Stress wave superposition effect and crack initiation mechanism between two adjacent boreholes

2021 ◽  
Vol 138 ◽  
pp. 104622
Author(s):  
Chenxi Ding ◽  
Renshu Yang ◽  
Chun Feng
Keyword(s):  
Crack Initiation ◽  
Stress Wave ◽  
Initiation Mechanism ◽  
Wave Superposition ◽  
Superposition Effect

Very High Cycle Fatigue Behavior and Life Prediction of a Low Strength Weld Metal at Moderate Temperature

2011 ◽  
Author(s):  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan ◽  
Zhengdong Wang
Keyword(s):  
Crack Initiation ◽  
Weld Metal ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Dissimilar Welding ◽  
Initiation Mechanism ◽  
Metallic Inclusions ◽  
Low Strength ◽  
Very High

The fatigue properties of a low strength weld metal in a dissimilar welding joint in high cycle and very high cycle regimes were investigated by fully reversed axial tests in air at room temperature and 370°C. A clear duplex S-N curve existed as a result of the transition of fatigue failure mode from surface-induced failure to internal-induced failure at 370°C, while the S-N curve was continuously decreased at room temperature. A new model was successfully proposed to predict fatigue life, and interpret the crack initiation modes transition from surface inclusion to interior inclusion. It was concluded that cracks were initiated by competition among non-metallic inclusions, welding pores and discontinuous microstructures in high cycle regime. While in the very high cycle regime, non-metallic inclusions were the dominant crack initiation mechanism which depended on stress level, inclusion size as well as inclusion depth.

scholarly journals 3D characterization of the fracture mechanisms of a Fe-rich Al-Si-Cu alloy

2018 ◽  
Vol 165 ◽  
pp. 04006
Author(s):  
Angelika Brueckner-Foit ◽  
Inigo Bacaicoa ◽  
Martin Luetje ◽  
Marcel Wicke ◽  
Andreas Geisert ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Fracture Mechanisms ◽  
Crack Advance ◽  
Micro Computed Tomography ◽  
Initiation Mechanism ◽  
Initiation Phase ◽  
Β Phase ◽  
Cu Alloy

The effect of the defect size and morphology on the fatigue damage evolution was analysed in a recycled Al-Si-Cu alloy by micro-computed tomography and scanning electron microscopy. Fatigue tests were performed and the different crack initiation scenarios were characterized and classified. The interaction between shrinkage and gas pores was the key crack initiation mechanism and the ß-Al5FeSi particles did not play any role in the crack initiation phase. However, crack path analysis indicated that there is a certain amount of crack advance by brittle fracture of the β-phase particles. This is in accordance with the findings of tensile tests in which the ductility depended strongly on the iron content.

scholarly journals Fatigue life assessment regarding different influences on the HCF/VHCF behavior of a martensitic steel

2018 ◽  
Vol 165 ◽  
pp. 20004
Author(s):  
Igor Milošević ◽  
Benjamin Seisenbacher ◽  
Gerhard Winter ◽  
Florian Grün ◽  
Martin Kober
Keyword(s):  
Crack Initiation ◽  
Life Assessment ◽  
Special Treatment ◽  
Initiation Mechanism ◽  
Component Size ◽  
Fatigue Life Assessment ◽  
Fatigue Data ◽  
Gradient Based ◽  
Actual Material ◽  
Cycles To Failure

Modern applications require a special treatment when the conventional specimen size is much larger than the component size. Additional to that, high sophisticated materials are used for highly loaded components. Often the conventional fatigue limit is exceeded and loads are applied in the VHCF regime. Focus was put on the lifetime calculation and the implementation of investigated fatigue data of a X5CrNiCuNb-16-4 type steel. Two specimen geometries with diameters D7.5=7.5 mm and D2.5=2.5 mm were tested at R=-1, at room temperature and up to 109 cycles to failure. The application of different software tools (FEMFAT, fe-safe) showed several issues based on the current results. Results showed a change of crack initiation mechanism to subsurface crack initiation at approx. 2x106 cycles to failure. The gradient based correction of the reference fatigue data showed a good applicability up to 2x106 cylces. The application of fe-safe allows the flexible modification of S/N parameters over the whole cycle range. The usage of the actual material configuration introduced several important questions regarding the fatigue data and the implementation into lifetime calculation tools.

scholarly journals Control of fatigue failure mechanisms in multilayer coatings by varying the architectural parameters of an intermetallic interlayer

