Готові списки джерел за темами / Defect-free joints

Добірка наукової літератури з теми "Defect-free joints"

Автор: Grafiati

Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Defect-free joints"

Leinenbach, Christian, Michael Koster, and Hans-Jakob Schindler. "Fatigue Assessment of Defect-Free and Defect-Containing Brazed Steel Joints." Journal of Materials Engineering and Performance 21, no. 5 (February 28, 2012): 739–47. http://dx.doi.org/10.1007/s11665-012-0182-7.

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Li, Weipo, Zhimin Liang, Congwei Cai, and Dianlong Wang. "Repair Welding of the Tunnel Defect in Friction Stir Weld." High Temperature Materials and Processes 37, no. 7 (July 26, 2018): 675–81. http://dx.doi.org/10.1515/htmp-2017-0026.

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AbstractThe tunnel defect formed in friction stir weld would dramatically push the mechanical properties of joints into deterioration. In this study, friction stir welding process was adopted to repair the joints of 7N01 aluminum alloy with tunnel defect. The effects of friction stir repair welding process on the microstructure and mechanical properties were comprehensively investigated. Microstructure of the repaired joints shows that the grain size in nugget zone decreases slightly while the recrystallization in the retreating side of thermo-mechanically affected zone is intensified as the joints are repaired. The microhardness of the repaired joints declined slightly compared with the defective joint. However, the yield strength and tensile strength increase and recover to the values of the joints free of defect. The longitudinal residual stress in weld zone increased remarkably as the repair times increase. Compared with the once repaired joint, yield strength and tensile strength of the twice repaired joint reduced slightly, and the throat thickness also reduced during the repeated repair welding process. Therefore, the times of repair welding applied should be limited actually.

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Barat, Vera, Artem Marchenkov, Vladimir Bardakov, Daria Zhgut, Marina Karpova, Timofey Balandin, and Sergey Elizarov. "Assessment of the Structural State of Dissimilar Welded Joints by the Acoustic Emission Method." Applied Sciences 12, no. 14 (July 18, 2022): 7213. http://dx.doi.org/10.3390/app12147213.

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In this study, we investigated defect detection in dissimilar welded joints by the acoustic emission (AE) method. The study objects were carbide and decarburized interlayers, which are formed at the fusion boundary between austenitic and pearlitic steels. Diffusion interlayers, as a structural defect, usually have microscopic dimensions and cannot be detected using conventional non-destructive testing (NDT) methods. In this regard, the AE method is a promising approach to diagnose metal objects with a complex structure and to detect microscopic defects. In this paper, the AE signatures obtained from testing defect-free specimens and specimens with diffusion interlayers are analyzed. We found that the AE signature for defective and defect-free welded joints has significant differences, which makes it possible to identify descriptors corresponding to the presence of diffusion interlayers in dissimilar welded joints.

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Motomura, Hisashi, Kensuke Nose, Masao Fujiwara, Toshiyuki Ozawa, Teruichi Harada, and Michinari Muraoka. "Arthroplasty of the Interphalangeal Joint of the Great Toe Using Costal Osteochondral Grafting." Journal of the American Podiatric Medical Association 96, no. 6 (November 1, 2006): 508–12. http://dx.doi.org/10.7547/0960508.

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Although many reports have been published on the usefulness of costal cartilage grafting in the reconstruction of interphalangeal joints of fingers, there are only a few published reports on the reconstruction of interphalangeal joints of toes. We describe a 21-year-old woman with a tissue defect of the dorsum pedis and a partial defect of the interphalangeal joint of the great toe caused by a motor-vehicle accident. We attempted arthroplasty using a free latissimus dorsi myocutaneous flap and a costal osteochondral graft. The grafted rib and cartilage survived, allowing the patient to resume functional ambulation for day-to-day activities. Arthroplasty using costal osteochondral grafts seems to be an effective means of reconstructing the interphalangeal joints of toes. (J Am Podiatr Med Assoc 96(6): 508–512, 2006)

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Al-jarrah, J. A., A. Ibrahim, and S. Sawlaha. "Effect of Applied Pressure on the Mechanical Properties of 6061 Aluminum Alloy Welded Joints Prepared by Friction Stir Welding." Engineering, Technology & Applied Science Research 7, no. 3 (June 12, 2017): 1619–22. http://dx.doi.org/10.48084/etasr.1124.

