Vol. 11, No. 6 (1955)
A method is presented here to sum certain type of Fourier series. The series is treated as a response function of a linear electric circuit with lumped constants. This electric circuit, subjected to the action of an external force expressed in the form of another Fourier series derived from the original series to be summed can be formed by inspection or by network synthesis. If this derived series can be put into a closed form, then by applying the steady-state operational technique to this electric circuit, the original series can be expressed in a closed form or in a graphical form.
1955, 32 (6): 469-478. doi: 10.7498/aps.11.469
In the spectrochemical analysis of high speed steels with a small current activated a.c. arc (after Aбрамсон), the results of analysis were found to be affected by different previous heat-treatments given to the steel samples. To study this effect we selected 10 chromium steel samples of different carbon content. Spectrochemical analysis of these samples under different procedures of heat treatment shows that with an a.c. arc (5 amp.) the results of analysis of Cr for annealed and for hardened samples of the same steel are different and the difference increases with the increase of carbon content. We are inclined to think that in a low energy light source, the evaporation and the excitation of the alloying elements vary according to the existing form of carbon and this directly affects the results of spectrochemical analysis. The magnitude of this effect is different for different alloying elements, it is considerable in the case of Cr but is inappreciable in the case of Mn and Si.How to eliminate the effect of micro-structure on spectrochemical analysis was also investigated. It was found that with a low energy light source, the effect can not be eliminated by increasing the time of pre-arcing. However, this effect is considerably reduced by using a spark source or an a.c. arc source of large current.
1955, 32 (6): 479-492. doi: 10.7498/aps.11.479
Internal friction in hardened carbon steels was measured with a torsion pendulum and an internal friction peak was observed around 130℃ when measurements were taken from room temperature upwards. This peak disappeared completely after the temperature of the specimen reached 170℃. This phenomenon was observed in carbon steels containing carbon ranging from 0.29% to 1.4%, and also in an alloy steel. The appearance of this internal friction peak seems to indicate that the transformation product (ε-carbide) formed in the first-stage tempering of martensite is in coherence with its parent phase, and the origin of internal friction is the stress-induced movement of the plane of coherence.The above-mentioned internal friction peak was not observed in 0.25% carbon steel specimens having a martensite structure. However, after such a specimen has been tempered at a temperature around 300℃, an internal friction peak was observed around 150℃. This indicates that the transformation product formed in martensite containing 0.25% carbon in the third-stage tempering is in coherence with its parent phase. Since the internal friction peak associated with this transformation product behaves differently from that associated with this ε-carbide, so it may be concluded that this transformation product is not ε-carbide.