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B W Darvell - One of the best experts on this subject based on the ideXlab platform.
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fatigue testing of a niti rotary instrument part 1 strain life relationship
International Endodontic Journal, 2007Co-Authors: Gsp Cheung, B W DarvellAbstract:Aim To examine the fatigue behaviour using a Strain-Life Approach, and to determine the effect of water on the fatigue life of a NiTi rotary instrument. Methodology Instruments of one brand of NiTi engine-file (size 25, ProFile 0.04 and 0.06) were subjected to rotational bending either in air or under water, the number of revolutions to fracture (Nf) being recorded using an optical counter and an electronic break-detection circuit. The effective surface strain amplitude (ɛa) for each specimen was determined from the curvature of the instrument (on a photograph) and the diameter of the fracture cross-section (from a scanning electron micrograph of the fracture surface). Strain was plotted against fatigue life and the low-cycle fatigue (LCF) region identified. Values were examined using two-way analysis of variance for difference between various instrument–environment combinations. Results A total of 212 instruments were tested. A Strain-Life relationship typical of metals was found. Nf declined with an inverse power function dependence on ɛa. A fatigue limit was present at about 0.7% strain. The apparent fatigue-ductility exponent, a material constant for the LCF life of metals, was found to be between −0.45 and −0.55. There was a significant effect of the environmental condition on the LCF life, water being more detrimental than air. Conclusions The fatigue behaviour of NiTi rotary instrument is typical of most metals, provided that the analysis is based on the surface strain amplitude, and showed a high-cycle and a LCF region. The LCF life is adversely affected by water.
Sankar Dhar - One of the best experts on this subject based on the ideXlab platform.
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fatigue failure of notched specimen a strain life Approach
Materials Sciences and Applications, 2011Co-Authors: Bikash Joadder, Jagabandhu Shit, Sanjib Acharyya, Sankar DharAbstract:Failure cycles of notched round specimens under strain controlled cyclic loading are predicted using strain—life relations obtained from experiment for plain fatigue round specimens. For notched specimens, maximum strain occurs at notch root and is different from applied controlled strain. The maximum strain is computed by appropriate Finite element analysis using the FE software ABAQUS. FE model and material parameters are validated by comparing the FE results and experimental results of LCF tests of round specimens. This value of maximum strain is used for prediction of failure cycles. Prediction is compared with the experimental results. The results show good matching.
Gsp Cheung - One of the best experts on this subject based on the ideXlab platform.
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fatigue testing of a niti rotary instrument part 1 strain life relationship
International Endodontic Journal, 2007Co-Authors: Gsp Cheung, B W DarvellAbstract:Aim To examine the fatigue behaviour using a Strain-Life Approach, and to determine the effect of water on the fatigue life of a NiTi rotary instrument. Methodology Instruments of one brand of NiTi engine-file (size 25, ProFile 0.04 and 0.06) were subjected to rotational bending either in air or under water, the number of revolutions to fracture (Nf) being recorded using an optical counter and an electronic break-detection circuit. The effective surface strain amplitude (ɛa) for each specimen was determined from the curvature of the instrument (on a photograph) and the diameter of the fracture cross-section (from a scanning electron micrograph of the fracture surface). Strain was plotted against fatigue life and the low-cycle fatigue (LCF) region identified. Values were examined using two-way analysis of variance for difference between various instrument–environment combinations. Results A total of 212 instruments were tested. A Strain-Life relationship typical of metals was found. Nf declined with an inverse power function dependence on ɛa. A fatigue limit was present at about 0.7% strain. The apparent fatigue-ductility exponent, a material constant for the LCF life of metals, was found to be between −0.45 and −0.55. There was a significant effect of the environmental condition on the LCF life, water being more detrimental than air. Conclusions The fatigue behaviour of NiTi rotary instrument is typical of most metals, provided that the analysis is based on the surface strain amplitude, and showed a high-cycle and a LCF region. The LCF life is adversely affected by water.
Y.g. Kim - One of the best experts on this subject based on the ideXlab platform.
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Fatigue life assessment of fabric braided composite rubber hose in complicated large deformation cyclic motion
Finite Elements in Analysis and Design, 2015Co-Authors: Jin-rae Cho, Y.h. Yoon, C.w. Seo, Y.g. KimAbstract:High-pressure braking hose in the automobile power braking system undergoes the complicated large deformation cyclic motion during the driver's steering operation and the up and down motion of vehicle, so that the fatigue damage becomes accumulated in proportional to the cycle number. Since the occurrence of fatigue-induced micro crack in the braking hose may cause the oil leakage, the fatigue life assessment becomes the most important task in the design of high-durable braking hose. In this context, this paper intends to introduce a numerical method for predicting the fatigue life of braking hose in the lamination structure composed of pure rubber and fabric braided layers. A specific trajectory of braking hose in the combined tire's steering and car's up-down motion is defined as the target cyclic path, and the variations in strain and stress fields along the cyclic path are analyzed by the large deformation finite element analysis. The strain and stress cycles in their variations are calculated by the rainflow cycle counting method, and the fatigue life cycle is evaluated by three fatigue life evaluation models, together with the Palmgren-Miner accumulative damage law. The e - N curves of rubber layers are obtained by a specially designed displacement-controlled fatigue test using rubber specimens, while the inserted fabric braided layers which are excluded from the fatigue life assessment are modeled as an orthotropic material. The validity of the proposed numerical method is illustrated by the numerical experiments, and the fatigue life cycles to the evaluation model and to the cyclic path are investigated and compared. The fatigue life of braided 5-layer rubber hose in the complicated large deformation cycle motion is numerically evaluated.The fatigue life cycles are evaluated by three different fatigue evaluation models for two distinct cycle paths.The relative differences in the critical fatigue life cycles with respect to the basic Strain-Life Approach are - 35.13 ~ + 18.80 % at the Morrow model and - 48.24 ~ + 12.04 % at the SWAT model, respectively.
Bikash Joadder - One of the best experts on this subject based on the ideXlab platform.
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fatigue failure of notched specimen a strain life Approach
Materials Sciences and Applications, 2011Co-Authors: Bikash Joadder, Jagabandhu Shit, Sanjib Acharyya, Sankar DharAbstract:Failure cycles of notched round specimens under strain controlled cyclic loading are predicted using strain—life relations obtained from experiment for plain fatigue round specimens. For notched specimens, maximum strain occurs at notch root and is different from applied controlled strain. The maximum strain is computed by appropriate Finite element analysis using the FE software ABAQUS. FE model and material parameters are validated by comparing the FE results and experimental results of LCF tests of round specimens. This value of maximum strain is used for prediction of failure cycles. Prediction is compared with the experimental results. The results show good matching.