刀刃结构对镍合金切削过程影响的数值模拟

Numerical simulation of effects of cutting edge geometry on machining nickel-based alloy

利用DEFORM-2D有限元软件,使用多种钝圆刀具进行Inconel 718的正交切削模拟,刀刃与前刀面和后刀面的2个过渡点到理想刀尖的距离分别设为Sγ与Sα,通过Sγ和Sα描述刀刃结构,探究钝圆刀刃结构及进给量对切削力和摩擦因数的影响,对比理想刀具和钝圆刀具下的材料流动情况;通过DEFORM二次开发实现对材料微观结构变化的模拟,比较倒角刀具和钝圆刀具下已加工表面晶粒度和硬度的预测情况。研究结果表明:刀具钝圆尺寸对主切削力Fc和进给力Ff有不同程度的影响,存在使切削力比值μ(即Ff/Fc)为1的进给量临界点且受钝圆尺寸影响;Sγ和Sα对切屑力FQ和前刀面上的摩擦因数μQ几乎无影响;Sγ对材料滞留区范围的影响比Sα的大,对材料分离点的影响比Sα的小;倒角刀具和钝圆刀具模拟得到的晶粒度和硬度具有一定的辨识度。

The commercial finite element software DEFORM-2D was employed to conduct finite element modeling of orthogonal machining of Inconel 718 using multiple honed cutting tools. The cutting edge geometry was described by S_γ and S_α, in which S_γ represented the distance from the transition point between the cutting edge and rake face to the ideal tool tip, while S_α represented the distance from the transition point between the cutting edge and flank face to the ideal tool top. The influences of honed cutting edge geometry and feed on process forces and friction coefficient were investigated, whereas comparison of material flow under conditions of using ideal and honed tools was made. Simulation of microstructure evolution was implemented through the secondary development of DEFORM and predictions of grain size and hardness in machined surface involving chamfered and honed tools were compared. The results show that the hone size and feed have different effects on cutting force F_c and feed force F_f. There exists a critical point of feed affected by the hone size, in which the ratio of process forces μ i. e., F_f/F_c equals 1. Neither S_γ nor S_α shows any explicit influence on chip force F_Q and friction coefficient μ_Q on rake face. S_γ is found to influence material stagnation zone more than S_αwhile its influence on material separation point is less significant than that of S_α. Moreover, differences are identified according to the results obtained from modeling grain size and hardness with chamfered and honed tools used.