钻孔偏心对松弛应变和残余应力的影响

用盲孔释放法测残余应力的基本理论导出在任意钻孔偏心下应变释放系数 A、B 的精确公式.同时通过用偏心公式和不偏心公式计算得到的残余应力值的比较,说明钻孔偏心量对残余应力值影响很大.     

钻孔偏心下的应变释放系数及残余应力

用钻孔应变释放法测残余应力的基本理论导出在任意钻孔偏心下应变释放系数[A],[B]的精确公式.揭示了各传统近似方法(丝栅中心应变法、纵向线积分平均应变法及有效面积上积分平均应变法)的应变释放系数随r_м/а的变化规律。并采用数值逼近法求解了钻孔偏心时的应变释放系数及残余应力.结果表明,偏心对残余应力影响很大。     

钻孔法测量残余应力中几个问题的探讨

本文针对钻孔法测量残余应力中一些不能用“释放”理论解释的问题,通过对钻孔法基本测量原理的分析和与其它传统电测方法对比,认为常用于测量残余应力的电测方法中钻孔法应定义为“干扰法”,切条法和套孔法为“释放法”,Sach＇s镗削法则为“干扰-释放法”.根据实验结果推荐公式=(λ-1)~(1/2)为预测钻孔深度的经验公式.同时应用“干扰”理论分析了压痕法测量残余应力的基本特性,提出压痕法与电测法结合将发展成为一种近似无损的测量残余应力的新方法.     

钻孔法测量残余应力过程中钻孔附加应变的研究（Ⅱ）

本文应用弹塑性理论研究了被测试样的屈服强度、应力场对钻孔法测量残余应力过程中钻孔附加应变的影响,使用简化的理论模型推导了低速旋转钻头钻孔产生附加应变的一般表达式.结果表明钻孔引入的附加应变与被测试样的原始残余应力状态有关,随应力水平增加而增大,在压应力减小到某一临界值σ时,钻孔附加应变为零。在 Ly12铝合金上的实验测量结果与理论结果一致。     

钻孔法测量残余应力过程中钻孔附加应变

本文叙述了钻孔法测量残余应力过程中的附加应变.研究应力水平对附加应变的影响是在单向应力条件下进行的,结果表明,钻孔条件、材料状态以及残余应力达到一定值时,附加应变为零.     

整体化复合材料结构残余应力实验研究

通过钻孔法测试了T型整体化复合材料结构件在不同固化工艺方案下的残余应力,并研究了多墙类加筋壁板的腹板和蒙皮的残余应力分布,以及不同钻孔深度对结构件内部残余应力测试结果的影响。研究结果表明:共固化方式下产生的残余应力要小于胶结共固化方式下的残余应力。     

大错位量散斑干涉法测量残余应力

本文提出大错位量激光散斑干涉法结合钻孔法测量残余应力,对单向拉伸残余应力进行了测量,试验结果与理论解非常吻合,并且实现了对真实构件表面残余应力的测量.     

接合残余应力在界面端的应力奇异性

接合残余应力对异种接合材料强度的影响很大，正确地分析接合残余应力在界面端附近的分布及其奇异特性，是研究异材强度评价方法的关键问题之一，本文利用弹性学中的Ｇｏｕｒｓａｔ公式和有关微分方程解的理论，求得了平面近似下的界面端附近的残余应力场及其应力奇异性，与单纯的外力作用时的情况不同，残余应力在界面端有可能出现对数型的应力奇异性，并且不能仅用Ｄｕｎｄｅｒｓ的异材参数来描述。     

钻孔法测定焊接残余应力时的εp

用钻孔法测定焊接残余应力，孔边塑性变形对测量精度有很大影响。本文对孔边屈服过程进行了研究。克服了以往在误差修正方法中的不足，确定了塑性释放应变εｐ与主应力δ１、δ２和主方向角β的函数关系：εｐ＝ｆ（δ１、δ２、β），用以修正这塑变引起的测量误差，使得在二维应力状态下最大值近２０％的测量误差降至２％以下。     

云纹干涉与钻孔法测量搅动摩擦焊接头的残余应力

搅动摩擦焊是90年代出现的一种新型焊接技术,特别适用于熔化焊接性差的有色金属等材料.搅动摩擦焊接头的残余应力分别具有高应力梯度的特点,传统的应变片钻孔法不能满足测量要求.本文结合云纹干涉法与钻孔法的技术,得到了铝合金薄板搅拌摩擦焊接头残余应力沿深度和沿垂直焊缝方向的分布.     

