scholarly journals Processing of videos of the fatigue cracks propagation in the rotor blades of the helicopter

2019 ◽  
Vol 684 ◽  
pp. 012004
Author(s):  
V Yu Kurokhtin
Keyword(s):  
Fatigue Cracks ◽  
Rotor Blades ◽  
Cracks Propagation

Hydrogen Aggressive Media Impact on Cycling Durability of Structure Components

2016 ◽  
Vol 844 ◽  
pp. 27-30 ◽  
Author(s):  
Daniel L. Kishlakov ◽  
Pavel V. Tarakanov ◽  
Georgy V. Shashurin ◽  
Yury V. Berchun
Keyword(s):  
Hydrogen Embrittlement ◽  
Damage Accumulation ◽  
Cyclic Load ◽  
Fatigue Cracks ◽  
Environmental Concentration ◽  
Media Impact ◽  
Aggressive Environment ◽  
Mathematical Rule ◽  
Cycling Frequency ◽  
Cracks Propagation

To develop modern CAE systems for durable and reliable structure components design, mathematical modeling of environmentally assisted metal cracking becomes very important. For structure components exploited in aggressive environment and under cyclic load, it is a problem of today. Besides, mathematical rule of damage accumulation of different causes (for instance, hydrogen media impact and cycling) is rarely used in CAE systems, but if such rule was used, crack propagation simulation considering several damage causes would be possible.Environmentally assisted metal cracking model (developed earlier by authors) is described in the paper. This model considers cyclic load and hydrogen embrittlement, the most important characteristics of which are hydrogen environmental concentration and load frequency respectively.The authors’ model successfully predicts effect, known from certain experimental data, that the greater is the frequency, the less hydrogen embrittlement affects fatigue cracks propagation and, vice-versa, that there are certain boundaries of cycling frequency for which embrittlement effect is comparably big.Such boundaries of frequency were numerically estimated by means of the presented model. Plots showing dependency of the component’s life on different defect and loading features are shown.

Fatigue Behaviour of Ti-6Al-4V Alloy in Vacuum and at Low Temperature

2008 ◽  
Vol 41-42 ◽  
pp. 83-90 ◽  
Author(s):  
J.H. Zuo ◽  
Z.G. Wang ◽  
En Hou Han
Keyword(s):  
Low Temperature ◽  
Fatigue Fracture ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Sample Surface ◽  
Fatigue Behaviour ◽  
Fatigue Properties ◽  
Fatigue Fracture Surface ◽  
Cracks Propagation

Investigations have been conducted on the fatigue behavior of Ti-6Al-4V alloy with the bimodal microstructure in air at room temperature, in vacuum at room temperature and in vacuum at low temperature (100K), respectively. The results show that the fatigue life of this alloy is longer in vacuum and/or at low temperature than that in air at room temperature. The combination of vacuum and low temperature can much improve the fatigue properties of this alloy because of their purifying effect on fatigue cracks propagation. SEM observation of fatigue fracture surface indicates that all the fatigue cracks initiate in the sample surface when Nf ≦106 cycles. The above three testing conditions lead to different modes of fatigue crack propagation and therefore much different morphology of fatigue fracture.

scholarly journals To the modelling of the fatigue cracks propagation in a thin isotropic plates under biaxial asymmetric tension-compression

2019 ◽  
pp. 154-157
Author(s):  
Alla Plashchynska
Keyword(s):  
Circular Hole ◽  
Cyclic Load ◽  
Damage Mechanics ◽  
Fatigue Cracks ◽  
Equivalent Stress ◽  
Plane Stress State ◽  
Isotropic Plates ◽  
Cracks Propagation ◽  
Mechanics Concepts ◽  
Joint Consideration

The modelling of the fatigue fracture process of the thin isotropic infinite plates with cracks under external biaxial asymmetric cyclic loading is considered. The solution of the problem is based on the joint consideration of the fracture mechanics and continuous damage mechanics concepts and using two types of equivalent stress criteria’s. The first one reduces an asymmetrical cyclic load to the equivalent symmetric cyclic load in time of the rupture. The second one reduces a plane stress state in the vicinity of the top crack to a single-axial one. The obtained system of equations of the model a relatively equivalent stress intensity factor allows us to determine the duration of the incubation stage and the rate of fatigue crack propagation in plates with different stress concentrators. The calculated dependences of the crack length, which extends from the circular hole, from the number of load cycles in the infinite aluminum plate with a circular hole at the variation of the parameters of the asymmetrical cycle and the coefficient of the biaxiality loading are constructed.

