Determination of the Plastic Flow Stress Curve of Metal Based on the Data of Micro-Impact Intrusion of a Spherical Indenter
摘要
The accurate measurement of the tensile stress–strain curve is crucial for predicting the performance and service life of different constructions. Among different methods, instrumented indentation has emerged as a promising approach to assess the mechanical behavior of materials. Traditional static indentation devices are heavy and require the use of special accessories during the testing of industrial products: chains, magnetic grips, and clamps, which must create a closed force system. From this point of view, devices using dynamic indentation are preferable. It is shown that a dynamic portable hardness tester with the special electronic unit can be used for the stress–strain curve evaluation. An algorithm was developed for determining the flow stress based on the values of the velocity restitution coefficient, as well as dynamic and static Meyer hardness. The main objective of this paper is to critically evaluate the relationships between the flow stress curve measured in standard tensile tests and the indentation flow stress obtained from the developed dynamic instrumented indentation test. Studies were carried out on static and dynamic indentation and static tensile behavior of 4 metals: steel, brass, copper, and aluminum. It is shown that for dynamic indentation with strain rates up to 4000 s-1 the Tabor’s theory can be used. For the first time, it demonstrates the possibility of plotting the plastic flow curve of metals based on dynamic micro-impact indentation data, with average strain rates in the range of 600-4000 s-1. This research contributes to the development of a consistent methodology for the prediction of the static behavior of metals using dynamic instrumented indentation as a method of nondestructive testing.