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1.
This paper studies the dispersion of the axisymmetric longitudinal wave propagation in the pre-strained hollow cylinder consisting of two-layers under the shear-spring type imperfectness of the contact conditions between these layers. The investigations are made within the framework of the piecewise homogeneous body model by utilizing the 3D linearized theory of elastic waves in elastic bodies with initial stresses. It is assumed that the layers of the cylinder are made from compressible hyper-elastic materials and their elasticity relations are given through the harmonic potential. The degree of the mentioned imperfectness is estimated by the shear-spring parameter. Numerical results on the influence of this parameter on the behavior of the dispersion curves related to the fundamental mode are presented and discussed. It is established that the considered type imperfectness of the contact conditions causes two branches of the dispersion curve related to the fundamental mode to appear: the first disappears, but the second approaches the dispersion curve obtained for the perfect interface case by decreasing the shear-spring parameter. 相似文献
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Within the framework of the piecewise homogeneous body model the influence of the shear-spring type imperfect contact conditions on the dispersion relation of the generalized Rayleigh waves in the system consisting of the initially stressed covering layer and initially stressed half plane is investigated. The second version of the small initial deformation theory of the three-dimensional linearized theory of elastic waves in initially stressed bodies is applied and the elasticity relations of the materials of the constituents are described by the Murnaghan potential. The magnitude of the imperfectness of the contact conditions is estimated through the shear-spring type parameter. Consequently, the influence of the imperfectness of the contact conditions on the generalized Rayleigh wave propagation velocity is studied through the influence of the values of this parameter. Numerical results on the action of the imperfectness of the contact conditions and the influence of the initial stresses in the constituents on the wave dispersion curves are presented and discussed. In particular, it is established that the magnitude of action of the imperfectness of the contact conditions under the influence of the initial stresses on the wave propagation velocity cannot be limited with corresponding ones obtained in the case where the contact between the constituents is complete and in the case where this contact is full slipping one. The possible application of the obtained results on the geophysical and geotechnical engineering is also discussed. 相似文献
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轻型车动力总成模态频率响应分析 总被引：5，自引：0，他引：5
本文用频率响应方法对某轻型车动力总成的应力响应进行了计算,分析诊断了动力总成的破坏原因,比较了不同改进方案下的动应力水平并选出了较优方案。 相似文献
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一种多孔铝合金制备技术的研究 总被引：1，自引：0，他引：1
采用加压铸造法制备出多孔铝合金大块试样,系统地研究了浇注温度,充型压力等工艺参数对充型过程的影响。实验表明,预制块的初始预热温度对最终制品的有效长度起着重要作用,高的浇注温度及较大的充型压力也有助于金属液向空隙的渗透。 相似文献
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David Moens Dirk Vandepitte 《International journal for numerical methods in engineering》2004,61(14):2480-2507
This paper focusses on the application of the interval finite element method in dynamic analyses. It describes a methodology for calculating frequency response function envelopes from a finite element model containing imprecise parameters defined as interval uncertainties. The resulting envelope functions give a conservative approximation of the possible range of the frequency response function, taking into account that the uncertain parameters in the model can adopt any value in their presumed uncertainty intervals. The methodology is based on the modal superposition principle. It consists of an interval aritmethic algorithm which processes the results of a preliminary global optimization performed on the modal parameters. The algorithm is constructed such that it optimally combines the advantages of both the anti‐optimization and the interval arithmetic strategy for general numerical interval calculations. In the first stage of the development, the modal parameter ranges of each individual mode are independently combined in the modal response contributions. This yields the modal rectangle (MR) method. In order to remedy the high conservatism inherent to the MR method, the exact eigenfrequency ranges are added to the analysis. This results in the modal rectangle method with eigenfrequency interval correction (MRE). A second improvement consists of adding extra delimiters to the MRE modal parameter range approximation. This is achieved by performing an extra optimization on the modal response contributions at discrete frequencies. The method is referred to as the locally optimized modal rectangle method with eigenfrequency interval correction (OMRE). Finally, a numerical example illustrates the different algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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A. K. Singh R. P. Yadav K. C. Mistri A. Chattopadhyay 《Fatigue & Fracture of Engineering Materials & Structures》2016,39(5):624-636
