Control of Local Hardness Gradient of Metal Surface by Inclined Surface Treatment Using Ultrasonic Nanocrystal Surface Modification

We propose an effective method to control the local hardness and morphology of a metal surface by tilting the incident angle of a horn during ultrasonic nanocrystal surface modification (UNSM). In this study, surface treatment using UNSM was performed on an S45C specimen and a parameter study was conducted for optimization. The process parameters were the feeding rate, static load, striking force, and processing angle (Ф). In particular, the Ф was analyzed by tilting the horn by 0°, 10°, 20°, 30°, 40°, and 45° to understand its effect on surface hardness and changes in the morphology. From fundamental experiments, some important phenomena were observed, such as grain-microstructure changes along the processing and thickness directions. Furthermore, to verify the practical usefulness of this study, a flat and a hemispherical specimen of S45C material were treated using UNSM with various values of Ф. A significant change in hardness (an increase from 2–45%) and a gradual hardness gradient on the tested specimens could be easily realized by the proposed method. Therefore, we believe that the method is effective for controlling the mechanical hardness of a metal surface.

Methods of elimination of rails increased damage in the area of weld joints

Rail weld joints from electric-contact welding in stationary and fi eld conditions, as well as those from aluminothermic welding are weak points on tracks that are easily damaged compared with rails outside the weld joints. Currently, these weak points are the defects connected with lack of penetration in the welding area, burns at the points of poor contact of the rail foot with the current-carrying contact tips, or with defects of the weld joint machining after welding, as well as the local hardness reduction in areas affected by heat after welding, and local heat treatment after welding. Elimination of wide areas of reduced hardness at the weld joint points producing saddles, cracks, and chipping, and promoting rails damage next to such joints is a major challenge for increasing the serviceability of weld joints. This study introduces three avenues for elimination of increased damage of rails at weld joints including:• Improvement of technology and equipment for electriccontact welding and local heat treatment after welding in the stationary and fi eld conditions.• Development of technology and equipment for induction welding in the stationary and fi eld conditions.• Development of technology and equipment for differentiated induction tempering of rails preliminary welded in strings 800 m long.

Methodischer Festigkeitsnachweis spielbehafteter lokal gehärteter formschlüssiger Kupplungen/Methodical Strength Assessment of Interlocking Couplings Considering Local Hardness and Clearance

Inhalt: Ein Versagen formschlüssiger Kupplungen zur Übertragung von Drehmomenten führt in der Regel zum Ausfall des gesamten Antriebsstranges. Die Forderungen nach immer leichterer Bauweise sowie gleichzeitig höherer Leistungsfähigkeit auf der einen Seite und günstigeren Fertigungskosten auf der anderen Seite stellen die Entwickler in diesem Zusammenhang vor immer neue Herausforderungen. Dabei entstehen neue Lösungsansätze, für die es in der Literatur keine hinreichenden Auslegungsregeln gibt. In dieser Forschungsarbeit wurde ein methodischer Festigkeitsnachweis einer auf dem Oldham-Prinzip basierenden, dynamisch belasteten Kupplungskomponente entwickelt, der die Auswirkung von Einbauspiel und lokal gehärteten Bereichen auf die Lebensdauer des Bauteils berücksichtigt. Mit umfangreichen Versuchsreihen konnte die Methode experimentell validiert werden.