A Preliminary Study of the After-Effect or Drift in Rubber under Constant Load

1937 ◽  
Vol 10 (2) ◽  
pp. 224-230
Author(s):  
Milton L. Braun
Keyword(s):  
Specific Gravity ◽  
Power Law ◽  
Constant Load ◽  
Observation Time ◽  
Rubber Tube ◽  
Original Length ◽  
Specific Analysis ◽  
After Effect ◽  
Preliminary Study ◽  
Logarithmic Law

Abstract When a suitable weight is supported by suspension from a piece of rubber, as a stationer's band, the rubber may be stretched any amount up to several times its original length, but its new length is not constant; it increases with time. The increase in length with time is variously known as “after-effect, #x201D; “creep,” “drift,” “flow,” or “time-yield.” This phenomenon, which seems to have been very incompletely investigated, was probably first recognized by Dietzel in 1857. Kohlrausch in 1875 made an entensive study of both torsional and linear after-effect in metal, glass, and rubber. The load used by Kohlrausch on rubber were, however, exceedingly small, and the duration of drift was limited to one day. He came to the conclusion that drift in rubber followed a power law for the first sixty minutes. During the next decade Pulfrich slightly extended the work of Kohlrausch by experimentation on a red rubber tube, using elongations up to 150 per cent, with maximum observation time of 15 days. He concluded that the power law of Kohlrausch held for at least thirty minutes of drift. In 1903, Bouaase and Carrière observed the after-effect (in pure gum and sulfur cords of 4 mm. diameter and of specific gravity 0.984) under a great variety of experiments, and concluded that drift was to be expressed by an exponential or logarithmic law rather than by a power function. Both Phillips and Schwartz arrived at similar conclusions. More recently Ariano reported that the drift proceeded at a decreasing rate which finally assumed a constant value either finite or zero. Van Geel and Eymers found that for milled rubber the drift continued until the specimens broke, but that for rubber obtained by evaporation of latex all after-effect ceased within three minutes. Shacklock noted that creep took place for some hours and then reached a limit. Evidently more light needs to be cast on the probem of the drift effect in rubber. Two preliminary experiments on drift are herein considered; Part I on general trends, and Part II on more specific analysis of the effect as observed in one specimen.

scholarly journals A Preliminary Study on the Physical Properties of an Alternative Coarse Aggregate Made with Red Soil and Fly Ash

2018 ◽  
Vol 12 (1) ◽  
pp. 1-8
Author(s):  
J. Bright Brabin Winsley ◽  
M. Muthukannan
Keyword(s):  
Fly Ash ◽  
Specific Gravity ◽  
Room Temperature ◽  
Coarse Aggregate ◽  
Environmental Issues ◽  
Red Soil ◽  
Test Results ◽  
Ordinary Concrete ◽  
Preliminary Study ◽  
Natural Aggregates

Background and Objective: The demand for course aggregate is increasing every day. Natural aggregate used for ordinary concrete is obtained by quarrying, which cause serious environmental issues. An alternate course aggregate is needed for sustainable development. The objective of this research is to produce an alternative course aggregate in combination with soil available locally near site along with fly ash, to test its properties to make it fit for concrete. Method: An alternative coarse aggregate is produced from red soil and fly ash mixed at various ratios, 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, fresh aggregate granules of different sizes less than 10mm is prepared using hand press, the aggregates were sundried in shade for 24hours, oven dried at 110°C, burned in Muffle furnace at temperature of 950°C and cooled gradually to reach room temperature. After the production, the specific gravity, bulk density, water absorption, Impact and aggregate crushing of the aggregates were tested. Result: Test results showed that aggregates produced are of lesser specific gravity, density with relatively appreciable impact value and crushing value. Conclusion: The test results show that the aggregates produced can be used in construction as replacement for natural aggregates.

