Magnetic softening of young's modulus of amorphous Fe90Zr10
Abstract The Young's modulus and the internal friction of amorphous Fe90Zr10 alloy were measured near the Curie temperature using the vibrating reed technique. The modulus shows softening around Tc(= 227 K) and the internal friction undergoes drastic increase in the same temperature range. It is found that both the Young's modulus and the reciprocal of internal friction are inversely proportional to the magnetic susceptibility in the paramagnetic phase.
Magnetoelastic study of amorphous Fe90+xZr10-x alloys
Abstract Young's modulus ( E ) of stress-relieved Fe-rich Fe–Zr amorphous alloys has been measured as a function of temperature in the range 80–350 K using the vibrating reed technique. The measured E ( T ) data are corrected for thermal expansion and non-magnetic background, E bg ( T ), to arrive at the magnetic contribution to Young's modulus, Δ E / EE bg =[ E ( T )− E bg ( T )]/ E ( T ) E bg ( T ), in the ferromagnetic state. A strikingly different behaviour of Δ E / EE bg is observed in alloys whose Fe content differs barely by 1 at% in that Δ E / EE bg decreases monotonously in amorphous (a-) Fe 90 Zr 10 , whereas after an initial decrease it increases steeply in a-Fe 91 Zr 9 as the temperature is lowered from the Curie point ( T C ) down to 80 K. Generalisation of the Landau theory of phase transitions leads to an expression for Δ E / EE bg that includes both first- and second-order magnetoelastic contributions, which respectively are linear and quadratic in stress. This expression is shown to provide a straightforward explanation for the distinctly different behaviour of Δ E / EE bg observed in a-Fe 90 Zr 10 and a-Fe 91 Zr 9 alloys. Furthermore, the present theoretical approach not only brings out clearly the role of exchange-enhanced local spin-density fluctuations in the thermal demagnetisation of spontaneous magnetisation but also permits an accurate determination of the pressure dependence of T C from the Young's modulus measurements on systems (which exhibit strong magnetoelastic effects) such as the alloys in question.
Economics of General-Purpose Assembly Robots
Summary A study of the comparative economics of various automatic assembly systems using general-purpose assembly robots is described. In the study, use is made of a “typical” candidate assembly whose profile is obtained from statistical analysis of actual products submitted by interested companies. It is shown that the choice of assembly system and the various parts presentation methods depends on three main factors, namely: the annual production volume per shift, the number of parts in the product and the equipment payback period.