Effect of Size-Dependent Cavitation on Micro- to Macroscopic Mechanical Behavior of Rubber-Blended Polymer

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Isamu Riku ◽  
Koji Mimura ◽  
Yoshihiro Tomita
Keyword(s):  
Surface Tension ◽  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Volumetric Strain ◽  
Critical Value ◽  
The Other ◽  
Size Dependent ◽  
Other Hand ◽  
Blended Polymer ◽  
Onset Of Cavitation

In rubber-blended polymer, the onset of cavitation in the particles relaxes the high triaxiality stress state and suppresses the onset of crazing in the polymer. As a result, large plastic deformation is substantially promoted compared with single-phase polymer. On the other hand, it is also well known that the onset of cavitation depends on the size of particle. To investigate the size dependence of cavitation behavior in the particle, a theoretical analysis is done employing a void model under plane strain condition, which takes into account the surface tension and the limiting stretch of the void. Continuously, to study the effect of the size-dependent cavitation on the micro- to macroscopic mechanical behavior of the blend, a computational model is proposed for the blend consisting of irregularly distributed heterogeneous particles containing the void with surface force. The results indicate that when the size of the particle decreases to a critical value that depends on both the initial shear modulus of particle and the surface tension on the surface of void, the increase of the critical stress for the onset of cavitation becomes remarkable and consequently, the onset of cavitation is eliminated. When the particle is embedded in polymer, the relation between average normal stress, which is acting on the interface of particle and matrix, and volumetric strain of particle shows dependence on the size of particle but no dependence on the triaxiality of macroscopic loading condition. For the blend consisting of particles smaller than the critical value, the onset of cavitation is eliminated in particles and as a result, the conformation of the shape of particle to the localized shear band in matrix becomes difficult and the shear deformation behavior tends to occur all over the matrix. Furthermore, in this case, the area of the maximum mean stress is confined to the area adjacent to the particle and the value of it increases almost linearly throughout the whole deformation process, which would lead to the onset of crazing in matrix. On the other hand, it is clarified that the onset of cavitation is predominant in the localized microscopic region containing heterogeneous particles and therefore, the plastic deformation is promoted in this region.

Effect of Specimen Geometry on the Predicted Mechanical Behavior of Polyethylene Pipe Material

2014 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Tawfeeq A. R. Alkanhal ◽  
Maher Y. A. Younan
Keyword(s):  
Mechanical Behavior ◽  
Longitudinal Direction ◽  
Primary Objective ◽  
The Other ◽  
Pipe Material ◽  
Ring Specimen ◽  
Design Data ◽  
Practical Applications ◽  
Other Hand ◽  
Gauge Section

The primary objective of the present paper is to depict the mechanical behavior of high density polyethylene, (HDPE), pipes under different loading conditions with different specimen geometries to provide the designer with reliable design data relevant to practical applications. Therefore, it is necessary to study the effect of strain rate, ring configuration, and grip or fixture type on the mechanical behavior of dumb-bell-shaped, (DBS), and ring specimens made from HDPE pipe material. DBS and ring specimens are cut from the pipe in longitudinally, and circumferential (transverse) direction respectively. On the other hand, the ring specimen configuration is classified into two types; full ring, (FR), and notched ring, (NR) (equal double notch from two sides of notched ring specimen) specimens according to ASTM D 2290-12 standard. Tensile tests are conducted on specimens cut out from the pipe with thickness 10 mm at different crosshead speeds (10–1000 mm/min), and ambient temperature, Ta = 20 °C to investigate the mechanical properties of DBS, and ring specimens. In the case of test specimens taken from longitudinal direction from the pipe a necking phenomenon before failure appears at different locations along the gauge section. On the other hand, the fracture of NR specimens occurs at one notched side. The results demonstrated that the NR specimen has higher yield stress than DBS, and FR specimens at all crosshead speeds. The present experimental work reveals that the crosshead speed has a significant effect on the mechanical behavior of both DBS, and ring specimens. The fixture type plays an important role in the mechanical behavior for both FR and NR specimens at all crosshead speeds.

