• International journal of advanced smart convergence
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• v.4 no.1
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• pp.145-153
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• 2015

Friction Stir Welding (FSW) is a solid state welding that could successfully weld the difficult-to-weldmaterials such as an aluminum alloy. In this welding process, the stirrer of the welding tool is one of the important factors for producing the perfect sound joint that indicates the higher joint strength. So, this report aims to apply the friction stir welding using various stirrer geometries to weld the AA6063-T1 aluminum alloy butt joint, investigates the mechanical properties of the joint and then compares the mechanical properties with the microstructure of the joint. An experiment was started by applying the friction stir welding process to weld a 6.3 mm thickness of AA6063-T1 aluminum alloy butt joint. A study of the stirrer geometries effect such as a cylindrical geometry, a cone geometry, a left screw geometry and a right screw geometry at a rotational speed of 2000 rpm and a welding speed of 50-200 mm/min was performed. The mechanical properties such as a tensile strength and a hardness of the joint were also investigated and compared with the microstructure of the joint. The results are as follows. A variation of FSW Stirrer shape directly affected the quality AA6063-T1 aluminum alloy butt joint. A cylindrical stirrer shape and a cone stirrer shape produced the void defect at the bottom part of the weld metal and initiated the failure of the joint when the joint was subjected to the load during the tensile test. Left and right screw stirrer shapes gave the sound joint with no void defect in the weld metal and affected to increase the joint strength that was higher than that of the aluminum base metal.

• Preventive Nutrition and Food Science
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• v.17 no.4
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• pp.286-292
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• 2012

We investigated the effect of various cooking methods (boiling, steaming, stir-frying, and roasting) and three cooking times (5, 10, and 15 min) on the antioxidant properties of red pepper. Raw and cooked peppers were measured for proximate composition, ascorbic acid (AsA) content, total carotenoid content (TCC), total polyphenol content (TP), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities. Results showed that the proximate composition, AsA content, TCC, TP, and antioxidant activities were significantly (p<0.05) affected by the cooking procedure; the loss rate varied among individual compounds. Boiling and steaming significantly reduced AsA content (24.3~66.5%), TP (13.9~54.9%), and antioxidant activity (21.7~60.5%) in red pepper, while stir-frying and roasting slightly reduced AsA content (2.7~25.9%), TP (1.8~4.9%), and antioxidant activity (4.9~17.9%). The highest loss was observed after boiling, followed by steaming, roasting, and stir-frying. Stir-frying and roasting better preserved AsA content, TCC, TP, and antioxidant activity. In conclusion, dry-heat cooking methods such as stir-frying and roasting may be preferred to retain the nutrient compositions and antioxidant properties of red pepper.

• Transactions of Materials Processing
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• v.29 no.1
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• pp.11-19
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• 2020

For microstructural analysis of a friction stir welded (FSWed) joint of advanced high-strength steels, dual phase (DP) and complex phase (CP) steels, are studied. FSWed joints are successfully fabricated in the following four cases: (i) DP/DP; (ii) CP/CP; (iii) DP/CP, where the advancing side is DP and the retreating side is CP; (iv) CP/DP, where the advancing side is CP and the retreating side is DP. The stir zone (SZ) of (i) the DP/DP joint mainly consists of lath martensite, while the stir zone of (ii) the CP/CP joint consists not only of lath martensite but also of bainite. In the case of (iii) DP/CP and (iv) CP/DP, they exhibit a similar microstructure including acicular-shaped phases in the joints; however, cross-sections of the joints show differences in material mixing in each case. In (iv) the CP/DP joint, temperature towards the CP steel is sufficient to cause softening, thus leading to better mixing than that in (iii) DP/CP. The phases of the SZ in each of the four cases are formed by phase transformation during the FSWed process; however, the transformed phase volume fraction of CP steel is lower than that of DP steel, indicating that dynamic recrystallization occurs mainly in CP steel. The hardness values of the SZ are significantly higher than those of the base materials, especially, the SZ of (iii) the DP/CP joint has the highest value due to highest fraction of lath martensite.

