scholarly journals The Behavior of Graphite Under Alternating Stress

1951 ◽  
Vol 18 (4) ◽  
pp. 345-348
Author(s):  
Leon Green
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Endurance Limit ◽  
Elevated Temperatures ◽  
Fatigue Properties ◽  
Polycrystalline Graphite ◽  
Short Time

Abstract The fatigue properties of grade AUF extruded polycrystalline graphite were investigated at ambient and elevated temperatures. Specimens cut parallel to the axis of extrusion were stressed in reversed bending at room temperature and at 3550 F. The endurance limit of this graphite was found to increase from 2500 psi at room temperature to about 4400 psi at 3550 F. The increase in endurance limit is correlative with the increase in short-time tensile strength with temperature observed in earlier studies of graphite.

High-Temperature Compression Testing of Graphite

1953 ◽  
Vol 20 (2) ◽  
pp. 289-294
Author(s):  
Leon Green
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
High Temperature ◽  
Stress Relaxation ◽  
Temperature Control ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Limited Degree ◽  
Relaxation Curves ◽  
Short Time

Abstract Experiments on the compression of graphite cylinders at elevated temperatures are described. It is found that the short-time compressive strength increases with temperature in the range from room temperature to 2000 C, a variation which is consistent with the previously reported behavior of the tensile strength. Photographs of typical modes of deformation and their corresponding stress-strain curves are presented, but a limited degree of temperature control renders the curves semiquantitative in nature. The large, mutually opposing influences of temperature and strain rate are illustrated by photographs of typical failures, and stress-relaxation curves manifest the plasticity of graphite at high temperatures.

Effect of Thermal Exposure on Tensile and Fatigue Properties of Clay Reinforced Nylon Nanocomposites

2015 ◽  
Vol 833 ◽  
pp. 52-55
Author(s):  
Yukiko Nakahara ◽  
Yusuke Kodama ◽  
Shi Jie Zhu ◽  
Arimitsu Usuki ◽  
Makoto Kato
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Thermal Exposure ◽  
Tensile Tests ◽  
Nylon 6 ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Oxidation Treatment ◽  
Exposure Temperature ◽  
Matrix Nanocomposite

In this paper, both nylon 6 and 2 wt% clay reinforced nylon 6 matrix nanocomposite were used for thermal exposure tests at temperatures of 80 oC and 120 oC and 150 oC, respectively. Then, the tensile tests and fatigue tests of the exposed specimens were conducted at room temperature. It was shown that the tensile strength in both nylon 6 and NCH-2 decreased with an increase in thermal exposure temperature. The brittle fracture occurred in the specimens exposed at 120 oC and 150 oC. After pre-oxidation treatment at 80 °C for 100 hours, the fatigue strength decreased 14% in nylon 6, and 8% in NCH-2. From this result, it was understood that the addition of clay in nylon 6 could suppress the decrease of fatigue strengths.

The Influence of Test Temperature on the Ratchetting Behavior of Type 304 Stainless Steel

1989 ◽  
Vol 111 (4) ◽  
pp. 378-383 ◽  
Author(s):  
M. B. Ruggles ◽  
E. Krempl
Keyword(s):  
Stress Level ◽  
Driving Force ◽  
Room Temperature ◽  
Maximum Stress ◽  
Elevated Temperatures ◽  
304 Stainless Steel ◽  
Short Time ◽  
Independent Behavior ◽  
Type 304 ◽  
Type 304 Stainless Steel

The zero-to-tension ratchetting behavior was investigated under uniaxial loading at room temperature and at 550, 600, and 650°C. In History I the maximum stress level of ratchetting was equal to the stress reached in a tensile test at one percent strain. For History II the maximum stress level was established as the stress reached after a 2100 s relaxation at one percent strain. Significant ratchetting was observed for History I at room temperature but not at the elevated temperatures. The accumulated ratchet strain increases with decreasing stress rate. Independent of the stress rates used insignificant ratchet strain was observed at room temperature for History II. This observation is explained in the context of the viscoplasticity theory based on overstress by the exhaustion of the viscous contribution to the stress during relaxation. The viscous part of the stress is the driving force for the ratchetting in History I. Strain aging is presumably responsible for the lack of short-time inelastic deformation resulting in a nearly rate-independent behavior at the elevated temperatures.

scholarly journals Mechanical and Dielectric Properties of Two Types of Si3N4 Fibers Annealed at Elevated Temperatures

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1498 ◽  
Author(s):  
Jie Zhou ◽  
Fang Ye ◽  
Xuefeng Cui ◽  
Laifei Cheng ◽  
Jianping Li ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Tensile Strength ◽  
Dielectric Properties ◽  
Electrical Resistance ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Fiber Bundles ◽  
Lower Content ◽  
Amorphous Silicon Nitride ◽  
Waveguide Method

