Calculation and Experimental Study of a Two-Way Reinforced Rubber-Cord Composite in Tension

A rubber-cord composite, reinforced in two directions with fibers of polyamide cord, under large tensile deformations is investigated based on calculations of a rubber-cord composite material and on tensile tests of specimens made of the casing of a diagonal truck tire. A method of the experimental tensile testing of rubber-cord composite specimens is described. The calculations are based on the carcass theory of composite materials. The calculated and experimental parameters of the macroscopic strains of the rubber tire cord and of its structure in a deformed configuration are given. The manifestation of edge effects in relation to the reinforcement angle is described.     

An Experimental and Numerical Investigation on the Low-Velocity Impact Response of Nanoreinforced Polypropylene Core Sandwich Structures

Mechanics of Composite Materials - The impact behavior of sandwich structures was studied using experimental and numerical methods. Polypropylene with 0.5 wt% of graphene (PP/0.5% G) or pure...     

Experimental and Numerical Study of the Open-Hole Tensile Strength of Carbon/Epoxy Composites

Open-hole tension tests are a part of the qualification process for composite parts that need to be joined to other parts in aircraft structures [1]. With each new material, a new set of tests is required. To reduce costs, it is desirable to develop analysis tools for the prediction of damage and failure in such tests, so that the amount of testing can be reduced and predictions can be made about material behaviour early in the design process. In this paper, an experimental and numerical study is presented on the notched (open-hole) strength of high-strength carbon/epoxy composites (HTA/6376). Open-hole tension tests have been performed on specimens with three different lay-ups — quasi-isotropic, zero-dominated, and cross-ply — in accordance with procedures in available standards. The data observed are being used to develop several methods for predicting the notched strength, and results from one such method using a progressive damage analysis are presented with comparisons with experiments. The predictions of specimen stiffness and failure load were found to agree well with experiments. To gain insight into the failure process, damage progression maps are shown.     

Experimental and Numerical Investigations of Al/Mg Compounds

Al/Mg compounds produced by hydrostatic extrusion exhibit unique characteristics regarding high strength and low weight, which are required by safety part applications in lightweight constructions. Between the two materials an interface in form of a brittle intermetallic phase consisting of Al₂Mg₃ and Al₁₂Mg₁₇ arises during the production process. However, a certain plastic deformability of the semi-finished product is essential for further forming processes. Even under multi-axle load during a radial upsetting process, the interface maintains a full material joint although a fragmentation and a new secondary interface between the fragments can be observed. Due to the evaluations of light microscopy images and Eulerian Hencky strain values at the interface, which are obtained with the help of the Digital Image Correlation, a relation between the strain and the boundary layer's appearance seems reasonable. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

An Experimental and Numerical Study of Deformable Bodies Contact

This study deals with the impact of a rotating disc elastically striking a strip. We establish an experimental setup including a disc with a throwing machine controlled by a dSPACE-Autobox to generate the translational and rotational motions of the disc, a properly fixed strip and a high-speed digital camera system with an image processing package to capture kinematical data of the disc. The effects of strip flexibility and disc initial normal velocity before impact are investigated in detail. For interpreting the experimental results a hybrid impact model is developed which can provide not only generally good predictions compared with measurements but also some insight into the influences of strip flexibility and disc initial motions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mechanical Properties of High-Density Polyethylene/Chlorinated Polyethylene Blends

Results of experimental investigation of mechanical properties of high-density polyethylene (HDPE)/chlorinated polyethylene (CPE) blends in tension are reported. The specimens of pure HDPE, CPE, and nine types of HDPE/CPE blends, with different component ratios at 10 wt.% intervals, are examined. The features of the stress-strain curves obtained are discussed. Data on the influence of blend composition on the elastic modulus, yield stress, breaking stress, and ultimate elongation are obtained. The results of investigations into the creep behavior are also presented. It is found that the creep compliance obeys the power law of creep with coefficients depending on blend composition.     

直接数值模拟／大涡模拟中数值误差影响的研究

通过比较湍流的能谱和总动能,对数值误差(包括混淆误差、离散截断误差)、亚格子模型以及它们之间相互作用对直接数值模拟和大涡模拟的影响进行了系统研究.算例采用了三维各向均匀同性湍流.为了研究复杂几何形状,数值格式采用了谱方法和Pade紧致格式.大涡模型采用了truncated Navior-Stokes(TNS)模型结合Pade离散滤波器.结果表明直接数值模拟中离散误差对结果有很大影响,低阶格式会导致计算发散.而大涡模拟中亚格子模型不仅能表征小尺度对大尺度的影响,而且还缓解了数值误差对计算结果的影响.因而低精度格式也可取得不错的结果.     