scholarly journals Mullins–Sekerka stability analysis for melting-freezing waves in helium

1994 ◽  
Vol 5 (1) ◽  
pp. 21-37
Author(s):  
Joseph D. Fehribach
Keyword(s):  
Surface Tension ◽  
Growth Rate ◽  
Stability Analysis ◽  
Original Problem ◽  
The Other ◽  
Field Conditions ◽  
System Of Equations ◽  
Far Field ◽  
Other Hand ◽  
The Stability

This paper considers the stability of melt-solid interfaces to eigenfunction perturbations for a system of equations which describe the melting and freezing of helium. The analysis is carried out in both planar and spherical geometries. The principal results are that when the melt is freezing, under certain far-field conditions, the interface is stable in the sense of Mullins and Sekerka. On the other hand, when the solid is melting (at least when the melting is sufficiently fast), the interface is unstable. In some circumstances these instabilities are oscillatory, with amplitude and growth rate increasing with surface tension and frequency. The last section considers the original problem of Mullins and Sekerka in the present notation.

Microstructural Factors Affecting the Deformation Behavior of Mg12ZnY LPSO-Phase Alloys

2012 ◽  
Vol 706-709 ◽  
pp. 1158-1163 ◽  
Author(s):  
Koji Hagihara ◽  
Akihito Kinoshita ◽  
Yoshihiro Fukusumi ◽  
Michiaki Yamasaki ◽  
Yoshihito Kawamura
Keyword(s):  
Plastic Deformation ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Basal Slip ◽  
The Other ◽  
Factors Affecting ◽  
Lpso Phase ◽  
Long Period ◽  
Other Hand

Microstructural factors that govern the plastic deformation of the long-period stacking ordered (LPSO) phase were clarified. The decrease in length of the long-axis for the plate-like shape of LPSO-phase grains increases the yield stress of the alloy in which basal slip is predominant in deformation. On the other hand, the yield stress tended to increase as the thickness of the plate-like shapes of the grains decreased for the alloy in which the formation of deformation kinks carried the strain.

Pb-free solders: Predicting of some physicochemical properties of Ag–Cu–Sn material at different temperatures

2016 ◽  
Vol 15 (07) ◽  
pp. 1650062 ◽  
Author(s):  
Rachida M’chaar ◽  
Mouloud El Moudane ◽  
Abdelaziz Sabbar ◽  
Ahmed Ghanimi
Keyword(s):  
Surface Tension ◽  
Physicochemical Properties ◽  
Molar Volume ◽  
The Other ◽  
Ternary Alloys ◽  
Other Hand ◽  
Different Temperatures ◽  
Experimental Values ◽  
Increasing Temperature ◽  
Good Agreement

In this paper, the surface tension, molar volume and density of liquid Ag–Cu–Sn alloys have been calculated using Kohler, Muggianu, Toop, and Hillert models. In addition, the surface tension and viscosity of the Ag–Cu–Sn ternary alloys at different temperatures have been predicted on the basis of Guggenheim and Seetharaman–Sichen equations, respectively. The results show that density and viscosity decrease with increasing tin and increasing temperature for the all studied models. While the surface tension shows a different tendency, especially for the Kohler and Muggianu symmetric models. On the other hand, the molar volume increases with increase of temperature and tin compositions. The calculated values of surface tension and density of Ag–Cu–Sn alloys are compared with the available experimental values and a good agreement was observed.

