Research on the Fatigue Strength of Brazed Joints in Gas-Wave Refrigerator Oscillating Tubes Based on Cohesive Zone Model

Abstract

Gas-wave refrigerators are widely used devices that utilize gas pressure to produce wave motion inside an oscillating tube for high-power refrigeration. This paper manufactures the core component of gas-wave refrigerators—the oscillating tubes—using hub and blade brazing. The tensile strength and fatigue life of the brazed joints were obtained through experiments. A finite element simulation based on the cohesive zone model determined that the critical damage stress of the brazed-joint brazing seam was 525 MPa. Under cyclic displacements of U = [0.4 mm, 0.5 mm, 0.6 mm], the errors between the simulated and experimental values of fatigue life are 9.09%, 4.38%, and 4.44%, respectively, which verifies the accuracy of the VUMAT subroutine of the cyclic CZM. The fatigue life relationship formula for the butt-brazed joints was fitted as y=5458.97x−3.545. Through the simulation analysis of the impact of the butt-joint angles on the fatigue life of brazed joints, it was found that as the butt-joint angle increased, the fatigue damage decreased, and the fatigue life increased. A finite element model of an oscillating tube with a DN (Nominal Diameter) of 285 × 450 mm was established to analyze the fatigue life of the butt-brazed structure of the rotor blade. The fatigue life of the brazed structure with a butt-joint angle of α = 45° increased by over 102.92% than that of α = 0°.

Keywords

• cohesive zone model
• brazed joints
• VUMAT subroutine
• fatigue life