The time to failure of fiber bundles subjected to random loads

1979 ◽  
Vol 11 (03) ◽  
pp. 527-541 ◽  
Author(s):  
Howard M. Taylor
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Failure Time ◽  
Constant Load ◽  
Asymptotic Distributions ◽  
Asymptotic Independence ◽  
Time To Failure ◽  
Random Load ◽  
The Mean ◽  
Wave Induced

The effect on cable reliability of random cyclic loading such as that generated by the wave-induced rocking of ocean vessels deploying these cables is examined. A simple model yielding exact formulas is first explored. In this model, the failure time of a single fiber under a constant load is assumed to be exponentially distributed, and the random loadings are a two-state stationary Markov process. The effect of load on failure time is assumed to follow a power law breakdown rule. In this setting, exact results concerning the distribution of bundle or cable failure time, and especially the mean failure time, are obtained. Where the fluctuations in load are frequent relative to bundle life, such as may occur in long-lived cables, it is shown that randomness in load tends to decrease mean bundle life, but it is suggested that the reduction in mean life often can be restored by modestly reducing the base load on the structure or by modestly increasing the number of elements in the bundle. In later pages this simple model is extended to cover a broader range of materials and random loadings. Asymptotic distributions and mean failure times are given where fibers follow a Weibull distribution of failure time under constant load, and loads that are general non-negative stationary processes subject only to some mild condition of asymptotic independence. When the power law breakdown exponent is large, the mean time to bundle failure depends heavily on the exact form of the marginal probability distribution for the random load process and cannot be summarized by the first two moments of this distribution alone.

Computational and Experimental Characterization of Indentation Creep

2003 ◽  
Vol 795 ◽  
Author(s):  
Ming Dao ◽  
Hidenari Takagi ◽  
Masami Fujiwara ◽  
Masahisa Otsuka
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Constant Load ◽  
Dislocation Creep ◽  
Solid Solution Alloy ◽  
Indentation Creep ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Self Similar ◽  
Power Law Creep

ABSTRACT:Detailed finite-element computations and carefully designed indentation creep experiments were carried out in order to establish a robust and systematic method to accurately extract creep properties during indentation creep tests. Finite-element simulations confirmed that, for a power law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent, n, the activation energy for creep, Qc and so on can be evaluated robustly. Samples made from an Al-5.3mol%Mg solid solution alloy were tested at temperatures ranging from 573 K to 773 K. The results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime.

scholarly journals Flexible and consistent quantile estimation for intensity–duration–frequency curves

2021 ◽  
Vol 25 (12) ◽  
pp. 6479-6494
Author(s):  
Felix S. Fauer ◽  
Jana Ulrich ◽  
Oscar E. Jurado ◽  
Henning W. Rust
Keyword(s):  
Power Law ◽  
Skill Score ◽  
Observation Time ◽  
Performance Model ◽  
Wide Range ◽  
Intensity Duration Frequency ◽  
The Individual ◽  
The Relationship ◽  
Flexible Model

Abstract. Assessing the relationship between the intensity, duration, and frequency (IDF) of extreme precipitation is required for the design of water management systems. However, when modeling sub-daily precipitation extremes, there are commonly only short observation time series available. This problem can be overcome by applying the duration-dependent formulation of the generalized extreme value (GEV) distribution which fits an IDF model with a range of durations simultaneously. The originally proposed duration-dependent GEV model exhibits a power-law-like behavior of the quantiles and takes care of a deviation from this scaling relation (curvature) for sub-hourly durations (Koutsoyiannis et al., 1998). We suggest that a more flexible model might be required to model a wide range of durations (1 min to 5 d). Therefore, we extend the model with the following two features: (i) different slopes for different quantiles (multiscaling) and (ii) the deviation from the power law for large durations (flattening), which is newly introduced in this study. Based on the quantile skill score, we investigate the performance of the resulting flexible model with respect to the benefit of the individual features (curvature, multiscaling, and flattening) with simulated and empirical data. We provide detailed information on the duration and probability ranges for which specific features or a systematic combination of features leads to improvements for stations in a case study area in the Wupper catchment (Germany). Our results show that allowing curvature or multiscaling improves the model only for very short or long durations, respectively, but leads to disadvantages in modeling the other duration ranges. In contrast, allowing flattening on average leads to an improvement for medium durations between 1 h and 1 d, without affecting other duration regimes. Overall, the new parametric form offers a flexible and enhanced performance model for consistently describing IDF relations over a wide range of durations, which has not been done before as most existing studies focus on durations longer than 1 h or day and do not address the deviation from the power law for very long durations (2–5 d).

