The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform

Weiwei Wang - One of the best experts on this subject based on the ideXlab platform.

  • crack initiation life prediction for solid cylinders with transverse circular holes under in phase and out of phase multiaxial loading
    International Journal of Fatigue, 2005
    Co-Authors: Weiwei Wang
    Abstract:

    Abstract This work investigates crack initiation life for AISI 316 stainless steel solid cylinders with transverse circular holes under in-phase and out-of-phase multiaxial loading. Elastic–plastic finite element analysis is applied to determine the local stress/strain state. Four critical plane approaches and four combined energy and critical plane approaches are employed to predict the crack initiation life by correlating the predictive parameters with Smooth Specimen data. The critical plane model proposed by Fatemi and Socie and the energy-critical plane prediction model for shear failure-type material proposed by Chen, Xu and Han in 1999 are found to yield better predictions than other models. The location of crack initiation is also investigated herein and compared with the experimentally obtained results.

  • crack initiation life prediction for solid cylinders with transverse circular holes under in phase and out of phase multiaxial loading
    International Journal of Fatigue, 2005
    Co-Authors: Weiwei Wang
    Abstract:

    Abstract This work investigates crack initiation life for AISI 316 stainless steel solid cylinders with transverse circular holes under in-phase and out-of-phase multiaxial loading. Elastic–plastic finite element analysis is applied to determine the local stress/strain state. Four critical plane approaches and four combined energy and critical plane approaches are employed to predict the crack initiation life by correlating the predictive parameters with Smooth Specimen data. The critical plane model proposed by Fatemi and Socie and the energy-critical plane prediction model for shear failure-type material proposed by Chen, Xu and Han in 1999 are found to yield better predictions than other models. The location of crack initiation is also investigated herein and compared with the experimentally obtained results.

K Laha - One of the best experts on this subject based on the ideXlab platform.

  • creep life prediction of 9cr 1mo steel under multiaxial state of stress
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Sunil Goyal, K Laha
    Abstract:

    Abstract Creep rupture life of 9Cr–1Mo steel under multiaxial state of stress has been assessed. Stress multiaxiality in cylindrical Specimens during creep tests has been introduced by incorporating circumferential U-notches of different notch root radii. Creep tests were carried out on both Smooth and notched Specimens of the steel at 873 K over the net applied stresses in the range of 110–210 MPa. The creep rupture life of the steel was found to be higher in the presence of notch than that of Smooth Specimen indicating ‘notch strengthening’ behavior under multiaxial state of stress. The extent of strengthening tends to saturate for relatively sharper notches. Finite element analysis of stress and strain distributions across the notch was carried out to assess the notch strengthening behavior observed in the steel. The reduction in the von-Mises stress, extent of which increased and tends towards saturation with increase in notch root radii, resulted in increase in rupture life under multiaxial state of stress. Estimation of the creep rupture life under multiaxial state of stress has been assessed based on the different models, invoking the concept of skeletal point for calculating the representative stress. It has been observed that the creep rupture behavior of the steel under multiaxial state of stress is predominantly governed by the von-Mises stress. The creep rupture life has been predicted using finite element analysis coupled with continuum damage mechanics.

  • notch creep rupture strength of 316ln ss and its variation with nitrogen content
    Nuclear Engineering and Design, 2013
    Co-Authors: V Ganesan, Ganesh J Kumar, K Laha, M D Mathew
    Abstract:

