Electrical methods for verifying internal pressure of vacuum interrupters after long-time service

1993 ◽  
Vol 28 (4) ◽  
pp. 635-641 ◽  
Author(s):  
F.R. Frontzek ◽  
D. Konig ◽  
R. Heinemeyer
Keyword(s):  
Internal Pressure ◽  
Time Service ◽  
Long Time ◽  
Electrical Methods

The Creep of Natural and Snythetic Rubber Compounds in Shear

1941 ◽  
Vol 14 (2) ◽  
pp. 433-443 ◽  
Author(s):  
Stuart H. Hahn ◽  
Ivan Gazdik
Keyword(s):  
Processing Technique ◽  
Creep Tests ◽  
Time Service ◽  
Wide Range ◽  
Recent Developments ◽  
Long Time ◽  
The Many ◽  
Short Time ◽  
Relative Creep ◽  
Rubberlike Materials

Abstract Creep tests, extending in some cases as long as 900 days, indicate that both natural and synthetic rubbers such as Neoprene and butadiene copolymer can be compounded to give satisfactory service in shear mountings. At 140° F, creep is from two to nine times greater than at 80° F, depending on the compound. Tests at room temperature do not indicate either the amount of creep or the life to be expected at higher temperatures. Actual creep (measured in inches) increases with stress, but when expressed at percentage of initial deflection, it may be independent of stress. Creep curves are linear over a considerable range of time when plotted on log-log scales. However, extrapolation of such curves to predict results after very long times is not justified, because the curves may not continue to be linear, or failure of the mountings may occur, particularly at high temperatures. Short time tests of any sort are not necessarily indicative of the relative creep or life of compounds in long-time service. The tests reported here are a small portion of a large number which is being continued and augmented. It is hoped that these and other investigations now under way may contribute to clearing the picture of the complex interrelations between the many physical properties of compounds of rubberlike materials. The rubber technologist uses his specialized knowledge to develop a wide variety of compounds, making use of several types of basic rubberlike materials. He chooses whichever fits service requirements best from performance and economic viewpoints. Modern materials and recent developments in processing technique have made possible compounds suitable for a wide range of service conditions.

scholarly journals Microstructure Evolution and Failure Behavior of Stellite 6 Coating on Steel after Long-Time Service

Coatings ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 532 ◽  
Author(s):  
Jiankun Xiong ◽  
Fuheng Nie ◽  
Haiyan Zhao ◽  
Liangliang Zheng ◽  
Jun Luo ◽  
...  
Keyword(s):  
Fusion Zone ◽  
Microstructure Evolution ◽  
Failure Behavior ◽  
Micro Hardness ◽  
Time Service ◽  
Stellite 6 ◽  
Long Time ◽  
Metallic Compounds ◽  
Hardness Increase ◽  
Stellite Coating

The microstructure evolution, elements diffusion and fracture behavior of the Stellite 6 weld overlay, deposited on 10Cr9Mo1VNbN (F91) steel by the tungsten inert gas (TIG) cladding process, were investigated after long-time service. Obvious diffusion of Fe occurred from the steel and fusion zone to the Stellite overlay, resulting in the microstructure evolution and hardness increase in the coating, where hard Co–Fe phases, σ phases (Fe–Cr metallic compounds) and Cr-rich carbides (Cr18.93Fe4.07C6) were formed. Besides, the width of the light zone, combined with the fusion zone and diffusion zone, increased significantly to a maximum value of 2.5 mm. The fracture of the Stellite coating samples mainly occurred in the light zone, which was caused by the formation and growth of circumferential crack and radial crack under high temperature and pressure conditions. Moreover, the micro-hardness values in the light zone increased to the maximum (470–680 HV) due to the formation and growth of brittle Co–Fe phases. The formation of these cracks might be caused by formed brittle phases and changes of micro-hardness during service.

The Influence of Simulated Service Exposure on the Rupture Strengths of Grade 11, Grade 22, and Type 304 Steels

1974 ◽  
Vol 96 (1) ◽  
pp. 10-21
Author(s):  
D. J. Wilson
Keyword(s):  
High Temperature ◽  
Present Stage ◽  
Time Service ◽  
Type Reaction ◽  
Stage Of Development ◽  
Straight Line ◽  
Long Time ◽  
Service Exposure ◽  
Type 304 ◽  
Grade 11

High temperature exposures were carried out to simulate long-time service. Rupture curves for exposed Grade 11 and Grade 22 steels did not exhibit the instabilities characteristic of the unused materials so that straight-line extrapolation gave good predictions of long-time strengths. Possibly due to a C-type reaction, strength predictions were poorer for Type 304 steel. Similar strengths were obtained using parameter tests of the unused materials. At the present stage of development, simulated service exposures offer an alternative, but not a superior, technique for extrapolating rupture characteristics.

