Low Temperature Relaxation Phenomena in Rubber-Like Polymers Subjected to Low Deformation

1972 ◽  
Vol 45 (1) ◽  
pp. 71-81
Author(s):  
G. M. Bartenev ◽  
A. M. Kucherskii
Keyword(s):  
Relaxation Time ◽  
Critical Stress ◽  
Glassy State ◽  
Strong Dependence ◽  
Relaxation Phenomena ◽  
3 Dimensional ◽  
Critical Stresses ◽  
New Process ◽  
Temperature Relaxation ◽  
Small Deformations

Abstract 1. A new relaxation process was discovered which explains the change, at critical tensile stresses (0.1–0.5 kg/cm2), in the elasticity of rubber-like polymers subjected to small deformations. This new process is characterized by relatively low activation energies (weak dependence of temperature on relaxation time) and kinetic units that are large (strong dependence of relaxation time on stress). The kinetic stress is a function of the temperature and for rubbery polymers it is reduced to zero, at 40° –60° C. 2. The mechanism of this phenomenon is elucidated by the existence of ordered, supermolecular microregions forming, with the free chains of 3-dimensional networks, supplementary bundles of non-chemical origin which disintegrate under, critical stresses. The activities observed are analogous to the processes of forced-elastic deformation in the same polymers in the glassy state. The critical stress is analogous to the limit of forced elasticity at low second order (glass) transition temperatures.

scholarly journals Critical Stresses in Materials with Cracks

2019 ◽  
Vol 70 (7) ◽  
pp. 2442-2446
Author(s):  
Simona Eugenia Manea ◽  
Vali Ifigenia Nicolof ◽  
Teodor Sima
Keyword(s):  
Fracture Mechanics ◽  
Critical Stress ◽  
Crack Width ◽  
Crack Depth ◽  
Equivalent Stress ◽  
Critical Energy ◽  
Material Behavior ◽  
Experimental Results ◽  
Critical Stresses ◽  
Mechanics Concepts

The fracture mechanics concepts, as well as the concepts introduced on the basis of principle of critical energy, correlated with strength of materials with cracks is analysed. The equivalent stress method of strength was applied to cracked materials, by using the concept of local critical stress. This one depends on the material behavior and the deterioration due to crack. Experimental results have been obtained with specimens of OL304 steel with different cracks. The influence of crack depth and crack width is put into evidence.

Micro Cutting of Sapphire

2012 ◽  
Vol 523-524 ◽  
pp. 99-104 ◽  
Author(s):  
Takashi Matsumura ◽  
Yuki Endo ◽  
Hideyuki Ozawa
Keyword(s):  
Surface Finish ◽  
Critical Stress ◽  
Extreme Environments ◽  
Indentation Test ◽  
Cutting Parameters ◽  
Crystal Plane ◽  
Depth Of Cut ◽  
Micro Cutting ◽  
3 Dimensional ◽  
Ae Signal

Sapphire has high mechanical strength at high temperatures and high pressure. Thus, micro devices made of sapphire are expected to be used in extreme environments such as aerospace, defense and marine. Then, the machining technology is required for manufacturing of 3 dimensional shapes. The paper discusses the micro cutting process of sapphire to determine the applicable cutting parameters in planing and milling. First, the critical stress at which crack initiation occurs is measured in the indentation test with detecting AE signal. The critical stress of sapphire is beyond 22.6 GPa, which is much higher than those of glasses. Then, the critical depths of cut, maximum depths of cut in which crack-free surfaces were finished, were measured in cutting of r crystal plane. The critical depth of cut is maximized when the cutting is performed in a crystal axis direction. In milling of sapphire, adhesion of chip onto the surface finish should be considered as well as brittle fracture. In milling of r crystal plane, the surface finish is improved better than those of the other crystal planes. Adhesion of material can also be controlled by supplying lubrication.

