Rate-Dependent function in the correlation between hardness and yield stress of polyethylene composites

2000 ◽  
Vol 21 (2) ◽  
pp. 238-244 ◽  
Author(s):  
J. Suwanprateeb
Keyword(s):  
Yield Stress ◽  
Rate Dependent ◽  
Dependent Function ◽  
Polyethylene Composites

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2019 ◽  
Vol 287 ◽  
pp. 3-7
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

EFFECTS OF STRAIN RATE DEPENDENCY OF MATERIAL PROPERTIES IN LOW VELOCITY IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1165-1170 ◽  
Author(s):  
HIROFUMI MINAMOTO ◽  
ROBERT SEIFRIED ◽  
PETER EBERHARD ◽  
SHOZO KAWAMURA
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Yield Stress ◽  
Coefficient Of Restitution ◽  
Finite Element Simulations ◽  
Material Behavior ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Strain Rate Dependency ◽  
The Impact

Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of strain rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. Finite Element simulations using strain-rate dependent material behavior are carried out. In addition, Finite Element simulations with elastic-plastic material behavior, which ignore the strain rate dependency, are carried out as well as elastic material behavior. Comparisons between the experiments and the simulations using strain-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the strain rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.

scholarly journals Shear Rate-Dependent Rheological Properties of Mine Tailings: Determination of Dynamic and Static Yield Stresses

2019 ◽  
Vol 9 (22) ◽  
pp. 4744
Author(s):  
Sueng-Won Jeong
Keyword(s):  
Shear Rate ◽  
Yield Stress ◽  
Stress Growth ◽  
Rate Dependent ◽  
Static Yield ◽  
Dynamic Yield ◽  
Bingham Yield Stress ◽  
Growth Methods ◽  
Static Yield Stress

In this paper, shear rate-dependent rheological properties of mine tailings taken from abandoned mine deposits prone to mass movements are examined using a commercial ball-measuring rheological system. The yield stresses (i.e., dynamic and static yield stresses) and viscosity of sand-rich materials are examined by the shear rate-controlled flow curve and time-dependent stress growth methods. Before yielding, the shear stress reaches a peak value (i.e., yield stress) observed for all flow curves. In the steady-state condition, the materials have a minimum shear stress (i.e., dynamic yield stress). The static yield stress can be determined under a constant applied shear rate with different initial values ranging from 10−4 to 10−1 s−1. As a result, the Bingham yield stress and viscosity can be used as a first approximation for estimating the debris flow mobility of post-failure materials. However, the Bingham yield stress is competitive with the static yield stress measured from stress growth methods. Upon comparison of the dynamic and static yield stresses, the static yield stress is approximately 35–45 times greater than the dynamic yield stress, and may be strongly related to microstructural changes (i.e., thixotropy). In this context, special attention must be paid to the determination of yield stresses in debris flow mitigation programs.

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2018 ◽  
Vol 30 ◽  
pp. 8-12
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

Application of the Quemada Viscosity Model for Drilling Fluids

2021 ◽  
Author(s):  
Sandra Knutsen ◽  
Eric Cayeux ◽  
Arild Saasen ◽  
Mahmoud Khalifeh
Keyword(s):  
Shear Rate ◽  
Yield Stress ◽  
Drilling Fluid ◽  
Model Fit ◽  
Drilling Fluids ◽  
Shear Rates ◽  
Rate Dependent ◽  
Dependent Viscosity ◽  
Very High

Abstract A number of different models are used to describe the shear rate dependent viscosity of drilling fluids. Most, such as the Herschel-Bulkley model, have a purely empirical basis. The Quemada model, while still empirical, is based on physical principles. It is based on the notion that structural units develop in the fluid at low shear rates which are then partially broken down as the applied shear rate increases. In the current work, drilling fluid rheological data are fitted to the Herschel-Bulkley and the Quemada model. The development of the Quemada model and the calculation of each model parameter are presented. We show that the Quemada model better fits measurements over a wider range of shear rates than the Herschel-Bulkley model. We describe how to select the parameters of the Quemada model. Knowing the difficulty of obtaining a known shear rate for fluids with yield stresses, we discuss how this can affect the quality of the Quemada model fit. Furthermore, in principle, the Quemada model is not applicable in presence a non-zero yield stress. Therefore, we show how to handle the yield stress using a (very high) zero shear rate viscosity.

