A Guide to Choosing an Ultrasonic Hardness Tester

From a practical standpoint, ensuring the hardness of your materials is a fundamental quality checkpoint. While established testing methods have their place, the Ultrasonic Contact Impedance method offers a level of operational flexibility and efficiency that is hard to ignore.

We have seen a variety of instruments, and this solution consistently proves its value. For any application that requires non-destructive evaluation, we've found this approach to be exceptionally effective.

Understanding the UCI Hardness Tester Principle

The idea behind the UCI hardness tester principle is refreshingly direct. It operates with a small rod that has a Vickers diamond tip at its end, which vibrates at a high, ultrasonic frequency. 

When you apply this diamond point to the test material with a specified force, the vibrational frequency of the rod alters. This frequency shift is directly related to the contact area, which in turn depends on the material's hardness (Kleesattel, 1970; Gladwell, 1968; Schiller & Halim, 1990; Burik & Pešek, 2014). 

The instrument detects this minute alteration and computes the value, providing a direct hardness reading by converting the frequency change using calibration formulas (Schiller & Halim, 1990; Junek et al., 2017). This foundational UCI hardness tester principle is what proves its reliability in the field.

Key UCI Advantages in a Working Environment

The true strength of the UCI method for hardness testing becomes clear when you see its performance on the job. We’ve seen our clients benefit from a number of key UCI advantages.

- Truly Non-Destructive: In our professional opinion, this is its most significant benefit. The test produces a mark so small it’s typically invisible without magnification, making it perfect for in-situ testing (Gogolinskii et al., 2019). Professionals in the automotive and aerospace fields will appreciate this.

- True Portability for Fieldwork: This capability is a major asset for on-site quality assurance. The portability of these handheld devices allows your team to bring the inspection process directly to the workpiece, making the UCI method for hardness testing ideal for confirming the hardness of pipeline welds on location (Frehner, 2017).

- Adaptable to Complex Geometries: We have watched these instruments deliver accurate readings on challenging shapes and on small or thin parts where traditional methods are not applicable (Fu & Li, 2015; Gogolinskii et al., 2019). Getting a reliable result in these areas can be a consistent challenge with other portable tools. The method is also much faster than many conventional tests (Szilard, 1984).

A Clear Comparison: Where the Ultrasonic Contact Impedance Method Fits In

Making the right choice in testing equipment requires a clear view of where a technology performs best. We believe our role is to equip you to make the most appropriate choice for your application.

Next to Leeb and Benchtop Testers

We often field questions comparing this to Leeb testers. Leeb instruments are excellent for very large, coarse-grained components.

However, the Ultrasonic Contact Impedance method offers a clear advantage for thinner materials—down to 2-3mm—and for parts with more intricate shapes. And while a traditional benchtop unit is a benchmark for accuracy, it remains in the lab.

This method delivers results that are very close to benchtop standards, right where you need them.

Key Application Considerations

We believe in being transparent: this method has ideal conditions for its use. It provides its most accurate readings on materials with a fine-grained, uniform structure. 

For components with a very coarse grain, a Leeb instrument may provide a more representative bulk hardness value.

Acknowledging these details is essential for achieving dependable test results.

A Guide to Choosing an Ultrasonic Hardness Tester

Selecting the correct instrument is the most critical step. The process of choosing an ultrasonic hardness tester comes down to a clear-eyed assessment of your specific testing scenario. We guide our clients through this process by focusing on the details of the job.

Materials and Part Geometry

First, consider the materials you work with most often. Calibration for materials with varying elastic moduli is important for reliable outcomes (Junek et al., 2017; Burik & Pešek, 2014).

For instance, a client in the automotive supply chain needed to verify the case hardness deep within the root of a gear tooth. For a challenge like that, our Elongated Probe Ultrasonic Hardness Tester - UCI-3300C was the ideal solution. Its specialized probe is built for these exact hard-to-reach areas.

