A control method for residual thermal stress and induced deformation in additive manufacturing

Abstract

The present invention relates to the field of geometric precision control of additive manufacturing formed parts, in particular to a method for controlling residual thermal stress and induced deformation of additive manufacturing, comprising the following steps: 1) Obtaining the residual stress distribution and Stress value; 2) According to the specific structural form of the formed part, design a continuous or discontinuous flexible base structure, so that the equivalent strain of the designed flexible structure is lower than the allowable deformation range, and has an equivalent elastic modulus lower than that of the body material. 3) By designing multiple sets of flexible substrate structures, the zonal release and active control of residual stress based on flexible structures can be realized. 4) During the additive forming process, the characteristic size of the flexible structure is gradually changed, the structural flexibility coefficient is reduced, and a gradient flexible structure is obtained to meet the service load requirements of the component. Through structural deformation, the space is discretized and the residual stress is released, and the discrete control of the spatial macroscopic thermal stress is realized within the allowable deformation range.

Description

technical field [0001] The invention relates to the field of geometric precision control of additive manufacturing formed parts, in particular to a method for controlling residual thermal stress and induced deformation of additive manufacturing. Background technique [0002] Additive Manufacturing (AM) technology is a rapid prototyping technology based on the discrete-accumulation principle, driven by the three-dimensional data of parts, and using the method of gradually accumulating materials to manufacture solid parts. It is also often called material increase manufacturing, layered manufacturing, solid freeform fabrication, 3D printing, etc. According to different energy beams, high-performance metal additive manufacturing technology can be divided into laser additive manufacturing, electron beam additive manufacturing and arc additive manufacturing. Different from the traditional "subtractive" manufacturing method, the additive manufacturing technology can accumulate an...

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Problems solved by technology

However, for additive manufacturing, only rigid fixation, adjusting heat input, welding rolling, hammering and other deformation suppression methods are feasible to a certain extent, but after the rigid fixation is removed, it is difficult to guarantee the size and structural accuracy of the original formed part. Adjusting the heat input has little effect on the macroscopic temperature field during the multi-channel reciprocating forming process

Colegrove of Cranfield University studied the application of rolling with welding in WAAM forming. Although this method can significantly reduce the residual stress in some positions where the transverse and longitudinal residual stress is concentrated, the effect of rolling may be limited to the first The release of the second and third types of internal stress, and the release of macroscopic internal stress is limited, in the literature [P. A. Colegrove, H. E. Coules, J. Fairman, et al. Microstructure and residual stress improvement in wire and arc additively manufactured parts through high-pressure rolling [J]. Journal of Materials Processing Technology, 2013, 23(10): 1782-1791.], it can be seen that after 25KN and 50KN pressure rolling, there is almost no difference in residual stress level, indicating that after a certain degree of plastic deformation, the microscopic Stress release, continuing to increase the degree of deformation, has little effect on macroscopic residual stress

At the same time, rolling with welding greatly increases the investment in WAAM equipment, and is not conducive to giving full play to its advantages of high-efficiency forming

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