Creep Behaviour of Closed Cell Aluminium Foams from Stress Relaxation Tests

2009 ◽  
Vol 423 ◽  
pp. 131-136 ◽  
Author(s):  
B. Carcel ◽  
A.C. Carcel ◽  
P. Arrué
Keyword(s):  
Stress Relaxation ◽  
Power Law ◽  
Creep Behaviour ◽  
Solid Material ◽  
Constant Load ◽  
Creep Tests ◽  
Closed Cell ◽  
Power Law Exponent ◽  
Order Of Magnitude ◽  
Power Law Creep

Creep behaviour of closed cell aluminium foams and transitions from power law to power law breakdown (PLB) creep regimes are investigated from results of stress relaxation tests (SRT) carried out on Alporas foams with densities between 0.20 to 0.32 g/cm3. Tests were carried out at temperatures between 200°C and 300°C and stress relaxation was measured from the collapse stress under compression of the foams. Under similar foam density, temperature and stress conditions, the values of strain rate calculated from SRT tests were of the same order of magnitude than those previously reported in the literature from conventional constant load creep tests. Under stress values close to the collapse stress, the creep mechanism seems to follow a PLB regime, with values of the power law exponent n=10-17, much higher than those corresponding to the power law creep in the solid material (n=4.4-6.5) and with activation energy values close to Q = 150 KJ/mol. Having in mind the limitations of available creep models for closed cell foams and the need for additional experimental results, the use of SRT testing would offer advantages for the assessment of the high temperature behaviour of aluminium foams, due to its lower testing times and reduced experimental effort.

scholarly journals Analysis of Separation Distances under Varying Odour Emission Rates and Meteorology: A WWTP Case Study

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 962
Author(s):  
Marco Ravina ◽  
Salvatore Bruzzese ◽  
Deborah Panepinto ◽  
Mariachiara Zanetti
Keyword(s):  
Power Law ◽  
Research Work ◽  
Treatment Plant ◽  
Evaluation Procedure ◽  
Second Phase ◽  
Emission Rates ◽  
Italian Regions ◽  
Logarithmic Law ◽  
Selection Of

A wide variability of odour impact criteria is found around the world. The objective of this research work was to evaluate the influence of the uncertainties related to some individual stages of odour impact assessment in the application of regulatory criteria. The evaluation procedure was established by following the guidelines of the Northern Italian regions. A wastewater treatment plant located in Northern Italy was considered as a case study. Odour dispersion modelling was carried out with the CALPUFF model. The study focused on two phases of the assessment. The first phase was the selection of the meteorology datasets. For low odour concentration thresholds (CT = 1 OU m−3), the results showed that two different years (2018 and 2019) provided similar patterns of the separation distances. The difference between the two years tended to increase by increasing the value of the concentration threshold (CT = 3 OU m−3 and CT = 5 OU m−3). The second phase of the assessment was the selection of the open field correction method for wind velocity used in the calculation of odour emission rates (OERs). Three different relationships were considered: the power law, the logarithmic law and the Deaves–Harris (D–H) law. The results showed that OERs and separation distances varied depending on the selected method. Taking the power law as the reference, the average variability of the separation distances was between −7% (D–H law) and +10% (logarithmic law). Higher variability (up to 25%) was found for single transport distances. The present study provides knowledge towards a better alignment of the concept of the odour impact criteria.

