The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

Gunnar Åkerström - One of the best experts on this subject based on the ideXlab platform.

  • Sheet Metal Fatigue near nuts welded to thin sheet structures
    International Journal of Fatigue, 2008
    Co-Authors: Jonas W. Ringsberg, Pierre Orvegren, Hans-fredrik Henrysson, Gunnar Åkerström
    Abstract:

    One of the Fatigue design processes of a car body is stress-based sheet Metal Fatigue near nuts welded to thin sheets (weld nuts). In this investigation, the influence from nut geometry and dimension, as well as sheet material and thickness on sheet Metal Fatigue life was studied by Fatigue experiments and numerical analyses. The Fatigue experiments were force-controlled and carried out on a weld nut specimen which, during the reversed loading that was applied, was designed to result in bending Fatigue loading conditions of the sheet Metal near the weld nut. The results from the experiments were Fa–N curves for various combinations of nut geometry and dimension, sheet material and thickness. Numerical analyses of the experiments were carried out by linear elastic finite element (FE) analyses, in order to transform the Fa–N curves to Wohler (sig_a–N) curves. A simplified FE model of the weld nut, which is suitable for structural analysis of car body structures, was used. The structural stresses calculated using the FE model showed good agreement with the structural stresses calculated using an analytical model that is based on plate theory. The conclusion was that the simplified representation of the weld nut, and the mesh density used in the FE model, was appropriate for computation of the stress response near a weld nut subjected to bending Fatigue loading conditions. Finally, ra–N curves were computed for each weld nut configuration using its experimental data set. A sig_a–N curve fitted to all data sets resulted in the relation sig_a = 9888N^0.312. The sig_a–N curves for the 21 weld nut configurations tested were gathered within a factor of three in Fatigue life from this curve.

Jonas W. Ringsberg - One of the best experts on this subject based on the ideXlab platform.

  • Sheet Metal Fatigue near nuts welded to thin sheet structures
    International Journal of Fatigue, 2008
    Co-Authors: Jonas W. Ringsberg, Pierre Orvegren, Hans-fredrik Henrysson, Gunnar Åkerström
    Abstract:

    One of the Fatigue design processes of a car body is stress-based sheet Metal Fatigue near nuts welded to thin sheets (weld nuts). In this investigation, the influence from nut geometry and dimension, as well as sheet material and thickness on sheet Metal Fatigue life was studied by Fatigue experiments and numerical analyses. The Fatigue experiments were force-controlled and carried out on a weld nut specimen which, during the reversed loading that was applied, was designed to result in bending Fatigue loading conditions of the sheet Metal near the weld nut. The results from the experiments were Fa–N curves for various combinations of nut geometry and dimension, sheet material and thickness. Numerical analyses of the experiments were carried out by linear elastic finite element (FE) analyses, in order to transform the Fa–N curves to Wohler (sig_a–N) curves. A simplified FE model of the weld nut, which is suitable for structural analysis of car body structures, was used. The structural stresses calculated using the FE model showed good agreement with the structural stresses calculated using an analytical model that is based on plate theory. The conclusion was that the simplified representation of the weld nut, and the mesh density used in the FE model, was appropriate for computation of the stress response near a weld nut subjected to bending Fatigue loading conditions. Finally, ra–N curves were computed for each weld nut configuration using its experimental data set. A sig_a–N curve fitted to all data sets resulted in the relation sig_a = 9888N^0.312. The sig_a–N curves for the 21 weld nut configurations tested were gathered within a factor of three in Fatigue life from this curve.

  • Sheet Metal Fatigue near nuts welded to thin sheet structures in car bodies
    2006
    Co-Authors: Jonas W. Ringsberg, Orvegren Pierre, Henrysson Hans-fredrik, Åkerström Gunnar
    Abstract:

    The Fatigue design process of a car body includes, among others, stress-based sheet Metal Fatigue near nuts welded to thin sheets (weld nuts). In this investigation, the influence from nut geometry and dimension, and sheet material and thickness, on sheet Metal Fatigue life was studied by Fatigue experiments and numerical analyses. The Fatigue experiments were force-controlled and carried out on a weld nut specimen which, during the applied reversed loading, was designed to result in bending Fatigue loading conditions of the sheet Metal near the weld nut. The results from the experiments were Fa-N curves for various combinations of nut geometry and dimension, sheet material and thickness. Numerical analyses of the experiments were carried out, by linear elastic finite element (FE) analyses, in order to transform the Fa-N curves to Wohler (σa-N) curves. A simplified FE model of the weld nut was used which is suitable for structural analysis of car body structures. The stresses calculated using the FE model were compared with the stresses calculated using an analytical model that is based on plate theory, and there was good agreement in results between models. The conclusion was that the simplified representation of the weld nut, and the mesh density in the FE model, was appropriate for computation of the stress response near a weld nut subjected to bending Fatigue loading conditions. Finally, σa-N curves were computed for each weld nut configuration using its experimental data set. A σa-N curve fitted to all data sets resulted in the relation σa = 5706•N -0.269. The σa-N curves for the eight weld nut configurations tested were gathered within a factor of three in Fatigue life from this curve.

A.m. Lewis - One of the best experts on this subject based on the ideXlab platform.

  • A theoretical model of the response of an eddy-current probe to a surface-breaking Metal Fatigue crack in a flat test-piece
    Journal of Physics D: Applied Physics, 1992
    Co-Authors: A.m. Lewis
    Abstract:

    An analytical calculation is presented for the response of an air-cored eddy-current probe to a surface-breaking Metal Fatigue crack in a flat plate, modelled as a region of zero conductivity, infinitely long and uniformly deep, in a homogeneous, conducting half-space. The problem is formulated in terms of the magnetic scalar potential, subject to surface impedance boundary conditions, with a line source to represent the crack. Solutions are found using spatial Fourier transforms. The theory is valid for both ferromagnetic and non-magnetic Metals, providing that the electromagnetic penetration depth is small compared with the crack depth. The signal is expressed in terms of two integrals which, in general, must be evaluated numerically. Specific computations have been performed for a circular, single-coil probe.

