Statistical Analysis and Monte-Carlo Simulations of Warm Prestressing of Pre-Cracked Small Single Edge Notch Bend Specimens

2013 ◽  
Author(s):  
Derreck van Gelderen ◽  
Dana Lauerova ◽  
Miroslav Posta ◽  
Vladislav Pistora ◽  
Julian Booker ◽  
...  
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Statistical Significance ◽  
Pressure Vessels ◽  
Single Edge ◽  
Warm Prestressing ◽  
Edge Notch ◽  
Predicted Values

Warm prestressing is widely acknowledged as being able to enhance material toughness, especially in steels that exhibit lower shelf cleavage fracture. The enhancement in toughness has a significant impact on the integrity of pressure vessels, particularly during severe loading conditions, such as pressurised thermal shock. In this paper, we undertake detailed statistical analyses of experimental data provided via a comprehensive programme of fracture tests at UJV (Ústav jaderného výzkumu Řež a.s.). A warm prestressing model, developed by Chell, is used to predict the change in toughness probabilistically, using Monte-Carlo methods to predict the distribution in toughness following different warm prestressing cycles. The results obtained from this model are also compared to predictions made by the Wallin approach. Experimental data was generated, at UJV for WWER 440 RPV steel, using small single-edge-notched bend SEN(B) specimens (or pre-cracked Charpy) across a range of different fracture temperatures, warm pre-stress temperatures, and levels of preload, in both as-received and irradiated conditions. In this paper, experimental data obtained only from tests on unirradiated specimens were statistically treated. A three parameter Weibull distribution was used to map the scatter observed in the virgin toughness. The statistical significance of increase in apparent fracture toughness due to warm prestressing was evaluated using the Mann-Whitney test. It was further shown by Monte-Carlo simulations that the Chell and Wallin models provide slightly conservative predictions of the resulting fracture toughness. Both, the experimentally measured and predicted values of the resulting fracture toughness, depend on the specific tests conditions, especially on the level of preload.

Reversing the Chell Model to Predict Using Monte Carlo Simulations the Original Fracture Toughness of Ferritic Steels

2018 ◽  
Author(s):  
Derreck Van Gelderen ◽  
Julian Booker
Keyword(s):  
Fracture Toughness ◽  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Compact Tension ◽  
Load Cycle ◽  
Small Scale ◽  
Ferritic Steels ◽  
Single Edge ◽  
Edge Notch ◽  
Single Edge Notch Bend

Warm pre-stress (WPS) is the process of subjecting a pre-cracked component to a load cycle at a temperature higher than subsequent operating temperatures. This process is widely acknowledged as being able to enhance the load to fracture, especially in ferritic steels which exhibit lower shelf cleavage fracture. Various models exist to predict this type of enhancement, with the Chell model being one of the most widely used within industry. Previous research conducted by Van Gelderen et al. have reformulated the Chell model to create a method of undertaking Monte Carlo Simulations (MCS) to study the effect of WPS on brittle fracture. Following on from this research, the Chell model could effectively be reversed providing a means of predicting the underlying fracture toughness from experimental WPS data. It also offers the possibility of assessing whether or not a specific specimen has indeed seen an enhancement, solely based on its experimental apparent toughness post WPS. The reverse Chell model was applied to different experimental data and provided reasonable estimates of the original fracture toughness. In the same way that the traditional Chell model offers conservative estimates, the reverse Chell model also provides “reverse conservative” estimates of the original fracture toughness. It was also used to provide confidence that a typical fatigue pre-cracking procedure performed according to ASTM standard E399 would not be sufficient to induce a WPS benefit on the specimens. This type of check can be of particularly interest when manufacturing small scale specimens (small scale Single Edge Notch Bend (SENB) or miniature sized Compact Tension C(T) specimens); a practice often favoured by industry to maximise the number of tests possible.

Comparative analysis and verification of engineering methods of shallow cracks effect for fracture toughness prediction for reactor pressure vessels

2020 ◽  
pp. 140-165
Author(s):  
V. I. Kostylev ◽  
B. Z. Margolin
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Comparative Analysis ◽  
Nuclear Reactor ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Local Methods ◽  
European Method ◽  
Shallow Crack ◽  
Reactor Pressure

The main features of shallow cracks fracture are considered, and a brief analysis of methods allowing to predict the temperature dependence of the fracture toughness KJC (T) for specimens with shallow cracks is given. These methods include DA-method, (JQ)-method, (J-T)-method, “local methods” with its multiparameter probabilistic approach, GP method uses power approach, and also two engineering methods – RMSC (Russian Method for Shallow Crack) and EMSC (European Method for Shallow Crack). On the basis of 13 sets of experimental data for national and foreign steels, a detailed verification and comparative analysis of these two engineering methods were carried out on the materials of the VVER and PWR nuclear reactor vessels considering the effect of shallow cracks.

