The single lap shear test is widely used to measure the strength of dissimilar welds even though such a test brings limited understanding of the intrinsic weld toughness. The present study proposes a numerical finite element (FE) analysis and experimental characterization of dissimilar joints presenting various microstructures (thickness of the intermetallic layer (IML) and hardness profile). For this purpose, Friction Melt Bonding (FMB) and Friction Stir Welding (FSW) were used to join aluminum AA6061 and Dual Phase steel (DP980). The FE simulations allowed calculating the evolution of the J-integral near this notch tip. It shows that crack initiation depends significantly on the plastic properties of the welded metallic alloys around the notch tip and the width of the welded zone, which both are significantly different for FSW and FMB processes. Nevertheless, a similar weld fracture toughness $J_C$ of approximately 1 kJ.m⁻² is estimated from the analysis for both FMB and FSW. This is three orders of magnitude higher than the fracture toughness of the intermetallic layer, revealing that the plastic dissipation in the Al and steel plates around the crack tip has a major effect on the weld toughness.

单搭接剪切试验被广泛用于测量异种焊缝的强度，尽管这种试验带来了对固有焊缝韧性的有限了解。本研究提出了一种数值有限元（FE）分析和不同特征的接头的实验表征，这些接头呈现出各种微观结构（金属间层的厚度（IML）和硬度分布）。为此，摩擦熔接（FMB）和搅拌摩擦焊（FSW）用于连接AA6061铝和双相钢（DP980）。有限元模拟可以计算J的演化-在该缺口尖端附近积分。结果表明，裂纹萌生在很大程度上取决于切口尖端周围的焊接金属合金的塑性和焊接区的宽度，这对于FSW和FMB工艺而言都明显不同。然而，类似的焊缝断裂韧性${Ĵ}_C$从FMB和FSW的分析估计大约1kJ.m ^-2。这比金属间层的断裂韧性高三个数量级，表明裂纹尖端周围的Al和钢板中的塑性耗散对焊接韧性有重要影响。