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Yoshiharu Mutoh - One of the best experts on this subject based on the ideXlab platform.
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fretting fatigue strength prediction of dovetail joint and bolted joint by using the generalized tangential Stress Range compressive Stress Range diagram
2014Co-Authors: Jayaprakash Murugesan, Yoshiharu MutohAbstract:Abstract Stress distribution at the contact edge plays a dominant role in fretting fatigue strength. In the previous studies, based on the Stress distribution at the contact edge, a generalized tangential Stress Range–compressive Stress Range (TSR–CSR) diagram has been proposed as a fretting fatigue fracture criterion. It has been also confirmed that the proposed diagram would be very useful to predict the fretting fatigue strength regardless of contact geometry, loading condition, material strength, environment, etc. for laboratory-type specimens. In the present study, fretting fatigue strengths of actual components, such as a dovetail joint and a bolted joint, have been predicted based on the generalized TSR–CSR diagram. To verify the effectiveness of the prediction based on the generalized TSR–CSR diagram, the fretting fatigue tests of dovetail joints and bolted joints were carried out. The fretting fatigue strengths of dovetail joints and bolted joints predicted based on the generalized TSR–CSR diagram were in good agreement with the experimental results.
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tangential Stress Range compressive Stress Range diagram for fretting fatigue design curve
2011Co-Authors: Yoshiharu MutohAbstract:Abstract Fretting fatigue strength can be effectively predicted regardless of pad geometry, rigidity, contact pressure and slip amplitude based on the tangential Stress Range–compressive Stress Range diagram. However, the tangential Stress Range–compressive Stress Range diagram is a material property and applicable only to the material concerned. In the present study, a new approach for predicting fretting fatigue strength irrespective of material has been proposed based on a generalized tangential Stress Range–compressive Stress Range diagram. The generalized tangential Stress Range–compressive Stress Range diagram was obtained by normalizing the tangential Stress Range and compressive Stress Range values by tensile strength of each material. It was found that the generalized tangential Stress Range–compressive Stress Range diagrams for all the steels merged to one line and could be applicable for predicting fretting fatigue strength of wide Range of steels.
Z.d. Xiang - One of the best experts on this subject based on the ideXlab platform.
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long term creep rupture strength prediction for a new grade of 9cr martensitic creep resistant steel g115 an application of a new tensile creep rupture model
2020Co-Authors: C C Jiang, X.l. Song, Z Dong, J Jia, Z.d. XiangAbstract:Abstract A method is presented to firstly rationalise the short-term creep rupture strength data and then to predict the 100,000 h creep rupture strengths of a new 9Cr grade of martensitic creep resistant steels (G115) at different temperatures. The method is made possible by a new tensile creep rupture model, which is formulated by combining a new tensile creep model that integrates tensile strength at creep temperature with the Monkman–Grant relationship. On the basis of this new tensile creep rupture model, the activation energy of creep rupture determined for the steel G115, which is 293 ± 25 kJ/mol, does not depend on Stress or Stress Range, and the creep rupture Stress exponent depends only on Stress Range but not on temperature. The model parameters determined from short-term creep rupture strength data can then be used to predict the long-term creep rupture strengths at different temperatures for this new steel grade. The reliability of the predictions is analysed and the microstructural evolutions occurring during creep that may cause premature creep rupture and hence lead to possible over-predictions are also delineated. Based on the prediction results obtained, the highest applicable temperature of this new steel grade for power plant applications is determined to be slightly higher than 625 °C.