Surface Condition of Your Parts

The UCI probe needs clean, direct contact to function correctly. A surface that has been ground or smoothly machined is perfect.

The performance of the tester can be influenced by experimental conditions like sample thickness and surface coatings, so a consistent preparation process is key (Gogolinskii et al., 2019; Burik & Pešek, 2014).

We worked with a foundry that simply integrated a quick, localized grinding step to create a small, smooth pad for testing.

Manual Versus a Motorized Probe

You also need to weigh the benefits of a manual versus a motorized probe. For fieldwork, a manual probe like the one on our popular Portable Ultrasonic Hardness Tester - UCI-3000H offers great flexibility.

However, for a client running a three-shift manufacturing line, consistency was the top priority. They chose the UCI-3000M with its motorized probe.

Modern testers with integrated load sensors offer improved accuracy and reduced user dependence, which is a major benefit in a multi-operator environment (Frehner et al., 2017; Frehner, 2017).

Data Collection and Versatility

Finally, think about your operational needs. A fabrication shop that works with a huge variety of parts needed a single tool for everything.

For them, the Dynasonic Leeb / Ultrasonic Hardness Tester UCI-4000 was the perfect fit. It combines both UCI and Leeb methods, allowing them to use the best approach for any job.

Plus, its comprehensive data logging was essential for their quality certifications.

Qualitest: Your Partner in Hardness Testing

At Qualitest, we understand that you depend on accurate and repeatable hardness measurements.

Our selection of ultrasonic portable hardness testers, all based on the advanced Ultrasonic Contact Impedance method, gives you a cost-effective way to maintain your quality standards.

We invite you to examine our collection and see how they can improve your quality control workflow. Visit our product page to review the details. 

Let us help you with the process of choosing an ultrasonic hardness tester that is the ideal configuration for your operation.

References

- Kleesattel, C. (1970). Contact impedance meter. Part IV. Ultrasonics, 8, 39-48. https://doi.org/10.1016/0041-624x(70)90799-7

- Junek, M., Janovec, J., & Ducháček, P. (2017). Dependence of ultrasonic contact impedance hardness on Young’s modulus of elasticity of creep-resistant steels. **, 6, 27-32. https://doi.org/10.21014/acta_imeko.v6i1.325

- Gogolinskii, K., Syasko, V., Umanskii, A., Nikazov, A., & Bobkova, T. (2019). Mechanical properties measurements with portable hardness testers: advantages, limitations, prospects. Journal of Physics: Conference Series, 1384. https://doi.org/10.1088/1742-6596/1384/1/012012

- Szilard, J. (1984). Quicker, simpler hardness testing using ultrasonics. Ultrasonics, 22, 174-178. https://doi.org/10.1016/0041-624x(84)90033-7

- Frehner, C., Mennicke, R., Gattiker, F., & Chai, D. (2017). Advancements of ultrasonic contact impedance (UCI) hardness testing based on continuous load monitoring during the indentation process, and practical benefits. **.

- Gladwell, G. (1968). The calculation of mechanical impedances relating to an indenter vibrating on the surface of a semi-infinite elastic body. Journal of Sound and Vibration, 8, 215-228. https://doi.org/10.1016/0022-460x(68)90228-9

- Frehner, C. (2017). NEW GENERATION OF UCI PROBES WITH ACCURATE LOAD DETECTION: OVERVIEW AND PRACTICAL BENEFITS. **.

- Fu, J., & Li, F. (2015). A finger-like hardness tester based on the contact electromechanical impedance of a piezoelectric bimorph cantilever.. The Review of scientific instruments, 86 10, 103902. https://doi.org/10.1063/1.4932186

- Schiller, J., & Halim, A. (1990). A method for measuring hardness or elastic material properties under a load by the ultrasonic contact-impedance method. **.

- Burik, P., & Pešek, L. (2014). Effect of Experimental Factors on Hardness Measurement Using the UCI Technique. Materials Science Forum, 782, 61 - 64. https://doi.org/10.4028/www.scientific.net/msf.782.61