Application of the material inhomogeneity effect for the improvement of fracture toughness of a brittle polymer

2020 ◽  
Vol 224 ◽  
pp. 106776 ◽  
Author(s):  
Abhishek Tiwari ◽  
Johannes Wiener ◽  
Florian Arbeiter ◽  
Gerald Pinter ◽  
Otmar Kolednik
Keyword(s):  
Fracture Toughness ◽  
Material Inhomogeneity ◽  
Brittle Polymer

Evaluation of Fracture Toughness of a SA580 Gr. 3 Reactor Pressure Vessel Using a Bimodal Master Curve Approach

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jong-Min Kim ◽  
Seok-Min Hong ◽  
Min-Chul Kim ◽  
Bong-Sang Lee
Keyword(s):  
Fracture Toughness ◽  
Cooling Rate ◽  
Pressure Vessel ◽  
Master Curve ◽  
Random Parameter ◽  
Random Inhomogeneity ◽  
Reactor Pressure Vessel ◽  
Inhomogeneous Materials ◽  
Material Inhomogeneity ◽  
Reactor Pressure

Abstract The standard master curve (MC) approach has a major limitation in that it is only applicable to homogeneous datasets. In nature, steels are macroscopically inhomogeneous. Reactor pressure vessel (RPV) steel has different fracture toughness with varying distance from the inner surface of the wall due to the higher cooling rate at the surface (deterministic material inhomogeneity). On the other hand, the T0 value itself behaves like a random parameter when the datasets have large scatter because the datasets are for several different materials (random inhomogeneity). In this paper, four regions, the surface, 1/8 T, 1/4 T, and 1/2 T, were considered for fracture toughness specimens of Korean Standard Nuclear Plant (KSNP) SA508 Gr. 3 steel to provide information on deterministic material inhomogeneity and random inhomogeneity effects. Fracture toughness tests were carried out for the four regions at three test temperatures in the transition region and the microstructure of each region was analyzed. The amount of upper bainite increased toward the center, which has a lower cooling rate; therefore, the center has lower fracture toughness than the surface so reference temperature (T0) is higher. The fracture toughness was evaluated using the bimodal master curve (BMC) approach. The results of the BMC analyses were compared with those obtained via a conventional master curve analyses. The results indicate that the bimodal master approach considering inhomogeneous materials provides a better description of scatter in the fracture toughness data than a conventional master curve analysis does.

Analysis of Material Inhomogeneity in the European Round Robin Fracture Toughness Data Set

2008 ◽  
Vol 5 (9) ◽  
pp. 101512 ◽  
Author(s):  
James A. Joyce ◽  
Xiaosheng Gao ◽  
Richard Neu ◽  
Kim Wallin ◽  
Steven R. Thompson ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Round Robin ◽  
Data Set ◽  
Material Inhomogeneity

Interlaminar fracture toughness of flax-epoxy composites

2016 ◽  
Vol 36 (2) ◽  
pp. 121-136 ◽  
Author(s):  
F Bensadoun ◽  
I Verpoest ◽  
AW Van Vuure
Keyword(s):  
Fracture Toughness ◽  
Epoxy Composite ◽  
Flax Fibre ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Brittle Polymer ◽  
Tensile Toughness

The purpose of this study was to determine the influence of fibre architectures on the interlaminar fracture toughness and tensile toughness of flax fibre epoxy composites. The fracture toughness was investigated for both Mode I (GIC) and Mode II (GIIC) for seven flax-epoxy architectures: one plain weave, two twill 2 × 2 weaves, a quasi-unidirectional and a unidirectional architecture, the UD’s being tested in both [0,90] and [90,0] composite lay-ups. The results of the Mode I and Mode II showed promising results of the flax-epoxy composite performance. The addition of flax fibre increases the GIC and GIIC of the composites over that of the unreinforced brittle polymer by at least two to three times. Further improvements are made with the use of woven textiles. The tensile toughness was found to be a good indicator of the capacity of a material to sustain perforation or non-perforation impact.

Application of the Master Curve Approach for Abnormal Material Conditions

2007 ◽  
Author(s):  
Tapio Planman ◽  
William Server ◽  
Kim Wallin ◽  
Stan Rosinski
Keyword(s):  
Fracture Toughness ◽  
Lower Bound ◽  
Master Curve ◽  
Pressure Vessels ◽  
Data Sets ◽  
Inhomogeneous Materials ◽  
Data Set ◽  
Material Inhomogeneity ◽  
Fracture Modes ◽  
Material Conditions

