Overlay Tester Results from Dense-Graded Asphalt Concrete Mixes: Accuracy in Characterizing Crack Susceptibility

2017 ◽  
Vol 2631 (1) ◽  
pp. 30-38 ◽  
Author(s):  
Victor M. Garcia ◽  
Jose Garibay ◽  
Imad Abdallah ◽  
Soheil Nazarian
Keyword(s):  
Asphalt Concrete ◽  
Specimen Preparation ◽  
Progression Rate ◽  
Preparation Process ◽  
Cracking Potential ◽  
Performance Indexes ◽  
Number Of Cycles ◽  
Crack Susceptibility ◽  
Cycles To Failure ◽  
Overlay Tester

Several highway agencies have either implemented or considered implementing laboratory performance tests to estimate the cracking potential of asphalt concrete (AC) mixes during the mix design process. One such popular test, the overlay tester (OT), measures the number of cycles to failure of specimens that are caused by the repeated application of deformation. The major concern about using this test as a reliable characterization of the cracking susceptibility of AC mixes, especially for dense-graded mixtures, is the variability in the specified number of cycles to failure in the performance index. The main objective of this paper is to report a means for improving the consistency of the OT test results on dense-graded AC mixes. An assessment of a specimen preparation process that can yield more consistent results was conducted. The consistency of the traditional number of cycles to failure as well as of the load–displacement response and load reduction curves was investigated by using a modified specimen preparation process. The repeatability of alternative performance indexes, such as the critical fracture energy and crack progression rate, that can be measured from the OT test was also investigated and compared with that of the index for the number of cycles to failure. This study indicated that the raw data from the OT test seemed to be repeatable if the proposed specimen preparation process was consistently followed. Alternative performance indexes that yielded an acceptable degree of repeatability may be readily implemented in the OT test to assess the cracking characteristics of AC mixes.

scholarly journals Influence of the specimen production and preparation on the compressive strength and the fatigue resistance of HPC and UHPC

2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Marco Basaldella ◽  
Nadja Oneschkow ◽  
Ludger Lohaus
Keyword(s):  
Compressive Strength ◽  
Positive Influence ◽  
Probabilistic Methods ◽  
Specimen Preparation ◽  
Mean Values ◽  
Compression Load ◽  
The Mean ◽  
Number Of Cycles ◽  
Preparation Techniques ◽  
Cycles To Failure

AbstractThe results of tests under monotonically increasing load and cyclic compression load are often analysed by means of probabilistic methods. Although there is a considerable scattering in the results, especially in the number of cycles to failure, the cause of these cannot be completely explained. The imperfections of the specimens tested are among the causes of this scattering mentioned in the literature. Based on a round robin test the influence of HPC and UHPC production and specimen preparation techniques on the mean values of the compressive strengths, number of cycles to failure and data scattering have been evaluated. The main findings of the study are that the production techniques have an influence on the compressive strength, however, do not affect the mean number of cycles to failure. Moreover, the accurate preparation of the specimens has a positive influence on the compressive strength and the scattering of the results of both compression and cyclic load tests. The mean number of cycles to failure of HPC specimens is not influenced by the preparation techniques, whereas the polishing technique may have a positive influence on the mean number of cycles to failure of UHPC specimens.

Assessing Crack Susceptibility of Asphalt Concrete Mixtures with Overlay Tester

2018 ◽  
Vol 46 (3) ◽  
pp. 20170006 ◽  
Author(s):  
Victor M. Garcia ◽  
Alejandro Miramontes ◽  
Jose Garibay ◽  
Imad Abdallah ◽  
Soheil Nazarian
Keyword(s):  
Asphalt Concrete ◽  
Concrete Mixtures ◽  
Crack Susceptibility ◽  
Overlay Tester

Fatigue Life of the Human Teeth: A Continuum Damage Approach

2019 ◽  
Vol 43 ◽  
pp. 1-19
Author(s):  
Theddeus Tochukwu Akano
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Stress Amplitude ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Elastoplastic Model ◽  
Human Teeth ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Cycles To Failure

Normal oral food ingestion processes such as mastication would not have been possible without the teeth. The human teeth are subjected to many cyclic loadings per day. This, in turn, exerts forces on the teeth just like an engineering material undergoing the same cyclic loading. Over a period, there will be the creation of microcracks on the teeth that might not be visible ab initio. The constant formation of these microcracks weakens the teeth structure and foundation that result in its fracture. Therefore, the need to predict the fatigue life for human teeth is essential. In this paper, a continuum damage mechanics (CDM) based model is employed to evaluate the fatigue life of the human teeth. The material characteristic of the teeth is captured within the framework of the elastoplastic model. By applying the damage evolution equivalence, a mathematical formula is developed that describes the fatigue life in terms of the stress amplitude. Existing experimental data served as a guide as to the completeness of the proposed model. Results as a function of age and tubule orientation are presented. The outcomes produced by the current study have substantial agreement with the experimental results when plotted on the same axes. There is a notable difference in the number of cycles to failure as the tubule orientation increases. It is also revealed that the developed model could forecast for any tubule orientation and be adopted for both young and old teeth.

Unification proposals for fatigue crack propagation laws

2017 ◽  
Vol 13 (2) ◽  
pp. 262-283 ◽  
Author(s):  
Vladimir Kobelev
Keyword(s):  
Differential Equation ◽  
Crack Propagation ◽  
Crack Length ◽  
Closed Form ◽  
Crack Growth ◽  
Stress Ratio ◽  
Elementary Functions ◽  
Content Type ◽  
Number Of Cycles ◽  
Cycles To Failure

Purpose The purpose of this paper is to propose the new dependences of cycles to failure for a given initial crack length upon the stress amplitude in the linear fracture approach. The anticipated unified propagation function describes the infinitesimal crack-length growths per increasing number of load cycles, supposing that the load ratio remains constant over the load history. Two unification functions with different number of fitting parameters are proposed. On one hand, the closed-form analytical solutions facilitate the universal fitting of the constants of the fatigue law over all stages of fatigue. On the other hand, the closed-form solution eases the application of the fatigue law, because the solution of nonlinear differential equation turns out to be dispensable. The main advantage of the proposed functions is the possibility of having closed-form analytical solutions for the unified crack growth law. Moreover, the mean stress dependence is the immediate consequence of the proposed law. The corresponding formulas for crack length over the number of cycles are derived. Design/methodology/approach In this paper, the method of representation of crack propagation functions through appropriate elementary functions is employed. The choice of the elementary functions is motivated by the phenomenological data and covers a broad region of possible parameters. With the introduced crack propagation functions, differential equations describing the crack propagation are solved rigorously. Findings The resulting closed-form solutions allow the evaluation of crack propagation histories on one hand, and the effects of stress ratio on crack propagation on the other hand. The explicit formulas for crack length over the number of cycles are derived. Research limitations/implications In this paper, linear fracture mechanics approach is assumed. Practical implications Shortening of evaluation time for fatigue crack growth. Simplification of the computer codes due to the elimination of solution of differential equation. Standardization of experiments for crack growth. Originality/value This paper introduces the closed-form analytical expression for crack length over number of cycles. The new function that expresses the damage growth per cycle is also introduced. This function allows closed-form analytical solution for crack length. The solution expresses the number of cycles to failure as the function of the initial size of the crack and eliminates the solution of the nonlinear ordinary differential equation of the first order. The different common expressions, which account for the influence of the stress ratio, are immediately applicable.

Lifetime estimation for a land-fast ice sheet subjected to ocean swell

2001 ◽  
Vol 33 ◽  
pp. 333-338 ◽  
Author(s):  
P. J. Langhorne ◽  
V. A. Squire ◽  
C. Fox ◽  
T. G. Haskell
Keyword(s):  
Sea Ice ◽  
Strain Field ◽  
Field Experiments ◽  
Ice Sheet ◽  
Lifetime Estimation ◽  
Spectral Content ◽  
Fast Ice ◽  
Damage Law ◽  
Number Of Cycles ◽  
Cycles To Failure

AbstractIt is well known that an incoming ocean swell produces a strain field in a land-fast ice sheet. The attenuation and spectral content of this strain field can be calculated and has been measured. The response of the sea ice to this type of cyclic forcing has also been measured, and in particular we are able to estimate the number of cycles to failure for sea ice loaded at constant amplitude. In this paper we consider the response of the land-fast ice sheet or vast floe to a measured ice-coupled wave field of variable amplitude. We use the Palmgren-Miner cumulative damage law and stress-lifetime curves taken from field experiments to predict the lifetime of the sea-ice sheet as a function of significant wave height and sea-ice brine fraction. Calculations are performed to account for the swell entering a land-fast sea-ice sheet at arbitrary angle, and the influence of c-axis alignment and the presence of pre-existing cracks are discussed.

Mechanical Fatigue Limit for Rubber

1966 ◽  
Vol 39 (2) ◽  
pp. 348-364 ◽  
Author(s):  
G. J. Lake ◽  
P. B. Lindley
Keyword(s):  
Fatigue Limit ◽  
Growth Behavior ◽  
Energy Characteristics ◽  
Mechanical Fatigue ◽  
Tearing Energy ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Limiting Value ◽  
Mechanical Rupture

Abstract Investigations of the dynamic cut growth behavior of vulcanized rubbers indicate that there is a minimum tearing energy at which mechanical rupture of chains occurs. The limiting value is characteristic of each vulcanizate, but is in the region of 0.05 kg/cm. The mechanical fatigue limit, below which the number of cycles to failure increases rapidly, is accurately predicted from this critical tearing energy. Characteristics of cut growth at low tearing energies, and effects of polymer, vulcanizing system, oxygen, and fillers on the critical tearing energy and fatigue limit are discussed.

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