Suppression Control of Transversal Oscillation on High‐Cycle Fatigue Properties of Thin Spot‐Welded Steel Sheets

Resistance spot welding (RSW) is a critical joining technique in automotive manufacturing, where the fatigue performance of spot‐welded joints significantly influences the durability and structural integrity of vehicle bodies. The novelty of this study lies in systematically identifying and quantitatively controlling two major experimental disturbances, namely weld nugget interstice and transversal oscillation, which have long been overlooked in conventional fatigue tests of thin spot‐welded steel sheets. JSC270 and HC220BD were used to fabricate lap‐shear specimens. An antibuckling fixture was developed to suppress lateral oscillation, and gap‐filling methods using rubber bands and shaped copper strips were adopted. Fatigue experiments were conducted under strictly controlled and consistent conditions to ensure that performance improvements were attributed mainly to the proposed interventions rather than uncontrolled variables. Results indicate that both gap‐filling and antibuckling constraints significantly enhance fatigue life and reduce data scatter. Copper strip filling reduced the relative standard deviation of fatigue life to 11.6%, while antibuckling constraints increased average fatigue life by 82.3%. The proposed methods provide practical and low‐cost strategies to improve the accuracy and reliability of fatigue life evaluation, which is of great importance for standardizing fatigue tests and enhancing the durability of spot‐welded structures in automotive applications.