Fundamentals & Limiting Draw Ratio
深拉深基本原理与极限拉深比
标签：极限拉深比, 塑性流动, 杯形件, 材料方向性
深拉深成败取决于极限拉深比（LDR，β=D₀/d₁），即首次拉深中坯料直径与凸模直径的最大允许比值，一般黄铜约 2.0、紫铜约 1.9。超过此值侧壁会失稳起皱或底部圆角拉裂。材料厚向异性指数 r 越高、硬化指数 n 越大，越利于均匀流动、抑制局部变薄。
Success in deep drawing depends on the limiting draw ratio (LDR, β=D₀/d₁), the maximum allowable ratio of blank diameter to punch diameter in the first draw—roughly 2.0 for brass and 1.9 for copper. Exceeding it causes wall wrinkling or fracture at the bottom radius. Higher normal anisotropy r and strain-hardening exponent n improve uniform flow and reduce local thinning. ---