A statistical theory of time-dependent fracture for cementitious materials subjected to cyclic loading

1989 ◽  
Vol 24 (9) ◽  
pp. 3118-3122 ◽  
Author(s):  
Xiaozhi Hu ◽  
Yiu-Wing Mai ◽  
Brian Cotterell
Keyword(s):  
Statistical Theory ◽  
Cyclic Loading ◽  
Cementitious Materials ◽  
Time Dependent

A Statistical Theory of Time-Dependent Fracture for Cementitious Materials

1990 ◽  
pp. 37-46
Author(s):  
Xiao-Zhi Hu ◽  
Yiu-Wing Mai ◽  
Brian Cotterell
Keyword(s):  
Statistical Theory ◽  
Cementitious Materials ◽  
Time Dependent

A Consistent Approach for the Development of a Comprehensive Data Base of Time-Dependent Parameters for Concrete Engineered Barriers

2013 ◽  
Author(s):  
Suresh C. Seetharam ◽  
Dirk Mallants ◽  
Janez Perko ◽  
Diederik Jacques
Keyword(s):  
Data Base ◽  
Experimental Studies ◽  
Cementitious Materials ◽  
Time Dependent ◽  
Extensive Literature ◽  
Near Surface ◽  
Comprehensive Data ◽  
Engineered Barriers ◽  
Parameter Values ◽  
Consistent Approach

This paper presents a consistent approach for the development of a comprehensive data base of time-dependent hydraulic and transport parameters for concrete engineered barriers of the future Dessel near surface repository for low level waste. The parameter derivation is based on integration of selected data obtained through an extensive literature review, data from experimental studies on cementitious materials specific for the Dessel repository and numerical modelling using physically-based models of water and mass transport. Best estimate parameter values for assessment calculations are derived, together with source and expert range and their probability density function wherever the data was sufficient. We further discuss a numerical method for upscaling laboratory derived parameter values to the repository scale; the resulting large-scale effective parameters are commensurate with numerical grids used in models for radionuclide migration. To accommodate different levels of conservatism in the various assessment calculations defined by ONDRAF/NIRAS, several sets of parameter values have been derived based on assumptions that introduce different degrees of conservatism. For pertinent parameters, the time evolution of such properties due to the long-term concrete degradation is also addressed. The implementation of the consistent approach is demonstrated by considering the pore water diffusion coefficient as an example.

The Behavior of Salem Limestone in Cyclic Loading

1974 ◽  
Vol 14 (01) ◽  
pp. 19-24 ◽  
Author(s):  
S.S. Peng ◽  
E.R. Podnieks ◽  
P.J. Cain
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Material Properties ◽  
High Frequency ◽  
Low Frequency ◽  
Tensile Loading ◽  
Cyclic Stress ◽  
Time Dependent ◽  
Mean Stress ◽  
Frequency Range

Abstract Specimens of Salem limestone were loaded cyclically at a frequency of 2 cycles/sec in uniaxial cyclic compression, tension, and compression-tension. The number of cycles to failure, maximum deformation for each cycle, and load-deformation hysteresis loops were recorded. The fatigue life and fatigue limit values under cyclic compressive loading are comparable with those under cyclic tensile loading, whereas under cyclic compressive-tensile loading they are considerably lower. Introduction The study of rock behavior in cyclic loading has been relatively ignored in the past, even though certain problems in rock mechanics are closely related to cyclic loading. These problems include the effects of percussive drilling and the vibrations generated by blasting. An understanding of the mechanisms of fatigue failure in rock can be expected to help improve drilling efficiency and prevent vibration damage caused by blasting. Because of the lack of bask information on rock behavior under cyclic loading, the Federal Bureau of Mines, Twin Cities Mining Research Center began in 1968 an extensive program for studying cyclic loading effects. This program included the investigation of the behavior of rock loaded cyclically at different frequencies under varying test geometries, loading configurations, and environments. In the high-frequency range, sonic power transducers are being used to apply cyclic loading at a frequency of 10,000 Hz, and an electromagnetic shaker is being used at frequencies from 100 to 1,000 Hz. In the low-frequency range, cyclic loading of 2 to 10 Hz is applied by a closed-loop servocontrolled electrohydraulic testing machine. In each frequency range, experiments are conducted to provide the following information: fatigue limits, fatigue life, energy dissipation, temperature induced in the specimen, and the time history of load and deformation. This paper presents the first phase of be results obtained on specimens of Salem limestone loaded in the low-frequency range. The early findings on the high-frequency effects were reported separately. Recently, the effect of cyclic loading on rock behavior has been receiving more attention and considerable information is being generated. General Loading Concept in Cyclic Loading In conventional strength tests the monotonic loading program is specified by the loading rate and control mode. For cyclic loading, where the load is a periodic function of time, the problem is more complex. To evaluate such material properties as fatigue life, the load must be described systematically and concisely in terms of physically significant parameters. parameters. For a general case, one approach is to divide the cyclic stress into time-independent and time-dependent components. The time-independent component (or mean stress) is the time average of the stress. A cyclic stress with an amplitude A and zero mean can be superimposed on this loading. For the usual case of cyclic loading with steady loading conditions, the stress can be described as follows.(1)= + (t), where f(t) is a periodic function of time, t, and can be represented by a sine or sawtooth wave. Other ways of describing the stress are available such as using the maximum and minimum stresses, which are related to the mean and amplitude:(2)max = . and(3)min = . The key issue is to describe the loading in terms that will correlate with the material properties of interest. The use of amplitude and mean stress to describe cyclic loading separates the time-dependent bona the time-independent portion of the stress because the effect of each portion of the loading should be investigated separately. In analyzing the effect of cyclic loading on rock, another significant factor is the large difference between the tensile strength and the compressive strength. P. 19

