• Journal of the Korean Institute of Gas
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• v.20 no.4
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• pp.78-84
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• 2016

In this work, finite element investigations were carried out to optimize reverse drawing process design for manufacture of high-capacity aluminum liner used in fuel cell vehicle. The tensile tests with aluminum alloy Al6061 annealed at $350^{\circ}C$ were carried out to obtain the flow stresses. In order to estimate more accurate flow stresses after necking, the flow stresses were estimated from the comparison of load vs. displacement curves which were obtained from experimental and simulation results of tensile tests. In case of finite element analyses of reverse drawing processes, it was focused on the effects of process designs such as punch and die designs, blank holding force, drawing ratio and the clearance between the punch and blank holder on the generation of wrinkle and fracture of the blank and partially heated punch. However, it was revealed that experimental results still show the fracture at the end of 2nd drawn cup, although partially heated punch is used. Nevertheless, the drawn cup can be used because the sufficient length of the drawn cup for the next flow forming process and spinning process was obtained.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.3
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• pp.169-175
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• 1976

A solvent extraction-atomic absorption spectrophotometry for determination of trace amount of cadmium, copper, lead and zinc and a flameless atomic absorption spectrophotometry for mercury in sea water were studied. The optimum pH range for solvent extraction was pH 4-7. A better solvent extraction efficiency was obtained with MIBK solvent than nitrobenzene, benzene, isoamylalcohol, n-buthylacetate. DDTC was more advantageous than APDC as chelating agent. The metals, chelated with DDTC and concentrated into MIBK by solvent extraction with a volume of $1\iota$ of sea water for cadmium, copper and lead, and 200m1 for zinc, were determined simultaneously by atomic absorption spectrophotometry. For mercury determination, 500ml of sea water was digested with permanganate-sulfuric acid and mercury( II ) was reduced by stannous chloride and aerated the solution with air pump until the absorbance reached a constant value. The precisions, in standard deviation, of these methods were 0.058ppb for cadmium, 0.084 ppb for copper, 0.44ppb for lead, 2.49ppb for zinc and 0.08 ppb for mercury. The sensitivities, expressed in $ppb/1\%$ absorption, were 0.058 ppb cadmium, 0. 15 ppb copper, 0.6 ppb lead, 1.2 ppb zinc and 0.01 ppb mercury respectively. No significant adsorption on the wall of polyethylene sample bottle occurred during 30 days of storing by acidification to pH 1.5 with nitric acid except zinc. Poor reproducibility was found for zinc with this method.