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This paper investigates the effect of axial force on the surface appearance and mechanical properties of 6061 aluminum alloy welded joints prepared by friction stir welding. The applied pressure varies from 1.44 to 10.07 MPa. The applied pressure was calculated from the axial force which exerted by a spring loaded cell designed for this purpose. Defect free joints obtained at an applied pressure of 3.62 MPa. The mechanical properties of the welded joints were evaluated through microhardness and tensile tests at room temperature. From this investigation, it was found that the joint produced with an applied pressure of 5.76 MPa exhibits superior tensile strength compared to other welded joints. The fracture of this joint happened at the base material.

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Yan, Yinfei, Yifu Shen, Keyu Shi, Jiaxin Wu, and Jinpeng Hu. "Friction plug repair welding of glass fiber-reinforced polyamide 6: Investigation of morphology, microstructure, and mechanical properties." Journal of Reinforced Plastics and Composites 39, no. 21-22 (June 15, 2020): 805–16. http://dx.doi.org/10.1177/0731684420932646.

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Friction plug repair welding technology has been demonstrated to be effective to repair the glass fiber-reinforced polyamide 6 sheets in the present paper. Influences of repair hole geometries and parameters on joint morphology and mechanical performance were investigated. Results showed that defect-free repaired joints were produced with the utilization of tapered holes rather than cylindrical holes. Process parameters exerted significant influences on the cross-sectional profile and morphology of the joints. Defect-free repaired welds with larger stir zone thicknesses were produced with the proper increase of rotational speeds, but excessive rotational speeds caused the formation of cavities along the plug boundary and the reduction of stir zone thicknesses. The fluctuation of the wavy bottom interface increased under larger plunge rates and incomplete connections between stir zone and base material were observed under plunge rate of 25 mm/min. Extended dwell time led to larger stir zone thickness and improved joint morphology. Tensile tests showed that the strength of the repaired joints increased and then decreased with the enlargement of rotational speeds. Decreased plunge rate and extended dwell time led to promoted joint mechanical performance. Three failure modes were observed, which corresponded to low, middle, and high repaired weld strengths.

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Wei, Yanni, Hui Li, Peng Xiao, and Juntao Zou. "Microstructure and Conductivity of the Al-Cu Joint Processed by Friction Stir Welding." Advances in Materials Science and Engineering 2020 (July 27, 2020): 1–10. http://dx.doi.org/10.1155/2020/6845468.

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In this paper, 1060 aluminum and T2 pure copper were joined by friction stir welding. The influence of the rotation speed and inclination on the microstructure and mechanical properties of the joint were investigated. The microstructure and composition of the welded interface region were analyzed. The joints’ strength was tested, and the conductivity of the joints was estimated. Joints having good surface formation and defect-free cross section were successfully obtained. The cross-sectional morphologies of the Al-Cu friction stir welding joints can be divided into three zones: the shoulder impact zone, the weld nugget zone, and the interface zone. The interface zone consisted of a metallurgical reaction layer and a visible mixed structure. The reaction layers were identified as Al2Cu, Al4Cu9 phases. The tensile strength of the joints reaches maximum values of 102 MPa at a rotation speed of 950 rpm and inclination of 0°, which was approximately equal to those of 1060Al base metal. The resistivity of the Al-Cu joint was approximately equal to the theoretical resistivity. The interfacial resistance is directly affected by the joint defects, compound types, and thickness of the intermetallic compound layer.

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Ivanov, Alexey, Valery Rubtsov, Andrey Chumaevskii, Kseniya Osipovich, Evgeny Kolubaev, Vladimir Bakshaev, and Ivan Ivashkin. "Features of structure formation processes in AA2024 alloy joints formed by the friction stir welding with bobbin tool." Metal Working and Material Science 23, no. 2 (June 10, 2021): 98–115. http://dx.doi.org/10.17212/1994-6309-2021-23.2-98-115.