APPLICATION OF THE MODIFIED METHOD OF MULTIPLE SCALES TO SOLVING THE PROBLEM OF A THIN CLAMPED CIRCULAR PLATE OF A VERY LARGE DEFLECTION

In this paper,asymptotic behaviour of the solution to the problem of a thin clamped circular plate under uniform normal pressure at very large deflection is restudied by means of the modified method of multiple scales given in[1?].The result presented herein is in good agreement with the one obtained by professor Chien Wei-zang who first proposed the method of composite expansions to solve this problem in[3].However,by contrast,the advantage of the modified method of multiple scales it seems to be relatively simpler than the method used in[3].It is also shown that the restriction of the method of paper[1-2]pointed out in paper[4]is not essential,and several computation errors in[3]are corrected as well.     

Control of nonlinear vibrations of vibrating ring microgyroscope

The influence of the basement rotation on the variations in the spectrum of vibration frequencies of thin elastic shells and rings was known already at the end of the 19th century [1]. The physical phenomenon of inertness of elastic waves occurring free vibrations of an axisymmetric body, first explained in [2], were practically used in developing new types of gyros [2–6]. The foundations of the theory of wave gyros were laid in [2, 4], and the errors of such gyroscopes for various shapes of the vibrating resonator were studied in [2, 4, 7, 8]. It was shown that the error of the resonator manufacturing (the variable density, thickness, anisotropy of the material elastic properties, etc.) [2, 8] and the geometric nonlinearity of the resonator flexural vibrations studied in [2, 7] lead to splitting of the natural frequency of flexural vibrations [2], which is reflected in the wave picture of the resonator vibrations and characterizes the gyroscope precision.In the present paper, we study the errors of the vibrating microgyroscope which arise because of nonlinear elastic properties of the ring resonator material. We construct a control of the potential on the electrodes which allows one to maintain the prescribed amplitude of the normal resonator deflection and compensate for the gyroscope errors arising because of the nonlinear elastic properties of the material.     

弹性常数对薄板大挠度弯曲的影响

本文针对薄板大挠度弯曲问题，导出了不同弹性常数对应解之间的等价关系式，研究了弹性常数对横向荷载－挠度、弯曲应力－挠度、中面应力－挠度等非线性表达式系数的影响，还分析了文献［１］中近似换算公式的误差。     

Abhängigkeit der Wärmeübergangskoeffizienten vom Wandtemperaturverlaufund die Konsequenzen für die Berechnung von Wärmedurchgangskoeffizienten bei Wärmetauschern

In a recent article [2] it has been shown that the common equation in VDI Heat Atlas [1], which has been used for the calculation of overall heat transfer coefficients, satisfies the energy balance of the heat exchanger in seldom exceptional cases only. This equation has been corrected for constant wall temperature. In this article an equation for the calculation of overall heat transfer coefficients valid for any shape of the wall temperature will be developed at which it becomes obvious, that only in the case of identical shapes of wall temperature in measurement and real heat exchanger process the calculation according to VDI Heat Atlas [1] is valid. In all other cases this procedure leads to errors.     

Response of a non-linear system with strong damping to multifrequency excitations

Summary In this paper, a new asymptotic calculation method is presented for a class of nonlinear nonautonomous vibration systems with multiple external periodic interferences. Simple calculation formulae of an asymptotic solution for resonance and off-resonance vibration are derived. The paper is concerned with a vibration system representing a class of nonlinear oscillators. Consequently, the calculation of a class of nonlinear oscillators is routinized. Two different Duffing equations are verified which shows that the results are completely in accordance with the solutions of references [3, 4, 6]. The derivation of solutions of Duffing equations becomes easier and simpler. In addition, some errors in reference [6] are pointed out.     

