Obtaining Creep Compliance Parameters Accurately from Static or Cyclic Creep Tests

2008 ◽  
pp. 179-179-21
Author(s):  
J Kim ◽  
R Roque ◽  
B Birgisson
Keyword(s):  
Creep Compliance ◽  
Cyclic Creep ◽  
Creep Tests

Obtaining Creep Compliance Parameters Accurately from Static or Cyclic Creep Tests

2005 ◽  
Vol 2 (8) ◽  
pp. 12263 ◽  
Author(s):  
J Kim ◽  
R Roque ◽  
B Birgisson
Keyword(s):  
Creep Compliance ◽  
Cyclic Creep ◽  
Creep Tests

Effect of Cure State on Stress Relaxation in 3501-6 Epoxy Resin

1997 ◽  
Vol 119 (3) ◽  
pp. 262-265 ◽  
Author(s):  
S. R. White ◽  
A. B. Hartman
Keyword(s):  
Stress Relaxation ◽  
Epoxy Resin ◽  
Creep Compliance ◽  
Numerical Technique ◽  
Matrix Material ◽  
Relaxation Modulus ◽  
Master Curves ◽  
Creep Tests ◽  
Three Point Bending ◽  
Direct Inversion

Little experimental work has been done to characterize how the viscoelastic properties of composite material matrix resins develop during cure. In this paper, the results of a series of creep tests carried out on 3501–6 epoxy resin, a common epoxy matrix material for graphite/epoxy composites, at several different cure states is reported. Beam specimens were isothermally cured at increasing cure temperatures to obtain a range of degrees of cure from 0.66 to 0.99. These specimens were then tested in three-point bending to obtain creep compliance over a wide temperature range. The master curves and shift functions for each degree of cure case were obtained by time-temperature superposition. A numerical technique and direct inversion were used to calculate the stress relaxation modulus master curves from the creep compliance master curves. Direct inversion was shown to be adequate for fully cured specimens, however it underpredicts the relaxation modulus and the transition for partially cured specimens. Correlations with experimental stress relaxation data from Kim and White (1996) showed that reasonably accurate results can be obtained by creep testing followed by numerical conversion using the Hopkins-Hamming method.

Creep relaxation and fully reversible creep of foam core sandwich composites in seawater

2015 ◽  
Vol 24 (5-6) ◽  
pp. 187-194
Author(s):  
Ismael de la Paz ◽  
Basir Shafiq
Keyword(s):  
Strong Dependence ◽  
Cyclic Creep ◽  
Foam Core ◽  
Sandwich Composites ◽  
Creep Tests ◽  
Modes Of Failure ◽  
Service Lifetime ◽  
Interface Cell ◽  
Reversed Loading ◽  
Creep Loading

AbstractFoam core sandwich composites were subjected to (i) creep to failure, (ii) cyclic creep-relaxation and (iii) fully reversible cyclic creep loading in seawater in order to mimic an actual ship hull’s service lifetime scenario. The results indicate a strong dependence of lifetime on the mode of loading. A significant reduction in the overall life was observed under cyclic creep as compared with the conventional creep to failure. Creep relaxation (R=1) tests were performed at loading-relaxation periods of 24/24, 24/12, 24/6, 12/12 and 6/6 h, while the fully reversible (R=-1) creep tests were conducted at loading-reversed loading times of 36/36, 24/24, 12/12, 6/6, and 3/3 h. The results suggest that creep-relaxation lifetime characteristics depend predominantly on the relaxation time as opposed to loading times, i.e. longer relaxation periods lead to shorter life. Whereas, fully reversible creep appears to be dependent upon the number of reversals whereby, life is observed to reduce as the number of reversals increase. These significant observations are explained in terms of various possible paths to interface cell wall collapse. Modes of failure were predominantly indentation and core compression in the vicinity of the loading site.