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Introduction. One of friction stir welding types is the bobbin friction stir welding (BFSW) process, which allows to obtain welded joints in various configurations without using a substrate and axial embedding force, as well as to reduce heat loss and temperature gradient across the welded material thickness. This makes the BFSW process effective for welding aluminum alloys, which properties are determined by their structural-phase state. According to research data, the temperature and strain rate of the welded material have some value intervals in which strong defect-free joints are formed. At the same time, much less attention has been paid to the mechanisms of structure formation in the BFSW process. Therefore, to solve the problem of obtaining defect-free and strong welded joints by BFSW, an extended understanding of the basic mechanisms of structure formation in the welding process is required. The aim of this work is to research the mechanisms of structure formation in welded joint of AA2024 alloy obtained by bobbin tool friction stir welding with variation of the welding speed. Results and discussion. Weld formation conditions during BFSW process are determined by heat input into a welded material, its fragmentation and plastic flow around the welding tool, which depend on the ratio of tool rotation speed and tool travel speed. Mechanisms of joint formation are based on a combination of equally important processes of adhesive interaction in “tool-material” system and extrusion of metal into the region behind the welding tool. Combined with heat dissipation conditions and the configuration of the “tool-material” system, this leads to material extrusion from a welded joint and its decompaction. This results in formation of extended defects. Increasing in tool travel speed reduce the specific heat input, but in case of extended joints welding an amount of heat released in joint increases because of specific heat removal conditions. As a result, the conditions of adhesion interaction and extrusion processes change, which leads either to the growth of existing defects or to the formation of new ones. Taking into account the complexity of mechanisms of structure formation in joint obtained by BFSW, an obtaining of defect-free joints implies a necessary usage of various nondestructive testing methods in combination with an adaptive control of technological parameters directly in course of a welding process.

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Sevvel, P., and V. Jaiganesh. "Influence of The Arrangement of Materials and Microstructural Analysis During FSW of AZ80A & AZ91C Mg Alloys." Archives of Metallurgy and Materials 62, no. 3 (September 26, 2017): 1795–801. http://dx.doi.org/10.1515/amm-2017-0272.

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AbstractThe main objective of this paper is to produce defect free weldments with improved properties during friction stir welding of dissimilar Mg alloys. The influence of the anisotropic arrangement of materials when AZ80A Mg alloy is taken as advancing side and AZ91C Mg alloy as retreating side and vice versa with respect to their mechanical properties and microstructural characteristics were investigated. The effects of various FSW parameters on the quality of these joints were also analyzed and best optimized FSW parameters were suggested. Defect free sound joints with excellent mechanical properties were produced when AZ80A Mg alloy was positioned at retreating side. At the same time, it seems a little bit difficult to obtain good quality joints with the contrary arrangement of materials. These investigations revealed that materials having inferior plastic deformability must be kept at the advancing side to obtain sound joints during FSW of dissimilar alloys of Magnesium.

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Li, Tielong, and Zhenshan Wang. "Forming and Properties of Friction Stir Welding Process for Dissimilar Mg Alloy." Open Mechanical Engineering Journal 9, no. 1 (October 7, 2015): 859–64. http://dx.doi.org/10.2174/1874155x01509010859.

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For hot extrusions of magnesium alloy sheets, Dissimilar AZ80 and AZ31 were used, in which AZ80 was placed on advancing side and AZ31 on retreating side, using friction stir butt welding with different process parameters. Some defect-free welded joints with good weld surfaces could be obtained with some suitable welding conditions. The maximum tensile strength of welded joint which is 225.5 MPa can reach 98% that of the AZ31 base material. Influence of process parameters on defects, weld shaping and mechanical property were discussed systematically. And the microstructure of different zones was compared. The fracture of the welded joints takes place at the junction of mechanical heat affected zone and nugget zone in AZ31 magnesium alloy set retreating side, since existing difference in metallographic structure of alloy diversely suffered by heat, pressure and depositing impurities. Fracture initiation site may be the P line defect which should be eliminated, and the P line defect formation was analyzed.

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Тези доповідей конференцій з теми "Defect-free joints"

Ma, YunWu, YongBing Li, and ZhongQin Lin. "Joint Formation and Mechanical Performance of Friction Self-Piercing Riveted Aluminum Alloy AA7075-T6 Joints." In ASME 2019 14th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/msec2019-2857.

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Abstract AA7xxx series aluminum alloys have great potentials in mass saving of vehicle bodies due to pretty high specific strength. However, the use of these high strength materials poses significant challenges to traditional self-piercing riveting (SPR) process. To address this issue, friction self-piercing riveting (F-SPR) was applied to join aluminum alloy AA7075-T6 sheets. F-SPR is realized by feeding a high speed rotating steel rivet to aluminum alloy sheets to form a dissimilar material joint. The effects of spindle speed and rivet feed rate on F-SPR joint cross-section geometry evolution, riveting force and energy input were investigated systematically. It was found that the rivet shank deformation, especially the buckling of the shank tip before penetrating through the top sheet has significant influence on geometry and lap-shear failure mode of the final joint. A medium rivet feed rate combined with a high spindle speed was prone to produce a defect free joint with sound mechanical interlocking. F-SPR joints with the failure mode of rivet shear fracture was observed to have superior lap-shear peak load and energy absorption over the joints with mechanical interlock failure. The optimized F-SPR joint in this study exhibited 67.6% and 13.9% greater lap-shear peak load compared to, respectively, SPR and refill friction stir spot welding joints of the same sheets. This research provides a valuable reference for further understanding the F-SPR process.

