J31315曲柄压力机设计毕业论文.doc

Numerical design of a new forging press drive incorporating non-circular gears Abstract: Manufacturing processes as well as products have to be improved continually to meet all the requirements of international competition. Along with economic demands，changing consumer and environmental legislation lead to increased pressure for new and advanced products and processes. Consequently，the forging industry continually tries to improve hot forging processes. Precision hot forging technology，used for the production of connecting rods，bevel gears，straight planet gears，helical gears clutch gearing or constant velocity joints，has been improved constantly [1-3]. Precision forging is carried out with closed dies in order to guarantee the continuous quality of the workpiece and to avoid possible damage to the forged parts by clipping or piercing operations. Many variables influence the quality of the final product and the economics of the Process，especially the workpiece temperature，the die temperature and the pressure dwell time. High workpiece temperatures lead to high temperatures on the surface of the dies. Therefore，the temperature load depends directly on the pressure dwell time. Excessive temperature loads inevitably lead to damage of the dies [4]. This article presents a numerical study of a new press concept using non-circular gears in the drive mechanism. The new press kinematics result in a reduced pressure dwell time in comparison with a conventional press kinematics. Keywords: metal forming; finite element simulation; thermal die loading; drive mechanism; non-circular gears . NOTATION : a center distance a,b coefficients of Fourier series A surface area of the die C quality of the transmission function regarding kinematic demands e distance between the center and the pivot of an eccentrically mounted circular transition ratio as a function of the driving angle n number of the cycle flux Q quantity of heat pitch curve radius of the driving fear as a