VERIFICATION METHOD FOR FLEXIBLE EXHAUST HOSE : A background study

Abstract: On Scania trucks of today a flexible exhaust hose is used to decouple the motions of components in the exhaust system. This flexible hose section experiences premature and unpredictable failures. To gain control over the situation a lifetime assessment is required, in which the ultimate verification is to be confirmed in a test rig. In order to build this rig and perform adequate tests, background information is needed. This report is aimed at collecting and analysing information on the underlying problem, such as material characteristics, working conditions and failure modes for the flexible hose. This is done by a literature study, measurements and investigations and an FE-model. The results show that the major failure mechanism is wear. The wear is concentrated to a small portion of the hose due to the unstable nature of the construction, aggravating the working conditions for the material. In addition, heating to working temperature seems to bring with it much increased wear rates and a significant increased friction coefficient for the interaction between the metal sheets constituting the hose. Because of the working mode of the hose, the material used should be replaced with a more suitable alternative. To start out, a change from the current EN 1.4301 (AISI 304) to the, from the manufacturer instantly available, EN 1.4571 (AISI 316 Ti) should be made. There are other material alternatives offered as direct replacements, these should be evaluated along with suitable surface treatments.