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Sample records for spot friction welding

  1. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Hovanski, Yuri; Grant, Glenn J.; Santella, M. L.

    2009-11-13

    Friction stir spot welding techniques were developed to successfully join several advanced high strength steels. Two distinct tool materials were evaluated to determine the effect of tool materials on the process parameters and joint properties. Welds were characterized primarily via lap shear, microhardness, and optical microscopy. Friction stir spot welds were compared to the resistance spot welds in similar strength alloys by using the AWS standard for resistance spot welding high strength steels. As further comparison, a primitive cost comparison between the two joining processes was developed, which included an evaluation of the future cost prospects of friction stir spot welding in advanced high strength steels.

  2. Fundamentals of friction stir spot welding

    NASA Astrophysics Data System (ADS)

    Badarinarayan, Harsha

    The recent spike in energy costs has been a major contributor to propel the use of light weight alloys in the transportation industry. In particular, the automotive industry sees benefit in using light weight alloys to increase fuel efficiency and enhance performance. In this context, light weight design by replacing steel with Al and/or Mg alloys have been considered as promising initiatives. The joining of structures made of light weight alloys is therefore very important and calls for more attention. Friction Stir Spot Welding (FSSW) is an evolving technique that offers several advantages over conventional joining processes. The fundamentals aspects of FSSW are systematically studied in this dissertation. The effects and influence of process inputs (weld parameters and tool geometry) on the process output (weld geometry and static strength) is studied. A Design of Experiments (DoE) is carried out to identify the effect of each process parameter on weld strength. It is found that the tool geometry, and in particular the pin profile has a significant role in determining the weld geometry (hook, stir zone size etc.) which in turn influences the failure mode and weld strength. A novel triangular pin tool geometry is proposed that suppresses the hook formation and produces welds with twice the static strength as those produced with conventional cylindrical pin tools. An experimental and numerical approach is undertaken to understand the effect of pin geometry on the material flow and failure mechanism of spot welds. In addition, key practical issues have been addressed such as quantification of tool life and a methodology to control tool plunge depth during welding. Finally, by implementing the findings of this dissertation, FSSW is successfully performed on a closure panel assembly for an automotive application.

  3. Friction Stir Spot Welding of DP780 Carbon Steel

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Frederick, Alan; Grant, Glenn J.; Dahl, Michael E.

    2009-09-15

    Friction stir spot welds were made in uncoated and galvannneled DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1-10 s. Increasing tool rotation speed from 800 to 1600 rpm increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap-shear strengths exceeding 10.3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.

  4. FRICTION STIR SPOT WELDING OF 6016 ALUMINUM ALLOY

    SciTech Connect

    Mishra, Rajiv S.; Webb, S.; Freeney, T. A.; Chen, Y. L.; Gayden, X.; Grant, Glenn J.; Herling, Darrell R.

    2007-01-08

    Friction stir spot welding (FSSW) of 6016 aluminum alloy was evaluated with conventional pin tool and new off-center feature tools. The off-center feature tool provides significant control over the joint area. The tool rotation rate was varied between 1000 and 2500 rpm. Maximum failure strength was observed in the tool rotation range of 1200-1500 rpm. The results are interpreted in the context of material flow in the joint and influence of thermal input on microstructural changes. The off-center feature tool concept opens up new possibilities for plunge-type friction stir spot welding.

  5. Friction Stir Spot Welding of DP780 Carbon Steel

    SciTech Connect

    Santella, Michael L; Hovanski, Yuri; Frederick, David Alan; Grant, Glenn J; Dahl, Michael E

    2010-01-01

    Friction stir spot welds were made in uncoated and galvannealed DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1 to 10 s. Increasing tool rotation speed from 800 to 1600 rev min{sup -1} increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap shear strengths exceeding 10 {center_dot} 3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.

  6. Friction stir spot welding of hot-stamped boron steel

    SciTech Connect

    Hovanski, Yuri; Santella, M. L.; Grant, Glenn J.

    2007-11-01

    Hot-stamped, boron steel was successfully joined via friction stir spot welding using polycrystalline cubic boron nitride tooling. The resulting microstructure, microhardness and mechanical properties are reported, including a brief look into failure mechanisms. Relationships between the unique mechanical mixing, phase transformations and failure initiation sites associated with joining martensitic steels are characterized.

  7. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Santella, Michael L; Hovanski, Yuri; Grant, Glenn J; Frederick, D Alan; Dahl, Michael E

    2009-02-01

    Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.

