Evaluation of Local Mechanical Properties of High Strength Steels by Indentation Method

Komori, Takafumi

doi:10.1299/kikaia.78.646

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…Many studies using the indentation method have been reported (Nakashima et al, 2016;Yonezu et al, 2006;Sakaue et al, 2012). The local stress-strain relationship can be evaluated using the multi-indentation method, which is performed by indentation with multiple apex angles (Ozeki et al, 2014;Komori et al, 2012). However, numerous indentation studies have reported an increase in the hardness with decreasing depth of penetration, which is known as the indentation size effect.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the indentation size effect based on measurement of the geometrically necessary dislocation density by electron backscatter diffraction

Hasunuma

Miyazaki

Shimada

et al. 2018

Mechanical Engineering Journal

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In this study, we investigated the mechanism of the indentation size effect based on measurement of the geometrically necessary (GN) dislocation density. The GN dislocation density was measured around impressions by electron backscatter diffraction (EBSD). Indentation tests were performed for two types of single crystal Ni with different crystal orientations: (001) and (111). Difference between (111) and (001) orientation are small in the relationship of the hardness and the penetration depth. However, the deformation behavior and distribution of the GN dislocation density are different for the (001) and (111) orientations. For the (111) orientation, the GN dislocation density increases with decreasing hardness. However, the GN dislocation density for the (001) orientation increases with increasing hardness. The mechanism of the indentation size effect for the (001) orientation can be attributed to the increase of the GN dislocation density. In addition, we investigated the effect of the indenter shape on the indentation size effect. Indentation tests were performed with different apex angles. The hardness using an indenter with a large apex angle is smaller than that using an indenter with a small apex angle. The GN dislocation density increases with decreasing apex angle. The mechanism of the indentation size effect for the apex angle can be attributed to the increase of the GN dislocation density. We prepared another indenter with a dull tip. The hardness using the dull indenter is larger than that using the sharp indenter. The GN dislocation density distribution changes with the indenter sharpness but the GN dislocation density is similar. For the dull indenter, variation of the GN dislocation density has a smaller effect on the indentation size effect than the increase of the resistance because of the different indenter shape.

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Section: Introductionmentioning

confidence: 99%

Investigation of the indentation size effect based on measurement of the geometrically necessary dislocation density by electron backscatter diffraction

Hasunuma

Miyazaki

Shimada

et al. 2018

Mechanical Engineering Journal

View full text Add to dashboard Cite

show abstract

“…Many studies using the indentation method have been reported (Nakashima et al, 2016;Yonedu et al, 2006;Sakaue et al, 2012). The local stress-strain relationship can be evaluated using the multi-indentation method, which is performed by indentation with multiple apex angles (Ozeki et al, 2014;Komori et al, 2012). However, numerous indentation studies have reported an increase in the hardness with decreasing penetration depth, which is known as the indentation size effect.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the mechanism of the indentation size effect for titanium

Hasunuma

Miyazaki

Ogawa

2019

Mechanical Engineering Journal

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In this study, we investigated the mechanism of the indentation size effect for Ti, whose crystal structure is hexagonal close-packed. Indentation tests were performed for two types of single-crystal Ti with different crystal orientations: (0001) and (11 2 _ 0). Indentation tests were also performed with different indenter directions. The hardness depends on the crystal orientation and indenter direction because Ti has large anisotropy. The shape of the impression also changes with the crystal orientation and indenter direction. The hardness increases with decreasing penetration depth for the (0001) and (112 _ 0) orientations, so the indentation size effect occurs. For the (0001) orientation, a sudden rapid increase in displacement occurs during indentation tests owing to twinning. This sudden rapid increase in displacement causes a rapid decrease in the hardness. Electron backscatter diffraction was performed around the impressions to measure the geometrically necessary (GN) dislocation density. The GN dislocation density increases with decreasing penetration depth for the (0001) and (112 _ 0) orientations. This trend corresponds to strain gradient theory. The reason for the indentation size effect in Ti is the increase in the GN dislocation density. For the (0001) orientation, the indentation size effect also can be attributed to twinning. Considering both our previous study and this study, the experimental results correspond to strain gradient theory in many cases.

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Evaluation of Local Mechanical Properties of High Strength Steels by Indentation Method

Cited by 2 publications

References 2 publications

Investigation of the indentation size effect based on measurement of the geometrically necessary dislocation density by electron backscatter diffraction

Investigation of the indentation size effect based on measurement of the geometrically necessary dislocation density by electron backscatter diffraction

Investigation of the mechanism of the indentation size effect for titanium

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