Variation of Plastic Strain Range of Copper Alloys in Fatigue Process

The plain bending fatigue tests were conducted under a constant stress amplitude with zero mean stress at a frequency of 60 Hz.The stress-strain hysteresis loops and variation of plastic strain range Δe p with number of cycles of pure copper C1100P-1/4H and brass C2801P-1/4H were obtained. Based on the model of dislocation multiplication and annihilation, it can be induced that Δe p is only determined by movable dislocation density ρ and Burgers vector b by Δe p=ρb, and ρ can be expressed as a function of the number of stress cycles n, thus a formula between Δe p and n was established. By using the formula, the theory curves between plastic strain range Δe p and number of stress cycles n were obtained, and compared with experiment data. It is showed that the theory curves is well agreement with the experiments data, so it can be concluded that the formula can be used to predict the fatigue life of the Cu alloys.