Comparative Analysis of Fracture Toughness Obtained by Different Techniques in Alumina Matrix - Dispersed TZP Zirconia Composites

2016 ◽  
Vol 869 ◽  
pp. 46-51
Author(s):  
Daniel Alessander Nono ◽  
Eron Fernandes da Silva ◽  
Maria do Carmo de Andrade Nono ◽  
Francisco Piorino Neto ◽  
Sergio Luiz Mineiro
Keyword(s):  
Fracture Toughness ◽  
Tetragonal Zirconia ◽  
Ceramic Composites ◽  
Alumina Matrix ◽  
Single Edge ◽  
Chemical Inertness ◽  
Edge Notch ◽  
Properties Of Materials ◽  
Experimental Values ◽  
Benefit Cost

The fracture toughness is one of the requirements for mechanical properties of materials for use in satellites. The ceramic TZP zirconia (tetragonal zirconia polycrystals) have been investigated for applications in ballistic armor. Due to the chemical inertness and fracture toughness, this material has the potential to act as a screen against impacts of micrometeorites and space debris. The ceramic composites of alumina-zirconia 3Y-TZP (tetragonal zirconia polycrystals doped with 3 mol% ytria ) are the materials with the best benefit / cost for this application. This paper presents and discusses the results obtained from the use of two techniques for determining fracture toughness. The composite alumina - 18.5% of 3Y-TZP zirconia nanoparticles obtained from deflocculated powders have been tested for Vickers and the SEVNB penetration method (Single-Edge-Notch Beam V) to obtain the fracture toughness values (KIC). The KIC values obtained were analyzed due to the lower dispersion of experimental values. The SEVNB method showed better reliability in determining the toughness values in the studied ceramics.

Fracture toughness of Si3N4 fibers: A combined methodology based on single-edge notch tension and micropillar splitting

2018 ◽  
Vol 44 (17) ◽  
pp. 22036-22040
Author(s):  
Xun Sun ◽  
Haitao Liu ◽  
Lingwei Yang ◽  
Ru Jiang ◽  
Haifeng Cheng
Keyword(s):  
Fracture Toughness ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch

Fracture Mechanism and Fracture Toughness at the Interface Between Cortical and Cancellous Bone

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Pankaj Shitole ◽  
Arpan Gupta ◽  
Rajesh Ghosh
Keyword(s):  
Fracture Toughness ◽  
Cortical Bone ◽  
Cancellous Bone ◽  
Fracture Mechanism ◽  
Fracture Mechanisms ◽  
J Integral ◽  
Single Edge ◽  
Plastic Part ◽  
Edge Notch ◽  
Sample Width

The microstructure at the interface of cortical and cancellous bone is quite complicated. The fracture mechanisms at this location are necessary for understanding the comprehensive fracture of the whole bone. The goal of this study is to identify fracture toughness in terms of J integral and fracture mechanism at the interface between cortical and cancellous bone. For this purpose, single edge notch bend (SENB) specimens were prepared from bovine proximal femur according to ASTM-E399 standard. Bone samples were prepared such that half of the sample width consists of cortical bone and other half of the width was cancellous bone; this interfacial bone is referred as a corticellous bone. Elastic–plastic fracture mechanics was used to measure fracture toughness. The J integral (both elastic and plastic) was used to quantify the fracture toughness. The plastic part of J integral value (Jpl) of corticellous specimen was 9310 J m−2, and shown to be 27 times of the J integral of the elastic part (Jel), 341 J m−2. The total J integral of the corticellous bone was found to be 9651 J m−2, which is close to two times of the cortical bone, 4731 J m−2. This study observed that J integral of corticellous bone is higher than the cortical bone since more energy is required for plastic deformation of corticellous bone due to crack branches and slowdown at the interface between cortical and cancellous bone.

Fracture Toughness Estimation for Pipeline Girth Welds

2002 ◽  
Author(s):  
Henryk G. Pisarski ◽  
Colin M. Wignall
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Loading Modes ◽  
Girth Welds ◽  
The Relationship ◽  
Single Edge Notch Bend

The relationship between fracture toughness estimated using standard single edge notch bend (SENB), single edge notch tension (SENT) test specimens and fracture toughness associated with a circumferential flaw in a pipe girth weld is explored in terms of constraint using the Q parameter. It is shown that in the elastic-plastic regime, use of standard deeply notched SENB specimens provides a conservative assessment of fracture toughness, for both weld metal and HAZ, because of the high constraint associated with this specimen geometry. Use of specimen geometries and loading modes associated with lower constraint (e.g. SENT and shallowed notched SENB specimens), allow for improved estimates of fracture toughness to be made that are appropriate for the assessment of circumferential flaws in pipe girth welds. Recommendations are given on the specimen designs and notch orientations to be employed when evaluating weld metal and HAZ fracture toughness.

The Temperature Dependence of Yield Stress and Fracture Toughness in Unstabilized Zirconia Crystals

1986 ◽  
Vol 78 ◽  
Author(s):  
T. W. Coyle ◽  
R. P. Ingel ◽  
P. A. Willging
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Test Temperature ◽  
Room Temperature ◽  
Single Edge ◽  
Melting Technique ◽  
Strength Tests ◽  
Edge Notch

ABSTRACTThe flexural strength and the single edge notch beam fracture toughness of undoped ZrO2 crystals, grown by the skull melting technique, were examined from room temperature to 1400°C. On heating the toughness increased with test temperature to a maximum of 4.0 MPajm at 1225°C then gradually decreased to 2.6 MPa/m. Upon cooling after a 20 minute hold at 1250°C an increase in toughness to 5 MPa/m was observed at 1200°C; upon cooling to lower temperatures Kic gradually diminished. The loaddeflection curves for the flexural strength tests showed marked nonlinearity before failure for samples tested on cooling. The temperature dependence of the apparent yield stress suggests that initial yielding occurs by slip above 1200°C but that from 1200°C to 1050°C the observed yielding is due to stress induced tetragonal to monoclinic transformation.

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