# Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM
## 1 Introduction  
Due to the complex processing technology of thin and hollow plate parts, negative production and material loss occur through traditional machining. However, technology, along with the development of additive manufacturing (AM), have become the preferred forming process plan for small quantities of complex parts [1; 2]. Selective laser melting (SLM) is a typical rapid forming technology [1; 3]. However, in practice, the metal powder is spread layer by layer followed by laser melting in SLM, which can produce a molten pool with a low-sized area and high temperature. Additionally, the temperature gradient is produced from high heat as well as being simultaneously transferred to the surrounding powder or printed body formation quickly [3; 4; 5], which makes the molten pool rapidly cool within microseconds. In addition, the molten pool shrinks, and thermal stress with the surrounding solid is produced under the interaction of condensation. When the stress is significantly high, macroscopic geometry deformation is produced, which is caused by the warping and cracking of the printed parts due to thermal stress. Therefore, a high number of printed parts failed to be produced, resulting in high amounts of material waste. Consequently, in this paper, the thermal field, thermal stress,and thermal deformation were researched, which were analyzed to develop the finite element method (FEM) analysis of welding. Many scholars have studied molten pool formation and the temperature field mechanism [6; 7; 8; 9; 10; 11]. [PERSON] et al. (2015) [6] reported that the temperature history could be measured with four thermocouples during experimentation, while the curves between experimental and numerical temperatures were compared. [PERSON] et al. (2016) [10] indicated that the ANSYS simulation agreed well with the experimental results, including temperature distribution, depth, width, and length of the melting pool. These were evaluated for each track by simultaneously considering the optical penetration depth of the laser at different scanning speeds. [PERSON] (2018) [11] researched thermal conduction to simulate the curing and solidification of the filament. In recent years, the research on thermal stress in hot-melt solidification has increased from experimental research [12; 13; 14] to extensive simulation [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. Since most predicted variables in the process are very difficult to measure experimentally, melting temperature field and thermal stress field simulations were developed based on the finite element method. [PERSON] et al. (2013) [17] developed 3D-FEM of ANSYS parametric design language (APDL) for the temperature and stress field analyses, predicting the melt pool size and value of von Mises stresses within five tracks for different scanning speeds (the model size was \(10\times 1\times 1\) mm). [PERSON] et al. (2016) [18] produced a 2D temperature profile and melt pool geometry of the In 625 (\(1\times 0.6\) (mm) for SLM. Additionally, the effects of the material properties and process parameters on the predicted temperature profile along the center of the laser beam path were simulated. [PERSON] et al. (2017) [24] built a 3D thermos-elastic-plastic model to analyze the melt pool size and horizontal/vertical normal stresses of the Ti6 Al4V product through direct metal laser sintering (DMLS), for which the simulation model size was \(1.5\times 1.5\times 2\) mm. [PERSON] et al. (2018) [26] investigated the modeling residual stress through ANSYS (APDL) of the four layers. The stress increased with the number of printed layers and the maximum stress occurred at the middle plane of the printed part (\(0.5\times 0.5\times 0.2\) mm). [PERSON] et al. (2018) [27] achieved enhanced volumetric heat source penetration to simulate the melt pool size and residual stress values during the SLM of a Ti6 Al4V part (\(30\times 30\times 10\) mm). [PERSON] et al.