Papers by Keyword: Hardness Testing

Abstract: The composites sample of Zinc Ferrite (Zn_xFe_3-xO₄) were prepared by mixing zinc oxide (ZnO) and iron oxide (Fe₂O₃) via different stoichiometry (ratio) with Zn_xFe_3-xO₄, for x= 0,0.2,0.4,0.6,0.8 and sintering temperature at 1000 °C, 1100 °C,1200 °C for six hours. The phase compositions of the synthesized Zinc Ferrite (ZF) were verified using X-ray Diffraction (XRD), hardness testing using hardness Vickers, density and thermal conductivity for composite was studied. The result shows the sample with ratio 0.8 and 1200 ^oC sintering temperature gives the highest value of thermal conductivity with 9.7614 W/m²K and the lowest thermal resistance with 0.1024 m²K / W.

Abstract: The work hardening behavior of electrodeposited nanocrystalline (grain size: 100 nm) and fully annealed polycrystalline nickel (grain size: 160 µm) was examined by hardness indentation analysis. First, plastic strain was introduced into the materials through large Rockwell hardness indentations. A series of Vickers micro-hardness traces below and away from the Rockwell indentation then measured the change in hardness as a function of distance from the plastic zone. The results showed that polycrystalline nickel exhibited considerable strain hardening, with micro-hardness values closest to the Rockwell indentation averaging twice the hardness value of the bulk material. On the other hand, for the nanocrystalline nickel the Vickers micro-hardness values changed only by a few percent indicating a limited strain hardening capacity.

Abstract: Instrumented indentation testing has been carried out on steel samples subjected to uniaxial loading. It is distinguished between purely elastic as well as elasto-plastic loading up to plastic strains of 3%. The experimental approach allows the combination of local in-situ residual stress analyses by means of X-ray diffraction and the subsequent realisation of instrumented indentation testing for the same material volumes beforehand irradiated by the X-rays. The aim of the investigations was to explore a potential correlation between the imposed macroscopic stresses and the characteristic values of instrumented indentation testing evaluated from the measured force-indentation depth curves according to the standard ISO EN 14577. The studies illustrate that results of depth sensing indentation testing have to be handled with care for prestressed material states. The effect of mechanical stresses on the results of instrumented indentation testing is not stringently limited on the hardness measures alone. Other indentation parameters like e.g. the indentation modulus EIT or the elastic part of the indentation work η IT are likewise affected by the prestresses, whereas the impact is in the order of magnitude that it has to be taken into account during interpretation of indentation readings.