Surface modification of titanium and titanium alloys: Technologies, developments, and future interests

Drilling of glass fibre reinforced plastic (GFRP) composite is substantially different from metallic materials due to its mechanical properties. The drilling of this material may generate delamination of drilled holes on workpiece. The purpose of this paper is to investigate the influence of the cutting parameters, such as cutting speed and feed rate, and point angle on delamination produced when drilling a GFRP composite. The damage generated associated with drilling GFRP composites were observed, both at the entrance and the exit during the drilling. Hence it is essential to obtain optimum cutting parameters minimizing delamination at drilling of GFRP composites. Moreover, this paper presents the application of Taguchi method and analysis of variance (ANOVA) for minimization of delamination influenced by drilling parameters and drill point angle. The optimum drilling parameter combination was obtained by using the analysis of signal-to-noise ratio. The conclusion revealed that feed rate and cutting speed were the most influential factor on the delamination, respectively. The best results of the delamination were obtained at lower cutting speeds and feed rates.

Review: Optimization of cutting parameters on delamination based on Taguchi method during drilling of GFRP composite

Hydrothermal processing of hydroxyapatite nanoparticles—A Taguchi experimental design approach

An efficient two dimensional T-A formulation based approach is proposed to calculate the electromagnetic characteristics of tape stacks and coils made of second generation high temperature superconductors. In the approach, a thin strip approximation of the superconductor is used in which the superconducting layer is modeled as a 1-dimensional domain. The formulation is mainly based on the calculation of the current vector potential T in the superconductor layer and the calculation of the magnetic vector potential A in the whole space, which are coupled together in the model. Compared with previous T-based models, the proposed model is innovative in terms of magnetic vector potential A solving, which is achieved by using the differential method, instead of the integral method. To validate the T-A formulation model, it is used to simulate racetrack coils made of second generation high temperature superconducting (2G HTS) tape, and the results are compared with the experimentally obtained data on the AC loss. The results show that the T-A formulation is accurate and efficient in calculating 2G HTS coils, including magnetic field distribution, current density distribution, and AC loss. Finally, the proposed model is used for simulating a 2000 turn coil to demonstrate its effectiveness and efficiency in simulating large-scale 2G HTS coils.

A finite element model for simulating second generation high temperature superconducting coils/stacks with large number of turns

This investigation presents the use of Taguchi and response surface methodologies for minimizing the burr height and the surface roughness in drilling Al-7075. The Taguchi method, a powerful tool to design optimization for quality, is used to find optimal cutting parameters. Response surface methodology is useful for modeling and analyzing engineering problems. The purpose of this paper was to investigate the influence of cutting parameters, such as cutting speed and feed rate, and point angle on burr height and surface roughness produced when drilling Al-7075. A plan of experiments, based on L27 Taguchi design method, was performed drilling with cutting parameters in Al-7075. All tests were run without coolant at cutting speeds of 4, 12, and 20 m/min and feed rates of 0.1, 0.2, and 0.3 mm/rev and point angle of 90°, 118°, and 135°. The orthogonal array, signal-to-noise ratio, and analysis of variance (ANOVA) were employed to investigate the optimal drilling parameters of Al-7075. From the analysis of means and ANOVA, the optimal combination levels and the significant drilling parameters on burr height and surface roughness were obtained. The optimization results showed that the combination of low cutting speed, low feed rate, and high point angle is necessary to minimize burr height. The best results of the surface roughness were obtained at lower cutting speed and feed rates while at higher point angle. The predicted values and measured values are quite close to each other; therefore, this result indicates that the developed models can be effectively used to predict the burr height and the surface roughness on drilling of Al-7075.

Modeling and optimization of burr height in drilling of Al-7075 using Taguchi method and response surface methodology

Electrodeposition of copper on titanium wires: Taguchi experimental design approach

In this paper, a 220-V resistive superconducting fault current limiter (SFCL) prototype is built and tested under different prospective fault currents, which vary from 0.8 to 7.4 kA. A 2D superconductor model is integrated into an experimental circuit model in COMSOL to simulate the performance of the SFCL prototype in the experimental system in fault tests. In the simulation, a new E-J relationship is proposed to enhance the convergence of calculation. Comparison between simulation results and experimental results shows that the proposed model performs well in simulating current limiting performance of SFCL in experimental system in case of fault.

