Multiaxial Behavior and Viscoelastic Constitutive Modeling of Epoxy Polymers

2000 ◽  
Author(s):  
F. Ellyin ◽  
Y. Hu ◽  
Z. Xia
Keyword(s):  
Present Model ◽  
Hydrostatic Stress ◽  
Equivalent Stress ◽  
Experiment Data ◽  
Epoxy Polymers ◽  
Nonlinear Viscoelastic ◽  
Octahedral Shear Stress ◽  
Strain Paths ◽  
Viscoelastic Constitutive Model ◽  
Stress Influence

Abstract A nonlinear viscoelastic constitutive model previously proposed has been modified to account for hydrostatic stress influence. The modification is achieved by incorporating the hydrostatic stress in the equivalent stress definition. The present model predicts a shift of stress envelopes along equibiaxial compressive stress direction. It also predicts different octahedral shear stress versus octahedral shear strain curves for various strain paths. These trends indicate improved agreement between the model prediction and multiaxial experiment data.

Constitutive modeling of strain-dependent bond breaking and healing kinetics of chemical polyampholyte (PA) gel

Soft Matter ◽  
2021 ◽  
Vol 17 (15) ◽  
pp. 4161-4169
Author(s):  
Sairam Pamulaparthi Venkata ◽  
Kunpeng Cui ◽  
Jingyi Guo ◽  
Alan T. Zehnder ◽  
Jian Ping Gong ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Uniaxial Tension ◽  
Constitutive Modeling ◽  
Finite Strain ◽  
Bond Breaking ◽  
Nonlinear Viscoelastic ◽  
Viscoelastic Constitutive Model ◽  
Kinetics Of ◽  
Strain Dependent

A finite strain nonlinear viscoelastic constitutive model is used to study the uniaxial tension behaviour of a chemical polyampholyte (PA) gel.

Some Implications of a Nonlinear Viscoelastic Constitutive Theory Regarding Interrelationships Between Creep and Strength Behavior of Ice at Failure

1989 ◽  
Vol 111 (2) ◽  
pp. 144-148 ◽  
Author(s):  
B. D. Harper
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Nonlinear Viscoelastic ◽  
Uniaxial Creep ◽  
Strength Behavior ◽  
Minimum Strain Rate ◽  
Strength Constant ◽  
Viscoelastic Constitutive Model ◽  
Stress And Strain Rate ◽  
Special Case

This study explores several possibilities for a correspondence in the behavior of ice at failure during uniaxial creep (constant stress) and strength (constant strain rate) experiments. The usual notion of failure in ice is employed (i.e., the occurrence of a minimum strain rate during a creep test and a peak or maximum stress during a strength test), and the behavior at failure is discussed in terms of a recently proposed nonlinear viscoelastic constitutive model for ice. It is demonstrated that no correspondence between creep and strength data can be expected in general; however, several approximate interrelationships do occur for the experimentally motivated special case of a constant (independent of stress and strain rate) failure strain.

A Study of High Temperature Damage Processes Using Microradiography

1988 ◽  
Vol 142 ◽  
Author(s):  
J. E. Benci ◽  
D. P. Pope
Keyword(s):  
Image Analysis ◽  
Alloy Steel ◽  
Hydrostatic Stress ◽  
Equivalent Stress ◽  
Creep Damage ◽  
Tensile Tests ◽  
Crack Plane ◽  
Image Analysis System ◽  
Low Alloy Steel ◽  
Damage Process

AbstractSynchrotron radiation and microradiographic techniques were used to study the development of creep damage in notched tensile samples. The creep damage in these samples was recorded using microradiography. The density and distribution of creep damage was measured from the microradiographs using an image analysis system. The results from the image analysis can be compared to damage predictions from finite element models of the damage process to determine the quality of these models.Notched tensile samples of copper, iron and a low alloy steel were subjected to slow strain rate tensile tests at 500°C or 700°C. The tests were interrupted after various fractions of the creep lives had been expended. 1 mm thick longitudinal sections were then removed from the center of each sample for microradiography using electro-discharge machining.Creep damage in the copper alloy was concentrated in a fairly narrow band around the plane of minimum cross-section in the samples. This is in stark contrast to the results from iron and the low alloy steel. The creep damage in these materials developed at fairly sharp angles to the notch or crack plane. These results show that the damage process in iron and this steel is controlled by the equivalent stress while the formation of damage in copper is controlled by the maximum principal or hydrostatic stress.

