一般情况下小垂度索的刚度方程及其应用

索单元的刚度随变形而变化,索结构的力学分析是一个典型的几何非线性问题,因而在数值分析中单索的刚度方程显得尤为重要。由于许多文献不常见的单索刚度方程在推导时忽略了索单元元弦向倾的影响,用来进行结构计算尚存在一定的误差。本文因此考虑了影响单元刚度的弦倾角等因素,推导了一般情况下小垂度索的显式表达刚度方程,并运用该刚度方程进行结构数值分析,与采用近似刚度方程的分析结果进行了比较,给出了近似刚度方程与本文     

由润滑油密度求黏度的新黏压关系式探讨

研究了润滑油密度与黏度的关系,并提出了一个由密度求黏度的新黏压关系式.以Dowson-Higginson密度公式为媒介,新公式只改变一个常数可退化为Barus黏压关系,而改变两个常数可退化为Doolittle自由体积黏压关系.用Dowson-Higginson密压关系消去密度,新公式具有与Roelands黏压关系相同的结构,但对应常数各不相同.以squalane油为例,给出了由实验数据确定新公式中两个待定常数的简单方法,而如此确定下来的新公式可以与全部实验数据吻合良好.应用新公式计算黏度并以squalane油品为润滑剂,可顺利求得等温椭圆接触弹性流体动力润滑的数值解,说明新公式具有良好的适应性.     

弹体侵彻深度计算公式对比研究

讨论了目前应用较广的弹体对混凝土侵彻深度计算公式,并与试验结果进行对比,分析各经验公式及理论公式的计算误差。     

两异径湿球颗粒间静态液桥力的近似解析公式及数值评测

针对异径球形湿颗粒间液桥力,以Young-Laplace公式为基础,结合环形近似法并引入等效半径,在宽松设定的条件下推导出了简化的近似解析公式。此公式形式简洁,且当两球半径相等时,可回归到Pitois等提出的径球液桥力公式。本文对此近似解析公式进行参数敏感度分析,发现随着颗粒间距的增大,液桥力对颗粒半径的敏感度降低。此外,本文近似解析公式与其他实验和理论结果进行对比发现,该近似解析公式与上述实验和数值结果相当吻合,表明该近似解析公式可以较准确地计算接触角较小时的异径球颗粒间的液桥力,因而适于湿颗粒系统的数值模拟。     

闭式柴油喷嘴阀体座面的冲击应力计算

介绍按应力波理论推导出的无推杆式低惯量喷油嘴的针问座面冲击应力的计算公式,该式不仅为此类喷油嘴的设计和启喷压力的选择提出了一个可靠的理论依据,也解决了长期以来此类喷油嘴用传统计算公式计算得到的允许启喷压力值与其实际应用的启喷压力值不一致的矛盾．     

On the Rayleigh Wave Speed in Orthotropic Elastic Solids

Recently, a formula for the Rayleigh wave speed in an isotropic elastic half-space has been given by Malischewsky and a detailed derivation given by the present authors. This study deals with the generalization of this formula to orthotropic elastic materials and Malischewsky’s formula is recovered as a special case. The formula is obtained using the theory of cubic equations and is expressed as a continuous function of three dimensionless material parameters.     

白铜弹簧丝两级载荷下累积疲劳损伤预测模型

通过对文献中白铜弹簧丝疲劳寿命试验数据的分析,给出了具带存活率的疲劳寿命曲线表达式。在此基础上,建立了两级载荷下累积疲劳损伤及概率分布的预测模型。     

Green's Function for Orthorhombic Aggregates of Weakly Anisotropic Cubic Crystals

Herein a closed but approximate formula of the Green's function is obtained for orthorhombic aggregates of cubic crystallites. This formula, which includes three material constants and three texture coefficients, accounts for the effects of the orientation distribution function (ODF) up to terms linear in the texture coefficients. Thus it is expected that our formula would be applicable to aggregates with weak texture or to materials such as aluminum whose single crystal has weak anisotropy. The approximate formula remains valid and assumes a simpler form when the polycrystal reduces to a weakly anisotropic cubic crystal. Two examples are presented to compare predictions from our formula with those from Nishioka and Lothe's formula and from Synge's contour integral through numerical integration.     

