Experimental evaluation on grinding wheel wear through vibration and acoustic emission

The dressing process is necessary to reestablish the surface of the grinding wheel, when its grains lose their edges and break due to the wheel wear. Dressing must be done to avoid part rejections caused mainly by roughness increase. The determination of the exact moment to accomplish the dressing process (known as the end of wheel life) is still a problem without a precise solution. Generally, machine operators decide when to dress the wheel based on their own experience. During the last years, several works have been done in order to build grinding monitoring systems that could determine the end of grinding wheel life in a more precise way, without the need of an operator. The objectives of this work follow this trend. Hardened steel workpieces were ground until their surface roughness reached values considered intolerable for grinding process. At the same time, vibration and acoustic emission sensors attached on two points of the grinder machine monitored the process, in order to indirectly establish the wheel condition and the moment to dress it. Besides that, the signals from these sensors were also used to determine the duration of spark out and elastic deformation phases of the grinding cycle. The vibration sensor proved to be the best one to establish the end of wheel life; the acoustic emission sensor is the most suitable to determine the time spent on elastic deformation and both acoustic emission and vibration sensors are able to detect the end of spark out phase. (C) 1998 Elsevier Science S.A. All rights reserved.217171

Evaluation of grinding fluids in the grinding of a martensitic valve steel with CBN and alumina abrasives

In this paper the performances of different cutting fluids and grinding wheel types were analysed in the grinding of SAE HVN-3 workpieces. The resulting residual stress, wheel wear and roughness were evaluated. The influence of the cutting fluid jet velocity v(j) was also analysed. As a conclusion, the lubrication ability seems to be the governing factor in the cutting fluid performance. The use of CBN wheels can significantly reduce the thermal damage in grinding, leading to compressive residual stresses. The CBN wheel and the cutting oil give an optimum combination for performing this grinding operation

The presence of Microlobius foetidus cause changes in the antioxidant defense of Urochloa decumbens?

AbstractUrochloa decumbens (Stapf) R. D. Webster (Poaceae) is an exotic species with has spread rapidly through the Cerrado area of Pantanal, Mato Grosso do Sul, Brazil. It has covered the soil aggressively turning it into cultivated pastures. Thus, it has become a challenge to protect native areas due its capacity of exclusion of native species. It has been observed that Microlobius foetidus (Jacq.) M.Sousa & G.Andrade species (Fabaceae) shows a dominant pattern over the development of U. decumbens. This work shows that M. foetidusinterfere on the natural growth of U. decumbens within 10 m ratio. Between 15 and 20 m, it was observed an increase of Importance Value index (IVI) and Relative cover (RC) values. It was also observed a variation on the antioxidant defense system of U. decumbens within 10m ratio from M. foetidus. The enzymes superoxide dismutase, catalase and peroxidase present higher levels of activity then those found for glutathione reductase. This data indicates that M. foetidus may have an effect on U. decumbens, increase the activity of antioxidant enzymes. This effect probably happens as means to neutralize the toxic effects of the oxygen generated due to the presence of allelochemicals, which increases oxidative stress