Residual stresses are a concern in weld beads since they increase the susceptibility to cracks and fatigue failure. Conventional methods to reduce these stresses are based on post-processing or the application of additional tools in the process, which increases the processing cost and time. In this context, this study aimed to measure the effect on residual stresses in welds of modulating the laser power emission applying two different wave shapes. The modulation method allows the energy delivery of the beam to be controlled by adding power steps, which changes the heat absorption and distribution by the molten pool. Square and step-shaped power modulation waves were used, through a YLS 10,000 fiber laser source (IPG Photonics) with a maximum power of 10 kW, in the welding of SAE 4140 steel of high hardenability. To measure residual stress fields in a specific critical point near the weld bead, the measuring technique combines the hole drilling method and speckle interferometry (instead of traditional strain gauges) for the identification of the displacements around the hole. The results showed that a reduction in the stress magnitudes was obtained for the step-shaped modulation wave, in the order of 77 MPa, which represents a reduction of 16% in comparison with the continuous wave with an increase of 37% in penetration depth, which is appreciable for applications in thicker plates.

残余应力是焊缝中需要考虑的问题，因为它们会增加对裂纹和疲劳破坏的敏感性。减轻这些压力的常规方法是基于后处理或过程中附加工具的应用，这会增加处理成本和时间。在这种情况下，本研究旨在测量采用两种不同波形调制激光功率发射对焊缝中残余应力的影响。调制方法允许通过增加功率步长来控制束的能量传递，这会改变熔池的热量吸收和分布。在具有高淬透性的SAE 4140钢的焊接中，通过最大功率为10 kW的YLS 10,000光纤激光源（IPG Photonics）使用了方形和阶梯形的功率调制波。为了测量焊缝附近特定临界点的残余应力场，该测量技术结合了钻孔方法和斑点干涉法（代替传统的应变仪）来识别孔周围的位移。结果表明，阶梯形调制波的应力幅度有所降低，约为77 MPa，与连续波相比，穿透深度增加了37％，与连续波相比降低了16％，这对于在较厚的板中的应用来说是很有意义的。