A Nonlinear Viscoelastic and Micromechanical Damage Constitutive Model for Solid Propellant

2013 ◽  
Vol 750-752 ◽  
pp. 2196-2199
Author(s):  
Zhi Xu Gu ◽  
Jian Zheng ◽  
Wei Peng ◽  
Xi Nan Tang ◽  
Jun Hui Yin
Keyword(s):  
Constitutive Model ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Solid Propellant ◽  
Damage Evolution Equation ◽  
Nonlinear Viscoelastic ◽  
Tension Tests ◽  
Composite Solid Propellant ◽  
Damage Process ◽  
Viscoelastic Constitutive Model

This paper studies the damage process induced by dewetting microcracks in composite solid propellant. A nonlinear viscoelastic constitutive model for composite soild propellant is presented. The damage variable D is derived from the microcrack system and is function of microcrack size density. The damage evolution equation is determinded by the extending of microcrack. Form the proposed model of microrack evolution process, an explicit form of damage evolution equation which is a function of stress field is given. The cracking event N and the new crack surface area damage ΔA formed by microcrack extension are defined. Material constants are determinded by acoustic emission tests. The rationality of our model has been confirmed by tension tests.

Evaluation of Creep Properties in Soldering Ball by Nanoindentation Creep

2005 ◽  
Author(s):  
Tadahiro Shibutani ◽  
Qiang Yu ◽  
Masaki Shiratori
Keyword(s):  
Chemical Potential ◽  
Early Stage ◽  
Hydrostatic Stress ◽  
Equivalent Stress ◽  
Nanoindentation Test ◽  
Diffusion Creep ◽  
Creep Properties ◽  
Last Stage ◽  
Power Law Creep ◽  
The Relationship

In this paper, the behavior the behavior of creep deformation in low melting point alloy during a nanoindentation test was examined. Nanoindentation creep test was performed for eutectic tin-lead solder ball. Estimated creep exponent from the relationship between hardness and indenter dwell-time decreases as a function of time. The morphology of indented area shows that the transition from the deformation due to the tip in the early stage to another one in the last stage. Each grain near the indenter tip was transformed in the last stage. Stress analysis using a finite element method reveals that relaxation of equivalent stress progresses rapidly and the residual hydrostatic stress is dominant. Then, the gradient of the residual hydrostatic stress affects the chemical potential on grain boundaries and diffusion creep is activated. Therefore, the transition from the power-law creep to diffusion creep takes place during the nanoindentaion creep.

scholarly journals Piezo-Plunger Jetting Technology: An Experimental Study on Jetting Characteristics of Filled Epoxy Polymers

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 23 ◽  
Author(s):  
Alexander Kurz ◽  
Jörg Bauer ◽  
Manfred Wagner
Keyword(s):  
High Speed ◽  
Colloidal Particles ◽  
Theoretical Research ◽  
Related Factors ◽  
Rheological Analysis ◽  
Drop Dynamics ◽  
Epoxy Polymers ◽  
Glass Spheres ◽  
Nonlinear Viscoelastic ◽  
Properties Of Materials

The droplet formation of Newtonian fluids and suspensions modified by spherical, non-colloidal particles has attracted much interest in practical and theoretical research. For the present study, a jetting technique was used which accelerates a geometrically defined plunger by a piezoelectric actuator. Changing rheological properties of materials and extending deformation rates towards nonlinear viscoelastic regimes created the requirement to extend dosage impulses towards larger magnitudes. To mimic the rheological characteristics of nonconductive adhesives we modified Newtonian epoxy resins by thixotropic additives and micro-scale glass spheres. Rheological analysis at steady shear and oscillatory shear ensured a differentiation between material and process-related factors. Evaluation of high-speed images allowed the investigation of drop dynamics and highlighted the dispense impulse reduction by material-specific dampening properties.

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