Creep Fatigue Interactions in a 1 CrMo V Steel

1976 ◽  
Vol 190 (1) ◽  
pp. 319-330 ◽  
Author(s):  
E.G. Ellison ◽  
A.J.F. Paterson
Keyword(s):  
Plastic Strain ◽  
High Strain ◽  
Creep Behaviour ◽  
Creep Damage ◽  
Cyclic Creep ◽  
Creep Data ◽  
Creep Tests ◽  
Brittle Transition ◽  
Creep Fatigue ◽  
Cyclic Plastic Strain

Static and cyclic creep tests have been carried out on a 1 Cr Mo V steel at 565 °C. In addition, the effects of prior high strain fatigue on subsequent creep behaviour has been studied. A well defined ductile/brittle transition was noted which was unaffected by the type of load controlled cycle. The material softened under cyclic plastic strain and no experimental evidence was obtained which indicated that fatigue and creep damage interacted in a load controlled test to give rise to unexpectedly short lives. The conclusion derived is that “softened creep” data should be used in predictions of deformation and rupture behaviour, and that the use of virgin creep data can give rise to substantial errors.

Experimental and Numerical Study of Cyclic Creep of Cast Magnesium Alloy at High Temperature

2008 ◽  
Vol 33-37 ◽  
pp. 421-428
Author(s):  
Xiang Guo Zeng ◽  
Zhan Hua Gao ◽  
Jing Hong Fan ◽  
Hua Yan Chen
Keyword(s):  
High Temperature ◽  
Magnesium Alloy ◽  
Numerical Study ◽  
Cyclic Creep ◽  
Damage Parameter ◽  
Creep Tests ◽  
Proposed Model ◽  
Cast Magnesium Alloy ◽  
Creep Constitutive Model ◽  
Cast Magnesium

The cast magnesium alloys as AM50 offer a good strength, ductility and surface finish for automotive industry. But the poor creep resistance limited its application to power components such as engine and transmission cases at temperatures in excess of 100°C. In order to investigate the cyclic creep behavior of Magnesium Alloy at high temperature, creep tests of plate specimens AM50 were conducted in this work. Based on the analysis about the microstructure and defects of AM50 under the condition of cyclic creep, a cyclic creep constitutive model with isotropic and scalar damage parameter was developed. Furthermore, the proposed model was experimentally verified by analyzing the cyclic creep and recovery response of Cast Magnesium alloy under cyclic loading with dwell time. Comparisons between calculated results and experimental data showed good agreement.

STRAIN RATE–DEPENDENT BEHAVIOR OF UNCURED RUBBER: EXPERIMENTAL INVESTIGATION AND CONSTITUTIVE MODELING

2022 ◽  
Author(s):  
Sanghyeub Kim ◽  
Thomas Berger ◽  
Michael Kaliske
Keyword(s):  
Strain Rate ◽  
Evolution Equations ◽  
Cyclic Creep ◽  
Tensile Tests ◽  
Internal Variables ◽  
Creep Tests ◽  
Rate Dependent ◽  
Nonlinear Viscosity ◽  
Dependent Behavior ◽  
Building Process

ABSTRACT The strain rate dependence of uncured rubber is investigated through a series of tensile tests (monotonic, multistep relaxation, cyclic creep tests) at different strain rates. In addition, loading/unloading tests in which the strain rate is varied every cycle are carried out to observe their dependence on the deformation history. A strain rate–dependent viscoelastic–viscoplastic constitutive model is proposed with the nonlinear viscosity and process-dependent recovery properties observed in the test results. Those properties are implemented by introducing evolution equations for additional internal variables. The identified material parameters capture the experiments qualitatively well. The proposed model is also evaluated by finite element simulations of the building process of a tire, followed by the in-molding.

Viscoelastic Response of Closed-Cell Polyurethane Foams From Half Hour-Long Creep Tests: Identification of Lomnitz Behavior

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Christian Pichler ◽  
Marcus Maier ◽  
Roman Lackner
Keyword(s):  
Creep Compliance ◽  
Polyurethane Foams ◽  
Elastic Compliance ◽  
Velocity Measurements ◽  
Creep Tests ◽  
Viscous Material ◽  
Material Parameters ◽  
Static Creep ◽  
Closed Cell ◽  
Logarithmic Type

In this paper, a protocol for interpretation of static creep tests on closed-cell polyurethane foams is defined, considering the influence of a finite loading duration when identifying creep compliance parameters. Experiments were conducted at isothermal conditions with temperatures ranging from 20 to 120 °C. The experimental results indicate Lomnitz, i.e., logarithmic-type creep behavior. We discuss uniqueness of the backcalculated parameters. Furthermore, the viscoelastic material parameters obtained were verified in independent experiments: elastic compliance by ultrasonic wave velocity measurements, viscous material parameters by relaxation tests.

