Fretting fatigue tests at elevated temperature were carried out using shot-peened specimens to improve the high temperature fretting fatigue strength of 12Cr-Mo-W-V steam turbine steel. Shot peening improved fretting fatigue strengths by a factor of 1.8 at an elevated temperature (773 K) as well as at room temperature. Residual compressive stresses first drop rapidly by a factor of three and then level off. Residual compressive stresses of 200 MPa were measured after a 30 000 h exposure at 773 K. Shot peening is thus shown to be effective over long periods at 773 K.

Fretting fatigue tests of high tensile roping steel, 1 .5 mm in diameter, 1770 MPa grade, were carried out in air and seawater. S-N curves were completed in both the environments and under cathodic protection at -850 mV (SCE). The crack growth curves were determined at three different alternating stress levels. The coefficients of friction between the specimen and the fretting bridge, where the macro-slip occurred, were found to be 0.63 in air and 0.38 in seawater. The prediction of the fretting fatigue lives were made according to the Tanaka-Mutoh model, where the frictional force was taken into consideration. The predicted fatigue life agreed well with the experimental results in air but in seawater the prediction defined a much higher fatigue limit compared with the experimental results which showed the absence of the fatigue limit. These results indicate that the method of removing the electrochemical component is very promising for the prevention of fretting fatigue failure in seawater.

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ab s t r ac tAmino-functionalized silica membranes were applied to the separation of water/ethanol mixtures by pervaporation. An increased interaction between the silica membrane surface and permeating materials is important in order to enhance separation. In this study, the improvement in water permeance ability and selectivity was examined by modifying the silica membrane surface with amino groups. Silica membranes were prepared by the sol-gel method of hydrolysis and cocondensation processes using tetraethoxysilane (TEOS) as a silica source and 3-aminopropyltriethoxysilane (AP-TES) to introduce the amino groups. The performance of membranes prepared with various molar ratios of TEOS/APTES was evaluated by pervaporation of water/ethanol. The separation property of the amino-functionalized membrane was higher than that of a membrane prepared with TEOS. The membranes were characterized by FE-SEM, FT-IR and single gas permeation measurements of He and N 2 .

Fatigue tests and fretting fatigue tests of two steam turbine steels at room temperature and 773 K were carried out. The reduction of fatigue life and strength in the fretting test were significant at 773 K as well as at room temperature. The values of the friction coefficient at 773 K was almost equal to those at room temperature. The geometry of the fretting fatigue crack was flat in the early stage of fatigue life where a significant effect of fretting was observed. With increasing crack length and with a reducing effect of fretting, the fatigue crack shape changed to a semi-circular form. The fretting fatigue lives predicted on the basis of elastic-plastic fracture mechanics analysis, with the frictional force between the fretting pad and the specimen taken into consideration, agreed well with experimental results at both temperatures.