Papers by Keyword: Stiffness

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Authors: Zhao Qun Du, Tian Xian Zhou, Gang Zheng, Wei Dong Yu
Abstract: The two well known systems for measuring stiffness handle of fabrics are KES-FB and FAST both consisting of four meters, whose testing principles are multiple mechanical properties through multiple tests. It is expensive, time-consuming and no in-situ. The multiple properties through single test in principle is up-to-date technology of measurement science, which is an assembled measuring technology in-situ and measure multiple functions on the same part of a sample. The corresponding apparatus was developed for measuring weight, bending, friction, tensile/shearing and compression behaviour of yarns and fabrics (CHES-FY) and also for stiffness handle evaluation. The paper just presented the bending model, and the comparisons between characteristics including bending rigidity and stiffness from the pulling-out force and distance curve and results by KES-F & FAST systems were conducted. Conclusions showed high correlations and indicates the approach by CHES-FY be feasible and accurate in measuring bending rigidity and stiffness handle.
Authors: Cosmin Mihai Miriţoiu, Dumitru Bolcu, Marius Marinel Stănescu, Rosca Vîlcu, Dan Ilincioiu
Abstract: There were built some new original composite sandwich bars with polypropylene honeycomb core and the exterior layers of the bars were made of epoxy resin reinforced with steel wire mesh. For these composite bars, there were determined the stiffness by using two different experimental methods: variant 1- using the Walter-Bai testing machine and variant 2- using the eigenfrequency of the first eigenmode. The errors between these two methods were determined. In the next stage of the paper, some metallic beams, equivalent from the stiffness point of view with the composite ones, were considered. Comparisons between them, from the mass per unit length point of view, were made.
Authors: De Bin Zhu, Xiao Jun Cao, Ya Shuang Bai, Qing Wen Zhang
Abstract: Castellated beam is a kind of holed web plate structural beam, since it has many advantages: savings in steel, light self-weight, resists bending and easy to deploy, the application of this structural beam becomes more and more widely. Due to its weakened web plate, castellated beam would be affected by shear effects greatly. The deformation of components increased under the affects of external loads. Therefore, in order to improve the accuracy of finite element analysis model, by consideration of the shearing effects and the bending stiffness affected under opened structure, this issue made improvement based on the theory of curved beams. By compare the results from this issue and the result from the analytical model of shell elements; we verify the feasibility of this method.
Authors: Ludmila Fridrichová
Abstract: The article is dealing with the principle of measuring bending rigidity by the method of Cantilever test which is suitable for measuring different types of textile and also non-textile materials. The authors are presenting a modification of the device and a simple method for calculation bending rigidity. It is a method by means of which bending rigidity, in extreme conditions - high temperature and humidity of the air-can be measured. In the discussion, the authors are pointing out the advantages and difficulties of this method of measuring.
Authors: A. Albers, H. Weiler, D. Emmrich, B. Lauber
Abstract: Beads are a widespread technology for reinforcing sheet metal structures, because they can be applied without any additional manufacturing effort and without significant weight increase. The two main applications of bead technology are to increase the stiffness for static loading conditions and to reduce the noise and vibrations for dynamic loadings. However, it is difficult to design the bead patterns of sheet metal structures due to the direction-controlled reinforcement effect of the beads. A wrong bead pattern layout can even weaken the properties of the structure. In the past, the designs were predominantly determined empirically or by the use of so called bead catalogues. Recently, different optimization approaches for bead patterns were developed, which are based upon classical mathematical programming optimization algorithms together with automatically generated shape basis vectors. However, these approaches usually provide only vague suggestions for the designs. One of the most severe difficulty with these approaches is to transfer the optimized results into manufacturable designs. Furthermore, another severe difficulty is that the optimization problem is non-convex, which frequently leads the mathematical programming algorithms into a local optima and thus to sub-optimal solutions. The investigations in this article show an optimization method, which within a few iterations leads to bead structures with excellent reinforcement effects using optimality criteria based approach. Generally, the results can be transferred without large effort into a final design. The new optimization method calculates the distribution of the bending stress tensor and the principal bending stresses based upon the results of a finite element analysis. The bead orientations are calculated by the trajectories of the principal bending stress with the largest magnitude. The beads are projected on to the mesh of the component using geometric form functions of the desired bead cross section. A local bead ratio of 50% (defined as average area of the beads in relation to total area of the sheet) is used by the algorithm to determine the maximum moment of inertia. The proposed algorithm is numerical implemented in the optimization system TOSCA and available for being applied with the following finite element solvers: ABAQUS, ANSYS, I-DEAS, NX Nastran, MSC.Nastran, MSC.Marc and PERMAS. The optimization algorithm is successfully applied to static and dynamic real world problems like car body parts, oil pans and exhaust mufflers. In the present work several academic and industrial examples are presented.