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Modeling and Experiment of the Current Limiting Performance of a Resistive Superconducting Fault Current Limiter in the Experimental System

Evaluation of epoxy cure in magnet impregnation is an important task because the final mechanical and electrical characteristics depend upon how the curing process was done. Usually the evaluation of curing scheme relies on thermal analysis methods, mainly the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In spite of their sensitivity and reliability, these methods have difficulties to evaluate fast curing of thermoset polymers. They also do not allow the in-situ monitoring of the cure of epoxy during impregnation of superconducting devices. The dielectric thermal analysis (DETA) is an analytical method commonly used to monitor in-situ the fabrication of polymer-matrix composite materials by the resin transfer molding (RTM) process in which the rheological and calorimetric parameters are continuously evaluated during the curing stage and the response signal is used to control the process. In this work we present the evaluation of dielectric characteristics during the cure of epoxy resins employed in the impregnation of electric and superconducting devices. The dielectric analysis was performed imposing a 2 V amplitude signal with fixed frequency of 120 Hz on a sample connected as a capacitor in a RC equivalent circuit. The epoxy is inserted as a dielectric medium within a parallel plate capacitor. The output signal is measured by a lock-in amplifier and the complex impedance is evaluated against the time and temperature of epoxy cure. The results show a very consistent correlation between the sample impedance signal and the reaction extent as well with viscosity versus temperature evolution in the pre-gelation stage of cure.

Monitoring the epoxy curing by the dielectric thermal analysis method

The joint process between tapes of coated conductors is a critical issue for the most of the applications of high temperature superconductors (HTS). Using different fabrication techniques joints of YBCO coated superconductors were prepared and characterized through electrical measurements. For soldering material low melting point eutectic alloys, such as In-Sn (m.p. 116degC) and Sn-Pb (m.p. 189degC) were selected to prepare lap joints with effective length between 1 to 20 cm. The splice resistance and the critical current of the joints were evaluated by I-V curve measurements with the maximum current strength above the critical current, in order to evaluate the degree of degradation for each joint method. Pressed lap joints prepared with tapes without external reinforcement presented low resistance lap joint nevertheless some critical current degradation occurs when strong pressing is applied. When mechanical pressure is applied during the soldering process we can reduce the thickness of the solder alloy and a residual resistance arises from contributions of high resistivity matrix and external reinforcement. The lap joints for reinforced tape were prepared using two methods: the first, using ldquoas-suppliedrdquo tape and the other after reinforcement-removal; in the latter case, the tapes were resoldered using Sn-Pb alloy. The results using several joint geometries, distinct surface preparation processes and different soldering materials are presented and analysed. The solder alloy with lower melting point and the longer joint length presented the smallest joint resistance.

Evaluation of Electrical Properties of Lap Joints for BSCCO and YBCO Tapes

A fault current limiter (FCL) based on an arrangement of parallel connected high temperature superconducting tapes constituting a limiter element was designed and tested in 220 V line for a fault current peak between 1 kA to 2 kA. The limiter employed second generation (2G) HTS tapes of YBCO coated conductor reinforced with stainless steel. Four tapes were electrically connected in parallel with 0.4 m effective length per element wherein 16 elements connected in series constitutes a single-phase unit. The FCL performance was evaluated through over-current and current fault tests. Its recovery characteristics were used to design the shunt protection. The designed limiting ratio is 4 for 16 elements and the experimental result for one element showed a 20% limiting ratio. For the fault current test one element can withstand five cycles of fault without degradation. It was observed recovery times below 0.5 s under nominal load using a shunt resistance of 173 mOmega.

C.A. Baldan

Papers

Electrodeposition of copper on titanium wires: Taguchi experimental design approach

Modeling and Experiment of the Current Limiting Performance of a Resistive Superconducting Fault Current Limiter in the Experimental System

Monitoring the epoxy curing by the dielectric thermal analysis method

Evaluation of Electrical Properties of Lap Joints for BSCCO and YBCO Tapes

Fault Current Limiter Using YBCO Coated Conductor—The Limiting Factor and Its Recovery Time