  • ELECTROMAGNETIC METHODS FOR NDE OF Metal Fatigue CRACKS: PRACTICAL TECHNIQUES AND THEORETICAL MODELS
    Nondestructive Testing and Evaluation, 1992
    Co-Authors: A.m. Lewis
    Abstract:

    The available electromagnetic methods used for the detection and measurement of Metal Fatigue cracks are first described. A distinction is drawn between the eddy-current and potential drop methods, which detect the crack primarily because of the break in electric conductivity, and the magnetic particle and flux leakage methods which detect the break in magnetic permeability. The importance of the skin-effect is stressed and the various frequency regimes distinguished. Theoretical models of each method are described and compared and their strengths and weaknesses discussed.

Michael M. Khonsari - One of the best experts on this subject based on the ideXlab platform.

  • Online monitoring of Metal Fatigue life
    Structural Health Monitoring, 2019
    Co-Authors: K. P. Lijesh, Mohammad Mehdizadeh, Michael M. Khonsari
    Abstract:

    A novel nondestructive testing methodology is proposed for online monitoring health and for in situ determination of the Fatigue life of a component. This method only requires the determination of ...

  • on the anelasticity and Fatigue fracture entropy in high cycle Metal Fatigue
    Materials & Design, 2015
    Co-Authors: M. Liakat, Michael M. Khonsari
    Abstract:

    Abstract The concept of thermodynamic entropy generation in a degradation process is utilized to study the high-cycle Fatigue of medium carbon steel 1018. Uniaxial tension–compression Fatigue tests are carried out with tubular dogbone specimens at different stress levels and loading frequencies. It is shown that a phase lag between the stress and the strain caused by the internal friction includes a considerable amount of non-damaging anelastic energy in a hysteresis loop when the amplitude of cyclic load is substantially smaller than the yield strength of the material. A methodology is proposed to determine the anelastic energy associated with Metal Fatigue at a stress level lower than the yield strength of a material. Finite element simulations are carried out with a 3-D model of the specimen to determine the validity of the proposed methodology. The evolutions of the plastic strain energy and temperature are discussed and utilized to calculate the entropy accumulation. It is shown that the accumulation of entropy generation in the HCF of the material—beginning with a pristine specimen and ending at Fatigue fracture—is nearly constant within the experimental and loading conditions considered. The concept of tallying entropy is useful for the prediction of the Fatigue life evolution of a material undergoing cyclic loading.

  • Entropic characterization of Metal Fatigue with stress concentration
    International Journal of Fatigue, 2015
    Co-Authors: M. Liakat, Michael M. Khonsari
    Abstract:

    Abstract The accumulation of thermodynamic entropy generation in a Fatigue degradation process, beginning with a pristine specimen and ending at fracture, is referred to as the Fatigue fracture entropy (FFE). In this paper, the concept of FFE is applied to study the effect of stress concentration on Metal Fatigue. Experiments involve uniaxial tension–compression Fatigue tests carried out with solid cylindrical un-notched and V-notched specimens made of both medium-carbon steel 1045 and aluminum 6061. Finite element simulations are also performed with both types of specimens to study their thermal response under cyclic load and to predict the corresponding FFE. Experimental and theoretical results show that the FFE of these materials are nearly constant for each type of the specimens. Under the conditions tested the presence of stress concentration is shown to reduce the amount of hysteresis energy generation in the specimen gage section compared to the un-notched specimen under the identical loading conditions. Also shown is that the FFE decreases significantly due to the presence of stress concentration. An empirical correlation is proposed that can predict the Fatigue life of a V-notched specimen based on the hysteresis energy per cycle and the FFE of an un-notched specimen. Predicted and experimental Fatigue lives of V-notched specimens are found to be in good agreement.

Pierre Orvegren - One of the best experts on this subject based on the ideXlab platform.

  • Sheet Metal Fatigue near nuts welded to thin sheet structures
    International Journal of Fatigue, 2008
    Co-Authors: Jonas W. Ringsberg, Pierre Orvegren, Hans-fredrik Henrysson, Gunnar Åkerström
    Abstract:

    One of the Fatigue design processes of a car body is stress-based sheet Metal Fatigue near nuts welded to thin sheets (weld nuts). In this investigation, the influence from nut geometry and dimension, as well as sheet material and thickness on sheet Metal Fatigue life was studied by Fatigue experiments and numerical analyses. The Fatigue experiments were force-controlled and carried out on a weld nut specimen which, during the reversed loading that was applied, was designed to result in bending Fatigue loading conditions of the sheet Metal near the weld nut. The results from the experiments were Fa–N curves for various combinations of nut geometry and dimension, sheet material and thickness. Numerical analyses of the experiments were carried out by linear elastic finite element (FE) analyses, in order to transform the Fa–N curves to Wohler (sig_a–N) curves. A simplified FE model of the weld nut, which is suitable for structural analysis of car body structures, was used. The structural stresses calculated using the FE model showed good agreement with the structural stresses calculated using an analytical model that is based on plate theory. The conclusion was that the simplified representation of the weld nut, and the mesh density used in the FE model, was appropriate for computation of the stress response near a weld nut subjected to bending Fatigue loading conditions. Finally, ra–N curves were computed for each weld nut configuration using its experimental data set. A sig_a–N curve fitted to all data sets resulted in the relation sig_a = 9888N^0.312. The sig_a–N curves for the 21 weld nut configurations tested were gathered within a factor of three in Fatigue life from this curve.