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on the applicability of boundary condition based tensile creep model in predicting long term creep strengths and lifetimes of engineering alloys
2019Co-Authors: H P Yao, X.l. Song, J Jia, Y R Zhao, Z.d. XiangAbstract:Abstract Creep behaviour of metal alloys for critical high temperature engineering applications is usually studied by uniaxial tensile creep tests. The Stress and temperature dependence of steady-state or minimum creep rate observed in such tests is rationalised at present on the basis of either Norton or MBD equation. But, the Stress exponent determined on such basis depend strongly and often irregularly on test temperature and the creep activation energy varies with Stress or Stress Range. Hence, these parameters cannot be used for long-term predictions. Here, it is shown that these difficulties can be removed if a new creep model, which incorporates tensile strength, is used to rationalise the creep data. The Stress exponent determined then does not depend on temperature although it depends on Stress Range, and the creep activation energy does not depend on Stress. Thus, there is no relationship between Stress exponent value and creep mechanism. Consequently, the new tensile creep model can be used in combination with Monkman-Grant relationship to predict the long-term tensile creep strengths and lifetimes at different temperatures using creep parameters determined from short-term tensile creep tests. Both the deficiencies of the Norton and MBD equations and the predictive quality of the new tensile creep model are demonstrated here using uniaxial tensile creep data and tensile strength data measured for two totally different types of creep resistant engineering alloys: 9Cr-1Mo steel and Ni base superalloy Ni-16Cr-8.5Co-3.5Al-3.5Ti-2.6W-1.8Mo-0.9Nb.
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effects of heterogeneous and homogenous laves phase precipitation on creep rupture strength of fe 9cr 3co wt alloys at 650 c
2014Co-Authors: S. Zhu, M. Yang, X.l. Song, S. Tang, Zhan Zhang, Z.d. XiangAbstract:The relationship between creep rupture strength and Laves phase precipitation and growth kinetics was investigated at 650 °C for two Fe-9Cr-3Co (wt.%) alloys differing mainly in the amounts of W and Mo added. In the alloy with 3.14 wt.% W added, Laves phase precipitated heterogeneously on grain boundaries and hence had little dispersion strengthening effect. Its Stress exponent for rup-ture time became lower in the lower creep Stress Range tested. In the alloy with 1.31 wt.% W and 3.22 Mo added, Laves phase precipitated both heterogeneously on grain boundaries and homogenously within grains and there was no reduction in Stress exponent for rupture time in the whole Stress Range tested. The Lave phase precipitation kinetics increased with increasing the total amount of W and Mo in the alloys. The differences in Stress-rupture time relationship observed between the two alloys were discussed in relation to their differences in the Lave phase precipitation behaviour.
Reinhard Pippan - One of the best experts on this subject based on the ideXlab platform.
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fatigue crack growth threshold as a design criterion statistical scatter and load ratio in the kitagawa takahashi diagram
2016Co-Authors: Stefan Kolitsch, Jurgen Maierhofer, Hanspeter Ganser, Reinhard PippanAbstract:Cracks in components reduce the endurable Stress so that the endurance limit obtained from common smooth fatigue specimens cannot be used anymore as a design criterion. In such cases, the Kitagawa-Takahashi diagram can be used to predict the admissible Stress Range for infinite life, at a given crack length and Stress Range. This diagram is constructed for a single load ratio R. However, in typical mechanical engineering applications, the load ratio R varies widely due to the applied load spectra and residual Stresses. In the present work an extended Kitagawa-Takahashi diagram accounting for crack length, crack extension and load ratio is constructed. To describe the threshold behaviour of short cracks, a master resistance curve valid for a wide Range of steels is developed using a statistical approach.
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modified kitagawa takahashi diagram accounting for finite notch depths
2015Co-Authors: Jurgen Maierhofer, Hanspeter Ganser, Reinhard PippanAbstract:Abstract The Kitagawa–Takahashi diagram in its commonly used form allows to predict, for cracks of given length and Stress Range, the allowable Stress Range for infinite life. However, caution is advised if a crack emanates not directly from the plane surface but from a sharp, crack-like notch instead. In this contribution, it is shown that taking the crack length equal to the total flaw depth (sum of notch depth and crack length) gives non-conservative results. Based on a simple mechanical model, a 3-dimensional Kitagawa–Takahashi diagram considering the build-up of crack growth resistance as well as the influence of the notch depth is developed. Comparison of model predictions and experimental results shows good agreement.
