7A52 Aluminum Alloy MIG Welding Residual Stress Reliable Measurement based on Hole-Drilling Method

摘要

To analyze the welding residual stress distributions for aluminum alloy medium and thick plates after the process of MIG welding, a residual stress testing system based on hole-drilling method was designed by virtual instrument and NI data acquisition card. To improve the accuracy and reliability of measurement results, the elasticity modulus error, strain gauge pasted error, and strain reading value time error were emphatically analyzed. The elasticity modulus error could be corrected by the curve that is fit to data measured in different MIG welding joint areas. The final measurement error caused by the strain gauge pasted error was reduced to 0 in 24 hours after the strain gauge was pasted. The final measurement error caused by the strain reading value time error was reduced to 0 in 150 minutes after the residual stress began to be measured. The experiment of MIG welding residual stress measurement was carried out on 10 mm thick 7A52 aluminum alloy plates. The results showed that the distributions of residual stresses on two sides of the weld seam were basically symmetrical about the weld center. The maximum tensile stress appeared in the fusion zone, and the maximum transverse residual stress σ_y and the maximum longitudinal residual stress σ_x were 96 MPa and 185 MPa, respectively. The residual stresses from the fusion zone to heat affected zone were all tensile stresses, which were higher than the residual stresses in the center of the welding seam. Smaller compressive stresses appeared in the base metal.