An Experimental/Numerical Investigation on Drag Reduction by Dimples

The paper is concerned with experimental and numerical investigations of the turbulent flow over dimpled surfaces. Shallow dimples distributed regularly over the wall of a plane channel with large aspect ratio are used to study their effect on the skin-friction drag. The resulting pressure drop in the channel was measured for smooth and dimpled walls. In addition to these investigations on internal flows, an external flow study was performed and boundary-layer profiles were measured using a Pitot-tube rake. Complementary to the measurements, direct numerical simulations for the internal flow configuration with and without dimples were carried out for two different grid resolutions and analyzed in detail. The objective was to clarify whether or not dimples cause reduction of the skin-friction drag. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

张力腿平台有限振幅运动的方程和数值解

论证了张力腿平台（TLP）在波浪作用下发生有限振幅运动时,所受惯性力、粘性力、浮力等载荷不仅与波浪场有关,还与瞬时响应有关,是响应的非线性函数;张力腿拉力也是各自由度位移的非线性函数．所以分析TLP受力时必须考虑平台的瞬时加速度、速度和位移,在瞬时位置建立运动方程．据此推导出TLP发生有限振幅运动时的外力计算公式,建立了TLP 6自由度有限振幅运动非线性控制方程．其中考虑了由6自由度有限位移引起的多种非线性因素,如各自由度之间的耦合、瞬时湿表面、瞬时位置等;还包括自由表面效应、粘性力等因素引起的非线性．用数值方法求解所得到的非线性运动方程．对典型平台ISSC TLP进行了数值分析,求得该平台在规则波作用下的6自由度运动响应．用退化到线性范围的解与已有解进行了对比,吻合良好．数值结果表明,综合考虑非线性因素后响应有明显改变．     

Numerical Approximation of Time Domain Electromagnetic Scattering from a Thin Wire

We present two new stable schemes for computing the current induced on the surface of a thin wire by an incident time-dependent electromagnetic field. The problem involves solving a retarded potential integral equation (RPIE). One algorithm solves the previously studied reduced kernel RPIE problem, and the other solves the more complicated exact kernel RPIE problem (for which there are no previous numerical results). Both algorithms behave stably for arbitrarily chosen values of the mesh size. Test experiments and numerically computed values of the induced current are presented.     

冲击波作用下Air/SF6斜界面不稳定性实验和数值模拟研究

开展了Mach数为1.23和1.41的冲击波作用下的Air/SF6斜界面不稳定性激波管实验,并利用王涛等人发展的可压缩多介质粘性流体和湍流大涡模拟程序MVFT(multi-viscous-fluid and turbulence),对该激波管实验进行了数值模拟,二者相比较一致性较好,包括界面图像、湍流混合区TMZ(turbulent mixing zone)宽度、气泡和尖钉位移,确认了该计算代码对界面不稳定性问题模拟的可靠性和有效性.数值模拟再现了冲击波作用下,Air/SF6斜界面的演化过程及流动中复杂波系结构的发展如冲击波的传播、折射和反射.结果还显示冲击波Mach数较大时,冲击波和界面相互作用时混合区获得的能量也较大,扰动界面发展的也更快.     

Experimental and Numerical Investigations for Cyclic Thermal Shocks

Thermal shock is an extreme form of thermo-mechanical loading. Detailed investigations of thermal shock and live time analysis close to reality are necessary in industrial engineering in order to get a good prediction of life expectancy of high quality and safety relevant machine components. The first part of this paper concentrates on experimental investigations of macroscopic quantities like temperature, deformation, damage and crack propagation. Additionally first results on parameter studies for finite element thermal shock simulations on the thermal-mechanical problem are summarized. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

数值分析实践教学实验设计

简述了数值分析课程实验设计的总体思路,设计了三个新的探索性实验,包括递归方程拟合、非光滑函数插值和奇异积分计算.这些实验均从最简单的情形出发,通过观察、比较、分析和联想得出了新的结论,有助于培养学生的创新思维能力,为更好地开展数值分析实践教学提供指导.     

Numerical Simulation of Free Oscillations of Elastic Bodies with a Thin Coating

We propose an approach to the investigation of problems on free oscillations of elastic bodies with a thin coating. The method consists of applying a combined mathematical model which is based on the three-dimensional equations of elasticity theory in the domain of a body and on the two-dimensional equations of the theory of shells of the Timoshenko type in the domain of a thin coating. The systems of these equations are related by the conditions of conjugation on the surface of contact. For the numerical analysis of the eigenvalue problem, we used a scheme of the finite-element method constructed by using approximations of different dimensionality.     

Thin bases of order h

A subset is called a basis of order h if every positive integer can be represented as a sum of h members of A. Thin bases of order h will be constructed in this paper, for each h?2, where the value of is smaller than that of thin bases known so far. In the most important case h=2 it is shown that for the considered class of bases (which generalizes an ansatz of Stöhr) the result is best possible up to an ε>0.