  8. Friction Stir Spot Welding of Advanced High Strength Steels

    SciTech Connect

    Hovanski, Yuri; Santella, M. L.; Grant, Glenn J.

    2009-12-28

    Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.

  9. Friction Stir Spot Welding of 6061 Aluminum-to-Copper

    NASA Astrophysics Data System (ADS)

    Heideman, Robert J.

    Friction stir spot welding (FSSW) between 1.5mm thick 6061 Al on top and 1.5mm thick Cu at bottom was conducted. First, weld parameters and the weld macrostructure that were necessary to form good quality welds, as determined using lap shear weld strength, were identified. Tool rotation speed and tool pin length are key variables that control weld strength. To obtain high quality strong welds, a Cu ring extruded upward from the lower Cu sheet into the upper 6061 Al-sheet, which promoted bonding and interlocking between the sheets, and an Al-rich stir zone between Cu ring and weld keyhole were both necessary. Second, a technique where the tool remained in the sample after FSSW helped determine the material flow that takes place during high quality weld formation and the functions of the welding tool features. The tool threads cause 6061 Al from the upper sheet to move downward into the region near the threads. The tool shoulder causes a counter flow movement of 6061 Al that results in the formation of the Al-rich stir zone and also causes the upward extrusion of the lower Cu sheet. This technique also identified that a Cu-rich material forms on the tool tip, that this material sheds and rebuilds during subsequent welds, and that this material can form large Cu-rich particles that can completely fill the tool threads, impede proper material flow and lead to a low strength, poor quality weld. Third, to further understand welding parameters, weld temperatures, torque, and vertical forces were measured. Temperature data was collected using a tool holder that permitted wireless thermocouple data collection. Through these measurements, rotational plunge weld energy was recognized as important in determining if a quality weld formed, and weld plunge rate was identified as the welding parameter that significantly impacted rotational weld plunge energy. The final phase of research was to improve weld quality consistency. Through repetitive trials with a single tool

  10. Textures in Single-Crystal Aluminum Friction Stir Spot Welds

    NASA Astrophysics Data System (ADS)

    Shibayanagi, Toshiya; Gerlich, Adrian P.; Kashihara, Keizo; North, Thomas H.

    2009-04-01

    The present article examines the textural features produced during friction stir spot welding of single-crystal aluminum sheet. The crystal has the {111} plane perpendicular to the normal direction (ND) of the sheet, and the left< { 1 10} rightrangle direction parallel to the growth direction (GD). Friction stir spot welding was carried out using a rotation speed of 1500 rpm and a dwell time of 2 seconds, and completed spot welds were characterized using a combination of optical microscopy and electron backscatter diffraction (EBSD). The EBSD measurements indicate there are no significant changes in orientation in locations more than 840 μm from the stir-zone extremity. The orientation distribution in the thermomechanically-affected zone (TMAZ) region conformed with the {110}⊥ND orientation within 580 μm of the stir-zone extremity. In the location immediately adjacent to the stir-zone extremity, there was a deviation from the {110}//ND orientation due to a combination of compressive loading perpendicular to the stir-zone boundary and shear loading in the direction of tool rotation. It is suggested a {111}⊥ND texture in the stir zone is associated with material flow imposed by the thread on the rotating pin.

  11. Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding

    SciTech Connect

    Grant, Glenn J.; Herling, Darrell R.; Arbegast, William J.; Allen, Casey D.; Degen, Cassandra M.

    2006-12-20

    Superplastically-formed structural panels are growing in their applications in aerospace, aircraft, automotive, and other industries. Generally, monolithic sheets are employed, limiting the size and complexity of the final part. However, more complex and larger final geometries are possible if individual sheet materials can be joined together through an appropriate joining technology, then SPF formed to final shape. The primary challenge in this type of SPF fabrication has been making a joint between the sheets that will survive the SPF forming event and display the correct amount of elongation in the joint relative to the base materials being formed. Friction Stir Welding is an ideal joining technology for SPF applications because the forming response of the weld metal at SPF conditions is adjustable by selecting different weld process parameters during initial joining. This allows the SPF deformation in the weld metal to be “tuned” to the deformation of the parent sheet to prevent early failure from occurring in either the weld metal or the parent sheet due to mismatched SPF flow stresses. Industrial application of the concept of matching flow stresses is currently being pursued on a program at the Pacific Northwest National Laboratory on room temperature formed friction stir welded tailor welded blanks for heavy truck applications. Flow stress matching and process parameter “tuning” is also important in the fabrication of SPF multisheet structural panels. These panels are fabricated by joining three sheets together with alternating welds top and bottom, so that each weld penetrates only two of the three sheets. This sheet pack is then sealed with a weld seam around the outside and hot gas is introduced between the sheets through a welded tube. Under SPF conditions the sheet pack inflates to produce an internally supported structure. In this paper we presents results on an investigation into using FSW and Refill Friction Stir Spot Welding to fabricated

