How thick must a test piece be according to the Brinell test guidelines?

In the Brinell hardness test, the thickness of the test piece is crucial to ensure accurate results and prevent failure during testing. The correct requirement is that the thickness of the test piece must be at least 8 times the depth of the indentation made by the hard steel or carbide ball. This guideline is established to ensure that the test piece can adequately support the load applied during the test without yielding or deforming in an unintended manner.

If the test piece is not thick enough—less than 8 times the impression depth—the material could exhibit characteristics that would affect the accuracy of the hardness measurement. Insufficient thickness might lead to the impression merging with other impressions or the material below the surface being affected, thereby skewing the readout of hardness. Therefore, adhering to this guideline is essential for reliable test results.