PSI - Issue 36

V. Kharchenko et al. / Procedia Structural Integrity 36 (2022) 277–283 A.V. Sereda et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Equation (Oliver and Pharr (1992)) was used to eliminate the elastic strain effect of the indentation depth measurement on the imprint depth measurement (Fig. 2). ( ) r t h h h  = − − (2)

Fig. 2. Scheme of the determination of the yield limit via instrumented indentation test method.

To determine the strength limit via instrumented indentation test method Rm indent, the procedure developed at the Institute has been used. It is based on the correlation dependence of the yield limit defined for uniaxial tension Rm and proportionality factor of plastic indentation а: (3) where k1σ and k2σ are the coefficients that are experimentally determined using setup UTM - 20HT; а is a tangent of an angle of inclination for the indentation diagram in coordinates «Fmax – hp» (Fig. 3). m 2 indent R k a k    =  + 1

Fig. 3. Scheme of the strength limit determination via instrumented indentation method . The proportionality factor of plastic indentation α was determined by the diagram approximation « F max – h p » from the formula:

max p F a h = 

(4)

or using the indentation data: