首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
离心机动不平衡量的配平方法   总被引:1,自引:0,他引:1  
本离心机用于标定加速度计模型参数的设备.从分析引起离心机动不平衡的原因入手,研究了静不平衡和偶不平衡对离心机的影响,认为静不平衡量测量和配平问题是解决所研究的盘式离心机动不平衡的关键.给出了静不平衡量的测试方法和计算公式,同时给出了静不平衡的配平原则和配平方法.通过实验验证了此方法的正确性和有效性,从而为离心机动不平衡量的配平提供了一种准确高效的方法.  相似文献   

2.
????? 《力学与实践》1991,13(4):61-61
<正> 考虑摩擦力的平衡问题分为两类:1.求平衡范围问题。此时,物系中的滑动摩擦力至少有一处达到了最大值,并需用静(或动)力学方程与物理方程联立求解.2.判断系统是否平衡,此时,物系中的滑动摩擦力均未达最大值,仅用静(或动)力学方程便可求解.  相似文献   

3.
在解决考虑静滑动摩擦力的物体、物系的平衡或运动的问题时,往往首先必须解决的问题是静滑动摩擦力应假定方向再讨论,还是应正确判断它的方向,以及如何判断其方向。这类问题可分二种情况来研究。一、主动力大小未知,求物体或物系平衡时主动力的范围。此时静滑动摩擦力的方向不能任意假设,必须经分析后确定其正确方向,否则不能解出正确的 ...  相似文献   

4.
基于Euler-Bernoulli梁的几何非线性理论,建立了弹性曲梁在任意分布机械载荷和热载荷共同作用下的几何非线性静平衡控制方程。该模型不仅计及了轴线伸长,同时也精确地考虑了梁的初始曲率对变形的影响以及轴向变形与弯曲变形之间的相互耦合效应。应用打靶法数值求解了半圆形曲梁在横向均匀升温作用下的非线性弯曲问题,数值比较了轴向伸长对曲梁变形的影响。  相似文献   

5.
混凝土结构在受到动载荷作用之前,通常已承受着初始静载荷的作用.大量关于混凝土应变率效应的研究均没有考虑初始静载荷对动强度的影响,会导致过高地估计混凝土的动强度,使混凝土结构设计偏于危险.本文通过分析混凝土材料在静动组合载荷下的率效应机理,给出了初始静载荷的定义.在此基础上,推导了混凝土材料参数与初始静载荷和应变率的表达式,提出了建立静动组合强度准则的一般方法.通过材料参数反映初始静载荷与应变率的联合影响,给出了由初始有效静载荷、动态黏聚强度和摩擦强度共同组成的混凝土动态强度,将广义非线性强度准则发展为静动组合多轴强度准则.建立的强度面在相同初始静载荷下随应变率的增大向外扩张,在相同应变率下随初始静载荷的增大向里收缩,即混凝土的强度在相同初始静载荷下随应变率的增大而增大,在相同应变率下随初始静载荷的增大而减小.此外,当初始静载荷和应变率不变时,加载路径对混凝土材料的应变率效应无影响,但会影响混凝土材料的静水压力效应,即当初始静载荷和应变率固定不变时,静动组合强度面的位置和大小即可确定,不同加载路径下强度的不同是由于静水压力效应导致的.最后利用多组混凝土材料静动组合强度试验对建立的静动组合强度准则进行了验证.  相似文献   

6.
<正> 1.计算方法简介对于环板,其平衡方程为式中(?)为环板内半径.对于内边界支承的环板,在最大弯矩极限条件下,其极限条件为 M_θ=-M_p,M_p,为塑性极限弯矩.于是,设  相似文献   

7.
应用新型动光弹系统研究某设备受冲击载荷作用   总被引:1,自引:0,他引:1       下载免费PDF全文
李松刚  杨国标  倪凡  李斌 《实验力学》2011,26(3):229-233
结构受到冲击时,其应力分布与在静荷载作用下完全不同.本丈应用新型动光弹实验系统研究了某设备在冲击载荷作用下其内部动态应力分布情况.该系统由部分传统的动光弹实验装置、高速摄影系统和数字光弹图像处理系统组成,并且采用激光光源、落锤冲击载荷加载装置.加工制作了该设备模型的光弹性模型,应用到冲击载荷作用下的实验研究中,得到了该...  相似文献   

8.
静载荷作用下柔韧圆板的大幅度振动   总被引:3,自引:1,他引:2  
本文首先给出了均布载荷作用下柔韧圆板的大幅度振动方程,按文中给出的时间模态假设导了该问题的非线性耦合的代数和微分特征方程组,利用修正迭代法求出了该方程组的近似解析解,得到了柔韧圆振动的幅频-载荷特征关系,讨论了静载荷对其振动性态的影响。  相似文献   

