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Equivalent Stress (equivalent + stress)

Distribution by Scientific Domains

Polymers and Materials Science	40%
Medical Sciences	40%

Selected Abstracts

Changes in compaction stress distributions in roots resulting from canal preparation

INTERNATIONAL ENDODONTIC JOURNAL, Issue 12 2006
A. Versluis
Abstract Aim, To examine if canal enlargement with instruments of controlled taper leads to more uniform stress distributions within a root, thereby reducing fracture susceptibility. Methodology, Finite element models of a mandibular incisor were constructed with round and oval canal profiles, based on measurements from extracted teeth. The shapes of rotary nickel,titanium instruments (ProTaper F1, F2, and F3 and ProFile size 30, 0.04 taper and size 30, 0.06 taper; Dentsply Maillefer) were superimposed on the canals. Equivalent stresses and circumferential stresses in the root were calculated for a compaction load. Results, The highest stresses were found at the canal wall. Round canals showed lower uniform distributions, whilst oval canals showed uneven distributions with high concentrations at the buccal and lingual canal extensions and greater stresses in the coronal and middle thirds than in the apical third. Preparation of round canals introduced only small circumferential stress increases in the apical half; preparation of oval canals produced substantial reductions where the canal was enlarged to a smooth round shape. Even where fins were not completely eliminated, the maximum stresses were still reduced by up to 15%. External distal and mesial surfaces of roots with oval canals showed moderate stress concentrations that were minimally affected by preparations, whilst stress concentrations emerged on roots with round canals when preparation sizes increased. Conclusions, The potential for reducing fracture susceptibility exists as a result of round canal profiles achieved and smooth canal taper. Even when fins were not contacted by the instrument, stresses within the root were lower and more evenly distributed than before preparation. [source]

Multiaxial fatigue of welded joints under constant and variable amplitude loadings

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2001
C. M. Sonsino
Flange-tube joints from fine grained steel StE 460 with unmachined welds were investigated under biaxial constant and variable amplitude loading (bending and torsion) in the range of 103 to 5,×,106 cycles to crack initiation and break-through, respectively. In order not to interfere with residual stresses they were relieved by a heat treatment. In-phase loading can be treated fairly well using the conventional hypotheses (von Mises or Tresca) on the basis of nominal, structural or local strains or stresses. But the influence of out-of-phase loading on fatigue life is severely overestimated if conventional hypotheses are used. However, the hypothesis of the effective equivalent stress that is introduced leads to fairly good predictions for constant as well as for random variable amplitude loads. Therefore, the knowledge of local strains or stresses is necessary. They are determined by boundary element analyses that are dependent on weld geometry. This hypothesis considers the fatigue-life-reducing influence of out-of-phase loading by taking into account the interaction of local shear stresses acting in different surface planes of the material. Further, size effects resulting from weld geometry and loading mode were included. Damage accumulation under a Gaussian spectrum can be assessed for in- and out-of-phase combined bending and torsion using an allowable damage sum of 0.35. [source]

Dimensional measurement and finite element analysis of I-bar clasps in clinical use

JOURNAL OF ORAL REHABILITATION, Issue 11 2000
Y. Sato
An I-bar clasp is a popular retainer for distal-extension removable partial dentures. However, there have been almost no evidence-based criteria on the mechanically preferable shape. The present study aimed to investigate the variations of dimension in I-bar clasps used in patients, and to clarify the effect of the variations on stiffness and stress of I-bar clasps by finite element analysis. Dimensions (thickness, width, taper, radius of curvature, length, relation to oral structures) of 23 I-bar clasps were measured. A three-dimensional finite element model was made for each measured I-bar clasp with vertical and horizontal straight sections connected with a curved section. A concentrated load of 5 N was applied at the lowest point of the tip that contacted the abutment in the buccal direction. Maximal equivalent stress and stiffness of each clasp were evaluated. The measured dimension, stiffness, and maximum stress showed wide variations. Mean stiffness was far from the proper one, and mean stress was near the proportional limit of Co,Cr alloy. Considering the stiffness and stresses in this study, only six clasps out of 23 were appropriate. These results suggest that evidence-based criteria of preferable shape of I-bar clasps should be determined. [source]

A comparative analysis of a modified picture frame test for characterization of woven fabrics

POLYMER COMPOSITES, Issue 4 2010
A.S. Milani
An experimental, finite-element analysis framework is utilized to estimate the deformation state in a modified version of the picture frame test. During the analysis, the effect of fiber misalignment and the deformation heterogeneity in the tested fabric, a 2 × 2 PP/E-Glass twill, is accounted for and a force prediction model is presented. Using an equivalent stress,strain normalization scheme, the comparison of the modified test with the conventional (original) picture frame and bias-extension tests is also made, and results reveal similarities and differences that should receive attention in the identification of constitutive models of woven fabrics using these basic tests. Ideally, the trellising behavior should not change from one test to another but results show that in the presence of fiber misalignment, the modified picture frame test yields a behavior closer to that of the bias-extension test, while the general form of the test's repeatability, measured by a signal-to-noise metric, remains similar to the original picture frame test. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]

An orthotropic damage model for masonry structures

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2002
Luisa Berto
Abstract An orthotropic damage model specifically developed for the analysis of brittle masonry subjected to in-plane loading is described. Four independent internal damage parameters, one in compression and one in tension for each of the two natural axes of the masonry, are defined allowing the stiffness recovery at crack closure as well as the different inelastic behaviour along each natural axis to be considered. The damage field of the material is defined in terms of four equivalent stresses and results, in the space of the in-plane effective stresses, in a double pyramid with a rectangular base where the slopes of the faces correspond to the internal friction angle of the material. The equivalent stresses also control the growth of the damage parameters. The returning path from the effective to the damaged stresses is given by multiplication by a fourth-rank damage effect tensor, which is a function of the damage parameters and of the effective stress state. Mesh size regularization is achieved by means of an enhanced local method taking into account the finite element size. Good agreement has been found in the comparison between numerical results and experimental data both for masonry shear panels and for a large-scale masonry holed wall. Copyright © 2002 John Wiley & Sons, Ltd. [source]