Expert fractographic evaluation of the crack growth time and the level of nominal stresses in fatigue

1989 ◽  
Vol 24 (6) ◽  
pp. 639-643
Author(s):  
V. A. Stepanenko
Keyword(s):  
Crack Growth ◽  
Growth Time ◽  
Crack Growth Time

PWSCC Crack Growth Modeling Approaches

2011 ◽  
Author(s):  
F. W. Brust ◽  
D.-J. Shim ◽  
G. Wilkowski ◽  
D. Rudland
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Residual Stresses ◽  
Crack Growth ◽  
Corrosion Cracking ◽  
Growth Time ◽  
Pressurized Water ◽  
Primary Water ◽  
Water Reactors

Flaw indications have been found in some dissimilar metal (DM) nozzle to stainless steel piping welds and reactor pressure vessel heads (RPVH) in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe) using Alloy 182/82 weld metal. The welds may become susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. The weld residual stresses (WRS) induced by the welds are a main driver of PWSCC. Several mechanical mitigation methods to control PWSCC have been developed for use on a nozzle welds in nuclear PWR plants. These methods consist of applying a weld overlay repair (WOR), using a method called mechanical stress improvement process (MSIP), and applying an inlay to the nozzle ID. The purpose of a mitigation method is to reduce the probability that PWSCC will occur in the nozzle joint. The key to assessing the effectiveness of mitigation is to determine the crack growth time to leak with and without the mitigation. Indeed, for WOR and MSIP, the weld residual stresses are often reduced after application while for inlay they are actually increased. However, all approaches reduce crack growth rates if applied properly. Procedures for modeling PWSCC growth tend to vary between organizations performing the analyses. Currently, the prediction of PWSCC crack growth is based on the stress intensity factors at the crack tips. Several methods for evaluating the stress intensity factor for modeling the crack growth through these WRS fields are possible, including using analytical, natural crack growth using finite element methods, and using the finite element alternating method. This paper will summarize the methods used, critique the procedures, and provide some examples for crack growth with and without mitigation. Suggestions for modeling such growth will be provided.

scholarly journals Residual life assessment of welded joints in the girth weld root

2020 ◽  
Vol 315 ◽  
pp. 12001
Author(s):  
Leonid Shron ◽  
Vladimir Bogutsky ◽  
Elmar Yagyaev ◽  
Illa Tabolin
Keyword(s):  
Crack Growth ◽  
Welded Joints ◽  
Residual Life ◽  
Critical Length ◽  
Initial Crack ◽  
Calculation Model ◽  
Life Assessment ◽  
Internal Crack ◽  
Growth Time ◽  
Weld Root

The article analyzes the influence of the structural crack-like defect in the girth weld root welding the bottom to the collector body on the crack growth resistance. A mathematical model has been developed to estimate the residual life resource of welded joints with an internal crack-like defect in the root of the weld under creep. Results of metallographic studies of bench tests results for the welded joints long-term strength formed the basis of the calculation model. In all tested models the cracks start at the top of the narrow structural gap in the weld root and develop along almost the entire weld axis, perpendicular to the wall of the pipe and have a discrete growth pattern. As a result, discrete rupture of material occurs on a length of rc, and the initial crack is incremented by this length. After that, a “plastic core” of rc length is formed in the newly formed crack tip, additional damage is accumulated, and the crack development process continues until the stress level in the section weakened by the crack reaches a critical value. The obtained dependence characterizes the crack growth time from the initial crack-like defect to its critical length.

