Design and analysis of a smart composite pipe joint system integrated with piezoelectric layers under bending

Incorporating with the high electro-mechanical coupling performance of piezoelectric materials, design and analysis of an adhesively bonded smart composite pipe joint system were conducted. In this joint system, piezoelectric layers were integrated into the joint coupler in order to reduce stress concentration in the joint adhesive layer. To theoretically verify the composite action and efficiency of the integrated piezoelectric layers, an electro-mechanical model based on the first-order shear deformation theory was established. This model was able to clarify the energetic characteristics of the proposed joint system on the improvement in the joint strength, which was under the action of a bending moment at the joint ends. The state-space method was utilized to obtain the final analytical solutions, including the peel and shear stress distributions in the adhesive layer. Finally, some numerical examples were calculated to evaluate the effect of the detailed stacking sequence and size of the integrated piezoelectric layers on reducing the stress concentration in the adhesive layer as well as the applied electric fields. These numerical results validated the integrity of the developed adhesively bonded smart composite pipe joint system.     

304L/Q235B大面积金属板爆炸焊接物质点法模拟分析

大面积金属板材304L/Q235B的爆炸焊接过程涉及炸药爆轰、金属板材的高速碰撞和塑性变形等。采用有限元法计算模拟这个问题时,网格单元会发生扭曲畸变现象,导致计算精度下降,甚至出现单元负体积而使计算终止,并且炸药爆轰形成气体产物飞散过程也很难模拟。为了能模拟大面积金属板材的爆炸焊接整个过程并获得合理的技术工艺参数,采用物质点法进行三维数值模拟分析。物质点法作为一种无网格法,在模拟冲击动力学问题中主要采用显式积分算法。通过将拉格朗日质点单元与固定的欧拉背景网格相结合,可以实现爆炸焊接的复板与基板的高速碰撞、炸药滑移爆轰、金属板面的塑性变形过程的数值模拟,并给出爆炸复合板材的形变、有效塑性应变和复板与基板的碰撞速度的计算结果。采用物质点法模拟的复合板材变形与爆炸焊接实验结果基本一致。计算复板与基板的碰撞速度这个重要的物理参数时,物质点法与Richter理论公式的相对误差不超过13%。数值计算和实验结果表明,物质点法在数值精度和计算效率方面具有优势,物质点法是研究金属焊接爆炸问题的一种有效数值方法。     

应变硬化薄板夹持型滚弯成形过程分析

现存文献对薄板的连续滚弯成形过程的数学模拟多限于讨论三辊轮解锥型弯板过程,且基于较多的假定和板的小变形情况。而开发有更多的功能和更高的生产效率的四辊轮连续弯板机需研究夹持型滚弯成形过程。本文将「１」的工作,理想塑性材料平面应变薄板的夹持型连续滚弯成形过程的弹塑性大变形弯曲的力学分析,推广至一般应变硬化材料的情形。得出了控制微分方程的解析解。采用固支边界条件模拟刚度很大的平持系统对板的夹持。通过对线     

Influence of prestress on the velocities of plane waves propagating normally to the layers of nanocomposites

The paper is concerned with longitudinal and transverse waves propagating at a right angle to the layers of a nanocomposite material with initial (process-induced residual) stresses. The composite consists of alternating layers of two dissimilar materials. The materials are assumed nonlinearly elastic and described by the Murnaghan potential. For simulation of wave propagation, a problem is formulated within the framework of the three-dimensional linearized theory of elasticity for finite prestrains. It is established that the relative velocities of waves depend linearly on small prestresses. In some composite materials, however, the thicknesses of the layers may be in a ratio such that the wave velocities are independent of the prestress level __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 3–22, July 2006.     

混凝土复合靶结构参数对侵彻过载的影响

混凝土复合靶基体靶板的层数和中间粘结层厚度是复合靶能否模拟单一靶的两个重要影响因 素, 利用AUTODYN2D仿真软件, 重点研究了这两个因素对弹体侵彻过载的影响. 首先通 过已有的实验和理论公式验证了初始仿真模型和材料参数的合理性. 在此基础上, 通过改变 基体靶板的层数和中间粘结层厚度建立了多组侵彻复合靶的仿真算例. 通过弹体侵彻速度、 过载曲线的对比, 结果表明: 全尺寸深侵彻过载实验中复合靶能够代替单一靶, 但复合靶中 间粘结层的厚度不要大于1/2弹头部长度; 当中间粘结层厚度超过弹头部长度1/2时, 弹体 侵彻复合靶过载与侵彻单一靶的偏离程度随基体靶板层数的增加而增大, 上述结论可为实验 中构建混凝土复合靶提供参考.     

