With the increasing global competition, it is important for the automotive fasteners industries to reduce the cost and improve the production efficiency against other competitors. To achieve it, the author intends to introduce injection forging as an alternative method to conventional forming for automotive fastener production. This study investigates the characteristics of injection forging by finite element (FE) analysis and physical experiment. For the comparison of the conventional forming process with injection forging, ABAQUS and DEFORM were used to conduct FE simulations of the forming of a wheel bolt. Axisymmetric models were developed with both FE codes to analyse forging force, forging energy, forming form-error, tool stress, etc. of conventional multistep forging and injection forging (single step forging). A ring test was also conducted to determine the coefficient of friction between the workpiece and the tools in order to define the contact conditions in the FE models. Subsequently, tests on injection forging were carried out in Ritai Auto Standard Component Co. Ltd. The trials included forging force measurement, evaluation of lubricants, critical dimension measurement, macroetch testing micro-hardness tests and a manufacturing try-out. FE simulation results and experimental results were then compared. Behaviour of the lubricants was also examined for injection forging. Through the comparison, FE models were verified. Some improvements, regarding the influence of forging speed, thermal issues, meshing plan and the limitation of axis-symmetric model, were proposed. By using improved FE models, effects of critical aspects such as process parameters (forging speed and coefficient of friction), tool parameters (tool structure, tool geometry and tool materials), and workpiece parameters (workpiece material and workpiece geometry), were investigated in detail.With the improved FE models, influences of these parameters on fatigue life of the die, die wear, form-errors, and grain flow-lines, were examined. Based on the sensitivity analysis of forging parameters, optimisation was carried out on the tool parameters, and a new tool structure has been proposed for injection forging of the fastener. The tool design was assessed through FE simulations. As results of FE simulations and experiments, the main findings included the merits and drawbacks of injection forging compared with traditional forging process, the precision of FE models, the optimal lubricant for injection forging, the behaviour of injection forging in manufacture trials, the influence of process factors on tool life, forming accuracy and grain flow line. These findings supported the further tool optimization. After optimization, the tool life and forming accuracy had an increase. Based on the research work, the contributions were defined and recommendations of the further work were proposed.
|Date of Award||21 Mar 2017|
- University Of Strathclyde
|Supervisor||Yi Qin (Supervisor) & Amir Siddiq (Supervisor)|