  12. A Feasiblity Study on Spot Friction Welding of Magnesium Alloy AZ31

    SciTech Connect

    Santella, Michael L; Pan, Dr. Tsung-Yu; Frederick, David Alan; Schwartz, William

    2007-01-01

    Spot friction welding (SFW) is a novel variant of the linear friction stir welding process with the potential to create strong joints between similar, as well as dissimilar sheet metals. It is particularly suitable for soft, low melting point metals such as aluminum, magnesium, and their alloys where resistance spot welding can cause defects such as voids, trapped gas and micro-cracks due to the intense heat requirement for joint formation. Up to now, spot friction welding has focused primarily on aluminum alloys. This paper presents a feasibility study on spot friction welding of AZ31, a wrought magnesium alloy available in sheet form. Lap joints of 1.58-mm-thick magnesium alloy AZ31B-O sheet were produced by spot friction welding. The spot welds were made in 2 sec with 15-mm-diameter pin tool rotating at 500-2,000 rpm. The tool was inserted into 2-sheet stack-ups to depths of either 2.4 or 2.8 mm relative to the top sheet surface. Tensile-shear testing showed that joint strengths up to 4.75 kN were obtained. The removal of surface oxides from the sheets prior to welding increased lap shear strengths about 50% at the 2.4-mm insertion depth and it promoted failure by nugget pull-out rather than by interface separation.

  13. Strain Rates and Grain Growth in Al 5754 and Al 6061 Friction Stir Spot Welds

    NASA Astrophysics Data System (ADS)

    Gerlich, A.; Yamamoto, M.; North, T. H.

    2007-06-01

    The stir zone temperature and microstructures are compared in friction stir spot welds produced in Al 5754 and Al 6061 alloys. Electron backscattered diffraction was used to determine the relationship between tool rotation speed during welding and final stir zone grain size. Comparison of the grain sizes in rapidly quenched welds with those in air-cooled joints confirmed that grain growth occurred only in Al 6061 spot welds. There was no evidence of abnormal grain growth in the stir zones of Al 6061 welds; the final grain size could be represented using an Arrhenius equation. The strain rates during welding were determined by incorporating the stir zone temperature and average subgrain sizes in quenched spot welds in the Zener-Hollomon relation. When the tool rotation speed increased from 750 to 3000 RPM, the strain rate values ranged from 180 to 497 s-1 in Al 5754 spot welds and from 55 to 395 s-1 in Al 6061 spot welds. It is suggested that a no-slip boundary condition may be appropriate during numerical modeling of Al 5754 and 6061 friction stir spot welding. This is not the case during Al 7075, Al 2024, and Mg-alloy AZ91 spot welding because spontaneous melting facilitates slippage at the tool contact interface.

  14. Stir zone microstructure and strain rate during Al 7075-T6 friction stir spot welding

    NASA Astrophysics Data System (ADS)

    Gerlich, A.; Avramovic-Cingara, G.; North, T. H.

    2006-09-01

    The factors determining the temperature, heating rate, microstructure, and strain rate in Al 7075-T6 friction stir spot welds are investigated. Stir zone microstructure was examined using a combination of transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) microscopy, while the strain rate during spot welding was calculated by incorporating measured temperatures and the average subgrain dimensions in the Zener-Hollomon relation. The highest temperature during friction stir spot welding (527 °C) was observed in spot welds made using a tool rotational speed of 3000 rpm. The stir zone regions comprised fine-grained, equiaxed, fully recrystallized microstructures. The calculated strain rate in Al 7075-T6 spot welds decreased from 650 to about 20 s-1 when the tool rotational speed increased from 1000 to 3000 rpm. It is suggested that the decrease in strain rate results when tool slippage occurs when the welding parameter settings facilitate transient local melting during the spot welding operation. Transient local melting and tool slippage are produced when the welding parameters produce sufficiently high heating rates and temperatures during spot welding. However, transient local melting and tool slippage is not produced in Al 7075-T6 spot welds made using a rotational speed of 1000 rpm since the peak temperature is always less than 475 °C.

