A Study on the Tensile Test Behavior and Fatigue Life Rate of Bolted Joint in Elastic Region Tightening and Bolted Joint in Plastic Region Tightening of the SCM435H

摘要

Bolted joint in plastic region tightening acquire high tightening strength and high degree of efficiency of intensity. In case of high-cycle fatigue testing, a lot of time and efforts are needed to know correct data analysis and mathematical model. The SN curve at a particular stress level represents the formation of the persistent slip band, its strain-hardening and crack formation (necking) and step-wise crack propagation locally in the test specimen. However, in the tensile test the whole specimen deforms plastically and strain-hardens homogeneously as the stress increases. Number of cycles to failure under cyclic loading depends only on the elongation accumulated in the test and Young's modulus of the material. Therefore, this study confirm a usefulness of compare experimental value with high cycle fatigue equation that shows relationship between the tensile test and the S-N curve of bolted joint in plastic region. As a result, plastic region tightening increase in 1.32 times of (#DELTA#1/l_0)_f value rather than bolted joint in elastic region tightening in tensile test.