The mechanical and dielectric properties of two types of amorphous silicon nitride (Si3N4) fibers prior to and following annealing at 800 °C were studied. The tensile strengths of the Si3N4 fiber bundles were measured using unidirectional tensile experimentation at room temperature, whereas the permittivity values were measured at 8.2–12.4 GHz using the waveguide method. The results demonstrated that the tensile strength and dielectric properties of Si3N4 fibers were correlated to the corresponding composition, microstructure, and intrinsic performance of electrical resistance. The Si3N4 fibers with a lower content of amorphous SiNxOy presented an improved thermal stability, a higher tensile strength, a higher conductivity, and a significantly stable wave-transparent property. These were mainly attributed to the highly pure composition and decomposition of less amorphous SiNxOy.

Effect of Plating Thickness on Fatigue Strength of Galvanized Steel

2020 ◽  
Vol 841 ◽  
pp. 3-8
Author(s):  
Kayo Hasegawa ◽  
Tatsuo Hayashi ◽  
Motoaki Morita ◽  
Shinichi Motoda
Keyword(s):  
Tensile Strength ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Main Crack ◽  
Immersion Time ◽  
Room Temperature ◽  
Columnar Structure ◽  
Galvanized Steel ◽  
Fatigue Properties ◽  
Plating Layer

Effect of the plating thicknesses on tensile and fatigue properties of hot-dip galvanized steel at room temperature was evaluated. The galvanized steel with thickness of 100 μm and 200 μm were prepared. Both microstructures of η-phase and δ1-phase were similar with each other. In the comparison with the galvanized steel with thickness of 100 μm, the microstructure of ζ-phase for the galvanized steel with thickness of 200 μm was blunt columnar structure due to long immersion time. Tensile and fatigue strengths for a galvanized steel are sensitive to the microstructure of the galvanized layer. The tensile strength and the strength of fatigue limit for the galvanized steel with thickness of 200 μm were smaller than that of 100 μm. In the galvanized steel with thickness of 200 μm, the peeling at plating layer easily occurred. The exfoliated sites have the potential to become subcracks. As the result, the main crack may propagate at early cycles.

Correlation of Tensile Strength with Brittle Points of Vulcanized Diene Polymers

1947 ◽  
Vol 20 (2) ◽  
pp. 515-524
Author(s):  
A. M. Borders ◽  
R. D. Juve
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Practical Importance ◽  
Testing Temperature ◽  
Crack Growth Resistance ◽  
Polymer Composition ◽  
Copolymer Composition ◽  
General Observation ◽  
Brittle Point

Abstract For several years work has been carried on here to evaluate a large number of diene polymers and copolymers as rubberlike materials. The writers have observed that changes in polymer composition which result in improved tensile strength and crack-growth resistance of the vulcanizate cause an increase in low temperature stiffness and a rise in brittle point. This generalization seems to apply to tensile values measured at elevated temperatures as well as to those at room temperature. For example, a butadiene copolymer of dichlorostyrene can be made which, as a tread type of vulcanizate, exhibits a tensile strength of over 1500 pounds per square inch at 93° C, in comparison with 800 to 1000 pounds per square inch for GR-S in the same test tread formula at the same temperature. The brittle point of the butadiene-dichlorostyrene rubber, however, is −35° C or higher. GR-S treads in the same test have brittle points between − 55° and −60° C. Probably of greater practical importance is the fact that the vulcanizate with the higher brittle point is stiffer at temperatures well above the brittle point. The purpose of this investigation was to determine to what extent the maximum tensile strength of tread stocks of several synthetic rubbers varies with the temperature difference between the brittle point and the tensile testing temperature of each rubber. These data can then be used to judge the validity and extent of the general observation that changes in copolymer composition which increase strength also raise the brittle point.

High Cycle Fatigue Properties of Modified 9Cr-1Mo Steel at Elevated Temperatures

2012 ◽  
Author(s):  
Yoshiaki Matsumori ◽  
Jumpei Nemoto ◽  
Yuji Ichikawa ◽  
Isamu Nonaka ◽  
Hideo Miura
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Room Temperature ◽  
Structural Reliability ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Cyclic Softening ◽  
Fatigue Properties ◽  
Cycle Fatigue

