Materials Science Forum Vols. 505-507

Abstract: Due to the rapid progress of industrial development, the formation of lightweight and small-size parts is becoming increasingly important. Especially in the IC and 3C industry, the sheet metal forming of miniature parts is especially interesting. Size effects such as specimen dimension, blank thickness, punch corner dimension, grain size, and grid dimension (for strain measurement), as well as the microstructure of material and surface condition all seriously influence the forming of miniature parts. In this paper, systematic experiments including Erichsen stretch forming and hydraulic bulge, and strain analyzers including for circular and rectangular grids are described for establishing the relationships of sheet metal formability to process parameters. The details of the experimental procedures and results are presented and discussed.

Abstract: The process of precision gear forging has been developed recently because of its advantages of giving high production rates, improved strength and surface finish. For complete filling up, predicting the power requirement is an important feature of the forging process. To analyze the process of incremental forging of hollow spur gear forms from initially ring-type specimens, a series of simulations using the program DEFORM-3D was carried out. The results of current simulation were compared with the experimental data those obtained by forging of hollow spur gear forms. In addition, the influences of the process parameters such as module, number of teeth, the ratio of the inner radius to the outer radius, friction factor and the height of the billet on the forging force is also examined.

Abstract: Currently, tube hydroforming and metal micro-forming technique have emerged as the attractive and important developing tendencies in industry. Hence, in this study, the finite element simulation technique was employed to investigate the micro-hydroforming for making the micro-square tube with non-equal section and dendritic shape from square tube. Results of the current study show that the deformation of micro-square tube can be effectively analyzed by finite element simulation. The bulging and wall thinning of the tube are severely influenced not only by the internal hydraulic pressure but also by the punch axial feeding speed.

Abstract: In this study, the predictive model of friction coefficient using cylindrical compression was constructed through combining the finite element method and neutral networks. Namely, the related data of the materials characters, cylinder compression bulging, and how they were associated with friction coefficient was obtained by the finite element method. Based on those analysis data, the relationship model, reflecting the relationship among the materials characters such as strength coefficient and strain-hardening exponent, the compression bulging such as reduction height, expanding in upper ending, expanding in bottom ending, maximum expanding in outside diameter and the friction coefficient in workpiece/die interface, was constructed. Finally, the cross verification between finite element analysis, prediction by neutral network model and the experiments of cylindrical compression testing and ring compression testing are repeatedly checked to ensure the accuracy and reliability of the constructed model. Results of the current study indicate that their errors are extremely limited, and the developed predictive system is reliable and feasible.

Abstract: In this study, deep drawing using plastic die was investigated to prevent seizure during forming. In the deep drawing process of aluminum and titanium sheets, seizure was found to occur during forming due to a high reactivity with other metals. For the prevention of seizure, plastic dies were used in this study. These plastic materials have a good resistant to seizing, since no seizure occurs in the contact surface of the metal and plastic material. Moreover, the effects of seizure and wearing die on the dimensional accuracy of drawn cups were examined using nylon die. The blanks used were pure aluminum, aluminum alloy A5052 and pure titanium. The blanks could be successfully formed with a water lubricant. To increase the dimensional accuracy of the drawn cups, deep drawing using fiber-glass-reinforced nylon and plastic composite steel die was also attempted. It was found that the use of plastic die was very effective in preventing of seizure.

Abstract: Both the minimum relative depth of die cavity and the minimum amount required in preforming are determined to produce a defect-free product of tubular component in the preforming technique of radial extrusion in this study. This scheme is based on the least amount of material dissipation in radial extrusion of tubular component. A finite element based code is utilized to investigate the effects of various relative depths of die cavity, different percentage of preforming and relative height reduction on the material flow characteristics resulting in the movements of the defects locations. The abductive network is also applied to synthesize the data sets obtained from the numerical simulations. Consequently, a prediction model is established for organizing the minimum relative depth of die cavity and the related minimum amount required in preforming of the tubular component for different end strokes of deformation.

Abstract: In this study, we’ve used carburized-quenched-tempered steels that received shot-peening process with different shot grain sizes and evaluated variation of surface property of the steels. As a result of study, it is demonstrated that the fatigue life of carburized steels can be prolonged significantly by increasing surface hardness and compressive residual stress and by reducing surface roughness and abnormal carburized case depth at superficial layer, which we’ve investigated in the study.