Indentation Fracture Studies of a BaTiO3 Thin Film on a Silicon Substrate

1995 ◽  
Vol 403 ◽  
Author(s):  
Wai-Ming Ho ◽  
Ran Fu ◽  
Kai-Tak Wan ◽  
Ji Chou ◽  
Tong-Yi Zhang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Silicon Substrate ◽  
Square Root ◽  
Indentation Fracture ◽  
Batio3 Thin Film

AbstractIt has been experimentally and theoretically found that the critical applied stress intensity factor for indentation cracking also depends linearly on the reciprocal of the square root of crack length when the indentation fracture technique is used to measure residual stresses in thin films.

Slow Crack Growth in Glasses and Ceramics Under Residual and Applied Stresses

1989 ◽  
Vol 111 (1) ◽  
pp. 61-67 ◽  
Author(s):  
F. Erdogan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Crack Growth ◽  
Slow Crack Growth ◽  
Threshold Value ◽  
Crack Arrest ◽  
Growing Crack ◽  
Applied Stresses

The problem of slow crack growth under residual stresses and externally applied loads in plates is considered. Even though the technique developed to treat the problem is quite general, in the solution given it is assumed that the plate contains a surface crack and the residual stresses are compressive near and at the surfaces and tensile in the interior. The crack would start growing subcritically when the stress intensity factor exceeds a threshold value. Initially the crack faces near the plate surface would remain closed. A crack-contact problem would, therefore, have to be solved to calculate the stress intensity factor. Depending on the relative magnitudes of the residual and applied stresses and the threshold and critical stress intensity factors, the subcritically growing crack would either be arrested or become unstable. The problem is solved and examples showing the time to crack arrest or failure are discussed.

Analysis of Residual Stresses and Assessment of Postulated Cracks in a Core Shroud Weld

2002 ◽  
Author(s):  
Igor Varfolomeyev ◽  
Dieter Siegele ◽  
Dieter Beukelmann
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Crack Depth ◽  
Numerical Procedure ◽  
Welding Process ◽  
Material Model ◽  
Finite Element Program ◽  
Core Shroud

In order to assess postulated cracks in weldments of a BWR core shroud residual stresses are calculated by simulating the welding process. In the numerical analysis, weld metal deposition and the sequence of weld passes follow the manufacture protocol. The calculations are performed using the finite element program ABAQUS and a material model with kinematic nonlinear hardening. Calculations of the crack driving parameter, the stress intensity factor, are carried out for postulated circumferential cracks using a numerical procedure, as well as by applying a weight function solution specially developed for cracks in a thin-walled cylinder. The results give rise to a discussion on the validity of linear elastic fracture mechanics for assessing defects in weldments. Additionally, for a complete circumferential crack the trend in the stress intensity factor is studied when the crack depth approaches the full wall thickness.

Probing the Critical Stress Intensity Factor for Slip Transfer across Grain Boundaries by Subgranular Indentation Alfonso

2000 ◽  
Vol 649 ◽  
Author(s):  
H.W. Ngan ◽  
Y.L. Chiu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Critical Stress ◽  
Critical Stress Intensity Factor ◽  
Square Root ◽  
Slip Transfer ◽  
Macroscopic Deformation

ABSTRACTBy analysing the relevant results in the literature, we have found that, when indentation is made on a subgranular level, the hardness varies roughly inversely with the square root of the distance between the indent and the grain boundary. This effect is analogous to the Hall-Petch effect for macroscopic deformation.

Modelling shattered rim cracking in railroad wheels

2011 ◽  
Vol 225 (6) ◽  
pp. 593-604
Author(s):  
V Sura ◽  
S Mahadevan
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress State ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Equivalent Stress ◽  
Crack Tip ◽  
Residual Stress State

Shattered rim cracking, propagation of a subsurface crack parallel to the tread surface, is one of the dominant railroad wheel failure types observed in North America. This crack initiation and propagation life depends on several factors, such as wheel rim thickness, wheel load, residual stresses in the rim, and the size and location of material defects in the rim. This article investigates the effect of the above-mentioned parameters on shattered rim cracking, using finite element analysis and fracture mechanics. This cracking is modelled using a three-dimensional, multiresolution, elastic–plastic finite element model of a railroad wheel. Material defects are modelled as mathematically sharp cracks. Rolling contact loading is simulated by applying the wheel load on the tread surface over a Hertzian contact area. The equivalent stress intensity factor ranges at the subsurface crack tips are estimated using uni-modal stress intensity factors obtained from the finite element analysis and a mixed-mode crack growth model. The residual stress and wheel wear effects are also included in modelling shattered rim cracking. The analysis results show that the sensitive depth below the tread surface for shattered rim cracking ranges from 19.05 to 22.23 mm, which is in good agreement with field observations. The relationship of the equivalent stress intensity factor (Δ K eq) at the crack tip to the load magnitude is observed to be approximately linear. The analysis results show that the equivalent stress intensity factor (Δ K eq) at the crack tip depends significantly on the residual stress state in the wheel. Consideration of as-manufactured residual stresses decreases the Δ K eq at the crack tip by about 40 per cent compared to that of no residual stress state, whereas consideration of service-induced residual stresses increases the Δ K eq at the crack tip by about 50 per cent compared to that of as-manufactured residual stress state. In summary, the methodology developed in this article can help to predict whether a shattered rim crack will propagate for a given set of parameters, such as load magnitude, rim thickness, crack size, crack location, and residual stress state.