Dan M Frangopol - One of the best experts on this subject based on the ideXlab platform.
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bridge fatigue reliability assessment using probability density functions of equivalent Stress Range based on field monitoring data
2010Co-Authors: Kihyon Kwon, Dan M FrangopolAbstract:This paper focuses on fatigue reliability assessment of steel bridges by using probability density functions of equivalent Stress Range based on field monitoring data. To date, existing steel bridges have experienced fatigue cracks initiated and propagated. As a result, bridge structural integrity may not be preserved safely up to its anticipated service life. For this reason, it is necessary to assess and predict bridge fatigue reliability. The AASHTO Specifications can be used to estimate capacity of structural details in the fatigue reliability assessment, whereas long-term monitoring data can be used to provide efficient information for fatigue in terms of equivalent Stress Range and cumulative number of Stress cycles. Under uncertainties, an approach using probabilistic distributions associated with Stress Ranges is proposed to effectively predict equivalent Stress Ranges for bridge fatigue reliability assessment. The fatigue detail coefficient, A, and the equivalent Stress Range, Sre, are both treated as random variables in the proposed fatigue reliability approach. This approach is illustrated on two existing bridges which are expected to experience finite or infinite fatigue life.
Kentaro Yamada - One of the best experts on this subject based on the ideXlab platform.
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Stress analyses and fatigue evaluation of rib to deck joints in steel orthotropic decks
2008Co-Authors: Zhigang Xiao, Samol Ya, Kentaro Yamada, Xiao Ling ZhaoAbstract:The transverse distribution of wheel loads in orthotropic decks generates significant out-of-plane bending moments in the deck plate and rib wall at the rib-to-deck joint. Due to the relatively small thickness of both the deck plate and rib wall, the out-of-plane bending moments result in high local flexural Stresses causing fatigue cracks to develop at the joint. In this study, the transverse Stresses within the joint region that arise under the action of wheel loads are investigated with finite element analyses. Based on the Stress results and the basic theories of linear elastic fracture mechanics, the design fatigue strength is determined for the joint. Factors affecting the Stress Range are also studied. The analyses show that the surface Stresses in the deck plate are much larger than those in the rib wall in the case of 75% weld penetration into the rib wall, indicating that the fatigue strength of the joint is governed by the fatigue cracks propagating into the thickness of deck plate. It is also shown with finite element analyses that increasing the distribution area of wheel load or the thickness of deck plate can reduce the Stress Range of the deck plate and increase significantly the fatigue life of the joint.
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fatigue life evaluation of welded joints under combined normal and shear Stress cycles
2005Co-Authors: Intae Kim, Kentaro YamadaAbstract:This paper discusses methods for evaluating the fatigue life when combined normal and shear Stresses are applied in phase simultaneously. The conventional fatigue design procedures based on maximum principal or normal Stress Ranges are reviewed using published data. This indicates that the fatigue life may be under- or overestimated by the procedures, when the shear-to-normal-Stress ratio Range is close to 1.0. A proposed alternative procedure, based on the equivalent Stress Range and the fatigue life for a normal Stress Range, produces a much more appropriate evaluation of the fatigue life for combined Stress Ranges, independent of the ratio.
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fatigue crack growth measurements under spectrum loading
2000Co-Authors: Kentaro Yamada, Qiuliang Cao, Naoki OkadoAbstract:Abstract Fatigue crack growth rates under variable amplitude Stress cycles were measured on two center-cracked tension specimens made of SM520B steel. Four loading spectra, right-skewed and left-skewed β distributions with the minimum or maximum Stress constant, were applied to the specimens. Based on the root-mean-cube Stress Range, the test results are compared with the fatigue crack growth behavior under constant amplitude loading with the same Stress ratio. They are generally in good agreement, indicating that effect of Stress ratio is generally dominant. However, when large number of Stress cycles are in the low Stress Range region, the effect of threshold Stress intensity factor Range is found to be large.
