An approach to eliminate stepped features in multistage incremental sheet forming process: Experimental and FEA analysis

Incremental sheet forming (ISF) is a recently developed manufacturing technique. In ISF, forming is done by applying deformation force through the motion of Numerically controlled (NC) single point forming tool on the clamped sheet metal blank. Single Point Incremental sheet forming (SPISF) is also known as a die-less forming process because no die is required to fabricate any component by using this process. Now a day it is widely accepted for rapid manufacturing of sheet metal components. The formability of SPISF process improves by adding some intermediate stages into it, which is known as Multi-stage SPISF (MSPISF) process. However during forming in MSPISF process because of intermediate stages stepped features are generated. This paper investigates the generation of stepped features with simulation and experimental results. An effective MSPISF strategy is proposed to remove or eliminate this generated undesirable stepped features.     

Al-4.5Cu-2Mg合金应力-应变定位及分布的有限元分析（英文）

通过有限元方法分析不同加工路线和条件对Al-4.5Cu-2Mg合金微观形变行为的影响。合金采用4种不同的加工技术和条件制备,分别为有或无细化剂的常规重力铸造、流变铸造和SIMA工艺。以合金的光学显微结构作为代表性体积元(RVEs),采用两种不同的边界条件模拟合金在单轴载荷作用下的变形行为,最后将模拟的应力-应变行为与实验结果进行比较。结果表明,微观结构形态对应力和应变分布及承载能力具有显著影响,共晶相比α(Al)相能承受更高的载荷,具有较薄且均匀分布的共晶网络结构的球状α(Al)相能提供更好的应力和应变分布。因此,SIMA加工合金比其他技术加工合金拥有更好的应力和应变分布。最后,将该合金的模拟屈服强度与实验进行验证,结果具有较好的一致性。     

Development of a generative CAPP system for axisymmetric components for a job shop environment

Process planning is a function in a manufacturing organization that selects the manufacturing processes and parameters to be used to transform a part from its initial state to the final form according to the design specifications. It is a bridge between product design and product manufacturing. The activities of process planning include understanding the part specifications or product design data, selection of job material and tool, setup planning, sequencing the operations within a setup, determination of process parameters for each operation, and generation of process sheets. This paper outlines a method to develop a generative computer-aided process planning system for axisymmetric components for a job shop environment. A decision support system is used to perform semi-structured tasks such as setup planning and establishing precedence relationship among various operations.     

Study of chemiresistor type CNT doped polyaniline gas sensor

The composite thin films of polyaniline (Pani) with multiwall carbon nanotube (MWNT) and single wall carbon nanotube (SWNT) for hydrogen gas sensing application are presented in this paper. Polyaniline (Pani) was synthesized by chemical oxidative polymerization of aniline using ammonium persulfate in acidic medium. The SWNT and MWNT were doped in Pani in presence of champhor sulfonic acid (CSA) by solution mixing method. Thin films of CNT/Pani composites were prepared by spin coating method. Finally, the response of these composite films for hydrogen gas was evaluated by monitering the change in electrical resistance at room tempeature. It is observed that the SWNT/Pani and MWNT/Pani composite films show a higher response as compare to pure Pani. The structural and optical properties of these composite films have been characterised by X-ray diffraction (XRD) and UV–visible spectroscopy respectively. Surface morphology of these films has also been characterised by optical microscopy.     

Frequency dependent electrical transport properties of 4,4′,4″-tris(N-3-methylphenyl-N-phenylamine)triphenylamine by impedance spectroscopy

The frequency dependent ac conduction mechanism in 4,4′,4″-tris(N-3-methylphenyl-N-phenylamine)triphenylamine (m-MTDATA) has been studied as a function of applied bias and temperature. The Cole–Cole plot shows a slightly depressed semicircle indicating Debye type relaxation. This result has been explained by an equivalent circuit of the device designed as a two parallel resistor and capacitance network in series with contact resistance. The ac conduction studies under dc bias for hole only devices shows an increase in device conductivity with the increase in bias. The variation of bulk resistance with applied bias indicates Space Charge Limited Conduction (SCLC) mechanism for hole conduction. The hole mobility of the material has also been evaluated from SCLC as 8.859 × 10^?6 cm²/V s. The temperature dependent impedance studies show two activation energies indicating two different phase of the material with a phase transition at 235 K.     

