【作者】 张丽娜；

【导师】 计欣华；

【作者基本信息】 天津大学 ， 固体力学， 2008， 博士

【摘要】 光弹性法是解决工程中二维和三维应力问题的有效实验方法,它能够直接测量三维模型内部任意一点的应力信息。随着计算机技术的发展,光弹性法测量三维应力模型的自动化技术成为新的研究热点。本文在结合前人工作的基础上,针对三维数字光弹性法中的几个待解决的问题进行系统的研究,实现从图像采集到应力分离的完全自动化。本文以相移法为实现数字光弹性法的基础,针对Patterson和Wang的光弹性六步相移法中等倾线信息受到整数和半数级等差线的影响,提出了八步相移法。该方法从理论上解决了等倾线(范围在[ 0,π2])信息受等差线干扰的问题,得到全场等倾线参数。在光弹性八步相移法的基础上,提出了确定模型切片的第一主应力方向的三种方法。根据求解反正切运算的两种规则,分析并获得反映第一主应力方向的等倾角信息。通过对径受压圆盘和圆环验证了该方法的可行性。分析了时效对三维光弹性模型的影响,在时效存在的前提下,假设了时效影响的力学模型,通过模拟和实验证明了此假设。介绍了在实验中消除时效影响的两种方法。在三维冻结应力模型切片的应力信息自动获取后,本文讨论了应力分离实现自动化的问题。用三维数字光弹性法分析汽轮机叶根、轮缘的三维接触应力。得到了该模型六个应力分量的全场数值,并讨论了叶根和轮缘的可能接触区域、该三维模型的Mises等效应力和轮缘各齿承担的载荷。这说明三维数字光弹法可以应用到工程测试中,为扩展数字光弹性法发展的空间奠定了基础。更多还原

【Abstract】 Photoelascity is an effective method to solve two-dimensional and three-dimensional stress analysis in engineering and a focus today. Stress components at any point of the three-dimensional model can be calculated by it.With the development of computer technique, automatic whole-field measurement of photoelasticity has been focused. Based on the work which was reported before, some urgent problems of digital photoelasticity have been discussed,and automatic data processing and stress separation of photoelasticity are realized. The problem of isoclinic and isochromatic interaction is important in phase-shifting techniques in photoelasticity. A technique named eight-step phase shifting technique is presented to solve the problem of isoclinic fringe pattern influenced by isochromatic fringe patterns of integer order and half-integer order. Isoclinic parameter in the range of [ 0,π2] of the frozen slice is given by the method.Based on the eight-step phase shifting technique, three methods to determining the first principal stress direction of the slice are discussed. Isoclinic angle information of whole-field first principal-stress direction can be analyzed and obtained by two rules of arctan calculation. The feasibility of this method was proved by the experiments of disk and ring under radial compression.The influence of time edge effect is analyzed. On the premise of exiting time edge effect, mechanic model is founded and proved by simulation and experiment. Two methods for erasing time edge effect are put forward in the experiments.Automatic technique of stress separation is discussed after obtaining the value and direction of secondary principal stress of every frozen slice.Three-dimensional contact stress of turbine between roots and rims are analyzed by the three-dimensional digital photoelasticity. Six stress components and equivalent Von Mises stress of any point in the model are calculated and the contact area of roots and rims are discussed. Finally, the loading values of every tooth of rims are obtained. Three-dimensional digital photoelasticity can be used widely in engineering field and the field of application is widened.更多还原