Cloud Applications Performance in Crack Growth Simulations of Pre-Hydrogenated Structure Components

2016 ◽  
Vol 844 ◽  
pp. 97-102
Author(s):  
Daniel L. Kishlakov ◽  
Pavel V. Tarakanov ◽  
Georgy V. Shashurin ◽  
Yury V. Berchun
Keyword(s):  
Crack Growth ◽  
Batch Processing ◽  
Growth Time ◽  
Efficiency Criterion ◽  
Durability Analysis ◽  
Fracture Crack ◽  
Efficiency Estimation ◽  
Type Calculation ◽  
Loaded Structure ◽  
Computational Resources

The design of durable structure components requires durability analysis in CAE systems and cloud computations use is favorable for batch processing of multiple same-type calculation routines. To develop CAE durability modules analytical approach to different batch processing systems efficiency estimation is necessary. Such modules are intended for durability analysis of pre-hydrogenated and statically loaded structure components with initial defects. Durability estimate is defined as crack growth time elapsed from initial defect state to structure component fracture. Crack kinetics model had been used to simulate a fracture process, required for safe operation of a structure; crack length curves had been obtained and analyzed. The results were verified with the published experimental data on the subject at hand.The authors’ efficiency criterion was applied for performance analysis of the developed cloud application to find a subset of one modelling parameter in which the application is efficient being constrained in number of computational resources available and in the desirable level of performance.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

A discrete dislocation analysis of fatigue crack growth

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-69-Pr5-75
Author(s):  
V. S. Deshpande ◽  
H. H.M. Cleveringa ◽  
E. Van der Giessen ◽  
A. Needleman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Discrete Dislocation

Use of cold tolerant eucalyptus species as a partial replacement for southern mixed hardwoods

TAPPI Journal ◽  
2012 ◽  
Vol 11 (7) ◽  
pp. 29-35 ◽  
Author(s):  
PETER W. HART ◽  
DALE E. NUTTER
Keyword(s):  
Potential Method ◽  
The United States ◽  
Partial Replacement ◽  
Growth Time ◽  
Eucalyptus Species ◽  
Cold Tolerant ◽  
Hardwood Pulp ◽  
Time Required ◽  
The Cost ◽  
Operational Data

During the last several years, the increasing cost and decreasing availability of mixed southern hardwoods have resulted in financial and production difficulties for southern U.S. mills that use a significant percentage of hardwood kraft pulp. Traditionally, in the United States, hardwoods are not plantation grown because of the growth time required to produce a quality tree suitable for pulping. One potential method of mitigating the cost and supply issues associated with the use of native hardwoods is to grow eucalyptus in plantations for the sole purpose of producing hardwood pulp. However, most of the eucalyptus species used in pulping elsewhere in the world are not capable of surviving in the southern U.S. climate. This study examines the potential of seven different cold-tolerant eucalyptus species to be used as replacements for, or supplements to, mixed southern hardwoods. The laboratory pulping and bleaching aspects of these seven species are discussed, along with pertinent mill operational data. Selected mill trial data also are reviewed.

Progressive Debonding of Multilayer Interconnect Structures

1997 ◽  
Vol 473 ◽  
Author(s):  
Michael Lane ◽  
Robert Ware ◽  
Steven Voss ◽  
Qing Ma ◽  
Harry Fujimoto ◽  
...  
Keyword(s):  
Thin Films ◽  
Crack Growth ◽  
Driving Force ◽  
Adhesion Energy ◽  
Time Dependent ◽  
Multilayer Thin Films ◽  
Processing Conditions ◽  
Interface Morphology ◽  
Entire Sample ◽  
Crack Growth Velocity

ABSTRACTProgressive (or time dependent) debonding of interfaces poses serious problems in interconnect structures involving multilayer thin films stacks. The existence of such subcriticai debonding associated with environmentally assisted crack-growth processes is examined for a TiN/SiO2 interface commonly encountered in interconnect structures. The rate of debond extension is found to be sensitive to the mechanical driving force as well as the interface morphology, chemistry, and yielding of adjacent ductile layers. In order to investigate the effect of interconnect structure, particularly the effect of an adjacent ductile Al-Cu layer, on subcriticai debonding along the TiN/SiO2 interface, a set of samples was prepared with Al-Cu layer thicknesses varying from 0.2–4.0 μm. All other processing conditions remained the same over the entire sample run. Results showed that for a given crack growth velocity, the debond driving force scaled with Al-Cu layer thickness. Normalizing the data by the critical adhesion energy allowed a universal subcriticai debond rate curve to be derived.

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