Prediction of Fatigue Life With and Without Hold Times Using the Chaboche Viscoplastic Constitutive Theory

1990 ◽  
Vol 112 (2) ◽  
pp. 188-197 ◽  
Author(s):  
S. S. Chiu ◽  
J. Eftis ◽  
D. L. Jones
Keyword(s):  
Fatigue Life ◽  
Yield Stress ◽  
Stress Level ◽  
Life Prediction ◽  
Hold Time ◽  
Fatigue Life Prediction ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Rate Of Loading

The titanium alloy Ti-6Al-4V is known to exhibit creep behavior at temperatures as low as room temperature. Consequently, for cyclic loading with hold times it is possible that the rate dependent behavior of Ti-6Al-4V can have negative bearing upon the low cycle fatigue life. If this effect is shown to be present at room temperatures, then it will certainly be magnified and, therefore, very important at elevated temperatures. In order to account for the effects of strain rate dependent deformation in fatigue life prediction methodology, it was considered necessary to incorporate a viscoplastic constitutive equation into the fatigue life calculational algorithm. After critical evaluation of a score of recently proposed viscoplastic constitutive theories, the Chaboche theory, which employs a yield condition, was considered to offer the most promise for description of a wide range of inelastic material behavior characteristics. The six viscoplastic material parameters that are required for nonelevated temperature applications were determined from data of uniaxial tests, conducted elsewhere and made avialable to this study. The fatigue life testing of smooth round bar specimens included load cycles with load hold times. Fatigue life predictions were performed using the equivalent fully reversed symmetric cycle, and the Smith-Watson-Topper parameter, for load cycles having varying stress amplitudes and varying hold times. The predicted fatigue life results indicate that: (i) For a given stress level above the initial yield stress, shorter load hold time periods result in longer fatigue lives. (ii) The higher the stress level (above the initial yield stress) the more pronounced becomes the effect of the load hold time on the fatigue life prediction. (iii) The rate of loading also has an effect on fatigue life. Analysis indicates that the slower the rate of loading, the higher the rate dependent (primary creep) deformation, and consequently, the lower the resulting fatigue life.

Temperature and Rate-Dependent Constitutive Relationship for Vanadium Alloy V-5Cr-5Ti and Failure Modes

2010 ◽  
Vol 44-47 ◽  
pp. 2336-2340
Author(s):  
Xi Cheng Huang ◽  
Wen Jun Hu ◽  
Yi Xia Yan ◽  
Ruo Ze Xie ◽  
Fang Ju Zhang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Strain Rate ◽  
Yield Stress ◽  
Failure Modes ◽  
Constitutive Relationship ◽  
Strain Rates ◽  
Vanadium Alloy ◽  
Rate Dependent ◽  
Brittle Ductile Transition ◽  
Wide Range

In this work the static and dynamic properties of vanadium alloy V-5Cr-5Ti over a wide range of temperature from 20 to 1000 degree at strain rates ranged from 10-4/s~103/s were studied experimentally under uniaxial quasi-static tension with MTS universal testing machine, uniaxial dynamic compression and tension with split Hopkinson bar system with temperature control. The stress-strain curves of V-5Cr-5Ti at various temperatures and various strain rates were obtained. Experimental data show that V-5Cr-5Ti behaves strain-rate sensitive and temperature dependent, for instance the material parameters yield stress, tensile strength and failure strain. And fracture mode of the material is also dependent on strain-rate and temperature. Based on experimental data the temperature-rate-dependent constitutive relations were established in the form of Johnson-Cook and Cowper-Symonds models which are widely used in numerical simulation of dynamic processes of structures under impact loading. The material microstructures and failure modes were analyzed using optical microscope, TEM etc, and results shows that the yield stress and strength are increased with strain rate. The brittle-ductile transition strain-rate is from 101/s to102/s.

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