An integrated optimization design was described using multilevel decomposition technique on the base of the parametric distribution and independent axiom at the stages of lower level. Based on Pareto optimum solution,...An integrated optimization design was described using multilevel decomposition technique on the base of the parametric distribution and independent axiom at the stages of lower level. Based on Pareto optimum solution, the detailed parameters at lower level can be defined into the independent axiom. The suspension design was used as the simulation example. In an axiomatic design for the optimization design, the uncoupled and decoupled designs between functional requirements and design parameters are generally needed. But using the design sensitivity(or screening) of design parameters, the approximate uncoupled design is developed on behalf of the decoupled and coupled designs. Successive design parameters were applied to the suspension of torsion beam axle. The structural performance increases by 18%. The kinematic and compliance performance increases by 6% within the feasible ranges.展开更多
Aluminium trihydrate(ATH) is being extensively added to polypropylene(PP) to make a fire retardant composite. Blends of PP/ATH composite are more fire resistant as compared to pure PP. Percentage proportion of both th...Aluminium trihydrate(ATH) is being extensively added to polypropylene(PP) to make a fire retardant composite. Blends of PP/ATH composite are more fire resistant as compared to pure PP. Percentage proportion of both the constituents in the final composite depends upon the application. Improvement in the fire retardant properties of such composites have been studied and published in literature but effects on mechanical strength have not been addressed. The effect of concentration of ATH on the strength of PP/ATH composite was presented. The tensile, flexural and fracture properties were studied and discussed. Experimental tests, ASTM analytical formulae and finite element approach were used. It has been found that increase in ATH has an inverse effect on the mechanical strength.展开更多
A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to...A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strikes. A planar shutter type electric field mill （EFM） with a rotating vane is studied to measure the electric field. From a calibration experiment, the sensitivity of the EFM was adjusted to 0.15 V/kV/m, and this covers the ranges from 200 V/m to 20 kV/m. Magnetic field waveform is detected by a crossed loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges from 5 kHz to 1.2 MHz. The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero cross time of the detected magnetic field waveform.展开更多
The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thick...The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thicknesses with the crystal size of about 15 nrn. The crystallite size during microforging was primarily determined by plastic deformation rather than fracturing and agglomeration. Unlike the general trend of coercivity reduction with annealing, the coercivity of the nanocrystalline flakes was slightly increased with increasing annealing temperature, which can be explained with the diffusion anisotropy of the magnetic moments resulting from the formation of Fe-atoms pairs. The magnetic rernanence （Mr） of the planar nanocrystalline flakes was measured to be about 26% of the saturation magnetization （Ms）, a significant increase from 2% of the initial amorphous precursor.展开更多
In the present study, the contribution of the gas bubbling filtration （GBF） process to the microporosity variation, microstructural characteristics and tensile properties of A356 aluminium alloy was investigated. Th...In the present study, the contribution of the gas bubbling filtration （GBF） process to the microporosity variation, microstructural characteristics and tensile properties of A356 aluminium alloy was investigated. The test specimens were fabricated through gravity casting in terms of the process variables： the degassing time, the impeller rotation and the aperture size of gas inlet hole. The density measurement and scanning electron microscope fractography analyses were conducted to evaluate the variation of the volumetric porosity and fractographic porosity with the GBF process, respec- tively. The fractographic porosity of the specimens can be minimised under specific GBF conditions in terms of the buoyant velocity and the absorbing capacity of gas bubbles, the inclusion of oxide films, whereas the volumetric porosity can be wholly reduced on the lapse of degassing time. The ultimate tensile strength （UTS） and elongation at optimal conditions were improved to approximately 30 MPa and 1.5% compared with no GBF treatment. Even though an extension of the degassing time and/or excessive stirring action of the melt may induce the inclusion of bifilm oxides and the increase of fractographic porosity, the tensile properties of over-treated specimens were maintained to a level which is similar to those that did not undergo GBF treatment due to the grain refinement accompanying with the GBF process. In addition, the defect susceptibility of UTS and elongation to microporosity variation could be remarkably improved at an optimal GBF condition.展开更多
文摘An integrated optimization design was described using multilevel decomposition technique on the base of the parametric distribution and independent axiom at the stages of lower level. Based on Pareto optimum solution, the detailed parameters at lower level can be defined into the independent axiom. The suspension design was used as the simulation example. In an axiomatic design for the optimization design, the uncoupled and decoupled designs between functional requirements and design parameters are generally needed. But using the design sensitivity(or screening) of design parameters, the approximate uncoupled design is developed on behalf of the decoupled and coupled designs. Successive design parameters were applied to the suspension of torsion beam axle. The structural performance increases by 18%. The kinematic and compliance performance increases by 6% within the feasible ranges.