    Abstract Low carbon, nitrogen-alloyed, 316L(N) stainless steel (SS) is a major structural material for high temperature components of sodium cooled fast reactors. With a view to increase the design life from 40 to 60 years and beyond, studies are being carried out to develop 316LN grade austenitic stainless steels with superior high temperature mechanical properties. As a part of this development programme, four laboratory heats of 316LN SS containing 0.07, 0.11, 0.14 and 0.22 wt.% nitrogen are being evaluated extensively. Creep tests have been carried out on Smooth and notched sample geometries at a nominal stress level of 200 MPa and at a temperature of 923 K. The notched Specimens contained a V-notch at an angle of 60° with root radius of 0.19 mm, which provided theoretical stress concentration factor of 4.2. The gauge diameter of the notched Specimen at the notch root was 6.4 mm and was 10 mm for the Smooth Specimen. It was found that the presence of notch increased the creep life for all the four heats. In the case of Smooth Specimens, rupture life increased with increase in nitrogen content. In the case of notched Specimens, rupture life showed a peak value at 0.14 wt.% nitrogen content. The ratio of rupture life of Smooth to notched Specimens decreased with increase in the nitrogen content from 18 for the material containing 0.07 wt.% nitrogen to 3 for the material containing 0.22 wt.% nitrogen thereby implying that the notch strengthening effect decreased significantly at high nitrogen levels. The notched Specimens showed a lower value of ductility, measured in terms of reduction in area, as compared to the Smooth Specimens. Finite element analysis of the stress and strain distribution in the notch region was carried out as a function of nitrogen content. The stress concentration factor ( K t ) evaluated through stress analysis was found to be 4.2 for the geometry used in this study. The creep analysis was run for a sufficiently long time to achieve the steady state creep condition. The influence of nitrogen content on the values of triaxial stresses under steady state conditions for the given notch geometry was evaluated. The presence of notch with the investigated notch geometry lowered the maximum principal stress and this lead to higher rupture life in all the four heats.

Weida Yao - One of the best experts on this subject based on the ideXlab platform.

Junhao Liang - One of the best experts on this subject based on the ideXlab platform.

  • prediction of creep rupture life of a v notched bar in dd6 ni based single crystal superalloy
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Dongsheng Zhang, Junhao Liang
    Abstract:

    Abstract The circumferential V-type notched round bar has been designed to investigate the effect of multi-axial stress state on creep rupture behavior of DD6 Ni-based single crystal superalloys at 1100 °C. Creep test on both Smooth and notched Specimens were carried out under 160 MPa and 200 MPa on the minimum net-section. Time to creep fracture was found to be higher in notched Specimens than in Smooth Specimens. Finite element (FE) analysis coupled with continuum damage mechanics (CDM) was carried out to understand the stress distribution and the creep damage evolution under uniaxial and multi-axial stress states. The creep rupture life of the Smooth Specimen was successfully predicted by the classical Kachanov–Rabotnov damage law. The creep rupture life of the notched Specimen predicted by finite element calculation incorporating a multi-axial creep CDM model was in good agreement with the experimental results. Both the fracture morphology and FE damage analysis indicate that rupture initiates first at the notch root in the notched Specimen and finally towards to the center location.

J J F Bonnen - One of the best experts on this subject based on the ideXlab platform.

  • threshold crack growth behavior of shear and tensile cracks
    International Journal of Fatigue, 2012
    Co-Authors: J J F Bonnen, T H Topper
    Abstract:

    Abstract Crack-face interference-free mode I and mode II crack-growth data was combined with Smooth axial ( λ  =  e xy / e xx  = 0) and torsional ( λ  = ∞) endurance limit data to develop unified crack growth models that incorporate both shear and tensile cracking. The crack growth models incorporated growth from a slip band (including short crack behavior) size crack until the final failure of a long crack, and the ability to switch between crack growth on shear planes to growth on tensile planes. The models successfully predicted Smooth Specimen crack-face interference-free fatigue lives and gave reasonable estimates of the Smooth Specimen endurance limits of crack-face interference free tubular tests run at intermediate strain ratios ( λ  = 3/4, 3/2, and 3). The series of Kitigawa–Takahashi (threshold fatigue) diagrams developed from the models help illustrate the competition between shear and tensile cracking at the fatigue limit under crack-face interference-free crack growth.

  • modeling crack closure and damage in variable amplitude fatigue using Smooth Specimen fatigue test data
    International Journal of Fatigue, 2011
    Co-Authors: M Elzeghayar, T H Topper, F A Conle, J J F Bonnen
    Abstract:

    During overloads in variable amplitude fatigue, local stresses at small cracks growing from notches reach yield stress magnitude. Such high stress levels result in a large decrease in crack opening stress and an increase in the fatigue damage of subsequent smaller stress cycles. This paper presents a methodology for modeling changes in crack opening stress level and fatigue damage using data derived from periodic underload fatigue tests of Smooth Specimens. Predicted crack closure stress levels agree well with those obtained from crack growth observations made with a high magnification microscope.