Stationary flow past the lower surface of a piecewise planar delta wing with supersonic leading edges

The considered wing has any finite number of inflections in its plane with lines of inflection intersecting at the point of inflection of the leading edge. In the present paper, this generalizes the author's earlier work [1] on flow past the undersurface of a flat wing at unite angle of attack with finite angle of slip and supersonic leading edges. In [1], calculations were not given. The special case of flow without slip in the same situation was considered later in [2], However, this paper contains errors, indicated at the end of the present paper. The calculations given in [2] are not correct. In the quoted papers, the gas flow is assumed to be a perturbation of a homogeneous flow behind a plane oblique shock wave. Such flows are treated systematically in [3]. Here and in [1], we use and generalize the representation of the linearized conservation laws across the shock front as the conditions of a boundary-value problem for an analytic function of a complex variable as obtained in [4, 5]. Calculations are given of the pressure distribution over the span for a number of different flow regimes and the pressure coefficients in the middle of the wing are compared with a numerical solution presented partly in [6].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 80–90, September–October, 1979.I am very grateful to V. I. Lapygin for making available a large number of variants of his numerical solution, and to L. E. Pekurovskii for assistance in the calculations.     

A KIND OF GENERAL INFLUENCE MEASURE ON THE LINEAR WEIGHTED REGRESSION

The linear weighted regression model is one of the models studied in many articles in recent years. Some further problems, such as disturbation, influence measure and estimate efficiency, have been discussed in this paper on the basis of the regression diagnosties. The partial conclusions of this paper are the extension of the familiar concepts in the regression diagnosties theory because they are representative of this kind of model.     

Kelvin-Helmholtz instability of a compressible plasma in a magnetic field

The Kelvin-Helmholtz instability of a compressible plasma in a uniform magnetic field with respect to disturbances propagating along the flow is considered. First, the case with the magnetic field parallel to the direction of streaming is considered. The result given by Sen [4] that the compressibility effects destabilize an otherwise neutrally stable system even in the hydrodynamic limit is apparently erroneous. Re-examination of the dispersion relation in the limit of small compressibility effects shows that the latter reduce the growth rate of an otherwise unstable disturbance. Attention is also drawn to errors in the calculations of Fejer [2] in the limit of small compressibility effects. Next, the case with the magnetic field transverse to the direction of streaming is considered. It is found that the transverse magnetic field does influence the stability of the system when the compressibility effects are present, contrary to the result given by Chandrasekhar [1] for the case of an incompressible plasma. However, interestingly enough, the compressibility effects are effectively reduced if a transverse magnetic field is present! It is further shown that the transverse magnetic field reduces the stability of the system.     

Comments on the paper “On the derivation of the constitutive equation of the simple fluid from that of a simple material” by R.R. Huilgol

Huilgol's paper [1] is discussed critically. It is shown that there are significant errors in each section of the paper. His argument depends critically on a refusal to recognize that when a statement is made that a functional of a tensor function is invariant under a group of transformations, these transformations must be constants and that otherwise the statement is meaningless. Furthermore, he consistently ignores the contradictions to which this refusal leads.     

The potential approximation in the theory of conical flows

The use of potential theory to describe external flows at intermediate supersonic velocities makes it possible to construct very fast algorithms for calculating the flow even in the presence of subsonic regions [1, 2]. However, this approach involves errors associated with the neglect of the increase of entropy in the bow shock. The magnitude of these errors and their effect on the values of the various flow parameters are most easily estimated with reference to examples of conical flows. The shock-capturing projection-grid method [3] is used for integrating the conical potential equation. The results of calculating the flow past circular and elliptical cones, a triangular plate and a V-wing are compared with the corresponding solutions of the system of Euler equations. The region of applicability of the potential model is determined and it is shown that the satisfaction of the Hugoniot shock polar equation at the bow shock increases the error of the pressure calculations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 112–118, May–June, 1990.In conclusion the authors wish to thank V. V. Kovalenko for calculating the Euler equations and A. N. Kraiko for discussing the results.