propagation, and generally accepted test procedures. To determine the condition of a test piece, the echo pattern from it can be compared to the patterns from these calibration standards.

Ultrasonic flaw detection using straight beam

Ultrasonic flaw detection using straight beam testing with contact, delay line, dual element, or immersion transducers is commonly used to detect cracks or delaminations parallel to the test piece’s surface, as well as voids and porosity. It works on the basic premise that sound energy propagating through a medium will continue to propagate until it either disperses or reflects off a boundary with another material, such as the air surrounding a distant wall or found inside a crack. 

Ultrasonic flaw detection using transmission mode

In some cases, the ultrasonic flaw detection is completed using transmission mode. In this method of ultrasonic flaw detection, sound energy moves between the two transducers located on the sides opposite of the test piece. 

If the sound path contains a large flaw, the beam will be obstructed, and the sound pulse will not reach the receiver.

Angle beam testing for ultrasonic flaw detection

While using Angle Beam Testing for ultrasonic flaw detection, cracks or other discontinuities perpendicular to the surface of a test piece to that surface can not be detected using straight beam test techniques. 

Such flaws can appear in welds, structural metal parts, and a variety of other critical components.

Ultrasonic transducers 

A transducer is a device that can change the state of energy from one direction to another. Electrical energy may be converted into sound energy using ultrasonic transducers and vice versa.

Standard transducers for ultrasonic flaw detection use a dynamic element consisting of polymers, composites, or piezoelectric ceramics. When a high-voltage electrical pulse is delivered to this element, it vibrates over a certain frequency range and creates sound waves. An electrical pulse is produced when an incoming sound wave vibrates this element.

Five types of ultrasonic transducers are often used in fault detecting operations. 

• Contact transducers
• Immersion transducers
• Delay line transducers
• Angle beam transducers
• Dual element transducers

Modern ultrasonic flaw detectors 

The modern and advanced ultrasonic flaw detectors are microprocessor-based small and portable equipment. They’re perfect for factory and industrial usage, and they provide an ultrasound wave that an experienced operator may readily understand when detecting and classifying faults in test parts. A wave screen, an ultrasound pulse/receiver, a data recording module, and hardware and software for signal collection and analysis are all included in the range. Pulse amplitude, damping, and shape may all be modified to improve transducer performance. Similarly, receiver gain and bandwidth may be adjusted to improve signal-to-noise ratios.

TEQTO’s answer to portable acoustic flaw detection: TQ-92 - Acoustic flaw detector

In engineering, a coating is classified as a material that is deposited onto the surface of another material (commonly referred to as a substrate) to specifically enhance the properties of the surface for functional or decorative purposes.

A number of factors dictate the type of coating that would be applied to the material surface which include cost, life of service of the component, substrate the coating is applied to, size and shape of the component, component environment and most importantly the function of the component that is to be coated. Coatings are applied to surfaces according to specific standards, such as ISO, BS, ASTM, DIN etc., additionally, the thickness of the applied coating is dictated by its function and cost. Typical coating thicknesses can range from a few nanometres to several centimetres. As an example, Titanium Zirconium (TiZr) coatings can be 1nm to 5nm thick, while anodic films can range from 0.5μm to 150μm, paint coatings can be up to a couple of millimetres in thickness.

Coatings fall into two distinct categories: layers formed by reactions involving the modification of the surface of the substrate material and those that are deposited on the surface of the substrate material.

Coatings formed by reactions involving the surface of the substrate tend to form a layer at the substrate surface by chemically acceleration reactions that naturally take place in order to protect the substrate from for example corrosion. Anodising is one of the most notable of these methods which can be used to protect the underlying substrate material.

The latter types of coatings are more varied and offer different properties depending on the coating that is applied to the substrates.

Most common types of coatings applied to substrates are those applied in solution by a reduction reaction of ions and include electro-deposited coatings (chrome, gold, silver etc) or by electroless deposition methods (eg. Electroless nickel plating).

Why measure coatings?

Coatings that have functional roles, are usually highly regulated by standards BA, ASTM, DIN, ISO, QUALICOAT, QUALINOD etc. Coatings performing specific functions have to be regulated. In the example of the TiN coating in the engine, the coatings are applied to strict tolerance limits. Above the specified limits, the coatings would impede the function of the engine components, while below these limits the components may fail without adequate protection from the frictional stresses it is applied for. When components are manufactured the coatings are checked to ensure they are within these parameters; alternatively, coatings can be measured at various intervals during the life of a component, to ensure that they have not been worn away. Coatings wearing away can cause corrosion to occur in the substrate material potentially causing catastrophic failure, especially if that component is used in the automotive, aerospace, rail or marine industries.

