Evaluation of the intervertebral joint force in vivo is very important for clinical spine problems, for example, spinal instability, disorder of intervertebral disc, compressive fracture of osteoporotic vertebra, etc. Direct measurement of the joint force is difficult to get permission, so computational method to calculate the force is expected. Spine structure is mainly constructed of many vertebrae and flexible intervertebral disks, and it is unstable by itself under standing condition. Supporting by erector muscles and ligaments keep the spine standing condition, so that loading condition of each vertebra depend on the muscle and ligament forces. Biomechanical analysis of musculoskeletal system taking into account of large number of muscle and ligament forces is necessary to determine the intervertebral joint force. Commercial software to deal with the musculoskeletal system is available nowadays, and it has been applied to clinical, ergonomic or sport biomechanics problem.Surgery of spinal fixation is frequently operated for instability or disorder of intervertebral joints. Although stability of the joints is recovered and nervous symptom related with the disorder joints is relieved, additional trouble at adjoining joints with the fixation is concerned because excessive rigidity and posture change by the fixation makes load of the adjoining joints increase. It is required to evaluate the change of adjoining joint force by the fixation, to prevent additional trouble in advance. In this study, analysis of intervertebral joint force and muscle force was performed in the case with or without spinal fixation using full body musculoskeletal model developed by the AnyBody Modeling System (AnyBody Technology). The joint and muscle forces were evaluated under various posture of flexion and extension. Then influence of the spinal fixation on the intervertebral joint force at adjoining joints with the fixation was discussed.

Mechanical stress analysis of vertebral bone is required to determine compressive strength of vertebra for osteoporosis patients in clinical situation of orthopedics. Stress occurred in vertebrae depend on condition of musculoskeletal system of spine. Spine structure is mainly constructed of many vertebrae and flexible intervertebral disks, and it is unstable by itself under standing condition. Supporting by erector muscles and ligaments keep the spine standing condition, so that loading condition of each vertebra depend on the muscle and ligament forces. Biomechanical simulation of musculoskeletal model taking into account of muscle and ligament forces and intervertebral joint forces is necessary to determine the loading condition for vertebral stress analysis. Commercial software to deal with the musculoskeletal system, e.g. AnyBody Modeling System (AnyBody Technology Inc.), Is available nowadays, and it has been applied to clinical, ergonomic or sport biomechanics problem.Spine kyphosis is often caused by compression fracture of osteoporotic vertebra, because shape of the fractured vertebra is sphenoidal with sharp anterior side of vertebral body. Spine kyphosis makes gravity center of trunk shift to anterior side, and then intervertebral joint moment due to trunk weight increase. Additional compression fracture is concerned at adjoining vertebrae to the fractured one in the kyphotic spine. In this study, musculoskeletal simulation model with spine kyphosis was created by using AnyBody Modeling System considering compensation posture due to kyphosis. Kyphosis patient used to have compensation posture to recover body balance and face up. Intervertebral joint forces and muscle forces of the model were computed, and then influence of the kyphosis on the intervertebral joint force at adjoining joints was discussed comparing between kyphosis and intact model. Furthermore, influence of the compensation posture on muscle forces related to spine was considered.

Some aspects of the early collapse biomechanics of the segmentally necrotic adult human femoral head were studied, using a small-deformation plane strain, elasto-plastic finite element model. The computational procedure used was based upon the initial stress technique, and permitted study of stress and strain fields and of the progression of failure regions as a function of incrementally applied joint loads. The results consistently demonstrated both subchondral and deep cancellous failure patterns similar to those seen clinically. There was a clear distinction, however, between these two failure regimes, dependent primarily upon the relative strength deficits input for the subchondral versus the deep cancellous regions. Usually, the failure zone was appreciable only at significantly supra-physiological loads, reflecting the likely importance of fatigue events in the clinical collapse process. Although subchondral failure was always limited to the entire base region of the infarction wedge, the zones of deep failure varied considerably with changes in lesion geometry, usually being concentrated within the infarct near the underlying necrotic/viable interface.

