Search

In this paper, non-isothermal analysis of an automatic multi-stage cold forging process of a ball-stud is conducted using a new material model which is a closed form function of strain, temperature and strain rate covering low and warm temperatures for high-strength stainless steel SUS304. An assembled die structural analysis scheme is employed for revealing the detailed die stresses, which is of great importance for process and die design for metal forming of the materials with high strengths. Die elastic deformation is dealt with to predict final geometries of material with higher accuracy. A complete analysis model is proposed to be used for optimal design of process and die designs in automatic multi-stage cold forging of high-strength materials.

SUS304 stainless steel is characterized by combined tensile and compression testing, with an emphasis on flow stress at higher strain and temperature. The plastic deformation behavior of SUS304 from room temperature to 400 &deg, C is examined and a general approach is used to express flow stress as a closed-form function of strain, strain rate, and temperature, this is optimal when the strain is high, especially during automatic multi-stage cold forging. The fitted flow stress is subjected to elastothermoviscoplastic finite element analysis (FEA) of an automatic multi-stage cold forging process for an SUS304 ball-stud. The importance of the thermal effect during cold forging, in terms of high material strength and good strain-hardening, is revealed by comparing the forming load, die wear and die stress predictions of non-isothermal and isothermal FEAs. The experiments have shown that the predictions of isothermal FEA are not feasible because of the high predicted effective stress on the weakest part of the die.

In this paper, a study has been performed for optimal design and development of dynamic voltage compensation system using supercapacitor to solve voltage sag which are considered the dominant disturbances affecting power quality. Supercapacitor is employed to compensate dynamically for the voltage sag of system with sensitive load. With the prolific use of semiconductor devices in electrical equipment, modern-day loads are becoming increasingly sensitive to the sags and the disturbances prove to be costly to industries. As a technology -driven custom power installation, the dynamic voltage compensation system is recognized to be most effective equipment that can be used to counter the voltage sag problem. Hence, this paper proposes the high-performance optimal design of dynamic voltage compensation system which can efficiently compensate the instantaneous voltage sag and instantaneous interruption of the utility voltage source. This DVR system consists of a dynamic voltage converter in series with the supply voltage and high-efficiency controller of energy storage device using supercapacitor. Recently, in energy storage systems, the supercapacitor is paid attention as a new environmentally friendly energy storage element. This capacitor stores higher energy density than the conventional electrolytic capacitor. Also, this capacitor has a lot of advantages such as maintenance-free, longer life cycle and faster charge-discharge time than the conventional battery system. However, the supercapacitor for dynamic voltage compensation system must have each charge-discharge controller to control, a series-parallel switching circuit to use energy effectively with application of several compensation techniques for optimal operating. Therefore, in this paper, optimal development of on-line type dynamic voltage compensation systems is proposed.