Advanced Materials Research Vols. 41-42

Abstract: A new twenty-freedom non-linear dynamic model for two-span dissymmetric elastic rotor system was established by considering the crack fault, rub-impact fault and oil film force. The complex motion characteristics of this system were numerically studied and the effect of different parameters on the system is investigated. Moreover, the both cases with and without crack fault were discussed in detail. The results indicate that the system has obvious single-period, period-doubling bifurcation and chaos phenomena. There are marked influences of the crack faults on the nonlinear characteristics of the system, especially under some the rotating speed. The case considering crack faults has different chaos region from the case without crack fault. The chaos phenomenon appears at lower rotating speed, and when the chaos comes again, the corresponding rotating speed extends backwards. Synchronously, the influence of crack fault increases along with the depth of crack. The results may provide theoretical references for rotor fault diagnosis.

Abstract: ASTM A106/B is commonly used for pressure piping in alumina refineries. Due to the problem of caustic cracking in alumina refineries, piping must be stress relieved after welding, usually through a post-weld heat treatment (PWHT) process at a temperature of 635°C. However, multiple PWHT procedures tend to degrade the mechanical properties of steel and design standards have set limits on the length of time PWHT can be carried out before steel should be replaced. In this study, the effect of PWHT time on the properties of A106/B parent metal was examined, with particular emphasis on the effect on toughness. PWHT was carried out for 1, 8 and 40 hours and the results were compared with those for as-received material. Impact transition temperature and room-temperature tensile results were determined using standard tests. The reference temperature, To, was determined using ASTM E1921 with arc-shaped tension specimens. The results showed that the ductile-to-brittle transition temperature increased significantly as PWHT time increased and the implications of this to a fracture mechanics analysis of plant operations are discussed.

Abstract: In the result of corrosion phenomena in automotive metallic fuel tank, a layer of rust which consists of hard and micronized oxide grits with low cohesion and adhesion could appear. Through gasoline delivery from fuel tank to chamber of combustion, these hard and micronized grits could cause erosion and service problem for the components in this rout. In concept of after sale services, some defective parts such as fuel tank, injector pump, nozzle of injector and etc, needs to be repaired or changed due to the corrosion. In this article in order to improvement of corrosion resistance, some investigations into the recognition and assessment of corrosion in which relative these parts have been done. The corrosion mechanisms such as galvanic corrosion, general corrosion have been recognized. Based on this information modification and improvement are concentrated in field of welding, plating showed considerable improvement in corrosion resistance.

Abstract: Acoustic Emission (AE) monitoring is an effective tool for prioritising more conventional non-destructive inspections of above ground tanks, either process or storage vessels. Results obtained from AE monitoring may be assessed against an existing data bank permitting plant management to prioritise maintenance to tanks with high active corrosion rates or leaks. AE results may be used to extend inspection periods of tanks without leaks or active corrosion. This paper covers the theory of AE leak detection and corrosion monitoring including some background research into the difference between AE from corrosion and leaks. It looks at the equipment used and provides a summary of tank test results conducted by ATTAR and other overseas organisations as well as reviewing AE tank inspection economics.