scholarly journals Fracture Failure Analysis of the Connecting Bolt of Circuit Breaker in 500kV Converter Station

2021 ◽  
Vol 2076 (1) ◽  
pp. 012099
Author(s):  
Jun Wang ◽  
Xianhui Cao ◽  
Rong Huang ◽  
Yujing Hu ◽  
Weike Liu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Energy Spectrum ◽  
Low Cycle Fatigue ◽  
Circuit Breaker ◽  
High Stress ◽  
Metallographic Analysis ◽  
Cycle Fatigue ◽  
Safe Operation ◽  
Fracture Failure ◽  
Scanning Electron

Abstract Through a macroscopic inspection, a stereomicroscopic inspection, a material analysis, a hardness inspection, a metallographic analysis, scanning electron microscope and energy spectrum analysis, the reasons for the breakage of the connecting bolts of the circuit breaker in a 500kV converter station are studied. The results show that the bolt fracture is caused by the combined effect of a hydrogen embrittlement and a high-stress low-cycle fatigue. The corresponding recommended measures are proposed to improve the reliability of the bolts and ensure the safe operation of the circuit breaker.

Cracking Failure Analysis of Cr12MoV Steel Guide Roller

2014 ◽  
Vol 1033-1034 ◽  
pp. 818-823
Author(s):  
Yuan Li ◽  
Gang Yang ◽  
Yi Yang ◽  
Yi Chen ◽  
Shu Lin Huang
Keyword(s):  
Electron Microscope ◽  
Energy Spectrum ◽  
Scanning Electron Microscope ◽  
Failure Analysis ◽  
Hardness Test ◽  
Metallographic Analysis ◽  
Casting Defects ◽  
Guide Roller ◽  
Macroscopic Observation ◽  
Scanning Electron

A failure case of the Cr12MoV steel guide roller is presented in this paper. Many net cracks were distributed on the surface and both ends of guide roller had been oxidized to black seriously. The failure analysis was performed in terms of macroscopic observation, fracture scanning electron microscope (SEM), energy spectrum, metallographic analysis and hardness test, etc. The results show that a large number of casting defects, such as holes and inclusions, exist inside of the guide roller, which could be considered as crack source under the effect of alternating load; and then the crack source constantly grows and expands along the vulnerable region-grain boundary when the guide roller bears cold and hot effects repeatedly, resulting in large stress existing on the surface; finally fatigue intergranular cracks are formed which lead to guide roller cracking failure.

Low-Cycle Fatigue Behaviour of Gas Turbine Alloys

1974 ◽  
Vol 188 (1) ◽  
pp. 321-328 ◽  
Author(s):  
W. J. Evans ◽  
G. P. Tilly
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
High Stress ◽  
Cyclic Creep ◽  
Fatigue Curve ◽  
Fatigue Behaviour ◽  
Material Surface ◽  
Tension Stress ◽  
Cycle Fatigue ◽  
Stress Tests

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 103 and 104 cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions. Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

A Revisit of Material and Structural Failures

2015 ◽  
Author(s):  
Sheldon Wang
Keyword(s):  
Low Cycle Fatigue ◽  
High Stress ◽  
Engineering Practice ◽  
Material Failure ◽  
Cycle Fatigue ◽  
Structural Failure ◽  
Column Buckling ◽  
Typical Material ◽  
Structural Failures ◽  
To Come

In this paper, we revisit the issues related to material and structural failures. In particular, we employ a similar bridging function between the typical structural failure, the so-called column buckling, and the typical material failure under compression, to link the low stress high cycle and the high stress low cycle fatigue. A part of the intention of this paper is to come up with simple formulas as guidelines in engineering practice for both material and structural failures in both static and dynamic situations.

Using CFRP to Repair the Steel Pipe with Fatigue Cracks

2010 ◽  
Vol 146-147 ◽  
pp. 1086-1089 ◽  
Author(s):  
Hong Tao Zhang ◽  
Xiao Xiang Xue ◽  
Yan Zheng ◽  
Peng Feng
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fiber Reinforced Polymer ◽  
Steel Pipe ◽  
Carbon Fiber Reinforced Polymer ◽  
Cycle Fatigue ◽  
Safe Operation ◽  
Reinforced Polymer ◽  
Pressure Pipeline ◽  
Crack Defect

This paper provides a new method to repair the steel pipe with fatigue cracks by using carbon fiber reinforced polymer (CFRP). Cracks may arise in Pressure pipeline in service because of low cycle fatigue. Crack defect is the biggest problem, because crack will gradually propagate and seriously threaten the safe operation of pipeline. This paper provides a repair and calculation method for pressure pipeline with fatigue cracks, and some specific engineering cases are given based on this method.

Shear Strength of a Thermal Barrier Coating Parallel to the Bond Coat

1998 ◽  
Vol 120 (1) ◽  
pp. 26-32 ◽  
Author(s):  
T. A. Cruse ◽  
R. C. Dommarco ◽  
P. C. Basti´as
Keyword(s):  
Shear Strength ◽  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Low Cycle Fatigue ◽  
High Stress ◽  
Test Method ◽  
Thermal Barrier ◽  
Cycle Fatigue ◽  
Air Plasma ◽  
Barrier Coating

The static and low cycle fatigue strength of an air plasma sprayed (APS) partially stabilized zirconia thermal barrier coating (TBC) is experimentally evaluated. The shear testing utilized the Iosipescu shear test arrangement. Testing was performed parallel to the TBC-substrate interface. The TBC testing required an innovative use of steel extensions with the TBC bonded between the steel extensions to form the standard losipescu specimen shape. The test method appears to have been successful. Fracture of the TBC was initiated in shear, although unconstrained specimen fractures propagated at the TBC-bond coat interface. The use of side grooves on the TBC was successful in keeping the failure in the gage section and did not appear to affect the shear strength values that were measured. Low cycle fatigue failures were obtained at high stress levels approaching the ultimate strength of the TBC. The static and fatigue strengths do not appear to be markedly different from tensile properties for comparable TBC material.

scholarly journals The Effect of Long Term Service at Elevated Temperatures on Microstructure Degradation of Austenitic Reformer Tubes

2018 ◽  
Vol 18 (2) ◽  
pp. 27-36
Author(s):  
J. Łabanowski ◽  
M. Jurkowski ◽  
M. Landowski
Keyword(s):  
Electron Microscope ◽  
Elevated Temperatures ◽  
Cast Steel ◽  
Metallographic Analysis ◽  
Degradation Ratio ◽  
Inner Diameter ◽  
Reformer Tubes ◽  
The Relationship ◽  
Scanning Electron

AbstractThe paper analyses the relationship between an increase of the inner diameter of tubes made of Manaurite XM cast steel and transformations occurring in their microstructure due to long-lasting operation in methane reformer. Examinations included metallographic analysis with light microscope (LM), scanning electron microscope (SEM) and microanalysis of the chemical composition of precipitates (EDX). It was indicated that there is a relationship between the microstructure degradation ratio, morphology of the precipitates and an increase of the inner diameter of the tubes.

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