【作者】 杨佳；

【导师】 李有堂；

【作者基本信息】 兰州理工大学 ， 机械制造及其自动化， 2021， 硕士

【摘要】 复合层板材料因其具有节约设备的生产成本、减少部分稀贵金属的使用并且可以满足实际生产中的特殊功能等优点,目前广泛地应用于航空航天、氯碱工业等生活中的大型工程项目中。钛-钢复合层板以其良好的综合性能广泛地应用于现代化学工业和高压容器行业中,金属钛相比于其他材料具有良好的抗腐蚀性能,而钢材在保证构件具有足够的强度下还可以降低构件的生产成本,二者构成的层板材料有效地发挥了两种材料各自的独特性能。为了提高钛-钢复合层板压力容器的疲劳强度以及有效地预测其裂纹扩展寿命,研究复合层板压力容器材料中裂纹的特性是很有意义的。主要的研究内容与成果有以下几个方面:(1)通过分析复合层板压力容器裂纹尖端应力场及位移场的分布情况,推导出了适用于求解复合层板压力容器中裂纹尖端应力强度因子的求解方法,确立了复合层板压力容器材料中的裂纹扩展判断准则,并分析了层板压力容器工作过程中的弹性力学问题,为实际工程应用提供理论依据。(2)建立了含裂纹的层板压力容器有限元模型,讨论了不同条件下层板压力容器的裂纹应力强度因子和J积分的变化规律。结果表明:裂纹应力强度因子K随着载荷比R、裂纹尺寸比a/δ的增大而增大。材料性能参数错配对裂纹应力强度因子产生促进或抑制作用。压力容器壁中心裂纹的起裂角度随着裂纹偏心距的变化而变化,并且裂纹两尖端的起裂角度不同。(3)通过分析裂纹扩展过程中裂纹尖端应力分布的变化,判断裂纹尖端驱动力的大小,进而分析裂纹的扩展路径。层板压力容器外表面和内表面的裂纹扩展路径和扩展速率不同,并且层板界面处是影响裂纹扩展路径的主要因素。容器表面裂纹相比于容器壁中心裂纹更容易发生应力集中现象,在裂纹扩展过程中更容易发生起裂。(4)对压力容器进行了系统的设计、建模、分析计算等工作,对其寿命进行了预估。在循环载荷作用下,压力容器过渡缘处出现最大应力,并且变形量也主要集中在侧表面过渡缘处。压力容器中的裂纹在扩展过程中,由于层板材料性能参数错配的影响,会一定程度抑制裂纹的扩展,从而延长了压力容器的使用寿命。更多还原

【Abstract】 Composite laminate materials have the advantages of saving equipment production costs,reducing the use of some rare and precious metals,and meeting special functions in actual production,and are currently widely used in large-scale engineering projects in life such as aerospace,chlor-alkali industry,etc.Titanium-steel composite laminates are generally used in the modern chemical industry and high-pressure vessel industry due to their good comprehensive performance.Compared with other materials,titanium metal has better corrosion resistance.The steel can also reduce the production cost of the component while ensuring that the component has sufficient strength.And the laminate material composed of the two materials effectively exerts the unique properties of theirs.In order to improve the fatigue strength of the titanium-steel composite laminate pressure vessel and effectively predict its crack propagation life,it is meaningful to study the characteristics of cracks in the composite laminate pressure vessel material.The main research content and results are as follows:(1)By analyzing the distribution of the crack tip stress field and displacement field of the composite laminate pressure vessel,a solution method suitable for solving the crack tip stress intensity factor in the composite laminate pressure vessel was derived.A criterion of crack propagation in composite laminate pressure vessel materials was established,and analyzed the elastic mechanics problems in the working process of the laminate pressure vessel,which provides a theoretical basis for practical engineering applications.(2)A finite element model of a laminated pressure vessel with cracks was established,and the variation law of the crack stress intensity factor and J integral of the laminate pressure vessel under different conditions was discussed.The results show that the crack stress intensity factor K increases with the increase of the load ratio R and the crack size ratio a/δ.The mismatch of material performance parameters will promote or inhibit the crack stress intensity factor.The initiation angle of the crack in the center of the pressure vessel wall varies with the eccentricity of the crack,and the initiation angles of the two crack tips are different.(3)By analyzing the changes in the stress distribution at the crack tip during the crack propagation process,the driving force of the crack tip is judged,and then the crack propagation path is analyzed.The crack propagation path and growth rate of the outer surface and the inner surface of the laminate pressure vessel are different,and the laminate interface is the main factor affecting the crack propagation path.The cracks on the surface of the container are more prone to stress concentration than the cracks in the center of the container wall,and cracks are more likely to occur during the crack propagation process.(4)The pressure vessel has been designed,modeled,analyzed and calculated systematically,and its service life has been estimated.Under the action of cyclic loading,the maximum stress appears at the transition edge of the pressure vessel,and the deformation is mainly concentrated at the transition edge of the side surface.In the process of crack propagation in the pressure vessel,the crack propagation will be inhibited to a certain extent due to the influence of the mismatch of the laminate material performance parameters,thereby prolonging the service life of the pressure vessel.更多还原