9.
超临界条件下固支边界输液管的内共振   总被引:1,自引:0,他引:1  
运用摄动方法研究固支边界条件下的弹性输液管道的横向非线性振动.随着输液管道内流体流动的速度增大至临界流速以上时,输液管道的平衡位形将会发生屈曲变形,变成零静平衡解以及一对称的非零静平衡解.对于超临界管道系统的非零静平衡解的扰动方程,通过迦辽金方法截断使系统变为标准的有限维离散陀螺系统.运用离散多尺度方法以及陀螺系统的可...  相似文献   

10.
<正> 《力学与实践》1987年第3期发表了周庆华老师的一篇文章,题为《摩擦力的方向问题及其判断方法》.本人持不同意见,在此和您商榷.文中(指《摩擦力的方向问题及其判断方法》一文,下同)所说的第一种情况是:“主动力大小未知,求物体或物体系平衡时主动力的范围,此时静滑动摩擦力的方向不能任意假设,必须经分析后确定其正确方向,否则不能解出正确的值.”实际上,此时只要约束充许,静滑动摩擦力的方向是可以假设的,而且对于不易确定静摩擦力的方向的问题,假设其方向是方便的,甚至  相似文献   

11.
研究弹性地基上带传力杆的间断中厚矩形板的非线性静力特性。荷载在传力杆中的传递由竖向弹簧模拟,其弹簧刚度取决于传力杆的特性以及杆与板间的相互作用。根据能量变分原理,考虑地基耦合效应,建立了双参数地基上带传力杆的间断矩形中厚板的非线性静力控制方程。构造出一组满足所有边界条件的试探函数,应用伽辽金法对该组非线性方程进行求解。数值算例中,讨论了传力杆参数、板的结构参数及地基参数对弹性地基上间断矩形中厚板的非线性静力特性的影响。  相似文献   

12.
Nonlinear equations of motion for orthotropic plates are proposed on the basis of the three dimensional nonlinear theory of elasticity. The resulting plate model provides a high accuracy, which is confirmed by solving the Vlasov static problem of bending a hinge-supported plate under sinusoidal load.  相似文献   

13.
Gorguluarslan  Recep M.  Gungor  O. Utku  Yıldız  Saltuk  Erem  Erdem 《Meccanica》2021,56(11):2825-2841

The objective of this study is to investigate the energy absorption performance of the graded lattice energy absorbers designed by a stiffness-based size optimization process under static loadings applied during the in-service conditions. The energy absorber geometry is modeled using three different lattice types, namely complex cubic, octet cubic, face- and body-centered cubic. The stiffness-based size optimization subjected to a static bending load is conducted to determine the optimal strut diameters which produced graded lattice structure designs. To investigate the energy absorption behavior of these graded lattice designs, the nonlinear dynamic explicit finite element analysis (FEA) is conducted under quasi-static compression for each design. The lattice designs are fabricated by a material extrusion technique using the polylactic acid material and the quasi-static uniaxial compression tests are conducted on the fabricated designs. The FEA results are found to be in good agreement with the experimental results. When compared with uniform counterparts, the presented graded lattices exhibit the improved energy absorption in response to uniaxial compression although their designs were derived from a stiffness-based size optimization with bending load.

  相似文献   

14.
We study static and dynamic stability problems for a thin flexible rod subjected to axial compression with the geometric nonlinearity explicitly taken into account. In the case of static action of a force, the critical load and the bending shapes of the rod were determined by Euler. Lavrent’ev and Ishlinsky discovered that, in the case of rod dynamic loading significantly greater than the Euler static critical load, there arise buckling modes with a large number of waves in the longitudinal direction. Lavrent’ev and Ishlinsky referred to the first loading threshold discovered by Euler as the static threshold, and the subsequent ones were called dynamic thresholds; they can be attained under impact loading if the pulse growth time is less than the system relaxation time. Later, the buckling mechanism in this case and the arising parametric resonance were studied in detail by Academician Morozov and his colleagues.In this paper, we complete and develop the approach to studying dynamic rod systems suggested by Morozov; in particular, we construct exact and approximate analytic solutions by using a system of special functions generalizing the Jacobi elliptic functions. We obtain approximate analytic solutions of the nonlinear dynamic problem of flexible rod deformation under longitudinal loading with regard to the boundary conditions and show that the analytic solution of static rod system stability problems in a geometrically nonlinear statement permits exactly determining all possible shapes of the bent rod and the complete system of buckling thresholds. The study of approximate analytic solutions of dynamic problems of nonlinear vibrations of rod systems loaded by lumped forces after buckling in the deformed state allows one to determine the vibration frequencies and then the parametric resonance thresholds.  相似文献   

