• Composites Research
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• v.20 no.3
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• pp.8-16
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• 2007

Bending collapse of light-weight square tubes used for vehicle structure components is a dominant failure mode in oblique collision and rollover of vehicles. In this paper bending performances of aluminum-GFRP hybrid tube beams were evaluated in relation with bending deformation behavior and energy absorption characteristics. Aluminum/GFRP hybrid tube beams fabricated by inserting adhesive film between prepreg and metal layer were used in the bending test. Failure mechanisms of hybrid tubes under a bending load were experimentally investigated to analyze the bending performance as a function of ply orientation and composite layer thickness. Ultimate bending moments and energy absorption capacity of hybrid tube beams were obtained from the measured load-displacement corves. It was found that aluminum/GFRP hybrid tubes could be converted to rather stable collapse mode showing excellent energy absorption capacity in comparison to the pure aluminum tube beams. In particular, the hybrid tube beam with $[0^{\circ}/90^{\circ}]s$ composite layer showed a large improvement by about 78% in energy absorption capacity and by 29% in specific energy absorption.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.378-381
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• 2008

The buckling behavior of cylindrical shape-memory alloy and aluminum tube is investigated at room temperature using a split Hopkinson pressure bar and an Instron hydraulic machine with a specially designed recording system. The shape-memory alloy at superelastic property regime buckles gradually in quasi-static loading, and fully recovers upon unloading. However, the buckling of aluminum tube is sudden and catastrophic, and shows permanent deformation. This gradual buckling of shape-memory alloy is associated with the forward and reverse transformation of stress-induced martensite and seems to have a profound effect on the unstable deformation of tube structures made from shape-memory alloy.

• Imaging Science in Dentistry
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• v.53 no.3
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• pp.217-220
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• 2023

Purpose: This pilot study was conducted to evaluate half-value layer (HVL) measurements obtained using a semiconductor dosimeter for intraoral radiography. Materials and Methods: This study included 8 aluminum plates, 4 of which were low-purity (less than 99.9%) and 4 high-purity (greater than 99.9%). Intraoral radiography was performed using an intraoral X-ray unit in accordance with the dental protocol at the authors' affiliated hospital: tube voltage, 60 kVp and 70 kVp; tube current, 7 mA; and exposure time, 0.10 s. The accuracy of HVL measurements for intraoral radiography was assessed using a semiconductor dosimeter. A simple regression analysis was performed to compare the aluminum plate thickness and HVL in relation to the tube voltage (60 kVp and 70 kVp) and aluminum purity (low and high). Results: For the low-purity aluminum plates, the HVL at 60 kVp (Y) and 70 kVp (Y) was significantly correlated with the thickness of the aluminum plate (X), with Y=1.708+0.415X (r=0.999, P<0.05) and Y=1.980+0.484X (r=0.999, P<0.05), respectively. Similarly, for the high-purity aluminum plates, the HVL at 60 kVp (Y) and 70 kVp (Y) was significantly correlated with the plate thickness(X), with Y=1.696+0.454X (r=0.999, P<0.05) and Y=1.968+0.515X (r=0.998, P<0.05), respectively. Conclusion: This pilot study examined the relationship between aluminum plate thickness and HVL measurements using a semiconductor dosimeter for intraoral radiography. Semiconductor dosimeters may prove useful in HVL measurement for purposes such as quality assurance in dental X-ray imaging.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.311-320
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• 2023

Recently, lightweight of automotive parts has been required to solve environmental problems caused by global warming. Accordingly, research and development are proceeded on manufacturing of parts using aluminum that can replace steel for lightweight of the automotive parts. In addition, high strength aluminum can be applied to body parts in order to meet both requirements of lightening and improving crash safety of vehicle. In this study, hot blow forming of roof side rail is employed to manufacturing of the automotive parts with high strength aluminum tube. In hot blow forming, longer forming times and excessive thinning can be occurred as compared with conventional manufacturing processes. So optimization of process conditions is required to prevent excessive thinning and to uniformize thickness distribution with fast forming time. Mechanical properties of high strength aluminum are obtained from tensile test at high temperature. These properties are used for finite element(FE) analysis to investigate the effect of strain rate on thinning and thickness distribution. Variation of thickness was firstly investigated from the result of FE analysis according to tube diameter, where the shapes at cross section of roof side rail are compared with allowable dimensional tolerance. Effective tube diameter is determined when fracture and wrinkle are not occurred during hot blow forming. Also FE analysis with various pressure-time profiles is performed to investigate the their effects on thinning and thickness distribution which is quantitatively verified with thinning factor. As a results, optimal process conditions can be determined for the manufacturing of roof side rail using high strength aluminum.

