SIMPLE CONSTITUTIVE EQUATIONS FOR BRITTLE ROCKS, BASED ON STRAIN-DEPENDENT STIFFNESS

1998 ◽  
pp. 186-193
Author(s):  
Y. FUJII ◽  
Y. ISHIJIMA
2014 ◽  
Vol 783-786 ◽  
pp. 2136-2141
Author(s):  
Manuel Carsí ◽  
Victor Gutiérrez ◽  
Ignacio Rieiro ◽  
Esther Benavente ◽  
Oscar A. Ruano

The improvement of optimization numerical methods for constitutive equations has been the first aim of this research. A subordinate optimization algorithm, based on Newton method, through “ad hoc” assessment, has been developed. Application to hot torsion data of AISI4145 with two grain sizes has been carried out. It is concluded that the Newton method is an excellent algorithm for the optimization of strain dependent constitutive equations. Two models are presented as alternative to the generalized Garofalo model: the normalized stress exponent model (NSE) and the Generalized Sherby model (SG). The NSE model is the most precise to restitute the experimental stress-strain curves.


Author(s):  
Guzide Satir Basaran ◽  
Yagut Akbarova ◽  
Kezban Korkmaz ◽  
Kursad Unluhizarci ◽  
Francois Cuzin ◽  
...  

2003 ◽  
Vol 775 ◽  
Author(s):  
Byeongchan Lee ◽  
Kyeongjae Cho

AbstractWe investigate the surface kinetics of Pt using the extended embedded-atom method, an extension of the embedded-atom method with additional degrees of freedom to include the nonbulk data from lower-coordinated systems as well as the bulk properties. The surface energies of the clean Pt (111) and Pt (100) surfaces are found to be 0.13 eV and 0.147 eV respectively, in excellent agreement with experiment. The Pt on Pt (111) adatom diffusion barrier is found to be 0.38 eV and predicted to be strongly strain-dependent, indicating that, in the compressive domain, adatoms are unstable and the diffusion barrier is lower; the nucleation occurs in the tensile domain. In addition, the dissociation barrier from the dimer configuration is found to be 0.82 eV. Therefore, we expect that atoms, once coalesced, are unlikely to dissociate into single adatoms. This essentially tells that by changing the applied strain, we can control the patterning of nanostructures on the metal surface.


2007 ◽  
Vol 35 (4) ◽  
pp. 276-299 ◽  
Author(s):  
J. C. Cho ◽  
B. C. Jung

Abstract Tread pattern wear is predicted by using an explicit finite element model (FEM) and compared with the indoor drum test results under a set of actual driving conditions. One pattern is used to determine the wear rate equation, which is composed of slip velocity and tangential stress under a single driving condition. Two other patterns with the same size (225/45ZR17) and profile are used to be simulated and compared with the indoor wear test results under the actual driving conditions. As a study on the rubber wear rate equation, trial wear rates are assumed by several constitutive equations and each trial wear rate is integrated along time to yield the total accumulated wear under a selected single cornering condition. The trial constitutive equations are defined by independently varying each exponent of slip velocity and tangential stress. The integrated results are compared with the indoor test results, and the best matching constitutive equation for wear is selected for the following wear simulation of two other patterns under actual driving conditions. Tens of thousands of driving conditions of a tire are categorized into a small number of simplified conditions by a suggested simplification procedure which considers the driving condition frequency and weighting function. Both of these simplified conditions and the original actual conditions are tested on the indoor drum test machines. The two results can be regarded to be in good agreement if the deviation that exists in the data is mainly due to the difference in the test velocity. Therefore, the simplification procedure is justified. By applying the selected wear rate equation and the simplified driving conditions to the explicit FEM simulation, the simulated wear results for the two patterns show good match with the actual indoor wear results.


1978 ◽  
Vol 18 (3) ◽  
pp. 85-95
Author(s):  
Hideo Sekiguchi

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