Mechanical Behavior of Typical Material in Whole Load Processes Under Complex Stress State

To investigate the material's mechanical appearance under complex stresses in the whole load processes, solid cylindrical specimens are used for the tension-torsion tests. Meanwhile, how to realize the fixed proportional (C(σ/τ)) tension-torsion loading test in the life cycle of solid cylindrical shaft is derived. 24 series of experiments of 16MnR carbon steel and 304 stainless steel specimens have been done under different C values. Based on test results, the calculation method of equivalent true stress and strain of solid cylindrical specimen is derived. Hence, the influence of different stress state on the plastic limit strain is described by triaxial stress coefficient (TS). Results show that: the plastic limit stress of the two materials has a minimum value through the change of TS values, which defined as stress stationary point. The plastic limit strain of the two materials is in inverse proportion to TS. When the stress state of a point is determined, the plastic limit stress and strain can be calculated by the formula presented in this paper. Difference of material make the limit stress-TS and limit strain-TS mathematical models different, so that the model should be calibrated respectively. © 2017, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.