An analytical solution has been attained to establish the closed form expression of stress intensity factor at the tip of a semi‐infinite crack, dynamically propagating in an initially stressed transversely isotropic poroelastic strip due to Love‐type wave for the case of concentrated force of constant intensity as well as for the case of constant load. The study presents the sound effect of various affecting parameters viz. speed of the crack, length of the crack, horizontal compressive/tensile initial stress, vertical compressive/tensile initial stress, porosity parameter and anisotropy parameter on the stress intensity factor. In order to delineate the effects of these aforementioned parameters on the stress intensity factor graphically, numerical simulations have been accomplished. One of the major highlight of the paper is the comparative study carried out for horizontal compressive/tensile initial stress, vertical compressive/tensile initial stress, porosity parameter and anisotropy parameter with the case when the strip is isotropic, non‐porous and free from initial stresses. Wiener–Hopf technique and the Fourier integral transform has been effectuated for the procurement of the closed form expression (exact solution) of stress intensity factor. 相似文献
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为深入研究ACL重建中移植物初始力对术后膝关节性能的影响,该文从MRI数据中提取膝关节各组织来构造出正常膝关节三维模型,通过对正常膝关节添加隧道与植入ACL移植物构建出ACL单束/双束重建膝关节模型。随后在压扭、压弯及压扭弯载荷作用下通过对ACL移植物施加10N~100N范围内的初始力进行有限元仿真,以此来分析初始力对关节软骨、半月板、移植物的应力分布影响以及对关节间接触力和关节位移的影响,所得结论如下：首先,单束/双束重建胫股关节的软骨、半月板的应力分布受初始力影响较小,其最大等效应力随初始力的变化分别不超过25%和20%,但移植物上的最大应力却随初始力的增加明显增大;其次,单束重建关节中半月板传递的轴向载荷随初始力增大而增加,双束重建关节中半月板传递载荷则随着初始力的增大反而减小;最后,在初始力10N~100N范围内,胫骨前移与所承受的前向力载荷之间基本成线性关系,前移量随初始力增大而减小。根据重建关节特性曲线表明,初始力对双束重建的影响稍微小于单束重建。 相似文献
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A new method is proposed for measuring the range rate of an airborne object in a frequency tuning regime. Mathematical modelling is used to study the effect of different factors on characteristics of the method. Limits for its application are determined. __________ Translated from Izmeritel’naya Tekhnika, No. 2. pp. 43–47, February, 2008. 相似文献
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Sven Knoth 《国际生产研究杂志》2013,51(15):4629-4647
Exponentially weighted moving average (EWMA) control charts are well-established devices for monitoring process stability. Typically, control charts are evaluated by considering their Average Run Length (ARL), that is the expected number of observations or samples until the chart signals. Because of the limitations of an average, various papers also dealt with the run length distribution and quantiles. Going beyond these papers, we develop algorithms for and evaluate the quantile performance of EWMA control charts with variance adjusted control limits and with fast initial response features, of EWMA charts based on the sample variance, and of EWMA charts simultaneously monitoring mean and variance. Additionally, for the mean charts we consider medium, late and very late process changes and their impact on appropriately conditioned run length quantiles. It is demonstrated that considering run length quantiles can protect from constructing distorted EWMA designs while optimising their zero-state ARL performance. The implementation of all the considered measures in the R package ‘spc’ allows any control chart user to consider EWMA schemes from the run length quantile prospective in an easy way. 相似文献
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用解卷积同态滤波识别桩身单缺陷界面反射 总被引：6，自引：0，他引：6
利用解卷积同态滤波,从桩顶反射波曲线的功率谱中分解得到频响函数│Ｈ（ｆ）│,在单缺陷界面反射条件下,根据│Ｈ（ｆ）│函数的基本特性可以确定反射系数及反射波往返时,进而确定桩身缺陷位置及缺陷严重程度,以实现桩身质量定量诊断的目的。给出了两根桩的桩身缺陷识别实例。 相似文献
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计算模型修正的频率响应函数方法 总被引：4，自引：0，他引：4
本文提出一种有限元动力分析计算模型修正的频率响应函数方法。这个方法综合考虑了系统的质量、刚度,特别是阻尼矩阵的修正,由位置矩阵将修正量集中体现在测量自由度上,利用结构系统的频率响应函数有限元分析值和实测值,计算出模型的质量、阻尼和刚度矩阵的修正量。文中算例结果表明,本方法有较好的修正结果。 相似文献
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基于FEM的正交异性压电复合材料传感研究 总被引：1，自引：0，他引：1
