Friction stir spot welding (FSSW) is a solid-state joining process and a rapidly growing dissimilar material welding technology for joining metallic alloys in the automotive industry. Welding tool shape and process conditions must be appropriately controlled to obtain high bonding characteristics. In this study, FSSW is performed on dissimilar materials AA5052-H32 aluminum alloy sheet and SPRC440 steel sheet, and the influence of the shape of joining tool and tool insertion depth during joining is investigated. A new intermetallic compound is produced at the aluminum and steel sheets joint. When the insertion depth of the tool is insufficient, the intermetallic compound between the two sheets did not form uniformly. As the insertion depth increased, the intermetallic compound layer become uniform and continuous. The joint specimen shows higher values of tensile shear load as the diameter and insertion depth of the tool increase. This shows that the uniform formation of the intermetallic compound strengthens the bonding force between the joining specimens and increases the tensile shear load.

The present research focuses on the tribological behavior of the AA5083 alloy-based hybrid surface composite using aluminosilicate and multi-walled-carbon nanotube through friction stir processing for automotive applications. The friction stir processing parameters (tool rotation and traverse speed) are varied based on full factorial design to understand their influence on the tribological characteristics of the developed hybrid composite. The surface morphology and composition of the worn hybrid composite are examined using a field-emission scanning electron microscope and an energy-dispersive x-ray spectroscope. No synergistic interaction is observed between the wear rate and friction coefficient of the hybrid composite plate. Also, adhesive wear is the major wear mechanism in both base material and hybrid composite. The influence of friction stir process parameters on wear rate and the friction coefficient is analyzed using the hybrid polynomial and multi-quadratic radial basis function. The models are utilized to optimize the friction stir processing parameters for reducing the rate of wear and friction coefficient using multi-quadratic RBF algorithm optimization.

To improve the thermophysical properties of Al alloy for thermal management materials, the Cu-coated carbon fibers (CFs) were used as reinforcement to improve the thermal conductivity (TC) and the coefficient of thermal expansion (CTE) of Al-12Si. The CFs reinforced Al matrix (CFs/Al) composites with different CFs contents were prepared by stir casting. The effects of the CFs volume fraction and Cu coating on the microstructure, component, TC and CTE of CFs/Al composites were investigated by scanning electron microscopy with EDS, X-ray diffraction, thermal dilatometer and thermal dilatometer. The results show that the Cu coating can effectively improve the interface between CFs and the Al-12Si matrix, and the Cu coating becomes Al2Cu with Al matrix after stir casting. The CFs/Al composites have a relative density greater than 95% when the volume fraction of CFs is less than 8% because the CFs uniform dispersion without agglomeration in the matrix can be achieved by stir casting. The TC and CTE of CFs/Al composites are further improved with the increased CFs volume fraction, respectively. When the volume fraction of CFs is 8%, the CFs/Al composite has the best thermophysical properties; the TC is 169.25 W/mK, and the CTE is 15.28 × 10– 6/K. The excellent thermophysical properties of CFs and good interface bonding are the main reasons for improving the thermophysical properties of composites. The research is expected to improve the application of Al matrix composites in heat dissipation neighborhoods and provide certain theoretical foundations.

In this study, we investigated the change in fracture properties after friction stir welding on Al606. In the L-T direction test, the fracture toughness of the unwelded base material was 275 MPa, and the specimen subjected to friction stir welding (FSW) was 227 MPa, showing that the fracture toughness decreased significantly with friction stir welding. In the T-L direction test, the difference between the base material and the weld material was not large, but the fracture toughness was shown to decrease during welding. In the comparison of the L-T direction and the T-L direction, it was found that both the base material and the weld material showed high fracture toughness in the L-T direction.In this study, the following conclusions were obtained after friction stir welding of Al 6061-T6.

Power converter devices require a high level of quality because they have a high direct connection with vehicle operation. Therefore, structural bonding was carried out by friction stir welding with excellent mechanical properties. Friction stir welding can cause structural deflection depending on the load of the welding tool, so it is important to control this for high quality flatness. In this study, pre-welding was performed before welding to minimize deflection generated during welding. And deflection reduction data according to the location of pre-welding were analyzed through dynamic analysis. As a result, based on computerized data rather than experimental data an optimized position of pre-welding was secured to minimize the deflection that occurs during friction stir welding. Through this, a process guide that enables high quality structural bonding was presented.

B4C/Al composite is mainly used for neutron absorbing materials, which is one of the components of equipment that manages spent nuclear fuel. There are various processes for manufacturing neutron absorbing materials, but most of them are based on the powder metallurgy. In this study, B4C/Al composite in which the reinforcement was uniformly dispersed was manufactured by using the stir casting process. The microstructure, thermal neutron absorption rate, mechanical properties and dispersibility of the reinforcement of the prepared B4C/Al composite were analyzed.

