薄钢壳回转体轴向磁化状态分析

潜艇壳体、弹药壳体等薄钢壳回转体的半径和壁厚逐渐变化,且两端闭合,其轴向磁化状态的高精度建模非常困难.针对此问题提出了一种锥环单元计算公式,精确划分这些轴对称薄钢壳回转体的实际结构只需要少量的锥环单元,采用一维积分方程法实现了其轴向磁化状态的高精度快速建模.空心薄壁钢球壳磁特征的验证计算表明,所提出方法的计算值与解析值之间相对误差为1.2%.简易船模磁特征的验证计算表明,所提出方法的计算值与实测值非常吻合.并且上述计算过程分别只划分了100个锥环单元,便于工程实践中的应用.     

薄钢板船舶磁性的物理模型和数值模拟混合建模

针对现有薄钢壳船舶磁性参数获取方法存在的技术复杂、精度较低的问题,提出了一种将物理模型法和数值模拟法结合起来的混合建模方法.该方法将船体结构划分为若干种典型结构类型,并分别建造这些典型结构类型的磁性物理模型.测量典型结构磁性物理模型的外部磁场,通过拟合计算得到其等效磁性参数.对船体结构进行单元剖分,每个单元对应一种典型结构,利用所得到的等效磁性参数,实现整艘船舶的磁性建模.建模实例表明,该方法具有直观可信和精度高的优点,可以用于工程实践.     

Natural frequency characteristics of thin-walled homogeneous and manifold layered cylindrical shells underpressure using energy method简

Energy method for the vibration of two types of cylindrical shells,namely thin-walled homogeneous isotropic and manifold layered isotropic cylindrical shells under uniform external lateral pressure is presented.The study is carried out based on strain-displacement relationship from Love＇s shell theory with beam functions as axial modal function.A manifold layered cylindrical shell configuration is formed by three layers of isotropic material where the inner and outer layers are stainless steel and the middle layer is aluminum.The homogeneous cylindrical shell is made-up of isotropic one layer with stainless steel.The governing equations with uniform external lateral pressure for homogeneous isotropic and manifold layered isotropic cylindrical shells are obtained using energy functional by the Lagrangian function with Rayleigh-Ritz method.The boundary conditions that are presented at the end conditions of the cylindrical shell are simply supported-simply supported,clamped-clamped and free-free.The influences of uniform external lateral pressure and symmetrical boundary conditions on the natural frequency characteristics for both homogeneous and manifold layered isotropic cylindrical shells are examined.For all boundary conditions considered,the natural frequency of both cylindrical shells with symmetric uniform lateral pressure increases as h/R ratio increases and those considering natural frequency of the both cylindrical shells with symmetric uniform lateral pressure decrease as L/R ratio increases.     

Hard magnetization direction and its relation with magnetic permeability of highly grain-oriented electrical steel

The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling direction. The hard magnetization direction was found at an angle of 60° to the rolling direction. To compare the measured and fitting curves, when the magnetic field intensity is higher than 7000 A/m, it is appropriate to simulate the relation of magnetic permeability and magnetization angle using the conventional elliptical model. When the magnetic field intensity is less than 3000 A/m, parabolic fitting models should be used; but when the magnetic field intensity is between 3000 and 7000 A/m, hybrid models with high accuracy, as proposed in this paper, should be applied. Piecewise relation models of magnetic permeability and magnetization angle are significant for improving the accuracy of electromagnetic engineering calculations of electrical steel, and these new models could be applied in further industrial applications.     

轴向退磁线圈作用下潜艇壳体磁化状态分析

为了研究潜艇外部轴向退磁线圈对壳体的磁化作用,将现代潜艇的耐压壳体和非耐压壳体等效为双层薄钢壳回转体,采用一维积分方程法建立了潜艇壳体轴向非线性磁化数学模型。分析了潜艇壳体在轴向退磁线圈作用下的磁化状态,计算得到了潜艇内部和外部磁场值。计算结果表明:潜艇壳体对退磁线圈磁场具有约20%~30%的衰减作用,潜艇壳体内部磁场达到了铁磁材料矫顽力水平;潜艇外部近场(距离10 m)达到了铁磁材料矫顽力的约1/4,能对其他铁磁物体磁性产生明显影响;潜艇外部远场(距离50 m)已衰减得较弱,仅有地磁场水平的1/20左右,对其他铁磁物体磁性不再产生明显影响。     

多环交界裂纹面在谐振应力波作用下的动应力强度因子

研究埋藏圆柱体中多个环形交界裂纹面上受谐振应力波作用时的弹性波散射问题,以裂纹面的位错密度函数为未知量,利用Fourier积分变换,将问题归结为第二类奇异积分方程;然后通过数值求解奇异积分方程,获得裂纹尖端的动应力强度因子;给出了双裂纹动应力强度因子随入射波频率变化的关系曲线。     

钻孔法对焊接薄壁钢管纵向残余应力的测定

通过对钻孔法测定焊接钢构件残余应力的试验分析,我们测定了焊接薄壁钢管试件沿圆周的纵向残余应力的分布模式,得出该法测定纵向残余应力是可行的,其残余应力以拉应力为主。     

纵向磁场对低碳钢MIG焊焊缝组织及性能的影响

现代焊接结构对焊接质量的要求越来越高.焊缝金属的内部组织及其结构显著影响焊接接头的性能.为了通过控制焊接接头内部的晶粒形态和尺寸来提高焊接接头的性能，利用纵向磁场发生装置进行了低碳钢MIG焊接实验，对焊缝金属进行了金相及力学性能试验.结果表明，外加纵向磁场作用下与不加磁场进行比较，焊缝的抗拉强度提高了37.79%，焊缝的抗冲击韧性比不加磁场时增加了72.21%.可见外加纵向磁场焊接可以有效地细化焊缝的晶粒，提高焊接接头抗拉强度以及冲击韧性等力学性能.     

Stress singularity near the end of a cylindrical interface and the linear elasticity of push-in tests

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地磁场中空心铁磁圆柱体纵向磁化状态数值分析

在磁探测工作中,将潜艇壳体、武器弹药壳体等铁磁物体等效为空心薄壳铁磁圆柱体,对于分析它们的外部磁特征具有重要意义.采用三维积分方程法,建立了地磁场中空心铁磁圆柱体纵向磁化状态的数学模型,并按照不同的剖分格式进行了计算分析.一个典型实例的计算结果表明,三维积分方程法只需要少量剖分单元就可以很好地满足计算精度要求,大大减少了计算前的数据准备工作量.另外,根据磁感应强度求解问题,计算时间大大少于根据磁场强度求解问题,大幅度地加快了计算速度.三维积分方程法计算结果与实测结果具有很好的一致性,表明该计算方法是有效可行的,非常适合于计算空心薄壳铁磁圆柱体在地磁场中的纵向磁场特征.     

纵向磁场对WQ960钢焊接接头组织和性能的影响

为了研究纵向磁场对焊接接头的显微组织、冲击韧性和抗拉强度的影响,利用纵向磁场辅助MAG焊焊接WQ960高强钢.纵向磁场的施加提高了焊接接头的抗拉强度、冲击吸收功和冲击韧性,改善了焊接接头的显微组织,且焊接接头的显微组织主要由细小的针状铁素体构成.结果表明,当励磁电流达到2.5 A且磁场频率为20 Hz时,焊接接头的抗拉强度和低温冲击功均可达到最大值,分别为839 MPa和72 J,且分别提高了17.01%和24.14%;先共析铁素体和侧板条铁素体数量相应减少,因而形成了更多的针状铁素体.