Proposal of a Method to Predict Grinding Stresses

2008 ◽  
Author(s):  
V. Boucly ◽  
D. Ne´lias
Keyword(s):  
Mechanical Model ◽  
Frictional Heating ◽  
Computing Time ◽  
Fretting Wear ◽  
Work Piece ◽  
Stress And Strain ◽  
The Finite Element Method ◽  
First Results ◽  
History Of ◽  
Grinding Tool

Residual stresses due to machining are the results of the thermo-mechanical history of the piece/tool interface. The magnitude and the gradient of stress play a key role for the surface integrity. A thermo-mechanical model has been developed. It allows simulating the rolling/sliding contact between an elastic tool in rotation along its own axis and an elastic-plastic flat in translation. The analysis includes the effects of both the normal and tangential loading. Frictional heating is also considered. The model is based on a semi-analytical method and the transient 3D contact problem is fully solved. Compared to the finite element method the computing time is reduced by several orders of magnitude. This technique has already been successfully applied to the simulation of running-in and wear, and to fretting wear, and a first attempt to simulate residual stress and strain due to the contact between a grinding tool and a work piece is made here. First results are presented for various stationary and transient thermo-mechanical loading histories.

Large Deformation Modeling Applied to the Sheet Metal Electromagnetic Forming

2008 ◽  
Author(s):  
C. Dumitras ◽  
I. Cozminca
Keyword(s):  
Finite Element ◽  
Deformation Process ◽  
Electromagnetic Forming ◽  
Stress And Strain ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Strain Fields ◽  
The Finite Element Analysis ◽  
History Of ◽  
Free Bulging

The electromagnetic forming has the advantage of a minimum forming time, but this is a major obstacle in determining the process’s history of the forming workpiece. Both experimental and theoretical known analysis methods for this process give a discret array of data (only for the displacements). One considers it is more adequate to use the finite element method in studying this process. The main advantage of the finite element analysis is given by the fact that it shows the stress and strain fields in a continuous way during the deformation process. Also, it offers a model from which one can predict the final shape of the part and the possible crack zones. One present a compared study of the experimental and the simulated results achieved of the free bulging aluminum specimens by electromagnetic impulses.

A Numerical Solution for Fretting Contacts

2010 ◽  
Author(s):  
Zhan-jiang Wang ◽  
Yuan-zhong Hu ◽  
Wen-zhong Wang ◽  
Hui Wang
Keyword(s):  
Dynamic Load ◽  
Normal Load ◽  
Contact Region ◽  
Computing Time ◽  
Numerical Procedure ◽  
Surface Displacement ◽  
Dissimilar Materials ◽  
Fretting Wear ◽  
History Of ◽  
Analytical Relations

When two surfaces in static contacts are subjected to combined loads applied in the normal and tangential directions, or just a normal load for dissimilar materials, microscopic slip would take place at certain areas of the contact region even though the contacting bodies remain still without macroscopic movement. The micro-slip is considered a major cause of fretting wear for the materials in contacts under alternating dynamic load or vibration, referred as the fretting contacts in this study. The fretting contact problem was solved using a semi-analytical method (SAM), in which analytical relations between a unite stress and corresponding surface displacement were obtained on the basis of Green functions. The contact pressure and shear tractions were then calculated by minimizing the complementary energy, and by a numerical procedure based on Conjugate Gradient Method (CGM) and Fast Fourier Transform (FFT) technique. The algorithm is very effective since the meshes are applied to the positions just in the contact areas of interest, which saves the computing time. The fretting contacts of dissimilar materials were studied and the effects of surface roughness were analyzed. Results show that the coupled effects of shear traction and material dissimilarity make the traction distributions quite different with the solutions from similar materials. The solutions under dynamic load depend on the path or history of the loading process, but the stress distributions and load-displacement curves will quickly converge to a periodic stability after several load cycles.

Materials for the history of the gospel-Baptist movement in Ukraine

1996 ◽  
pp. 4-15
Author(s):  
S. Golovaschenko ◽  
Petro Kosuha
Keyword(s):  
Large Scale ◽  
Religious Studies ◽  
Theological Seminary ◽  
National Academy Of Sciences ◽  
Evangelical Christians ◽  
Evangelical Christian ◽  
First Results ◽  
History Of ◽  
Fruitful Cooperation ◽  
Academy Of Sciences

The report is based on the first results of the study "The History of the Evangelical Christians-Baptists in Ukraine", carried out in 1994-1996 by the joint efforts of the Department of Religious Studies at the Institute of Philosophy of the National Academy of Sciences of Ukraine and the Odessa Theological Seminary of Evangelical Christian Baptists. A large-scale description and research of archival sources on the history of evangelical movements in our country gave the first experience of fruitful cooperation between secular and church researchers.

Stationary and Transient Response of Cylindrical Shells Under Random Excitation

1988 ◽  
Vol 110 (2) ◽  
pp. 205-209
Author(s):  
A. V. Singh
Keyword(s):  
Transient Response ◽  
Random Vibration ◽  
Time History ◽  
Wide Band ◽  
Random Excitation ◽  
Mode Shapes ◽  
The Finite Element Method ◽  
History Of ◽  
The Mean ◽  
Random Vibration Analysis

This paper presents the random vibration analysis of a simply supported cylindrical shell under a ring load which is uniform around the circumference. The time history of the excitation is assumed to be a stationary wide-band random process. The finite element method and the condition of symmetry along the length of the cylinder are used to calculate the natural frequencies and associated mode shapes. Maximum values of the mean square displacements and velocities occur at the point of application of the load. It is seen that the transient response of the shell under wide band stationary excitation is nonstationary in the initial stages and approaches the stationary solution for large value of time.

