对"压杆截面设计的图解法"的意见

在"压杆截面设计的图解法"文(《力学与实践》1985年第7卷第6期)中,作者为了避开几次反复计算,用"图解法"代替传统的"试算法",从而一次求得压杆截面的尺寸.但是,文中忽视了材料力学的一个基本概念:稳定安全系数(K_y,)与柔度(λ)有关,柔度越大,所取的稳定安全系数越小.而作者把稳定安全系数预先取为常数,这是不妥的.如果稳定安全系数与柔度无关,早期的学者也就不会采用试算的办法确定压杆截面的尺寸.     

关于压杆临界应力经验公式的小议

关于压杆的临界应力超过材料比例极限时的计算式,材料力学教材和有关的手册多应用直线型经验公式σ_(cr)=a-bλ(1)而在具体应用到某一种材料的压杆时,对柔度λ的下限和系数a,b的值,在不同的教材中有所不同。例 ...     

欧拉公式对针叶树木材压杆的适用范围

<正> 求细长压杆的临界应力用欧拉公式式中(?)为细长压杆的临界应力;E 为压杆材料的弯曲弹性模量;λ为压杆的柔度.式(1)由压杆的挠曲线近似微分方程推导得出.该方程只有在材料服从虎克定律的条件下才能成立.由     

Helmholtz方程的中值定理

本文提出并证明了二维和三维Ｈｅｌｍｈｏｌｔｚ方程的中值定理。令λ→０就得到二维和三维Ｌａｐｌａｃｅ方程的中值定理。     

中小柔度钢压杆稳定性设计的通用公式

中小柔度钢压杆稳定性设计的通用公式赵显慧，赵加祯（山西省吕梁煤炭工业学校，汾阳０３２２００）文［１］提出了考虑稳定性的压杆截面直接设计方法，但对型钢压杆设计计算失效．本文提出的通用公式则较完美地解决了这类问题，和文［２］提出的大柔度钢压杆稳定性设计通...     

工程压杆的变形和强度

压杆截面按轴力和弯矩联合作用考虑,计算大、中、小柔度工程压杆的变形和强度。     

基于动柔度法的门杆耦合

本文基于动柔度法法计算了闸门与启闭杆耦合的结构动态特性,比较了门杆开启的两种运行方式,初步探讨了抗振中门杆的相互关系     

冷质部件支撑结构中压杆的热过屈曲分析

以圆杆式冷质量支撑结构中的压杆为研究对象,考虑了材料线膨胀系数α随温度非线性变化的特性及材料本构关系的非线性,基于轴线可伸长原理建立了压杆的热过屈曲数学模型;利用打靶法分别分析了材料本构关系取线性模型和非线性模型时的压杆热屈曲过程,并对二者进行了对比。研究结果表明:无论材料本构关系采用线性模型还是非线性模型,当α取常数时临界屈曲温度与柔度无关;而当α随温度非线性变化时,柔度则对临界屈曲温度产生影响;在同一柔度下,考察α对屈曲特性参数的影响规律时材料本构关系的非线性特性不可忽略;在非线性本构关系下线膨胀系数随温度非线性变化时可得到最大轴向载荷、最小横向支座反力、最小轴线总伸长量;较小的横向支座反力可以有效减小支撑结构中心收缩位移,较小的轴线总伸长量可以有效减小压杆周向固定端连接处应力。     

杆、梁差分离散系统的柔度矩阵及其极限

本文导出了任意边条件的杆和悬臂梁、简支梁的格林函数及杆、梁离散系统的柔度矩阵，验证了柔度系数和格林函数之间的极限关系     

柔度方程在COD法测量疲劳裂纹长度中的应用

简介了COD技术测量裂纹长度的理论标定式.通过一套高精度的柔度测量系统,对GC4高强钢的两和热处理制度的CT试样进行了裂纹测量标定。调整柔度——裂纹表达式中的弹性模量E′,获得了高精度的实验柔度——裂纹(即BE′V/P-a/W)标定曲线.由实验观察提出了对BEV/P取对数的多项式标定函数,它此广为采用的以1/[(BEV/P)1/2+1]为项的多项式简单,无论是与理论计算值还是与实验值进行对比,前者均优于后者。     

大学物理《力学》中的自由度分析

对《力学》中的物体自由度进行多方面分析,以深化教学、提高学生正 确分析物理问题的能力.使用实际教学分析的研究方法,在《力学》范围内讨论自由度与坐标、 自由与约束的关系并得以下结论: (1) 同一物体的自由度随其所在的``空间'不同而不同, 不因坐标系的选取不同而 异, 在同类参考系中不因参考系的动静而有别;(2)自由度遵循叠加原理. 讨论了质点系的总自由度及相关计算问题,并指出研究《力学》中自由度的意义.     

Development and design of new methods of measurement of state of strain of structures

The present paper deals with development and design of new methods utilizing Wiedemann's effect for determination of state of strain in building structures. Wiedemann's effect and some features of torsional strain of magnetic field are the basis of new experimental method. Especially the point electromagnetic strain gages using the effect of pure torsion of electromagnetic field to enable universal examination. For strain-gage measurements, almost all physical quantities are used which can be related to the variation in length of the structures. From the electric strain measurements, the most commonly used methods are the measurements by resonance-wire strain gages or by electric-resistance strain gages. In this paper, electromagnetic strain gages are discussed using the Wiedemann effect, and the author describes some new measuring equipment and his own suggestions and methods based on an application of this effect.     

Calculation of aerodynamic characteristics of arrays of profiles of arbitrary shape

It is well known that the problem on nonseparating potential flow of an incompressible fluid about an array of profiles reduces to an integral equation for a certain real function, determined on the contours of the profiles of the array. As such a function one can take, as was done, for instance, in [1–5], the relative velocity of the fluid on the profiles of the array. For arrays of profiles of arbitrary shape it is necessary to solve the corresponding integral equation numerically. In the particular examples of the calculation of aerodynamic arrays that are available [1–3] the numerical methods used were based on the approximate evaluation of contour integrals by rectangle formulas. As investigations showed, sizeable errors arose thereby in the approximate solution obtained, these being especially significant in the case of curved profiles of relatively small bulk. In the present paper a method for the numerical solution of the integral equation obtained in [5] is proposed. The method is based on the replacement of a profile of the array with an inscribed N polygon, the length of whose sides is of the order N^–1 and whose internal angles are close to . Convergence with increasing N of the numerical solution to an exact solution of the integral equations at the reference points is demonstrated. Examples of the calculation are given.Novosibirsk. Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 105–112, March–April, 1972.