scholarly journals A finite-element mechanical contact model based on Mindlin–Reissner shell theory for a three-dimensional human body and garment

2011 ◽  
Vol 236 (5) ◽  
pp. 867-877 ◽  
Author(s):  
Ruomei Wang ◽  
Yu Liu ◽  
Xiaonan Luo ◽  
Yi Li ◽  
Shuai Ji
2014 ◽  
Vol 51 (2) ◽  
pp. 196-207 ◽  
Author(s):  
Tamer M. Elshimi ◽  
Richard W.I. Brachman ◽  
Ian D. Moore

Long-span metal culverts have been used for almost 50 years as an economical alternative to short-span bridges. Current design methods are based on two-dimensional finite element analysis using beam theory to represent the structure, or three-dimensional analysis employing orthotropic shell theory. However, neither analysis has been used to investigate the most critical position for trucks at the surface of long-span metal culverts. This paper shows results of three-dimensional finite element analysis, employing orthotropic shell theory and explicitly modeling the geometry of corrugated plates for a specific box culvert tested using a fully loaded dump truck. The analysis was then extended to study the effect of truck position on the response of long-span box and arch culverts. The finite element models, employing orthotropic shell theory and explicitly modeling the geometry of corrugated plates, successfully produced the behaviour of the culvert under truck loading for different truck positions. Culvert deformations were calculated within 7%–13% of the measured values at different locations. The bending moment at the crown was within 4%–17% of the values calculated using the measured strains. If three-dimensional finite element analysis is used to design these culverts, two design trucks should be considered (current design considers a single design truck). The highest moment or thrust is obtained when the truck tandem axles are located above the crown of the culvert.


2013 ◽  
Vol 56 (6) ◽  
pp. 1909-1923 ◽  
Author(s):  
Mohammad Ali Nazari ◽  
Pascal Perrier ◽  
Yohan Payan

Purpose The authors aimed to design a distributed lambda model (DLM), which is well adapted to implement three-dimensional (3-D), finite-element descriptions of muscles. Method A muscle element model was designed. Its stress–strain relationships included the active force–length characteristics of the λ model along the muscle fibers, together with the passive properties of muscle tissues in the 3-D space. The muscle element was first assessed using simple geometrical representations of muscles in the form of rectangular bars. It was then included in a 3-D face model, and its impact on lip protrusion was compared with the impact of a Hill-type muscle model. Results The force–length characteristic associated with the muscle elements matched well with the invariant characteristics of the λ model. The impact of the passive properties was assessed. Isometric force variation and isotonic displacements were modeled. The comparison with a Hill-type model revealed strong similarities in terms of global stress and strain. Conclusion The DLM accounted for the characteristics of the λ model. Biomechanically, no clear differences were found between the DLM and a Hill-type model. Accurate evaluations of the λ model, based on the comparison between data and simulations, are now possible with 3-D biomechanical descriptions of the speech articulators because of the DLM.


2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Feikai Zhang ◽  
Jianhua Liu ◽  
Xiaoyu Ding ◽  
Zhimeng Yang

Surface topography of sealing interface is a key factor affecting sealing performance. In industry, it has always been desirable to optimize the performance of static seals by optimizing the surface topography. The evolution of leak channels and the quantitative effects of surface topography on leak rates are expected to be clarified. This paper proposes a novel approach to calculate leak channels and leak rates between sealing surfaces for specific surface topographies, based on three-dimensional (3D) finite-element contact analysis. First, a macromechanical analysis of the entire sealing structure is conducted to calculate the interfacial pressure. Second, the surface topography data are measured and processed. Third, the interfacial pressure is used as the boundary condition applied on the microscale 3D finite-element contact model, which is built based on the specific surface topography. Fourth, the geometrical models of leak channels are extracted from the finite-element contact model, and the leak rates are calculated using the computational fluid dynamics (CFD) method. The proposed approach was applied to a hollow bolt-sealing structure. Finally, experimental results verified the accuracy and effectiveness of the proposed approach, which can provide valuable information for optimizing surface processing techniques, surface topography, and static seal performance.


Author(s):  
Mitsuhiro Hayase ◽  
◽  
Susumu Shimada ◽  

We propose a new model-based recognition method that involves the use of three-dimensional (3D) ellipsoidal models in various sizes and proportions as well as their two-dimensional (2D) appearance models. Most model-based vision is intended to recognize specified objects, and the model is specific to the object. However, our method can recognize various proportions of objects and was applied in posture estimation of the human body from thermal images.


1984 ◽  
Vol 51 (1) ◽  
pp. 206-207
Author(s):  
E. H. Mansfield

The complexity of shell analysis stems from the fact that loads are resisted, in general, by both membrane and flexural action. There is a need to develop a suitable shell finite element, but many of those proposed at the present time fail in the context of the “sensitive solutions” coupled with rigid body movements. These “sensitive solutions” refer to known solutions (within the framework of shell theory) of problem in which it is kinematically possible for the shell to deform with no straining of the midsurface. (Purely inextensional solutions were first considered by Lord Rayleigh [1].) In two cases, namely the torsion of a slit cylinder and the application of uniformly distributed moments Mθ and Mx = vMθ to a slit cylinder, the contribution of the membrane forces is identically zero. The second of these two cases is too trivial to be used for comparison with finite element solutions, but the first case exhibits many of the features that current finite elements have difficulty in reproducing. An exact solution within the context of shell theory is not necessarily, of course, an exact three-dimensional solution. However, the torsion of a slit cylinder has also been solved three-dimensionally (Love [2]) and the present Note focuses attention on the exact variation of shear stress through the wall of the shell and on how this compares with shell theory.


2017 ◽  
Vol 3 (3) ◽  
pp. 64-78
Author(s):  
Igor G Emel’yanov ◽  
Alexey V Kuznetsov

Introduction. With the development of numerical methods and computational complexes, it is quite easy to evaluate the stress state of thin-walled structures in the form of rotation bodies. However, when solving such problems by the finite element method, it is necessary to choose such finite element grid to "grasp" all possible singularities of the stressed state. To correctly take them into account, you must reduce the size of the finite elements. Reducing the size of the elements leads to an increase in the required computing power. Formulation of the problem. When solving applied problems, even with a sufficiently coarse grid, the number of elements can exceed hundreds of thousands. When solving problems for real constructions in a three-dimensional setting, the amount of computation can be quite large and not every supercomputer can even handle such a solution. Objective. The purpose of this paper is to use the well-known approach used in shell theory, which allows us to reduce the three-dimensional problem to the solution of a onedimensional problem, which substantially reduces the requirements for computing power. Method (methodology). The problem of determining the stress state of shell structures in the form of bodies of revolution is considered. The approach is based on the integration of the equations of the theory of shells and the expansion of functions into Fourier series for separation of variables. The expansion into a discrete Fourier series in cosines and sines is used in this paper, which describes arbitrary asymmetric mechanical loads. Results. A thin-walled cylindrical structure hinged at the ends is considered. The structure is loaded in three places by a distributed force acting normal to the surface of the shell. After integrating the system of equations for the shell, the found stress-strain state of the shell is determined by the stress components on the outer and inner surfaces of the shell and the displacement components. The paper compares the calculation results with the proposed methodology and the finite element method. The conclusion. It is shown that the use of methods of shell theory, and the proposed expansion of resolving functions and loads in a Fourier series, allows solving problems using small computing resources. At the same time, the necessary accuracy of calculation for all components of the stress-strain state of the structure is ensured.


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