Prediction of Yield in Ductile Materials Operating at Creep Temperatures

1977 ◽  
Vol 99 (3) ◽  
pp. 425-428
Author(s):  
G. M. Kurajian ◽  
T. Y. Na
Keyword(s):  
Experimental Data ◽  
Elevated Temperature ◽  
Yield Strength ◽  
Yield Point ◽  
Room Temperature ◽  
Ductile Metals ◽  
Ductile Materials ◽  
Machine Element ◽  
Creep Temperature ◽  
Good Agreement

Utilizing a thermodynamic approach, this paper provides the designer with formulations and data so that he can obtain or verify, and then employ, the yield strength (or yield point) value he may desire in the design of a particular ductile machine element operating in the creep temperature range. A previous paper by the authors [1] dealt with the prediction of failure of such elements in the range between room temperature and the lower creep temperature. Thus, the present paper in conjunction with [1], and the references in both, is to provide a thermodynamic explanation for failure of such elements operating in elevated temperature environments ranging from room through creep temperatures. Specific applications are taken for three selected categories of steel with good agreement between the theory and experimental data. However, with necessary data, the procedures in this paper, as it was in [1], is expected to be applicable to other ductile metals as well.

Prediction of Failure in Ductile Machine Elements Operating at Elevated Temperatures

1976 ◽  
Vol 98 (3) ◽  
pp. 1062-1065
Author(s):  
G. M. Kurajian ◽  
T. Y. Na
Keyword(s):  
Elevated Temperatures ◽  
State Of The Art ◽  
Design Practice ◽  
Ductile Metals ◽  
Ductile Materials ◽  
Machine Element ◽  
Distortion Energy ◽  
Machine Elements ◽  
Sound Theoretical Basis ◽  
Good Agreement

This paper provides the designer with formulations and data so that he can more confidently design a ductile machine element, operating at elevated temperatures, by employing obtainable strength data at those temperatures. The paper begins by taking a panoramic view of the state of the art regarding a procedure for designing such elements, under such conditions, on the basis of stress vs. strength. Then, the paper combines the basic principle of the distortion-energy theory of failure, long recognized as the best theory of failure for ductile materials by well documented experiments, with thermodynamic behavioral and mechanical properties. This combination and accompanying study result in formulation, information and data so that the validity of the aforementioned design practice is given a sound theoretical basis. Specific applications are taken for various categories of steel with very good agreement between the theory and experimental data. However, with necessary data, the procedure can be applied to other ductile metals as well.

Three-Dimensional Numerical Analysis for Bolted Flange Joints Considering Effect of Creep

2018 ◽  
Author(s):  
Lewen Bi ◽  
Lanzhu Zhang
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Numerical Analysis ◽  
Yield Strength ◽  
Room Temperature ◽  
Three Dimensional ◽  
Short Term ◽  
Flange Connection ◽  
Petroleum Chemical ◽  
Bolted Flange

Bolted flange joints are widely used in petroleum, chemical, nuclear and power industries, etc. With more and more devices are used at high temperature, the performance of flange connections becomes more complex, especially with creep of different components in flange connection. At elevated temperature, with the loss of bolt force and gasket force due to creep, the joints are prone to leak. Based on this, this paper analyzed the relaxation of bolt force at elevated temperature due to creep of bolt, flange and gasket separately and simultaneously. Besides, the influence of different initial installation stress of bolts was also studied. The results showed bolted flange joints relaxed due to gasket creep during early short term service. However, contribution of bolt and flange creep became more and more significant with the extension of time. With considering the creep of bolt, flange and gasket simultaneously, 50% to 60% of the bolt material yield strength at room temperature was recommended as the bolt initial installation stress for the joint case studied in this paper.

LARGE ROOM TEMPERATURE MAGNETORESISTANCE IN (La0.7Sm0.3)0.7Sr0.3MnO3/Agx COMPOSITES

2005 ◽  
Vol 19 (30) ◽  
pp. 4467-4473 ◽  
Author(s):  
XIAO-BO YUAN ◽  
YI-HUA LIU ◽  
CHENG-JIAN WANG ◽  
LIANG-MO MEI
Keyword(s):  
Experimental Data ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Composite System ◽  
Molar Ratio ◽  
Ag Addition ◽  
Brillouin Function ◽  
Spin Clusters ◽  
Good Agreement

The effects of Ag addition in the composite ( La 0.7 Sm 0.3)0.7 Sr 0.3 MnO 3/ Ag x (abbreviated as LSSMO/Ag x) has been studied. The results showed that Ag addition induces the decrease in resistivity (ρ) due to the improvement of grain boundaries resulted from the segregation of Ag on the grain surfaces. In addition, 27% molar ratio of Ag addition induces a large room temperature magnetoresistance (MR) ratio of 35%. The good agreement of experimental data with Brillouin function indicates that the MR behavior in this composite system accounts for the spin-dependent hopping of the electrons between the spin clusters.

