To a considerable degree hardness is an empirical value which depends on many details involved in the measuring process. In the present work, hardness values were measured in the depth range 2 – 800 nm using microhardness, nanoindentation and scratch hardness tests on fused silica, steel and sapphire. It is shown that overestimation of hardness values for steel and sapphire with the nanoindentation method can be directly related to the relative height of pile-ups observed on the topography image of the indentation imprint. It is also shown that the scratch hardness test is a promising technique for nanoscaled hardness measurements.
This article is devoted to the study of means and methods for non-destructive testing mechanical properties of polyethylene gas pipelines that have been in operation for 25–55 years. In order to assess mechanical properties, stress at yield was chosen as a key parameter. Stress at yield is determined from the results of tensile tests and is associated with the limiting circumferential (hoop) stress, determined from the results of tests for short-term pressure. Tensile tests require sample cutting and the shutdown of pipelines’ service. To solve this problem of nondestructive testing of pipelines, tests were carried out using the methods of Shore, Leeb and dynamic instrumental indentation. According to the test results, it was revealed that the correlation coefficient between the values of stress at yield and hardness, obtained by the method of dynamic instrumental indentation, is 0.98 which confirms the possibility of the evaluation of the mechanical properties of pipelines by the method of dynamic instrumental indentation.
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