Development of a smart composite pipe joint integrated with piezoelectric layers under tensile loading

To actively reduce the stress concentration effect in adhesive layers, a novel smart adhesively bonded composite pipe joint system was developed by integrating piezoelectric layers as sensor/actuator in the connection coupler. In the presently developed smart pipe joint system, the mechanical loading induced structural deformation can be detected and monitored by integrated sensing piezoelectric layers, and then the signal is fed back to the integrated actuating piezoelectric layers to adaptively produce additional forces and moments so as to decrease the maximum peel and shear stresses in the adhesive layer. In order to theoretically predict the efficiency of the developed smart pipe joint system, an electro-mechanical theoretical analytical model was established to investigate the characteristics of the joint system under end tension load in terms of first-order shear deformation theory. Simultaneously, the state-space method was utilized to deduce the final analytical solutions, including the peel and shear stress distributions in the adhesive layer. Finally, some detailed numerical results were obtained to demonstrate the optimal design method of such smart pipe joint system and further validate the integrity of this joint system.     

复合材料圆筒自由边效应的有限元分析

本文分析复合材料圆筒在内压作用下的自由边效应，讨论圆筒的叠层顺序对自由边应力的影响，预报最易发生边界脱层的界面．有限元分析结果表明：层间剪切破坏是该结构发生边界失效的主要原因，不同的叠层顺序可较大地影响自由边层间剪切应力，而大变形情况下线性有限元分析结果与非线性有限元数据相差较大，几何非线性的影响不容忽视．     

The thermoelastic Hertzian contact problem

A numerical solution is obtained for the steady-state thermoelastic contact problem in which heat is conducted between two elastic bodies of dissimilar materials at different temperatures with arbitrary quadratic profiles. Thermoelastic deformation causes the initially elliptical contact area to be reduced in size and to become more nearly circular as the temperature difference is increased. There is also a small but identifiable deviation from exact ellipticity at intermediate temperature differences. An approximate analytical solution is obtained, based on approximating the contact area by an ellipse.     

An approach for calculating the dynamic load of deep groove ball bearing joints in planar multibody systems

This study is focused on dynamic modeling of planar multibody systems with multiple deep groove ball bearing joints, in which the radial clearance, contact deformation, and bearing kinematics are included. By using the approach presented, the variation of the joint reaction force and the dynamic load on each ball element in bearings can be simulated. The deep groove ball bearing joints are modeled by introducing a nonlinear force system, which takes into account the contact elastic deformations between the ball elements and the raceways. The contact force is calculated by the Hertzian contact deformation theory that accounts for the geometrical and material properties of the contacting bodies. A planar slider-crank mechanism with two deep groove ball bearing joints is chosen as an example to demonstrate the application of the methodologies presented in this paper. In this model, one bearing locates at the joint between the ground and crank, while the other one locates at the joint between the crank and connecting rod. By numerical calculation, the dynamic load distribution characteristics of bearings under real mechanism movement conditions are simulated. From the results, it can be concluded that the dynamic load on each rolling element varies differently and belongs to a variable load with the change of mechanism configuration. Load characteristic analysis is the foundation of developing research on the fatigue life and reliability of bearings. This study will provide a key mechanical support for the performance evaluation, dynamic design, and geometrical parameter optimization of the joint rolling element bearings.     

The effect of transverse shear deformation on the buckling of two-layer composite columns with interlayer slip

This paper presents an efficient mathematical model for studying the buckling behavior of geometrically perfect elastic two-layer composite columns with interlayer slip between the layers. The present analytical model is based on the linearized stability theory and is capable of predicting exact critical buckling loads. Based on the parametric analysis, the critical buckling loads are compared to those in the literature. It is shown that the discrepancy between the different methods can be up to approximately 22%. In addition, a combined and an individual effect of pre-buckling shortening and transverse shear deformation on the critical buckling loads is studied in detail. A comprehensive parametric analysis reveals that generally the effect of pre-buckling shortening can be neglected, while, on the other hand, the effect of transverse shear deformation can be significant. This effect can be up to 20% for timber composite columns, 40% for composite columns very flexible in shear (pyrolytic graphite), while for metal composite columns it is insignificant.     

