【作者】 芮嘉白；

【导师】 徐秉业； 金观昌；

【作者基本信息】 清华大学 ， 固体力学， 1994， 博士

【摘要】 本文从轴对称空间问题的基本方程出发,研究了理想弹塑性材料塑性加载时的一般解法,讨论了采用各种形式Tresca屈服条件的可能性及轴向应力对于它的影响,并导出了塑性应变的解析式。本文又根据机械自紧本身和火炮身管材料循环加载的特点,采用与现有文献不同的途径和塑性轴对称问题的一般解法,推导了满足所有弹塑性基本方程并符合机械自紧实际情况的加载、卸载及残余量的简明解析式,导出了冲头和身管接触面压力分布、塑性区的大小和形状、产生反向屈服和全塑性时内膛加载位移△的临界值和反向屈服区等参量,提出了合理的反向屈服加载函数。使用本文所提出的方法只需要过盈量δ、几何尺寸和材料性能参数即可直接求得机械自紧所需各项参数。文中还分析了包兴格效应、反向屈服及其强化系数对残余应力的影响。计算结果与现有文献的实验结果符合得较好,证明了本文理论的正确性与可靠性。 本文改进和完善了用于测量位移和变形的数字散斑相关技术,提出了一种新的数字散斑相关搜索位移的方法——十字搜索法,讨论了提高测量精度的技术条件,采用这种方法可以提高处理速度及测试精度。本文的实验测试工作使用透明的光塑性材料聚碳酸酯模拟炮筒、数字散斑相关法测量机械自紧身管内部加载区的弹塑性变形,成功地模拟了机械自紧身管的加载过程,使其变形机理更为直观。用本文理论计算的变形规律与模拟实验结果一致。更多还原

【Abstract】 In the present thesis, the solution of axisymmetrical space full plastic problems of ideal elastoplastic material is proposed from the fundamental equations, the possibility of using Tresca’s yielding condition and the influence of longitudinal stress are discussed therefore the analytic formulae of plastic strain are also derived. Depending on the characteristics of mechanical autofrettage, the cyclical loading feature of the gun tube material and the solution of axisymmetrical space full plastic problem, the simple analytic formulae of mechanical autofrettage about loading, unloading and residual parameteres that satisfy all the elastoplastic equations and the realistic situations are derived by a new way that different from the previous papers completely. On the other hand the pressure distribution between mandrel and tube, the shape and the size of the plastic zone, the critical value of the loading displacement A in cavity when reyielding or full plasticity is taking place, and the reyielding zone etc. are given. The reasonable reyielding loading function is proposed. All the parameteres of the mechanical autofrettage can be obtained directly by the excess δ, the geometric size and the material constants using this method. The influences of Bauschinger’s effection and reyielding with it’s hardening coefficient to residual stresses are analyzed. The experimental result of the previous papers agree well with the presented theoretical analysis, it prove the reliability of the theory in the present paper.The Digital Speckle Correlation Method (DSCM)for measuring the displacement and deformation is improved in this paper and a new searchingmethod-----cross searching method is proposed. The technique conditionsfor enhancing the measuring accuracy that made DSCM more practical are discussed. The transparent photoplastic material polycarbonate is chosen to simulate gun tube and DSCM is adopted for guaging the deformation inloading area of the tube. The loading procedure of the tube is successfully simulated by the experimental testing and it makes the mechanism of the deformation in mechanical autofrettage more intuitive. The regularity of deformation calculated by the present theory agree well with the result of simulated experiment.更多还原