Dislocation nucleation from near surface void under static tensile stress in Cu

2011 ◽  
Vol 110 (2) ◽  
pp. 023509 ◽  
Author(s):  
A. S. Pohjonen ◽  
F. Djurabekova ◽  
K. Nordlund ◽  
A. Kuronen ◽  
S. P. Fitzgerald
Keyword(s):  
Tensile Stress ◽  
Dislocation Nucleation ◽  
Near Surface ◽  
Static Tensile ◽  
Static Tensile Stress

Creep Performance of Candidate SiC and Si3N4 Materials for Land-Based, Gas Turbine Engine Components

1997 ◽  
Vol 119 (4) ◽  
pp. 799-806 ◽  
Author(s):  
A. A. Wereszczak ◽  
T. P. Kirkland
Keyword(s):  
Tensile Stress ◽  
Gas Turbine ◽  
Test Data ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Fatigue Stress ◽  
Creep Stress ◽  
Static Tensile ◽  
Static Tensile Stress ◽  
Sintered Silicon

The tensile creep-rupture performance of a commercially available gas pressure sintered silicon nitride (Si3N4) and a sintered silicon carbide (SiC) is examined at 1038, 1150, and 1350°C. These two ceramic materials are candidates for nozzles and combustor tiles that are to be retrofitted in land-based gas turbine engines, and interest exists to investigate their high-temperature mechanical performance over service times up to, and in excess of, 10,000 hours (≈14 months). To achieve lifetimes approaching 10,000 hours for the candidate Si3N4 ceramic, it was found (or it was estimated based on ongoing test data) that a static tensile stress of 300 MPa at 1038 and 1150°C, and a stress of 125 MPa at 1350°C cannot be exceeded. For the SiC ceramic, it was estimated from ongoing test data that a static tensile stress of 300 MPa at 1038°C, 250 MPa at 1150°C, and 180 MPa at 1350°C cannot be exceeded. The creep-stress exponents for this Si3N4 were determined to be 33, 17, and 8 for 1038, 1150, and 1350°C, respectively. The fatigue-stress exponents for the Si3N4 were found to be equivalent to the creep exponents, suggesting that the fatigue mechanism that ultimately causes fracture is controlled and related to the creep mechanisms. Little success was experienced at generating failures in the SiC after several decades of time through exposure to appropriate tensile stress; it was typically observed that if failure did not occur on loading, then the SiC specimens most often did not creep-rupture. However, creep-stress exponents for the SiC were determined to be 57, 27, and 11 for 1038, 1150, and 1350°C, respectively. For SiC, the fatigue-stress exponents did not correlate as well with creep-stress exponents. Failures that occurred in the SiC were a result of slow crack growth that was initiated from the specimen’s surface.

Creep Performance of Candidate SiC and Si3N4 Materials for Land-Based, Gas Turbine Engine Components

1996 ◽  
Author(s):  
Andrew A. Wereszczak ◽  
Timothy P. Kirkland
Keyword(s):  
Tensile Stress ◽  
Gas Turbine ◽  
Test Data ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Fatigue Stress ◽  
Creep Stress ◽  
Static Tensile ◽  
Static Tensile Stress ◽  
Sintered Silicon

The tensile creep-rupture performance of a commercially available gas pressure sintered silicon nitride (Si3N4) and a sintered silicon carbide (SiC) is examined at 1038, 1150, and 1350°C. These two ceramic materials are candidates for nozzles and combustor tiles that are to be retrofitted in land-based gas turbine engines, and interest exists to investigate their high temperature mechanical performance over service-times up to, and in excess of, 10000 hours (≈ 14 months). To achieve lifetimes approaching 10000 hours for the candidate Si3N4 ceramic, it was found (or it was estimated based on ongoing test data) that a static tensile stress of 300 MPa at 1038 and 1150°C, and a stress of 125 MPa at 1350°C cannot be exceeded. For the SiC ceramic, it was estimated from ongoing test data that a static tensile stress of 300 MPa at 1038°C, 250 MPa at 1150°C, and 180 MPa at 1350°C cannot be exceeded. The creep-stress exponents for this Si3N4 were determined to be 33, 17, and 8 for 1038, 1150, and 1350°C, respectively. The fatigue-stress exponents for the Si3N4 were found to be equivalent to the creep exponents, suggesting that the fatigue mechanism that ultimately causes fracture is controlled and related to the creep mechanisms. Little success was experienced at generating failures in the SiC after several decades of time through exposure to appropriate tensile stress; it was typically observed that if failure did not occur on loading, then the SiC specimens most often did not creep-rupture. However, creep-stress exponents for the SiC were determined to be 57, 27, and 11 for 1038, 1150, and 1350°C, respectively. For SiC, the fatigue-stress exponents did not correlate as well with creep-stress exponents. Failures that occurred in the SiC were a result of slow crack growth that initiated from the specimen’s surface.

scholarly journals Influence of Micro-Arc Oxidation Coatings on Stress Corrosion of AlMg6 Alloy

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 356 ◽  
Author(s):  
Lesław Kyzioł ◽  
Aleksandr Komarov
Keyword(s):  
Tensile Stress ◽  
Stress Corrosion ◽  
Glass Container ◽  
Ceramic Coatings ◽  
Porosity Level ◽  
Protective Properties ◽  
Micro Arc Oxidation ◽  
Static Tensile ◽  
Static Tensile Stress ◽  
Prolonged Stress

This paper shows results of a study on the corrosion behavior of micro-arc oxidation (MAO) coatings sampled from the AlMg6 alloy. The alloy was simultaneously subjected to a corrosive environment and static tensile stress. For comparative purposes, the tests were run for both coated samples and samples without coatings. The research was conducted at a properly prepared stand; the samples were placed in a glass container filled with 3.5% NaCl aqueous solution and stretched. Two levels of tensile stress were accepted for the samples: σ1 = 0.8R0.2 σ2 = R0.2, and the tests were run for two time intervals: t1 = 480 h and t2 = 1000 h. Prolonged stress corrosion tests (lasting up to 1000 h) showed that the samples covered with ceramic coatings demonstrated significantly higher corrosion resistance than the samples without the coatings. Protective properties of the coating could be explained by its structure. Surface pores were insignificant, and their depth was very limited. The porosity level of the main coating layer was 1%. Such a structure of coating and its phase composition provided high protective properties.