纤维增强混凝土材料的界面剪应力分布研究

针对纤维与混凝土界面的破坏过程,提出了几种简化的粘结-滑移本构模型,以双线性局部粘结-滑移本构模型为基础,在受力平衡和变形协调的基本原理基础上,推导了纤维脱粘过程中界面剪应力的解析解.采用弹簧粘结单元,通过数值方法模拟了纤维与混凝土之间的粘结-滑移过程,给出了纤维与混凝土界面脱粘过程中界面剪应力的分布、变化情况.对解析解、有限元计算结果和试验结果之间的差异进行了对比分析,验证了简化模型的合理性和有效性.     

Modeling elasto-plastic indentation on layered materials using the equivalent inclusion method

This paper develops a fast semi-analytical model for solving the three-dimensional elasto-plastic contact problems involving layered materials using the Equivalent Inclusion Method (EIM). The analytical elastic solutions of a half-space subjected to a unit surface pressure and a unit subsurface eigenstrain are employed in this model; the topmost layer is simulated by an equivalent inclusion with fictitious eigenstrain. Accumulative plastic deformation is determined by a procedure involving an iterative plasticity loop and an incremental loading process. Algorithms of the fast Fourier transform (FFT) and the Conjugate Gradient Method (CGM) are utilized to improve the computation efficiency. An analytical elastic solution of layered body contact (O’Sullivan and King, 1988) and an indentation experiment result involving a layered substrate (Michler et al., 1999) are used to examine the accuracy of this model. Comparisons between numerical results from the present model and a commercial FEM software (Abaqus) are also presented. Case studies of a rigid ball loaded against a layered elasto-plastic half-space are conducted to explore the effects of the modulus, yield strength, and thickness of the coating on the hardness, stiffness, and plastic deformation of the composite body.     

Exact slip-buckling analysis of two-layer composite columns

A mathematical model for slip-buckling has been proposed and its analytical solution has been found for the analysis of layered and geometrically perfect composite columns with inter-layer slip between the layers. The analytical study has been carried out to evaluate exact critical forces and to compare them to those in the literature. Particular emphasis has been placed on the influence of interface compliance on decreasing the bifurcation loads. For this purpose, a preliminary parametric study has been performed by which the influence of various material and geometric parameters on buckling forces have been investigated.     

复合材料层合板壳非线性力学的研究进展

复合材料层合板壳是由多种组分材料组合而成.与单一材料的板壳结构相比,它无明确的材料主方向,各层间材料间断和不连续,具有明显的几何非线性和材料非线性等新的特点.其失效模式也远比单一材料的情况复杂,具有如基体开裂、脱胶、分层、分层裂纹偏转、多分层以及分层传播等多种模式.各国学者基于不同的考虑,提出了多种方法研究复合材料层合板壳的失效.首先,在简要介绍了层合板壳线性力学基本理论的基础上,重点回顾了层合板壳结构非线性力学几种基本理论发展的过程,主要阐述了经典大挠度非线性理论、一阶剪切变形理论、高阶剪切变形理论、锯齿理论、广义分层理论的理论体系及基本公式,并对几种理论之间的联系和差异进行了总结;其次,介绍了当前层合结构非线性领域的研究进展,综述了典型复合材料板壳结构的失效机理及优化设计、复合材料板壳结构在复杂环境下的破坏机理、复合材料板壳结构的物理非线性、含脱层纤维增强复合材料板壳结构的破坏机理等各研究热点的最新研究成果;最后,对该领域未来的研究方向进行了展望.     

Stress near apex of dissimilar material with bilinear behavior

This study presents an analytical solution for the asymptotic stress field near the apex of a wedge composed of dissimilar materials exhibiting elastic and/or plastic deformation that can be described by a bilinear material model. Under the same assumptions, previous investigations resulted in eigenvalue differential equations that were not amenable to analytical integration. The present formulation avoids the numerical integration of such equations. After establishing its validity, the corner of the junction formed between a solder ball and a substrate was considered in order the study the effect of the hardening parameter on the strength of the singular stress field. Also, this formulation provides the exact form of the displacement field, which permits the construction of a global element to capture the correct strength of the singular stress field in regions with material and geometric discontinuities.     