Osteoporosis causes frequently bone compressive fracture at the vertebrae. Drug therapy is often treated in clinic to strengthen osteoporosis vertebra and prevent fracture. It is important to evaluate mechanical strength and betterment of bone fracture risk of vertebra in the treatment process. Patient-specific mechanical analysis is necessary to estimate bone fracture risk. In this study, patient specific finite-element models of osteoporosis vertebra based on CT images were obtained considering individual bone shape, cortical thickness and bone density distribution. Bone fracture analysis of the osteoporosis vertebrae undergoing drug treatment were performed over time, for 4 patients to estimate the therapy effect to mechanical strength recovery of vertebrae.

In this paper, we propose a new method to produce the functional continuum, It is a topological optimization technique based on a function of the continuum and composed of three steps. In the first step, an initial mechanism model, which conforms the given function is determined, using only some levers and supports. The mechanism model is changed to a framed structure as the Rahmen model in the second step, The cross section and length of members in the framed structure are optimized to maintain the original design requirement. In the final step, the framed structure is changed to the functional continuum using some well known shape optimization techniques. Two examples of application of this technique for the functional continuum are presented.

Cellular Automata(CA) are examples of dynamical systems which exhibit"self organizing"behavior with increasing time. They are useful in modeling modular systems. One such application of modularity is described in this paper where a structural plate is considered as composed of smaller"structural modules"which are considered as cells in a lattice of sites in a CA and have discrete values updated in discrete time steps according to local rules. These local rules are generally fixed in a CA, but we consider these rules as evolvable. To evolve the local rules, we use the Genetic Algorithm(GA) model. In this paper, two structural optimization methods by Evolutionary Cellular Automata(ECA) are presented. ECA is a Cellular Automata(CA) which is optimized for computation of certain problems by the Genetic Algorithm(GA). The first method is called"Direct Rule Encoding"and the other is called"Indirect Rule Encoding". Direct Rule uses configuration of the neighborhood state as the CA's input. Indirect Rule uses the"Ratio"between given cells' stress and sum of neighborhood stresses. These two methods are applied to minimize weight design problems and adaptive solutions are obtained From this experiment, we observe that Indirect Rule is effective in large scale problems.

A special finite-element method for multiple laminated structure, previously proposed by the authors, is presented here. It can provide attractive results without three-dimensional finite-element discretization and can be applied to electronic packaging problems. The thermal stress analysis of the basic IC model, the practical IC model with lead fingers and the electronic printed board with solder bump joints are selected as the problems to deal with, and analyzed in detail.From the results of the basic IC model, the influences of varying chip size and package thickness for the stress distributions, are presented. The causes of failure for the real IC device are presented from the results of the practical IC model. In addition, influences of the solder joint arrangements for the thermal stresses are presented from the results of the electronic printed board with solder bump joints. (C) 1998 Elsevier Science B.V. All rights reserved.

An eggshell is cracked easily by an inside load, but has strong resistance to an outside load. In this study, the structural and material composition of an eggshell (from a hen's egg) is analyzed by microscopic observation, static and dynamic penetration tests and FEM. The results obtained are as follows. (1) From microscopic observation, the eggshell is found to have a laminated structure of many material compositions. (2) The outer eggshell membrane acts as a strong adhesive agent between the inner eggshell membrane and the eggshell. (3) A cone-type punch and striker makes an initial crack easily, but subsequently large penetration energies are required. (4) The penetration energy required from outside of an eggshell is larger than from inside because it includes the energies required to break the membrane and peel it off the eggshell.

This paper analyzes the impact fractures of a laminated glass with interlayered polyvinyl butyral (PVB) and a bi-layer laminated glass with PVB on one side, using the discrete element method (DEM). A laminated glass beam and a bi-layer laminated glass beam with both ends fixed are analyzed when impacted at the center by a cylindrical rigid body moving with a certain initial velocity. For the bilayer laminated glass beam, two analytical models are selected where the impact surfaces are the glass and PVB sheets. The DEM is applied to simulate the impact fracture behavior of three kinds of beam until penetration. From the numerical results, it is shown that the bi-layer type, laminated type and reverse bi-layer type have the maximal impact force in descending order. But penetration energies of laminated type and bi-layer type are similar. Based on the above observations, it can be concluded that the bi-layer laminated glass is safer than the laminated glass as the windscreen of automobiles.

In this study, a new computer simulation model of the bone remodeling adapting to mechanical environment by using the cellular automata is proposed. Finiteelements of FEM are further subdivided into smaller cells which are stated as bone tissue, bone cell or empty space. States of the cells are changed automatically by a set of rules as similar as bone remodeling rules. While the set of rules is changed due to stress level of each element, the bone density is changed adapting to the stress. Efficiency of the simulation model is demonstrated applying it to a bone remodeling problem of a human femoral head.