15.
李清禄  李世荣 《计算力学学报》2014,31(3):340-344,389
基于直法线假设,采用可伸长梁的几何非线性理论,建立了功能梯度材料弹性组合曲梁受切线均布随从力作用下的静态大变形数学模型。该模型不仅计及了轴线伸长,同时也精确地考虑了梁的初始曲率对变形的影响以及轴向变形与弯曲变形之间的耦合效应。用打靶法数值求解了由金属和陶瓷两相材料所构成的一种FGM组合曲梁在沿轴线均布切向随动载荷作用下的非线性平面弯曲问题,给出了不同梯度指标下FGM弹性曲梁随载荷参数大范围变化的平衡路径,并与金属和陶瓷两种单相材料曲梁的相应特性进行了比较。  相似文献   

16.
Antonini  A.  Gioffrè  M.  Gusella  V. 《Nonlinear dynamics》2002,28(1):83-102
This paper deals with the static and dynamic response of acantilever beam affected by Gaussian and non-Gaussian vectorprocesses. The load is modeled by three different correlationstructures based on the second-order Markov process, and thenon-Gaussian random features are described by translationprocesses. Both the linear and geometrically nonlinear behaviorare described using the finite element approach, and the beammechanical characteristics (natural frequencies and damping) arevaried to investigate their influence on the response. Finally,the Monte Carlo approach is used to estimate the responsestatistics. The transverse displacement and the bending moment atthe beam joints are used to summarize the obtained results interms of skewness and kurtosis coefficients, and probabilitydensity functions. The study presented in this paper providesinformation on the influence of the load nature and the structuralbehavior on the response random features.  相似文献   

17.
贾金政  马连生 《应用力学学报》2020,(1):231-238,I0016
基于一阶非线性梁理论和物理中面概念,导出了纵横向载荷作用下功能梯度材料(FGM)梁非线性弯曲和过屈曲问题的控制方程,并获得了该问题的精确解;据此解研究了梯度材料性质、外载荷、横向剪切变形以及边界条件等因素对功能梯度材料梁非线性力学行为的影响,分析中假设功能梯度材料性质只沿梁厚度方向,并按成分含量的幂指数函数形式变化。结果表明:纵横载荷共同作用下,功能梯度梁的弯曲构形将有无限多个;随着梯度指数的增大,梁的变形减小,临界载荷升高;随着长高比的增大,横向剪切变形的影响减小。  相似文献   

18.
In this study, rubberized concrete samples were prepared by partial substitution (5 %, 10 % and 20 % replacements by volume) of sand by waste crumb rubber, and tested under impact three-point bending load, as well as static load. Three types of specimens (size 50?×?100?×?500 mm) namely, plain concrete, rubberized concrete, and double layer concrete (with rubberized concrete top and plain concrete bottom) were loaded to failure in a drop-weight impact machine by subjecting to 20 N weight from a height of 300 mm, and another three similar specimens were used for the static load test. In both the tests, the load–displacement and fracture energy of each specimen were investigated. Finite-element simulations were also performed to study the dynamic behaviors of the samples, by using LUSAS V.14 software. It was noticed that, the impact tup, and inertial and bending loads increased with the increase in the percentage of sand replacement by crumb rubber. It was interesting to observe that these effects were more significant in the double layer specimen compared to the plain and rubberized concrete samples. The static peak bending load always decreased with increase of rubber in the mix. In general, the strength and energy absorbing capability of rubberized concrete was better under impact loading than under static loading. The simulated load against displacement behaviors of all the samples were validated by the experimental results.  相似文献   

19.
In this paper,fundamental equations and boundary conditions of the nonlinearbending theory for a rectangular sandwicl plate with a soft core are derived by meansof the method of calculus of variations.Then the nonlinear bending for a simplysupported rectangular sandwich plate under the uniform lateral load is investigated byuse of the perturbation method and a quite accurate analytic solution is obtained.  相似文献   

20.
饱和多孔弹性Timoshenko梁的大挠度分析   总被引:1,自引:0,他引:1  
基于微观不可压饱和多孔介质理论和弹性梁的大挠度变形假设,考虑梁剪切变形效应,在梁轴线不可伸长和孔隙流体仅沿轴向扩散的限定下,建立了饱和多孔弹性Timoshenko梁大挠度弯曲变形的非线性数学模型.在此基础上,利用Galerkin截断法,研究了两端可渗透简支饱和多孔Timoshenko梁在突加均布横向载荷作用下的拟静态弯曲,给出了饱和多孔 Timoshenko梁弯曲变形时固相挠度、弯矩和孔隙流体压力等效力偶等随时间的响应.比较了饱和多孔Timoshenko梁非线性大挠度和线性小挠度理论以及饱和多孔 Euler-Bernoulli梁非线性大挠度理论的结果,揭示了他们间的差异,指出当无量纲载荷参数q>l0时,应采用饱和多孔Timoshenko梁或Euler-Bernoulli梁的大挠度数学模型进行分析,特别的,当梁长细比λ<30时,应采用饱和多孔Timoshenko梁大挠度数学模型进行分析.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号