Unraveling stress inheritance and distribution mechanisms in the multi-stage processing of 2219 aluminum alloy tanks

Abstract

Controlling residual stress during the multi-stage processing of rocket tanks is pivotal to ensuring the safety and longevity of reusable launch vehicles(RLVs). This study established a multi-stage processing model to simulate the continuous fabrication of the tank, validated experimentally for accuracy. By integrating stress zoning with predefined fields, stress inheritance across processing stages was achieved, facilitating a detailed analysis of stress redistribution and inheritance throughout the tank’s continuous processing. The results reveal that under multi-stage processing, the peak stress in the spun tank bottom undergoes an "increase-decrease-increase" pattern. Following heat treatment, the stress distribution becomes uniform, whereas after welding, stress concentration emerges at the edges and the dome region, reaching a peak stress of 112.7 MPa. For the barrel segment, the overall peak stress follows an "increase-decrease" trend. After roll bending (RB), a high stress zone appears in the middle of the wall panel. After friction stir welding (FSW) of the longitudinal weld, stress concentration occurs at the weld seam, with annular high stress zones forming at both ends. Upon completion of the FSW of the girth weld, thermomechanical effects alleviate the initial stress concentration areas, which gradually shift to the girth weld and adjacent regions. Throughout the multi-stage processing, the peak stress rises from 43.8 MPa to 126.3 MPa. To regulate the tank’s residual stress, orthogonal experiments were utilized to optimize welding parameters, resulting in a 20.8 % reduction in peak stress. These findings provide theoretical support for optimizing the manufacturing process of RLVs.