A second reason to measure coatings is strictly from a financial standpoint. Current prices of gold, platinum and silver for example, mean that companies that manufacture components with these coatings can be losing money if they add too much of the coating to the components. An example is the electroplated silver on copper wires used in cabling for the aerospace sector. In order to ensure that wires meet the strictest standards for this sector, it may be common to apply more silver to the copper wire, to ensure the wire is in specification. For manufacturers this can translate into an accumulated cost of $250,000 per year in just over-depositing the silver coating. Another example is the automotive industry applying paint and lacquer to the car bodies. By saving 1μm on the paint/ lacquer that is over applied, the manufacturers can save £1 per car. In 2019 approximately 2.3 million cars were registered in the UK, suggesting that a potential of £2.3 Million can be saved per year (Society of Motor Manufacturers and Traders, 2020). Thus, the need to measure the coatings becomes clear.

TEQTO’s answer to portable coating thickness gauge measurement: CT-07 - Coating thickness gauge

Ferrite measurement is a vital non-destructive testing (NDT) technique used to determine the amount of ferrite present in austenitic and duplex stainless steels. Ferrite content significantly impacts the mechanical properties, corrosion resistance, and weldability of these materials. The most common method employed for ferrite testing is magnetic induction. This process uses a probe with an exciter coil that generates a low-frequency magnetic field. When placed near a steel sample, this magnetic field is amplified by ferrite grains, and the resulting voltage change is measured to determine the ferrite content.

Maintaining the right balance of ferrite is crucial. If the ferrite content is too low, it can lead to solidification cracking, particularly during welding. On the other hand, excessive ferrite can reduce the material’s corrosion resistance and negatively affect mechanical properties. By assessing ferrite levels, industries can ensure that the material is tough, resistant to cracking, and maintains its intended performance, especially in challenging environments.

Applications of ferrite testing

Ferrite testing is widely used across several industries, including oil and gas, chemical processing, power generation, mining, and manufacturing. It is especially important in environments where corrosion resistance and structural integrity are crucial. For example, in oil refineries and chemical plants, equipment and piping made from stainless steel are often exposed to harsh, corrosive substances. Maintaining the proper ferrite content ensures that these components can withstand such conditions.

In terms of objects, ferrite measurement is applied to a variety of critical equipment, including:

• Welds and cladding: Ensuring that weld seams in stainless steel pipes and tanks have the correct ferrite content to prevent cracking during cooling and operation.
• Pressure vessels and tanks: These large industrial containers, used for storing liquids or gases, require accurate ferrite content to ensure their strength and longevity.
• Heat exchangers: Used in power generation and petrochemical industries, where the integrity of stainless steel components is key to safe and efficient operation.
• Piping systems: Commonly found in power plants, chemical plants, and oil refineries, where ferrite testing helps prevent material failure due to stress or corrosion.

Ferrite testing is particularly beneficial for stainless steel grades like 300 series austenitic stainless steel (e.g., 304/L, 316/L) and duplex stainless steels, where the ferrite percentage directly impacts toughness, ductility, and resistance to corrosion and cracking.

Importance and benefits of ferrite testing

Ferrite testing is quick, affordable, and provides immediate results, making it an essential part of quality control in industries where material failure can result in costly downtime or hazardous situations. By maintaining the correct ferrite content, companies can enhance the performance, safety, and reliability of their stainless steel components, avoiding issues like premature failure, high maintenance costs, or safety risks due to structural weaknesses.

In summary, ferrite testing is a critical NDT method used across a variety of industries to assess and control the material properties of stainless steel, ensuring long-term durability, reliability, and safety.

TEQTO’s answer to portable ferrite testing: TQ-7 - Ferrite meter

Induction heating is a non-contact method of heating electrically conductive materials, primarily metals, using electromagnetic induction. The process relies on creating an alternating magnetic field around the material, which induces an electric current (eddy currents) within it. These currents generate heat due to the material's electrical resistance, effectively heating it from within. Induction heating is widely used for various industrial applications, including shrink-fitting, hardening, brazing, welding, and preheating before further processing.