  15. The Mechanical Behavior of Friction-Stir Spot Welded Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Güler, Hande

    2014-09-01

    Aluminum and alloys are widely used in the automotive industry due to the light weight, good formability, and malleability. Spot welding is the most commonly used joining method of these materials, but the high current requirements and the inconsistent quality of the final welds make this process unsuitable. An alternative welding technique, the friction-stir spot welding process, can also be successfully used in joining of aluminum and alloys. In this study, 1-mm-thick AA5754 Al-alloy plates in the H-111 temper conditions were joined by friction-stir spot welding using two different weld parameters such as tool rotational speed and dwell time. Mechanical properties of the joints were obtained with extensive hardness measurements and tensile shear tests. The effect of these parameters on the failure modes of welded joints was also determined.

  16. The Mechanical Behavior of Friction-Stir Spot Welded Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Güler, Hande

    2014-10-01

    Aluminum and alloys are widely used in the automotive industry due to the light weight, good formability, and malleability. Spot welding is the most commonly used joining method of these materials, but the high current requirements and the inconsistent quality of the final welds make this process unsuitable. An alternative welding technique, the friction-stir spot welding process, can also be successfully used in joining of aluminum and alloys. In this study, 1-mm-thick AA5754 Al-alloy plates in the H-111 temper conditions were joined by friction-stir spot welding using two different weld parameters such as tool rotational speed and dwell time. Mechanical properties of the joints were obtained with extensive hardness measurements and tensile shear tests. The effect of these parameters on the failure modes of welded joints was also determined.

  17. Microstructures and Mechanical Properties of Friction Stir Spot Welded Aluminum Alloy AA2014

    NASA Astrophysics Data System (ADS)

    Babu, S.; Sankar, V. S.; Janaki Ram, G. D.; Venkitakrishnan, P. V.; Madhusudhan Reddy, G.; Prasad Rao, K.

    2013-01-01

    Friction stir spot welding (FSSW) is a relatively recent development, which can provide a superior alternative to resistance spot welding and riveting for fabrication of aluminum sheet metal structures. In the current work, FSSW experiments were conducted in 3-mm thick sheets of aluminum alloy 2014 in T4 and T6 conditions, with and without Alclad layers. The effects of tool geometry and welding process parameters on joint formation were investigated. A good correlation between process parameters, bond width, hook height, joint strength, and fracture mode was observed. The presence of Alclad layers and the base metal temper condition were found to have no major effect on joint formation and joint strength. Friction stir spot welds produced under optimum conditions were found to be superior to riveted joints in lap-shear and cross-tension tests. The prospects of FSSW in aluminum sheet metal fabrication are discussed.

  18. Eutectic structures in friction spot welding joint of aluminum alloy to copper

    NASA Astrophysics Data System (ADS)

    Shen, Junjun; Suhuddin, Uceu F. H.; Cardillo, Maria E. B.; dos Santos, Jorge F.

    2014-05-01

    A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl2 eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.

  19. Eutectic structures in friction spot welding joint of aluminum alloy to copper

    SciTech Connect

    Shen, Junjun Suhuddin, Uceu F. H.; Cardillo, Maria E. B.; Santos, Jorge F. dos

    2014-05-12

    A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl{sub 2} eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.

  20. Friction welding.

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1972-01-01

    Results of an exploratory study of the structure and properties of friction welds in Udimet 700 (U-700) and TD-nickel (TD-Ni) bar materials, as well as dissimilar U-700/TD-Ni friction welds. Butt welds were prepared by friction welding 12.7-mm-diam U-700 bars and TD-Ni bars. Specimens for elevated temperature tensile and stress rupture testing were machined after a postweld heat treatment. Friction welding of U-700 shows great potential because the welds were found to be as strong as the parent metal in stress rupture and tensile tests at 760 and 980 C. In addition, the weld line was not detectable by metallographic examination after postheating. Friction welds in TD-Ni or between U-700 and TD-Ni were extremely weak at elevated temperatures. The TD-Ni friction welds could support only 9% as much stress as the base metal for 10-hour stress rupture life at 1090 C. The U-700/TD-Ni weld could sustain only 15% as much stress as the TD-Ni parent metal for a 10-hour stress rupture life at 930 C. Thus friction welding is not a suitable joining method for obtaining high-strength TD-Ni or U-700/TD-Ni weldments.

  1. Thermal Modeling of Al-Al and Al-Steel Friction Stir Spot Welding

    NASA Astrophysics Data System (ADS)

    Jedrasiak, P.; Shercliff, H. R.; Reilly, A.; McShane, G. J.; Chen, Y. C.; Wang, L.; Robson, J.; Prangnell, P.