TIME-DEPENDENT MECHANICAL BEHAVIOR OF CARBON BLACK FILLED ELASTOMERS

2011 ◽  
Vol 84 (3) ◽  
pp. 296-324 ◽  
Author(s):  
Aparajita Bhattacharya ◽  
Grigori A. Medvedev ◽  
James M. Caruthers
Keyword(s):  
Cyclic Loading ◽  
Stress Relaxation ◽  
Constitutive Models ◽  
Large Change ◽  
Time Dependent ◽  
Tangent Modulus ◽  
Strain Rate Effects ◽  
Damage Models ◽  
Filled Elastomers ◽  
Rate Effects

Abstract An extensive set of time-dependent mechanical data was obtained for several filled SBR elastomers, including Mullins experiments, cyclic loading experiments, and stress relaxation. These comprehensive data enable critical evaluation of three classes of constitutive models. Viscoelastic models can naturally describe the hysteresis upon loading/reloading, but are unable to capture the large change in tangent modulus between the initial loading and the modulus just as the specimen is being unloaded. Elastic-damage models can capture the large change in tangent modulus just prior versus subsequent to unloading of a virgin sample, but can only parameterize the hysteresis on cyclic loading and are unable to predict strain rate effects and stress relaxation. A viscoelastic-damage model can predict the large change in tangent modulus upon reversal of the strain, hysteresis, strain rate effects, and stress relaxation; however, viscoelastic-damage models are unable to simultaneously predict the modest amount of hysteresis observed in cyclic experiments and the large amount of stress relaxation observed after loading to large deformations. The analysis indicates that constitutive models that include different deformation mechanics than the traditional elastic, viscoelastic, and damage processes will be needed to describe the full range of mechanical behavior exhibited by carbon black filled elastomers.

Healing Ligaments Have Shorter Lifetime and Greater Strain Rate During Fatigue Than Creep at Functional Stresses

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Gail M. Thornton ◽  
Soraya J. Bailey
Keyword(s):  
Cyclic Loading ◽  
Strain Rate ◽  
Static Loading ◽  
Fatigue Loading ◽  
Cyclic Fatigue ◽  
Time Dependent ◽  
Daily Activities ◽  
Ligament Injury ◽  
Fatigue Lifetime ◽  
Creep Loading

Healing ligaments have compromised strength, which makes them susceptible to damage during daily activities at normal functional stresses. Daily activities expose ligaments to cyclic (fatigue) and static (creep) loading. A gap injury was created in the midsubstance of both hindlimb medial collateral ligaments of 40 female 1-year-old New Zealand White rabbits. After a 14-week healing interval, medial collateral ligament gap scars were exposed to long-term fatigue and creep loading over a range of functional force/stress levels. Lifetime and strain behavior were compared during fatigue and creep. The contribution of time-dependent mechanisms to fatigue lifetime was modeled using creep data. Fatigue-loaded healing ligaments had shorter lifetime, greater steady-state strain rate and greater increase in strain at 0.8 h than creep-loaded healing ligaments. The actual fatigue lifetime was less than the predicted fatigue lifetime which was derived from time-dependent damage alone, indicating an important role for cycle-dependent damage mechanisms in healing ligaments during fatigue loading. Cyclic loading decreased lifetime and increased strain rate and strain prior to rupture compared to static loading in healing ligaments. These findings suggest that, after a ligament injury, more care should be taken when exercises result in cyclic loading rather than static loading of the healing ligament even at functional stresses.

Modeling nonlinear time-dependent behaviors of synthetic fiber ropes under cyclic loading

2015 ◽  
Vol 109 ◽  
pp. 207-216 ◽  
Author(s):  
Wei Huang ◽  
Haixiao Liu ◽  
Yushun Lian ◽  
Linan Li
Keyword(s):  
Cyclic Loading ◽  
Time Dependent ◽  
Synthetic Fiber

The Effects of Environment and Fatigue on the Adhesion and Subcritical Debonding of Dielectric Polymers

1999 ◽  
Vol 565 ◽  
Author(s):  
J. M. Snodgrass ◽  
D. Pantelidis ◽  
J. C. Bravman ◽  
R. H. Dauskardt
Keyword(s):  
Thin Film ◽  
Cyclic Loading ◽  
Silicon Dioxide ◽  
Double Cantilever Beam ◽  
Time Dependent ◽  
Interface Fracture ◽  
Layered Systems ◽  
Beam Geometry ◽  
Interface Delamination ◽  
Microelectronic Processing

AbstractThe adhesion of thin film polymers will be critical in the integration of low-κ materials into microelectronic processing. This study describes the adhesion of two promising low-κ polymers (polyimide and benzocyclobutene) to a silicon dioxide surface. Critical adhesion values were measured using interface fracture mechanics samples in a double cantilever beam geometry. The effect of subcritical (time-dependent) delamination was also evaluated for these systems. Subcritical debonding data are important in understanding the effect of environment and temperature on interface reliability. To that end, experiments were conducted over a range of humidities to elucidate the effect of moisture on interface delamination. The important effect of the acceleration of debond growth rates due to cyclic loading is also described. In addition, XPS studies are presented to characterize the debond path in these layered systems.

A numerical model for the time‐dependent cracking of cementitious materials

2001 ◽  
Vol 52 (7) ◽  
pp. 637-654 ◽  
Author(s):  
G. P. A. G. van Zijl ◽  
R. de Borst ◽  
J. G. Rots
Keyword(s):  
Numerical Model ◽  
Cementitious Materials ◽  
Time Dependent
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