Factors Affecting Choice of Working Stresses for High-Temperature Service

1933 ◽  
Vol 1 (3) ◽  
pp. 99-102
Author(s):  
P. G. McVetty
Keyword(s):  
High Temperature ◽  
Published Data ◽  
Creep Tests ◽  
Fundamental Study ◽  
Factors Affecting ◽  
Creep Characteristics ◽  
The Stability ◽  
Safe Working

Abstract This paper discusses the various methods which have been proposed to determine safe working stresses for high-temperature service. The question of the stability of alloys during the test and in subsequent service is considered, with particular emphasis upon probable changes in creep characteristics during long exposure to stress and temperature. It is shown that published data in general do not admit of extrapolation, and that attempts to estimate total creep in service from such data are not usually satisfactory. The author stresses the need for more fundamental study of the laws governing creep rather than creep tests of many different materials.

Factors Affecting the Stability of Scale Inhibitors Used for Capillary Injection in High Temperature Wells

2013 ◽  
Author(s):  
J. Rick Griffin ◽  
James R Johnstone ◽  
Terry E Cotter ◽  
Ashleigh E O'Brien
Keyword(s):  
High Temperature ◽  
Factors Affecting ◽  
The Stability

Microstructural Instability in Mosi2/Sic Nanolayers

1997 ◽  
Vol 3 (S2) ◽  
pp. 399-400
Author(s):  
Y.C. Lu ◽  
H. Kung ◽  
J-P Hirvonen ◽  
T.R. Jervis ◽  
M. Nastasi ◽  
...  
Keyword(s):  
High Temperature ◽  
Ion Irradiation ◽  
High Temperature Strength ◽  
Second Phase ◽  
Microstructural Stability ◽  
Factors Affecting ◽  
Structural Applications ◽  
Thermal Compatibility ◽  
Two Phases ◽  
The Stability

Thin film multilayers have been the focus of extensive studies recently due to the interesting properties they exhibit. Since the improvement in properties can be attributed directly to the unique nanoscale microstructures, it is essential to understand the factors affecting the microstructural stability in these nanolayer structures. The intermetallic compound, MoSi2, despite its superior oxidation resistance and high melting point, suffers from inadequate high temperature strength and low temperature ductility, properties which hinder its high temperature structural applications [1]. SiC is a potential second phase reinforcement due to its high temperature strength and thermal compatibility with MoSi2. The addition of SiC in a nanolayered configuration has been shown to exhibit significant increase in hardness after annealing [2]. It has also been shown that when annealed above 900°C, the layers break down and grain growth sets in, with a significant decrease in hardness and. Due to the lack of a thermochemical driving force, the two phases remain separate at all temperatures investigated. In this study, the stability of the MoSi2/SiC nanolayers structure under ion irradiation has been investigated.

Factors affecting the stability of Nafion conductivity at high temperature and relative humidity

Desalination ◽  
2006 ◽  
Vol 200 (1-3) ◽  
pp. 639-641 ◽  
Author(s):  
Mario Casciola ◽  
Giulio Alberti ◽  
Manolo Sganappa ◽  
Riccardo Narducci
Keyword(s):  
High Temperature ◽  
Relative Humidity ◽  
Factors Affecting ◽  
The Stability

scholarly journals The Influence of Macrostructure of Nickelbased Superalloys IN713C and MAR 247 on the Characteristics of High-temperature Creep

2014 ◽  
Vol 14 (4) ◽  
pp. 11-16 ◽  
Author(s):  
M. Cieśla ◽  
F. Binczyk ◽  
M. Mańka ◽  
R. Findziński
Keyword(s):  
High Temperature ◽  
Diffusion Mechanism ◽  
Morphological Characteristics ◽  
Deformation Mechanisms ◽  
High Temperature Creep ◽  
Creep Tests ◽  
Dislocation Mechanism ◽  
Waste Products ◽  
Temperature Creep ◽  
Creep Characteristics

Abstract The study consisted in assessing the influence of surface and volume modification on the characteristics of high-temperature creep of castings made of waste products of nickel-based superalloys IN 713C and the MAR-247. The results of high-temperature creep tests performed under conditions of two variants of research were analysed. The characteristics of creep according to variant I were obtained on the basis of earlier studies of these alloys with the parameters T=982°C, σ=150MPa [1]. Variant II included carrying out creep tests of alloy IN713C with the parameters T=760°C, σ =400MPa and alloy MAR247 with the parameters: T=982°C, σ=200MPa.Developed creep characteristics were compared with the results of these alloys with the parameters according to variant I of the study. It was observed that the conditions of experiments carried out depending upon the value of the creep test temperature and stress with the creep stability depends on the size of the macrograin (I variant of the studies) or such influence was not observed (II variant of the studies). Stability of samples with coarse structure in variant I of creep tests was significantly higher than the samples with fragmented grain. It was found that the observed stability conditions are dependent on the dominant deformation mechanisms under creep tests carried out - diffusion mechanism in variant I and a dislocation mechanism in variant II of the study. The conditions for the formation and growth of the cracks in the tested materials, including the morphological characteristics of their macro-and microstructure were tested

