Purpose

During the powder bed fusion process, thermal distortion is one big problem owing to the thermal stress caused by the high cooling rate and temperature gradient. For the purpose of avoiding distortion caused by internal residual stresses, support structures are used in most selective laser melting (SLM) process especially for cantilever beams because they can assist the heat dissipation. Support structures can also help to hold the work piece in its place and reduce volume of the printing materials. The mitigation of high thermal gradients during the manufacturing process helps to reduce thermal distortion and thus alleviate cracking, curling, delamination and shrinkage. Therefore, this paper aims to study the displacement and residual stress evolution of SLMed parts.

Design/methodology/approach

The objective of this study was to examine and compare the distortion and residual stress properties of two cantilever structures, using both numerical and experimental methods. The part-scale finite element analysis modeling technique was applied to numerically analyze the overhang distortions, using the layer-by-layer model for predicting a part scale model. The validation experiments of these two samples were built in a SLM platform. Then average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model.

Findings

The validation experiments results of average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. It was found that they matched well with each other. From displacement and residual stress standpoint, by introducing two different support structure, two samples with the same cantilever beam can be successfully printed. In terms of reducing wasted support materials, print time and high surface quality, sample with less support will need less post-processing and waste energy.

Originality/value

Numerical modeling in this work can be a very useful tool to parametrically study the feasibility of support structures of SLM parts in terms of residual stresses and deformations. It has the capability for fast prediction in the SLMed parts.

中文翻译：

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选择性激光熔化工艺制造悬臂结构的变形和应力预测

目的

在粉末床熔融过程中，由于高冷却速率和温度梯度导致的热应力，热变形是一个大问题。为了避免内部残余应力引起的变形，在大多数选择性激光熔化（SLM）工艺中使用了支撑结构，尤其是对于悬臂梁，因为它们可以帮助散热。支撑结构还可以帮助将工件固定在其位置上，并减少打印材料的体积。在制造过程中减轻高的热梯度有助于减少热变形，从而减轻开裂，卷曲，分层和收缩。因此，本文旨在研究SLM零件的位移和残余应力的演变。

设计/方法/方法

这项研究的目的是使用数值和实验方法来检查和比较两个悬臂结构的变形和残余应力特性。应用零件比例有限元分析建模技术，使用逐层模型预测零件比例模型，对悬垂变形进行数值分析。这两个样本的验证实验是在SLM平台中构建的。然后测试四个尖端角的平均位移和悬臂梁顶表面的残余应力以验证模型。

发现

测试了四个尖端角的平均位移和悬臂梁顶表面上的残余应力的验证实验结果，以验证该模型。发现它们彼此匹配良好。从位移和残余应力的角度来看，通过引入两种不同的支撑结构，可以成功地打印出具有相同悬臂梁的两个样品。在减少浪费的支撑材料，减少打印时间和提高表面质量方面，具有较少支撑的样品将需要较少的后处理和浪费的能源。

创意/价值

这项工作中的数值建模可能是一个非常有用的工具，可以根据残余应力和变形参数化地研究SLM零件支撑结构的可行性。它具有在SLMed零件中进行快速预测的功能。