Experimental studies on noise spectra of ball-rod hardening of wheel pair assemblies

Introduction. Currently, wheel tread surfacing is implemented on special design wheel lathes. This method provides the desired technological strength of the wheel treads, but does not provide hard facing and, consequently, does not increase wear resistance. Ball-rod hardening (BRH) has great advantages as a process, especially for composite geometric surfaces; and besides, it enables the necessary compressive stresses in the surface of the hardenable products. However, it has a significant disadvantage in terms of the increased levels of the acoustic pressure in the operators’ working area. Materials and Methods. The experimental studies under BRH of the wheelpair assembly elements are carried out by several process steps. Wheel tread surfacing is performed on a special design wheel lathe on which ball-rod reinforcers are installed instead of a cutter. Hardening of the mounting surfaces of the wheelset axles is performed on a special axial lathe on which, in a similar manner, ball-rod reinforcers are installed instead of a cutter. Hardening of the wheel mounting surface is performed on a boring-and-turning mill. The octave sound pressure levels are measured on all of these lathes at idle and under the hardening process implementation. It allows determining the contribution of the sound radiation of the acoustic subsystem “hardenable product - ball-rod reinforcer” into the soundfield generated by a common lathe loudspeaker system in the operators’ working area. Research Results. Due to the high intensity of the radiant sound energy, the equipment is installed in separate facilities commensurable with the overall machine dimensions that consequently contributes to the increased noise activity. Therefore, the research data are of current interest for the enterprises of mechanical engineering, and they have both scholary interest and practical applicability. Discussion and Conclusions. It should be noted that the data obtained on the regular engine lathes, i.e. on round work pieces, are a particular case and are not applicable to the assembly of such complex geometrics as wheelpairs of rolling stock and various types of cranes. The implemented measurements show that under BRH, sound pressure levels exceed health standards by 5 to 15 dB of the high-frequency part of 500-8000 Hz spectrum, i.e. in the range in which the maximum permissible levels should not exceed 78-69 dB.