Tongguang Zhai

Bio: Tongguang Zhai is an academic researcher from University of Kentucky. The author has contributed to research in topics: Alloy & Fatigue limit. The author has an hindex of 21, co-authored 88 publications receiving 1722 citations. Previous affiliations of Tongguang Zhai include Shandong jianzhu university 山東建築大學 & Hebei University of Technology.

Enhancement of fatigue and corrosion properties of pure Ti by sandblasting

Abstract: Commercially pure titanium was sandblasted with SiO2 particles of 200–300 μm in diameter. It was found that the sandblasted samples exhibited an increase in fatigue strength by 11% over that of the untreated samples. The peak subsurface compressive residual stress produced by sandblasting was measured by XRD to be around 480 MPa. Three distinct regions were observed in the sandblasted samples, namely the severely deformed surface layer, the region deformed mainly by twinning, and the substrate. After recovery treatment below 300 °C, the surface layer of the sandblasted samples was transformed into a nano-crystalline structure, and its corrosion resistance was significantly improved.

Effects of shot-peening and re-shot-peening on four-point bend fatigue behavior of Ti–6Al–4V

Abstract: The application of shot-peening to improve performance and reduce scatter in the high cycle fatigue regime is common in aerospace production practice. Frequently, aerospace components are re-shot-peened during refit to “restore” compressive stresses that may have redistributed in service. Since shot-peening is an impact process that can cause various surface artifacts, it is not clear what effect this re-shot-peening process has on fatigue properties. In the current study, the effects of shot-peening and re-shot-peening on the profile of surface residual stress and the four-point bend fatigue behavior of Ti–6Al–4V(wt.%) alloy were investigated at room temperature and 150 °C. A step-test method was used to determine the fatigue strength of the shot-peened and re-shot-peened specimens in different conditions. Shot-peening improved the fatigue strength of the alloy from about 65% σ y to 71% σ y ( σ y is the yield strength of this alloy at room temperature). The fatigue limits of the shot-peened Ti–6Al–4V alloy at room temperature and 150 °C were found to be almost identical. Residual stresses did not seem to redistribute significantly under the fatigue loading at room temperature and 150 °C. Both shot-peening and re-shot-peening significantly enhanced the fatigue strength over that of the un-shot-peened alloy. No negative effects of re-shot-peening were observed.

Effects of Pore Position in Depth on Stress/Strain Concentration and Fatigue Crack Initiation

Abstract: The stress field around a pore was analyzed as a function of the pore position in depth in the surface of a linear elastic solid using finite element modeling It was found that the pore depth dominated the stress field around the pore on the surface and that the maximum stress was increased sharply when the pore intercepted with the surface at its top Given the applied nominal stress, the magnitude of the maximum main stress only depended on the relative depth of the pore, while the pore size affected the stress distribution in the surface An elastic-plastic model was also used to account for the yielding effect in the region where stress was over the yield strength The results still indicated a significant maximum stress concentration when the pore was just buried underneath the surface, but with a lowered value than that of the linear elastic model These results were consistent with the experimental observations that fatigue cracks were preferably initiated from pores and particles, which were just intercepted at their top with the sample surface or just buried beneath the surface

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These