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根据岩心实验提出了两参数的非线性渗流方程,并在此基础上结合Buckly-Leverett 方程建立了非线性非混相驱替方程. 通过对该方程求解分析可知,与线性达西渗流相比,非 线性渗流的驱油相率较差;同一含水饱和度下的含水率更高;而储层中各点的压力梯度更大, 导致所需注采压差更大. 说明有效的开发低渗透油藏需要比中高渗油藏更小的井距和更高的 注采压力体系.     

A new formula for the C-matrix in the Somigliana identity

By making use of a convenient decomposition of the fundamental tractions, a new formula for the C-matrix in the Somigliana identity for a three- or two-dimensional elastic isotropic body is derived. This kind of formula is more advantageous for analytical and computational C-matrix evaluations than the currently well-known formula. A general closed analytical formula of the C-matrix for the case of any finite number of tangent planes to the boundary of the body at a non-smooth boundary point, presented in the final section of this paper, demonstrates the usefulness of the new formula.     

带弹簧支撑超静定结构位移的简化计算方法

针对带有弹性支撑的超静定结构的位移计算问题, 对利用虚功原理得到的位移计 算一般公式进行了进一步推导, 提出了该类结构位移的简化计算方法. 文中计算公式表达形 式简洁, 且与一般刚性支撑超静定结构的位移计算方法一致. 通过与有限元分析结果的对比, 证明了该公式的正确性.     

纵向剪切三相共焦点椭圆模型的精确解及其应用

推广夹杂问题的三相同心圆模型,提出了三相共焦点椭圆模型,从而计及了夹杂形状变化的重要因素。利用保角变换结合罗朗级数展开技术获得了纵向剪切载荷下的封闭形式解。本模型和解答对夹杂、界面层附近的细观应力场分析、对复合材料和含缺陷材料的有效弹性模量预测有重要实用价值,获得了比经典公式更精确的结果。对特殊模型,可以得到许多有意义的问题（如二相模型）的解答。     

爆破振动速度预测安全保证系数的确定

基于爆破振动速度预测公式回归分析的基本原理,提出根据建筑物不同安全等级应选择一定的可靠性指标,并推导了预测爆破振动速度公式中所含安全保证系数的计算过程。为简化计算过程,又进一步提出了基于监测数据量、回归分析相关系数以及可靠性指标的关于安全保证系数计算的经验公式。经过大量监测数据验证了该经验公式的计算精度和可靠性均能满足工程实际需要,从而修正了萨氏公式预测精确度不够的缺陷,可为重要建筑物周边的安全爆破设计提供参考。     

A new analytical formula to compute the step length of Padé approximants in the ANM: Application to buckling structures

In this paper, we propose a new analytical formula to define the next branch in the Asymptotic Numerical Method (ANM) using the Padé approximants. The proposed formula is based on the computation of the relative error of two consecutive Padé approximants. This formula is obtained by developing the relative error with respect to the path parameter. An appropriate matrix formulation is adopted for the computation of this relative error. A comparison between the analytical formula proposed in this paper and the classical continuation Padé approximants using the step length computed numerically using dichotomy method is presented for examples of buckling structures.     

