Mechanisms of crack initiation and fracture of the surface of crystals of lithium fluoride and calcite in pulsed thermal loading

1985 ◽  
Vol 17 (3) ◽  
pp. 355-360
Author(s):  
V. M. Finkel' ◽  
N. I. Alyushina
Keyword(s):  
Crack Initiation ◽  
Lithium Fluoride ◽  
Thermal Loading ◽  
Surface Of Crystals

Fatigue Crack Initiation and Growth in Stainless Steel Pipe Welds

2009 ◽  
Author(s):  
D. Green ◽  
R. D. Smith ◽  
J. P. Taggart ◽  
D. Beardsmore ◽  
S. Robinson
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Thermal Loading ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Cyclic Hardening ◽  
Element Model ◽  
Fatigue Tests ◽  
Welded Pipe ◽  
Pipe Work

Thermal fatigue cracks have been found in austenitic pipe work in many pressurised water reactors, caused by thermal cycling due to the passage of water at different temperatures along the pipe inner surface. The rates of crack initiation and growth for this situation are not well understood because of the stochastic nature of the temperature fluctuations. Therefore, large allowances must be made when assessing the integrity of this pipe work to this failure mechanism. Improved assessment of crack initiation and growth could enable increased plant availability, and better safety cases. A programme of work has been completed consisting of fatigue tests on thick 304L butt-welded pipe specimens, and accompanying predictions of crack initiation and growth. In each test, uniform thermal cycles were generated using a water jet on a small area of the pipe. The magnitude of the cycles differed between the tests. Crack initiation and growth were monitored using a dye penetrant technique, applied to the pipe inner and outer surfaces, together with destructive examination. Crack initiation predictions were made using fatigue data derived from mechanical fatigue tests on the same material as in the pipe specimens. Good predictions were made using a strain-life endurance curve at a temperature corresponding to the average temperature of the metal surface during the thermal cycle. Crack growth predictions were based on an inelastic finite-element model accounting for cyclic hardening, and an enhanced R5 procedure (1) with crack closure taken into account. A linear elastic fracture mechanics definition of a Paris law for crack growth was used, and plastic redistribution effects were included. Predictions were good for all of the experimental scenarios carried out. A further experimental and analytical programme is in hand using the same experimental arrangements, concerning variable amplitude thermal loading.

A Study on Fatigue and Creep-Fatigue Life Assessment Using Cyclic Thermal Tests With Mod.9Cr-1Mo Steel Structures

2012 ◽  
Author(s):  
Masanori Ando ◽  
Hiroshi Kanasaki ◽  
Shingo Date ◽  
Koichi Kikuchi ◽  
Kenichiro Satoh ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Temperature Distribution ◽  
Crack Initiation ◽  
Thermal Loading ◽  
Life Assessment ◽  
Estimation Methods ◽  
Short Term ◽  
Cyclic Thermal Loading ◽  
Fatigue Life Assessment ◽  
Creep Fatigue

In a component design at elevated temperature, fatigue and creep-fatigue is one of the most important failure modes, and fatigue and creep-fatigue life assessment in structural discontinuities is important issue to evaluate structural integrity of the components. Therefore, to assess the failure estimation methods, cyclic thermal loading tests with two kinds of cylindrical models with thick part were performed by using an induction heating coil and pressurized cooling air. In the tests, crack initiation and propagation processes at stress concentration area were observed by replica method. Besides those, finite element analysis (FEA) was carried out to estimate the number of cycles to failure. In the first test, a shorter life than predicted based on axisymmetric analysis. Through the 3 dimensional FEA, Vickers hardness test and deformation measurements after the test, it was suggested that inhomogeneous temperature distribution in hoop direction resulted in such precocious failure. Then, the second test was performed after improvement of temperature distribution. As a result, the crack initiation life was in a good agreement with the FEA result by considering the short term compressive holding. Through these test and FEA results, fatigue and creep-fatigue life assessment methods of Mod.9Cr-1Mo steel including evaluation of cyclic thermal loading, short term compressive holding and failure criterion, were discussed. In addition it was pointed out that the temperature condition should be carefully controlled and measured in the structural test with Mod.9Cr-1Mo steel structure.