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Kulkarni, Neha, and M. Ramulu. "Experimental and Numerical Analysis of Mechanical Behavior in Friction Stir Welded Different Titanium Alloys." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39211.

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Friction Stir Welding (FSW) has been widely accepted technique to join titanium alloy, Ti-6Al-4V, to produce defect free sheets of it. The friction stir welding with other titanium alloys has a potential to improve the utilization and functional properties of titanium. The current study was undertaken to evaluate the performance of friction stir welded (FSW) different titanium joints. The impact of process parameters, mainly the spindle speed and feed rate on the strength of friction stir welded titanium alloy joints was studied. A combined approach of numerical and experimental was used to investigate the mechanical response of different titanium joints. This paper presents the numerical model that was developed to simulate mechanical behavior of FSW titanium joints. The numerical results were compared to experimentally determined behavior characteristics of the joints to gage the validity of the modeling approach. It was found that there was good agreement in the numerical and experimental results of the tensile behavior in titanium FSW joints. The optimum values of spindle speed and feed rate were found out for joining different titanium alloys.

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Perkins, David A., and Andrew P. Murray. "Singularity-Free RPR and SPS Chains for Actuating Single Degree of Freedom Planar and Spherical Mechanisms." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28896.

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This paper presents a method of selecting joints relative to a fixed and moving (coupler) frame that can be used to actuate a single degree of freedom planar mechanism using a revolute-prismatic-revolute (RPR) chain or a spherical mechanism via a spherical-prismatic-spherical (SPS) chain. Given a single degree of freedom mechanism, a moving reference frame attached to any link has a motion that can be described with a single parameter. A point relative to this moving frame is sought such that it either continually increases or decreases in distance from a point in the fixed frame over the entire motion. The mechanism can then be moved by placing an actuated prismatic joint between the two points. Moreover, the singularities relative to the joints in the original mechanism are not a concern and the dimensional synthesis can focus on creating the set of circuit-defect free solutions. From this analysis, a unique fixed point is determined relative to two positions and their velocities with the following characteristic. All points in the moving reference frame that are moving away from it in the first position are approaching it in the second position, and vice versa.

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Baydoun, Ahmad M. R., and Ramsey F. Hamade. "A Study of the Effect of Extended Hounsfield Unit Range and Voxel Size on Defect Detection in Friction Stir Welds." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23274.

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Abstract Friction stir welding (FSW) is a novel welding method that is garnering attention, in part, due to its ability to join dissimilar materials. One of the challenges in producing dissimilar friction welded joints is ensuring the welds are defect-free. Nondestructive testing (NDT) methods such as ultrasonic waves, gamma rays, X-rays, and X-ray CT, are gaining popularity as a method to detect internal defects in FSW joints. In this study, dissimilar AA1050-AA6061-T6 FSW lap welds are Manufactured and then examined using an NDT X-ray CT technique. The effects of two critical X-ray CT scanning parameters (voxel size and Hounsfield unit (HU)) on the detection of internal defects are investigated. The samples are scanned via X-ray CT at two different voxel sizes (2.457 E−02 and 1.420 E−03 mm3) and two HU ranges (12-bit and 16-bit depth). The generated Digital Imaging and Communications in Medicine (DICOM) images are segmented based on a proper HU threshold found via the Otsu thresholding method. The findings show that Small voxel size (higher resolution) improves the ability of detecting internal defects and improves the effectiveness of the thresholding process. Higher HU range results in a wider separation between detected material peaks, thus enhancing the effectiveness of the thresholding process as well.

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Dewan, Mohammad W., Muhammad A. Wahab, and Khurshida Sharmin. "Effects of Post Weld Heat Treatments (PWHT) on Friction Stir Welded AA2219-T87 Joints." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-3021.

