Ball Indent Test Fixture

A manufacturer of automotive panels required a high-temperature system to quantify the quality and performance of various sheet metals at elevated temperatures. Our customer used a dual column tabletop load frame and a 3119 environmental chamber to provide the ideal functionality for applying controlled loads and temperatures. A custom set of fixtures was also required for holding the test samples. The fixturing had to meet several requirements:

• Ability to clamp sample from outside of chamber
• Flexibility to perform multiple tests on each sample
• Simple way to change indenters

Our Engineered Solutions Group worked with the customer to design the fixturing. Multiple indentation tests were required on samples that had been soaked at 450^° C (840^° F) and our customer was concerned because the specimens and fixtures had to be handled at such high temperatures. To reduce the potential for injury, we designed a tightening mechanism that was located outside of the heating zone to adjust the pushrods to clamp the specimen before each test. And this reduced the operator's exposure to the heated zones when specimen or indenter replacement was needed.

For performance at 450^° C, 303 and 304 stainless steels were selected. The user inserted a 1 x 3 inch sample into the test slot at the top of the lower pushrod and then loaded an indenter into the upper pushrod. We suggest that if the chamber and load string are already at temperature, the operator should close the door and tighten the indenter and the sample using the externally located lock nuts.

Additional features included water cooling to protect the load cell from error induced by temperature gradients and a storage shelf at the bottom of chamber to allow various indenter sizes to soak at elevated temperature.