    2016-07-01

    This paper presents a finite element thermal model for similar and dissimilar alloy friction stir spot welding (FSSW). The model is calibrated and validated using instrumented lap joints in Al-Al and Al-Fe automotive sheet alloys. The model successfully predicts the thermal histories for a range of process conditions. The resulting temperature histories are used to predict the growth of intermetallic phases at the interface in Al-Fe welds. Temperature predictions were used to study the evolution of hardness of a precipitation-hardened aluminum alloy during post-weld aging after FSSW.

  2. Friction Stir Spot Welding of DP780 and Hot-Stamp Boron Steels

    SciTech Connect

    Santella, Michael L; Frederick, David Alan; Hovanski, Yuri; Grant, Glenn J

    2008-01-01

    Friction stir spot welds were made in two high-strength steels: DP780, and a hot-stamp-boron steel with tensile strength of 1500 MPa. The spot welds were made at either 800 or 1600 rpm using either of two polycrystalline boron nitride tools. One stir tool, BN77, had the relatively common pin-tool shape. The second tool, BN46, had a convex rather than a concave shoulder profile and a much wider and shorter pin. The tools were plunged to preprogrammed depths either at a continuous rate (1-step schedule) or in two segments consisting of a relatively high rate followed by a slower rate. In all cases, the welds were completed in 4s. The range of lap-shear values were compared to values required for resistance spot welds on the same steels. The minimum value of 10.3 kN was exceeded for friction stir spot welding of DP780 using a 2-step schedule and either the BN77- or the BN46-type stir tool. The respective minimum value of 12 kN was also exceeded for the HSB steel using the 2-step process and the BN46 stir tool.

  3. Friction Stir Spot Welding of DP780 and Hot-Stamp Boron Steels

    SciTech Connect

    Santella, Michael L.; Frederick, Alan; Hovanski, Yuri; Grant, Glenn J.

    2008-05-16

    Friction stir spot welds were made in two high-strength steels: DP780, and a hot-stamp-boron steel with tensile strength of 1500 MPa. The spot welds were made at either 800 or 1600 rpm using either of two polycrystalline boron nitride tools. One stir tool, BN77, had the relatively common pin-tool shape. The second tool, BN46, had a convex rather than a concave shoulder profile and a much wider and shorter pin. The tools were plunged to preprogrammed depths either at a continuous rate (1-step schedule) or in two segments consisting of a relatively high rate followed by a slower rate. In all cases, the welds were completed in 4s. The range of lap-shear values were compared to values required for resistance spot welds on the same steels. The minimum value of 10.3 kN was exceeded for friction stir spot welding of DP780 using a 2-step schedule and either the BN77- or the BN46-type stir tool. The respective minimum value of 12 kN was also exceeded for the HSB steel using the 2-step process and the BN46 stir tool.

  4. Local melting and tool slippage during friction stir spot welding of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Gerlich, Adrian Piotr

    Local melting and tool slippage during friction stir spot welding of different aluminum alloys is examined using a combination of detailed microscopy and temperature measurement. It has been widely accepted that friction stir welding is a solid-state process and does not involve melting. The present research indicates that local melting is an inherent feature when Al 7075 and Al 2024 alloys are spot welded, and produces tool slippage at the tool contact interface. In contrast, intermetallic particles contained in the Al 5754 and Al 6061 as-received materials do not melt and a no-slip condition is maintained. A combination of data acquisition of key welding parameters (axial force, torque and tool displacement), high-speed imaging, temperature measurement and metallography are employed to study the tool penetration stage and the subsequent dwell period during spot welding. A methodology is developed for reliably determining the stir zone temperature using thermocouples embedded within the tool itself. Tool slippage is investigated by determining the strain rate in stir zone material adjacent to the rotating tool. The strain rate is estimated by substituting stir zone temperature and subgrain size measurements into the Zener-Hollomon equation. Tool penetration early in the friction stir spot welding process can be explained as a progression of wear events from mild (delamination) wear, through to severe wear, and finally to melt wear in the material located immediately under the tip of the rotating pin. The stir zone peak temperature during welding is limited by either the solidus temperature of the alloy in question, or by local melting of intermetallic particles contained in the base material such as Al 7075 or Al 2024 alloys. Melted films dissolve rapidly in the high temperature stir zone, and as the weld cools to room temperature. Metallographic evidence confirming local melting and cracking is observed in Al 7075 and Al 2024 alloy friction stir spot welds made

  5. Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)

    SciTech Connect

    Santella, M. L.; Hovanski, Yuri; Pan, Tsung-Yu

    2012-04-16

    Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si3N4 ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint. The joining mechanism was illustrated from the cross-section micrographs. Microhardness measurement showed hardening in the upper sheet steel (DP780GA or TRIP780) in the weld, but softening of HSBS in the heat-affect zone (HAZ). The study demonstrated the feasibility of making high-strength AHSS spot welds with low-cost tools.