The time to failure of fiber bundles subjected to random loads

1979 ◽  
Vol 11 (3) ◽  
pp. 527-541 ◽  
Author(s):  
Howard M. Taylor
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Failure Time ◽  
Constant Load ◽  
Asymptotic Distributions ◽  
Asymptotic Independence ◽  
Time To Failure ◽  
Random Load ◽  
The Mean ◽  
Wave Induced

The effect on cable reliability of random cyclic loading such as that generated by the wave-induced rocking of ocean vessels deploying these cables is examined. A simple model yielding exact formulas is first explored. In this model, the failure time of a single fiber under a constant load is assumed to be exponentially distributed, and the random loadings are a two-state stationary Markov process. The effect of load on failure time is assumed to follow a power law breakdown rule. In this setting, exact results concerning the distribution of bundle or cable failure time, and especially the mean failure time, are obtained. Where the fluctuations in load are frequent relative to bundle life, such as may occur in long-lived cables, it is shown that randomness in load tends to decrease mean bundle life, but it is suggested that the reduction in mean life often can be restored by modestly reducing the base load on the structure or by modestly increasing the number of elements in the bundle.In later pages this simple model is extended to cover a broader range of materials and random loadings. Asymptotic distributions and mean failure times are given where fibers follow a Weibull distribution of failure time under constant load, and loads that are general non-negative stationary processes subject only to some mild condition of asymptotic independence. When the power law breakdown exponent is large, the mean time to bundle failure depends heavily on the exact form of the marginal probability distribution for the random load process and cannot be summarized by the first two moments of this distribution alone.

A Theoretical Calibration Curve for the Preston Tube on Smooth Boundaries for Larger Reynolds Numbers

1965 ◽  
Vol 69 (650) ◽  
pp. 136-137 ◽  
Author(s):  
N. Rajaratnam
Keyword(s):  
Power Law ◽  
Calibration Curve ◽  
Static Pressure ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Boundary Shear ◽  
Total Head ◽  
Logarithmic Law ◽  
The Difference ◽  
The One

Of the Several Methods available for the measurement of boundary shear, the simplest is perhaps the Preston tube. It is a total head tube resting on the boundary for which the difference between the dynamic pressure on the tube and the static pressure on the boundary is correlated with the boundary shear. It was evolved by Preston in 1954 mainly from similarity considerations and the existence of the wall law. In 1955, Hsu obtained Preston's original calibration curve theoretically for the one-seventh power law. In this note, a theoretical calibration curve is developed for the logarithmic law which describes the velocity distribution for larger Reynolds Numbers.

Aging and Glassy Dynamics in Complex Systems: Some Theoretical Ideas

1994 ◽  
Vol 367 ◽  
Author(s):  
Jean-Philippe Bouchaud
Keyword(s):  
Complex Systems ◽  
Power Law ◽  
Spin Glasses ◽  
A Priori ◽  
Mean Field ◽  
Observation Time ◽  
Spin Glass Phase ◽  
Power Law Decay ◽  
Small Times ◽  
Keywords Aging

AbstractWe discuss some recent experimental results on the non-stationary dynamics of spin-glasses, which serves as an excellent laboratory for other complex systems. Inspired from Parisi's mean-field solution, we propose that the dynamics of these systems can be though of as a random walk in phase space, between traps characterized by trapping time distribution decaying as a power law. The average exploration time diverges in the spin-glass phase, naturally leading to time-dependent dynamics with a charateristic time scale fixed by the observation time tw itself (aging). By the same token, we find that the correlation function (or the magnetization) decays as a stretched exponential at small times t ≪ tw crossing over to power-law decay at large times t ≫ tw. Finally, we discuss recent speculations on the relevance of these concepts to real glasses, where quenched disorder is a priori absent. Keywords: Aging, slow dynamics, spin-glasses, glasses.

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