Influence of Testing Environment on SP Creep Rupture Lives

2013 ◽  
Author(s):  
Ken-ichi Kobayashi ◽  
Sho Takei
Keyword(s):  
Oxide Scale ◽  
Residual Life ◽  
Rupture Life ◽  
High Vacuum ◽  
Creep Rupture ◽  
Test Duration ◽  
Destructive Testing ◽  
Creep Tests ◽  
Testing Environment ◽  
High Temperature Components

Small Punch (SP) Creep test has been recognized as a semi destructive testing method to examine residual life of creep in high temperature components. Employing 2.25Cr-1Mo steel (SCMV4), SP creep tests were conducted at 600°C both in air and in high vacuum to examine the influence of oxidation on the long-term rupture life of the SP creep tests. As a test result, the creep rupture life in air was shorter than that in vacuum when the rupture life was less than 1000 hours. Reduction of rupture lives in air was approximately a half of them tested in vacuum. However when the creep rupture life was longer than 1000 hours, little difference emerged even if the testing atmosphere was different. A thickness of the oxide scale formed on SP creep specimens in air increased with the test duration. The experimental test results showed that the oxide scale affected on a coefficient of friction between the loading ball and the SP creep specimen. Furthermore the oxide scale formed in air did not always peel off from the test specimen, and the thick oxide scale endured a part of applied load in the longer life test.

Influence of Testing Environment and Radius of Die Shoulder on SP Creep Rupture Life

2011 ◽  
Author(s):  
Ken-ichi Kobayashi ◽  
Masahiro Kaneko ◽  
Hideo Koyama ◽  
Gavin C. Stratford ◽  
Masaaki Tabuchi
Keyword(s):  
Oxide Scale ◽  
Rupture Life ◽  
High Vacuum ◽  
Creep Rupture ◽  
Test Duration ◽  
Creep Life ◽  
Destructive Testing ◽  
Creep Tests ◽  
Testing Environment ◽  
High Temperature Components

Small Punch, hereinafter designated as SP, creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. Employing low alloy steel, a series of SP creep tests were conducted on disc specimens at 600°C in air and in high vacuum to investigate the influence of oxide scale on the creep rupture life. Thickness of the oxide scale on disc specimens in air increased with the test duration, e.g., about 30μm in thickness after 400 hours. The creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the disc thickness. In addition, the magnitude of radius of a lower die shoulder affected the SP creep rupture life. The influence of this radius on the SP creep life was also studied experimentally and numerically. The creep rupture life with the die radius of 0.5mm had twice longer than that with 0.6mm. This fact was also demonstrated by the FE analysis.

PS44 Effect of Oxide Scale in Small Punch Creep Specimen on Creep Rupture Life

2010 ◽  
Vol 2010 (0) ◽  
pp. 143-145
Author(s):  
Masahiro KANEKO ◽  
Ken-ichi KOBAYASHI ◽  
Hideo KOYAMA
Keyword(s):  
Oxide Scale ◽  
Rupture Life ◽  
Creep Rupture ◽  
Small Punch ◽  
Creep Specimen

Study of Creep Strength for P91 Steels after Short Term Overheating above Ac3 Temperature

2013 ◽  
Vol 393 ◽  
pp. 94-101
Author(s):  
Ng Guat Peng ◽  
Badrol Ahmad ◽  
Mohd Razali Muhamad ◽  
M. Ahadlin
Keyword(s):  
High Temperature ◽  
Creep Strength ◽  
Rupture Strength ◽  
Rupture Life ◽  
Creep Rupture ◽  
Tempered Martensite ◽  
Short Term ◽  
Creep Tests ◽  
Rupture Stress ◽  
Limited Creep

Advanced ferritic steels containing 9 wt% Cr are widely used in the construction of supercritical and ultra supercritical boiler components. The microstructure of the as supplied 91 materials consists of a tempered martensite matrix, a fine dispersion of intergranular chromium rich M23C6 precipitates and intragranular carbonitrides MX particles rich in V and Nb. This steel requires post weld heat treatment (PWHT) to produce a tempered microstructure after welding to develop excellent creep strength for high temperature service. Based on past experience, situations may arise whereby the components are subjected to an accidental overshoot in temperature during PWHT. The short excursion to high temperature beyond Ac3 would have resulted in the formation of deleterious phases, for example, soft α-ferrite which has poor creep strength and hard martensite which has a low toughness. In this study, the degraded specimens with soft α ferrite as a result of cooling transformation from 900°C are proven to have a limited creep rupture life where the creep rupture strength dropped remarkably after 1000 hours. As the peak temperature increased to 950°C and 1000°C, hard and brittle martensite was formed on cooling. The creep specimens were found to exhibit better creep strength; most probably the creep behavior was improved by the tempering effect at 600°C during creep tests. Nevertheless, despite the tempering which might have improved the toughness slightly, the high temperature creep rupture stress still had dropped approximately 40%, as compared to the virgin alloys in the range of rupture time from 1,000 hours to 10,000 hours.