One of the most important problems in the design of press- and shrink-fitted assemblies is to avoid stress concentrations at the contact of two bodies. A method is presented whereby the contact-stresses can be made uniform by using variable interferences. In the proposed method the finite element technique is applied to determine the stresses of composite bodies, ignoring the effects of friction at the contact surfaces. A method of optimum structural design is used to obtain a uniform contact stress within the limit of the contraction force. In this method, interferences at contact nodal points are used as design variables. Some simple examples are presented and the effectiveness of the proposed approach is also demonstrated.

The influence of impact velocity and geometry in the fracture patterns produced by a concentrated impulse loading on brittle plates and cylindrical shells has been studied both experimentally and theoretically. The experiments were performed by impacting plates and cylindrical shells made of plaster with a steel ball. The fracture behavior was photographed by a camera with a flash. The crack-initiation time was measured using a memoriscope. The fracture behavior is explained using the theory of flexural motion of a plate and a cylindrical shell. With the addition of impact-fracture criteria to these theories, the fracture patterns of brittle plates and cylindrical shells are predicted and the resemblance is discussed.

Problems considered here are that of minimizing the weight of beams, which are subjected to a uniform bending moment and reinforced by the fibers distributed in the direction of beam axis. The beam is simplified as a multilaminate structure, of which the fiber volume percent Vfi of each lamina is considered as the design variables. To formulate this design problem the bending theory of multilaminate beam and the law of mixture for the composite material strength are applied. Furthermore, the sequential linear programming and the sequential unconstrianed minimization techniques are used to obtain the design solutions numerically.

The clamping effect of rail fastening systems in a travelling crane is studied by theoretical and experimental techniques. For the theoretical model, a model of a unit rail length with a pair of rail fasteners is first considered. The model was idealized to an equivalent spring system composed of many spring elements, and the stiffness constant was formulated. By using this model and the theory of a beam-on-an elastic foundation, the dynamical behavior of the practical rail model with many pairs of rail fasteners was theoretically analyzed. From the results, the changes of the clamping forces in the joint bolts and the rail displacements were obtained and were compared with the experimental values.

The influence of impact velocity and ring geometry in the fracture patterns produced by in-plane concentrated impulsive loading on brittle circular rings has been studied both experimentally and theoretically. The experiments were performed by impacting circular rings made of plaster with a steel plate. The fracture behavior was photographed by a camera with a flash, and the crack-initiation time was measured using a memoriscope. The fracture behavior is explained using dynamic photoelasticity and the theory of flexural motion of a circular ring. With the addition of an impact-fracture criterion to this theory, the fracture patterns of brittle circular rings are predicted.

The fracture patterns produced by concentrated impact loading on brittle beams and their dependence on the impact velocity and beam length has been determined. The experiment was performed using the transverse impact of a steel ball on the free end of cantilever beams made of plaster. The mechanism, location and time sequence of fracture were photographed by a camera connected to a stroboscope or with a high-speed framing camera. It was found experimentally that the concentrated impact loadings produce three characteristic fracture behaviors. Moreover, by using the dynamic photoelastic technique, the authors found it possible to explain theoretically the fracture behavior of this experiment by using the theory of flexural motion of a semi-infinite beam. Hence, applying an impact-fracture criterion to this theory, the fracture patterns of brittle beam can be estimated.

AbstractIn this paper, a procedure for obtaining a fully stresses shape of elastic continuum under arbitrary design conditions is proposed, by using the optimum distribution of the material properties such as the Young's modulus or the plate thickness. By using this technique, the optimum multiple‐connected shape can be created from the original shape of simply body. The optimum shape of a road‐pole subjected to an uniformly distributed load is determined by using the technique, and from the results the effectiveness of the technique is examined numerically.

はずみ車, ベルト車あるいは大経歯車などの有効な形状として用いられているスポーク付回転円板の強度的に最適な形状を, 有限要素法を利用した要素の形状変換法を基礎とした形状最適化法によって求め, 従来からの設計慣習などと比較検討し, 有用な設計指針を得た. さらにその形状に対し, レジンモルタルを用いて回転破壊試験を実施し, その有効性を確認した.