In this study, for thermal neutron absorption, an aluminum metal composite in which B4C particles were uniformly dispersed was prepared using stirring casting and hot rolling processes. The microstructure, thermal neutron absorption rate, mechanical properties and dispersibility of the reinforcement of the prepared B4C/Al composite were analyzed. The composite in which the 40 μm sized B4C particles were uniformly dispersed increased the tensile strength as the volume ratio of the reinforcement increased.

In this paper, the performance evaluation of Al-graphene nanoplatelets (GNP) composites surface engineered by a modified friction stir processing (FSP) is reported. Here, multiple micro channels (MCRF) are used to incorporate GNPs in the aluminium matrix instead of a single large groove (SCRF) that is usually used in conventional FSP. With the MCRF approach, ~ 18% higher peak temperature (compared to SCRF) was observed owing to the presence of aluminium sandwiched between consecutive microgrooves and higher heat accumulation in the stir zone. The MCRF approach have significantly reduced the coefficient of friction and wear rates of the processed composites by ~ 14% and ~ 57%, respectively as compared to the SCRF approach. The proposed reinforcement filling method significantly improves the particle dispersion in the matrix, which in turn changes the adhesion mode of wear in SCRF to abrasive mode in MCRF fabricated composites. The uniformly squeezed out GNP tribolayer prevented the direct metal to metal contact between composite and its counterpart which have effectively reduced the deterioration rates.

Aluminium metal matrix composites (AMMCs) are the fastest developing materials for structural applications due to their high specific weight, modulus, resistance to corrosion and wear, and high temperature strength. Carbon nanotubes (CNTs) is known as the material of the twenty-first century for its various applications in structural components for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present study comprise a systematic literature review of Al/CNT nanocomposites fabricated through a solid state friction stir processing. The present review is primarily focussed on the dispersion and survivability of CNTs in the Al matrix because these are the key factors in deciding the mechanical properties of the fabricated composite. Additionally, the formability, weldability and machinability of the FSPed fabricated composites reinforced with CNTs are also summarised here. Based on the detailed literature review, following research gaps are identified which require a critical and more focussed attention of the scientific community working in this research area: (i) the presence of agglomeration or clustering of CNTs in the composite, (ii) survivability and shortening of CNTs during FSP, (iii) interfacial reactions or the formation of reaction products (such as Al4C3) between Al matrix and CNTs, and (iv) the unidirectional alignment of CNTs in the fabricated composite. Important suggestions for further research in effective dispersion of CNTs with its preserved structure by FSP are also provided.

In this study, experiments and simulations were performed for fillet joint friction stir welding according to tool shape and welding conditions. Conventional butt friction stir welding has good weldability because heat is generated by friction with the bottom of the tool shoulder. However, in the case of fillet friction stir welding, the frictional heat is not sufficiently generated at the bottom of the tool shoulder due to the shape of the tool and the shape of the joint. Therefore, it is important to sufficiently generate frictional heat by slowing the welding speed as compared to butt welding. In this study, experiments and simulations were carried out on an aluminum battery housing made by friction stir welding an extruded material with a fillet joint. The temperature of the structure was measured using a thermocouple during welding, and the heat source was calculated through correlation analysis. Thermal elasto-plastic analysis of the structure was carried out using the calculated heat source and geometric boundary conditions. It is confirmed that the experimental results and the simulation results are well matched. Based on the results of the study, the deformation of the structure can be calculated through simulation even if the tool shape and welding process conditions change.

The life span of many engineering components depends upon their surface properties. The improved surface properties of the materials are essential for enhancing the mechanical and tribological performance of the material. In many applications, the components required only improved surface properties without changing the entire volume properties of the material. The friction stir process (FSP) is a novel processing technique for the fabrication of such surface composites. In the present investigation, the surface composites were fabricated by incorporating molybdenum disulfide ( MoS2) and graphite (Gr) as reinforcement on the surface of aluminum alloy (Al 1120) through the friction stir process (FSP) at tool rotational speed of 1400 rpm and tool feed rate of 40 mm/min process parameters using square profile FSP tool. The tribological behaviors of fabricated surface composites were calculated by using a pin on disk tribometer. It was observed that the wear resistance of surface composites improved as compared to the matrix material.