  6. Joint strength in high speed friction stir spot welded DP 980 steel

    SciTech Connect

    Saunders, Nathan; Miles, Michael; Hartman, Trent; Hovanski, Yuri; Hong, Sung Tae; Steel, Russell

    2014-05-01

    High speed friction stir spot welding was applied to 1.2 mm thick DP 980 steel sheets under different welding conditions, using PCBN tools. The range of vertical feed rates used during welding was 2.5 mm – 102 mm per minute, while the range of spindle speeds was 2500 – 6000 rpm. Extended testing was carried out for five different sets of welding conditions, until tool failure. These welding conditions resulted in vertical welding loads of 3.6 – 8.2 kN and lap shear tension failure loads of 8.9 – 11.1 kN. PCBN tools were shown, in the best case, to provide lap shear tension fracture loads at or above 9 kN for 900 spot welds, after which tool failure caused a rapid drop in joint strength. Joint strength was shown to be strongly correlated to bond area, which was measured from weld cross sections. Failure modes of the tested joints were a function of bond area and softening that occurred in the heat-affected zone.

  7. MODELING OF HIGH SPEED FRICTION STIR SPOT WELDING USING A LAGRANGIAN FINITE ELEMENT APPROACH

    SciTech Connect

    Miles, Michael; Karki, U.; Woodward, C.; Hovanski, Yuri

    2013-09-03

    Friction stir spot welding (FSSW) has been shown to be capable of joining steels of very high strength, while also being very flexible in terms of controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding (RSW) if tool life is sufficiently high, and if machine spindle loads are sufficiently low so that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11-14 kN. Therefore, in the current work tool speeds of 3000 rpm and higher were employed, in order to generate heat more quickly and to reduce welding loads to acceptable levels. The FSSW process was modeled using a finite element approach with the Forge® software package. An updated Lagrangian scheme with explicit time integration was employed to model the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate [3]. The modeling approach can be described as two-dimensional, axisymmetric, but with an aspect of three dimensions in terms of thermal boundary conditions. Material flow was calculated from a velocity field which was two dimensional, but heat generated by friction was computed using a virtual rotational velocity component from the tool surface. An isotropic, viscoplastic Norton-Hoff law was used to model the evolution of material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures and the movement of the joint interface with reasonable accuracy for the welding of a dual phase 980 steel.

  8. Microstructure and Mechanical Performance of Friction Stir Spot-Welded Aluminum-5754 Sheets

    NASA Astrophysics Data System (ADS)

    Pathak, N.; Bandyopadhyay, K.; Sarangi, M.; Panda, Sushanta Kumar

    2013-01-01

    Friction stir spot welding (FSSW) is a recent trend of joining light-weight sheet metals while fabricating automotive and aerospace body components. For the successful application of this solid-state welding process, it is imperative to have a thorough understanding of the weld microstructure, mechanical performance, and failure mechanism. In the present study, FSSW of aluminum-5754 sheet metal was tried using tools with circular and tapered pin considering different tool rotational speeds, plunge depths, and dwell times. The effects of tool design and process parameters on temperature distribution near the sheet-tool interface, weld microstructure, weld strength, and failure modes were studied. It was found that the peak temperature was higher while welding with a tool having circular pin compared to tapered pin, leading to a bigger dynamic recrystallized stir zone (SZ) with a hook tip bending towards the upper sheet and away from the keyhole. Hence, higher lap shear separation load was observed in the welds made from circular pin compared to those made from tapered pin. Due to influence of size and hardness of SZ on crack propagation, three different failure modes of weld nugget were observed through optical cross-sectional micrograph and SEM fractographs.