通过建立被测构件与压电正交异性复合材料(Orthotropic Piezoelectric Composite Materials，OPCM)传感元件的三维有限元(Finite Eleinelit Model，FEM)模型研究OPCM的动态传感特性．采用对被测构件施加冲击载荷的方法获得传感元件输出的电压时域信号，并进行傅立叶变换分析，计算和实验结果都表明OPCM传感元件对同平面内相互正交的应力波具有不同的频响特性，且两者之间有较好的吻合性． 相似文献
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In this paper, we propose an auxiliary‐information–based (AIB) Crosier cumulative sum (CCUSUM) t chart for monitoring the process mean, namely, the AIB‐CCUSUM‐t chart. The run length characteristics of the proposed chart are computed using Monte Carlo simulation. The optimal parameters for the AIB‐CCUSUM‐t chart to detect specific mean shifts are computed. The fast initial response (FIR) feature is also attached with the proposed chart. It is found that the AIB‐CCUSUM‐t and FIR‐AIB‐CCUSUM‐t charts perform uniformly and substantially better than the CCUSUM‐t and FIR‐CCUSUM‐t charts, respectively. An example is presented to support the theory. 相似文献
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Surkay D. Akbarov Hatam H. Guliyev Yusif M. Sevdimaliyev Nazmiye Yahnioglu 《计算机、材料和连续体（英文）》2018,55(2):359-380
The paper deals with a development of the discrete-analytical method for the solution of the dynamical problems of a hollow sphere with inhomogeneous initial stresses. The examinations are made with respect to the problem on the natural vibration of the hollow sphere the initial stresses in which is caused by internal and external uniformly distributed pressure. The initial stresses in the sphere are determined within the scope of the exact equations of elastostatics. It is assumed that after appearing this static initial stresses the sphere gets a dynamical excitation and mechanical behavior of the sphere caused by this excitation is described with the so-called three-dimensional linearized equations of elastic wave propagation in initially stressed bodies. For the solution of these equations, which have variable coefficients, the discrete analytical solution method is developed and applied. In particular, it is established that the convergence of the numerical results with respect to the number of discretization is very acceptable and applicable for the considered type dynamical problems. Numerical results on the influence of the initial stresses on the values of the natural frequencies of the hollow sphere are also presented and these results are discussed. 相似文献
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The dynamics of the moving-with-constant-velocity internal pressure acting on the inner surface of the hollow circular cylinder surrounded by an infinite elastic medium is studied within the scope of the piecewise homogeneous body model by employing the exact field equations of the linear theory of elastodynamics. It is assumed that the internal pressure is point-located with respect to the cylinder axis and is axisymmetric in the circumferential direction. Moreover, it is assumed that shear-spring type imperfect contact conditions on the interface between the cylinder and surrounding elastic medium are satisfied. The focus is on the influence of the mentioned imperfectness on the critical velocity of the moving load and this is the main contribution and difference of the present paper the related other ones. The other difference of the present work from the related other ones is the study of the response of the interface stresses to the load moving velocity, distribution of these stresses with respect to the axial coordinates and to the time. At the same time, the present work contains detail analyses of the influence of problem parameters such as the ratio of modulus of elasticity, the ratio of the cylinder thickness to the cylinder radius, and the shear-spring type parameter which characterizes the degree of the contact imperfection on the values of the critical velocity and stress distribution. Corresponding numerical results are presented and discussed. In particular, it is established that the values of the critical velocity of the moving pressure decrease with the external radius of the cylinder under constant thickness of that. 相似文献
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为明晰混凝土膨胀作用下弯折钢筋脆性断裂的机理,从导致脆断的推测起源-钢筋初期损伤入手,开展月牙纹钢筋在弯折参量及梯度递增弯折角度下的加工试验与数值模拟。探究钢筋直径与弯心直径对初期损伤形成的影响规律,探索各细分阶段下受挤压钢筋横肋的形变规律、初期裂纹尺度的演变特征,以及弯弧内部残余应力响应等,从而分析带肋钢筋因弯折加工形成初期损伤的规律与机制,并进一步探索抑制初期损伤的横肋形貌与加工参量。结果表明：较大的钢筋直径和弯折角度,较小的弯心直径会大幅增加初期损伤程度;严峻条件下(钢筋直径及弯心直径分别为16 mm及32 mm,弯折90°),月牙纹钢筋的初期损伤可达400 μm(钢筋直径的2.5%),超过了日本常发生脆性断裂竹节纹钢筋的水平,这增加了弯折钢筋受应力作用下初期损伤扩展的可能性;随弯折角度递增,钢筋横肋的挤压变形与根部应力集中程度愈发显著,且弯折90°卸载后弯弧内部由受压转为受拉应力状态,加剧了初期损伤的形成以及弯折钢筋如箍筋产生脆性断裂的敏感性;通过在月牙纹横肋与基圆之间设置适当的过渡圆角可较大程度缓解初期损伤。 相似文献