scholarly journals A model of energy dissipation at fatigue crack tip in metals

2019 ◽  
Vol 13 (48) ◽  
pp. 451-458
Author(s):  
Aleksei Vshivkov ◽  
Oleg Plekhov ◽  
Anastasiia Iziumova ◽  
Balasubramaniam Venkatraman
Keyword(s):  
Fatigue Crack ◽  
Energy Dissipation ◽  
Crack Tip

scholarly journals Peculiarities of energy dissipation at a fatigue crack tip in metals

2016 ◽  
Author(s):  
A. Iziumova ◽  
A. Vshivkov ◽  
A. Prokhorov ◽  
A. Kostina ◽  
O. Plekhov
Keyword(s):  
Fatigue Crack ◽  
Energy Dissipation ◽  
Crack Tip

scholarly journals An dissipated energy based analysis of fatigue crack propagation law

2019 ◽  
Vol 300 ◽  
pp. 11009
Author(s):  
Aleksei Vshivkov ◽  
Anastasiia Iziumova ◽  
Rustam Yarullin ◽  
Valery Shlyannikov ◽  
Oleg Plekhov
Keyword(s):  
Heat Flux ◽  
Fatigue Crack ◽  
Energy Dissipation ◽  
Cyclic Loading ◽  
Biaxial Loading ◽  
Crack Tip ◽  
Heat Flux Sensor ◽  
Dissipated Energy ◽  
Contact Heat ◽  
Propagation Law

The experimental study of heat flux evolution at the fatigue crack tip during biaxial loading was carry out in this work. The plane samples of stainless steel AISI 304 with thick of 3 mm were weakened by notch to initiate fatigue crack at the centre of samples. A contact heat flux sensor based on the Seebeck effect was used to monitor the dissipated thermal energy. During tests the samples were subjected to cyclic loading of 5 Hz with constant stress amplitude and different biaxial parameter. The experimental results confirm the previous conclusions of authors about two regime of energy dissipation at fatigue crack tip. The curve of the dissipated energy can be divided in two stages. In the second stage is characterized by classical linear relation between crack rate and energy dissipation. In the first stage the crack rate is proportional to the multiplication of the power of heat flux by crack length. The energy dissipation does not depend on the biaxial parameter during cyclic loading.

scholarly journals Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 4: sporadic fatigue crack propagation

2020 ◽  
Vol 92 (9) ◽  
pp. 1521-1536
Author(s):  
Clive Bucknall ◽  
Volker Altstädt ◽  
Dietmar Auhl ◽  
Paul Buckley ◽  
Dirk Dijkstra ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
High Molecular Weight ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Individual Growth ◽  
Paris Equation ◽  
Number Of Cycles ◽  
Ultra High Molecular Weight

AbstractFatigue tests were carried out on compression mouldings supplied by a leading polymer manufacturer. They were made from three batches of ultra-high molecular weight polyethylene (UHMWPE) with weight-average relative molar masses, ${\overline{M}}_{\mathrm{W}}$, of about 0.6 × 106, 5 × 106 and 9 × 106. In 10 mm thick compact tension specimens, crack propagation was so erratic that it was impossible to follow standard procedure, where crack-tip stress intensity amplitude, ΔK, is raised incrementally, and the resulting crack propagation rate, da/dN, increases, following the Paris equation, where a is crack length and N is number of cycles. Instead, most of the tests were conducted at fixed high values of ΔK. Typically, da/dN then started at a high level, but decreased irregularly during the test. Micrographs of fracture surfaces showed that crack propagation was sporadic in these specimens. In one test, at ΔK = 2.3 MPa m0.5, there were crack-arrest marks at intervals Δa of about 2 μm, while the number of cycles between individual growth steps increased from 1 to more than 1000 and the fracture surface showed increasing evidence of plastic deformation. It is concluded that sporadic crack propagation was caused by energy-dissipating crazing, which was initiated close to the crack tip under plane strain conditions in mouldings that were not fully consolidated. By contrast, fatigue crack propagation in 4 mm thick specimens followed the Paris equation approximately. The results from all four reports on this project are reviewed, and the possibility of using fatigue testing as a quality assurance procedure for melt-processed UHMWPE is discussed.

scholarly journals Study on the Influence of the Gurson–Tvergaard–Needleman Damage Model on the Fatigue Crack Growth Rate

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1183
Author(s):  
Edmundo R. Sérgio ◽  
Fernando V. Antunes ◽  
Diogo M. Neto ◽  
Micael F. Borges
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Plastic Strain ◽  
Crack Growth ◽  
Damage Model ◽  
Crack Tip ◽  
Strength Parameter ◽  
Stress Intensity Factor Range

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

Finite Element Simulation of Stable Fatigue Crack Growth Using Critical CTOD Determined by Preliminary Finite Element Analysis

2014 ◽  
Vol 891-892 ◽  
pp. 1675-1680
Author(s):  
Seok Jae Chu ◽  
Cong Hao Liu
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Finite Element Simulation ◽  
Crack Growth ◽  
Crack Tip ◽  
Stress Intensity Factor Range ◽  
Crack Tip Opening Displacement ◽  
Element Analysis ◽  
Element Simulation

Finite element simulation of stable fatigue crack growth using critical crack tip opening displacement (CTOD) was done. In the preliminary finite element simulation without crack growth, the critical CTOD was determined by monitoring the ratio between the displacement increments at the nodes above the crack tip and behind the crack tip in the neighborhood of the crack tip. The critical CTOD was determined as the vertical displacement at the node on the crack surface just behind the crack tip at the maximum ratio. In the main finite element simulation with crack growth, the crack growth rate with respect to the effective stress intensity factor range considering crack closure yielded more consistent result. The exponents m in the Paris law were determined.

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