How to Perform a UCI Hardness Test (ASTM A1038 Guide)

Verifying material hardness is a foundational part of quality assurance. For on-site hardness verification, the Ultrasonic Contact Impedance (UCI) method, governed by the ASTM A1038 standard, is the most effective approach available.

Understanding how to perform a UCI hardness test correctly is key to leveraging this powerful technique, and our experience shows that for obtaining fast, reliable data in the field, its performance is unmatched.

How to Perform a UCI Hardness Test: The 5 Steps of ASTM A1038

So, what is the correct procedure for a UCI test? The process itself is straightforward, but consistent, accurate results depend on getting the details right. Following these steps is what separates acceptable data from dependable data when you perform a UCI hardness test.

1. Get Your Surface Ready

Your first action is to prepare the test surface. The standard specifies optimal measurement conditions, including factors such as the distance between indents and the mounting method, all of which can affect the accuracy of the hardness values, especially for thin steel sheets (Burik & Pešek, 2014).

We typically recommend using a fine-grit flap disc or hand sanding to achieve a smooth, flat spot with a bright, metallic shine.

Related article: UCI: Solving Hardness Tests on Tricky Surfaces

2. Pick the Right Probe

Next, you must choose the appropriate probe for the job.

UCI probes come with different load forces, and using the right one is critical. A standard 50N (newton) load probe, found on workhorse models like our UCI-3000H, is ideal for most general steel and metal applications.

However, for testing thinner materials or delicate surfaces, a lighter 10N load probe is the correct choice.

3. Calibrate Your Machine

Before taking any measurements, calibrating your tester is a mandatory daily step. This involves testing a certified block to ensure your instrument is reading correctly, a core requirement of the ASTM A1038 standard.

It’s crucial to use a calibration block that is close to the expected hardness range of the material you'll be testing.

4. Go Ahead and Test

Now you are ready to perform the test.

Place the probe tip flat onto the prepared surface at a direct 90-degree angle. This is a critical detail in how to perform a UCI hardness test accurately. Apply firm, consistent pressure downward. The instrument will automatically perform the measurement and display the hardness value.

We always advise taking three to five readings in a small, concentrated area and using the average.

5. Keep Track of Your Numbers

A key feature of modern testers, like our popular UCI-1100H, is the capacity for internal data storage. Saving your measurements directly on the device does more than just record a number; it builds a history of your quality control, which is essential for traceability under ASTM A1038 guidelines.

Common Applications: Where UCI Testing Excels

So, where does this method actually get used? The portability and precision of testers compliant with ASTM A1038 make them incredibly useful for a number of specific jobs. We see them used most effectively in these situations:

- Welds and Heat-Affected Zones (HAZ): Testing the hardness across a weld is critical, and the tiny probe on a UCI tester lets you get precise readings right next to the weld bead without causing damage.

- Gears, Flanges, and Complex Shapes: You can't fit a complex gear into a traditional benchtop tester. A handheld UCI probe, especially a specialized one like our Elongated Probe Ultrasonic Hardness Tester (UCI-3300C), can get into tight spots with no problem.

- On-Site Inspections: For large assets like bridges or assembled machinery, UCI testing is the go-to solution. It provides lab-quality data right there on site.

- Thin-Walled Pipes and Tubing: The shallow indentation from a UCI probe is ideal for testing thinner materials where a heavier test method would give a false reading.

Related article: A Guide to Choosing an Ultrasonic Hardness Tester

So, What's the Big Deal with the ASTM A1038 Standard?

The ASTM A1038 standard is important because it provides a consistent and validated method for indirect hardness measurement, which is particularly useful for thin or surface-coated materials. 

Adhering to this standard helps minimize the influence of experimental variables and ensures that results are comparable and reproducible across different laboratories and applications (Burik & Pešek, 2014). In essence, the framework makes certain that:

- Your results are genuinely accurate.

- Your data is consistent with that from other facilities following the same procedure.

- Any guesswork is removed from the testing process.

By following the ASTM A1038 standard, you are not just taking a measurement. You are demonstrating a commitment to the quality and reliability of your products.

Qualitest: Your Partner in Precision Hardness Testing

We understand the operational need for hardness testing that is both reliable and straightforward.

We offer a complete and cost-effective line of ultrasonic portable hardness testers fully compliant with the ASTM A1038 standard. Our equipment is built to deliver trustworthy results, even in demanding industrial settings. Whether you are testing on the factory floor or in a quality lab, our user-friendly testers are made to meet your operational needs.

Please review our selection of ultrasonic portable hardness testers to find the ideal solution for your application. Our team of experts is available to help you select the most appropriate and cost-effective instrument for your needs.

References:

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