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

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.

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.

scholarly journals Crack growth pattern analysis of monolithic glass ceramic on a titanium abutment for single crown implant restorations using smooth particle hydrodynamics algorithm

2021 ◽  
Vol 13 (1) ◽  
pp. 7-11
Author(s):  
Mohammad Kashfi ◽  
Parisa Fakhri ◽  
Ataollah Ghavamian ◽  
Payam Pourrabia ◽  
Fatemeh Salehi Ghalesefid ◽  
...  
Keyword(s):  
Crack Growth ◽  
Dynamic Loading ◽  
Glass Ceramic ◽  
Growth Direction ◽  
Smooth Particle Hydrodynamics ◽  
Incisal Edge ◽  
Particle Hydrodynamics ◽  
Implant Crown ◽  
Crack Growth Direction ◽  
Sph Algorithm

Background. Glass ceramic materials have multiple applications in various prosthetic fields. Despite the many advantages of these materials, they still have limitations such as fragility and surface machining and ease of repairing. Crack propagation has been a typical concern in fullceramic crowns, for which many successful numerical simulations have been carried out using the extended finite element method (XFEM). However, XFEM cannot correctly predict a primary crack growth direction under dynamic loading on the implant crown. Methods. In this work, the dental implant crown and abutment were modeled in CATIA V5R19 software using a CT-scan technique based on the human first molar. The crown was approximated with 39514 spherical particles to reach a reasonable convergence in the results. In the present work, glass ceramic was considered the crown material on a titanium abutment. The simulation was performed for an impactor with an initial velocity of 25 m/s in the implant-abutment axis direction. We took advantage of smooth particle hydrodynamics (SPH) such that the burden of defining a primary crack growth direction was suppressed. Results. The simulation results demonstrated that the micro-crack onset due to the impact wave in the ceramic crown first began from the crown incisal edge and then extended to the margin due to increased stress concentration near the contact region. At 23.36 µs, the crack growth was observed in two different directions based on the crown geometry, and at the end of the simulation, some micro-cracks were also initiated from the crown margin. Moreover, the results showed that the SPH algorithm could be considered an alternative robust tool to predict crack propagation in brittle materials, particularly for the implant crown under dynamic loading. Conclusion. The main achievement of the present study was that the SPH algorithm is a helpful tool to predict the crack growth pattern in brittle materials, especially for ceramic crowns under dynamic loading. The predicted crack direction showed that the initial crack was divided into two branches after its impact, leading to the crown fracture. The micro-crack initiated from the crown incisal edge and then extended to the crown margin due to the stress concentration near the contact area.

Creep–fatigue crack growth in Jethete M152 at 550°C under mixed mode conditions

1992 ◽  
Vol 27 (1) ◽  
pp. 49-57 ◽  
Author(s):  
T H Hyde ◽  
A C Chambers
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Mixed Mode ◽  
Growth Direction ◽  
Fatigue Tests ◽  
Creep Fatigue ◽  
Crack Growth Direction ◽  
Creep Fatigue Crack ◽  
Dominant Influence

Creep–fatigue tests were carried out on Jethete M152 at 550°C under mode I, mode II, and mixed mode ( K1/ KII ≈ 1.6) conditions. The results were correlated and compared with corresponding fatigue and creep data. The results indicated that damage due to creep caused a larger increase in fatigue crack growth rate than a simple superposition model would predict. Also creep appeared to have a more dominant influence than fatigue on crack growth direction.

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