본 연구는 국내 식생활의 기본적인 구성식단으로 알려진 구이, 찜, 볶음, 조림에 존재하는 다양한 영양성분 중 수용성 비타민인 B1 (thiamin), B2 (riboflavin), 그리고 B3 (niacin)의 함량을 확인하였다. 실험분석 타당성 검증을 통해서 높은 직선성(r2>0.997)을 확인하였고, 검출한계의 경우 0.001-0.067 μg/mL 그리고 정량한계의 경우 0.002- 0.203 μg/mL를 확인하였다. 또한 실험값에 대한 정밀도와 반복성에 대한 검증을 위해서 standard reference materials 를 통해 실험값과 표준값과의 오차가 신뢰도 이내에 존재 한다는 결과를 확인하였다. 본 연구에서 제시된 구이식품의 경우 thiamin은 0.039-1.057 mg/100 g의 범위에 존재하였고, riboflavin은 0.058-0.686 mg/100 g의 범위에 존재했으며, niacin의 경우 0.021-21.772 mg/100 g의 범위로 나 타났다. 찜 종류의 경우 thiamin은 0.049-1.066 mg/100 g의 범위에 존재하였고, riboflavin은 0.025-0.548 mg/100 g의 범위에 존재했으며, niacin의 경우 0.134-21.509 mg/100 g의 범위로 나타났다. 볶음의 경우 thiamin은 0.114-0.388 mg/ 100 g의 범위에 존재하였고, riboflavin은 0.014-1.258 mg/ 100 g의 범위에 존재했으며, niacin의 경우 0.015-2.319 mg/ 100 g의 범위로 나타났다. 조림의 경우 thiamin은 0.112- 1.656 mg/100 g의 범위에 존재하였고, riboflavin은 0.024- 0.298 mg/100 g의 범위에 존재했으며, niacin의 경우 0.322- 2.157 mg/100 g의 범위로 나타났다. 본 연구에서 제시된 구이, 찜, 볶음, 그리고 조림 식품에 대한 수용성 비타민 함량에 대한 영양성분 데이터베이스 구축 연구가 국민 식생활의 중요한 기초자료로 이용될 것으로 확신한다.

In this study, Equivalent fracture strain and Fracture energy were evaluated with the small punch test(SP test) for friction stir welded(FSW) Al6061-T6 sheets. With the three rotation speeds and the three feeding rate, The nine different conditions of FSW were prepared for the SP test. The SP test specimens were manufactured and tested on the advancing side, center, and retreating side to the tool rotation direction. From the SP test data, the equivalent fracture strain and the fracture energy were analyzed. The high value of equivalent fracture strain was attained form tool rotational speed 900RPM and feeding rate 330mm/min. It is found that its characteristic is about 14% higher than the value of condition 1100RPM-330mm/min that have the lowest value. The high value of fracture energy was obtained from the tool rotation speed 900RPM and feeding rate 330mm/min. The lowest fracture energy, which from 1000RPM-300mm/min, was approximately 16% difference to the highest value.

목 적 : 목 부위에 있는 brachial plexus 검사 시 쇄골, 늑골, 쇄골 하 동맥과 정맥 및 다양한 근육으로 인한 복잡한 구조 때 문에 지방이 제대로 소거가 되지 않아 이를 제거하기 위해 STIR sequence를 SPIR(chemical saturation)기법과 함께 사용하고 있다. 하지만 이러한 경우에도 혈액의 강한 신호로 인해 신경다발 관찰에 어려움을 겪고 있다. 본 연구에서는 이러한 지방소거 기법과 함께 Black Blood pulse를 이용한 3D TSE STIR + Black Blood(이하3D TSE STIR+BB(iMSDE))기법의 유성을 알아보는데 있다. 대상 및 방법 : 2017년 1월 10일부터 2월 20일까지 지원자 15명을 대상(남자 8명, 여자 7명, 평균연령 35세)으로 3D TSE STIR기법과 3D TSE STIR+BB(iMSDE)기법으로 스캔하여 영상에 ROI를 설정하여대해 정량적 분석과 정성적 분석을 실시하였다. 사용 된 장비는 3.0T MR Imaging system (Ingenia 3.0T CX; Philips Healthcare, Best, Netherland)로 maximum achievable gradient amplitude는 80mT/m, slew rate 200T/m/sec 이고 dS head, anterior, posterior coil을 사용하였다. 검사 방법으로는 바로 누운 자세로 검사를 시행하였고 영상변수는 3D TSE STIR기법의 경우 TR=2200ms, TE=212ms, TI=220ms, FOV=300mm, Matrix=256×256, Slice Thickness=1mm, #slice=170, NEX=1, 총 영상획득 시간은 5분54초 였다. 3D TSE STIR+BB(iMSDE) 기법은 TR=2200ms, TE=170ms, TI=250ms, FOV=300mm, Matrix=256×256, Slice Thickness=1mm, #slice=170, NEX=1, 총 영상획득 시간은 4분 13초였다. 결 과 : 정성적 정량적 평가 모두 3D TSE STIR+BB(iMSDE)가 3D TSE STIR보다 더 좋은 결과가 나왔으며 통계학적으로 모두 0.05미만을 나타내고 있어 통계적 유의성을 보여주고 있다. 결 론 : 3D TSE STIR기법만 사용했을 때 보다는 3D TSE STIR 기법에 BB(iMSDE)기법을 결합하여 사용한 경우 검사 시 간이 더 빠르며 SNR, CNR과 같은 정량적, 정성적 평가 등 모든 부분에서 좋은 결과를 얻을 수 있는 장점이 있다. 따라서 brachial plexus 검사시 BB (iMSDE) pulse를 함께 사용하는 것이 진단적 가치가 더 있을 것으로 사료된다.

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).