scholarly journals The Crack Propagation Trend Analysis in Ceramic Rolling Element Bearing considering Initial Crack Angle and Contact Load Effect

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhe Yuan ◽  
Bohan Wang ◽  
Chao Liu ◽  
Zhan Wang ◽  
Xiaochen Zhang ◽  
...  
Keyword(s):  
Finite Element ◽  
Silicon Nitride ◽  
Crack Propagation ◽  
Crack Growth ◽  
Surface Crack ◽  
Initial Crack ◽  
Silicon Nitride Ceramic ◽  
Ball Surface ◽  
Crack Angle ◽  
Bearing Ball

Silicon nitride ceramic bearings are widely used for their excellent performance. However, due to their special manufacturing method, cracks will occur on ceramic ball surface, and this initial surface crack will propagate under the action of cyclic stress, which will lead to material spalling. This will greatly limit its service life in practical applications, especially under heavy load at high speed. Therefore, it is necessary to study the surface crack propagation of silicon nitride ceramic bearings. In this paper, the effect of initial crack angle and contact load on crack growth is analysed by the finite element method (FEM). A three-dimensional finite element model of a silicon nitride bearing ball containing an initial crack is created by the FEM. The cracks are initially classified based on the angle between the crack and the bearing ball surface, and the location of the most dangerous load for each type of crack is known by theoretical analysis. The stress intensity factors (SIFs) are calculated for the crack front to investigate the effect of load position on crack growth. Subsequently, the SIFs are calculated for each type of crack angle subdivided again to investigate the effect of crack angle on crack propagation.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

A research on fatigue crack growth monitoring based on multi-sensor and data fusion

2019 ◽  
pp. 147592171986572
Author(s):  
Chang Qi ◽  
Yang Weixi ◽  
Liu Jun ◽  
Gao Heming ◽  
Meng Yao
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Data Fusion ◽  
Crack Propagation ◽  
Finite Element Model ◽  
Crack Length ◽  
Crack Growth ◽  
Lamb Wave ◽  
Element Model

Fatigue crack propagation is one of the main problems in structural health monitoring. For the safety and operability of the metal structure, it is necessary to monitor the fatigue crack growth process of the structure in real time. In order to more accurately monitor the expansion of fatigue cracks, two kinds of sensors are used in this article: strain gauges and piezoelectric transducers. A model-based inverse finite element model algorithm is proposed to perform pattern recognition of fatigue crack length, and the fatigue crack monitoring experiment is carried out to verify the algorithm. The strain spectra of the specimen under cyclic load in the simulation and experimental crack propagation are obtained, respectively. The active lamb wave technique is also used to monitor the crack propagation. The relationship between the crack length and the lamb wave characteristic parameter is established. In order to improve the recognition accuracy of the crack propagation mode, the random forest and inverse finite element model algorithms are used to identify the crack length, and the Dempster–Shafer evidence theory is used as data fusion to integrate the conclusion of the two algorithms to make a more accountable and correct judge of the crack length. An experiment has been conducted to demonstrate the effectiveness of the method.

Finite Element Modeling for Energy Release Rate in Human Cortical Bone

Volume 2 ◽  
2004 ◽  
Author(s):  
Saiphon Charoenphan ◽  
Apiwon Polchai
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Finite Element Modeling ◽  
Energy Release Rate ◽  
Cortical Bone ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Slow Crack Growth ◽  
Finite Element Models

The energy release rates in human cortical bone are investigated using a hybrid method of experimental and finite element modeling techniques. An explicit finite element analysis was implemented with an energy release rate calculation for evaluating this important fracture property of bones. Comparison of the critical value of the energy release rate, Gc, shows good agreement between the finite element models and analytical solutions. The Gc was found to be approximately 820–1150 J/m2 depending upon the samples. Specimen thickness appears to have little effect on the plane strain condition and pure mode I assumption. Therefore the energy release rate can be regarded as a material constant and geometry independent and can be determined with thinner specimens. In addition, the R curve resulting from the finite element models during slow crack growth shows slight ductility of the bone specimen that indicates an ability to resist crack propagation. Oscillations were found at the onset of the crack growth due to the nodal releasing application in the models. In this study light mass-proportional damping was used to suppress the noises. Although this techniques was found to be efficient for this slow crack growth simulation, other methods to continuously release nodes during the crack growth would be recommended for rapid crack propagation.

