tailieunhanh - Metal Machining - Theory and Applications Episode 2 Part 2

Tham khảo tài liệu 'metal machining - theory and applications episode 2 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The Iterative Convergence Method ICM 213 Fig. Developed flow-chart of the iterative convergence method Judgement of saturation of the plastic flow is made either on the basis of the tool load reaching a maximum value or of conservation of volume - . that the computed flow of material out of the plastic zone into the chip balances that of the work into the plastic zone. Reformation of the flow field supposes that the separation between nodes along a streamline is unchanged by reformation but that the direction from one node to the next is altered to bring it more closely tangential to the calculated flow. For each flow line consisting of a node sequence j - 1 j j 1 . the updated x y coordinates of node j are given by Xj Xj-1 Ux j-1 ứx j ---- --------- Lj yj yj-1 Uy j-1 uy j ----1------- -- Lj 214 Finite element methods where uxj uy j are the calculated velocities at node j j is the resultant average velocity of nodes j-1 and j and Lj is the separation between nodes j-1 and j tj x j-1 uj uy j-1 Uy f h Lj xj-1- xj 2 yj-1- y 1 2 The reformation using equations and is implemented from the beginning to the end of a flow line so that the coordinates xj-1 yj--1 have already been revised. The equivalent plastic strain e in each element is evaluated by the integration of its rate e along the reformed flow lines e Jedi J -d ve where ve the element velocity obtained from the average of an element s nodal velocities. Relations between flow stress strain strain rate and temperature are considered in Section . Figure shows an ICM mesh for two-dimensional machining with a single point tool in which the x- and y-axes are taken respectively parallel and perpendicular to the cutting direction in a rectangular Cartesian coordinate system. The tool is assumed to be stationary and rigid while the workpiece moves towards it at the specified cutting speed. Fig. Two-dimensional finite element assemblage with boundary conditions The .