Time-Temperature-Stress Equivalence Applied to Accelerated Characterization of Creep Behavior of Viscoelastic Polymer

2007 ◽  
Vol 353-358 ◽  
pp. 1386-1389 ◽  
Author(s):  
Rong Guo Zhao ◽  
Wen Bo Luo ◽  
Chu Hong Wang ◽  
Xin Tang
Keyword(s):  
Temperature Stress ◽  
Stress Level ◽  
Creep Compliance ◽  
Superposition Principle ◽  
Test Duration ◽  
Nonlinear Creep ◽  
Creep Tests ◽  
Test Technique ◽  
Compliance Curve ◽  
Stress Superposition

Temperature induced change, and stress induced change as well, in intrinsic timescale were investigated by nonlinear creep tests on poly(methyl methacrylate). With four different experimental temperatures, from 14 to 26 degrees centigrade, time-dependent axial elongations of the specimen were measured at seven different stress levels, from 14 MPa to 30 MPa, and modeled according to the concept of time-temperature-stress equivalence. The test duration was only 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to the time-temperature superposition principle (TTSP), the time-stress superposition principle (TSSP) and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about two-year at a reference temperature 14 degrees centigrade and a reference stress 14 MPa was constructed by shifting the creep curves horizontally along the logarithmic time axis using shift factors. It is shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of PMMA specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level.

scholarly journals From Complex Modulus E* to Creep Compliance D(t): Experimental and Modeling Study

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1945
Author(s):  
Abdeldjalil Daoudi ◽  
Daniel Perraton ◽  
Anne Dony ◽  
Alan Carter
Keyword(s):  
Tensile Test ◽  
Creep Compliance ◽  
Complex Modulus ◽  
Tensile Tests ◽  
Direct Compression ◽  
Creep Tests ◽  
Indirect Tensile Test ◽  
2S2p1d Model ◽  
Indirect Tensile ◽  
Direct Tensile

Creep compliance (D(t)) is a very important input for the thermal cracking resistance in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The aim of the work presented here is to predict the results of creep compliance D(t) from the result of complex modulus E*(ω). The work plan is divided in two main parts: an experimental part consisting of creep tests, and a modeling part. Three configurations were compared together, namely direct tensile, direct compression and indirect tensile tests. The modelling part consists of using a 2S2P1D model coupled to Kopelman approximation to switch from the frequency domain to the time domain. Additionally, 2S2P1D was used to calibrate the generalized Kelvin–Voigt model and get the creep compliance directly from E* results. The experimental results show that D(t) from direct tensile and direct compression are the same in the viscoelastic domain and are greater than D(t) from the indirect tensile test. The indirect tensile test (IDT) seems to be very difficult to achieve compared to the other two variants. The converted results using the 2S2P1D model coupled to Kopelman approximation and the results from the GKV model describe the experimental points very well.

Effect of stress levels on compressive low-cycle fatigue behaviour of softwood

Holzforschung ◽  
2005 ◽  
Vol 59 (6) ◽  
pp. 662-668 ◽  
Author(s):  
Meng Gong ◽  
Ian Smith
Keyword(s):  
Mathematical Model ◽  
Creep Strain ◽  
Stress Level ◽  
Low Cycle Fatigue ◽  
Total Duration ◽  
Peak Stress ◽  
Cyclic Creep ◽  
Cycle Fatigue ◽  
Creep Tests ◽  
Stress Levels

Abstract Low-cycle fatigue (LCF) of spruce under parallel-to-grain compression was investigated to simulate the damage that occurs during extreme events such as hurricanes. Load control was used, with peak stress levels of 75%, 85% and 95% of static compressive strength (C max). Changes in the residual cyclic modulus, cyclic creep strain and modified work density were correlated with the number of load cycles to assess their suitability as damage indicators. Creep tests were also carried out and the strain compared with cyclic creep strain under LCF load. Fatigue and creep tests had a total duration of 10 min. A three-element mathematical model was used to predict the cyclic creep strain. Some key findings were that: (1) the residual cyclic modulus varies with the number of load cycles at a given stress level and decreases with an increase in stress level; (2) cyclic creep strain and pure creep strain are strongly influenced by the peak stress level; and creep specimens fail but fatigue specimens do not at a 95% peak stress level; and (3) the three-element mathematical model is appropriate for predicting cyclic creep strain.

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