scholarly journals Pitting process visualization

2010 ◽  
Vol 58 (5) ◽  
pp. 57-66
Author(s):  
Michal Černý ◽  
Josef Filípek ◽  
Roman Požár
Keyword(s):  
Fatigue Damage ◽  
Development Process ◽  
Gear Tooth ◽  
Plastic State ◽  
Time Domain Simulation ◽  
Damage Development ◽  
Process Visualization ◽  
Micro Cracks ◽  
Tooth Sample ◽  
Material Volume

The paper describes time-domain simulation of gear pitting damage using animation program. Key frames have been used to create illusion of motion. The animation uses experimental results of high-cycle fatigue of material. The fatigue damage occurs in the nominal creep area on the side of the gear tooth sample loaded with variable-positioned Hertz pressure. By applying the force, the pressure cumulates between two convex surfaces. This phenomenon results in material damage under of curved surfaces in contact. Moreover, further damage has been registered on the surface. This is due to exceeding the elastic-plastic state limit and development of „tabs“. The tabs serve as origin of surface micro cracks powered by shear stress and enclosed grease pressure as well. This deformation and extreme pressures of Pascal law contribute to elongation and growth of the surface micro crack. Non-homogenous parts of material volume support the initialization/development of the micro cracks as well. Resulting visualization of the tooth-side fatigue damage provides clear and easy-to-understand description of the damage development process right from the micro crack initialization to the final fragmentation due to pitting degradation.

Fatigue Damage Model of Limestone Based on Dynamic Elastic Modulus Attenuation Rule

2013 ◽  
Vol 353-356 ◽  
pp. 1281-1286
Author(s):  
Kai Zhao ◽  
Zhi Ming Han ◽  
Xing Wang Yang
Keyword(s):  
Elastic Modulus ◽  
Fatigue Damage ◽  
Damage Model ◽  
Test System ◽  
Dynamic Elastic Modulus ◽  
Damage Development ◽  
Micro Cracks ◽  
As Stress ◽  
Two Stages ◽  
Compressive Tests

For exploring the attenuation law of limestone dynamic elastic modulus (DEM) under fatigue cyclic loading, 24 limestone specimens were used to conduct dynamic uniaxial cyclic compressive tests under different loading frequencies and stress amplitudes on MTS Test System. The tests results confirmed that the decrease of DEM goes through three different stages with the increase of cyclic numbers. And, there is no distinct correlation between three-stage evolution rule of DEM and frequencies as well as stress amplitudes. The degeneration of DEM is caused by accumulation of micro-cracks and damage increase in rock specimen. Thus, based on attenuation rule of DEM, a fatigue damage evolution model which can depict the first two stages of limestone fatigue damage development was proposed.

Analysis of Uncertainties in the Estimation of Fatigue Damage in Maritime Structures by the Bootstrap Technique

2010 ◽  
Author(s):  
Antonio Vasconcelos ◽  
Edison Castro Prates de Lima ◽  
Lui´s Volnei Sudati Sagrilo
Keyword(s):  
Standard Deviation ◽  
Fatigue Damage ◽  
Time Domain ◽  
Structural Damage ◽  
Time Domain Analysis ◽  
Relevant Information ◽  
Time Domain Simulation ◽  
Random Loading ◽  
Bootstrap Technique ◽  
Bootstrap Methodology

This work describes the application of the Bootstrap technique to assess relevant information about the structural damage due to the action of a random loading time domain simulation. The Bootstrap methodology allows the estimation of the standard deviation confident interval calculated over a single time domain analysis. Two numerical applications are presented to exemplify the using of the confident intervals to obtain information on the cumulative damage of a structure subject to these random loadings.

scholarly journals Analysis of Flexural Fatigue Damage in Woven Glass-Polyester Composites

1997 ◽  
Vol 6 (2) ◽  
pp. 096369359700600 ◽  
Author(s):  
R. Elleuch ◽  
A. Chateauminois ◽  
Ch. Bradai
Keyword(s):  
Quantitative Analysis ◽  
Fatigue Damage ◽  
Fatigue Behaviour ◽  
Fiber Bundles ◽  
Flexural Fatigue ◽  
Three Point Bending ◽  
Micro Cracks ◽  
Polyester Composite ◽  
Longitudinal Fiber ◽  
Polyester Composites

The monotonic and fatigue behaviour of a woven glass/polyester composite has been investigated under three-point bending conditions. Microscopic observations of the fatigue specimens revealed that the damage was mainly related to the early nucleation of transverse micro-cracks and delaminations along the longitudinal fiber bundles. From the quantitative analysis of the length and the orientation of these defects, it was possible to derive a lifetime criterion which was associated to a transition in damage mechanisms.

