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护环是发电机组中重要的零件,针对护环液压胀形技术理论分析的不足,利用塑性力学与变分原理研究了液压胀形过程中护环形状尺寸与力学性能的变化。预设护环液压胀形运动学容许的速度场、借助马尔柯夫变分原理确定真实速度场;由应变速率场求得应变增量场、以体积不变条件作为补充方程,建立了内径与高度的微分方程,求解得到护环液压胀形过程中径向尺寸与高度的解析关系,并运用于对护环液压胀形尺寸的预测。根据护环液压胀形质点的应变分量单调增加的特点,通过对等效应变增量积分计算质点的等效应变。将等效应变代入实验建立的等向强化理论中线性强化模型,得到了后续屈服应力与护环瞬时尺寸的解析关系,并用于护环初始毛坯尺寸的确定和液压胀形过程中的性能预测。1∶5的护环胀形实验结果与计算结果吻合较好。
The retaining ring is an important part of the generator set. According to the theoretical analysis of the retaining ring hydraulic bulging technology, the change of the shape and mechanical properties of the retaining ring during hydraulic bulging is studied by using the principles of plasticity and variational principle. The velocity field of the preset retaining ring hydraulic bulge kinematics is allowed, and the true velocity field is determined by the Markov variational principle. The strain increment field is obtained from the strain rate field, and the constant volume condition is taken as the supplementary equation. The differential equation of height is used to obtain the analytic relationship between the radial dimension and the height of the retaining ring during hydraulic bulging and to predict the hydraulic bulge size of the retaining ring. According to the monotonic increase of the strain component of the hydraulic bulge of the retaining ring, the equivalent strain of the particle is calculated by integrating the equivalent strain increment. The equivalent strain is substituted into the linear enhancement model established in the isotropy strengthening theory. The analytical relationship between the subsequent yield stress and the instantaneous dimension of the retaining ring is obtained and used to determine the initial blank size of the retaining ring and to predict the performance during hydroforming. The experimental results of 1: 5 retaining ring bulging agree well with the calculated results.