TPT July 2010

A rticle

New developments in the field of continuous production of corrugated metal hoses Stefan Weiss – Rosendahl Maschinen GmbH, Austria, Thomas Hatzenbichler and Bruno Buchmayr, Chair of Metal Forming, Department Product Engineering, University of Leoben, Austria

Introduction Benefits of corrugated tubes

By the time compensators with corrugated shape are wide spread in mechanical engineering. One further application is the use as hoses to protect eg cables against damage due to mechanical forces and as sealing against atmospheric exposure. So, different product properties can be assigned to one constructional element in the sense of value engineering. Especially for mechanical protection application the cross pressure resistance is a main criterion. The goal is to find an optimum between flexibility and compression strength for hauling. Using a smooth tube the only way to improve bendability is to reduce the wall thickness or change the material which often leads to disadvantages in stability and costs. Figure 2 shows the elastic deformation of a smooth and a corrugated tube in principle computed in a FE-Simulation with NX Nastran. The main input data for this simulation are: • tube outer diameter 20mm • wall thickness 0.2mm A concentric force of 10N is applied three times from the outside to a smooth and a corrugated tube to show the difference in deformation. Comparing the magnitude of displacement shows a 2.1 times higher value for the smooth tube. So the cross pressure resistance can be increased in a very pronounced way without losing flexibility. Further on it is possible to reduce the wall thickness which gives a positive effect on costs and weight. • material AISI 304 (1.4301) • corrugation depth 1mm 3

Corrugated metal tubes are a well known alternative to smooth metal tubes or hoses made of plastics for different applications for many years. Using a corrugated design makes it possible to improve these mechanical product properties generally: • bendability • flexibility • form stability • compression strength Higher flexibility offers movement in axial, angular and lateral direction as shown in Figure 1. Due to these characteristics corrugated shaped tubes can be used in addition for transportation of fluids and as constructional elements.

Figure 1 : Flexibility of corrugated tubes [1]

Figure 2 : Cross pressure resistance of corrugated tubes

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J uly 2010

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