How does induction heating work?

The induction heating process involves three main components:

1. Induction coil (inductor): A coil through which alternating current (AC) flows, creating a magnetic field around the material being heated.
2. Workpiece (material): The metal or material placed within the magnetic field generated by the inductor.
3. Power source: A power generator that supplies the AC to the coil.

When the workpiece is placed inside or near the induction coil, the magnetic field induces eddy currents within the material, generating heat due to the material's electrical resistance. The key advantage of induction heating is its ability to heat only the specific area required without affecting surrounding materials, ensuring precise, efficient, and uniform heating.

Applications of induction heating

Induction heating is commonly used in industries like automotive, aerospace, energy, and manufacturing for tasks such as:

• Shrink-fitting: Heating a part to expand it and then cooling it to fit tightly onto another component.
• Hardening: Heat-treating materials to improve their surface hardness and wear resistance.
• Brazing and welding: Joining metals using a filler material, where induction heating provides controlled and localized heating.
• Preheating: Preparing materials for further processes like forging or machining.

Advantages of induction heating

1. Precision: Induction heating allows for highly localized heating, reducing the risk of overheating surrounding areas.
2. Speed and efficiency: The process is rapid, heating materials quickly and efficiently, leading to reduced processing times.
3. Energy savings: Since the heating occurs directly within the material, there is minimal energy loss, making it an energy-efficient method.
4. Non-contact heating: The material is heated without direct contact with the heating element, reducing the risk of contamination or wear.
5. Safety: Induction heating minimizes the exposure to open flames, making it a safer option in industrial environments.

Induction heating equipment from TEQTO

TEQTO offers a wide range of induction heaters suited for various industrial applications, including our Suretherm, Easyheat, and Easytherm series. These advanced heaters feature precise temperature control through dual sensor technology, ensuring stress-free heating for tasks like shrink-fitting, hardening, and component assembly. Whether you're working with small bearings or large industrial parts, TEQTO’s induction heaters provide efficient, controlled heating for every task.

Induction heating is a versatile, efficient, and safe method widely adopted in many industries. By leveraging advanced induction heaters, professionals can achieve precise, reliable, and energy-efficient heating tailored to specific applications.

The ultrasonic pulse-echo method is a widely used non-destructive testing (NDT) technique that helps assess the internal integrity of materials by detecting flaws such as cracks, voids, delaminations, and other internal discontinuities. This method uses high-frequency sound waves (ultrasound) to penetrate a material and measure the time it takes for the sound waves to bounce back (or "echo") from internal features or defects. The pulse-echo method is particularly effective for inspecting materials like metals, concrete, ceramics, and composites.

How does the ultrasonic pulse-echo method work?

The ultrasonic pulse-echo method involves the following key steps:

1. Pulse generation: A transducer generates high-frequency ultrasonic waves and sends them into the material being tested.
2. Propagation and reflection: As the sound waves travel through the material, they are reflected back when they encounter a boundary between different materials or a defect such as a crack or void.
3. Echo detection: The transducer receives the reflected sound waves (echoes) and measures the time taken for them to return.
4. Data interpretation: The time between the emission of the pulse and the reception of the echo is analyzed to determine the location, size, and nature of any internal flaws.

The time it takes for the echo to return indicates how far the wave traveled within the material. By analyzing the strength and timing of these echoes, inspectors can create a detailed image of the internal structure of the material and identify any defects or inconsistencies.

Applications of the ultrasonic pulse-echo method

The ultrasonic pulse-echo method is widely used across various industries, including:

• Construction: Inspecting concrete structures for voids, cracks, and delaminations to ensure the structural integrity of buildings, bridges, and tunnels.
• Manufacturing: Evaluating welds and detecting defects in components like pipes, pressure vessels, and machinery.
• Aerospace and automotive: Inspecting critical components such as engine parts, airframes, and gears for internal defects that could compromise safety and performance.
• Energy: Assessing the condition of power plant equipment, pipelines, and wind turbine blades for material degradation and fatigue.