Authors: Yi Li, Bo Sun, Wen Zhao
Abstract: An accelerating calculation of reliability analysis on strength and stiffness for frame structure was derived. The method of numerical analysis was combined with recurrence formula, to generatelimit state function of continual variational structure. This methodcan simplify the algorithm for identifying systemic dominant failure modes, because the repeated assembly of global stiffness matrix and repeated inverse matrix operation in analysis are avoided. A new criterion of degenerating the structure into mechanism is introduced. Continual analysis of variational structure can be realized.
Authors: Hai Tao Liu, Zhi Yu Wen, Zheng Guo Shang, Li Chen
Abstract: The finite element method to obtain the stiffness of MEMS (Micro-Electro-Mechanical Systems) accelerometer is difficult to give an exact expression, so a new method to analyze the stiffness of MEMS accelerometer was purposed. Both Mechanics and electricity analysis were used to calculate the stiffness of vacuum microelectronic accelerometer developed in our laboratory, and the control and detection circuits were design according to the result. Finally, the sensitivity, linearity and other performance were measured through the static gravitational field experiments; the least squares curve fitting correlation coefficient 0.9999 and linear 0.9%. The result shows that this method to analyze the stiffness of the stiffness of vacuum microelectronics accelerometer is correct and feasible, and this method can also be applied to other MEMS accelerometer with symmetrical structure and electrostatic force balance mode.
Authors: Cheng Chen, Zheng Ming Zhou
Abstract: Soils have nonlinear stiffness and develops irrecoverable strains even at very small strain levels. Accurate modeling of stress-strain behaviour at various strain levels is very important for predicting the deformation of soils. Some existing stress-strain models are reviewed and evaluated firstly. And then a new simple non-linear stress-strain model is proposed. Four undetermined parameters involved in the proposed model can be obtained through maximum Young’s module, deformation module, and limit deviator stress and linearity index of soils that can be measured from experiment directly or calculated by empirical formulas indirectly. The effectiveness of the proposed stress-strain model is examined by predicting stress-strain curves measured in plane-strain compression test on Toyota sand and undrained triaxial compression test on London clay. The fitting results of the proposed model are in good agreement with experimental data, which verify the effectiveness of the model.
Authors: Da Chang Zhu, Qi Hua Gu, Liang Wang, Fan Xiao
Abstract: A novel type of 4-RPUR spatial compliant parallel manipulator which named whole compliant parallel manipulator (WCPM) is presented in this paper. Compared with traditional design method, a novel 4-RPUR type spatial compliant parallel manipulator which satisfy the geometrical constraint conditions in spatial is proposed. By using ANSYS software, the proposed two kinds of compliant parallel manipulator are analyzed. The effectiveness of the proposed method is verified by simulation and experiments.
Authors: Fang Jia, Fan Cheng Zhang
Abstract: In present study, the mechanical properties of disc-spring vibration isolator with viscous dampers is investigated by finite element analysis (FEA) and experiments. The result of FEA and static test reveals that frictional damping has significant effect on the static stiffness of combination vibration isolator, the ability to strengthen loading stiffness and lower unloading stiffness. However viscous damper has no effect on the static mechanical properties. The dynamic experiment shows that the dynamic performance of combination vibration isolator can be greatly improved with viscous dampers. Viscous dampers have little effect on dynamic stiffness of vibration isolator, but significant effect on damping characteristics. These conclusions are of significant importance in the analysis and design of combination disc-spring vibration isolators.
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