Analytical approximations to damaged gear tooth transmission-error contributions for gear-health monitoring

2015 ◽  
Vol 230 (7-8) ◽  
pp. 1157-1182 ◽  
Author(s):  
William D Mark
Keyword(s):  
Fatigue Damage ◽  
Gear Tooth ◽  
Transmission Error ◽  
Generic Model ◽  
Model Framework ◽  
Bending Fatigue ◽  
New Methods ◽  
Analytical Approximations ◽  
Significant Damage ◽  
Higher Harmonic

A generic model of transmission-error contributions arising from gear-tooth damage is developed. Damage is modeled as material removed from tooth-working-surfaces. Regions of modeled tooth damage are of limited size as in pitting damage or are extended to full working surfaces as in tooth-bending-fatigue damage. Results are computed for a wide variety of damage forms and formulated for any collection of teeth experiencing damage. Final results are expressed as transmission-error rotational-harmonic amplitudes arising from damage. Rotational-harmonic regions experiencing significant damage contributions from pitting/spalling damage and from tooth-bending-fatigue damage are delineated. Increases in higher harmonic-number amplitudes arising from transmission-error discontinuities are formulated. The overall model framework can be used to explain and interpret observed features of gear transmission-error spectra arising from gear-tooth damage and to develop new methods of detecting and assessing the severity of such damage.

Fatigue Damage Evaluation in CFRP Woven Fabric Composites Through Dynamic Modulus Measurements

2004 ◽  
Author(s):  
Hideaki Kasano ◽  
Osamu Hasegawa ◽  
Chiaki Miyasaka
Keyword(s):  
Fatigue Damage ◽  
Material Properties ◽  
Elastic Moduli ◽  
Fatigue Loading ◽  
Damage Function ◽  
Fatigue Tests ◽  
Woven Fabric ◽  
Damage Development ◽  
Dynamic Elastic Moduli ◽  
Number Of Cycles

Advanced fiber reinforced composite materials offer substantial advantages over metallic materials for the structural applications subjected to fatigue loading. With the increasing use of these composites, it is required to understand their mechanical response to cyclic loading [1–4]. Our major concern in this work is to macroscopically evaluate the damage development in composites during fatigue loading. For this purpose, we examine what effect the fatigue damage may have on the material properties and how they can be related mathematically to each other. In general, as the damage initiates in composite materials and grows during cyclic loading, material properties such as modulus, residual strength and strain would vary and, in many cases, they may be significantly reduced because of the progressive accumulation of cracks. Therefore, the damage can be characterized by the change in material properties, which is expected to be available for non-destructive evaluation of the fatigue damage development in composites. Here, the tensiontension fatigue tests are firstly conducted on the plain woven fabric carbon fiber composites for different loading levels. In the fatigue tests, the dynamic elastic moduli are measured on real-time, which will decrease with an increasing number of cycles due to the degradation of stiffness. Then, the damage fimction presenting the damage development during fatigue loading is determined from the dynamic elastic moduli thus obtained, from which the damage function is formulated in terms of a number of cycles and an applied loading level. Finally, the damage function is shown to be applied for predicting the remaining fifetime of the CFRP composites subjected to two-stress level fatigue loading.

Local forming of gears by indentation of sheets

2016 ◽  
Vol 232 (5) ◽  
pp. 838-847 ◽  
Author(s):  
Peter Sieczkarek ◽  
Sebastian Wernicke ◽  
Christian Weddeling ◽  
Paulo AF Martins ◽  
A Erman Tekkaya
Keyword(s):  
Analytical Model ◽  
Gear Tooth ◽  
Sheet Thickness ◽  
The Finite Element Method ◽  
Indentation Force ◽  
Plane Strain Deformation ◽  
Line Theory ◽  
Plane Direction ◽  
Residual Strains ◽  
Material Volume

The aim and objectives of this article are to provide an analytical model for the incremental forming of gears along the direction perpendicular to the sheet thickness. The model allows determining the influence of the major process parameters in the indentation force and in the material volume undergoing plastic deformation during indentation by means of double-wedge gear tooth punches. Special emphasis is placed on the influence of superimposing tension stresses along the in-plane direction. The analytical model is built upon the slip-line theory under plane strain deformation conditions, and results are compared against those obtained from experiments in DC04 mild steel and from numerical simulations performed with the finite element method. Results show that the indentation force can be significantly reduced by stress superposition, and that a minimum distance from previous indentations is necessary to produce a new gear tooth in a material free from residual strains and stresses.

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