Advanced Materials Research Vol. 658

Abstract: This paper gives a description of an experimental study on the ultrasonic welding of metals. In ultrasonic metal welding, high frequency vibrations are combined with pressure to join two materials together quickly and securely, without generating large amount of heat. Horn, a key part of ultrasonic welding machine, should be designed very accurately to get the natural frequencies and vibration mode required. In this study, a horn is designed and developed for ultrasonic welding of Cu sheets. The tensile strength of welded parts is investigated for evaluation of weldability. Experimental parameters of welding test is set as follows; welding time 0.4s ~ 3.4sec. and vibration amplitude 40%, 60%, 80% and welding pressure 1.5bar, 2.0bar, 2.5bar. Samples are Cu sheets of 0.1mm thickness. Experimental results showed that the tensile strength increase as welding parameters increase, but when welding pressure is excessive, the tensile strength decrease due to fracture of the Cu sheets caused by over-welding. These results could be successfully applied for ultrasonic metal welding in various fields of manufacturing industry.

Abstract: The artificial neural network (ANN) and Orthogonal experimental design was applied in the research of main process parameters of electroforming Ni-Fe microstructure. In order to obtain the suitable parameters of the deposit, an ANN with 3 layers was built and trained based on orthogoality experiment using back propagation algorithm. The characteristics of the micro electroforming process were analysed systematically. And the optimal process parameters to obtain Ni-20% Fe deposition was as following: FeSO4•7H20 concentration: 5.5 g/L; PH value of the solution: 2.5; current density: 3.5 A/dm2; electrolyte temperature: 55 °C. The results indicate that the Ni-Fe deposit is bright and compact. Electrodeposited Ni-20% Fe has a strong paramagnetic effect with the smallest value of remanence 0.036 mA•m2 and the coercivity: 0.187 kA/m. The Ni-Fe micro electroplating process for the fabrication of microstructure was optimised.

Abstract: The relationship between the composition, coating microstructure and electromagnetic properties of electroforming Ni-Fe alloys was studied in this paper. And the optimal process parameters to obtain Ni-20%Fe deposition was as following: FeSO4•7H20 concentration was 6 g/L; PH value of the solution was 2.5; current density was 3.5 A/dm2; electrolyte temperature 55 °C. The results indicate that the Ni-Fe deposit is bright and compact, the crystal-planes of the plating were (111), (220) and (200). Electrodeposited Ni-20%Fe has a strong paramagnetism effect with the smallest remanence of 0.5 emu, The coercivity show a monotonic decrease with increasing Fe content in deposit, which proved that the electroformed Ni-20%Fe alloy has good electromagnetic property and could be used in MEMS actuator manufacturing.

Abstract: Four kinds of slow-release carbon source composite materials were prepared and used as carbon source and biofilm attachment carrier for groundwater nitrate pollution bioremediation. Their performances were detected through static and continuous experiments. The results showed that: In the static experiments, HB20 and HB40 had general release carbon ability, their CODMn were 5.42 and 12.83 mg/L respectively; In the continuous experiments, NO3-N removal rate of HLE decreased from 57.9% to 13.1% within 30 days, the denitrification endurance was not good. Organic carbon source can be released continuously by HBE which had the best denitrifying effect. In the operation of 66 days, above 96.0% NO3-N was removed and NO2-N level was below 0.02mg/L when influent NO3-N =30.0mg/L and HRT=24h. HBE was the most suitable carbon source carrier material which was used in groundwater nitrate pollution bioremediation.

Abstract: Bone machining processes are often performed in orthopaedic surgery and dental implantation, yet its analytical study is lacking. Towards contributing analysis on bone machining, this study reviews available references on orthogonal machining of bones. Considering the allowable limit in temperature and duration during bone machining to avoid thermal necrosis, machining temperature and forces are the machining responses of interest. Machining conditions (cutting speed, depth of cut, cooling method, tool geometry, and cutting direction) are analyzed in term of their effect to those machining responses.

Abstract: In this paper, the finite element method (FEM) was applied to predict the local buckling behavior and the debond propagation in honeycomb sandwich panels with face-core debond under in-plane compressive load. The finite element model of the sandwich panel was built, the cohesive element was used to model the adhesive between faces and core, the influence of the debond shape and size on the failure mode, critical buckling load and residual compressive strength of the sandwich panels was investigated, the rule of the damage propagation was summarized. The compression strength of the sandwich panels with through-width face-core debond decreases with increasing debond length. For the panels with central circular debond, when the diameter is less than 15mm, the panels will failure by global buckling and the debond will not grow. When the diameter is greater than 15mm, the panels will failure by local buckling and the critical load strongly decreases with increasing debond diameter. In addition, the direction of debond growth is predominantly perpendicular to the applied load.

Abstract: We have demonstrated several MZIs based on two spaced 3-dB LPFGs with different interference lengths in conventional SMFs fabricated in air by femtosecond laser pulses with the duration of 200 fs and the repetition rate of 250 kHz. Experimental results show that the average fringe spatial period increases with the resonance wavelength, while decreases with the interference length in approximately inverse proportion. The dominant cladding mode interfering with core mode has been calculated. The MZI sensitivity on temperature, refractive index and strain with a length of 16mm has also been investigated.

Abstract: Tungsten organometallic sol and tungsten organometallic-PANi sol were deposited onto SiO2 coated silicon substrates by a sol-gel spin coating technique. SEM studies on tungsten organometallic film show that it consists of many hollows compared to tungsten organometallic doped 1 wt.% PANi while SEM studies on tungsten organometallic doped 4 wt.% PANi show the sample became porous and agglomerated. Tungsten organometallic sensor was responsive towards isopropanol vapour at room remperature with sensitivity of 13.03%. Although the sensitivity of tungsten organometallic-PANi is lower than undoped PANi sensor, the hybrid sensor exhibited good reversibility meanwhile response of undoped PANi sensor decrease extremely with time. The small amount of PANi doping into tungsten organometallic sol improved the sensing properties of the sensor in terms of reversibility and recovery time.

Abstract: In this paper, the failure modes of the honeycomb sandwich structure under uniaxial compressions after impact (CAI) are analyzed through experiments and Finite Element Method (FEM). Three cases of impact damage location, two cases of impact damage depth and adhesive properties are investigated by the comparisons of corresponding non-destructive structure. Several conclusions are drawn: the failure modes and the initial damage positions obtained from experiments and FEM simulations are almost the same; the location of impact damage may affect the overall loading capabilities of the sandwich structure, whose decreasing rate peaks when the damage is at the top surface and drops when the damage is at the marginal area; different adhesive layer property of interface may lead to the failure mode change, that is, instead of honeycomb core failure, interlaminar failure will occur when the fracture energy of the adhesive layer is low; the damage level and risky location of the structure will vary relevant to the impact energy.

Abstract: Deformation twinning is widely observed in face-centered cubic (fcc) metals. The stress for activating twinning is an important issue to be solved. We presented an expression linking to twinning stress based on the total energy change associated with the formation of a twinning nucleus according to the classical nucleation theory. We assume there exist no energy fluctuations to overcome the nucleation barrier. The expression can predict the twinning stress for fcc metals, which is in excellent agreement with experimental results with simple form. Finally, we introduce a measure twinability to quantify the propensity of fcc metals to twin as opposed to cross-slip.