Ma N.,JSOL Corporation |
Takada K.,Honda Corporation |
Sato K.,Jfe Holdings
Procedia Engineering | Year: 2014
To estimate the strength of automotive bodies under impact loading and to predict the crack occurrence of high strength steel sheets, the local fracture strain and the ductile damage limit must be measured by experiments to provide data for metal forming simulation by using FEM. In the present study, the local strains at the cracking position and its nonlinear strain path during a simple uniaxial tensile test were measured using a digital image grid method developed by authors. Then, a new identification method for the ductile damage limit of steel sheets was proposed with the aid of the measured nonlinear local strain historical path and local fracture strain. By changing the grid pitch length of the digital image grid method, the effect of grid pitch length on the measured local fracture strain and ductile damage limit were investigated. This experimental investigation is very useful to predict the fracture occurrence conditions if various sizes of finite element mesh were employed in the simulation. The ductile damage limit identified by the newly proposed method using a simple uniaxial tensile test agreed very well compared with the conventional press test. © 2014 The Authors. Published by Elsevier Ltd.
Ishinabe M.,Chubu University |
Hayashi K.,JSOL Corporation
Strength of Materials | Year: 2012
Elastic buckling, which occurs in shell structures, is a major design issue because it can cause failures of structures. In particular, the variation in buckling load caused by a decrease in the thickness of the walls of structures is a key issue for safe design. The arc-length method, which is a finite element method, is generally applied to solve this type of problem. However, it has been reported that there are some cases in which the path of the buckling load cannot be solved using this method. We verified the problem by applying the arc-length method to elastic buckling that occurs in a shallow partial spherical shell. To solve the problem, we formulated a novel algorithm used in the explicit finite element method for estimating minimum strength of thin-walled structures. In this algorithm, initial deformation is given by pressing a rigid wall to the vertical direction of buckling mode. We anticipate that the proposed method will prove to be a practical way of calculating the minimum load for partial elastic buckling that occurs in a general shell structure under pressure. © 2012 Springer Science+Business Media, Inc.
Ichinose N.,JSOL Corporation |
Ishikawa M.,Yamagata University |
Morimoto K.,Sekisui Seikei Ltd.
Polymer Composites | Year: 2011
Thanks to their lightweight properties, formability and low cost, polymers have become an essential material for manufactured products. To improve the mechanical properties, almost all polymers are blended with some kind of fiber made from glass, carbon, organic or natural material. The importance of interfacial strength between matrix and fiber is a well known requirement for effective mechanical properties and some experimental results indicate that low interfacial strength helps increase the toughness of composites. In this paper, models of composite reinforced by fiber aligned with maximum principal stress under uni-tensile loading are simulated. Based on the simulation result, we discuss the effect of interfacial strength, aspect ratio of fiber and friction force between matrix and fiber on stable deformation and provide the guidelines for establishing composites with high modulus and toughness. © 2011 Society of Plastics Engineers.
