Microstructure and Fatigue Fracture of Spot Welded TRIP800 Steel

2015 ◽  
Vol 789-790 ◽  
pp. 15-19 ◽  
Author(s):  
Hua Wu ◽  
Bin Zhao ◽  
Hua Gao ◽  
Zhen Bo Zhao ◽  
Cheng Liu
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Crack ◽  
Fatigue Strength ◽  
Cleavage Fracture ◽  
Heat Affected Zone ◽  
Spot Welding ◽  
Fatigue Property ◽  
Transformation Induced Plasticity ◽  
Scanning Electron

The fatigue property of a TRIP (transformation induced plasticity) steel after resistance spot welding (RSW) is investigated. It is found that the fatigue strength of the spot weld is only 8.9% of the original TRIP800 steel. This is a result of microstructure mismatch in heat affected zone (HAZ) due to different cooling rates during RSW. A maximum variation of about 220HV microhardness is observed at different areas from the relatively narrow HAZ. The fatigue degradation is attributed to the inhomogeneous distributions of microstructure and microhardness at HAZ and its adjacent zones. The fatigue crack initiated between HAZ and BM is a cleavage fracture as confirmed by scanning electron microscopy (SEM) observation.

Fatigue Life and Stress Retro Estimation of 30CrMnSiA in Laboratory Environment

2020 ◽  
Vol 984 ◽  
pp. 3-10
Author(s):  
Wei Fang Zhang ◽  
Xing Yu Gao ◽  
Xiao Peng Liu ◽  
Xue Rong Liu
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Striation ◽  
Experimental Conditions ◽  
Laboratory Environment ◽  
Fatigue Stress ◽  
Paris Law ◽  
Scanning Electron

The fatigue life and fatigue stress of 30CrMnSiA material are studied by fracture retro estimation under experimental conditions. With the help of Scanning electron microscopy (SEM), fatigue crack can be observed. By Paris law, the fatigue life and fatigue stress of 30CrMnSiA material can be estimated by fatigue striation under the experimental environment. The method is simple and feasible, and the relative error is lower.

scholarly journals Influence of Indentation on the Fatigue Strength of Carbonitrided Plain Steel

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Jiewei Gao ◽  
Guangze Dai ◽  
Junwen Zhao ◽  
Hengkui Li ◽  
Lei Xu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Compound Layer ◽  
Indentation Size ◽  
Fracture Surfaces ◽  
Significant Difference ◽  
Scanning Electron

To study the influence of indentation on the fatigue strength of untreated and carbonitrided specimens of S38C steel, the fatigue limit of specimens with and without indentations was tested. Fracture surfaces were observed using scanning electron microscopy (SEM). The results show that the fatigue strength of the untreated specimen decreases with increasing dimension of indentation, without significant difference compared to the predicted results. Compared to the fatigue limit of the untreated specimen, those of the carbonitrided specimen and the carbonitrided specimen whose compound layer was polished were improved by 12% and 40%, respectively. The fatigue strength of the carbonitrided specimen decreased sharply with increasing indentation size because of the presence of microcracks in the compound layer. When the compound layer was removed, the fatigue limit was observed to be less sensitive to indentation than that of the carbonitrided specimen.

Technique for Visualizing Subgrain Structure at Fatigue Crack Tips by Ion Etching and Scanning Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 86-87 ◽  
Author(s):  
G. G. Shaw ◽  
D. K. Benson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Crack ◽  
Single Crystal ◽  
Fatigue Cracks ◽  
Subgrain Structure ◽  
Ion Etching ◽  
Etch Patterns ◽  
Crack Tips ◽  
Scanning Electron

The subgrain structure in ram size areas adjacent to fatigue cracks has been observed by ion etching followed by scanning electron microscopy. The etch patterns have been definitely identified as subgrain structure resulting from the fatigue strains by direct comparison with channelling electron microscopy. The technique is described as it was applied to a single crystal of aluminum which had been fatigued in Stage I by reversed bending.A 5 mm long section of crystal containing the crack was cut from the fatigue sample by spark machining. This section was sliced into pieces 2 to 3 mm thick, and a slice selected with the crack tip close to its center. The selected slice was placed in a shallow aluminum cup about 2 cm in diameter.

scholarly journals Low Cycle Fatigue Properties of Sc-Modified AA2519-T62 Extrusion

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 220 ◽  
Author(s):  
Robert Kosturek ◽  
Lucjan Śnieżek ◽  
Janusz Torzewski ◽  
Marcin Wachowski
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Strength ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Total Strain ◽  
Fatigue Properties ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Scanning Electron

This investigation presents the results of research on low cycle fatigue properties of Sc-modified AA2519-T62 extrusion. The basic mechanical properties of the investigated alloy have been established in the tensile test. The low cycle fatigue testing has been performed on five different levels of total strain amplitude: 0.4%; 0.5%; 0.6%; 0.7% and 0.8% with cycle asymmetry coefficient R = 0.1. For each level of total strain amplitude, the graphs of variations in stress amplitude and plastic strain amplitude in the number of cycles have been presented. The obtained results allowed to establish Ramberg-Osgood and Manson-Coffin-Basquin relationships. The established values of the cyclic strength coefficient and cyclic strain hardening exponent equal to k’ = 1518.1 MPa and n’ = 0.1702. Based on the Manscon-Coffin-Basquin equation, the values of the following parameters have been established: the fatigue strength coefficient σ’f = 1489.8 MPa, the fatigue strength exponent b = −0.157, the fatigue ductility coefficient ε’f = 0.4931 and the fatigue ductility exponent c = −1.01. The fatigue surfaces of samples tested on 0.4%, 0.6% and 0.8% of total strain amplitude have been subjected to scanning electron microscopy observations. The scanning electron microscopy observations of the fatigue surfaces revealed the presence of cracks in striations in the surrounding area with a high concentration of precipitates. It has been observed that larger Al2Cu precipitates exhibit a higher tendency to fracture than smaller precipitates having a higher concentration of scandium and zirconium.

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