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中文摘要：
内高压成形过程中，管材的轴向失稳大多发生在塑性阶段，对应的起皱临界载荷是管材进入塑性阶段时的屈服载荷与塑性起皱载荷之和。对于塑性起皱，采用线性硬化材料模型，将本构方程的起算点设置在理想线性强化的起始位置即屈服点，使本构方程有线性形式，建立管材内高压成形起皱临界应力解析表达式。以此为基础讨论力学性能及应力比等对管材内高压成形塑性起皱的影响。结果表明：弹性模量和屈服强度是影响管材抵抗轴向起皱能力的主要力学参数，两者变化参量A决定了管材轴向抗皱能力的变化。当2〉0时，起皱临界应力绝对值随之增大；当2〈0时，起皱临界应力绝对值随之减小。应力比对起皱临界应力影响存在两种情况：当最小起皱临界应力对应的起皱失稳发生在颈缩失稳之前，起皱临界应力绝对值随应力比绝对值的增大先减小后增大；当最小起皱临界应力对应的起皱失稳发生于临界颈缩失稳之时，起皱临界应力绝对值随应力比绝对值的增大单调增加。
英文摘要：
Wrinkling behavior of tube in hydroforming mostly occurs in plastic state. The corresponding critical load for wrinkling is the sum of the initial yield load and the plastic wrinkling load. For plastic wrinkling, constitutive equation is in linear form when it is computed from the initial yield point using linear-hardening model. Formulation to calculate the critical stress for wrinkling during tube hydroforming process is given first. And the effects of main mechanical properties, tube dimensions and axial-circumferential stress ratio on wrinkling behavior are analyzed. The results show that： the modulus of elasticity and yield strength are the main mechanical parameters affecting the resistance to axial wrinkling, and the variables λ of the both determine the changing of resistance to axial wrinkling. When λ is greater than zero, the absolute value of critical stress for wrinkling will increase. However, when λ is less than zero, the absolute value of critical stress for wrinkling will decrease. The effect of stress ratio on wrinkling depends on the time of the smallest critical stress＇s arising for wrinkling. When the wrinkling corresponding to the smallest critical stress arises before necking, the absolute value of critical stress for wrinkling will decrease first and then increase as the absolute value of stress ratio increases. When it arises at necking, the absolute value of critical stress for wrinkling will increase as the absolute value of stress ratio increases.
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