An investigation of the grinding wheel wear with the use of root-mean-square value of acoustic emission
This paper presents the results of an investigation of the grinding wheel wear in a peripheral surface grinding process. During this investigation varying geometrical parameters of an active grinding wheel surface have been measured and the components of the grinding force and acoustic emission signal have been recorded. On the basis of these output quantities an analysis has been conducted of an acoustic emission descriptor's practicability, i.e. a root-mean-square (RMS) value, to characterize the cutting abilities of a grinding wheel in the time progress of its work. This article also presents a new energy coefficient, which determines the rate of grinding wheel wear in the form of a RMS value of acoustic emission signal falling on a contact surface of a grinding wheel. Moreover, the article presents some examples of a correlation between the root-mean-square value of acoustic emission signal and the surface roughness of a workpiece, which shows that the parameters of acoustic emission signal can be a useful tool to monitor the surface roughness during the grinding process.
Extracting Acoustic Emission Signal Feature of Grinding Processing
Acoustic Emission (AE) may be defined as a transient elastic stress wave generated by the rapid release of strain energy in local area of material. To overcome the limitation of some traditional techniques, the AE technique, which provides high sensitivity and responding speed, were developed in the present paper. AE signature is usually difficult to be extracted and characterized in grinding process of 1Cr18Ni9Ti coatings due to their high hardness, great ductility, inhomogeneous structure and irregular surface with lots of hard points and pores. In this paper, AE signal of stationary grinding status before wheel-workpiece contact was characterized first, then AE signal of the grinding process was analyzed using root-mean-square (RMS) and power spectrum method. Results showed that before the contact occurred, the grinding signal is stable, with low amplitude and frequency ranging all frequency channels and no peak signal. However, when contact occurred, the RMS and spectrum of AE signal increased obviously and the bandwidth varied exquisitely between 100 KHz and 300 KHz. The real contact time between wheel and workpiece was about 0.5 to 1 ms.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.