A Three Dimensional Graphical Aid for Fatigue Data Analysis

2011 ◽  
Vol 488-489 ◽  
pp. 755-758 ◽  
Author(s):  
Bruno Atzori ◽  
Giovanni Meneghetti ◽  
Mauro Ricotta
Keyword(s):  
Experimental Data ◽  
Data Analysis ◽  
Three Dimensional ◽  
Strain Curve ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Compatibility Conditions ◽  
Stress Strain ◽  
Fatigue Data ◽  
Best Fitting

The fatigue behaviour of materials is usually synthesised in terms of stress-life (S-N) curve or in terms of strain-life (e-N) curve, the latter being described by the so-called Manson-Coffin equation. It is known that the assumption of equality of the plastic and elastic components between the Manson-Coffin and the stabilised stress-strain curves leads to the so-called compatibility conditions which connect the equations theoretically. The material constants of the Manson-Coffin and of the stabilised stress-strain curve are commonly determined by best fitting separately the experimental data obtained from strain-controlled fatigue tests. As a consequence the compatibility conditions may not be fulfilled. In this paper a method for fatigue data analysis that ensures the compatibility conditions is proposed and validated against experimental data.

Stress-strain curve of paper revisited

2012 ◽  
Vol 27 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Svetlana Borodulina ◽  
Artem Kulachenko ◽  
Mikael Nygårds ◽  
Sylvain Galland
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Failure Behavior ◽  
Three Dimensional Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Bonding Parameters ◽  
Particle Level ◽  
The Impact

Abstract We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

Elastomer Behavior IV. Loop Structure of Elastomer Networks

1966 ◽  
Vol 39 (5) ◽  
pp. 1489-1495
Author(s):  
L. C. Case ◽  
R. V. Wargin
Keyword(s):  
Experimental Data ◽  
Crosslink Density ◽  
Strain Curve ◽  
Uniaxial Stress ◽  
Polymer Chains ◽  
Theoretical Treatment ◽  
Loop Structure ◽  
Stress Strain ◽  
Strain Behavior ◽  
Selection Of

Abstract A new theoretical treatment strongly indicates that an elastomer network actually consists of a system of fused, closed, interpenetrating loops of polymer chains. This interpenetrating loop structure restricts the movement of the chains and thereby affects the stress-strain behavior of the elastomer. Methods have been developed to enable the calculation of the number of effective crosslinks caused by loop interpenetrations (virtual crosslinks). The uniaxial stress-strain behavior of an elastomer predicted using our methods can be fitted almost perfectly to published experimental data by proper selection of chain parameters. Previous theoretical treatments gave only a qualitative fit to the experimental data for the stress-strain behavior of elastomers and were not capable of predicting the correct shape of the experimental stress-strain curve. The present treatment gives a nearly perfect fit for both stress as a function of strain at constant crosslink density, and stress as a function of crosslink density at constant strain, and thus represents a vast improvement.

Cyclic and High Strain Behavior of Titanium Alloys Used for Riser Components

2008 ◽  
Author(s):  
C. F. G. Baxter
Keyword(s):  
Stress Relaxation ◽  
Titanium Alloys ◽  
Elevated Temperatures ◽  
Fatigue Testing ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
Fatigue Data ◽  
Stress Ratios

Grades 23 and 29 titanium alloys are becoming more commonly used offshore for critical components of riser systems. Many of these components, such as compact flanges, operate at high mean strains due to make-up loads, often close to or above yield. Hitherto, weld fatigue data collected at low mean strains have been used for prediction of fatigue lives of such components. However, these analyses have resulted in short but adequate lives. The objective of this work was, therefore, to derive fatigue data that could be applied to components operating at high strains and over a large range of stress ratios. This necessitated strain-controlled fatigue testing. Cyclic material properties evaluated from the tests are presented. In addition, it was found that sustained strain load, a type of stress relaxation that, unlike normal stress relaxation, does not require elevated temperatures, affected the cyclic behavior It also affects the distribution of make up stresses. This phenomenon was also investigated and it was shown that the cyclic stress/strain curve, readily derived from strain-controlled fatigue tests, accounted for sustained strain load effects.