• Progress in Medical Physics
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• v.6 no.2
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• pp.3-12
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• 1995

A 50 $\mu\textrm{m}$ thick niobium filter and its quantitatively determined aluminum equivalent filter were evaluated for effects on entrance skin dose, image quality, and x-ray tube loading for three different tube voltages in radiology. There was no significant difference in the reducion in entrance skin dose and increase in tube loading between two filters while keeping radiographic contrast on the film. For the clinical use of the aluminum equivalent filter as an alternative to the niobium filter in radiology, aluminum equivalent filter thickness at the mid energy range of radiology, 90 kVp, was measured and the filter was applied to the other kVp values, 73 and 125 kVps, to evaluate the effect on the entrance skin dose and tube loading. There was no significant difference between two filter cases at the selected kVp. The aluminum filter with equivalent thickness can be used as an inexpensive alternative to the niobium filter.

• Korean Journal of Materials Research
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• v.23 no.11
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• pp.607-612
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• 2013

A powder in sheath rolling method was applied to the fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A 6061 aluminum alloy tube with outer diameter of 31 mm and wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powder and CNTs with a volume content of 5% was filled in the tube by tap filling and then processed to an 85% reduction using multi-pass rolling after heating for 0.5 h at $400^{\circ}C$. The specimen was then further processed at $400^{\circ}C$ by multi-pass hot rolling. The specimen was then annealed for 1 h at various temperatures that ranged from 100 to $500^{\circ}C$. The relative density of the 5vol%CNT/Al composite fabricated using powder in sheath rolling increased with increasing of the rolling reduction, becoming about 97% after hot rolling under 96 % total reduction. The relative density of the composite hardly changed regardless of the increasing of the annealing temperature. The average hardness also had only slight dependence on the annealing temperature. However, the tensile strength of the composite containing the 6061 aluminum sheath decreased and the fracture elongation increased with increasing of the annealing temperature. It is concluded that the powder in sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.589-598
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• 2004

Flow condensation heat transfer coefficients (HTCs) of R22 and R134a were measured on a horizontal 9 hole aluminum multi-channel tube. The main test section in the refrigerant loop was made of a flat multi-channel aluminum tube of 1.4 mm hydraulic diameter and 0.53 m length. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in the vapor qualities of 0.1∼0.9 at mass flux of 200∼400 kg/$m^2$s and heat flux of 7.3∼7.7 ㎾/$m^2$ at the saturation temperature of 4$0^{\circ}C$. All popular correlations in single-phase subcooled liquid and flow condensation originally developed for large single tubes predicted the present data of the flat tube within 20% deviation when effective heat transfer area is used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Thermal insulation for the outer tube section surrounding the test tube for the transport of heat transfer fluid is very important in fluid heat-ing or cooling type heat transfer experimental apparatus.

• Journal of Powder Materials
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• v.21 no.1
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• pp.50-54
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• 2014

A powder-in-sheath rolling method was applied to a fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A STS304 tube with an outer diameter of 34 mm and a wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powders and CNTs with the volume contents of 1, 3, 5 vol was filled in the tube by tap filling and then processed to 73.5% height reduction by a rolling mill. The relative density of the CNT/Al composite fabricated by the powder-in-sheath rolling decreased slightly with increasing of CNTs content, but exhibited high value more than 98. The grain size of the aluminum matrix was largely decreased with addition of CNTs; it decreased from $24{\mu}m$ to $0.9{\mu}m$ by the addition of only 1 volCNT. The average hardness of the composites increased by approximately 3 times with the addition of CNTs, comparing to that of unreinforced pure aluminum. It is concluded that the powder-in-sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1686-1694
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• 2003

The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.247-250
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• 2005

The need for improved fuel efficiency, weight reduction has motivated the automotive industry to focus on aluminum alloys as a replacement for steel-based alloy. To cope with the needs for high structural rigidity with low weight, it is forecasted that substantial amount of cast components will be replaced by tubular parts which are mainly manufactured by the extruded aluminum tubes. The extrusion process is utilized to produce tubes and hollow sections. Because there is no weld seam, the circumferential mechanical properties may be uniform and advantageous for hydroforming. However the possibility of the occurrence of a surface defect is very high, especially due to the temperature increase from forming at high pressure when it comes out of the bearing and the roughness of the bearing, which cause the surface defects such as the dies line and pick-up. And when forming a extruded aluminum tube, the free surface of the tube becomes rough with increasing plastic strain. This is well known as orange peel phenomena and has a great effect not only on the surface quality of a product but also on the forming limit. In an attempt to increase the forming limit of the tubular specimen, in the present paper, surface asperities generated during the hydroforming process are polished to eliminate the weak positions of the tube which lead to a localized necking. It is shown that the forming limit of the tube can be considerably improved by simple method of polishing the surface roughness during hydroforming. And also the extent of the crack propagation caused by dies lines generated during the extrusion process is evaluated according to the deformed shape of the tube.