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Friction Stir Welding (FSW) offers significantly better performance on aluminum alloy joints compared to the conventional fusion arc welding techniques; however, plastic deformation, visco-plastic flow of metals, and complex non-uniform heating cycles during FSW processes, result in dissolution of alloying elements, intrinsic microstructural changes, and post-weld residual stress development. As a consequence, about 30% reduction in ultimate strength (UTS) and 60% reduction in yield strength (YS) were observed in defect-free, as-welded AA2219-T87 joints. PWHT is a common practice to refine grain-coarsened microstructures which removes or redistributes post-weld residual stresses; and improves mechanical properties of heat-treatable welded aluminum alloys by precipitation hardening. An extensive experimental program was undertaken on PWHT of FS-welded AA2219-T87 to obtain optimum PWHT conditions and improvement of the tensile properties. Artificial age-hardening (AH) helped in the precipitation of supersaturated alloying elements produced around weld nugget area during the welding process. As a result, an average 20% improvement in YS and 5% improvements in UTS was observed in age-hardened (AH-170°C-18h) specimens as compared to AW specimens. To achieve full benefit of PWHT, solution-treatment followed by age-hardening (STAH) was performed on FS-welded AA2219-T87 specimens. Solution-treatment (ST) helps in the grain refinement and formation of supersaturated precipitates in aluminum alloys. Age-hardening of ST specimens help in the precipitation of alloying elements around grain boundaries and strengthen the specimens. Optimum aging period is important to achieve better mechanical properties. For FS-welded AA2219-T87 peak aging time was 5 hours at 170°C. STAH-170°C -5h treated specimens showed about 78% JE based on UTS, 61% JE based on yield strength, and 36% JE based on tensile toughness values of base metal.

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S, Aravindan, and Siddharth Tamang. "JOINING OF CU TO SS304 BY MICROWAVE HYBRID HEATING WITH NI AN INTERLAYER." In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9813.

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The joining of dissimilar Pure Copper (Cu) to Stainless Steel (SS304) is necesilated in many industrial applications such as heat exchangers and electrical contacts. Advantages of both the materials such as high electrical conductivity of copper and better corrosion resistance of SS304 can be harnessed by way of joining both the metals. However, joining to Cu to itself or other materials is a challenge since the input heat is dissipated rapidly. Most of the conventional welding methods such as arc and gas are incompetent and unconventional methods such as Explosion Welding, EBW, Diffusion Bonding are very expensive.In this study a new economical process of joining of dissimilar metals i.e. Cu to SS304 by microwave hybrid heating is investigated. Microwave joining is made possible by applying a powder (in this work Nickel metal powder) as an interlayer and exposing to microwave surrounding the interlayer with a susceptor. In this study the interlayer of Ni powder having average size 200nm and 45μm was used. On exposure to microwave, the interlayer meal powder heats up [1] and then it promotes melting and thereby bonding to facilitate dissimilar joint. The microstructure of the joint is studied by optical microscope and scanning electron microscope. The joints formed with 200nm Ni powder were observed to have a defect free microstructure as illustrated in Fig. 1. The EDS and XRD analysis determines the formation of solid solution between Cu-Ni interface and an intermetallic compound at Fe-Ni interface. The diffusion of elements across the joint was further analyzed by EDS line scan. The hardness variation was studied by Vickers’ micro-hardness. It can be concluded that smaller size Ni heat up faster in microwave and produce stronger joint of Cu to SS304 by microwave hybrid heating. References 1. M. S. Srinath, A. K. Sharma, et al. ,Materials & Design , 2011, 32, 2685–2694

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Chitturi, Veerendra, Srinivasa Rao Pedapati, and Mokhtar Awang. "Effect of Process Parameters on Friction Stir Lap Welded 304 Stainless Steel and 5052 Aluminium Alloys." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23807.

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Abstract Joining of two different materials like aluminium and steel is a challenging task because of the vast differences in their physical, mechanical and chemical properties. Friction stir welding is a solid-state joining technique which is successful in joining dissimilar materials. In this study, the tool made with Tungsten-Rhenium with a pin length of 4.1 mm is used to weld 4 mm stainless steel and 2 mm aluminium plates in lap configuration with steel as the top plate. The process parameters used in the study are tool rotational speeds between 800 rpm and 1200 rpm, traverse speed ranging from 20 mm/min to 40 mm/min, penetration depth of 4.1 mm to 4.3 mm with a varying tilt between from 0° and 2.5°. The Aluminium is melted during the process because of the high temperature and is thrown out in the form of flash resulting in the formation of defects and a cup like structure at the weld zone. Microstructural analysis confirmed that formation of a sound joint without defects was impossible. The mechanically stirred zone consists of a thin intermetallic layer at the interface of aluminium and steel plates. The thickness of the intermetallic layers formed were between 5 μm and 20 μm. The maximum shear strength of 2.7 kN was achieved with tool rotational speed of 1000 rpm, penetration depth of 4.3 mm and welding speed of 30 mm/min when the angle was tilted at 0°. It is evident from the experiments that the joints achieved were not defect free because of improper mixing of the material.