基金Projects(2012-00094552012-0008302) supported by the National Research Foundation of Korea(NRF) Grant Funded by the Korea Government(MEST)
文摘Aluminium trihydrate(ATH) is being extensively added to polypropylene(PP) to make a fire retardant composite. Blends of PP/ATH composite are more fire resistant as compared to pure PP. Percentage proportion of both the constituents in the final composite depends upon the application. Improvement in the fire retardant properties of such composites have been studied and published in literature but effects on mechanical strength have not been addressed. The effect of concentration of ATH on the strength of PP/ATH composite was presented. The tensile, flexural and fracture properties were studied and discussed. Experimental tests, ASTM analytical formulae and finite element approach were used. It has been found that increase in ATH has an inverse effect on the mechanical strength.
文摘A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strikes. A planar shutter type electric field mill （EFM） with a rotating vane is studied to measure the electric field. From a calibration experiment, the sensitivity of the EFM was adjusted to 0.15 V/kV/m, and this covers the ranges from 200 V/m to 20 kV/m. Magnetic field waveform is detected by a crossed loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges from 5 kHz to 1.2 MHz. The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero cross time of the detected magnetic field waveform.
基金supported by INHA Technical College under a 2010-Research Grant
文摘The effect of microforging on the processing of nanocrystalline FeSiB alloy flakes was studied in terms of microstructure and magnetic properties. The flakes microforged from amorphous precursor showed submicron thicknesses with the crystal size of about 15 nrn. The crystallite size during microforging was primarily determined by plastic deformation rather than fracturing and agglomeration. Unlike the general trend of coercivity reduction with annealing, the coercivity of the nanocrystalline flakes was slightly increased with increasing annealing temperature, which can be explained with the diffusion anisotropy of the magnetic moments resulting from the formation of Fe-atoms pairs. The magnetic rernanence （Mr） of the planar nanocrystalline flakes was measured to be about 26% of the saturation magnetization （Ms）, a significant increase from 2% of the initial amorphous precursor.
基金supported by the General Researcher Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science and Technology(2010-0022284)+1 种基金supported by the Development Program for Industrial Core-Technology through the Korea Evaluation Institute of Industrial Technology(KEIT)funded by the Ministry of Trade,Industry and Energy(10048817)
文摘In the present study, the contribution of the gas bubbling filtration （GBF） process to the microporosity variation, microstructural characteristics and tensile properties of A356 aluminium alloy was investigated. The test specimens were fabricated through gravity casting in terms of the process variables： the degassing time, the impeller rotation and the aperture size of gas inlet hole. The density measurement and scanning electron microscope fractography analyses were conducted to evaluate the variation of the volumetric porosity and fractographic porosity with the GBF process, respec- tively. The fractographic porosity of the specimens can be minimised under specific GBF conditions in terms of the buoyant velocity and the absorbing capacity of gas bubbles, the inclusion of oxide films, whereas the volumetric porosity can be wholly reduced on the lapse of degassing time. The ultimate tensile strength （UTS） and elongation at optimal conditions were improved to approximately 30 MPa and 1.5% compared with no GBF treatment. Even though an extension of the degassing time and/or excessive stirring action of the melt may induce the inclusion of bifilm oxides and the increase of fractographic porosity, the tensile properties of over-treated specimens were maintained to a level which is similar to those that did not undergo GBF treatment due to the grain refinement accompanying with the GBF process. In addition, the defect susceptibility of UTS and elongation to microporosity variation could be remarkably improved at an optimal GBF condition.
