Abstract
Directed energy deposition (DED) provides a promising additive manufacturing method to fabricate and repair large metallic parts. However, it may suffer from excessive heat accumulation due to a high build rate, particularly during a wire feeding-type DED process. The implementation of interpass time in between two depositions of beads plays an important process role to passively control the interpass temperature. In this study, a method to estimate the proper interpass time using regression analysis from heat transfer finite element analysis is proposed for maintaining the interpass temperature during a wire feeding-type DED deposition of a planar layer. The overlapping beads of a planar layer are estimated using a polygonal-shaped bead profile in the finite element model. From the estimated proper interpass time, a selected proper interpass time scheme (PITS) is suggested for practical implementation. The selected PITS is applied in a thermo-mechanical finite element model to evaluate the temperature distribution and its effects on the depth of the melt pool, the depth of the heat-affected zone (HAZ), displacement, and residual stresses. By comparing the predicted results with those using a constant interpass time scheme (CITS), the selected PITS shows better control in reducing the depths of the melt pool and HAZ without severely inducing large displacement and residual stresses.
Highlights
Many industrial products use metals to form components or structures to meet their functional and aesthetic requirements
For the Directed energy deposition (DED) system used in this paper, the heat flux model has been calibrated according to the dimension of the heat-affected zone (HAZ) in [38]
Evolutions of the interpass temperatures, the depth of the melt pool, and the depth of the heat-affected zone with incremental bead depositions are discussed
Summary
Many industrial products use metals to form components or structures to meet their functional and aesthetic requirements. Directed energy deposition (DED) is a metal additive manufacturing technology that uses a high-intensity heat source to melt and fuse metallic feedstock to substrate as they are being fed It has shown promising applications for the production of large metallic components and the repair of the damaged region of an existing part [1,2,3]. Montevecchi et al [33] proposed an algorithm to computationally extract a suitable interpass time for multi-layer deposition using the wire-arc additive manufacturing process from heat transfer finite element analyses (FEAs). It is efficient, the implementation of the algorithm using Matlab into different FEA codes is difficult. Uncoupled thermo-mechanical FEAs are performed to further evaluate the influence of CITS and selected PITS on the displacement and thermal stress induced within the specimen
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