Ligand Redistribution Equilibria in Aqueous Fluoroberyllate Solutions

1998 ◽  
Vol 53 (11) ◽  
pp. 1294-1300 ◽  
Author(s):  
Michael Schmidt ◽  
Hubert Schmidbaur
Keyword(s):  
Experimental Data ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Individual Species ◽  
Ph Values ◽  
Exchange Processes ◽  
The Individual ◽  
Good Agreement

The composition of aqueous fluoroberyllate solutions has been studied by 9Be and 19F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]- , and [BeF4]2-. These equilibria are shifted towards [BeF4]2- at high pH. No polynuclear fluoroberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.

An Electrical Method for Failure Prediction in Ductile Machine Elements at Elevated Temperatures

1978 ◽  
Vol 100 (4) ◽  
pp. 614-618
Author(s):  
G. M. Kurajian ◽  
T. Y. Na
Keyword(s):  
Electrical Resistivity ◽  
Critical Stress ◽  
Elevated Temperatures ◽  
Failure Prediction ◽  
Electrical Method ◽  
Conservation Of Energy ◽  
Ductile Metals ◽  
Machine Element ◽  
Machine Elements ◽  
Good Agreement

This paper provides the designer with an electrical method for failure prediction in ductile machine elements operating at elevated temperatures from room through the creep range. The law of conservation of energy, electrical considerations, and electrical properties are employed to result in a formulation. The formulation enables the designer to obtain, or verify, and then employ the critical stress value he requires in the design of a particular machine element operating at a given elevated temperature. It is shown that this critical stress value may be calculated simply by knowing the electrical resistivity value at the operating temperature, and the critical stress and electrical resistivity values at a datum (room) temperature. Specific applications are taken for various categories of steels with very good agreement between the theory and experimental data. The formulation is deemed to be applicable to other ductile metals as well.

Nernst–Ettingshausen Effects in GaxIn1–xAs alloys

1973 ◽  
Vol 51 (22) ◽  
pp. 2369-2375 ◽  
Author(s):  
Denis J. E. Demars ◽  
John C. Woolley
Keyword(s):  
Experimental Data ◽  
Magnetic Fields ◽  
Effective Mass ◽  
Room Temperature ◽  
Optical Scattering ◽  
Temperature Measurements ◽  
Scattering Coefficient ◽  
Alloy Sample ◽  
Alloy Scattering ◽  
Good Agreement

Room temperature measurements of longitudinal and transverse Nernst–Ettingshausen coefficients [Formula: see text] have been made on samples of GaxIn1–xAs alloys for a range of magnetic fields (B) up to 3.2 Wb/m2. Previous theoretical expressions for the values of these coefficients have been extended to the case of electrons in a single Kane band, and hence expressions for [Formula: see text] and [Formula: see text] obtained in terms of B, the bottom of the band effective mass m0*, and the scattering coefficient s. Fitting of these expressions to the experimental data thus has given values of m0* and s for each alloy sample. The values of m0* are found to be in good agreement with those obtained previously from plasma reflectance work, while the values of s indicate that over most of the alloy range polar optical scattering is predominant, but that in the range 0.4 < x < 0.7, alloy scattering may also have some contribution.

Strain aging and breakaway strain amplitude of damping in NiAl and NiAlZr

1994 ◽  
Vol 9 (5) ◽  
pp. 1166-1173 ◽  
Author(s):  
A. Wolfenden ◽  
S.V. Raj ◽  
S.K.R. Kondlapudi
Keyword(s):  
Binding Energy ◽  
Yield Strength ◽  
Yield Point ◽  
Strain Amplitude ◽  
Strain Aging ◽  
Room Temperature ◽  
Young Modulus ◽  
Initial Strain Rate ◽  
Order Of Magnitude ◽  
Discontinuous Yielding

