Daimler Chrysler Ag

Daimler-benz Ag

Georg Dirmeier

Siegfried Emmann

Manfred Haller

An arrangement for detecting a fatigue fracture caused by overstressing of a bolted connection including a bolt and an internal-thread-bearing hollow section which is alternately stressed by an axial flux of force between zero and different maximal values. A transverse crack forms at a predetermined breaking point of the bolted connection, at which the hollow section breaks due to fatigue. The spacing of the predetermined breaking point from the connection ends, and the interaction of the bolt and the hollow section, are designed such that, after the breakage, the bolt forms in the hollow section a residual joining connection which can be alternatingly stressed. In order to signal the occurrence of a crack on the hollow section of the bolted connection in the event of a fracture caused by fatigue in a simple and always noticeable manner, the arrangement has an additional signaling device. The signaling device is arranged at least on the section of the residual joining connection formed by the area with play of the bolted connection such that the crack causes its destruction, whereby the device causes at least one signal which can be noticed visually or acoustically. The signaling device may be microcapsules containing dye arranged in the threads, a hollow space adjacent the bolt filled with pressurized gas, or a ripping wire attached to the hollow section.

Arrangement and method for detecting a fatigue fracture of a bolted

A connector assembly that is subjected to alternating loads by an axial flow of force between zero and various maximum values, with an outer assembly component designed as a hollow section and an inner assembly component located in the outer one and fitting by virtue of its shape. In order to detect failure of the assembly caused by a fatigue fracture produced by overloads at the end point in the assembly direction, even before it develops, in a simple fashion within the functional assembly, the assembly comprises a rear area with play that begins at the end of the connection that points in the assembly direction and a forward zero-play area of the inner assembly component that abuts the latter and is located inside the outer assembly component. The transition between the areas forms a desired breakage location between the two ends of the connection, at which point one of the assembly components, upon the formation of a locally defined crack that runs in the transverse direction of the assembly, breaks as a result of fatigue after a certain number of overloads. The distance of the required breakage location from the ends of the connection is so dimensioned and the cooperation of the assembly components is so designed that the inner assembly component within the outer assembly component forms a residual assembly that can withstand alternating loads after fracture.

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Stuttgart, Germany

Georg Dirmeier