Stress Strain Testing of the Strand of E-Glass Fibers

2008 ◽  
Vol 39-40 ◽  
pp. 165-168
Author(s):  
Mária Chromčíková ◽  
Marek Liška
Keyword(s):  
Experimental Data ◽  
Fiber Strength ◽  
Glass Fibers ◽  
Length Distribution ◽  
Continuous Distribution ◽  
Strain Curve ◽  
Young Modulus ◽  
Strength Distribution ◽  
Stress Strain ◽  
Strain Testing

The mathematical model of the stress-strain curve of the strand of glass fibers was proposed and applied on the experimental data obtained for E glass fibers. The model reflects the lognormal continuous distribution of the unstrained lengths of glass fibers and the Weibull distribution of the fibers strength. The regression treatment of experimental data provided the statistically robust estimates of the parameters of the lognormal length distribution, of the Young modulus, and of the parameters of the Weibull glass fibers strength distribution. It was shown that neglecting of the continuous unstrained length distribution leads to serious errors in estimates of the fiber strength distribution.

scholarly journals The Experimental Studies on Behavior of Ultrahigh-Performance Concrete Confined by Hybrid Fiber-Reinforced Polymer Tubes

2015 ◽  
Vol 2015 ◽  
pp. 1-18 ◽  
Author(s):  
Zong-cai Deng ◽  
Jiu-ling Qu
Keyword(s):  
Ultimate Strength ◽  
Experimental Studies ◽  
Strain Curve ◽  
Stress Strain ◽  
Explosive Failure ◽  
Linear Strengthening ◽  
Best Fitting ◽  
Reasonable Prediction ◽  
Frp Tube ◽  
Better Than

This paper conducts axial compression test of ultrahigh performance concrete- (UHPC-) filled hybrid FRP (HFRP) tubes, using the alternating hybrid technology to improve the deformation capacity of FRP tube and measure the axial compressive responses of ultimate strength, strains, and stress-strain curve of confined specimens. The test results show that the local rupture of HFRP tubes did not lead to explosive failure of UHPC cylinder, and its ductility is better than that of UHPC confined by only one type of FRP tube; HFRP tube can effectively improve the compressive strength and ultimate strain of UHPC specimens; the stress-strain curves divide into three distinct regions: linear phase, transition phase, and linear strengthening phase. None of the models provided a reasonable prediction for strength and strain of HFRP-confined UHPC specimen; therefore, a new ultimate strength and strain perdition model considering the confinement effectiveness of different hybrid FRP series was proposed. The new proposed model presented the best fitting results. The stress-strain responses predicted by the existing models are all below the experimental curves; therefore, a new three-stage constitutive model was proposed, which relatively fits the test curves better than the existing models.

scholarly journals Identification of Fatigue Constants by Means of 3D Method

2016 ◽  
Vol 66 (2) ◽  
pp. 107-116
Author(s):  
Dagmar Ličková ◽  
Radim Halama ◽  
Zdeněk Poruba
Keyword(s):  
Experimental Data ◽  
Conventional Method ◽  
Fatigue Tests ◽  
Compatibility Conditions ◽  
Identification Procedure

Abstract The conventional method for evaluation of the fatigue constants uses one set of experimental data from strain-controlled uniaxial fatigue tests. However, these constants do not ensure the compatibility conditions. The new 3D method retains the mathematical and physical relationships between curves considered. This paper presents a way of implementation of the identification procedure and shows results obtained for three types of materials.

