Using Vickers indentation method, plastic deformation (Ef) is suggested to be a convenient measurement to determine the ductility (brittleness) of brittle new materials. It was found that Ef is related empirically to KIC and GIC through a logarithmic linear relationship.
AbstractIn the present work, the regenerative thermal oxidiser (RTO) with preheating and baking system was applied to treating volatile organic compounds (VOCs) discharged from the shell mould casting. As a result, it was found that the tar characterised by more than 523 K of high boiling point was formed by the shell mould casting. The Fourier transform infrared spectrometry analysis showed that the tar was composed of paraffin, zinc stearate and quartz. A part of the tar was deposited on the ceramic honeycombs in the heat exchanger. However, the tar can be almost completely removed by means of baking treatment at 623 K in the RTO. Regarding the decomposition of VOCs, it was found that the concentrations of all VOCs were reduced to less than 1 ppm. Further, 98% of offensive odour was removed by the treatment. Thus, it can be concluded that the RTO is suitable for decreasing VOCs from the shell mould casting in the foundry.Keywords: VOLATILE ORGANIC COMPOUNDS (VOCS)REGENERATIVE HEAT EXCHANGERSHELL MOULDSODOR CONCENTRATIONTAR ADHESION
Because of the importance, from the engineering point of view of evaluating brittleness, a study was undertaken on critical stress (Pf) and critical strain (df) in the relation between load (stress) and the size of the pyramidal hole (strain) under microplastic deformation of brittle Ni-S alloys. Deformation energy (Ef) on fracture was also evaluated. Brittle Ni-S alloys were prepared by electroplating on Cu sheet (current density=60A/m2, distance between electrodes=40mm, pH=6.0, bath temperature=303K). The concentration of the water solutions were 100g/L for NiSO4(NH4)2SO4·6H2O, 15g/L for Na3C6H5O7·2H2O, and 1∼30g/L for Na2S2O3·5H2O. Ni-S alloy composition was varied by controlling the concentration of Na2S2O3. Precise evaluations of fractures were preformed with a Vickers microhardness tester. The addition of sulfur was found to decrease resistance to microplastic deformation (Po), however the higher the sulfer concentration, the lower were the values of Ef, df, and Pf become. Comparing values of Ef, the brittleness of Ni-S alloys was found to approximate the values obtained for Al2O3 and slide glasses.
Most intelligent materials are brittle. From the engineering point of view, it is just important to evaluate the fracture toughness. KIC is a standerd value to evaluate the brittleness. However, it is difficult to prepare (form) test specimens. Vickers hardness tester is a good tool to know many mechanical propaties without fracture. In this paper, we introduce evaluate methods of fracture toughness for brittle materials by means of Vickers hardness tester. Indentation fracture (IF) method is easy to detarmine KIC to measure crack length around the indentation, load, diagonal and Young's modules. On the other hands, we have suggested a new method to evaluate brittleness by means of critical deformation energey (Ef). Ef is calcurated by critical load (Pf) and critical diagonal (df) only. This method is useful to evaluate brittleness of small or thin specimens.