Advantages of the ultrasonic pulse-echo method

1. Non-destructive: The pulse-echo method allows for internal inspection without causing damage to the material, making it suitable for critical components and structures.
2. High accuracy: It provides precise data on the size, location, and nature of internal flaws, enabling accurate assessments of material integrity.
3. Versatility: This method can be used on a wide range of materials, including metals, concrete, composites, and ceramics.
4. Portable equipment: Ultrasonic pulse-echo systems are portable and can be used for both on-site inspections and in-lab testing.
5. Depth measurement: The pulse-echo method can detect flaws deep within a material, making it ideal for assessing thick or complex structures.

Ultrasonic pulse-echo equipment from TEQTO

TEQTO offers a comprehensive range of ultrasonic pulse-echo flaw detectors and ultrasonic pulse-echo tomography systems designed for the non-destructive testing of various materials. These advanced systems, provide precise three-dimensional imaging and defect detection. Our pulse-echo equipment is ideal for detecting internal cracks, voids, and delaminations, ensuring the safety and reliability of materials in industries such as construction, manufacturing, aerospace, and energy.

By using the ultrasonic pulse-echo method, professionals can detect hidden defects in materials and structures without compromising their integrity. This method is a reliable and effective solution for ensuring the safety, quality, and performance of critical components across a range of industries.

The ultrasonic pulse velocity (UPV) method is a non-destructive testing (NDT) technique used to evaluate the quality, uniformity, and structural integrity of materials, particularly concrete, rock, ceramics, and other solid materials. By measuring the speed at which ultrasonic pulses travel through a material, the UPV method can assess its density, strength, and detect potential flaws such as cracks, voids, and honeycombs. This technique is widely used in construction, civil engineering, and material testing applications to ensure the reliability and durability of structures.

How does the ultrasonic pulse velocity method work?

The UPV method operates on the principle that the speed of sound waves through a material is influenced by its density and elastic properties. Here’s how the process works:

1. Pulse generation: A transducer emits high-frequency ultrasonic pulses into the material being tested.
2. Pulse propagation: The ultrasonic waves travel through the material, interacting with any defects or variations within its structure.
3. Detection and measurement: A receiving transducer on the opposite side of the material (or at a different location on the same side) detects the transmitted pulse. The time taken for the pulse to travel from the transmitter to the receiver is recorded.
4. Velocity calculation: The velocity of the pulse is calculated based on the distance between the two transducers and the time it took for the pulse to travel through the material.

Higher velocity readings generally indicate a material of higher density and integrity, while lower velocities may suggest the presence of internal defects such as cracks, voids, or inconsistencies.

Applications of the ultrasonic pulse velocity method

The UPV method is highly versatile and used in various industries to assess material quality and integrity:

• Construction: UPV is widely used to evaluate the quality of concrete structures such as buildings, bridges, tunnels, and dams. It helps detect flaws like cracks, honeycombs, and voids that may compromise structural safety.
• Civil engineering: The method is used to assess the strength of concrete and rock in infrastructure projects, ensuring that materials meet design specifications and safety standards.
• Manufacturing: UPV can be applied to assess the quality of materials such as ceramics, composites, and refractory materials, ensuring they are free of internal flaws that could lead to failures.
• Preservation and restoration: UPV is used in the assessment of historical structures to detect degradation or damage in masonry and concrete, aiding in restoration efforts.

Advantages of the ultrasonic pulse velocity method

1. Non-destructive: UPV allows for thorough material assessment without damaging the structure or material being tested.
2. Accurate assessment: By measuring the velocity of ultrasonic waves, the method provides precise information about the material's uniformity, density, and strength.
3. Defect detection: UPV can identify internal defects such as cracks, voids, and honeycombs that may not be visible on the surface, ensuring early detection and timely maintenance.
4. Applicable to various materials: UPV can be used on a wide range of materials, including concrete, rock, ceramics, and composites, making it a versatile testing method.
5. Portable and efficient: UPV equipment is compact and portable, making it suitable for on-site inspections as well as lab-based evaluations.

Ultrasonic pulse velocity equipment from TEQTO

TEQTO offers a selection of 2 ultrasonic pulse velocity testers (UPVT). These advanced devices are designed to deliver accurate, non-destructive assessments of material strength and integrity. Whether you need to evaluate the uniformity of concrete structures or detect hidden defects in rock or masonry, UPV testers provide reliable, high-precision results.

By using the ultrasonic pulse velocity method, engineers and inspectors can ensure that materials meet safety and quality standards, detecting potential issues early and helping to prevent costly failures in the future. This method is an essential tool for ensuring the durability and performance of critical structures across industries.

