Investigation Of Macro-and Meso-mechanical Properties And Damage Of 0Cr18Ni9 Stainless Steel During Deformation

Investigation of macro- and meso- mechanical properties and damage evolution characteristics of polycrystalline materials under the external loading (monotonic loading,cyclic loading etc) is one of the most common topic in material science, mechanics and mechanical designs in recent years. This in-depth research will not only help to deepen the essensial understanding of polycrystalline deformation and damage, but it is also of great significance to develop advanced methods for fatigue life prediction.Firstly this paper is a review of macro- and meso- mechanical properties and damage research both in China and abroad. Among mesoscopic experimental methods, the "Depth-Sensing Indentation (DSI)" technique,one of the most booming developments of advanced mechanical surface testing techniques,is an effective method to study the meso-characteristics of materials. The experimental and theoretical research of the macro- and meso-mechanics and damage behaviors of 0Crl8Ni9 stainless steel is carried out in two different kinds of deformation conditions.According to the characteristics of the depth-sensing indentation test, testing conditions of meso-mechanics in this paper are determined, which meet demands of both meso-mechanics tests and that of the indentation load which has the smallest indentation size effect (ISE),smallest holding time and the minimum indentation numbers of samples tested and so on.The relationship between macro- and meso-mechanical properties (including elasticity, plasticity, strength and strain hardening exponent, etc) during the process of monotonic deformation which has obtained statistical consistence in this paper is systematicly studied in use of static tensile tests in combination with indentation tests. The meso-mechanical properties during monotonic deformation are subject to normal probability distribution. Based on statistical characteristics of mesoscopic elastic modulus , a probability model is established to describe ductile damage.In combination of fatigue loading and indentation testing, we systematicly study the evolution of macro-indexes such as elasticity, plasticity, strength and strain hardening exponent in different stages of fatigue damage during cyclic deformation of materials. Macro- and meso- relations are studied with the help of meso-mechanical calculation algorithm and testing techiques. Meanwhile, micro-mechanisms of mechanical properties are on research by means of metallography and SEM analysis. Based on principal theories of damage mechanics and energy exhaustion results in fatigue tests, the probability expression developed in terms of fatigue damage varibles in definition of plastic work is applied to evolution research of surface damage during cyclic deformation of 0Cr18Ni9 stainless steel.