本研究旨在模擬選擇性雷射熔融法對不鏽鋼316L基板與粉末的單層多軌掃描過程，並探討軌道中特定截面的溫度與熱應力作用之分析。研究採用商用軟體ANSYS R18.0建立三維數值模型，並加入熱焓多孔法、間接耦合熱機械建模方法和有限元素法(FEM)模型，模擬分析熱和殘留應力的分布情況的變化。此外，考慮熔池內部馬蘭格尼效應，並改變不同的加工參數，如雷射功率、掃描速率、掃描間距及基板加熱等條件，分析各個條件下之溫度及應力分析。
研究結果顯示，在相同雷射能量功率下，馬蘭格尼效應持續將熔池表面的熱往內部深度方向傳遞，造成熔池最高溫度的下降趨勢，向下擠壓的力會推擠熔池向下和向外，但馬蘭格尼力會將熱往中間堆積，提高熔池的整體溫度，因此後續的討論皆會考慮馬蘭格尼力。隨著雷射功率的增加，SS316L之溫度及相對密度也逐漸增加，且隨著雷射功率越大，溫度及寬度深度也會逐漸增大。當掃描速率增加時，相對密度也會遞減，但遞減的速率比雷射功率低，掃描速率對SS316L的相對密度影響次之。當掃描間距增加時，相對密度也會增加但速度非常緩慢，且當間距增加過0.1mm時其相對密度會遞減，掃描間距對SS316L的相對密度影響最小。在增加不同雷射功率及掃描速率下， SS316L降伏強度和抗拉強度均會提高，但伸長率會降低。當基板逐漸加熱時，在保持較高的降伏強度時，延伸率也得到提升，表現出較好的結構。在高溫熱加熱基板後，應力應變曲線開始表現出脆性行為，材料之結構變形能力降低。改變掃描速率在不同雷射功率下，當掃描速度增加時，熱影響的尺寸減小。增加掃描線速率和減少雷射功率可以減少熱影響區的尺寸，從而降低熱應力，提高材料的結構穩定性和抗應力能力。

This study aims to simulate the single-layer, multi-track scanning process of selective laser melting on stainless steel 316L substrate and powder and investigate the analysis of temperature and thermal stress effects on specific cross-sections along the tracks. A three-dimensional numerical model is established, incorporating the enthalpy-porosity method, indirect coupled thermo-mechanical modeling approach, and FEM. Additionally, the Marangoni effect within the melt pool is considered, and different processing parameters are varied to analyze temperature and stress distributions under various conditions.
The research results demonstrate that the Marangoni effect continuously transfers heat from the surface of the melt pool toward the interior, leading to a decreasing trend in the maximum temperature of the melt pool. It also accumulates heat towards the center, thereby increasing the overall temperature of the melt pool. Therefore, the subsequent analysis considers the influence of the Marangoni force. With the increase in laser power, the temperature and relative density of stainless steel increase, and the width-depth dimensions also enlarge. When the scanning speed increases, the relative density decreases. When the hatching increases, the relative density initially increases and then decreases, with the least impact on the relative density. Under different laser powers and scanning speeds, both the yield strength and tensile strength increase, while the elongation rate decreases. As the substrate gradually heats up, the elongation rate improves while maintaining a higher yield strength, indicating better plasticity. After heating the substrate at high temperatures, the stress-strain curve starts to exhibit brittle behavior, resulting in a reduction in the material's plastic deformation capability. By modifying the scanning speed, a higher scanning speed leads to a smaller heat-affected zone. Increasing the scanning speed and reducing the laser power can decrease the size of the heat-affected zone, thereby improving the material's structural stability and stress resistance.

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