Low-stress-splitting process for connecting rods with prefabricated notches

This paper presents a novel low-stress splitting process for connecting rods. Furthermore, a theoretical formula for calculating the critical load of the splitting process is derived. For a 500 mm cantilever, the maximum critical load required for the JD52 connecting rod is only 0.257 times that required for conventional fracture splitting. The analytical and experimental results reveal that crack evolution during this process is divided into three distinct stages: crack initiation, crack propagation, and instantaneous fracture. The material failure progresses through four successive stages:shear stress-dominated ductile failure, mixed shear-tensile stress-dominated ductile failure, tensile stress-dominated ductile–brittle failure, and tensile stress-dominated brittle failure. The cross-sectional horizontal error and maximum unevenness are ≤ 3 mm , both of which satisfy industrial production requirements. Additionally, a loading strategy is proposed to reduce the force required during the instantaneous fracture stage. This optimized control strategy, informed by the crack evolution characteristics, reduces the cross-sectional horizontal error to 0.27 mm and maximum unevenness to 736.5 μ m , while increasing the total processing time by less than 1%. This demonstrates the effectiveness of the proposed strategy in significantly improving connecting rod quality with minimal impact on processing efficiency.