Application Of Strain-Strengthening Technology In The Light-Weight Design Of Liquefied-Gas Cryogenic Tanks

Liquefied-gas cryogenic tank is widely used in chemical, metallurgy,medical, aerostatical industries and many other fields. With the rapiddevelopment of the modern industries, more and more liquefied-gas isrequired and as a result, larger and larger liquefied-gas cryogenic tanks areneeded. A large tank calls for light-weight design. In this paper, mechanicalbehaviors of austenitic stainless steel after strain-strengthening were measuredand the application of strain-strengthening technique in the light-weight designof liquefied-gas cryogenic tanks were studied. The main contributions are asfollows.(1) The engineering techniques for strain-strengthening of a liquefied-gascryogenic tank are summarized which include requirements of non-destructivetests, requirements of testing medium, pressurizing process, measurement ofcircumferential length and qualification criteria, etc.(2) Tests for the mechanical properties of the EN1.4301austenitestainless steel after strain-strengthening were carried out. For that,strengthening tests up to6%strain were conducted first and then, normal unixial tensile tests were performed to measure the0.2percentage offset yieldstress Rp0.2and ultimate strength Rmafter strengthening. Results show thatRp0.2is495MPa and Rmis680MPa, the former is significantly larger thanthat without strain-strengthening. With measured mechanical properties, thedesign stress intensity of the material is evaluated which is261MPa.(3) Three design methods, namely design by rule, design by analysis andelastic-plastic limit load analysis, were used in the stress analysis and strengthdesign of a liquefied-gas cryogenic tank using EN1.4301austenite stainlesssteel with or without strain-strengthening. Results indicate that withstrain-strengthening, thickness of the inner tank is greatly reduced and theweight of equipment is remarkably decreased.(4) A parametric finite element model of the inner tank with theconnected strips was established and the strength was optimized using ANSYSoptimization procedures. Furthermore, the connection way of legs with theouter tank was also improved so as the load carrying capacity of the legs isenhanced.