Ultimate kinematic characteristics of composite solids accelerated by a magnetic field

The present paper considers the ultimate (under heating conditions) kinematic characteristics of composite solid bodies accelerated by unsteady magneticfield pressure. The accelerated sheet comprises two layers: a layer of a composite material consisting of a mixture of two materials with different electrothermal properties and a homogeneous material layer. The electrical properties of the composite layer with the coordinate are varied along the coordinate by changing the volume concentration of its constituent materials. For an exponential magnetic field rise, an analytical solution is obtained for the problem of determining the optimum distribution of the volume concentration of the composite constituents for which there is a maximum increase in the ultimate velocity of the sheet. Numerical simulation showed that the distribution of the volume concentration obtained from analytical relations is also nearly optimal for pulse shapes of the accelerating magnetic field different from exponential ones. The possibility of considerably increasing the ultimate velocity through the use of composite layers compared to the ultimate velocities for the homogeneous materials constituting the composite is shown analytically and numerically.     

人工智能在复合材料研究中的应用

复合材料以其轻质高强高模、可设计性强等优点成为结构轻量化的重要用材. 然而, 随着复合材料组分、结构以及性能需求的日益复杂化, 以实验观测、理论建模和数值模拟为主体的传统研究范式, 在复合材料力学性能分析、设计和制造等方面遇到了新的科学问题与技术瓶颈. 其中, 实验观测不足、理论模型缺乏、数值分析受限、结果验证困难等问题在一定程度上制约了先进复合材料在面向未来工程领域中应用的发展. 人工智能方法以数据驱动的模型替代传统研究中的数学力学模型, 直接由高维高通量数据建立变量间的复杂关系, 捕捉传统力学研究方法难以发现的规律, 在复杂系统的分析、预测、优化方面拥有与生俱来的优势. 而通过人工智能赋能来寻求复合材料中传统研究方法所面临难题的新的解决方案, 目前已成为复合材料研究领域的发展趋势. 本文综述并评价了人工智能方法在复合材料性能预测、优化设计、制造检测及健康监测等方面的研究进展, 并对未来发展方向进行了探讨和展望.      

Complicated deformation simulating on temperature-driven 4D printed bilayer structures based on reduced bilayer plate model

The four-dimensional (4D) printing technology, as a combination of additive manufacturing and smart materials, has attracted increasing research interest in recent years. The bilayer structures printed with smart materials using this technology can realize complicated deformation under some special stimuli due to the material properties. The deformation prediction of bilayer structures can make the design process more rapid and thus is of great importance. However, the previous works on deformation prediction of bilayer structures rarely study the complicated deformations or the influence of the printing process on deformation. Thus, this paper proposes a new method to predict the complicated deformations of temperature-sensitive 4D printed bilayer structures, in particular to the bilayer structures based on temperature-driven shape-memory polymers (SMPs) and fabricated using the fused deposition modeling (FDM) technology. The programming process to the material during printing is revealed and considered in the simulation model. Simulation results are compared with experiments to verify the validity of the method. The advantages of this method are stable convergence and high efficiency, as the three-dimensional (3D) problem is converted to a two-dimensional (2D) problem. The simulation parameters in the model can be further associated with the printing parameters, which shows good application prospect in 4D printed bilayer structure design.

     

压电/纤维复合材料耦合旋转驱动器力学设计模型

本文在经典层合板理论和三维压电材料本构方程的基础上,依据压电材料与纤维复合材料之间的相互作用、位移连续条件,建立了压电—纤维复合材料旋转耦合驱动器力学模型,并推导出电耦合方程。计算和初步实验说明,这种新型结构的压电伸缩变形—离轴纤维复合层扭转变形耦合旋转驱动器比同类型驱动器能量密度高、转矩大,且这种旋转电机结构简单紧凑、工作稳定、寿命长、预计随着研究的进一步深入,可望成为一种新型的微致驱动器而广泛应用于微型机械、精密测量和自动控制等领域。