The range of applicability of Master Curve testing Standard ASTM E 1921 is limited to macroscopically homogeneous steels with “uniform tensile and toughness properties”. A majority of structural steels appear to satisfy this requirement by exhibiting fracture toughness data which comply with the assumed KJc vs. temperature dependence and scatter within the specified validity area. As indicated in ASTM E 1921 a criterion for material macroscopic inhomogeneity is often applied using the 2% lower bound (possibly also the 98% upper bound). Data falling below this 2% lower-limit curve may be an indication of material inhomogeneity or susceptibility to grain boundary fracture. When this situation occurs, it is recommended to analyze the material with the so-called SINTAP procedure, which is intended for randomly inhomogeneous materials to assure a conservative lower-bound estimate. When a data set distinctly consists of two or more different data populations instead of one (due to variation of irradiation dose or specimen extraction depth, for instance) adoption of a bimodal (or a multimodal) Master Curve model is generally appropriate. These modal models provide information if the deviation of distributions is statistically significant or if different distributions truly exist for values of reference transition temperature, T0, characteristic of separate data populations. In the case of data sets representing thick-walled structures (i.e., reactor pressure vessels), indications of abnormal fracture toughness data can be encountered such that material inhomogeneity or fracture modes other than pure cleavage should be suspected. A state-of-the-art review for extended, non-standard Master Curve data and techniques highlights limits of applicability in situations where the basic ASTM E 1921 procedure is not appropriate for material homogeneity or different fracture modes.

Validity of the Master Curve Temperature Dependence Assumption for Highly Embrittled RPV Materials: Results From the IAEA Coordinated Research Project (CRP-8)

2009 ◽  
Author(s):  
Tapio Planman ◽  
Kunio Onizawa ◽  
William Server
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
Master Curve ◽  
Shape Change ◽  
Transition Curve ◽  
Curve Shape ◽  
Topic Area ◽  
Material Inhomogeneity ◽  
Realistic Description ◽  
Definition Of

The fracture toughness temperature dependence (transition curve shape) has been discussed almost since the original empirical definition of the curve in 1991. The data sets showing anomalous fracture behaviour of highly irradiated VVER-1000 pressure vessel steels presented in 2000’s have further enhanced this discussion and even a special model has been proposed for highly irradiated steels, including a mathematical definition of the curve shape change. Although in most cases the standard Master Curve (MC) approach, assuming a constant transition curve shape, has proven to give a realistic description for also highly irradiated ferritic steels, there are grades which show for example abnormally weak temperature dependence. In these cases, however, an obvious reason for the behaviour may be that the material does not fail by the mechanism assumed in the MC model. The fracture toughness data collected and analysed in the CRP-8 Topic Area 3 supports the validity of the curve shape assumption of ASTM E1921 also in case of irradiated steels and gives no rise to change the present definition. The Master Curve C-parameter (the shape parameter) estimation is proposed as an appropriate analysis method when there is need to estimate also the temperature dependence, whereas the SINTAP procedure is recommended for ensuring conservative lower bound estimates when material inhomogeneity is suspected. The results show that irradiation may slightly lower the fracture toughness in the upper transition region in relation to that predicted by ASTM E1921, but the effect after moderate T0 shift values (up to about 100°C) seems to be negligible. The investigated steels exhibit no or very weak correlation between the C-parameter and T0.

Fracture Toughness Assessment of SA508 Gr 3 Steel for KSNP RPV Using Conventional and Bimodal Master Curve Approaches

2014 ◽  
Author(s):  
Jongmin Kim ◽  
Minchul Kim ◽  
Kwonjae Choi ◽  
Bongsang Lee
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Random Parameter ◽  
Random Inhomogeneity ◽  
Curve Analysis ◽  
Large Scatter ◽  
Inhomogeneous Materials ◽  
Quenching Rate ◽  
Material Inhomogeneity ◽  
Rpv Steel

The standard master curve approach has the major limitation, which is only applicable to homogeneous datasets. In nature, steels are macroscopically inhomogeneous and thus the fracture toughness has larger scatters than expected by a conventional master curve approach. RPV steel has different fracture toughness with varying distance from the inner surface of the wall. Regarding this, a clear tendency was reported in that the toughness extracted near the surface had to be higher than in the center region due to the higher quenching rate at the surface (deterministic material inhomogeneity). On the other hand, the T0 value itself behaves like a random parameter when the datasets have a large scatter due to the datasets consisting of several different materials such as welding region (random inhomogeneity). In the present paper, four regions, the surface, 1/8T, 1/4T and 1/2T, were considered for fracture toughness specimens of KSNP (Korean Standard Nuclear Plant) SA508 Gr. 3 steel to provide deterministic material inhomogeneity and random inhomogeneity effect. Specimens were extracted from these four regions and fracture toughness tests were performed at various temperatures in the transition region. Several concepts were provided for the master curve of inhomogeneous materials such as a bimodal and random inhomogeneous master curve scheme, and among them, the bimodal master curve analyses were reviewed and compared with a conventional master curve approach to find the random inhomogeneity. The bimodal master curve considering inhomogeneous materials provides better description of scatter in fracture toughness data than conventional master curve analysis, but it is unclear to provide evidence that the bimodal analysis lines follow the data more closely than the conventional master curve analysis.

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