Displacement Controlled Stress Intensity Factor Solutions for Structural Integrity Assessments of Welding Residual Stress Distributions

2008 ◽  
Author(s):  
Adam Toft ◽  
David Beardsmore ◽  
Colin Madew ◽  
Huego Teng ◽  
Mark Jackson
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Weight Function ◽  
Driving Force ◽  
Welding Residual Stress ◽  
Crack Plane ◽  
Crack Driving Force

Within the UK nuclear industry the assessment of fracture in pressurised components is often carried out using procedures to calculate the margin of safety between a lower-bound fracture toughness and the crack driving force. Determination of the crack driving force usually requires the calculation of elastic stress intensity factor solutions for primary loads and secondary loads arising from weld residual stresses and/or thermal stresses. Within established UK assessment procedures weight function solutions are available which allow the stress intensity factors to be calculated from the through-wall opening-mode stress distribution in an uncracked component. These weight-function solutions are generally based on models where either no boundary condition is applied, or where one is applied at a distance either side of the crack plane that is very long compared with the crack size and wall thickness. Such solutions do not take into account any reduction in the stress field that might occur as the distance from the crack faces increases. Weld residual stress fields may often be expected to reduce in this manner. A separate, earlier study has shown that the stress intensity factor for a cracked plate loaded in displacement control decreases substantially as the loading plane is moved closer to the crack plane. It would therefore be expected that a similar reduction in stress intensity factor would be obtained for a residual stress analysis when displacement boundary conditions are imposed at a distance relatively close to the crack plane. This paper describes an investigation of the differences, particularly in terms of a reduction in calculated stress intensity factor, which may arise from application of displacement controlled stress intensity factor solutions, as compared with load controlled solutions, when considering weld residual stresses. Consideration is also given as to how new displacement controlled stress intensity factor solutions could be developed by modification of existing load controlled solutions.

Effect of Cladding Residual Stress Modeling Technique on Shallow Flaw Stress Intensity Factor in a Reactor Pressure Vessel

2015 ◽  
Author(s):  
Joshua Kusnick ◽  
Mark Kirk ◽  
B. Richard Bass ◽  
Paul Williams ◽  
Terry Dickson
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Room Temperature ◽  
Pressure Vessels ◽  
Temperature Model ◽  
Probabilistic Fracture Mechanics ◽  
Reactor Pressure

Prior probabilistic fracture mechanics (PFM) analysis of reactor pressure vessels (RPVs) subjected to normal cool-down transients has shown that shallow, internal surface-breaking flaws dominate the RPV failure probability. This outcome is caused by the additional crack driving force generated near the clad interface due to the mismatch in coefficient of thermal expansion (CTE) between the cladding and base material, which elevates the thermally induced stresses. The CTE contribution decreases rapidly away from the cladding, making this effect negligible for deeper flaws. The probabilistic fracture mechanics code FAVOR (Fracture Analysis of Vessels, Oak Ridge) uses a stress-free temperature model to account for residual stresses in the RPV wall due to the cladding application process. This paper uses finite element analysis to compare the stresses and stress intensity factor during a cool-down transient for two cases: (1) the existing stress-free temperature model adopted for use in FAVOR, and (2) directly applied RPV residual stresses obtained from empirical measurements made at room temperature. It was found that for a linear elastic fracture mechanics analysis, the application of measured room temperature stresses resulted in a 10% decrease in the peak stress intensity factor during a cool-down transient as compared to the stress-free temperature model.

Crack Propagation in a Gun Barrel Due to the Firing Thermo-Mechanical Stresses

2003 ◽  
Vol 125 (3) ◽  
pp. 293-298 ◽  
Author(s):  
Eric Petitpas ◽  
B. Campion
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Internal Surface ◽  
Mechanical Stresses ◽  
Stress Intensity Factor Range ◽  
Plastic Behavior ◽  
Gun Barrel

The thermo-mechanical effects of firing induce very considerable stresses on the internal surface of the gun barrels. Consequently, micro-cracks appear very soon in the life of the tube. So it is important to control the propagation of these cracks. For more than 10 years, modeling has been used by Giat-Industries to understand and to control this phenomenon. This paper focuses on the study of short crack propagation kinetics during firings. Two-dimensional modeling taking into consideration the residual stresses from a hydraulic autofrettage and the thermo-mechanical stresses due to the successive firings is presented. The cyclic plastic behavior of the material is taken into consideration. This makes it possible to observe the effect of loss of the residual stresses at the surface due to the firings. Cracks of increasing length are introduced in the model to calculate the stress intensity factor. An innovative point is the modeling of the contact between the crack lips in order to take into account the effect of crack closing during cooling. Indeed the effective stress intensity factor range is calculated using this model for numerous crack lengths. A classic Paris law is then used to predict the crack propagation kinetics. Sensitivity analysis has been carried out using this model; in particular, the effect of autofrettage on crack propagation is analyzed as well as the effect of the use of lower-strength steels.

Fatigue Life Prediction of Ship Welded Materials

2005 ◽  
Vol 297-300 ◽  
pp. 743-749
Author(s):  
Min Koo Han ◽  
Mamidala Ramulu
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Crack Closure ◽  
Fatigue Cracks ◽  
Welding Process ◽  
Weld Toe

Fatigue crack propagation life of weld toe crack through residual stress field was estimated using Elber's crack closure concept. Propagation of weld toe crack is heavily influenced by residual stresses caused by the welding process, so it is essential to take into account the effect of residual stresses on the propagation life of a weld toe crack. Fatigue cracks at transverse and longitudinal weld toe was studied, these two cases represent the typical weld joints in ship structures. Numerical and experimental studies are performed for both cases. Residual stresses near the welding area were estimated through a nonlinear thermo-elasto-plastic finite element method and the residual stress intensity factor with Glinka's weight function method. Effective stress intensity factor was calculated using the Newman-Forman-de Koning-Henriksen equation, which is based on the Dugdale strip yield model in estimating the crack closure level, U, at different stress ratios. Calculated crack propagation life coincided well with experimental results.

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