Other

National Institute for Materials Science

Japan As Represented by Director General of National Research Institute for Metals

Saburo Matsuoka

Kensuke Miyahara

Nobuo Nagashima

Kaneaki Tsuzaki

Yuji Kimura

Etsuo Takeuchi

Tatsuaki Sawai

Takayuki Abe

Hisashi Hirukawa

An ultra micro indentation testing apparatus comprises: a lever stand provided with a center lever having a silicon probe and a diamond indenter disposed therein; a moving mechanism for moving the lever stand in a triaxial direction; in indentation mechanism for pushing the diamond indenter in a sample; a displacement gage for measuring a displacement of the silicon probe or the diamond indenter; and an optical picture device for positioning the silicon probe or the diamond indenter and observing the surface of the sample. The apparatus has, in combination, a hardness measuring function based on the measurement of the force and depth of the diamond indenter pushed in the surface of the sample, an atomic force microscopic function of acquiring the shape of the surface of the sample based on a displacement of the diamond indenter or the silicon probe, and an optical microscopic function of observing the surface of the sample by the optical picture device. Furthermore, the testing apparatus is equipped with both the function of measuring the hardness of the surface of material in a ultra micro region and the surface observing function with high accuracy.

Ultra micro indentation testing apparatus

The present invention provides a method of designing a high fatigue strength in high tensile strength steel, comprising: obtaining values of tensile strength &sgr; (unit thereof is MPa) and Vickers hardness Hv of the steel; measuring a flaw area of an inclusion, when a fracture origin is located only at a surface of the steel; and estimating, in designing the high fatigue strength steel, that a fatigue limit &sgr; (unit thereof is MPa) of the steel satisfies either &sgr; &gE;0.5 &sgr; or &sgr; &gE;1.6 Hv, when a square root of the flaw area, (area) (unit thereof is m), contained in the steel is no larger than 45.8/&sgr; or 4.47/Hv . According to the present invention, a method of evaluating high fatigue strength in high tensile strength steel, in which method a relationship between a flaw dimension (area) of ODA and the fatigue strength is considered, and a high fatigue strength material can be provided.

Method of evaluating high fatigue strength material in high tensile strength steel and creation of high fatigue strength material

A testing method is provided for determining the hardness of a micro region, using indentation curves indicating relations between observed penetration depths and indenting forces when an arbitrary shaped indenter is pushed into standard samples of plural types. The method involves (1) measuring relations between observed penetration depths and indenting forces when the arbitrary shaped indenter is pushed into standard samples of plural types, to prepare the indentation curves, (2) determining a reference function indicative of macro hardness, by standardizing the relations between the indenting forces and macro hardness at the same penetration depth as an index, for the indentation curves of the standard samples of plural types, (3) measuring a relation between the penetration depth and indenting force of an arbitrary sample, and (4) determining the hardness of a micro region from the measured value in step (3) according to the reference function as determined in step (2).

Method of testing hardness of micro region

Growing community of inventors

Ibaraki, Japan

Saburo Matsuoka