Abstract
Wire and arc additive manufacturing of stiffened ribs for fabricating large integral panel components holds promise for lightweight construction, but stress and warpage remain intractable problems. This work take stress in central lines as a research focus, theoretically analyzes stress evolution along central lines without a stress distribution hypothesis, then further develops prediction models of warpage, based on general beam theory. The stress and warpage models are then verified by experimental results. The results showed that below 40 layers, the stress in the top layer increased rapidly to the yield strength. Following the continuous deposition of up to 100 layers, stress increased slowly, then gradually trended to a constant level. After 100 layers of deposition, the top-layer-plane stress in the 10th layer decreased from 68 MPa to 5 MPa, and the plane stress in the 90th layer decreased from 296 MPa to 245 MPa. Post-heating treatment effect was important for temperature uniformity. The largest warpage (3.48 mm) happened when stiffener was designed as 30 layers.
Highlights
Wire and arc additive manufacture (WAAM) is a near-net forming technology, based on the discretization-deposition methodology, which uses an electric arc as a heat source and deposits 3D metal parts in a layer-upon-layer manner
During the WAAM deposition process, the main residual stress across the top layer usually results from solidification shrinkage—the limit value of which is the yield strength
In the single-wall part, the nonuniform distribution of the residual stress from the bottom to the top layer is the precipitating factor of warpage—the effect of which is similar to the bending moment
Summary
Wire and arc additive manufacture (WAAM) is a near-net forming technology, based on the discretization-deposition methodology, which uses an electric arc as a heat source and deposits 3D metal parts in a layer-upon-layer manner. Chen [5] highlighted WAAM application in fabrication of integral panel for the technical feature, deposits stiffeners layer up layer on to base plate. This method significantly improves material utilization and efficiency. Considering the stress distribution and the distribution feature of residual thermal stress, a curved laminated deposition path is usually advised to build space structures, so as to change the in-plane stress into 3D-stress distribution—and help to relieve stress during the continue deposition process This is just as in the case of a flexible structure because of its lower stiffness, but the elastic coefficient is gradually increased with the layer up layer deposition and equal to the elastic module of bulk material. The space flexible structure was designed according to the stress profile
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