• Journal of Welding and Joining
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• v.33 no.2
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• pp.8-13
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• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• Journal of the Korean Society of Radiology
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• v.8 no.5
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• pp.271-278
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• 2014

The purpose of this study is to know optimized fat suppression techniques for brachial plexus compared with STIR and SPAIR T1, T2 techniques. A total of 30 normal volunteers without brachial plexus disease were studied on a 3.0 T MRI scanner. As an analytical method, SNR, CNR, 4-point grading scale were evaluated by using three pulse sequences. As a quantitative analysis, the SNR, CNR for SPAIR T1 technique provided high value in branchial plexus roots (03.07, -2.25), branchial plexus trunks(06.70, 36.31)(p<0.05). As a qualitative Analysis, The visibility for delineation of brachial plexus, fat suppression, artifact was significantly better on SPAIR T1(3.2, 3.6, 3.4) technique(p<0.05).

• Journal of Welding and Joining
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• v.31 no.2
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• pp.16-20
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• 2013

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.22-28
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• 2007

The STIR(Signal Tracking & Illumination Radar) in KDX(Korean Destroyer Experimental) combat system acquires target from designating 3-D target information of surveillance radar (MW-08), and The performance of radar is decided by target acquisition time and accuracy of tracking loop because the STIR tracks automatically in accordance with tracking algorithm. In the view of ship, elements related with target acquisition time of the STIR can be various. In this paper the target acquisition time of the STIR is reduced by identifying the elements and suggesting the performance improvement method. The way of performance improvement is suggested through analysing main affecting factors. First, tracking algorism is required for analysis. Second, fitness of parameters that control elements related with acquisition distance is analyzed. And the third, accuracy of ship based sensors is analyzed. In conclusion, acquisition time against ship target can be advanced to 3 seconds from 10 seconds.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.94-99
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• 2019

Friction stir welding was first reported by TWI(The Welding Institute) in 1991, and this welding method has been rapidly used in various industrial areas such railway, automobile, aerospace and shipbuilding industry. Here, we study core characteristics of friction stir welding (FSW) applied to Al 6005-T6 extruded sheets, which is the typical alloy used for railway car bodies. With the fixed welding speed of 500 mm/min, the rotating tool speed was varied from 600 to 1800 RPM. The results of hardness measurement revealed that the hardness of nugget area is ~70% with respect to the parent material, and for the selected range of rotation speed, no clear dependence was observed and the hardness values close to the parent materials were achieved for the area located 5 mm away from the welding interface. The tension test shows that yield strength and tensile strength were slightly decreased with increasing RPM, with no observed difference for the elongation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.304-307
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• 2008

In order to evaluate the effect of permanent softening behavior on springback prediction, 2D-draw bending simulations were compared with experiments for friction stir welded DP590 steel sheets. To account fur the nonlinear hardening behavior, the combined isotropic-kinematic hardening law was utilized with and without considering the permanent softening behavior during reverse loading. Also, the non-quadratic orthotropic yield function, Yld2000-2d, was used to describe the anisotropic initial-yielding behavior of the base sheet while anisotropic properties of the weld zone were ignored for simplicity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.301-303
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• 2008

In order to investigate the influence of anisotropy on formability and also to obtain guidelines for the stamping process design in friction stir welded TWB (tailor welded blank), the aluminum ally 6111-T4 sheet was welded with three different types of combination: RD||RD, TD||RD and TD||TD (Here, RD and TD mean the rolling direction and transverse direction, respectively) and then hemisphere dome stretching and cylindrical cup drawing tests were carried out. In addition, the numerical analysis was performed to confirm the validity of experimental results. For the numerical analysis, the non-quadratic orthotropic yield function, Yld2004-18p was utilized to represent precise anisotropic properties.