Experimental Verification of Constitutive Equations for Creep and Plasticity Based on Overlay Models

1983 ◽  
Vol 105 (3) ◽  
pp. 277-284 ◽  
Author(s):  
P. Meijers ◽  
F. Roode
Keyword(s):  
Plastic Deformation ◽  
Room Temperature ◽  
304 Stainless Steel ◽  
Model Parameters ◽  
General Description ◽  
Time Effects ◽  
Plastic Deformations ◽  
Biaxial Load ◽  
Theoretical Predictions ◽  
Good Agreement

A general description of creep and plastic deformation based on overlay models is presented. This includes the description of time effects during plastic deformation at room temperature. A detailed procedure to obtain the model parameters is also discussed. The description has been evaluated for a large number of uniaxial and biaxial load histories on thin walled tubes. The materials involved are a 2 1/4 Cr-1 Mo steel stabilized with Niobium (WN 1.6770) and a 304 stainless steel (WN 1.4948). The theoretical predictions of the plastic deformations are found to be sufficiently accurate. The evaluation of the phenomenological description for creep shows a fairly good agreement with the real creep deformation process. Special attention requires the description of softening due to microstructural changes.

An Arbitrarily Inclined Triangular UBET Element and Its Application to Combined Forging

1985 ◽  
Vol 107 (2) ◽  
pp. 134-140 ◽  
Author(s):  
D. Y. Yang ◽  
J. H. Kim ◽  
C. K. Lim
Keyword(s):  
Velocity Field ◽  
Room Temperature ◽  
Field Experiments ◽  
Velocity Fields ◽  
Admissible Velocity ◽  
Forming Load ◽  
Theoretical Predictions ◽  
Triangular Elements ◽  
Al 2024 ◽  
Good Agreement

A kinematically admissible velocity field is derived for a proposed arbitrarily inclined triangular UBET element. The method is applied to combined forging to show the flexibility of application. From the derived velocity fields upper-bound loads on the punch and deformed configurations are determined by optimizing some given parameters related with geometry and velocity field. Experiments on combined forging are carried out with annealed Al-2024 billets at room temperature for several punch shapes. The theoretical predictions both in the forming load and deformed configuration are in good agreement with the experimental results. It is shown that arbitrarily inclined triangular elements proposed in this work can effectively be used for the prediction of the forming load and deformation in combined forging and can be applied to other forming processes with flexibility.

Plastic Deformations in Single Crystals of FePd with the L10 Structure

2008 ◽  
Vol 1128 ◽  
Author(s):  
Katsushi Tanaka ◽  
Wang Chen ◽  
Kyosuke Kishida ◽  
Norihiko L. Okamoto ◽  
Haruyuki Inui
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Room Temperature ◽  
Positive Temperature ◽  
Plastic Deformations ◽  
L10 Structure ◽  
Critical Resolved Shear Stress

AbstractCompressive deformations of L10-ordered single crystals of FePd have been investigated from room temperature to 873 K. The critical resolved shear stress for superlattice dislocations is hard to determine resulting from buckling that occurs after a small amount of conventional plastic deformation. The CRSS for superlattice dislocations determined from yield stress is significantly larger than that of ordinary dislocations. The CRSS for octahedral glide of ordinary and superlattice dislocations are virtually independent of the temperature, and the positive temperature dependence of the yield stress is not observed for both, ordinary and superlattice dislocations, by the present experiments.

SELENIUM ISOTOPE EFFECTS IN THE REDUCTION OF SODIUM SELENITE AND OF SODIUM SELENATE

1966 ◽  
Vol 44 (4) ◽  
pp. 419-427 ◽  
Author(s):  
C. E. Rees ◽  
H. G. Thode
Keyword(s):  
Rate Constant ◽  
Sodium Selenite ◽  
Room Temperature ◽  
Isotope Effects ◽  
Sodium Selenate ◽  
Theoretical Predictions ◽  
Selenium Isotope ◽  
Use Of Models ◽  
Good Agreement

Selenium isotope effects in the reduction of sodium selenite and of sodium selenate have been studied. Rate constant ratios for the 76Se and 82Se species have been determined for the reactions Seiv → Se0 (1.017), Sevi → Seiv (1.018), and Se0 → Seiv (1.010) at room temperature. Theoretical predictions of the first two ratios, from the use of models in which the rate-controlling steps are assumed to be Se—O bond cleavages in SeO32− and SeO42−, respectively, lead to predictions in good agreement with experiment.

