دانلود رایگان مقاله همگن سازی خواص مواد در ساختار های افزودنی تولید

Abstract

Additive manufacturing transforms material into three-dimensional parts incrementally, layer by layer or path by path. Subject to the build direction and machine resolution, an additively manufactured part deviates from its design model in terms of both geometry and mechanical performance. In particular, the material inside the fabricated part often exhibits spatially varying material distribution (heterogeneity) and direction dependent behavior (anisotropy), indicating that the design model is no longer a suitable surrogate to consistently estimate the mechanical performance of the printed component. We propose a new two-stage approach to modeling and estimating effective elastic properties of parts fabricated by fused deposition modeling (FDM) process. First, we construct an implicit representation of an effective mesoscale geometry–material model of the printed structure that captures the details of the particular process and published material information. This representation of mesoscale geometry and material of the printed structure is then homogenized at macro scale through a solution of an integral equation formulated using Green’s function. We show that the integral equation can be converted into a system of linear equations that is symmetric and positive definite and can be solved efficiently using conjugate gradient method and Fourier transform. The computed homogenized properties are validated by both finite element method and experiment results. The proposed two-stage approach can be used to estimate other effective material properties in a variety of additive manufacturing processes, whenever a similar effective mesoscale geometry–material model can be constructed.

6. Conclusions

6.1. Summary and significance The main contribution of the paper is a new approach to predicting effective material properties of FDM printed structures. The approach is based on two novel ideas. First, given the manufacturing process plan and widely available material specifications, we formulated and constructed an implicit representation of an effective mesoscale geometry–material model of the printed structure that captures the heterogeneity and anisotropy resulting from the printing process. We then showed how this implicit representation of the mesoscale model may be queried and homogenized at macro scale in order to predict the effective material properties of the printed structure that accounts for build orientation,directional changes, infill patterns and other mesoscale details of 3D printing. We adopted and significantly improved the homogenization method using Green’s function, showing that the corresponding linear system is symmetric and positive definite, and can be efficiently solved by the conjugate gradient method with matrix–vector multiplication evaluated in the frequency domain. The predicted effective material properties are in good agreement with known experimental results and with the homogenization results predicted by the finite element method. The potent combination of implicit representations and queries handles the mesoscale complexity of FDM structures and is a further demonstration of the effectiveness of the query-based approach [45,6] that avoids multiple representations and conversions of geometry and material models.