A Microfluidic Manipulator for Enrichment and Alignment of Moving Cells and Particles

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Hsiu-hung Chen ◽  
Bingbing Sun ◽  
Kenny K. Tran ◽  
Hong Shen ◽  
Dayong Gao
Keyword(s):  
Microfluidic Channel ◽  
Particle Separation ◽  
The Other ◽  
Fluid Mixing ◽  
Combination Effect ◽  
Particle Distributions ◽  
Size Dependent ◽  
Other Hand ◽  
Size Based Separation ◽  
Channel Systems

Grooved structures have been widely studied in particle separation and fluid mixing in microfluidic channel systems. In this brief report, we demonstrate the use of patterning flows produced by two different sorts of grooved surfaces: single slanted groove series (for enrichment patterns) and V-shaped groove series (for focusing patterns), into a microfluidic device to continuously manipulate the flowing particles, including microbeads with 6 μm, 10 μm, and 20 μm in diameter and mouse dendritic cells of comparable sizes to the depth of the channel. The device with grooved channels was developed and fabricated by soft-lithographic techniques. The particle distributions after passing through the single slanted grooves illustrate the size-dependent enrichment profiles. On the other hand, particles passing through the V-shaped grooves show focusing patterns downstream, for the combination effect from both sides of single slanted grooves setup side-by-side. Compared with devices utilizing sheath flows, the focusing patterns generated in this report are unique without introducing additional flow control. The alignment of the concentrated particles is expected to facilitate the visualization of sizing and counting in cell-based devices. On the other hand, the size-dependent patterns of particle distributions have the potential for the application of size-based separation.

Unusual Effect of Oxygen on the Mechanical Behavior of a β-Type Titanium Alloy Developed for Biomedical Applications

2012 ◽  
Vol 706-709 ◽  
pp. 135-142 ◽  
Author(s):  
Mitsuo Niinomi ◽  
Masaaki Nakai
Keyword(s):  
Tensile Strength ◽  
Titanium Alloy ◽  
Mechanical Behavior ◽  
Titanium Alloys ◽  
Biomedical Applications ◽  
The Other ◽  
Excess Oxygen ◽  
Ω Phase ◽  
Other Hand ◽  
Effect Of Oxygen

Oxygen enhances the strength of titanium alloys in general; however, excess oxygen can make titanium alloys brittle. On the other hand, oxygen enhances the precipitation of the α phase and suppresses the formation of the ω phase. Thus, using the optimal amount of oxygen is important to improve the mechanical properties of titanium alloys. The role of oxygen in titanium alloys is still not well understood. The effect of oxygen on the mechanical behavior of a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (referred to as TNTZ), which is used for biomedical applications, was investigated in this study. Oxygen was found to stabilize the ω phase in TNTZ. This behavior of oxygen is unusual considering the known behavior of oxygen in titanium alloys: oxygen is known to suppress the formation of the ω phase in titanium alloys. A small amount of oxygen increases the tensile strength but decreases the ductility of TNTZ. On the other hand, a large amount of oxygen, of around 0.7 mass%, increases both the tensile strength and the ductility of TNTZ. This phenomenon is unexpected.

Electrochemical Characterization of Ti and Ti Base Alloys under Simulated Body Fluid Environment

2006 ◽  
Vol 512 ◽  
pp. 249-254 ◽  
Author(s):  
Shinji Fujimoto ◽  
H. Kusu ◽  
S. Katsuma ◽  
Masashi Sakamoto ◽  
Y.C. Tang
Keyword(s):  
Plastic Deformation ◽  
Simulated Body Fluid ◽  
Elastic Deformation ◽  
Body Fluid ◽  
The Other ◽  
Transient Current ◽  
Anodic Current ◽  
Current Increase ◽  
Other Hand ◽  
Fluid Environment

Ti and Ti based alloys are characterised by a continuous electrochemical monitoring and a rapid straining electrode technique in simulated body fluid environment. Materials examined are Ti, Ti-6Al-7Nb, Ti-6Al-4V and Ti-29Nb-13Ta-4.6Zr. Sterilized specimens were immersed in Hanks solution or Eagle’s minimum essential medium (MEM) solution. Electrode potential and polarization resistance were simultaneously and continuously measured up to 7 days. For all the specimens examined, the corrosion potential reached to a steady state in 2 days for both solutions. On the other hand, corrosion resistance increased monotonously for the period examined. Tensile specimens were rapidly elongated under potentio-static polarization to evaluate the transient current after exposure of newly-created surface. The anodic current appeared during both elastic and plastic deformation. For Ti alloys, anodic current started to increase gradually during elastic deformation, then increased more rapidly to reveal a maximum when straining was stopped, then decreased. Pure Ti, on the other hand, revealed the transient current after plastic deformation, but does not show any current increase during elastic deformation. The larger dissolution for a straining was observed as the following order; Ti, Ti-29Nb-13Ta-4.6Zr, Ti-6Al-7Nb, then Ti-6Al-4V.

