A Variable Resolution Global Model Based upon Fourier and Finite Element Representation

1989 ◽  
Vol 117 (3) ◽  
pp. 583-606 ◽  
Author(s):  
Jan Paegle
2012 ◽  
Vol 504-506 ◽  
pp. 673-678 ◽  
Author(s):  
Laurent Tabourot ◽  
Pascale Balland ◽  
Jonathan Raujol-Veillé ◽  
Mathieu Vautrot ◽  
Christophe Déprés ◽  
...  

As close as you watch them, the materials (especially metals) present discontinuities that can easily be qualified as strong. Dislocations, structures formed by these dislocations, phases and grains are all discontinuities, also sources of heterogeneity, with effects on material behavior that are not really well reproduced by a model based on a continuity assessment. Consequently, the materials should be considered as a set of compartments with different behaviors. This promotes an alternative way to define models. A coherent modeling process is probably the integration of the different behaviors of the material compartments within the global model. The objective is here to build an efficient elasto(visco)plastic model of the mechanical behavior of titanium combining compartmentalized behaviors. After setting the frame of the study, which is of primary importance, the proposed modeling process is running as follows (i) choose a local behavior, (ii) identify the parameters of crystalline texture that must be integrated into the simulation and (iii) finally formulate a way of combining local compartments behaviors. The intrinsic properties of Finite Element codes are used to achieve the integration of the whole system.


2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 59-72 ◽  
Author(s):  
Hasan Nagiar ◽  
Tasko Maneski ◽  
Vesna Milosevic-Mitic ◽  
Branka Gacesa ◽  
Nina Andjelic

Membrane walls are very important structural parts of water-tube boiler construction. Based on their specific geometry, one special type of finite element was defined to help model the global boiler construction. That is the element of reduced orthotropic plate with two thicknesses and two elasticity matrixes, for membrane and bending load separately. A global model of the boiler construction showed that the high value of stress is concentrated in plates of the buckstay system in boiler corners. Validation of the new finite element was done on the local model of the part of membrane wall and buckstay. A very precise model of tubes and flanges was compared to the model formed on the element of a reduced orthotropic plate. Pressure and thermal loads were discussed. Obtained results indicated that the defined finite element was quite favorable in the design and reconstruction of the boiler substructures such as a buckstay system.


1986 ◽  
Vol 71 ◽  
Author(s):  
I. Suni ◽  
M. Finetti ◽  
K. Grahn

AbstractA computer model based on the finite element method has been applied to evaluate the effect of the parasitic area between contact and diffusion edges on end resistance measurements in four terminal Kelvin resistor structures. The model is then applied to Al/Ti/n+ Si contacts and a value of contact resistivity of Qc = 1.8×10−7.Ωcm2 is derived. For comparison, the use of a self-aligned structure to avoid parasitic effects is presented and the first experimental results obtained on Al/Ti/n+Si and Al/CoSi2/n+Si contacts are shown and discussed.


2021 ◽  
Author(s):  
Wanyu Li ◽  
Jun Xu ◽  
Shunan Zhang ◽  
Han Guo ◽  
Jianqi Sun ◽  
...  

Abstract Background: As the gold standard for clinical osteoporosis diagnosis, bone mineral density has significant limitations in bone strength assessment and fracture risk prediction. The purpose of this study is to explore a new osteoporotic bone quality evaluation criteria from both diagnosis site selection and bone strength prediction. Methods: Ovariectomized rats with different intensity swimming therapy were investigated in this study. The lumbar vertebrae and femurs of all the rats were scanned by synchrotron radiation computed tomography. Bone microstructure analysis and finite element analysis were combined to obtain bone microstructure parameters and estimated bone strength. And the sensitivity of different skeletal sites to therapy was explored. An elastic network regression model was established to predict bone strength by integrating additional bone microstructure characteristics besides bone mass.Results: Histomorphometry analysis showed that swimming therapy could reduce the risk of osteoporosis of lumbar vertebrae and femur and suggested that the femur might be a more suitable site for osteoporosis diagnosis and efficacy evaluation than the lumbar vertebrae. The average coefficient of determination and average root mean squared error of our predictive model were 0.774 and 0.110. Bland-Altman analysis showed that our model could be a good alternative to the finite element method. Conclusions: The present study developed a machine learning model for prediction of bone strength of osteoporosis model based on synchrotron x-ray imaging and demonstrated that different skeletal sites had different sensitivity to therapy, which is of great significance for the early diagnosis of osteoporosis, the prevention of fractures and the monitoring of therapy.


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