Upcoming Seminar February 23
Tuesday the 23th of February 9.15 to 12, there will be a seminar in room J1280 at BTH campus Gräsvik. The seminar is arranged by the Department of Mechanical Engineering at BTH and three researchers from China will present their research works:
Professor Chuanri LI
9.15-10.15: “The Physics of Failure Based Reliability Analysis and Test Method for Avionic Device“, by Professor Chuanri LI from Beihang University (http://ev.buaa.edu.cn/), China. (One of Prof. LI’s PhD student has been here at BTH as a joint PhD student.)
“The reliability is very important for avionic system working in harsh environmental. The verification and demonstration of reliability will be very difficult for products with very high reliability and long life when using traditional statistical method. As the reliability is very close related with the failure of products, a new method based on physics of failure can be used to deal with this difficulty. The design and analysis method for high reliable product can be based on different failure mechanism. The method of test and demonstration of reliability can also be determined by the failure type. The strength-stress model can be used in both over-stress failure and cumulative stress failure. In this method the environmental test result can be used to evaluate the reliability of the product.”
Associate Professor Rundong WAN
10.30-11.00: “Hybrid functional application on carbon doped titanium dioxide” by Guest researcher at BTH, Associate Professor Rundong WAN from Kunming Univ. of Sc. and Tech. China
Density functional theory calculation can accurately predict many properties of a material. For an extended system materials, we can obtain the structural, chemical, optical, spectroscopic, elastic, vibrational and thermodynamic properties. Original developed DFT encounters obstacle when dealing with one of most important electronic properties: the band gap and optical transitions of semiconductors or insulators. This is the wide recognized under-estimation of these values. To overcome this shortcoming, there have been a few theoretical methods developed. The most effective one is hybrid functional approaches, in which Hartree-Fock method is incorporated with the exchange-correlation functional. By this modification, some hybrid functional calculations can reproduce the experimental band gaps very well. The HSE06 functional is the most efficient and lightest hybrid functional so far. We have applied the HSE06 functional in our study on the carbon doped titanium dioxides. We have found that the geometrical parameters agree with other published results. In term of the band gap narrowing, we found the trend are different.
11-11.30: “A study on fretting damage mechanism of lightweight alloy sheet” by Guest PhD student at BTH, Lun ZHAO from Kunming Univ. of Sc. and Tech. China
Fretting damage is one of the most important reasons for causing the failure of the crucial components in the industry. Fretting damage occurs at the contact surface between two components, where relative micro-slip at the interface between two surfaces in intimate contact plays a significant role. This research mainly deal with the fretting damage mechanism of lightweight alloy sheet. The surface morphology, crack length, deformation, and the size and chemical composition of the third-body debris were investigated in the research. Fatigue tests were performed to characterize the fretting damage data of the components. Scanning electron microscopy (SEM) and Energy Dispersive X-ray Detector (EDX) were employed to obtain the surface microstructure of the fretting damage and chemical composition of third-body debris. The results showed that the surface morphology of fretting damage area exhibits the phenomena of micro-crack, delamination, pit, deformation and third-body debris. Micro-cracks are generated from fretting domain of the sheet and gradually propagate to fatigue macro-crack, which results in the failure of the component. The main function of third-body on the contact surface of the aluminum sheet is relieved wear in fretting process, the chemical compositions of the debris are largely made up of aluminum and oxygen with a small quantity of magnesium so the main ingredient of the debris is deemed to be Al2O3. The size and degree of fretting damage are strongly dependent upon fatigue load and fretting cycle.
For more details, contact Professor Sharon Kao-Walter (firstname.lastname@example.org)