Experimental and extended finite element simulations for tensile fracture phenomenon of cryorolled aluminium alloy 5754

2021 ◽  
pp. 095440622110282
Author(s):  
Pankaj Kumar
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Tensile Fracture ◽  
Crack Growth Behavior ◽  
Work Piece ◽  
Extended Finite Element ◽  
Propagation Behavior ◽  
Gauge Section ◽  
Contour Plots ◽  
Annealing Heat Treatment

In present work, cryorolling is performed to obtain the higher mechanical strength of the received material. Close to 50% and 30% increments in tensile and yield strengths of the material are observed for 40% thickness reduction. However, limited ductility has been obtained for cryorolled samples. Post annealing heat treatment is performed on cryorolled samples to obtain combined enhancement in strength and ductility of the alloy. Difference in the ductile fracture along with crack initiation and its advancement with plastic straining is also compared for cryorolled and annealed cryorolled samples. Fracture angle and crack propagation behavior at vicinity of gauge section is evaluated by using extended finite element method (XFEM) and compared with experimental tested work piece. XFEM has been adopted to simulate the crack growth behavior from nucleation till fracture of the investigated alloy. Triaxial stress contour plots are also captured by XFEM near to the crack initiation zone.

Assessment of Pipeline Spiral Weld Cracks Subjected to Internal Pressure

2018 ◽  
Author(s):  
Mark C. Neuert ◽  
Thomas J. Dessein ◽  
Millan Sen
Keyword(s):  
Finite Element ◽  
Crack Length ◽  
Normal Stress ◽  
Extended Finite Element Method ◽  
Stress Component ◽  
General Tendency ◽  
Extended Finite Element ◽  
Pipe Axis ◽  
Propagation Behavior ◽  
Longitudinal Cracks

Spirally welded pipelines can make up significant portions of operator transmission systems, and may contain manufacturing anomalies that are susceptible to fatigue growth. Modifications to inputs of crack assessment models, such as CorLAS®, are required to account for the angle these cracks make with respect to the longitudinal pipe axis, given that these crack assessment models were developed for longitudinally orientated cracks. Two such modifications were investigated and are discussed in this paper. One approach considered the normal stress component perpendicular to the angled crack, for which a stress transformation calculator was developed. Another approach, adapted from API 579 and BS7910 standards, used an effective crack length calculated as the longitudinal projection of the full length of an angled crack. Failure pressures calculated using these approaches were compared to validated finite element (FE) results. For both modifications, the pressure capacity increased for angled cracks versus longitudinal cracks. The transformed normal stress approach resulted in non-conservative failure pressure predictions with respect to the FE models, whereas the modified crack length approach was conservative. Additionally, the extended finite element method (XFEM) was used to investigate the propagation behavior of angled cracks. It was found that the general tendency was for propagation parallel to the longitudinal pipe axis; however, when considering weld residual stresses, the crack propagation would be directed toward the direction of the spiral seam.

Predictions of fracture load, crack initiation angle, and trajectory for V-notched Brazilian disk specimens under mixed mode I/II loading with negative mode I contributions

2017 ◽  
Vol 27 (8) ◽  
pp. 1173-1191 ◽  
Author(s):  
Bahador Bahrami ◽  
Majid R Ayatollahi ◽  
AR Torabi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Extended Finite Element Method ◽  
Fracture Load ◽  
Shear Loading ◽  
Mode I ◽  
Extended Finite Element ◽  
Brazilian Disk ◽  
Crack Initiation Angle

In this paper, first the fracture load, the crack initiation angle and the crack trajectory are experimentally measured for the round-tip V-notched Brazilian disk specimen made of polymethyl-methacrylate under compressive-shear loading. Then, the fracture load and the crack initiation angle are predicted by using the extended finite element method on the basis of the linear cohesive crack criterion. The fracture trajectory of the round-tip V-notched Brazilian disk specimens is also estimated by means of the extended finite element method and the incremental methods. Both the experimental observations and the theoretical fracture models indicate that although the notch bisector line is under compressive-shear loading, one half of the notch border still sustains tensile stresses and fracture takes place from this half. A very good agreement is shown to exist between the theoretical predictions and the experimental results for various notch opening angles and different notch radii.

Study of Crack Initiation and Propagation in TBCs by Experiments and Extended Finite Element Method

2013 ◽  
Vol 331 ◽  
pp. 129-132 ◽  
Author(s):  
Jing Xin Su ◽  
Zhao Hui Ji ◽  
Zhi Yong Han ◽  
Hua Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Thermal Cycling ◽  
Extended Finite Element Method ◽  
Interface Roughness ◽  
Crack Initiation And Propagation ◽  
Extended Finite Element ◽  
Initiation And Propagation ◽  
Element Method

CoNiCrAlY bond coat (BC) and top ceramic coating (TCC) was fabricated on the GH99 super alloy by high velocity oxyfuel spray (HVOF) and air plasma spray (APS), respectively. Thermal cycling treatment was applied to the thermal barrier coatings (TBCs). The cross-sectional images of crack initiation and propagation of TBCs after treatment were investigated by scanning electron micrograph (SEM), meanwhile crack initiation and propagation in TBCs were analyzed based upon ABAQUS software using extended finite element method (XFEM). The results show that, crack initiation and propagation can be easily traced via microscopy at the interface areas in TBCs; after thermal cycling treatments, the crack associated with the TCC/TGO interface morphology initiates at interface peak area and propagates along TCC/TGO interface with thermal cycles; the interface roughness affects the crack magnitude in length and width obviously, the rougher the morphology, the bigger the crack is; the XFEM is a novel and effective method to well predict the crack initiation and calculate the crack propagation, and simulation and experimental results fit well.

scholarly journals Investigating the Effect of Interlayer Geo-stress Difference on Hydraulic Fracture Propagation: Physical Modeling and Numerical Simulations

2016 ◽  
Vol 9 (1) ◽  
pp. 195-206 ◽  
Author(s):  
Xiaosen Shang ◽  
Yunhong Ding ◽  
Lifeng Yang ◽  
Yonghui Wang ◽  
Tao Wang
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Hydraulic Fracture ◽  
Physical Simulation ◽  
Fracture Propagation ◽  
Extended Finite Element ◽  
Final Shape ◽  
Propagation Behavior ◽  
Element Simulation ◽  
Fracture Height

The morphological control of the fracture has a great impact on the effectiveness of the hydraulic fracturing; the geostress difference between productive interval and barriers is one of controlling factors for the fracture height control. The propagation behavior of the hydraulic fracture was studied using the 3D physical simulation under conditions of the presence and absence of the interlaminar geostress difference. Combined with the result of the acoustic monitoring, the dynamic propagation process and the final shape of fracture were achieved. It shows that the lateral and vertical propagations of the fracture simultaneously occurred without the interlaminar geostress difference, and a fracture with round-shape face was finally presented. On the contrary, under the presence of the interlaminar geostress difference, due to the barrier effect of the high stress barrier on the vertical propagation of the fracture, the fracture height was obviously limited after the fracture propagated to the interval boundary. Therefore, the final shape of the fracture face was elliptical. Moreover, the extended finite element simulation was also adopted to analyze the propagation of the hydraulic fracture under two conditions mentioned above, and the result was consistent with that of the physical simulation. This verifies the feasibility of the extended finite element simulation method; therefore, this method was used to further simulate the fracture propagation behavior when several layers with different stiffness simultaneously exist. The result presents that during the fracture propagation, the fracture passed through the layer which has relatively weak stiffness and stopped before the layer which has stronger stiffness. Conclusions of this study can provide reference for the research of fracture propagation in complex geostress reservoirs.

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