Synthesis and characterization of soluble narrow band gap conducting polymers based on diketopyrrolopyrrole and propylenedioxythiophenes

A series of novel electro-active conjugated polymers containing 2,5-dialkyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-diones (DPPs) and 3,4-dihydro-3,3-dialkyl-2H-thieno[3,4-b][1,4]dioxepines (dialkyl-ProDOTs) were synthesized using Stille coupling reaction in presence of CuO. The molecular weights of the synthesized polymers were found to be in the range of 18,000–45,000. Incorporation of the electron deficient DPP units and the electron rich dialkyl-ProDOT units in the conjugated backbone leads to low band gap polymers. All the polymers were found to be highly soluble in most chlorinated organic solvents as well THF and toluene with excellent film forming properties. From the UV–vis spectra, the band gap of the polymers was determined as 1.40–1.42 eV which is lower than the poly(dialkylProDOT)s. From the electrochemical study, highest occupied molecular orbital (HOMO) energy levels of the synthesized polymers were found to be in the range of 5.54–5.51 eV. Because of such high HOMO level, the resulting polymers were found to be more oxidatively stable. Polymers are thermally stable till 325–346 °C with only 5% weight loss which was confirmed from thermogravimetric analysis (TGA). The polymers were found to be moderately conducting with maximum conductivity up to 0.2–6.0 S/cm.     

Investigations on synthesis of HfB2 and development of a new composite with TiSi2

This paper presents the results of investigation carried out on synthesis and densification of monolithic HfB₂ and the effect of TiSi₂ as sinter additive. Pure phase HfB₂ was prepared by boron carbide reduction of HfO₂ and hot pressed to full density with the addition of TiSi₂. Isothermal oxidation study of this composite was carried out at 850 °C up to 64 h. Formation of HfB₂ was seen at 1200 °C but pure HfB₂ was formed at a much higher temperature of 1875 °C in vacuum. Hot pressing of HfB₂ at 1850 °C and 35 MPa pressure gave a compact of 80% TD. Addition of TiSi₂ helped in achieving a much higher density at a lower temperature of 1600 °C and a pressure of 20 MPa. A fully dense composite of HfB₂ and TiSi₂ was obtained with 15% TiSi₂. Hardness and fracture toughness of this composite were 27.4 ± 1.9 GPa and 6.6 ± 0.2 MPa m^1/2, respectively. Considerable deflection was observed in the crack propagation in composites. Oxidation studies indicated the formation of HfO₂, SiO₂, TiO₂ and HfSiO₄ with some glassy phase and the composite with 15% TiSi₂ was seen to be completely covered with a protective glassy layer.     

On performance studies during micromachining of quartz glass using electrochemical discharge machining

The electrochemical discharge machining is a highly stochastic process involving a number of complex parameters. Controlling of these process parameters simultaneously to fetch the best possible performance is a difficult task. Determining an optimal parametric combination has become complex owing to interdependency of the parameters. In this work, the authors have made an attempt to establish the optimal combination of control parameters for machining of micro-channels on quartz glass. Taguchi’s standard orthogonal array (L ₉) with Grey relational analysis (GRA) approach was used to establish the optimal parametric conditions for reducing the Width overcut (WOC) of micro-channels and increasing the Material removal rate (MRR). In order to optimize MRR and WOC together, the optimal combination of the selected control variables was obtained using the GRA. The experimental results showed the effectiveness of the adapted method to indicate the performance of the electrochemical discharge machining process.

     

Arc characterization study for submerged arc welding of HSLA (API X80) steel

Journal of Mechanical Science and Technology - The load bearing capacity of weld is highly influenced by the mode of metal transfer which in turn is dependent on welding current and arc voltage....     

Adsorption of gold(III) from waste rinse water of semiconductor manufacturing industries using Amberlite XAD-7HP resin

Advanced hydrometallurgical separation processes are gaining significant importance for the recovery of gold from the aqueous solutions viz. leach liquor of waste electronics, plating material solutions, and waste wash water from electronic industries. In the present investigation, gold adsorption from the waste rinse water of semiconductor manufacturing industries is reported using Amberlite XAD-7HP. For experimental purposes, chloride waste rinse water that contained primarily Au (281 mg/ L) with trace amounts of Cu, Ni, Zn, Sn etc was used. Batch studies were carried out to optimize various process parameters, including contact time, acidity of solution, and resin dosage for the adsorption of gold from the above waste effluent. Adsorption of 92.25% gold was found from the waste solution within a contact time of 30 minutes at an aqueous to resin (A/R) ratio of 25 mL/g and an equilibrium pH of 0.63. In optimal conditions, the loading capacity of resin for gold was observed to be 58.82 mg of gold/g of resin. The gold adsorption phenomena were confirmed by the comparative FT-IR spectroscopic characterization studies of fresh resin and gold loaded resin. Elution tests were carried out for the elution of gold from the gold loaded resin using various ratio mixtures of acetone and 1.0 M HCl. An elution efficiency of 96.96% gold was achieved at an acetone-to-acid ratio of 9. In this condition, gold-enriched solution containing 7,240 mg gold/ L was obtained. The maximum elution of gold was found to be 99.33% using pure acetone in a contact time of 30 minutes. The data obtained will be useful to simulate the continuous gold adsorption process within a column.