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF STOCHASTIC THICKNESS EFFECTS IN DISCONTINUOUS FIBER COMPOSITES

2021 ◽  
Author(s):  
SEUNGHYUN KO ◽  
TROY NAKAGAWA ◽  
ZHISONG CHEN ◽  
JAMES DAVEY ◽  
TALAL ABDULLAH ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Computational Models ◽  
Orientation Distribution ◽  
Fiber Composites ◽  
The Other ◽  
Numerical Investigations ◽  
Aspect Ratios ◽  
Other Hand ◽  
Discontinuous Fiber

Discontinuous fiber composites (DFCs) made of chopped prepreg tapes have recently drawn the attention of the aerospace and automobile industries thanks to their flexible manufacturing capability. Because of the discontinuity in a form of prepreg tapes, the fibers easily follow the mold contours while maintaining comparable stiffness and strength to continuous quasi-isotropic laminates. Furthermore, the high production rates and part complexities enabled by DFCs make them a competitive alternative to the use of metals in several applications. However, one of the current roadblocks for the use of DFCs is the lack of reliable analysis methods to predict their mechanical behavior, which depends on different parameters such as platelet sizes, aspect ratios, and spatial distribution. In this paper, we first experimentally investigated tensile elastic modulus and strength of unnotched coupons made of two different platelet aspect ratios (square and narrow) for varying coupon thicknesses. From the experiments, the square platelets showed significant thickness effects on both elastic modulus and strength. The narrow platelets also had significant thickness effects on strength but relatively constant modulus with varying thicknesses. In both modulus and strength, the narrow platelets had higher average values with larger deviations. Next, we computationally examined the relationship between the platelet distributions and the corresponding thickness effects. To get a thorough understanding of the effects of the platelet distribution on the mechanical behavior, the analysis was performed in two steps. In the first step, computational models were generated utilizing a uniform platelet distribution. In the second step, the models were generated leveraging platelet orientation tensors obtained from X-ray micro-computed tomography characterization. It was found that the assumption of a uniform orientation distribution condition was sufficient to capture the average modulus and strength with varying thicknesses for both platelet sizes. However, the associated Coefficient of Variation (CoV) of the results were significantly underpredicted, especially in the case of narrow platelets. On the other hand, numerical results using the orientation tensor obtained via micro-CT provided significantly improved predictions of the CoVs with varying thicknesses. These numerical investigations suggest that, for parts manufactured in conditions of limited platelet flow, the average mechanical performance can be accurately predicted by stochastic Finite Element models featuring a uniform platelet orientation distribution. On the other hand, the prediction of the CoV of moduli and strengths urges the use of an accurate representation of the real platelet morphology.

Microtron Supraconducteur: Limitations, Pertes

1972 ◽  
Vol 50 (3) ◽  
pp. 298-300
Author(s):  
André Alaux ◽  
Jean-Claude Audet
Keyword(s):  
Magnetic Field ◽  
Critical Value ◽  
The Other ◽  
Other Hand ◽  
Operating Temperatures ◽  
The Magnetic Field ◽  
Theoretical Results

The use of superconductivity allows us to consider the operation at continuous rate of a microtron type accelerator. The authors show here some of the theoretical results they have obtained. These results deal with the losses by Joules effect on one hand, and on the other hand, with the energy limitations caused by the critical value of the magnetic field. The superconductive material considered is niobium and the operating temperatures are 4.2 and 1.85 °K.

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