Tensile Creep and Creep Rupture of Continuous Strand Mat Polypropylene Composites

1995 ◽  
Vol 29 (16) ◽  
pp. 2215-2227 ◽  
Author(s):  
R. E. Little ◽  
W. J. Mitchell ◽  
P. K. Mallick
Keyword(s):  
Response Time ◽  
Creep Rupture ◽  
Tensile Creep ◽  
Test Duration ◽  
Secondary Creep ◽  
Creep Tests ◽  
Polypropylene Composites ◽  
Straight Line ◽  
Stress Levels ◽  
The Relationship

This paper describes an experimental study on the tensile creep behavior of a random continuous fiber mat reinforced polypropylene composite, commercially known as Azdel. A special experimental setup was designed and used to conduct these creep tests at 75 and 100°C with stress levels ranging from 30 to 60 percent of the tensile strength of Azdel. The test duration was 3,000 hours or the time to creep rupture response, whichever occurred first. A straight line on a semi-log plot adequately described the relationship between the imposed stress and the creep rupture response time for the range of stress levels studied. Moreover, the estimated secondary creep rate was inversely related to the observed creep rupture response time.

scholarly journals The Influence of Both Testing Environment and Fillet Radius of the Die Holder on the Rupture Life of Small Punch Creep Tests

2012 ◽  
Vol 6 (8) ◽  
pp. 925-934 ◽  
Author(s):  
Ken-ichi KOBAYASHI ◽  
Masahiro KANEKO ◽  
Hideo KOYAMA ◽  
Gavin C. STRATFORD ◽  
Masaaki TABUCHI
Keyword(s):  
Rupture Life ◽  
Creep Tests ◽  
Small Punch ◽  
Testing Environment ◽  
Fillet Radius

Microstructure Evolution and Creep Rupture Behavior of Modified 9Cr-1Mo Steel Welded Joint

2020 ◽  
Author(s):  
Facai Ren ◽  
Xiaoying Tang ◽  
Jinsha Xu ◽  
Jun Si ◽  
Yiwen Yuan
Keyword(s):  
Electron Microscope ◽  
Microstructure Evolution ◽  
Welded Joint ◽  
Rupture Life ◽  
Optical Microscope ◽  
Creep Rupture ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Before And After ◽  
Rupture Behavior

Abstract Microstructure evolution and creep rupture behavior of modified 9Cr-1Mo steel welded joint used for steam cooler in high pressure heater system were systematically studied in this paper. Creep tests were carried out using uniaxial creep specimens machined from the normalized and tempered plate at 818K and 838K with the stresses ranging from 150 to 225MPa. The curve of stress vs. rupture time was achieved to evaluate the creep rupture life of modified 9Cr-1Mo steel welded joint. The creep data were analyzed in terms of Norton’s power law, Monkman-Grant relation and modified Monkman-Grant relation. Microstructure before and after creep exposure were analyzed by optical microscope, scanning electron microscope and transmission electron microscope, to further explain the rupture mechanisms of modified 9Cr-1Mo steel welded joint.

Study on Creep Behaviors of T92 Steel under Multiaxial Stress State

2013 ◽  
Vol 860-863 ◽  
pp. 774-779
Author(s):  
Xue Ping Mao ◽  
Yang Yu ◽  
Chao Li ◽  
Sai Dong Huang ◽  
Hong Xu ◽  
...  
Keyword(s):  
Stress State ◽  
Rupture Life ◽  
Creep Damage ◽  
Creep Rupture ◽  
Failure Behavior ◽  
Multiaxial Stress ◽  
Creep Tests ◽  
Creep Ductility ◽  
Notched Specimen ◽  
Multiaxial Stress State

Creep tests for smooth specimens and notched specimens of T92 steel were carried out to study the effect of multiaxial stress state on creep rupture behaviors at 650°C. Creep rupture life was estimated by representative stress at multiaxial state of stress, the failure behavior of multiaxial creep was analyzed, and Kachanov creep damage formula was used to analyze the experimental data. The results show that the notch strengthens rupture life, multiaxial rupture behavior is controlled by mixed parameters, the creep ductility of the smooth and notched specimen decreases with rupture time, and damage factors of the smooth specimen and notched specimen are similar according to Kachanov formula.

scholarly journals GS14 Effect on Creep Rupture Life in Miniature Creep Tests

2014 ◽  
Vol 2014 (0) ◽  
pp. _GS14-1_-_GS14-2_
Author(s):  
Takeshi KAWASHIMA ◽  
Ken-ichi KOBAYASHI ◽  
Hideo KOYAMA
Keyword(s):  
Rupture Life ◽  
Creep Rupture ◽  
Creep Tests
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