Failure analysis of a loader hydraulic cylinder and its end cap structure improvement

With the rapid development in the manufacturing sector, lightweight manufacturing has become an inevitable trend. However, achieving lightweight engineering machinery requires the structural redesign of most internal components, including the hydraulic cylinders in hydraulic systems. When evaluating the lifespan of redesigned loader hydraulic cylinders using simulated pulse experiments, it was evident that the fillet weld between the connecting end cap and cylinder barrel failed and fractured before reaching its full lifespan. Consequently, in order to assess the failure conditions of the loader hydraulic cylinder, the generation and extension of the failure cracks were explored using methods such as macroscopic fracturing, hardness testing, metallographic analysis, inclusion component analysis, and finite element analysis. During this process, the end cap structure of hydraulic cylinder was improved using finite element analysis. The results showed that the presence of numerous coarse spherical carbides at the tip of the weld cracks and the formation of dislocation tangles around the carbides, resulting in high stress concentrations and accelerated fatigue crack propagation. Additionally, the specific welding-joint structure of the hydraulic cylinder, resulting in high stress concentrations and accelerated fatigue crack initiation at the weld. After improving the hydraulic-cylinder end cap structure using finite element analysis, the fatigue life of the hydraulic cylinder was improved. This work provides a theoretical basis for the design and manufacture of lightweight and high-life hydraulic cylinders.