The Implementation of Inter-Element Model for Crack Growth Simulation

2004 ◽  
Vol 261-263 ◽  
pp. 687-692 ◽  
Author(s):  
Ahmad Kamal Ariffin ◽  
Syifaul Huzni ◽  
Nik Abdullah Nik Mohamed ◽  
Mohd Jailani Mohd Nor
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Crack Problem ◽  
Adaptive Mesh ◽  
Element Model ◽  
Error Norm ◽  
Element Analysis ◽  
Element Mesh

The implementation of inter-element model to simulate crack propagation by using finite element analysis with adaptive mesh is presented. An adaptive finite element mesh is applied to analyze two-dimension elastoplastic fracture during crack propagation. Displacement control approach and updated Lagrangean strategy are used to solve the non-linearity in geometry, material and boundary for plane stress crack problem. In the finite element analysis, remeshing process is based on stress error norm coupled with h-version mesh refinement to find an optimal mesh. The crack is modeled by splitting crack tip node and automatic remeshing calculated for each step of crack growth. Crack has been modeled to propagate through the inter-element in the mesh. The crack is free to propagates without predetermine path direction. Maximum principal normal stress criterion is used as the direction criteria. Several examples are presented to show the results of the implementation.

Short Crack Growth Model in a Particulate Composite Using Nonlinear Elastic Fracture Mechanics

2003 ◽  
Author(s):  
Ying Zhang ◽  
Tsuchin Chu ◽  
Ajay Mahajan
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Crack Growth ◽  
Particulate Composite ◽  
Initial Crack ◽  
Short Crack ◽  
Video Tape ◽  
J Integral ◽  
Elastic Fracture ◽  
Crack Growth Model

The fracture mechanics model for a long crack does not work very well with short-crack propagation when the initial crack length is less than 5.1 mm (0.2 inch). In order to investigate the short crack effect, a series of tests of particulate composite specimens with long and short cracks were performed and the results recorded on a video tape. This test data was analyzed to determine the fracture parameters. Two initial crack lengths, 2.5 mm (0.1 inches) and 7.6 mm (0.3 inches) were used in the crack propagation tests. Based on the principle of linear elastic fracture mechanics (LEFM), the stress intensity factor KI was obtained. The instantaneous time-dependent J-integral for 0.1 and 0.3 inch crack specimens was determined by the NEFM analytical approach. The crack growth behavior was also investigated in the form of J-integral resistance curves. The calculated J-integral was reversed to derive a new KI. The new KI was compared with the measured value obtained from LEFM analysis results to determine the feasibility of applying the linear fracture approach to the non-linear behavior of the material. The results showed that the KI computed from the J-integral increased by 24.5%, and was at the time prior to the peak load for the 0.1 inch crack. For the 0.3 inch crack, the acceptable range was from the onset of propagation to the 9% strain stage (yield strain for the material), where the increase of the new KI was within 15.6%.

Fatigue Crack Propagation Simulation of Rubber Shock Absorbers

2011 ◽  
Vol 415-417 ◽  
pp. 2298-2303
Author(s):  
Jing Yu Zhai ◽  
Ying Yang ◽  
Qing Kai Han
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Shock Absorber ◽  
Three Dimensional ◽  
Element Model ◽  
Initial Crack ◽  
Shock Absorbers ◽  
Element Method

Rubber shock absorbers are the key parts to isolate vibrations of the machinery and equipment. In this paper, a three dimensional finite element model of a rubber shock absorber is established; then the computation of three dimensional fatigue crack growth rates are discussed by using the nonlinear finite element method. The stress distribution which can determine the initial crack location and the possible risk surface under dynamic loads is obtained. The three dimensional crack growth is simulated by using finite element method and linear elastic fracture mechanics. A brittle fracture process of the rubber shock absorber along the dangerous surface is simulated by using the cohesive element of ABAQUS.

A finite element model on effects of impact load and cavitation on fatigue crack propagation in mechanical bileaflet aortic heart valve

2008 ◽  
Vol 222 (7) ◽  
pp. 1115-1125 ◽  
Author(s):  
H Mohammadi ◽  
R J Klassen ◽  
W-K Wan
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Length ◽  
Heart Valve ◽  
Heart Valves ◽  
Element Model ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Element Approach ◽  
The Impact

