A new method for manufacturing hollow valves via cross wedge rolling and forging: Numerical analysis and experiment validation

Cross wedge rolling-forging (CWR-forging) is an innovative process for local plastic deformation that is suitable for forming hollow valves. This paper presents the numerical and experimental results of hollow valve production using this new method. The most popular production methods are described. Then, this study examines the formation of such valves through CWR-forging. A numerical model of CWR-forging using the finite element method (FEM) is developed to estimate the technological viability of this process. The distributions of effective strain, temperature, metal flow, force, and torque are analyzed as well. In this study, changing the stretching angle (β) can effectively avoid swollen holes. therefore, the forming quality of the workpiece can be greatly improved when the forming angle (α) is equal to 35° and the stretching angle (β) is equal to 5° and 4° in the knifing and stretching zones and the mandrel diameter is 4 mm, respectively. Numerical results are then verified under laboratory conditions. Experimental results are consistent with the FEM results, thus confirming that hollow valves can be produced through CWR-forging.