外框密肋复合墙抗剪机理及承载力计算

在外框密肋复合墙低周反复荷载试验的基础上,对墙体的抗剪机理进行了分析;依据极限平衡理论引入砌体抗剪承载力影响系数和框格承载力影响系数,同时考虑RC框格与填充砌块之间的相互作用;提出了外框密肋复合墙抗剪承载力计算公式;本文公式计算结果与试验结果、有限元数值模拟结果进行了比较。研究表明:本文基于水平薄弱层破坏建立的外框密肋复合墙抗剪公式较传统基于斜截面破坏建立的抗剪公式具有更明确的物理意义;本文公式计算精度较高,与试验结果、有限元数值模拟结果相差不到10%。     

Rotation invariant constitutive relation for Reynolds stress structure parameter

A new Reynolds stress constitutive formula is constructed using the firstorder statistics of turbulent fluctuations instead of the mean strain rate. It includes zero empirical coefficients. The formula is validated with the direct numerical simulation(DNS) data of turbulent channel flow at Reτ =180. The Reynolds stresses given by the proposed formula agree very well with the DNS results. The good agreement persists even after the multi-angle rotation of the coordinate system, indicating the rotation invariance of the formula. The autocorrelation of the fluctuating velocity rather than the mean strain rate is close to the essence of the Reynolds stress.     

A general formula for the drag on a sphere placed in a creeping unsteady micropolar fluid flow

In the present work, we investigate the creeping unsteady motion of an infinite micropolar fluid flow past a fixed sphere. The technique of Laplace transform is used. The drag formula is obtained in the physical domain analytically by using the complex inversion formula of the Laplace transform. The well known formula of Basset for the drag on a sphere placed in an unsteady viscous fluid flow and that of Ramkissoon and Majumdar for steady motion in the case of micropolar fluids are recovered as special cases. The obtained formula is employed to calculate the drag force for some micropolar fluid flows. Numerical results are obtained and represented graphically.     

BOUNDARY INTEGRAL FORMULA OF ELASTIC PROBLEMS IN CIRCLE PLANE

IntroductionConcerningtheelasticplaneprobleminaunitcircle ,ZhengShenzhouandZhengXueliangdevelopedaboundaryintegralformulaofthestressfunction[1]:Φ(r,θ) =-( 1 -r2 ) 24π ∫2π0ν( φ)1 -2rcos(θ-φ) r2 dφ　　 12π∫2π011 -2rcos(θ-ω) r2 dω∫2π0μ( φ)1 -cos(ω-φ) dφ　　 1 -r22π∫2π0μ( φ)1 -2rcos(θ -φ) r2 dφ　　 ( 0 ≤r <1 ) ,( 1 )whereμ(θ) =Φ(r,θ) ｜r=1,ν(θ) = Φ n r=1= Φ r r=1.Intheformula ( 1 )theseconditemisastrongsingularintegral,itshouldbeunderstoodasanintegra…     

圆外Stokes问题的边界积分公式

针对圆外区域的Stokes问题,利用Fourier展开法,通过自然边界归化得到了一个只与边界速度有关的Stokes问题的边界积分公式.根据此公式及边界速度值,求得区域内速度及压力分布的解析表达式,并通过数值积分的方法进行求解,计算量小,所得速度及压力分布图曲线光滑.最后借助流体软件进行数值计算,结果验证了边界积分公式的正确性、可行性.     

CONDITIONS FOR THE APPLICATION OF THE STRESS TRANSFORMATION FORMULA 1)

斜面应力公式,即一点应力的坐标旋转变换公式,是材料力学和弹性力学里最常用的公式之一,并广泛用于固体力学和工程设计中。一个让学生感觉例外的典型例子是含V 形切口的薄板在切口尖端的应力情况,如果利用斜面应力公式和切口面的自由面条件,就会得出切口尖点处于零应力状态的结果,而这与线弹性断裂力学给出切口处应力趋于无限大的结果不符。为消除这一疑虑,考察了尖端应力的特性,指出：只有在过一点的各个斜面上的应力是单值连续的情况下,斜面应力公式才能适用,此时,该点的全部应力分量组成应力张量。在V形切口的尖端、裂纹尖端,自由面与顺其延伸至介质内侧的面上的应力不同,应力在该面上就不是单值连续的,该点的应力状态就不能用张量表示,斜面应力公式在切口或裂纹尖端就不适用了。