Novel Synthesis Process and Characterization of Li-Mn-O Spinels for Rechargeable Lithium Batteries

1997 ◽  
Vol 496 ◽  
Author(s):  
Toshimi Takada ◽  
Hirotoshi Enoki ◽  
Etsuo Akiba ◽  
Takenori Ishizu ◽  
Tatsuo Horiba
Keyword(s):  
Strong Dependence ◽  
Lattice Parameter ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
Rechargeable Lithium Batteries ◽  
Rietveld Refinements ◽  
Synthesis Conditions ◽  
New Process ◽  
Homogeneous Composition

ABSTRACTA new process has been developed for the synthesis of well-crystallized Li-Mn-O spinels with a homogeneous composition Li[LixMn2-x]O4 (0.0≤x≤0.333) using the stoichiometry mixtures of lithium acetate and manganese nitrate as starting materials. The crystal structure of these compounds was studied with Rietveld refinements of the X-ray diffraction profiles. The lattice parameter of the spinels shows a strong dependence on the composition and manganese oxidation state. SEM micrographs indicate that the crystallites appear as single crystals. The size of the crystallites are in the range of 0.1 – 2μm, depending on the synthesis conditions. Samples with x≤0.125 show good electrode performance for the cell Li/Li1+xMn2-xO4 in the 4V region, whereas Li4Mn5O2 (x=0.333) spinels show good cyclability with a rechargeable capacity of over 100mAh/g in the 3V region.

Thermal equilibration of samples for neutron scattering

2013 ◽  
Vol 46 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Tobias K. Herman ◽  
Sarah C. Parks ◽  
Julia Scherschligt
Keyword(s):  
Relaxation Time ◽  
Neutron Scattering ◽  
Material Properties ◽  
Thermal Relaxation ◽  
Sample Cell ◽  
Time Constants ◽  
Thermal Equilibration ◽  
Temperature Relaxation ◽  
Relaxation Time Constants ◽  
Selection Of

Temperature relaxation and equilibration of samples for neutron scattering was investigated in a selection of samples and sample cells within the range of 5–300 K. A simple model was developed that relates thermal relaxation time constants to material properties of the sample and sample cell. This model should facilitate extension of this study to prediction of thermal behavior in other systems.

scholarly journals Oбобщенный кинетический критерий перехода жидкость--стекло

2020 ◽  
Vol 62 (10) ◽  
pp. 1706
Author(s):  
Д.С. Сандитов ◽  
В.В. Мантатов ◽  
С.Ш. Сангадиев
Keyword(s):  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Cooling Rate ◽  
Glassy State ◽  
Fluctuation Volume ◽  
Dimensionless Constant ◽  
Transition Criterion

Using the model of delocalized atoms, a substantiation and generalization of the Schmelzer glass transition criterion is proposed. In contrast to the Bartenev and Volkenstein - Ptitsyn approaches, in the generalized kinetic glass transition criterion, along with the relaxation time and the cooling rate of the melt, the glass transition temperature and an almost universal dimensionless constant appear, which is determined by the fraction of the fluctuation volume frozen at the glass transition temperature. The idea is developed that the liquid goes into a glassy state when its cooling rate q reaches a certain fraction of C_g of the characteristic cooling rate q_g=(T_g/taug), which is closely related to the relaxation time of the structure tau_g at the glass transition temperature T_g.

Calculated Spin-lattice Relaxation of 103Ru Compared with Low Temperature Quadrupole Orientation Measurements

1994 ◽  
Vol 49 (1-2) ◽  
pp. 395-400 ◽  
Author(s):  
R. Markendorf
Keyword(s):  
Relaxation Time ◽  
Low Temperature ◽  
Reference Value ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Axially Symmetric ◽  
Quadrupole Field ◽  
Spin Lattice ◽  
Temperature Relaxation