Preparation and Characterization of Nb-1Zr-0.1C Alloy Suitable for Liquid Metal Coolant Channels of High Temperature Reactors

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
S. Majumdar ◽  
J. Kishor ◽  
A. N. Behera ◽  
B. Vishwanadh ◽  
A. Borgohain ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Temperature ◽  
Mixed Oxides ◽  
Liquid Lead ◽  
Creep Tests ◽  
Prolonged Duration ◽  
Coated Alloy ◽  
High Temperature Reactors ◽  
The Stability ◽  
Electron Beam Melt

Abstract A novel process comprising of aluminothermic coreduction of mixed oxides followed by arc and electron beam melt refining was developed for preparation of Nb-1Zr-0.1C alloy. The parameters of the process were optimized by considering the thermodynamic (heat) and mass balance phenomenon. The ingots of the homogenized alloy produced after electron beam melt consolidation were further extruded into tubes. The alloy was vacuum annealed at 1350–1800 °C to study the stability of Nb2C and Nb(Zr)C carbide precipitates in the microstructure. Compression creep tests conducted at 900 and 1000 °C revealed a stress exponent value of 2 and activation energy of 508 kJ/mol. NbSi2-based coatings were developed on the Nb-1Zr-0.1C alloy tubes using pack siliconizing process. The coated alloy was tested for oxidation at 1250 °C, and corrosion in liquid lead-bismuth eutectic (LBE) alloy at 875 °C for prolonged duration. The silicide-coated alloy showed superior oxidation and LBE corrosion resistance at high temperatures. The alloy was found to be a promising material for coolant channels of high temperature reactors.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

Biodynamic Modeling of a Pedestrian Impact With a Rigid Frontal Guard of a Utility Vehicle

2010 ◽  
Author(s):  
Rasoul Moradi ◽  
Chandrashekhar K. Thorbole ◽  
Michael McCoy ◽  
Hamid M. Lankarani
Keyword(s):  
Front Surface ◽  
Body Region ◽  
Computational Technique ◽  
Surface Model ◽  
Published Data ◽  
Factors Affecting ◽  
Light Trucks ◽  
Accident Data ◽  
Facet Surface ◽  
The Impact

Accident data reveals that in most pedestrian accidents, the pedestrian head and lower extremity are vulnerable to serious injuries. The vehicle front geometry profile as well as the impact speed are important factors affecting the pedestrian kinematics and injury potential. In the US, accident data also shows that the fatality rate for pedestrian/light trucks and vans (LTV) impact is greater than that for the pedestrian/passenger-car impact. Addition of a front guard on light trucks and sports utility vehicles to mitigate damage during off-road activity or to provide mounting points for extra lights, makes the pedestrian more vulnerable to the impact. In this paper, a computational technique is utilized to study the influence of the added front guard on the impacted pedestrian. A CAD model of a typical commercial frontal guard is developed and converted into a rigid facet model, and attached to the vehicle front. The validated standing dummy model in the MADYMO code is used to simulate a pedestrian, and the rigid facet-surface model of a pickup truck is used to generate a vehicle front surface. This computational model is validated by comparing the pedestrian kinematics with the published data. This study demonstrates that the pedestrian mid body region is more vulnerable with the addition of guard on the vehicle. The result from this study facilitates a better understanding of a guard design and its geometry profile as required to protect vulnerable road users.

Creep Properties and Interfacial Microstructure of SiC Whisker Reinforced Si3N4

1989 ◽  
Vol 170 ◽  
Author(s):  
Håkan A. Swan ◽  
Colette O'meara
Keyword(s):  
High Temperature ◽  
Creep Resistance ◽  
Interfacial Microstructure ◽  
Deformation Mechanisms ◽  
Amorphous Films ◽  
Creep Tests ◽  
Creep Properties ◽  
High Temperature Exposure ◽  
Temperature Exposure

AbstractPreliminary creep tests were performed on SiC whisker reinforced and matrix Si3N4 material fabricated by the NPS technique. The material was extensively crystallised in the as received material, leaving only thin amorphous films surrounding the grains. No improvement in the creep resistance could be detected for the whisker reinforced material. The deformation mechanisms were found to be that of cavitation in the form of microcracks, predominantly at the whisker/matrix interfaces, and the formation of larger cracks. Extensive oxidation of the samples, as a result of high temperature exposure to air, was observed for the materials tested at 1375°C.

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