Comparison of Fracture Toughness Properties of Advanced Ferritic ODS-Alloys Based on 0.2T C(T) Specimen Tests

Based on the good experiences gained by using small specimens made of ferritic RPV materials, the Master Curve fracture toughness approach was applied to determine the fracture mechanical properties of oxide dispersion strengthened (ODS-) materials. A ferritic ODS-alloy (Fe-14Cr-1W-Ti-Y2O3) has been produced through the powder metallurgical production path via hot extrusion and hot isostatic pressing (HIP). Optimized oxide dispersion strengthened (ODS)-alloys have a promising potential to meet the foreseen requirements of components in future Gen IV power plants due to their high creep strength and swelling resistance under irradiation at elevated operational temperatures. The fracture toughness was characterized with mini 0.2T C(T) specimens in different material orientations (R-L / L-R) in the ductile-brittle and upper shelf region in the un-irradiated state, accounting especially for the ODS-material’s anisotropy as one key effect of manufacturing. Despite all tests were performed in orientation required by ASTM standards E 1921 and E 1820 not all validity criteria (e.g. height of yield strength, evenness of the crack, admissible K during testing or admissible stable crack growth) were met by the ODS-material: consequently, a valid T0 value and a standard-compliant Master Curve could not be determined for the ODS-material in the transition region especially in the respective R-L orientation, also due to a comparably low fracture toughness over the whole evaluated temperature range. Promising fracture toughness properties were obtained in the crack growth direction perpendicular to the prior main deformation (extrusion) direction, where a KJQ value of 196 MPa√m at T = 22°C was measured. Within the ductile regime, only a JQ = J0.2BL technical initiation toughness value could be calculated and at T = 22°C, a comparably large JQ of 137kJ/m2 is obtained for specimens with crack growth direction perpendicular to the extrusion direction, while in extrusion direction the toughness is again low. In addition two further ODS-materials (14YWT and PM2000) were tested and compared to the alloys above. Non-conformances of ODS relating to the material requirements in ASTM standards E1921 and E1820 were finally detected and explained.

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Fracture toughness of L-PBF fabricated aluminium–silicon: a quantitative study on the role of crack growth direction with respect to layering

Progress in Additive Manufacturing ◽

10.1007/s40964-020-00113-x ◽

2020 ◽

Vol 5 (3) ◽

pp. 259-266 ◽

Cited By ~ 1

Author(s):

L. Hitzler ◽

E. Sert ◽

E. Schuch ◽

A. Öchsner ◽

M. Merkel ◽

...

Keyword(s):

Fracture Toughness ◽

Crack Growth ◽

Quantitative Study ◽

Growth Direction ◽

Crack Growth Direction

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Fracture toughness and fatigue crack growth of oxide dispersion strengthened copper

10.2172/270445 ◽

1996 ◽

Cited By ~ 2

Author(s):

D J Alexander ◽

B G Gieseke

Keyword(s):

Fracture Toughness ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Oxide Dispersion Strengthened ◽

Oxide Dispersion

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Study on Ductile Fracture Including Shear-Lip Fracture under Mixed Mode Loading Condition

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.33-37.23 ◽

2008 ◽

Vol 33-37 ◽

pp. 23-28

Author(s):

Masanori Kikuchi ◽

Shougo Sannoumaru

Keyword(s):

Numerical Simulation ◽

Crack Growth ◽

Fracture Zone ◽

Mixed Mode ◽

Loading Condition ◽

Growth Direction ◽

Dimple Fracture ◽

Shear Lip ◽

Crack Growth Direction ◽

Fracture Tests

Dimple fracture tests are conducted under mode I and mixed mode lading conditions. Dimple fracture zone and shear-lip fracture zone are observed by scanning electron microscope precisely. It is found that crack growth direction is affected largely by the change of loading condition. It is also found that the differences of fracture pattern between mid-plane and at free surface are very large. Void diameter and crack growth direction are measured. Numerical simulation is conducted to simulate fracture tests in three-dimensional field. Gurson’s constitutive equation is used and large deformation analyses are conducted. It is assumed that void nucleation is controlled by both plastic strain and stress. Numerical results are compared with those of experiments. It is found that results of numerical simulation agree well with those of experiment qualitatively.