Abstract The spin-lattice relaxation time T1 in 103Ru has been determined on the basis of the Dirac theory and strict relativistic band structure calculations. The low temperature relaxation time T(of 103Ru in an axially symmetric quadrupole field and the quadrupole moment Q have been measured by Green and Stone using the technique of low temperature quadrupole orientation. For the usual reference value T1 T, which corresponds to relaxation in a Zeeman spectrum, they obtain 39(6) sK, which exceeds our value by 134%. This large discrepancy is attributed to the fact that the spin relaxation by direct quadrupole scattering of conduction electrons, the so-called Mitchell contribution, is dominant. According to our calculations it amounts to 81% of the total relaxation rate. This contribution could not be included in the evaluation of the experimental data.

Analysis of Nonlinear Local Buckling of Crane Telescopic Boom

2013 ◽  
Vol 387 ◽  
pp. 197-201 ◽  
Author(s):  
Xin Lei Huang ◽  
Ai Min Ji
Keyword(s):  
Critical Stress ◽  
Parametric Design ◽  
Local Buckling ◽  
Initial Imperfection ◽  
Arc Length ◽  
Ansys Software ◽  
Nonlinear Buckling ◽  
Critical Stresses ◽  
Linear Buckling ◽  
Nonlinear Buckling Analysis

The problems of nonlinear local buckling of telescopic boom of truck crane in the practical working condition were studied. The arc-length method of nonlinear buckling analysis was introduced. And the corresponding solving steps were given. Based on ANSYS software and redevelopment of ANSYS with APDL (ANSYS Parametric Design Language), the solution of critical stress of nonlinear local buckling of the boom was obtained. The critical stress values of the linear buckling and those of the nonlinear buckling of the boom were compared. The influence of different initial imperfection on the critical stresses of nonlinear local buckling of the rectangular, hexagonal and dodecagonal sectional boom was analyzed. The results indicate that the presented method can solve the problems of the nonlinear local buckling of telescopic boom of truck crane effectively.

Hot-electron-temperature relaxation time in a two-dimensional electron gas: AlGaN/GaN at 80 K

2002 ◽  
Vol 92 (8) ◽  
pp. 4490-4497 ◽  
Author(s):  
A. Matulionis ◽  
R. Katilius ◽  
J. Liberis ◽  
L. Ardaravičius ◽  
L. F. Eastman ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Electron Temperature ◽  
Electron Gas ◽  
Two Dimensional ◽  
Hot Electron ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Temperature Relaxation ◽  
Dimensional Electron Gas

scholarly journals CO2 Adsorption: Experimental Investigation and CFD Reactor Model Validation

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Ronald W. Breault ◽  
Lawrence J. Shadle ◽  
James L. Spenik ◽  
E. David Huckaby
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Time Series Data ◽  
Series Data ◽  
Reactor Model ◽  
Time Duration ◽  
Cfd Simulations ◽  
3 Dimensional ◽  
New Process ◽  
Adsorption Processes

The National Energy Technology Laboratory is investigating a new process for CO2 capture from large sources such as utility power generation facilities as an alternative to liquid amine based adsorption processes. Many of these advanced dry processes are based upon sorbents composed of supported polyamines. In this analysis, experiments have been conducted in a laboratory-scale fluidized bed reactor and compared to CFD reactor predictions using kinetics obtained from TGA tests. Batch experiments were conducted by flowing a mixture of CO2, H2O, and N2 (simulated flue gas) through a fluidized bed of sorbent material. The exit gas composition time series data is compared to CFD simulations using a 3-dimensional nonisothermal reacting multiphase flow model. The effects of the gas flow rate, distributor design, and particle size are explored through the CFD simulations. It is shown that the time duration for CO2 adsorption decreased for an increase in the gas flow. Fluid bed hydrodynamics indicated that there were regions in the reactor where the inert FCC particles segregated and defluidized; without adversely affecting the capacity of the sorbent to adsorb CO2. The details of the experimental facility and the model as well as the comparative analysis between the data and the simulation results are discussed.

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