Low-frequency electromagnetic testing is a non-destructive testing (NDT) method that utilizes alternating magnetic fields to detect metal thinning, corrosion, and other material defects in ferromagnetic objects. This technology is especially useful when inspecting items that are difficult to access from multiple sides or require a non-contact testing method.

How does low-frequency electromagnetic testing work?

Low-frequency electromagnetic testing works by applying a magnetic field to a ferromagnetic material, typically in the range of 5–30 Hz. As the magnetic field interacts with the metal, it creates alternating currents within the material, which can be measured by the testing equipment. Defects such as thinning of the material or corrosion alter the magnetic properties in localized areas, causing changes in the magnetic field. The testing equipment detects these changes, helping identify areas that need further inspection or repair.

What are the benefits of low-frequency electromagnetic testing?

• Non-contact inspection: No need for direct contact with the material, making it ideal for items that are hard to access or contain coatings.
• No surface preparation required: Unlike other methods, the material does not need to be cleaned or prepped unless performing in-line inspections.
• Ability to detect both surface and subsurface defects: The technology can identify inner and outer defects, providing a comprehensive view of material integrity.
• Wide application: It works effectively on a variety of ferromagnetic materials, such as pipelines, storage tanks, and heat exchangers.

What types of defects can be detected with low-frequency electromagnetic testing?

This method is especially effective in detecting:

• Metal thinning: Reductions in wall thickness due to corrosion or wear.
• Pitting corrosion: Small holes or pits that form on metal surfaces, weakening the material.
• Cracks: Particularly in welds or areas under stress.
• Other localized defects: Any changes in the material’s magnetic properties due to damage or alteration.

What are the key features of low-frequency electromagnetic testing equipment?

• Wide frequency range: The system typically operates in frequencies between 5 Hz and 30,000 Hz, allowing for inspection of both ferromagnetic and non-ferromagnetic materials.
• Wireless data transfer: Many systems, such as the CORSAIR-16, use Bluetooth for real-time data transfer to a laptop or tablet, making it easy to monitor and record results.
• No permanent magnets: The absence of permanent magnets ensures that the device won’t attract debris, making it suitable for continuous use.
• Flexible transducer options: The equipment can be used with different types of transducers, such as flat, concave, or in-line cylindrical transducers, depending on the shape and size of the material being tested.

What materials can be tested using low-frequency electromagnetic testing?

Low-frequency electromagnetic testing is particularly effective for ferromagnetic materials like carbon steel and low-alloy steels. However, the technology can also be used on non-ferromagnetic metals such as austenitic steels and other non-ferrous alloys when the system operates in higher frequencies (1,000–30,000 Hz).

Is calibration necessary for low-frequency electromagnetic testing?

Yes, calibration is important to ensure accurate results. Calibration can be done using test blocks or known reference materials to validate the system’s measurements. This step enhances the precision of defect size estimation and ensures the reliability of the inspection.

How do you interpret the results of low-frequency electromagnetic testing?

Results are typically displayed on a laptop or tablet screen in the form of A-Scan (amplitude and phase) or C-Scan (color-coded map). The data represents variations in the material's magnetic properties, with defect areas showing a change in the signal strength or phase. Operators can use on-screen cursors to estimate defect sizes and depths.

What are the advantages of low-frequency electromagnetic testing over other NDT methods?

• No need for surface preparation: Unlike ultrasonic testing, low-frequency electromagnetic testing does not require the surface to be clean or smooth, making it ideal for use in harsh environments.
• Detection of both inner and outer defects: This method can simultaneously detect internal and external defects, providing a more comprehensive inspection.
• Non-invasive and fast: Since it’s a non-contact method, it’s quick and minimizes disruption to the material being tested.
• Applicable in various industries: Commonly used in industries like oil and gas, power generation, and transportation for inspecting large structures like pipelines and storage tanks.

What are the limitations of low-frequency electromagnetic testing?

While this method is effective for many applications, it may not be suitable for:

• Non-ferromagnetic materials at low frequencies (below 1,000 Hz).
• Extremely small defects: While it’s excellent at detecting significant thinning and corrosion, very fine defects may require higher resolution techniques like ultrasonic testing.
• Complex geometries: Some testing systems may struggle with very complex or irregularly shaped surfaces.