Fatigue Multi-Cracks Growths in Plates Using J-Integral Approach with a Developed Home FEM Software

2013 ◽  
Vol 560 ◽  
pp. 61-70
Author(s):  
Hossein Hosseini-Toudeshky ◽  
Bijan Mohammadi ◽  
Pooya Saniei
Keyword(s):  
Crack Propagation ◽  
Fatigue Cracks ◽  
Propagation Path ◽  
Integral Approach ◽  
Multiple Cracks ◽  
J Integral ◽  
Crack Propagation Path ◽  
Cracks Propagation ◽  
Complex Boundaries ◽  
Refinement Algorithm

In this paper multiple fatigue cracks propagation are simulated in two-dimensional plates. Since re-meshing the cracked bodies in each increment of crack extension is a time-consuming and complicated procedure, numerical simulation of mixed-mode crack propagation with FEM is a difficulty. For this purpose, a FEM software is programmed and mesh refinement in each increment of crack is performed by Delaunay Refinement Algorithm. Using different refinement methods, complex boundaries such as multiple cracks and discontinuities which are closed together are easily refined by this algorithm. Crack propagation path is predicted using domain form of J-integral. Modified tensile stress (MTS) criterion is used to predict the crack propagation path in each increment. Different numerical examples illustrate the validation and reliability of present software.

scholarly journals Fracture failure analysis of the pump shaft

2020 ◽  
Vol 213 ◽  
pp. 03010
Author(s):  
Chengjun Jiang ◽  
Kai Tao ◽  
Jifeng Wang ◽  
Wei Wang
Keyword(s):  
Fatigue Cracks ◽  
Composition Analysis ◽  
Metallographic Examination ◽  
Fracture Failure ◽  
Silicate Inclusions ◽  
Macroscopic Observation ◽  
Pump Shaft ◽  
Cracks Propagation ◽  
Fracture Section ◽  
Section Analysis

The failure reasons of the circulating pump shaft in the upper section of the quench tower were analyzed by means of chemical composition analysis, macroscopic observation, metallographic examination and fracture section analysis. The analysis result shows that the calcium-silicate inclusions in the surface of the pump shaft cause the microcracks and the parallel fatigue sources, which leads to the fatigue cracks propagation under alternating load and finally the shaft is fatigue fractured.

Towards High Temperature Electronic Modules in which all Components would be attached using Silver Sintering

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000216-000225
Author(s):  
Thomas GEOFFROY ◽  
Jean-Christophe RIOU ◽  
Yves BIENVENU ◽  
Corinne PONS ◽  
Sylvain MEILLE ◽  
...  
Keyword(s):  
Fatigue Cracks ◽  
Passive Components ◽  
Thermomechanical Stress ◽  
Die Attach ◽  
Ceramic Capacitors ◽  
Cracks Propagation ◽  
Silver Sintering ◽  
Porous Microstructures ◽  
The Impact ◽  
Sintering Processes

Abstract This article points out the fact that conventional low temperature silver sintering processes do not seem to satisfy the needs for reliability when they are used to assemble passive components (such as multilayers ceramic capacitors) in electronic modules undergoing wide amplitude thermal cycles (−65°C / +200°C). These processes indeed lead to very porous microstructures of silver which favors rapid fatigue cracks propagation [1], [2], [3]. Even if these types of porous microstructures may be suitable for die attach, tests presented in this paper show they cannot resist to the levels of thermomechanical stress reached in attachment joints of multilayers ceramic capacitors (MLCCs). To find process parameters minimizing porosity in attachment joints of capacitors, measurements of the shrinkage of silver during sintering have been carried out by dilatometry. Then the impact of densification of attachment joints on the ageing behavior and on the mechanical behavior of assemblies has been assessed in this study.

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