Fracture Mechanics of Creep Crack Growth in Metallic Materials

1981 ◽  
pp. 253-262
Author(s):  
Kiyotsugu Ohji ◽  
Keiji Ogura ◽  
Shiro Kubo ◽  
Yasuyuki Katada
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Metallic Materials ◽  
Creep Crack

Assessment of Power Plant Components With Flaws and Defects Operating in the Long-Term Creep Range

2019 ◽  
Author(s):  
Magdalena Speicher ◽  
Thorben Bender ◽  
Andreas Klenk ◽  
Falk Mueller ◽  
Christian Kontermann ◽  
...  
Keyword(s):  
High Temperature ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Material Behavior ◽  
Critical Crack Length ◽  
Creep Crack ◽  
Combining Data ◽  
Crack Problems

Abstract Originating from defects and flaws in high temperature components crack initiation and crack propagation under service conditions can occur. Fracture mechanics data and procedures are needed to study crack problems and to support an advanced remnant life evaluation. During subsequent research in the past 35 years, data were determined for different high temperature materials. Methodologies and concepts taking into account the specific material behavior were developed in order to be able to describe crack initiation and crack growth and have appropriate assessment methods available. For creep crack initiation two criteria principles were used and for creep crack growth assessment based on the integral C* parameter were applied. Furthermore, a method for determination of critical crack length was developed allowing decisions whether modified stress analysis methods are sufficient or more complicated fracture mechanics methods are needed. To provide data and methodologies in a user-friendly way, a program system combining data and methods was implemented. The paper describes developed features and shows comparisons to other methods. The methods can be applied for design purposes as well as remnant life assessments.

Comparison Between Crack Growth in Fracture Mechanics Specimens and Feature Component Tests Carried Out in a Low-Alloy Steel

1999 ◽  
Vol 122 (1) ◽  
pp. 40-44 ◽  
Author(s):  
Kamran Nikbin
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Growth Data ◽  
Good Correspondence ◽  
Creep Crack ◽  
Growth Properties ◽  
Circumferential Defects ◽  
Testing Condition

In both power generation plants and the chemical industries, there is a need to assess the significance of defects which may exist in high-temperature equipment operating in the creep range. This paper examines the methods of analysis used in laboratory creep crack growth data and their relevance to crack growth data derived from feature component tests which best simulate actual components under controlled testing condition. The material examined was a 214 Cr 1 Mo steel in the new condition at 550 and 600°C. The creep crack growth properties were determined on compact tension specimens. The data were compared with representative crack growth data from feature test components. These consisted of cracked rings, thick-walled cylinders, and thin-walled tubes containing axial or circumferential defects under combinations of axial and internal pressure loading. Little influence of size or temperature on the measured crack propagation rates was observed when the results were plotted against the creep fracture mechanics parameter C*. This is shown to be because the relevant condition had little effect on the appropriate crack tip creep ductilities of the material. Good correspondence was observed between the compact tension and the feature component tests, suggesting the feasibility of the C* method for predicting short-term laboratory tests using different geometries. [S0094-9930(00)01001-5]

A Sensitivity Study of Creep Crack Growth in Pipes

2002 ◽  
Author(s):  
K. Wasmer ◽  
K. M. Nikbin ◽  
G. A. Webster
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Sensitivity Study ◽  
Pressure Vessels ◽  
Materials Properties ◽  
Creep Crack ◽  
Piping Systems ◽  
Mechanics Concepts ◽  
Assessment Procedures

Failure of pressure vessels and piping systems that operate at high temperatures can occur by net section rupture, creep crack growth or a combination of both processes. Several design and assessment procedures are available for dealing with this situation. These include the ASME Pressure Vessel and Piping, French RCC-MR (Appendix 16) and British R5 and BS7910 codes. Each of these procedures uses a combination of continuum mechanics and fracture mechanics concepts to make an assessment. Although the procedures adopt the same basic principles, often different formulae are employed to make an assessment. The main parameters that are used are reference stress, σref, stress intensity factor, K, and the creep fracture mechanics term C*. In this paper, an analysis is performed to estimate the sensitivity of the predictions of creep crack growth in a pressurised pipe to the choice of formulae used and materials properties employed. It is shown that most sensitivity is obtained to choice of expression employed for calculating σref and to whether batch specific or more generic materials properties data are selected.

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