| Based on referring to large numbers of literature, material property of ultrahigh pressuretube and stress field and flow field of end structure of the ultrahigh pressure polyethylenetubular reactor, in which corrosion fatigue fracture often occurred, were studied byexperimental and numerical simulation method. The detail status of local stress field and flowfield were exploded, and their influences on fatigue failure were analyzed, finally, somefeasible optimal schemes were provided. The main work and conclusions are as follows:⑴Chemical constitution of AISI4333M4is measured up to standard, so is the yieldstrength, tensile strength, ballistic work and fracture toughness property. The materialproperties of ultrahigh pressure tube have not deteriorated for17years work.⑵Local stress field of end structure is caused by shrink-fit, axial tensile stress is high onthe location at the edge of the shrink-fit under the shrink-fit, autofrettage treatment and thestartup load, and it’s larger than hoop stress. Fatigue alternating stress level is high under thestartup and shutdown cyclic loading, which indicates that the crack driving forceperpendicular to the axial direction is relative larger.⑶Local stress level of end structure increases significantly with the increase of shrinkrange and autofrettage pressure, and local axial stress level increases with the increase ofthickness and length of the jacket.⑷The flow state of end structure is bad, especially the root of jacket, flow velocity ofcooling water is next to zero, which increases the rate of corrosion scaling and raises the riskfor forming initial flaw, and then offering active influence on the corrosion fatigue fracturefailure of end structure.⑸Some feasible optimal schemes are offered such as designing guide-vanes which canimprove flow field, designing step-jacket which can improve stress field, designing packingbox seal which can improve stress field and enhancing water quality control. |
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