A stochastic analysis of glass crack initiation under thermal loading

2014 ◽  
Vol 67 (1-2) ◽  
pp. 447-457 ◽  
Author(s):  
Qingsong Wang ◽  
Yu Wang ◽  
Yi Zhang ◽  
Haodong Chen ◽  
Jinhua Sun ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Stochastic Analysis ◽  
Thermal Loading

Prediction of Fatigue Crack Initiation and Growth During Thermal Cycling

2015 ◽  
Author(s):  
Guiyi Wu ◽  
David Smith ◽  
David Tanner
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Crack Initiation ◽  
Thermal Cycling ◽  
Dwell Time ◽  
Thermal Loading ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Stress And Strain ◽  
Finite Element Analyses

Conventional approaches to assess fatigue under combined thermal and mechanical loading often utilize a fatigue design curve. In this paper models based on the physics and mechanics for the initiation and growth of fatigue cracks in stainless steel are first explained. The models are based on experimental evidence gathered for the initiation and growth of small cracks created during strain controlled laboratory tests. This evidence is then linked with data for the growth of large fatigue cracks in stainless steel. In the paper these models are coupled with finite element analyses to explore the fatigue initiation and growth of cracks in stainless steel pipes subjected to thermal cycling. It is assumed that the material behaviour is elastic-perfectly plastic, rate independent and fatigue occurs in air. The stress and strain fields for pipes subjected to a range of thermal loading conditions are explored. The fields are shown to be sensitive to parameters such as the Biot and Fourier numbers that include pipe dimensions, physical properties, dwell time and thermal conditions. Of particular interest is the temperature range and dwell time during thermal loading. Finite element analyses are then used to determine the stress and strain ranges created by thermal loading and these ranges are used in the crack initiation and growth models to estimate fatigue life.

Analysis of railway wheel to study crack initiation due to thermal loading and calculating life cycle

2017 ◽  
Vol 4 (2) ◽  
pp. 2454-2463 ◽  
Author(s):  
Nayan Chandak ◽  
Mayank Yede ◽  
Prashant Malviya ◽  
M.K. Pradhan
Keyword(s):  
Life Cycle ◽  
Crack Initiation ◽  
Thermal Loading ◽  
Railway Wheel

Tests and Numerical Analysis of Cracked Rings Under Thermal Shock in the Brittle/Ductile Transition of a Pressure Vessel Steel

2005 ◽  
Author(s):  
M. Reytier ◽  
S. Chapuliot ◽  
L. Ferry ◽  
M. Ne´de´lec
Keyword(s):  
Crack Initiation ◽  
Fracture Mode ◽  
Pressure Vessel ◽  
Thermal Loading ◽  
Hot Water ◽  
Pressure Vessel Steel ◽  
External Diameter ◽  
Vessel Steel ◽  
Brittle Ductile Transition ◽  
Thermal Shocks

Thermal shocks and temperature gradients associated with large thickness constitute difficult loadings for structures integrity analysis. Moreover, at low temperature or because of irradiation effects, the pressure vessel steel 16MND5 undergoes a transition in fracture mode which may lead to cleavage initiation. The prevention of this fracture mode is generally ensured by first staying outside the brittle domain and secondly, by imposing a stress intensity factor below the fracture toughness which is determined from monotonic and isotherm standard tests. But, with various temperature-loading histories, this criterion is not faultless. Therefore, in order to study in detail rupture under thermal shocks, with several loading types (mechanical and/or thermal loadings), a specific-adapted cracked ring has been developed. It consists of a 50mm thick ring which has a crack on the external diameter and several holes through the specimen to locally heat the ring by injecting hot water which can lead to crack initiation. This particular test allows the study of crack initiation with only thermal loading or both thermal loading and external mechanical loading. This article describes in details several tests including one with cleavage rupture. Moreover, numerical calculations are presented to estimate the mechanical fields at the crack tip and the global fracture mechanics parameters as a function of the temperature. Several rupture criteria are then applied to predict the initiation.

Low Cycle Fatigue Analysis of after Treatment Device Induced due to Thermal Load by Using Finite Element Analysis

2014 ◽  
Vol 592-594 ◽  
pp. 1104-1108 ◽  
Author(s):  
Swapnil Vitthal Kumbhar ◽  
Vilas Kulkarni ◽  
R.M. Tayade
Keyword(s):  
Crack Initiation ◽  
Thermal Fatigue ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Analysis ◽  
Von Mises Stress ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Von Mises

Cyclic thermal loading causes cyclic thermal stress and thermal fatigue in the component. The goal of this paper is to characterize the thermal fatigue behavior of after-treatment (AT) device, i.e. Exhaust Gas Processor (EGP) and prediction of crack initiation cycles. The paper contains transient thermal analysis to map temperature on EGP model. By taking temperature distribution as input, Elasto-plastic structural analysis is done. Based on stress-strain data and fatigue material property, crack initiation cycles are estimated. For low cycle fatigue analysis, strain based approach, i.e. Brown-Miller Criteria with Morrow mean stress correction factor [1] is used. The von-Mises stress and crack initiation cycles are investigated and S-N curve and Ɛ-N curve are compared with standard graphs.

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