Search results for "Fatigue limit"
showing 10 items of 25 documents
Creep and damage accumulation in orthotropic composites under cyclic loading
1998
Experimental results and theoretical prediction of the response of glassfiber-reinforced polyester under quasi-static, static (creep), and cyclic (fatigue) loading are presented. The nonlinear strain component at static loading and the strain amplitude rate at cyclic off-axis loading of an orthotropic composite are shown to follow the associated flow rule with a single-parameter quadratic potential function. The influence of fatigue damage on deformation is considerable due to the reduction in the elastic modulus of the composite and is apparently negligible with respect to its effect on the parameters of the creep kernel.
Model of delamination propagation in brittle-matrix composites under cyclic loading
2001
A model of interlaminar fatigue crack growth based on damage accumulation ahead of the crack is proposed. Linear cumulative assumption is used for damage estimation, and a quadratic failure criterion is applied for complex interlaminar loading. Model parameters are determined from mode I and mode II fatigue tests, and used to predict mixed-mode delamination propagation rate. Comparison of theoretical prediction with mixed-mode test results for different brittle graphite FRP at several mode- and load ratios show reasonable agreement.
Damage accumulation under variable amplitude loading of welded medium- and high-strength steels
2004
Abstract The paper presents the calculation of cumulative damage for two types of welded joints (butt weld and transverse stiffeners) of four steels (medium to high strength): S355N, S355M, S690Q and S960Q. This calculation is based on experimental data obtained under axial loading and bending with constant and variable amplitudes (Gaussian distribution and Gauss with overload spectrum). The experiments were performed under fully reversed ( R =−1) and pulsating ( R =0) loading. The fatigue life is calculated using the modifications of the Palmgren–Miner–Original rule, according to the Palmgren–Miner–Elementary method, as well as to Haibach’s suggestion. The fatigue life does not depend on t…
A theoretical and experimental study to point out the notion of loading mode in damage mechanicsApplication to the identification and validation of a…
2002
A model of fatigue-induced intralaminar cracking in strongly anisotropic laminates is presented. The features of the microscopic phenomenon are explicitly taken into account at the macroscopic level by the use of two variables, which define a new concept in Damage Mechanics that results not only in a coherent model of crack density evolution, but also in a coherent treatment of damage deactivation. Damage evolution indeed is strongly dependent on the local loading mode in each ply where cracking occurs. Experiments on complex lay-ups provided sufficient data for complete calibration of the model. These tests also allowed to validate the theoretical choice of the damage variable. Finally, nu…
Modeling the Fatigue Damage Evolution in Welded Joints
2017
The present paper presents a two-phase model for the fatigue damage evolution in welded steel joints. The argument for choosing a two-phase model is that crack initiation and subsequent crack propagation involve different damage mechanisms and should be treated separately. The crack initiation phase is defined as the number of cycles to reach a crack depth of 0.1 mm. This phase is modelled based on the Dang Van multiaxial stress approach. Both a multiaxial stress situation introduced by the acting loads and the presence of the multiaxial welding residual stresses are accounted for. The local notch effect at the weld toe becomes very important and the irregular weld toe geometry is character…
Fatigue Design of Roller Bearing for Large FPSO Turrets
2012
The present report presents the fatigue design and a fatigue life prediction method for large roller bearings applied in the turret turn table for large Floating Production Storage and Offloading (FPSO) units. The contact point between wheel and rail in these bearings is subjected to a multi-axial stress situation and both surface wear and fatigue cracking may occur. Stress analyses with contact elements are carried out and a methodology based on the Dang Van fatigue criterion is adopted. The criterion is based on an equivalent stress defined as a combination of the fluctuation of the shear stress from its mean value and the associated hydrostatic stress at a critical plane at any time. The…
In-Vitro Investigation of Fatigue and Fracture Behavior of Transmucosal versus Submerged Bone Level Implants Used in Fixed Prosthesis
2021
Background: The present in vitro study aimed to investigate the fatigue performance of different dental fixtures in two different emergence profiles. Biological failures are frequently reported because the problem canonly be solved by replacing a failing implant with a new one. Clinicians addressed minor mechanical failures, such as bending, loosening or the fracture of screws, abutment, or the entire prosthesis, by simply replacing or fixing them. Methods: Transmucosal and submerged bone-level dental implants underwent fatigue strength tests (statical and dynamical performance) by a standardized test: UNI EN ISO 14801:2016. Two types of emergence profiles (Premium sub-crestal straight impl…
Enhancement of Static and Fatigue Strength of Short Sisal Fiber Biocomposites by Low Fraction Nanotubes
2021
AbstractThanks to good mechanical performances, high availability, low cost and low weight, the agave sisalana fiber allows to obtain biocomposites characterised by high specific properties, potentially very attractive for the replacement of synthetic materials in various industrial fields. Unfortunately, due to the low strength versus transversal damage processes mainly related to the matrix brittleness and/or to the low fiber/matrix adhesion, the tensile performance of random short fiber biocomposites are quite low, and to date most of the fiber treatments proposed in literature to improve the fiber-matrix adhesion, have not led to very satisfactory results. In order to overcome such a dr…
Modelling of thermal stresses in bearing steel structure generated by electrical current impulses
2018
This work is the study of one particular candidate for white etching crack (WEC) initiation mechanism in wind turbine gearbox bearings: discharge current impulses flowing through bearing steel with associated thermal stresses and material fatigue. Using data/results from previously published works, the authors develop a series of models that are utilized to simulate these processes under various conditions/local microstructure configurations, as well as to verify the results of the previous numerical studies. Presented models show that the resulting stresses are several orders of magnitude below the fatigue limit/yield strength for the parameters used herein. Results and analysis of models …
Relations between cavitation erosion resistance of materials and their fatigue strength under random loading
1999
Abstract The paper contains results of tests on fatigue strength under uniaxial random loading and cavitation erosion resistance for three steels: 10HNAP, 18G2A and 15G2ANb. The obtained fatigue and cavitation characteristics were used for determination of relations between these two phenomena. From the analysis it appears that there is correlation between fatigue strength of the material under random loading and its cavitation erosion resistance. It has been shown that fatigue tests under random loading and tests on cavitation erosion of 10HNAP, 18G2A and 15G2ANb steels may be described with a mathematical model of the same type. It has been also found that there is a linear relation, in t…