2021 ◽  
Author(s):  
Songsong Lu ◽  
Richard Cook ◽  
Yi Zhang ◽  
Philippa Reed
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
Intermetallic Layer ◽  
Failure Mechanisms ◽  
Multilayer Coatings ◽  
Coating System ◽  
Fatigue Improvement ◽  
Initiation Mechanism ◽  
Experimental Characterisation ◽  
Surface Crack Initiation

A multilayer overlay coating system containing an intermediate intermetallic layer (designated 2IML) is an architecture expected to show good fatigue resistance. Experimental characterisation and modelling simulations were carried out to classify the different crack initiation mechanisms occurring during fatigue of this coating system and to reveal how changes in the layer architecture lead to fatigue improvement. Fatigue improvement is achieved by decreasing the IML-Top layer thickness due to the increased surface crack initiation resistance. However subsurface initiation mechanisms inhibit the improvement (dominated by surface initiation mechanism) achieved by locating the IML-Top layer closer to the top surface.

High Cycle Fatigue Properties of Multi-Directionally Forged Commercial Purity Grade 2 Ti Plate

2018 ◽  
Vol 916 ◽  
pp. 166-169
Author(s):  
Ilhamdi ◽  
Toshifumi Kakiuchi ◽  
Hiromi Miura ◽  
Yoshihiko Uematsu
Keyword(s):  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Pure Titanium ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Commercially Pure Titanium ◽  
Cycle Fatigue ◽  
Subsurface Crack ◽  
Initiation Mechanism ◽  
Fish Eye

Tension-tension fatigue tests were conducted using ultrafine-grained commercially pure Titanium (Ti) plates fabricated by multi-directional forging (MDFing). The MDFed pure Ti plates with the thickness of 1 mm were developed aiming at dental implant application. The fatigue properties of MDFed pure Ti plates were superior to those of the conventional rolled pure Ti plates. The higher fatigue strengths in MDFed plates could be attributed to the much finer grains evolved by MDFing. Fatigue crack initiated from specimen surface, when number of cycles to failure was shorter than 106 cycles. In the high cycle fatigue (HCF) region, however, subsurface crack initiation with typical fish-eye feature was recognized in the MDFed pure Ti plate in spite of the thin thickness. Fractographic analyses revealed that no inclusion existed at the center of fish-eye. The subsurface crack initiation mechanism could be related to the inhomogeneity of microstructure with some coarse grains in the inner part of the plate.

Revealing the fatigue crack initiation mechanism of a TiB2-reinforced steel matrix composite

2020 ◽  
Vol 130 ◽  
pp. 105276 ◽  
Author(s):  
Ronghua Chen ◽  
Bochuan Li ◽  
Yizhuang Li ◽  
Zhicheng Liu ◽  
Xiangyun Long ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Matrix Composite ◽  
Fatigue Crack Initiation ◽  
Steel Matrix ◽  
Initiation Mechanism ◽  
Reinforced Steel ◽  
Steel Matrix Composite

scholarly journals Effect of Rise and Fall Time on Dwell Fatigue Behavior of a High Strength Titanium Alloy

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 914 ◽  
Author(s):  
Qingyuan Song ◽  
Yanqing Li ◽  
Lei Wang ◽  
Ruxu Huang ◽  
Chengqi Sun
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Cross Section ◽  
Fatigue Behavior ◽  
Circular Cross Section ◽  
High Strength ◽  
Initiation Mechanism ◽  
Fall Time ◽  
Dwell Fatigue

Frequency is an important factor influencing the fatigue behavior. Regarding to the dwell fatigue, it corresponds to the effect of rise and fall time, which is also an important issue especially for the safety evaluation of structure parts under dwell fatigue loading, such as the engines of aircrafts and the pressure hulls of deep-sea submersibles. In this paper, the effect of rise and fall time (2 s, 20 s, 110 s, and 200 s) on the dwell fatigue behavior is investigated for a high strength titanium alloy Ti-6Al-2Sn-2Zr-3Mo-X with basket-weave microstructure. It is shown that the dwell fatigue life decreases with increasing the rise and fall time, which could be correlated by a linear relation in log–log scale for both the specimen with circular cross section and the specimen with square cross section. The rise and fall time has no influence on the crack initiation mechanism by the scanning electron microscope observation. The cracks initiate from the specimen surface and all the fracture surfaces present multiple crack initiation sites. Moreover, the facet characteristic is observed at some crack initiation sites for both the conventional fatigue and dwell fatigue tests. The paper also indicates that the dwell period of the peak stress reduces the fatigue life and the dwell fatigue life seems to be longer for the specimen with circular cross section than that of the specimen with square cross section.

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