On the Tensile and Compressive Fatigue Behaviour of Notched CFRP Laminates

2008 ◽  
Vol 385-387 ◽  
pp. 241-244
Author(s):  
Giangiacomo Minak ◽  
Piero Morelli
Keyword(s):  
Experimental Data ◽  
Carbon Fiber ◽  
Compressive Loading ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Maximum Likelihood Estimates ◽  
Combined Effects ◽  
Cfrp Laminates ◽  
Carbon Fiber Epoxy ◽  
Load Conditions

This paper describes the experimental results of a set of fatigue tests performed on T300 carbon fiber / epoxy resin laminates cured in autoclave. The effects of anisotropy in laminates lay up have been investigated, as well as the influence of circular hole notches, for both the case of tensile and compressive loading conditions. Due to the high slenderness of specimens, that have the ASTM D3039 standard suggested geometry, a special gripping device has been designed in order to avoid the axial buckling. Fatigue failure probability of the material has been assessed by means of Maximum Likelihood Estimates (MLE) of the experimental data, as a function of the lay-up and load conditions. Eventually, the micrographic analysis of fractured surfaces outlined the combined effects of both the geometry and notches towards the damage behaviour of this kind of material.

Bending Fatigue Life Prediction of Fillet Rolled Crankshafts

2013 ◽  
Vol 275-277 ◽  
pp. 174-178 ◽  
Author(s):  
Ke Bao ◽  
Ri Dong Liao
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Three Dimensional ◽  
Local Stress ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Stress Strain ◽  
Bending Fatigue ◽  
Bending Strain ◽  
Stress Computation

The influence of residual stesses must be considered in bending fatigue life prediction of fillet rolling crankshafts. In this paper, the stress/strain distributions near fillet during fatigue tests are calculated by finite element method. In residual stress computation, the three dimensional flexible contact model is adopted, and in bending strain computation, the static analysis are selected. Then, bending fatigue life prediction is performed by local stress-strain approach based on the residual stess and bending strain amplitude, and the results agree with the bending fatigue test.

Procedure for the Determination of True Stress-Strain Curves From Tensile Tests With Rectangular Cross-Section Specimens

2004 ◽  
Vol 126 (1) ◽  
pp. 70-76 ◽  
Author(s):  
I. Scheider ◽  
W. Brocks ◽  
A. Cornec
Keyword(s):  
Finite Element ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Strain Curve ◽  
Tensile Tests ◽  
Tensile Specimen ◽  
True Stress ◽  
Image Correlation ◽  
Stress Strain ◽  
Three Dimensional Finite Element

The problem of determining true stress-strain curves from flat tensile specimens beyond the onset of necking has been investigated based on finite element analyses under consideration of experimental accessible data using digital image correlation (DIC). The displacement field on the specimen surface is determined by in-situ deformation field measurement. A three-dimensional finite element study with different stress-strain-curves has been carried out to develop a formula, with which it is possible to calculate the true stress subject to the strain in the necking region. The method has been used to evaluate the true stress-strain curve with a so-called micro flat tensile specimen, which is normally used to determine the material properties in the material gradient around thin weldments.

Reliability Analysis of LCF Life for a Turbine Disk

2010 ◽  
Vol 146-147 ◽  
pp. 1379-1385
Author(s):  
Yang Gao ◽  
Chang Jun Yang ◽  
Kai Lin ◽  
Qing Gao
Keyword(s):  
Reliability Analysis ◽  
Low Cycle Fatigue ◽  
Three Dimensional ◽  
Strain Curve ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Turbine Disk ◽  
Fatigue Reliability ◽  
Three Dimensional Model ◽  
Stress Strain

Cyclic stress-strain curve and cyclic strain-life curve appear distinct scatters, and the scatter of fatigue life increases with reducing of the strain levels. A methodology for reliability simulation of low cycle fatigue (LCF) life for turbine disk structures is developed in this paper. First, probabilistic cyclic stress-strain model and linear heteroscedastic probabilistic cyclic strain-life model are founded based on the fatigue test data. Second, three dimensional model of a turbine disk is built, and the fatigue reliability analysis of this turbine disk is implemented in probabilistic design module (PDS) of ANSYS by the combination of response surface method (RSM) and Monte Carlo simulation (MCS). The predicted life with reliability 0.9987 is well consistent with the technology life obtained from disks LCF tests by scatter factors method.

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