LOW-TEMPERATURE AUTOFRETTAGE: AN IMPROVED TECHNIQUE TO ENHANCE THE FATIGUE RESISTANCE OF THICK-WALLED TUBES AGAINST PULSATING INTERNAL PRESSURE |
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Authors: | H Mughrabi B Donth G Vetter |
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Affiliation: | Institut für Werkstoffwissenschaften, Lehrstuhl I (Allgemeine Werkstoffeigenschaften), Universität Erlangen-Nürnberg, D-91058 Erlangen, F.R. Germany;Institut für Verfahrenstechnik, Lehrstuhl für Apparatetechnik und Chemiemaschinenbau, Universität Erlangen-Nürnberg, D-91058 Erlangen, F.R. Germany |
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Abstract: | Abstract— It is shown that autofrettage at low temperatures is superior to autofrettage at room temperature in enhancing the fatigue resistance of thick-walled tubes against pulsating internal pressure. The physical reason is based on the well-known temperature dependence of the mechanical behaviour of metals and alloys which generally exhibit an enhancement of both the yield stress and strain hardening behaviour at lower temperatures. As a consequence, significantly larger compressive residual hoop stresses can be introduced during pressurization at low temperatures than at room temperature. Experimental data obtained on thick-walled tubes of the metastable austenitic stainless steel AISI 304 L which were subjected to pulsating internal pressure at room temperature after autofrettage at temperatures between-110°C and room temperature are presented. These data demonstrate convincingly the advantages offered by low-temperature autofrettage in enhancing both the fatigue life in the finite-life region and the fatigue endurance limit in comparison with autofrettage at room temperature. In conclusion, some specific materials requirements for optimum low-temperature autofrettage performance are discussed. |
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Keywords: | Low-temperature autofrettage Thick-walled tubes Residual stresses Pulsating internal pressure Fatigue of tubes |
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