TPT July 2010

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106 J uly 2010 ›
Article
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
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.
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
• material AISI 304 (1.4301)
• corrugation depth 1mm3
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.
Figure 2:
Cross pressure
resistance of
corrugated tubes
Figure 1: Flexibility of corrugated tubes [1]