Applied Mechanics and Materials I

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Authors: Lin Li, Jin Yang, Xiu Qing Qian, Hai Xia Zhang, Zhi Cheng Liu
Abstract: Keywords: strain, stress, material constants, constitutive equation, anisotropy. Abstract. If the material is anisotropic, there are differences in stress distribution under the same boundary conditions when it was simplified as an orthotropic material. We established a simple finite element model for rectangular perforated planar material, in which one side was fixed, the opposite side was loaded with uniform force, and the other sides were set free. Based on this model we studied the difference of distribution of stress between anisotropic material and its simplified form, orthotropic material. The results showed differences in some cases quite large, the maximum relative error of extreme stress can reach 341%. In conclusions, this study does not support that the complex anisotropic materials are simplified to orthotropic materials. If researchers only concern the location of extreme stress, this study does not deny that the complex anisotropic materials can be simplified to orthotropic one.
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Authors: Rui Zhao, Yong Yao, Yong Jun Deng
Abstract: Based on the micromechanics principle, establish concrete random aggregate, constitutive model choose HJC model and K&C model, numerical Simulation for the part of the S.J.Hanchak projectile penetrating into concrete targets test. Through the bullets remaining projectile velocity and target plate failure compared, it is concluded that Concrete mesostructure uneven impact of its macro mechanics; flaking and spallation phenomena on the HJC model simulation of the target body front and back by the impact appears less effective, and K&C model is in good agreement with the experimental conditions; K&C model is a simple and effective way to predict the dynamic response of the projectile penetrating into concrete targets.
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Authors: Shu Ai Tian, Zhi Xue Wu
Abstract: Stress singularities exist on the interface endpoint or internal point, consisting of dissimilar linear elastic bonded wedges. The eigenvalue λ is an important parameter to represent the stress singularity on the interface singular point. And smaller eigenvalue represent stronger stress singularities on the interface singular points. The angular function is another parameter to represent stress singularities around singular points. It is known that the eigenvalue is influenced by the Young’s modulus, Poisson’s ratio and interface angles. The Airy stress eigenfunction method has been used to solve the eigenvalue on the bi- and tri-material junctions by verifying the Young’s modulus. And then talk about angular functions around the bi- and tri-material junctions’ singularity point. At last discuss the feasibility of enhancing the interfacial bonding strength in engineering practice.
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Authors: You Liang Xu
Abstract: The constitutive equation of large deformation problem is closely related to geometric description. Nowadays, linear strain tensor is no longer unsuitable to describe large deformation. However, the existing non-linear strain tensors have complicated forms as well as no apparent geometric or physical meaning. While, the increment method is used to solve, however, convergence and efficiency are low sometimes. Thus the idea of visual strain tensor is proposed, with distinct meaning and visual image. Beside, it is likely to be used in engineering measurement, and it can be connected with measured constitutive equation directly. Thus this research provides a new idea and method for solving large-deformation problems in practical engineering.
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Authors: Ya Lan Li, Wei Peng Guo, Wen Tao Jiang, Qing Yuan Wang, Yu Bo Fan
Abstract: The effect of shaping amplitude on the residual material strength of titanium implants was studied. A purposely built to and fro three point bending apparatus was developed for different amplitudes on the implant material. The strength of the material after different levels of amplitude was investigated thorough uniaxial tensile testing. The effect of stress concentration due to amplitude was investigated by finite element analysis. It was concluded that plastic deformation due to shaping amplitude produced different effect on the residual strength of the material.
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Authors: Ming Li, Xiao Ling Hu, Wen Bo Luo, You Jian Huang, Ji Ling Bu
Abstract: Mooney-Rivlin model and Ogden model are frequently used by engineers for finite element analysis of rubber material. Before simulation, simple, biaxial and planar extension tests are always done to get the model parameters. In this paper, we compare these two hyperelastic models with experimental data produced under simple, biaxial extension and planar extension loading conditions. The ability of the two models to reproduce different deformation modes is analyzed. Both material parameters and the stretch range of validity of each model are determined.
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Authors: Ming Li, Hui Ming Zheng, Luo Xia, Liu Yang
Abstract: In this paper, the boundary condition on free vibration of cantilever single-walled carbon nanotubes (SWCNTs) with Winkler elastic medium is investigated. The Euler beam theory with nonlocal elasticity is modeled as SWCNT. The analytical solution is derived and the numerical results show that the additional boundary conditions from small scale do not change natural frequencies. The reason is that the additional work made by the moment and shear force at the free end from small scale effect cancel each other, the boundary conditions due to local elasticity and nonlocal elasticity are also equivalent. Thus for simplicity, one can apply the local boundary condition to replace the small scale boundary condition.
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Authors: Fu Ping Wang, Cheng Jian Feng, Chen Xu, Kai Xiao, Yong Min Yu, Zhi Yong Yin
Abstract: Using a plastic material model to assess the injury energy of liver, the material must have excellent plastic deformation and with high-accuracy relationship between impact energy and deformation. In this paper we prepared a plastic material which composited of potassium stearate, paraffin liquid and novolac epoxy resin (F-51) with weight ratio 0.78/0.22/0.04. The elastic modulus values (Automatic young's) and yield stress data (yield strain 2%) were 54.44 MPa and 0.04185 MPa, measured by the Instron-8071. The deformation increased with impact energy obviously in impact experiment, we fit data with both an exponential curve and a second-order polynomial curve, the formulas were E=3.84687*e^(0.07476*Delta V)-3.20572and E=0.02428*(Delta V)^2+0.14718*Delta V+0.9778, the correlation coefficients were R^2=0.9510 and R^2=0.9544, respectively. These results indicated that the impact energy can be calculated from deformation, and the plastic material could be made a better model for assessing the injury energy of liver.
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Authors: Ri Hong Zhang, Jun Xia Shi, Ji Wen Hu
Abstract: The design of pneumatic cylinder seals is in accordance with the theory of fluid elastic tight seal. The sealing mechanism depends on the contact force which is created by the interference of initial elastic seal assembly and the sealing force which is created by the working fluid acting on the elastomeric material. In the high-speed pneumatic cylinder, the buffer structure enables the piston decelerates rapidly and stops stably. When the buffer stage begins, it will produce a strong dynamic contact between the cushion seals and the cushion spear. After the failure of cushion seals happen,the buffering capacity will be declined sharply. Therefore, the mechanical properties analysis of the cushion seals becomes very important. The material characteristics and the magnitude of interference of the cushion seals as well as the operating speed of the cylinder piston have a large impact on the life of the cushion seals. In this paper, based on the finite element analysis software ABAQUS, it provides certain reference value for the cushion seals material selection and structural parameters.
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