In-process sensing of tool wear and process states using a cylindrical displacement sensor in hard turning

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system for monitoring cutting conditions during hard turning was tested in this research. The sensor was installed between the face of the spindle cover and the chucking element, and measured pure radial motion of the spindle under conditions of roundness error at the measured surface. To prove the effectiveness of the developed system, hard-turning tests using ceramic inserts and with tool steel as the workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations in pure radial motion of the spindle were measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased, both the static component of the cutting forces and the centre shift of the spindle orbit increased. Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the unmanned machining centre.

Magnetic Correlations in Spin Glasses above the Freezing Temperature investigated by High Field Mössbauer Spectroscopy

The strong dynamics of magnetic correlations are observed by high field 57Fe Mössbauer investigations for the spin glasses AuFe and Y(Fe, Al)2 in the temperature interval between the freezing temperature Tf and approximately 7 to 10Tf. All recorded spectra can be analysed with a model which takes into account these dynamics by allowing the formation of correlated states after a stochastically varying time τoff and their decay after a time τon, restricting the number of subspectra to the different number of Fe atoms in the first neighbour shell. Whereas for the different Fe environments, in addition to centre shift and quadrupole splitting, different hyperfine fields of the two stochastically formed states can always be resolved, the same set of τon and τoff values was obtained for all subspectra above approximately 4Tf. The external field hinders the decay of the correlated regions. The temperature dependence of ¿ on scales with Tf and exhibits a power law with exponents of –2 for the Fe-rich and –1 for the Fe-poor compounds.