Measurement and Calculation of Residual Stress in Axi-Symmetric Glass Sample Using Structural Relaxation Theory

2008 ◽  
Vol 39-40 ◽  
pp. 529-534
Author(s):  
Norbert Krečmer ◽  
Marek Liška ◽  
Josef Chocholoušek ◽  
Peter Vrábel
Keyword(s):  
Temperature Dependence ◽  
Structural Relaxation ◽  
Coefficient Of Thermal Expansion ◽  
High Stress ◽  
Polarized Light ◽  
Temperature History ◽  
Fictive Temperature ◽  
Stress Calculation ◽  
Applied Model ◽  
Glass Forming

Consistent model including structural relaxation is necessary for correct glass stress calculation in numerical computations of glass forming processes. Calculation of glass relaxation phenomena is often done by combining independent empirical formula on stress relaxation (for a simple temperature regime) and independent model of time-temperature dependence on Tool fictive temperature, Tf. Another approach was developed and verified here. Tool-Narayanaswamy and Moynihan/Mazurin relaxation model was adopted. Relaxation was obtained not from empirical model, but from calculated time-temperature dependence of Tool fictive temperature (Tf), dynamic viscosity, heat capacity and coefficient of thermal expansion. Heat conduction in a glass probe of known temperature history, structural relaxation and stress calculation were used in one computation scheme using Matlab. The stress of glass probe was measured using polarized light (Senarmont method). Rather high stress computation accuracy was obtained in comparison to stress experimental results. The applied model approach is being to be extended for application in commercial finite element codes for modeling of glass forming processes.

Evaluation of a Characteristic Temperature in the Relaxation of Metallic Glass Forming Liquids

2018 ◽  
Vol 941 ◽  
pp. 2331-2336 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Metallic Glass ◽  
Bond Strength ◽  
Temperature Dependence ◽  
Coordination Number ◽  
Structural Relaxation ◽  
Characteristic Temperature ◽  
Glass Forming ◽  
Metallic Liquids

The high-temperature viscosity of metallic glass-forming liquids is investigated by using the Bond Strength-Coordination Number Fluctuation (BSCNF) model developed by the authors. For many glass-forming liquids, a salient change in the structural relaxation is observed above the melting point. The temperature dependence of the structural relaxation exhibits a deviation from an Arrhenius-like behavior, and upon cooling it transforms to a non-Arrhenius-like one. In the present study, we show that the BSCNF model describes well the high-temperature viscosity behaviors of metallic liquids. The analysis based on the BSCNF model also enables to extract a characteristic temperature at high temperature. The results of the present study show that such characteristic temperature can be a good indicator for the evaluation of the range of the transition from the Arrhenius-like to the non-Arrhenius-like relaxation behavior.

Fictive-temperature dependence of structural relaxation in silica glass

2003 ◽  
Vol 94 (3) ◽  
pp. 1705-1708 ◽  
Author(s):  
Hiroshi Kakiuchida ◽  
Kazuya Saito ◽  
Akira J. Ikushima
Keyword(s):  
Temperature Dependence ◽  
Structural Relaxation ◽  
Silica Glass ◽  
Fictive Temperature

TEMPERATURE DEPENDENCE OF CONFIGURATIONAL ENTROPY ON STRUCTURAL RELAXATION FUNCTION IN GLASS-FORMING LIQUIDS

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2623-2627
Author(s):  
WANQIANG CAO ◽  
JUNLI HU
Keyword(s):  
Temperature Dependence ◽  
Structural Relaxation ◽  
Relaxation Function ◽  
Configurational Entropy ◽  
Experimental Results ◽  
Linear Term ◽  
Glass Forming ◽  
Relaxation Functions ◽  
Molecule Number ◽  
Non Linear

A direct correlation between the stretched exponent, β(T), of relaxation functions and configurational entropy of the Adam–Gibbs's theory on cooperatively rearranging region (CRR) in glass-forming liquids is investigated. One important result is that β(T) is equal to the relative configurational entropy per molecule. Another significant prediction is that β(T) is inversely proportional to the critical molecule number z*, of a CRR in the transformation. Further, a factor f(T) is proposed to express the temperature dependence of viscosity and configurational entropy. A modified Vogel-Fulcher–Tammann (VFT) equation is obtained by adding a small non-linear term to f(T). The above theoretic investigations coincide precisely with the calorimetric experimental results of 3-bromopentane.

A Finite-Temperature Continuum Theory Based on Interatomic Potentials

2005 ◽  
Vol 127 (4) ◽  
pp. 408-416 ◽  
Author(s):  
H. Jiang ◽  
Y. Huang ◽  
K. C. Hwang
Keyword(s):  
Temperature Dependence ◽  
Finite Temperature ◽  
Interatomic Potential ◽  
Coefficient Of Thermal Expansion ◽  
Harmonic Approximation ◽  
Continuum Theory ◽  
Single Wall Carbon Nanotubes ◽  
Interatomic Potentials ◽  
Atomistic Models ◽  
Continuum Theories

There are significant efforts to develop continuum theories based on atomistic models. These atomistic-based continuum theories are limited to zero temperature (T=0K). We have developed a finite-temperature continuum theory based on interatomic potentials. The effect of finite temperature is accounted for via the local harmonic approximation, which relates the entropy to the vibration frequencies of the system, and the latter are determined from the interatomic potential. The focus of this theory is to establish the continuum constitutive model in terms of the interatomic potential and temperature. We have studied the temperature dependence of specific heat and coefficient of thermal expansion of graphene and diamond, and have found good agreements with the experimental data without any parameter fitting. We have also studied the temperature dependence of Young’s modulus and bifurcation strain of single-wall carbon nanotubes.

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