Research On Fatigue Problem Of Copper Rod Notched Under Tension And Compression Cycle--Simulation And Experimental Analysis

Engineering components inevitably exist stress concentration regions or defects, such as gaps, cracks, grooving, etc. And the area that contains defects or stress concentration, not only the local stress may increase but also cause the local triaxial stress state. To study the problem that engineering structures often work under cyclic loading, people often use notch specimens to investigate the mechanical behavior of materials under cyclic loading. And since the complexity of the stress-strain relationship of notched, fatigue of notched specimens lack of more in-depth understand, therefore it has more important practical significance to study notched specimen. In this paper, in the combination of experiment, theory and simulation, strain amplitude controlled cyclic loading test and tension and compression cycle simulation analysis is conduct on solid copper smooth round rod and notched round rod specimens. Based on the existing theory of fatigue, further study on notch fatigue problems is needed to enrich and improve fatigue theories of notched specimens.This paper adopts4kinds of notched specimens and smooth specimens, fatigue tests were carried out in0.003,0.0035,0.004and0.005strain amplitude (For notched specimens, strain amplitude is the maximum strain at the notch root strain amplitude). And on the basis of experiments, fatigue life law of materials is analyzed with a different state of stress concentration and the same strain amplitude.As how to determinate the local stress-strain of notched is a complex problem, we found it exists obvious deficiency when we use local stress-strain method for life prediction of notched. The Chaboche model was adopted to describe the cyclic plastic behavior of materials, and numerical simulation is performed to analyze the change of stress and strain of notched specimens under cyclic load. This paper analyses some factors that affecting the life of notched specimens, especially the analysis of the effect of stress triaxiality and stress gradient on the fatigue life of notched specimens. Fatigue life prediction on stress gradient method found stress gradient have a great influence on notched specimen.In this paper, with the help of microscope, fatigue fracture is analyzed. How gap radius, strain amplitude and loading ways influence the macro fracture morphology were analyzed respectively. Provide the experimental basis for the quantitative analysis of fatigue fracture.