Pyrolytic carbon mechanical heart valves (MHVs) are widely used to replace dysfunctional and failed heart valves. As the human heart beats around 40 million times per year, fatigue is the prime mechanism of mechanical failure. In this study, a finite element approach is implemented to develop a model for fatigue analysis of MHVs due to the impact force between the leaflet and the stent and cavitation in the aortic position. A two-step method to predict crack propagation in the leaflets of MHVs has been developed. Stress intensity factors (SIFs) are computed at a small initiated crack located on the leaflet edge (the worst case) using the boundary element method (BEM). Static analysis of the crack is performed to analyse the stress distribution around the front crack zone when the crack is opened; this is followed by a dynamic crack analysis to consider crack propagation using the finite element approach. Two factors are taken into account in the calculation of the SIFs: first, the effect of microjet formation due to cavitation in the vicinity of leaflets, resulting in water hammer pressure; second, the effect of the impact force between the leaflet and the stent of the MHVs, both in the closing phase. The critical initial crack length, the SIFs, the water hammer pressure, and the maximum jet velocity due to cavitation have been calculated. With an initial crack length of 35 μm, the fatigue life of the heart valve is greater than 60 years (i.e. about 2.2×109 cycles) and, with an initial crack length of 170 μm, the fatigue life of the heart valve would be around 2.5 years (i.e. about 9.1×107 cycles). For an initial crack length greater than 170 μm, there is catastrophic failure and fatigue cracking no longer occurs. A finite element model of fatigue analysis using Patran command language (PCL custom code) in MSC software can be used to evaluate the useful lifespan of MHVs. Similar methodologies can be extended to other medical devices under cyclic loads.

Surface to Through-Wall Crack Transition Model for Circumferential Cracks in Pipes

2021 ◽  
Author(s):  
Do Jun Shim ◽  
Jeong-Soon Park ◽  
Robert Kurth ◽  
David L. Rudland
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Surface Crack ◽  
Outer Diameter ◽  
Transition Model ◽  
Finite Element Analyses ◽  
Transition Behavior ◽  
Final Surface ◽  
Proposed Model ◽  
Crack Transition

Abstract In the present paper, finite element analyses were performed to update and also extend the applicable ranges of the existing KI and COD solutions for non-idealized through-wall cracks. Then, a surface to through-wall crack transition model was proposed based on these solutions. The proposed model provides a criterion which determines when the final surface crack should transition to a through-wall crack. It also provides a criterion to determine the two crack lengths (at the inner and outer diameter surfaces) of the initial non-idealized through-wall crack. Furthermore, crack growth of non-idealized through-wall cracks can be simulated by using the proposed method. Finally, the proposed model was verified by demonstrating that it can well predict the surface to through-wall transition behavior when compared to the natural crack growth simulations.

Failure Investigation and Crack Propagation Analysis of LP Blade Steam Turbine 220 MW

2021 ◽  
Vol 876 ◽  
pp. 67-76
Author(s):  
Natalina Damanik ◽  
Hendery Dahlan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Crack Propagation ◽  
Steam Turbine ◽  
Initial Crack ◽  
Tearing Mode ◽  
Element Analysis ◽  
Root Area ◽  
The Finite Element Analysis ◽  
Blade Failure

The cracked blade in L-0, L-1 governor side, and L-1 generator side were found when A 220 MW low-pressure steam turbine was checked in the serious inspection. However, the crack population more dominant at L-1 Gen compared to L-0 Gov and L-1 Gov. Most of the cracks were located on 300-400 mm from the root of the blade span, and it did not associate with the pitting defect. In this study, the root cause of L-1 blade failure was investigated. There is three-stage of analyzing process, firstly capturing the airfoil and dimension of L-1—secondly, the material properties analysis, and finally stress analysis of L-1 by the finite element analysis software. L-1 is the blade with the chord length on the tip L-1 blade longer than root as 2.1% and the angle of an airfoil from root to tip twisted as 24 degrees. The type of material did not look precisely similar to AISI 422 because its hardness-strength is lower than AISI 422 as 5.1%. The finite element analysis shows that there was a symptom of the imprecise shroud gap that promoted maximum stress at 300-400 mm from the root area of the L-1 blade span. Moreover, a lack of hardness-strength material cannot accommodate the excessive movement of the blade and promoted the initial crack of L-1. A crack length blade as 16 mm shows a lower number of cyclic (Nf) to failure tremendously compared to standard blades such as 32,367 of the number cyclic for regular blade and 42.6 for the crack blade. Increasing 2 mm of initial crack will decrease significantly the number of cyclic Nf of the blade. It was tearing mode crack propagation of L-1 results a significant stress intensity factor compared to other modes, especially at 16 mm length of the crack.

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