Method for measuring residue stress and metal material elastic-plastic mechanical property by continuous press mark method

Abstract

The invention discloses a method for measuring the residue stress and metal material elastic-plastic mechanical property by a continuous press mark method. The residue stress is simulated by exertingtransverse load onto a test sample without residue stress; continuous ball press mark experiments are performed; a dimensionless function expression between the press mark power ratio and the metal material mechanical property at different depth is built; the press mark experiment is performed on materials to be tested; the real press mark power ratio is obtained from a load-displacement curve; bya reverse analysis solving method, three groups of different press-in depths or more are selected so that the total sum of the error absolute value between the inversion press mark power ratio and the real press mark power ratio is minimum; at the moment, the values of the yield strength, residue stress and strain hardening indexes are solved values.

Description

Technical field [0001] The invention belongs to the field of material mechanical property characterization, and specifically relates to a method for measuring the yield strength, strain hardening index and residual stress of metal materials by adopting a continuous ball indentation method. Background technique [0002] In the machining and manufacturing process, uneven plastic deformation of materials or temperature mismatches will cause residual stress in the parts. Due to the existence of residual stress, it has an important influence on the fatigue strength, corrosion cracking, material brittleness of components, and the dimensional stability and processing accuracy of components. The ability to accurately measure the residual stress in the structure is of great significance for evaluating the mechanical properties of materials. Because the formation mechanism of residual stress is very complicated, so far there is no reliable theory and method to evaluate residual stress. Th...

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Problems solved by technology

In actual engineering measurement, it is difficult to find a sample without residual stress as a reference, which also increases the complexity of the experiment

Second, the dimensional analysis method, which is based on the Π theorem, establishes a dimensionless equation between the indentation response parameter and the mechanical parameters of the metal material, and obtains an accurate function expression through numerical simulation analysis. This method does not require a reference sample The unknown parameters can be obtained, because multiple unknown parameter groups (E,σ y , n and σ r ) in the dimensionless equation, so it is difficult to get an accurate functional expression to describe the relationship between indentation parameters and material parameters

[0004] At present, dimensional analysis and numerical simulation methods are widely used in the field of indentation technology. In order to simplify the dimensional equation, some researchers introduced the apparent strain into the dimensionless equation to make the equation independent of the strain hardening exponent. Although the dimensional equation simplified, but the presence of residual stresses was not considered in these studies

In addition, in order to establish multiple dimensional equations, multiple indenters of different shapes are used as analysis parameters, which also increases the complexity and cost of the experiment.

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