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Tarawneh, Constantine M., Javier A. Kypuros, Brent M. Wilson, Todd W. Snyder, Bertha A. Gonzalez, and Arturo A. Fuentes. "A Collaborative On-Track Field Test Conducted to Verify the Laboratory Findings on Bearing Temperature Trending." In 2009 Joint Rail Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/jrc2009-63056.

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Over the last three years, numerous laboratory tests have been conducted with the goal of identifying the root cause of the temperature trending phenomenon observed in tapered roller bearings during their field service. The experimental efforts were successful in duplicating the temperature trending phenomenon in the lab, and concluded that vibration induced roller misalignment was responsible for this troubling phenomenon; yet field verification of these findings was still missing. To this end, a collaborative on-track field test was carefully planned and executed by The Amsted Rail Company, The Union Pacific Railroad (UP), Rail Sciences Inc. (RSI), and The University of Texas-Pan American (UTPA). A locomotive, a business car, and two coal cars — one fully loaded and one empty — were made available by the UP for the purposes of this test. Four bearings that exhibited temperature trending during the laboratory testing, and two other bearings that were set-out for temperature trending by the UP, were mounted next to six high impact wheels of at least 70 kips. The impact wheels were used as external vibration sources. Three of these wheels were placed under the fully loaded coal car, and the other three under the empty car. The remaining components used in the test were all defect free bearings and wheels. All sixteen bearings were instrumented with thermocouples and accelerometers, with four additional accelerometers monitoring the track joints and defects and the car pitch and bounce. This paper provides a summary of the initial analysis of the acquired data which indicates that the field test was successful in verifying the laboratory findings.

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Stellman, P., W. Arora, S. Takahashi, E. D. Demaine, and G. Barbastathis. "Kinematics and Dynamics of Nanostructured Origami™." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81824.

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Two-dimensional (2D) nanofabrication processes such as lithography are the primary tools for building functional nanostructures. The third spatial dimension enables completely new devices to be realized, such as photonic crystals with arbitrary defect structures and materials with negative index of refraction [1]. Presently, available methods for three-dimensional (3D) nanopatterning tend to be either cost inefficient or limited to periodic structures. The Nanostructured Origami method fabricates 3D devices by first patterning nanostructures (electronic, optical, mechanical, etc) onto a 2D substrate and subsequently folding segments along predefined creases until the final design is obtained [2]. This approach allows almost arbitrary 3D nanostructured systems to be fabricated using exclusively 2D nanopatterning tools. In this paper, we present two approaches to the kinematic and dynamic modeling of folding origami structures. The first approach deals with the kinematics of unfolding single-vertex origami. This work is based on research conducted in the origami mathematics community, which is making rapid progress in understanding the geometry of origami and folding in general [3]. First, a unit positive “charge” is assigned to the creases of the structure in its folded state. Thus, each configuration of the structure as it unfolds can be assigned a value of electrostatic (Coulomb) energy. Because of repulsion between the positive charges, the structure will unfold if allowed to decrease its energy. If the energy minimization can be carried out all the way to the completely unfolded state, we are simultaneously guaranteed of the absence of collisions for the determined path. The second method deals with dynamic modeling of folding multi-segment (accordion style) origamis. The actuation method for folding the segments uses a thin, stressed metal layer that is deposited as a hinge on a relatively stress free structural layer. Through the use of robotics routines, the hinges are modeled as revolute joints, and the system dynamics are calculated.

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Balois, Maria Vanessa C., Norihiko Hayazawa, Satoshi Yasuda, Katsuyoshi Ikeda, Bo Yang, Emiko Kazuma, Yasayuki Yokota, Yousoo Kim, and Takuo Tanaka. "Plasmon activated forbidden phonon modes in defect-free graphene by tip-enhanced nano-confined light." In JSAP-OSA Joint Symposia. Washington, D.C.: Optica Publishing Group, 2018. http://dx.doi.org/10.1364/jsap.2018.18a_211b_5.

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