Extruded NiAl and NiAlZr alloys often show discontinuous yielding on strain aging in compression at room temperature. Two sets of experiments were conducted to understand the reasons for this yield-point behavior. First, strain-aging experiments were carried out on NiAl alloys containing O to 0.1 at. % Zr. The specimens were all deformed in compression at room temperature at a nominal initial strain rate of 1.1 × 10−4S−1, and the effect of annealing at 700 and 1200 K on the stress-strain curves and the yield strength was studied after an initial prestrain. While annealing at 700 and 1200 K consistently reduced the yield strength of both NiAl and NiAlZr, the effects were quite different. In the case of NiAl, annealing at 1200 K did not result in discontinuous yielding, whereas it generally resulted in a sharp yield point for the Zr containing alloys. Second, the PUCOT (piezoelectric ultrasonic composite oscillator technique) was used to measure the dynamic Young modulus, breakaway strain amplitude, and damping for the alloys. Only small differences were observed in the values of Young's modulus, but the breakaway strain was at least a factor of 2 to 3 lower for NiAl than for NiAlZr. The experimentally determined values of damping were used in the Granato-Lücke model to estimate the binding energy for NiAl. While the binding energy values were found to be in agreement with the calculated values of dislocation kink nucleation and migration energies in this material, to within an order of magnitude, other effects, such as dislocation pinning by quenched-in vacancies, cannot be ruled out. The observations made in this study suggest that the yield-point behavior in NiAl may be due to several factors, such as difficulties in double kink nucleation, and single kink migration, as well as dislocation-vacancy interactions; whereas, the yield-point behavior in the Zr-alloyed material is due at least in part to dislocation-solute interaction.

Effect of Nb content on the strength of Cu–Nb filamentary microcomposites

2000 ◽  
Vol 15 (9) ◽  
pp. 1889-1893 ◽  
Author(s):  
Sun Ig Hong
Keyword(s):  
Experimental Data ◽  
Yield Strength ◽  
Yield Stress ◽  
Plastic Flow ◽  
Volume Fraction ◽  
Strength Increase ◽  
Unit Cells ◽  
Nb Content ◽  
Good Agreement

The yield strength of Cu–Nb filamentary microcomposites was predicted as a function of Nb content by modifying the barrier strengthening model. To predict the variation of the yield strength with Nb content, the interfilamentary spacing was calculated as a function of Nb content on the basis of the assumption that Nb filaments are distributed regularly along the sides of triangular unit cells. The yield stress can be described as the sum of the substructural strengthening component and the filament boundary strengthening term. The good agreement between the prediction and the experimental data suggests that the strength increase in Cu–Nb filamentary microcomposites with increasing Nb content results mostly from increasing the volume fraction of Nb filaments, which act as barriers to plastic flow.

Elevated Temperature Tensile Behavior of Rheo-Cast 7075-T6 Al Alloy Produced by GISS Technique

2014 ◽  
Vol 881-883 ◽  
pp. 1597-1600 ◽  
Author(s):  
Narissara Mahathaninwong ◽  
Sirikul Wisutmethangoon ◽  
Thawatchai Plookphol ◽  
Jessada Wannasin ◽  
Suchart Chantaramanee
Keyword(s):  
Tensile Strength ◽  
Elevated Temperature ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Room Temperature ◽  
Tensile Behavior ◽  
Al Alloy ◽  
Elevated Temperature Tensile ◽  
Semi Solid ◽  
Increasing Temperature

Tensile properties of rheo-cast 7075-T6 Al alloy produced by Gas Induced Semi-Solid (GISS) technique was investigated as a function of temperatures from 25°C to 250 °C in order to assess the potent of high temperature applications. It was found that the ultimate tensile strength and yield strength of the alloy decreased steadily with increasing temperature. There was loss in strength of about 33% at 200°C and 46% at 250 °C comparing to the strength at room temperature. At T = 250 °C, the ultimate tensile strength and yield strength of the rheo-cast 7075-T6 Al alloy were higher than those of the wrought 7075-T651 Al alloy. Keyword: 7075 Al alloy; Gas Induced Semi Solid (GISS) technique; Elevated temperature tensile.

Springback Behavior of an Invar Sheet and Its Perforated Form

2006 ◽  
Vol 505-507 ◽  
pp. 781-786
Author(s):  
Yi Che Lee ◽  
Fuh Kuo Chen
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Test Results ◽  
Bending Tests ◽  
Predicted Values ◽  
Springback Behavior ◽  
Good Agreement

The springback behavior of an invar sheet and its perforated form were examined in the present study. The mechanical properties for invar sheet and perforated invar-sheet at elevated temperatures were first obtained from tensile tests. The test results suggest that both invar sheet and perforated invar-sheet have favorable formability at temperature higher than 200oC. An analytical model was also established to predict the springback of the invar sheet and its perforated form under bending conditions at various elevated temperatures. In order to verify the predicted results, the V-bending tests were conducted for the invar sheet at various temperatures ranging from room temperature to 300. The experimental data indicate that the springback decreases with the rise in temperature for both invar sheet and perforated invar-sheet. The good agreement between the experimental data and the predicted values confirms the validity of the proposed theoretical model as well.

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