A Comparison of Some Carbon Molybdenum Steels on the Basis of Various Creep Limits

1948 ◽  
Vol 159 (1) ◽  
pp. 165-172 ◽  
Author(s):  
A. E. Johnson ◽  
H. J. Tapsell
Keyword(s):  
Experimental Study ◽  
Experimental Work ◽  
Carbon Steels ◽  
Prolonged Heating ◽  
Time Service ◽  
Long Time ◽  
Engineering Materials ◽  
Short Time ◽  
The Relationship ◽  
Creep Limits

A previous report gave the results of an experimental study of the relationship between short-time and long-time creep limits of a number of carbon steels. Certain conclusions were drawn which it was realized were not necessarily applicable to other types of steel. Similar experimental work has since been carried out on six carbon molybdenum steels, and the results obtained indicate similar limitations in the applicability of short-time creep limits to estimation of design stresses for long-time service, as were disclosed by the prior tests on carbon steels. There is not, at first sight, any reason why short-time and long-time creep limits should correlate, since with most engineering materials metallurgical changes occur during prolonged heating.

Effects of Long-Time Service on the Material of a Steam Boiler Fire Tube

1998 ◽  
Vol 40 (1) ◽  
pp. 43-48 ◽  
Author(s):  
D.T Levcovici ◽  
V Munteanu ◽  
S.M Levcovici ◽  
M Ursu
Keyword(s):  
Steam Boiler ◽  
Time Service ◽  
Long Time

Influence of Service Time on the Microstructure and High Temperature Mechanical Properties of T23 Boiler Tube

2017 ◽  
Vol 898 ◽  
pp. 711-718 ◽  
Author(s):  
Cheng He ◽  
Bao Liang Shi ◽  
Wen Sheng Li ◽  
Jian Ping Zhao ◽  
Kai Xu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Temperature ◽  
Service Time ◽  
Testing Machine ◽  
Tensile Testing Machine ◽  
Time Service ◽  
High Temperature Mechanical Properties ◽  
The Matrix ◽  
Long Time

The influence of long time service on the microstructure and high temperature mechanical properties of T23 steel was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile testing machine. Results showed that lathy bainite ferrite disappears with the increasing service time, both the size and number of the carbides increases, and M23C6 carbides transform into M6C carbides rich in W element. The service process also has a significant influence on the recovery. Sub-grains were found at the grain boundaries with little dislocations in the matrix after 27448 h service time. After running for 27448 h the microstructure degradation of T23 steel is serious. High temperature tensile properties of T23 are closely related to the alloy aging degree. The reasons for the decrease of high temperature mechanical properties after long time service included microstructure degradations such as the increase of both the size and quantity of M23C6 carbides, the transformation of M23C6 to M6C, the desolution of Cr,W,and Mo elements, the decrease of the dislocation density and the occurrence of the sub-grains.

scholarly journals Hard Overlaid Roller and Liner of Coal Pulverizer for Long Time Service.

Materia Japan ◽  
1997 ◽  
Vol 36 (6) ◽  
pp. 619-621 ◽  
Author(s):  
Akira Notomi ◽  
Masaaki Kinoshita ◽  
Yutaka Iida
Keyword(s):  
Time Service ◽  
Long Time

Mechanical Investigation of a Failed Lock-Pin

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
E. Poursaeidi ◽  
A. A. Pirmohammadi ◽  
M. R. Mohammadi Arhani
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Peak Stress ◽  
Element Model ◽  
Gas Turbine Engine ◽  
Time Service ◽  
Turbine Engine ◽  
Turbo Generator ◽  
Long Time ◽  
Mechanical Investigation

This paper presents the outcomes of computational mechanics applied in the root-cause investigation on hot section failure of a 25 MW gas turbo generator in the domestic power plant after 2228 start-stops and 52,586 h operation. The failure includes the complete damage of the first and the second stage of nozzles, blades, seals, shroud segments, and also a peripheral damage on the disk of first stage. Several reported cases from the different power plants with similar events evidenced that the failure is a serious common type in the mentioned gas turbine engine. A previous study on complete metallurgical analysis of disk, moving blades, and lock-pins, was done by Poursaeidi and Mohammadi (2008, “Failure Analysis of Lock-Pin in a Gas Turbine Engine,” Eng. Fail. Anal., 15(7), pp. 847–855), which concluded that the mechanical specification of applied materials had been satisfied. Nevertheless, some problems were found in the fractographic results of lock-pins: the typical fatigue fracture surfaces in the neck of failed lock-pins and frankly localized pitting signs near the head of lock-pin. The lock-pins are kinds of small devices that lock the buckets after inserting them into disk grooves. In this work, a 3D finite element model (FEM) of a blade, a disk, and a lock-pin are made and analyzed by the ANSYS software. The results of the FEM showed a reasonable agreement between the analysis and position of fracture on lock-pins. Also, the results showed that the second vibrational mode of the bucket is a possible cause of failure because in this mode the peak stress occurs on the head of the lock-pin. However, inadequate design and long time service reduced the performance of lock-pins for sustaining a severe hot condition in the first stage of the turbine section.

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