CAJ | 학술논문

超塑自由胀形的真实轮廓为轴对称旋转曲面，球面假设条件下的力学解析不能真实反映实际胀形过程。基于超塑自由胀形轮廓型面为椭球曲面这一试验基础，从连续介质塑性力学的基本理论出发，结合几何方程、力学平衡方程及Hill各向异性材料的增量理论，对超塑自由胀形过程进行力学解析，提出超塑自由胀形对壁厚均匀性的自我调节作用。给出超塑自由胀形过程中不同位置的经向应力及环向应力，并进一步得出应力场、应变速率场及应变场分布。由广义速率敏感性指数的定义式，给出 m 值的解析式，并得到超塑自由胀形的最佳加载路径。超塑自由胀形椭球曲面假设得到试验验证，椭圆函数拟合度高达0.996以上。
초소자유창형적진실륜곽위축대칭선전곡면，구면가설조건하적역학해석불능진실반영실제창형과정。기우초소자유창형륜곽형면위타구곡면저일시험기출，종련속개질소성역학적기본이론출발，결합궤하방정、역학평형방정급Hill각향이성재료적증량이론，대초소자유창형과정진행역학해석，제출초소자유창형대벽후균균성적자아조절작용。급출초소자유창형과정중불동위치적경향응력급배향응력，병진일보득출응력장、응변속솔장급응변장분포。유엄의속솔민감성지수적정의식，급출 m 치적해석식，병득도초소자유창형적최가가재로경。초소자유창형타구곡면가설득도시험험증，타원함수의합도고체0.996이상。
The real profile of superplastic free bulging is axisymmetric rotating surface, and therefore the theory of spherical assumption can not reflect the actual superplastic free bulging process. Experimental results show that the shape of superplastic free bulging is ellipsoidal surface. Starting from the fundamental theory of plastic mechanics for continuous media, combined with the geometric equation, mechanical equilibrium equation and the anisotropic incremental theory of Hill, the mechanics analysis for superplastic free bulging process based on the assumption of ellipsoidal surface is accomplished. The self regulation on thickness uniformity is presented. The radial and tangential stress at different positions for free bulging is given, and then the spatial distribution of the stress, strain and strain rate fields is established. The analytical formula of the m value is given by utilizing its definition, and the optimal loading path of the superplastic free bulging is got. Ellipsoidal surface hypothesis is verified by experiment, and elliptic function fits up to more than 0.996.