Applied Mechanics and Materials Vols. 66-68

Abstract: As-welded AA6061 Al alloy using Al-Si-Mg (ER 4043) filler metal was subjected to oxidationexposure in flowing air gas for 40hrs at 600oC at a total pressure of approximately 1 atm. SEM andEDAX were chosen to characterize the morphology microstructure of oxide formation on welded jointafter oxidation process. Different oxide morphology were found on parent and fusion metal due to thedifferences of the alloying element. The morphology of the oxide shows the protection oxide surfacewere developed on parent metal while non-protective oxide formed on fusion metal.

Abstract: The most popular non-ferrous melting in Thailand is melted by using oil crucible furnace however since in the year 2004 we have faced the oil crisis situation oil price became expensive that made the production cost was rising up so we have designed and constructed new one crucible furnace which used LPG gas to be fuel the capacity of furnace is 40 kilograms for aluminium melting after that we tested to find out the melting rate and fuel consumption for cost comparison between diesel oil using and LPG gas using and we have got the result that new LPG furnace could save production cost more than diesel oil furnace it mean could make more profit for producers.

Abstract: In this paper was analyzed on the architecture of PC NC system, and was studied design ideas of PC+I/O software-based structure and its exist advantages, and was analyzed with some key technology solutions, comparative study, and put forward the framework of software and hardware platform design based on PC+I/O software-based structural CNC system.

Abstract: From March to December 2005 NMHCs were measured in an urban site in Guangzhou. Air samples were collected with canister and analyzed for HMHCs by GC-MSD/FID after cryogenic pre-concentration. Mixing ratios of Alkanes accounted for over 43% in total NMHCs in each month while the shares of aromatic hydrocarbons were 19-28%. In average ethyne was the most abundant compound (5.46 ppbv), followed by propane (4.49 ppbv) and toluene (4.19 ppbv). Seasonal variations of most anthropogenic hydrocarbons revealed higher mixing ratios in autumn-winter than in spring-summer. Isoprene, on the contrary, exhibited the the highest levels in summer and the lowest in spring. Anthropogenic NMHCs typically showed a first peak around 8:00 local time in morning and 20:00 local time in the evening, while isoprene revealed a different bimodal diurnal pattern.

Abstract: Ca-Mg-Al hydrotalcite-like compounds (CaMgAl-HTLcs) were synthesized by a hydrothermal method, and characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and differential thermal analysis (DTA) techniques. The effects of the medium pH value, the molar ratio of the raw materials, the reaction temperature and the reaction time on the structure of CaMgAl-HTLcs were studied. The results showed that increasing treatment temperature and reaction time could improve the crystallinity and monodispersity of hydrotalcite-like compound particles. And well-defined CaMgAl-HTLcs could be prepared at a pH value of 10~11 with n(Zn+Mg+Ca):n(Al) =2. The products synthesized were applied to PVC to improve the thermal stability of PVC.

Abstract: Uniaxial tensile deformation behavior of 5A90 aluminium-lithium alloy sheet is investigated in the hot forming with the temperature range of 200-450°C and strain rate range of 0.3×10^-3-0.2×10^-1s^-1. It is found that the flow stress of 5A90 Al-Li alloy in uniaxial tension increase with increasing strain rate and decrease with increasing temperature, however, the tendency of total elongation is just the reverse, and the optimum forming temperature is 400°C. The strain rate sensitivity index (m-value) remarkably increases with increasing temperature for a given strain rate. It is shown that 5A90 Al-Li alloy sheet displays the sensitivity to the strain rate at elevated temperatures. For a given strain rate, the strain hardening index (n-value) decreases with increasing temperature, whereas the n-value increases above 350°C. The constitutive equation of stress, strain and strain rate for 5A90 Al-Li alloy at any temperature is obtained by fitting the experimental data, which gave a good flow stress model for the FEM simulation of hot forming.

Abstract: The cylindrical cup drawing of 5A90 Aluminum-Lithium alloy sheets at various forming conditions was studied by both the experimental approach and the finite element analysis. The uniaxial tensile tests and forming limit tests of 5A90 Al-Li alloy sheets at various temperatures were first carried out. The tests results were then employed in the finite element simulations to investigate the effects of process parameters, such as forming temperature, holder force, and die corner radius, on the formability of cylindrical cup drawing with 5A90 sheets. In order to validate the finite element analysis, the corresponding deep drawing tests were also carried out. It is shown that the simulation results are in qualitative agreement with the experimental observations. The optimal forming temperature, diameter of blank, holder force, punch radius and die corner radius were then determined for the cylindrical cup drawing of 5A90 sheets, and the limit drawing ratio (LDR) reached 2.4 in the optimal parameter conditions.

Abstract: The finite element model of a 7075-T7410 straight attachment lug is built by using the finite element software ANSYS, a cosine distribution pin-bearing pressure is applied on the surface of the pin-hole as a boundary condition. The stress intensity factor (SIF) expression for the straight attachment lug with a single through-the-thickness crack and subjected to an axial pin-load is determined by studying on the effect of the geometric parameters (the dimensionless crack length a/R₁，the ratio of outer radius to inside radius R₂/R₁ and the inside radius R₁) on SIF value. The fatigue crack growth velocity (da-dN) and the stress intensity factor’s amplitude (ΔK) is calculated by the SIFs equations to get the values of the Paris constants, offering an analytical method for establishment of the fatigue crack growth model of the typical straight lugs. The paper can be helpful in assessing and designing damage tolerant attachment lugs.

Abstract: A new type of swelling solution is developed, which is applied for the pre-treatment of plating-through-hole (PTH) of print circuit board (PCB) made up of high Tg epoxy resin substrates. The results show that the best formula is 144 organic esters 200g/L and hexylene glycol 2g/L. The treatment temperature and processing time is 60°C and 6min, respectively. Under the optimal conditions, the residue caused by drilling can be removed completely through the process including swelling, oxidation and neutralization.

Abstract: To study life differences between pre-corrosion fatigue and corrosion-fatigue test, LY12CZ standard specimens are selected in pre-corrosion fatigue test to get the C(t) curve at first. Then, combining with Miner linear cumulative damage theory, theoretical fatigue life is calculated by simulated corrosion-fatigue interactive process. Compared with actual corrosion-fatigue interactive test, theoretical life is rather conservative. Afterwards, a modified model based on C(t) curve method and actual interactive test at different periods of specific flight strength is established. The result shows that the modified C(t) curve method is in good agreement with corrosion-fatigue interactive test.