A Ritz Model of Unsteady Oil-Film Forces for Nonlinear Dynamic Rotor-Bearing System

2004 ◽  
Vol 71 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Tiesheng Zheng ◽  
Shuhua Yang ◽  
Zhonghui Xiao ◽  
Wen Zhang
Keyword(s):  
Free Boundary ◽  
Ritz Method ◽  
Computing Time ◽  
Force Model ◽  
The Finite Element Method ◽  
Oil Film ◽  
Great Saving ◽  
Cavitation Region ◽  
The Given ◽  
Oil Film Pressure

Based on the free boundary theory and variational method, this paper presents a Ritz method to compute the instantaneous hydrodynamic forces of a real bearing subject to any perturbed motions of the rotor. The given method manipulates the cavitation region by simply introducing a parameter to match the free boundary condition and, as a result, a very simple approximate formula of oil-film pressure were obtained leading to great saving of computing time. The numerical examples show the high accuracy of the proposed formulas. This oil-film force model is also used to analyze the nonlinear dynamics of a rigid unbalanced rotor with elliptical bearing support. The results well agree with those of the oil-film force model computed by the finite element method and the computing time is saved greatly.

Embankment on sludge: predicted and observed performances

2007 ◽  
Vol 44 (5) ◽  
pp. 545-563 ◽  
Author(s):  
Tien H Wu ◽  
Steven Z Zhou ◽  
Stephan M Gale
Keyword(s):  
Finite Element ◽  
Water Treatment ◽  
Input Data ◽  
Bayesian Updating ◽  
Full Scale ◽  
The Finite Element Method ◽  
Water Treatment Sludge ◽  
History Of ◽  
Finite Element Prediction ◽  
Test Embankment

The case history of an embankment built over soft water-treatment sludge is presented. To assure that the sludge would consolidate and gain strength as predicted, a test embankment was built. The observed performance of the test embankment was compared with the predicted performance to verify and modify design assumptions. The results were used to design and construct the full-scale embankment. The finite element method and the critical state model were used to predict the performances of the test embankment and the full-scale embankment. Bayesian updating and system identification were used to update the material properties used in the prediction for the test embankment. The updated properties were then used to update the prediction for the test embankment and to predict the performance of the full-scale embankment. These predictions were compared with the observed performances to evaluate the accuracies of the predictions with different input data. Efforts were made to identify factors that cause differences between predicted and measured performances.Key words: Bayesian updating, consolidation, finite-element prediction, shear strength, stability, water-treatment sludge.

scholarly journals Czech language and the traditional culture in the multiethnic environment (results of the field research of 2019 in Serbia, Romania, Bosnia and Herzegovina)

2021 ◽  
pp. 310-328
Author(s):  
Sergej A. Borisov
Keyword(s):  
Bosnia And Herzegovina ◽  
Rural Areas ◽  
Mother Tongue ◽  
Field Research ◽  
Folk Culture ◽  
Language And Culture ◽  
The Balkans ◽  
Language Data ◽  
First Results ◽  
History Of

The article provides an overview of a field study conducted among Czechs in Serbia, Romania, Bosnia and Herzegovina in 2019. The first results are presented, samples of transcribed texts are given. The purpose of the expedition was to collect narratives for the proper linguistic study of contact elements, conversations were conducted, among other things, about the history of the resettlement of Czechs to the Balkans, about folk culture, and interaction with other Slavic and non-Slavic ethnic groups. In the three regions studied, the Czech language remains unevenly due to a number of linguistic and extralinguistic factors. There are very few Czechs left in Bosnia and Herzegovina; Czech is the mother tongue only for elder people living in rural areas. In Serbia, there are several schools where Czech language and culture are taught, and in Romania there are schools where in the primary grades all subjects are taught in Czech. The collected language data is a valuable source for studying local Czech dialects and contact phenomena (borrowings, code-switching). The metalinguistic comments used by informants when they have difficulties in their Czech language during a conversation with a researcher are of particular interest to sociolinguistics.

Research on Numerical Algorithm of Constitutive Equation under High Speed Deformation in Hadfield Steel

2012 ◽  
Vol 562-564 ◽  
pp. 688-692 ◽  
Author(s):  
Deng Yue Sun ◽  
Jing Li ◽  
Fu Cheng Zhang ◽  
Feng Chao Liu ◽  
Ming Zhang
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Speed ◽  
High Strain ◽  
Equivalent Stress ◽  
Hadfield Steel ◽  
Stress And Strain ◽  
Strain Rates ◽  
The Finite Element Method

The influence of the strain rate on the plastic deformation of the metals was significant during the high strain rate of loading. However, it was very difficult to obtain high strain rate data (≥ 104 s-1) by experimental techniques. Therefore, the finite element method and iterative method were employed in this study. Numerical simulation was used to characterise the deformation behavior of Hadfield steel during explosion treatment. Base on experimental data, a modified Johnson-Cook equation for Hadfield steel under various strain rate was fitted. The development of two field variables was quantified during explosion hardening: equivalent stress and strain rates.

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