Ma N.,Osaka University |
Ma N.,JSOL Corporation
International Journal of Advanced Manufacturing Technology | Year: 2016
To simulate welding induced transient thermal stress and deformation of large scale FE models, an accelerated explicit method (ACEXP) and graphical processing units (GPU) parallel computing program of the finite element method (FEM) were developed. In the accelerated explicit method, a two-stage computation scheme is employed. The first computation stage is based on a dynamic explicit method considering the characteristics of the welding mechanical process by controlling both the temperature increment and time scaling parameter. In the second computation stage, a static equilibrium computation scheme is implemented after dynamic thermal loading to obtain a static solution of transient thermal stress and welding deformation. It has been demonstrated that the developed GPU parallel computing program has a good scalability for large-scale models of more than 20 million degrees of freedom. The validity of the accelerated explicit method is verified by comparing the transient thermal stress and deformation with those computed by an implicit FEM. Finally, welding deformation and residual stress in a structure model assembled from nine high-strength steel plates and 26 weld lines were efficiently analyzed by ACEXP and GPU parallel computing within 45 h. The computed welding deformation agreed well with measured results, and a good accuracy was obtained. © 2016 Springer-Verlag London
Kitaoka H.,JSOL Corporation
Respirology | Year: 2011
Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity; however, it is unclear which components in the respiratory system generate the frequency dependence. The author constructed a 4D pulmonary lobule model and analysed relationships between airflow rate, pressure and airway resistance by the use of computational fluid dynamics. Methods: The lobule model contained bifurcated bronchioles with two adjacent acini in which deformable inter-acinar septa and alveolar duct walls were designed. Constrictive conditions of respective bronchioles were designed, too. 4D finite element models for computational fluid dynamics were generated and airflow simulations were performed under moving boundary conditions of the arbitrary Lagrangean-Eulerean method. From the simulation results, airway resistances for various conditions were calculated. Results: Tissue resistance emerged under the condition of different acinar pressures caused by unequal airway resistances. If the inter-acinar septum was shifted so as to cancel the pressure difference, the acinar pressures were equal in spite of unequal airway resistances, and hence, tissue resistances did not emerge. Therefore, the tissue resistance in the former case is thought to be an index of alveolar pressure inequality (which could be cancelled by mechanical interaction of lung parenchyma), rather than a material property of the tissue itself. Conclusions: Inequality of alveolar pressure decreases as the input oscillatory frequency increases. Therefore, frequency dependence of the respiratory resistance should be regarded as a conditional index of the alveolar pressure inequality caused by heterogeneous changes in the intra-pulmonary airway and/or the lung parenchyma. © 2011 The Author Respirology © 2011 Asian Pacific Society of Respirology.
Kitaoka H.,JSOL Corporation |
Cok S.,JSOL Corporation
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2013
Adventitious lung sounds in pulmonary emphysema, wheezes, are continuous musical sounds during expiration with 400 Hz or more. The textbook tells that expiratory airflow limitation in emphysema occurs at the peripheral airways and that wheezes are generated there. We have recently proposed a novel hypothesis based on image analysis and theoretical consideration that expiratory airflow limitation in emphysema occurs at the intra-mediastinal airway (trachea, main bronchi, and right lobar bronchi) due to compression by overinflated lungs. We performed expiratory airflow simulation by the use of a 4D finite element lung model, and found periodical vortex release with 300-900Hz at the end of protrusion of the the tracheal posterior wall. Relationship between the peak frequency of pressure fluctuation and airflow velocity was in agreement with Strahal's law either in normal or emphysematous condition. Contrarily, airflow simulation in a small bronchus (1.5 mm in diameter) indicated no apparent periodic vortex release. © 2013 IEEE.
JSOL Corporation | Date: 2013-05-29
Computer software for use in magnetic field analysis, electromagnetic wave analysis, thermal analysis, electric field analysis, structural analysis and combinations thereof; computers.
JSOL Corporation | Date: 2014-03-04
Kitaoka H.,JSOL Corporation
Japanese Journal of Clinical Radiology | Year: 2014
In order to understand interactions between small airways and alveoli in emphysema, the author performed 4D simulation of the acinar structure during progression of the emphysema. I assumed that the loss of elastin fibers at the alveolar mouth causes alveolar enlargement and then the over-stretch of the alveolar wall causes its rupture and degeneration. I also assumed that the air-supplying bronchiole is enlarged due to over-stretch of the inter-acinar connective tissue and that a bronchiole of an intact acinus is narrowed due to compression of surrounding enlarged air space. Obtained cross sectional images were similar to real histologic findings.
Jsol Corporation | Date: 2011-12-06
A simulation apparatus is provided with means for obtaining shape data expressing a simulation object, means for storing a constraint condition for a simulation in association with each type of object, means for storing, for each of one or more evaluation items for evaluating an object having an arbitrary shape satisfying the constraint condition, a procedure of a coupled analysis using one or more simulation means related to the evaluation item, means for accepting a type and an evaluation item for an object, means for reading out a procedure of a coupled analysis corresponding to the evaluation item based on the accepted evaluation item for the object, and means for reading out a constraint condition for an object corresponding to the accepted type and giving the constraint condition to the shape data to execute the coupled analysis in accordance with the procedure of the coupled analysis.