Since high-cycle fatigue loads is applied to the pipes in various energy and chemical plants due to the vibration and frequent temperature change of fluid in the pipes, the high-cycle fatigue behavior of the alloys used for pipes should be understood quantitatively in the structural reliability design of the pipes. The purpose of this study, therefore, is to clarify the high-cycle fatigue strength and fracture mechanism of the modified 9Cr-1Mo steel at temperatures higher than 400°C. This material is one of the effective candidates for the pipes in fast breeder demonstration reactor systems. A rotating bending fatigue test was applied to samples at 50 Hz in air. The stress waveform was sinusoidal and the stress ratio was fixed at −1. The fatigue limit was observed at room temperature and it was about 420 MPa. This value was lower than the 0.2% proof stress of this alloy by about 60 MPa. This decrease can be attributed to the cyclic softening of this material. The limited cycles at knee point was about 8×105 cycles. All fracture was initiated from a single surface crack and no inclusion-induced fracture was observed in the fracture surface by SEM. Thus, the high-cycle fatigue design based on the fatigue limit may be applicable to the modified 9Cr-1Mo steel at room temperature. The fatigue limit of about 350 MPa was also observed at 400°C, and it appeared at about 107 cycles, while it appeared at around 106 cycles at room temperature. Thus, it was confirmed that the fatigue strength of this alloy decrease with temperature. However, the fatigue limit didn’t appear at 550°C up to 108 cycles. The fatigue limit may disappear in this alloy at 550°C. It is very important, therefore, to evaluate the ultra-high cycle fatigue strength of this alloy at temperatures higher than 400°C.

Mechanical and Fatigue Properties of Cu-Al-Mn Shape Memory Alloys with Influence of Mechanical Cycling on Amplitude Dependence of Internal Friction at Room Temperature

2008 ◽  
Vol 137 ◽  
pp. 145-154 ◽  
Author(s):  
Agnieszka Mielczarek ◽  
Werner Riehemann ◽  
Sönke Vogelgesang ◽  
Babette Tonn
Keyword(s):  
Tensile Strength ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Strain Amplitude ◽  
Room Temperature ◽  
Fracture Strain ◽  
Fatigue Properties ◽  
Amplitude Dependence ◽  
Multiple Phase ◽  
Mechanical Cycling

The mechanical and fatigue properties of Cu - Al - Mn shape memory alloys with different phase fractions at room temperature were investigated. The specimens with different chemical compositions (Al: 8.9 - 12.5 wt. % and Mn: 3.3 - 9.3 wt. %) were tensile loaded with 10-3 s-1 tensile strain rate. Austenitic specimens have the highest tensile strength and fracture strain. Yield strength, tensile strength and elongation of martensitic alloys were lower compared with austenitic alloys. Fracture strain of martensitic alloys depend only little on the chemical composition. Specimens of martensitic, austenitic and three different multiple phase specimens were tested in the high cycle fatigue range at room temperature. The Woehler curves for multiple specimens depend on the phase fraction at testing temperatures. Different elements as Co, Ni, Fe and Si were alloyed to CuAl11.6Mn5. All decreased the ductility of the specimens, and their fatigue properties. Maxima could be detected in the strain amplitude dependence of damping for multiple phase specimen. These maximum are shifted to lower damping and to higher strains with increasing number of mechanical cycles, compared to the as cast condition for not cycled specimen. The strain amplitude dependence of damping in martensitic and austenitic Cu – Al – Mn shape memory alloys does not change much during mechanical cycling.

Structure and Fatigue Properties of Cr-Ni-Ti Austenitic Steel after Equal Channel Angular Pressing

2014 ◽  
Vol 783-786 ◽  
pp. 2611-2616 ◽  
Author(s):  
Sergey V. Dobatkin ◽  
Werner Skrotzki ◽  
Vladimir Terent’ev ◽  
Olga Rybalchenko ◽  
Andrey Belyakov ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Equal Channel Angular Pressing ◽  
Room Temperature ◽  
Fatigue Properties ◽  
Subgrain Structure ◽  
Structural Elements ◽  
High Angle ◽  
Structural Element ◽  
Angular Pressing ◽  
Element Size

After equal channel angular pressing (ECAP) at room temperature in 08%C-18%Cr-10%Ni-Ti steel grain-subgrain structure with the size of structural elements of 100-250 nm, volume of high angle boundaries (HAB) about 59% and 38% of martensite is formed. ECAP at 400°C results in fully austenitic structure with the structural element size of 100-400 nm and volume of HAB ~54%. ECAP increases the ultimate tensile strength of 08%C-18%Cr-10%Ni-Ti steel by 1.5 - 2 times, the yield stress by 3.8 - 5.2 times, the fatigue limit - by 1.4 - 1.7 times, however the ductility is reduced. Fatigue strength is enhanced by the refinement of the structure and twinning in the austenite during ECAP and due to intensive dynamic twinning, partial martensitic transformation and increasing of the volume of HAB during cyclic deformation.

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