Stress Corrosion—The Engineer̕ s View

1959 ◽  
Vol 63 (582) ◽  
pp. 354-365
Author(s):  
P. H. Wall
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Tensile Stress ◽  
Stress Corrosion ◽  
Atmospheric Corrosion ◽  
Corrosive Environment ◽  
Light Alloy ◽  
Exact Analysis ◽  
Static Tensile ◽  
Static Tensile Stress

Of all those forms of corrosion with which the engineer must deal, such as atmospheric corrosion, galvanic and fretting, stress corrosion is perhaps the most difficult to understand, to predict and to prevent.Unlike that other troublesome characteristic of metals, namely fatigue, which also defies exact analysis, it is caused by static tensile stress acting in a corrosive environment (in many cases, the atmosphere). This may be due to internal residual stress or externally applied assembly stress and under such circumstances the possibility of stress corrosion occurring is ever present and is not necessarily removed by the cessation of the working loads.Most alloys are susceptible to some degree ranging from those which suffer in practice to those which only exhibit the phenomena under exaggerated laboratory conditions. Some examples are railway locomotive boilers, stainless steel construction, commercial spot-welded construction and, of course, aeroplane structures in light alloy.

scholarly journals ‎‏FINDING PERCENTAGE OF BREAKDOWN STIMULATION OF ALUMINUM WIRES THAT OPERATES IN A CORROSIVE MEDIUM

2022 ◽  
Vol 26 (1) ◽  
pp. 87-94
Author(s):  
Mohammed Abdulateef Ahmed ◽  
Keyword(s):  
Tensile Stress ◽  
Electrical Energy ◽  
Electrical Current ◽  
Mechanical Resistance ◽  
Corrosive Environment ◽  
Aluminum Wire ◽  
Different Temperatures ◽  
Static Tensile ◽  
The Wire ◽  
Static Tensile Stress

The study of the duration of mechanical resistance to static tensile stress (withstand time) for an aluminum wire that being suffers from the corrosion effect stimulated by stray currents at different temperatures. Test device was designed and produced locally "in advance" in accordance with the specification (ASTM G103 - 97) to create static tensile stress of (1 N) on an aluminum wire of type ASTM (B231/B231M) with particular dimensions and utilized in the transmission of electrical energy, and when the wire is surrounded by a corrosive environment (NaCl solution) (3.5 % NaCl) at three different temperatures (25, 50, and 75 ° C) without any external electrical current causing corrosion; this symbolizes stray currents. Then compare the findings of that example to the results of the same wire's withstand time in the presence of an external electrical current generated by corrosion of type (D.C) by (5V & 3A). Following that, the resulting diagrams were analyzed, and it was discovered that the wire resistivity time (without the existence of stray currents and at a temperature of 25 ° C) completed (17 days), which is the longest duration of endure, and the lowest time of resistivity or resistance period (in the existence of an external electric current) is (18 hr.).Impact of (stray currents) at (75 ° C), and this is an indicator of the stray currents with corrosive environment temperatures on the resistance period (withstand duration) in the existence of static stress. The total stimulation increase is 1.9% between corrosion at 75°C and 25°C.

Nonlinear Elasticity of Poly (P-Phenylene Benzobisthiazole) (PBZT) Fibers

1988 ◽  
Vol 134 ◽  
Author(s):  
H. Jiang ◽  
R.K. Eby ◽  
W. W. Adams ◽  
Galen Lenhert
Keyword(s):  
Tensile Stress ◽  
Nonlinear Elasticity ◽  
Crystal Orientation ◽  
Orientation Distribution ◽  
Structure Change ◽  
Uniform Strain ◽  
Uniform Stress ◽  
X Ray ◽  
Static Tensile ◽  
Static Tensile Stress

ABSTRACTWe have developed a method which uses laser-generated ultrasound to measure the Young's modulus of fibers as a function of temperature and static tensile stress. For fibers of PBZT, measurements have been made to 580°C and 1.7 GPa. The fibers are shown to exhibit nonlinear elasticity which changes systematically with temperature, tensile stress and fiber processing conditions. They exhibit a relaxation associated with a structure change at about 300–400°C.We have also used x-ray diffraction to measure both the crystal modulus and aspects of the ultrastructure such as crystal orientation as a function of static tensile stress, crystal size and unit cell. It is shown that improved crystal orientation with increased tensile stress is one of the most important mechanisms of the nonlinear elasticity. The measurements of orientation distribution are combined with other measurements to make calculations of the crystal modulus for the assumptions of uniform stress and uniform strain. These apparent crystal moduli are considerably greater than the measured ultrasonic ones and both are less than the theoretical values. The assumptions of uniform stress and uniform strain have also been used together with the orientation distribution and other parameters to calculate the macroscopic modulus. Both results exhibit less nonlinear elasticity than that observed experimentally, indicating that there is another mechanism in addition to the crystal reorientation which contributes to the nonlinear elasticity. The x-ray measurements of unit cell as a function of temperature to 450°C show a structure change at about 300-400°C. It is consistant with an oscillation of the phenyl and bisthiazole moities around the connecting single bonds.

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