  9. Material Interactions in a Novel Pinless Tool Approach to Friction Stir Spot Welding Thin Aluminum Sheet

    NASA Astrophysics Data System (ADS)

    Bakavos, Dimitrios; Chen, Yingchun; Babout, Laurent; Prangnell, Phil

    2011-05-01

    The requirement for a probe, or pin, in friction stir spot welding (FSSW) leads to an undesirable keyhole and "hooking," which can influence the fracture path and weld strength. Furthermore, the full weld cycle for FSSW is typically longer than ideal for the automotive industry, being 2 to 5 seconds. Here, it is shown that using a novel pinless tool design it is possible to achieve high lap shear strength (~3.4 kN) in thin aluminum sheet (~1 mm thick), with short weld cycle times (<1 second). Several techniques have been exploited to study the material flow and mechanisms of weld formation in pinless FSSW, including high-resolution X-ray tomography, to understand the role of the tool design and weld parameters. Despite the "simple" nature of a pinless tool, material flow in the weld zone was found to be surprisingly complex and strongly influenced by surface features on the tool, which greatly increased the penetration of the plastic zone into the bottom sheet. Because of the rapid thermal cycle and high level of grain refinement, the weld zone was found to develop a higher strength than the parent material with little evidence of a heat affected zone (HAZ) after postweld natural aging.

  10. Microstructural and Mechanical Characteristics of Aluminum Alloy AA5754 Friction Stir Spot Welds

    NASA Astrophysics Data System (ADS)

    Mahmoud, T. S.; Khalifa, T. A.

    2014-03-01

    In the present investigation, friction stir spot welding on annealed aluminum alloy AA5754 sheets was performed. The influences of the tool rotational speed and tool stirring (dwell) time on the weld structure and static strength of welds were evaluated. The results revealed that the width of the completely metallurgical-bonded region increases with the increasing tool rotational speed and/or the dwell time up to certain levels. Increasing such parameters beyond these levels slightly reduces the width of the bonding region. The stirred zone exhibited higher microhardness than that of the base material. The tensile-shear force was found to increase with the increasing tool rotational speed and/or dwell time up to a certain level (9s). Higher tool rotational speeds and/or prolonged dwell times slightly reduce(s) the tensile-shear force.

  11. Mechanical behaviour of a friction stir spot welding lap under static loading

    NASA Astrophysics Data System (ADS)

    Herbelot, C.; Hoang, T. Dang; Imad, A.; Benseddiq, N.

    2011-01-01

    Friction stir spot welding (FSSW) is a recent welding method which takes advantage of being performed in the solid state and presents many benefits such as a lower heat-input, a reduction of residual stresses and an elimination of the solidification defects for example. The present study investigates, for fixed process parameters and tool geometry, the fracture and damage of a single-lap friction stir spot welding joints formed from thin sheets of aluminum alloy 6082 T6. An experimental approach was carried out in order to analyze the sequence of damage mechanisms using acoustic emission (A.E.) and measurement of fields by digital image correlation (D.I.C.) techniques simultaneously. The A.E. technique allows the monitoring of the evolution of acoustic activities by taking into account energy of the events. The D.I.C. technique confirms the damage scenarios after the treatment of strain field at any point near the fastener and especially between the exit hole and the shoulder footprint. The coupling of those two techniques allows to identify characteristic points and a breakdown of the load displacement curve in phases.

  12. Application of laser ultrasonic method for on-line monitoring of friction stir spot welding process.

    PubMed

    Zhang, Kuanshuang; Zhou, Zhenggan; Zhou, Jianghua

    2015-09-01

    Application of a laser ultrasonic method is developed for on-line monitoring of the friction stir spot welding (FSSW) process. Based on the technology of FSSW, laser-generated ultrasonic waves in a good weld and nonweld area are simulated by a finite element method. The reflected and transmitted waves are analyzed to disclose the properties of the welded interface. The noncontact-laser ultrasonic-inspection system was established to verify the numerical results. The reflected waves in the good-weld and nonweld area can be distinguished by time-of-flight. The transmitted waves evidently attenuate in the nonweld area in contrast to signal amplitude in the good weld area because of interfacial impedance difference. Laser ultrasonic C-scan images can sufficiently evaluate the intrinsic character of the weld area in comparison with traditional water-immersion ultrasonic testing results. The research results confirm that laser ultrasonics would be an effective method to realize the characterization of FSSW defects. PMID:26368866

  13. Analysis of Temperature and Plastic Flow during Friction Stir Spot Welding Using Particle Method

    NASA Astrophysics Data System (ADS)

    Hirasawa, Shigeki; Badarinarayan, Harsha; Okamoto, Kazutaka; Tomimura, Toshio; Kawanami, Tsuyoshi; Hirano, Shigeki