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Fatigue Crack Growth Rate and Fracture Toughness of API5L X65 in Sweet Environments

Volume 3: Materials Technology; Ocean Space Utilization ◽

10.1115/omae2013-10216 ◽

2013 ◽

Cited By ~ 1

Author(s):

Michael A. Tognarelli ◽

Ramgopal Thodla ◽

Steven Shademan

Keyword(s):

Fracture Toughness ◽

Growth Rate ◽

Fatigue Crack ◽

Crack Growth Rate ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Fatigue Crack Growth Rate ◽

Environmental Conditions ◽

Initiation Toughness ◽

Diffusible Hydrogen

Corrosion fatigue and fracture toughness in sour environments of APIX65 5L have typically been studied in relatively severe environments like NACE A and NACE B solutions. There are very limited data in sweet and mildly sour environments that are of interest in various applications. This paper presents fatigue crack growth frequency scans in a range of sweet and mildly sour environments as well as on different microstructures: Parent Pipe, Heat Affected Zone (HAZ) and Weld Center Line (WCL). The fatigue crack growth rate (FCGR) increased with decreasing frequency and reached a plateau value at low frequencies. FCGR in the sweet environments that were investigated did exhibit a frequency dependence (increasing with decreasing frequency) and had plateau FCGR in the range of 10–20× the in-air values. In the mildly sour environments that were investigated, FCGR was found to be about 25 to 30× higher than the in-air values. By comparison, in NACE A environments the FCGR is typically about 50× higher than the in-air values. The FCGRs of parent pipe and HAZ were found to be similar over a range of environments, whereas the WCL FCGR data were consistently lower by about a factor of 2×. The lower FCGR of the WCL is likely due to the lower concentration of diffusible hydrogen in the weld. FCGRs as a function of ΔK (stress integrity factor range) were measured on parent pipe at the plateau frequency. The measured Paris law curves were consistent with the frequency scan data. Rising displacement fracture toughness tests were performed in a range of sweet and sour environments to determine the R-curve behavior. Tests were performed in-situ at a slow K-rate of 0.05Nmm−3/2/s over a range of environmental conditions on parent pipe. The initiation toughness and the slope of the R-curve decreased sharply in the sour environments. The initiation toughness and slopes were largely independent of the notch location as well as environmental conditions. Typical values of initiation toughness were in the range of 90–110N/mm.

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A Combined Model Approach for Estimating T0

Volume 1: Codes and Standards ◽

10.1115/pvp2019-93646 ◽

2019 ◽

Author(s):

Marjorie Erickson

Keyword(s):

Fracture Toughness ◽

Master Curve ◽

Reference Temperature ◽

Initiation Toughness ◽

Correlation Model ◽

Combined Model ◽

Best Estimate ◽

Curve Model ◽

Asme Code ◽

Model Approach

Abstract The current best-estimate model describing the fracture toughness of ferritic steels is the Master Curve methodology standardized in ASTM E1921. Shortly following standardization by ASTM, efforts were undertaken to incorporate this best-estimate model into the framework of the ASME Code to reduce the conservatisms resulting from use of a reference temperature based on the nil-ductility temperature (RTNDT) to index the plane strain fracture initiation toughness (KIc). The reference temperature RTT0, which is based on the ASTM E1921-defined T0 value, was introduced in ASME Code Cases N-629 (replaced by Code Case N-851) and N-631 to replace RTNDT for indexing the ASME KIc curve. Efforts are continuing within the ASME Code to implement direct use of the Master Curve model; using the T0 reference temperature to index an elastic-plastic, KJc fracture toughness curve. Transitioning to a direct T0-based fracture toughness assessment methodology requires the availability of T0 estimates for all materials to be assessed. The historical Charpy and NDT-based regulatory approach to characterizing toughness for reactor pressure vessel (RPV) steels results in a lack of T0 values for a large population of the US nuclear fleet. The expense of the fracture toughness testing required to estimate a valid T0 value makes it unlikely that T0 will ever be widely available. Since direct implementation of best-estimate, fracture toughness models in codes and regulatory actions requires an estimate of T0 for all materials of interest it is necessary to develop an alternative means of estimating T0. A project has been undertaken to develop a combined model approach to estimating T0 from data that may include limited elastic-plastic fracture toughness KJc, Charpy, tensile, ductile initiation toughness, arrest toughness, and/or nil-ductility temperature data. Using correlations between these properties and T0 a methodology for combining estimates of T0 from several sources of data was developed. T0 estimates obtained independently from the Master Curve model, the Simple T28J correlation model, and a more complex Charpy correlation model were combined using the Mixture Probability Density Function (PDF) method to provide a single estimate for T0. Using this method, the individual T0 estimates were combined using weighting factors that accounted for sample size and individual model accuracy to optimize the accuracy and precision of the combined T0 estimate. Combining weighted estimates of T0 from several sources of data was found to provide a more refined estimate of T0 than could be obtained from any of the models alone.

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