Experimental Investigation of the Biaxial Load-Extension Properties of Plain, Weft-Knitted Fabrics

1977 ◽  
Vol 47 (4) ◽  
pp. 233-239 ◽  
Author(s):  
Brian M. Macrory ◽  
J. Roger Mccraith ◽  
A. B. McNamara
Keyword(s):  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Experimental Results ◽  
Knitted Fabric ◽  
Knitted Fabrics ◽  
Test Instrument ◽  
Biaxial Load ◽  
Theoretical Predictions ◽  
End Use ◽  
Good Agreement

A test instrument is described which permits measurement of load and extension along the courses and wales of a knitted fabric as the latter is being extended in both directions simultaneously. The rates of extension may be chosen to deform the fabric in a variety of modes representative of end-use situations. Experimental results obtained for plain, weft-knitted fabrics using three different hosiery yarns are presented. Comparison is made with values predicted by the authors' theoretical analysis of the biaxially-loaded fabric configuration, and good agreement between the experimental results and the theoretical predictions is obtained.

Writing Laser Power Dependence of Second Harmonic Generation in an Optically Poled Azo-dye/polymer Film

2004 ◽  
Vol 846 ◽  
Author(s):  
C. H. Wang ◽  
Oliver Y.-H. Tai ◽  
Yuxiao Wang
Keyword(s):  
Laser Power ◽  
Azo Dye ◽  
Room Temperature ◽  
Second Harmonic ◽  
Writing Process ◽  
Experimental Result ◽  
Power Dependence ◽  
Theoretical Predictions ◽  
Azo Chromophore ◽  
Good Agreement

ABSTRACTThe time and power dependence of the optical poling process of an azo chromophore in the PMMA matrix at room temperature is investigated. A model previously proposed is used to account for the writing process of the optical poling of the chromophore/PMMA system. Theoretical predictions of the growth rate and the plateau SHG intensity are found to be in good agreement with the experimental result.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

A crystallographic analysis of the CoSi/Si(111) interface using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 574-575
Author(s):  
A.C. Daykin ◽  
C.J. Kiely ◽  
R.C. Pond ◽  
J.L. Batstone
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Room Temperature ◽  
Theoretical Method ◽  
Crystallographic Analysis ◽  
Si Substrate ◽  
Transmission Electron ◽  
Theoretical Predictions

When CoSi2 is grown onto a Si(111) surface it can form in two distinct orientations. A-type CoSi2 has the same orientation as the Si substrate and B-type is rotated by 180° degrees about the [111] surface normal.One method of producing epitaxial CoSi2 is to deposit Co at room temperature and anneal to 650°C.If greater than 10Å of Co is deposited then both A and B-type CoSi2 form via a number of intermediate silicides .The literature suggests that the co-existence of A and B-type CoSi2 is in some way linked to these intermediate silicides analogous to the NiSi2/Si(111) system. The phase which forms prior to complete CoSi2 formation is CoSi. This paper is a crystallographic analysis of the CoSi2/Si(l11) bicrystal using a theoretical method developed by Pond. Transmission electron microscopy (TEM) has been used to verify the theoretical predictions and to characterise the defect structure at the interface.

Electron microscope studies of the plastic deformation of ternary alloys based on GaAs

1990 ◽  
Vol 48 (4) ◽  
pp. 1120-1120
Author(s):  
R. Haswell ◽  
U. Bangert ◽  
P. Charsley
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Room Temperature ◽  
Stacking Faults ◽  
The Other ◽  
Ternary Alloys ◽  
Dislocation Mobility ◽  
Semiconducting Materials ◽  
Micro Indentation

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.

Room-Temperature Chemical Synthesis of C2

2019 ◽  
Author(s):  
Kazunori Miyamoto ◽  
Shodai Narita ◽  
Yui Masumoto ◽  
Takahiro Hashishin ◽  
Mutsumi Kimura ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Ground State ◽  
Room Temperature ◽  
Chemical Species ◽  
Quadruple Bond ◽  
Photon Excitation ◽  
Physical Energy ◽  
Theoretical Predictions ◽  
Carbon Arc ◽  
Inherent Nature

Diatomic carbon (C<sub>2</sub>) is historically an elusive chemical species. It has long been believed that the generation of C<sub>2 </sub>requires extremely high “physical” energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C<sub>2 </sub><i>in the ground state </i>is experimentally inaccessible. Here, we present the first “chemical” synthesis of C<sub>2 </sub>in a flask at <i>room temperature or below</i>, providing the first experimental evidence to support theoretical predictions that (1) C<sub>2 </sub>has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C<sub>2 </sub>serves as a molecular element in the formation of sp<sup>2</sup>-carbon allotropes such as graphite, carbon nanotubes and C<sub>60</sub>.

scholarly journals A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 830
Author(s):  
Julio Cesar Martinez-Garcia ◽  
Alexandre Serraïma-Ferrer ◽  
Aitor Lopeandía-Fernández ◽  
Marco Lattuada ◽  
Janak Sapkota ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymeric Nanocomposites ◽  
Mechanical Reinforcement ◽  
Future Studies ◽  
Three Phase ◽  
Theoretical Predictions ◽  
Filler Network ◽  
New Research ◽  
Good Agreement ◽  
Research Avenue

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

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