A New Correction Procedure to Correct the Predicted Crack Extension Direction of a Mixed Mode Crack Path

2007 ◽  
Vol 348-349 ◽  
pp. 89-92
Author(s):  
Tore Lucht ◽  
M.H. Aliabadi
Keyword(s):  
Crack Growth ◽  
Crack Extension ◽  
Crack Path ◽  
Growth Direction ◽  
Correction Procedure ◽  
Growth Criterion ◽  
Incremental Formulation ◽  
Crack Growth Direction ◽  
Extension Direction ◽  
Reference Correction

In an incremental crack extension analysis each crack increment is in general modelled with a straight extension. In order to avoid introduction of an error when the local crack growth criterion is used with an incremental formulation, each straight crack extension would have to be infinitesimal as the crack growth direction changes when the crack grows. A correction procedure to correct the extension direction of the increment can however be applied to ensure that a unique crack path is achieved with different analyses of the same problem performed with different size of the crack-extension increments. A proposed correction procedure and an reference correction procedure are demonstrated by solving a computational crack growth example. The demonstration shows that analyses of the crack path performed with big crack extensions and the proposed crack correction procedure are in excellent agreement with analyses of the crack path performed with very small crack extensions. Furthermore it is shown that the reference correction procedure has a tendency to overcorrect the crack growth direction if the stop criterion for the iterative correction procedure is not specified for each new crack growth analysis.

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

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.

scholarly journals Numerical predictions of crack growth direction in a railhead under contact, bending and thermal loads

2022 ◽  
pp. 108218
Author(s):  
Mohammad Salahi Nezhad ◽  
Dimosthenis Floros ◽  
Fredrik Larsson ◽  
Elena Kabo ◽  
Anders Ekberg
Keyword(s):  
Crack Growth ◽  
Growth Direction ◽  
Thermal Loads ◽  
Numerical Predictions ◽  
Crack Growth Direction

The Influence of Aging Treatments on the Notched Tensile Strength of Ti-6Al-6V-2Sn Laser Welds

2008 ◽  
Vol 47-50 ◽  
pp. 185-188
Author(s):  
Lv Wen Tsay ◽  
C.X. Lee ◽  
W.C. Chung ◽  
C. Chen
Keyword(s):  
Tensile Strength ◽  
Crack Growth ◽  
High Hardness ◽  
Tensile Tests ◽  
Growth Direction ◽  
Laser Welds ◽  
Different Temperatures ◽  
Crack Growth Direction ◽  
Notched Tensile Strength ◽  
Fracture Features

Notched tensile tests were performed to evaluate the presence of notch on the tensile strength of Ti-6Al-6V-2Sn laser welds, which were post-weld aged at different temperatures. Ti-6Al-6V-2Sn laser welds showed notch brittleness except for the welds aged at/above 704 oC. Fine acicular α uniformly distributed in β matrix in the fusion zone accounted for the high hardness (Hv 440) as compared with mill-annealed base metal. Overaging at/above 704 oC resulted in coarsening the microstructures and decreased notch brittleness. The fracture features of the weld were strongly affected by the orientation of the solidified structures with respect to the crack growth direction.

3D Textural Analysis of Fatigue Fracture Surfaces

2020 ◽  
Vol 405 ◽  
pp. 259-263
Author(s):  
Hynek Lauschmann ◽  
Karel Tesař ◽  
Tereza Vronková
Keyword(s):  
Crack Growth ◽  
Real Data ◽  
Growth Direction ◽  
High Ratio ◽  
Textural Features ◽  
Aisi 304L ◽  
Fracture Surfaces ◽  
Steel Aisi ◽  
Crack Growth Direction ◽  
Wavelet Decompositions

Three CT specimens from stainless steel AISI 304L were subjected to constant amplitude cyclic loadings with various asymmetries. Crack growth was recorded in detail. Fracture surfaces were documented by 3D maps in about 110 locations in the crack growth direction. 3D maps and their local gradients were represented by 2D wavelet decompositions in 10 levels resulting in 60 textural features. Statistical models expressing crack growth rate as a function of textural features were optimized. Training and testing approach, a high ratio of overfitting, and testing of significance of components ensured model's robustness. Quality of results is documented by graphs confronting model outputs with real data known from experiment. Results are acceptable in all cases.

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

2016 ◽  
Author(s):  
Charles C. Eiselt ◽  
David T. Hoelzer ◽  
Yann de Carlan ◽  
Hieronymus Hein ◽  
Marta Serrano ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Master Curve ◽  
Extrusion Direction ◽  
Oxide Dispersion Strengthened ◽  
Growth Direction ◽  
Initiation Toughness ◽  
Oxide Dispersion ◽  
Crack Growth Direction ◽  
Ods Alloys

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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