Deformation Modeling Applied to Stress Relaxation of Four Solder Alloys

1980 ◽  
Vol 102 (2) ◽  
pp. 207-214 ◽  
Author(s):  
R. W. Rohde ◽  
J. C. Swearengen
Keyword(s):  
Stress Relaxation ◽  
Stainless Steels ◽  
General Concept ◽  
Model Parameters ◽  
Recovery Model ◽  
Solder Alloys ◽  
Dislocation Glide ◽  
Thermally Activated ◽  
Dependent Behavior ◽  
Excellent Description

Stress relaxation of four solder alloys, 50 percent Pb-50 percent In; 37.5 percent Sn-37.5 percent Pb-25 percent In; 63 percent Sn-37 percent Pb; and 62.5 percent Sn-37 percent Pb-0.5 percent Ag, has been examined at 222 K, 298 K, and 344 K. A model previously utilized to describe inelastic deformation of aluminum and stainless steels is applied and found to provide an excellent description of the experimental data. This model is based upon the general concept of stress assisted thermally activated dislocation glide in a microstructure evolving by the process of strain hardening and recovery. Model parameters useful for calculations of time dependent behavior of these solders are presented and their significance is discussed.

Line width Dependence of Stress Relaxation and Yield Behavior of Passivated Al(Cu) Lines

1994 ◽  
Vol 338 ◽  
Author(s):  
I.-S. Yeo ◽  
S.G.H. Anderson ◽  
C.-N. Liao ◽  
D. Jawarani ◽  
H. Kawasaki ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Void Formation ◽  
Relaxation Behavior ◽  
Effect Of Temperature ◽  
Thermally Induced ◽  
Stress Relaxation Behavior ◽  
Cu Films ◽  
Dislocation Glide ◽  
Thermally Activated ◽  
On Line

ABSTRACTStress relaxation behavior of thermally induced stresses in passivated line structures is strongly influenced by the metal yield strength. For some line geometries, stress relaxation can lead to void formation. In this study, bending beam measurements have been carried out to measure the thermal stress and stress relaxation behavior of passivated Al(l wt.% Cu) line structures with 3, 1, and 0.5 µm line widths. Our results reveal that stress relaxation in Al(Cu) films and lines shows log(time) kinetics consistent with a thermally activated dislocation glide mechanism. The kinetics of stress relaxation depend on line geometry and temperature, which can be explained by a combined effect of temperature (mass transport) and shear stress (driving force).

scholarly journals Fractional Stress Relaxation Model of Rock Freeze-Thaw Damage

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Q. Liu ◽  
W. Chen ◽  
J. K. Guo ◽  
R. F. Li ◽  
D. Ke ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Fatigue Loading ◽  
Element Model ◽  
Model Parameters ◽  
Rock Stress ◽  
Relaxation Equation ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Nonlinear Stress ◽  
Freeze Thaw Cycle

Freeze-thaw cycle is a type of fatigue loading, and rock stress relaxation under freeze-thaw cycles takes into account the influence of the freeze-thaw cycle damage and deterioration. Rock stress relaxation under freeze-thaw cycles is one of the paramount issues in tunnel and slope stability research. To accurately describe the mechanical behaviour of stress relaxation of rocks under freeze-thaw, the software element is constructed based on the theory of fractional calculus to replace the ideal viscous element in the traditional element model. The freeze-thaw damage degradation of viscosity coefficient is considered. A new three-element model is established to better reflect the nonlinear stress relaxation behavior of rocks under freeze-thaw. The freeze-thaw and stress relaxation of rock are simulated by ABAQUS, the relevant model parameters are determined, and the stress relaxation equation of rock under freeze-thaw cycle is obtained based on numerical simulation results. The research shows that the test results are consistent with the calculated results, indicating that the constitutive equation can better describe the stress relaxation characteristics of rocks under freeze-thaw and provide theoretical basis for surrounding rock support in cold region.

scholarly journals Variability of Mechanical Properties of Collagen Membranes used in Dentistry

2018 ◽  
Vol 55 (4) ◽  
pp. 488-493
Author(s):  
Loredana Santo ◽  
Fabrizio Quadrini ◽  
Denise Bellisario ◽  
Antonella Polimeni ◽  
Anna Santarsiero
Keyword(s):  
Stress Relaxation ◽  
Tensile Tests ◽  
Mechanical Analysis ◽  
Mechanical Tests ◽  
Static Behavior ◽  
Density Measurements ◽  
Dynamic Mechanical ◽  
Dependent Behavior ◽  
Order Of Magnitude ◽  
Collagen Membranes

The aim of this study is proposing a combination of measurements to assess the functional variability of collagen membranes used in Guided Bone Regeneration (GBR) and Guided Tissue Regeneration (GTR) techniques. As far as clinical applications are concerned, a proper qualification is critical when deciding, among commercially available collagen membranes, upon the most appropriate one for each specific clinical case. Two commercially available collagen membranes, namely Collprotect� and Jason�, were considered for the experimentation. After thickness and density measurements, the quasi-static behavior was studied for both membranes by means of conventional mechanical tests, i.e. tear and tensile tests, whereas their time-dependent behavior was evaluated by means of stress relaxation tests and dynamic mechanical analysis. Collagen membranes showed an elevated among samples variability. The variability within the same kind of membrane is of the same order of magnitude of the between membrane kinds variability. All the membranes showed strong time dependence both in stress relaxation and in dynamic mechanical tests. This fact should be taken under consideration for the membrane final application.

scholarly journals Constitutive Modeling of Time-Dependent Response of Human Plantar Aponeurosis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
P. G. Pavan ◽  
P. Pachera ◽  
C. Stecco ◽  
A. N. Natali
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Transverse Isotropy ◽  
Model Fitting ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Plantar Aponeurosis ◽  
Structural Conformation ◽  
Dependent Behavior

The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behavior of the aponeurotic tissue. This model is consistent with the structural conformation of the tissue where collagen fibers are mainly aligned with the proximal-distal direction. Constitutive model fitting to experimental data was made by implementing a stochastic-deterministic procedure. The stress relaxation was found close to 40%, independently of the level of strain applied. The agreement between experimental data and numerical results confirms the suitability of the constitutive model to describe the viscoelastic behaviour of the plantar aponeurosis.

Modeling of Dislocation Mobility in Metals: Effect of Obstacles and Thermal Processes

2001 ◽  
Vol 683 ◽  
Author(s):  
Masato Hiratani ◽  
Hussein M. Zbib
Keyword(s):  
Thermal Activation ◽  
Dislocation Dynamics ◽  
Thermal Processes ◽  
Weak Point ◽  
Dislocation Glide ◽  
Thermally Activated ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Activation Rate ◽  
Activation Event

ABSTRACTThermally activated dislocation glide velocity through weak point obstacle arrays is studied analytically and computationally. Thermal activation rate is estimated using the modified Friedel relations under the weak obstacle approximation. The average flight velocity after an activation event as a function of stress and temperature is obtained by the discrete dislocation dynamics (DD). This numerical calculation includes the effect of self-stress, interaction with electrons and phonons, and the inertial effect. These results are implemented into a phenomenological model to study the dislocation velocity under various conditions. The model can reproduce both obstacle control and drag control motion in low and high velocity regions, and a flow stress anomaly at transient regions.

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