    Friction stir spot welding (FSSW) is a new metal-joining process, and a numerical simulation code to calculate optimal welding conditions is desired. In this paper, we analyzed temperature distribution and plastic deformation flow during the FSSW process with the fluid flow model and the elastic-plastic deformation model using the particle method. Spot welds are made with a cylindrical pin tool having flat shoulder with a fixed tool rotational speed. Simulation results predict an axisymmetric temperature distribution with the temperature below the tool in the region of 300 °C. The material flow predicted by the elastic-plastic deformation model is similar to experimental results. The model predicts the material flow at the pin periphery is in the upward direction. Near the shoulder, there are two flow patterns observed - beneath the shoulder, the material is pushed downward due to the force acting from the shoulder face, whereas on the shoulder periphery the material flows upward and outward due to extrusion of the material that is caused by the shoulder plunge. This extruded material shows up on the specimen surface as burr.

  14. Effect of Rotational Speed on Microstructure and Mechanical Properties of Refill Friction Stir Spot Welded 2024 Al Alloy

    NASA Astrophysics Data System (ADS)

    Li, Zhengwei; Gao, Shuangsheng; Ji, Shude; Yue, Yumei; Chai, Peng

    2016-04-01

    Refill friction stir spot welding (RFSSW) was successfully used to weld alclad 2024 aluminum alloy with different thicknesses. Effects of tool rotational speed on the weld formation, microstructure, and mechanical properties of the RFSSW welds were mainly discussed. Results show that keyhole is successfully refilled and welding defects such as flash, annular groove, and material adhesion can be observed. A bright contrast bonding ligament is found embedded in the weld and it is thicker in the center. Defects of hook, void, lack of mixing, and incomplete refilling can be found at the thermo-mechanically affected zone/stir zone (TMAZ/SZ) interface, which can be attributed to weak metallurgical bonding effect. With increasing the tool rotational speed, thickness of the bonding ligament decreases, grains in the SZ coarsen, hardness of the SZ decreases, and lap shear load of the welds decreases. When changing the rotating speed, impact strength shows rather complicated variation trend.

  15. Wear testing of friction stir spot welding tools for joining of DP 980 Steel

    SciTech Connect

    Ridges, Chris; Miles, Michael; Hovanski, Yuri; Peterson, Jeremy; Steel, Russell

    2011-06-06

    Friction stir spot welding has been shown to be a viable method of joining ultra high strength steel (UHSS), both in terms of joint strength and process cycle time. However, the cost of tooling must be reasonable in order for this method to be adopted as an industrial process. Several tooling materials have been evaluated in prior studies, including silicon nitride and polycrystalline cubic boron nitride (PCBN). Recently a new tool alloy has been developed, where a blend of PCBN and tungsten rhenium (W-Re) was used in order to improve the toughness of the tool. Wear testing results are presented for two of these alloys: one with a composition of 60% PCBN and 40% W-Re (designated as Q60), and one with 70% PCBN and 30% W-Re (designated at Q70). The sheet material used for all wear testing was DP 980. Tool profiles were measured periodically during the testing process in order to show the progression of wear as a function of the number of spots produced. Lap shear testing was done each time a tool profile was taken in order to show the relationship between tool wear and joint strength. For the welding parameters chosen for this study the Q70 tool provided the best combination of wear resistance and joint strength.

  16. Impact of tool wear on joint strength in friction stir spot welding of DP 980 steel

    SciTech Connect

    Miles, Michael; Ridges, Chris; Hovanski, Yuri; Peterson, Jeremy; Santella, M. L.; Steel, Russel

    2011-09-14

    Friction stir spot welding has been shown to be a viable method of joining ultra high strength steel (UHSS), both in terms of joint strength and process cycle time. However, the cost of tooling must be reasonable in order for this method to be adopted as an industrial process. Recently a new tool alloy has been developed, using a blend of PCBN and tungsten rhenium (W-Re) in order to improve the toughness of the tool. Wear testing results are presented for two of these alloys: one with a composition of 60% PCBN and 40% W-Re, and one with 70% PCBN and 30% W-Re. The sheet material used for all wear testing was 1.4 mm DP 980. Lap shear testing was used to show the relationship between tool wear and joint strength. The Q70 tool provided the best combination of wear resistance and joint strength.

  17. Microstructure and Mechanical Properties of Friction Stir Spot-Welded IF/DP Dissimilar Steel Joints

    NASA Astrophysics Data System (ADS)

    Sarkar, Rajarshi; Sengupta, Shiladitya; Pal, Tapan Kumar; Shome, Mahadev

    2015-11-01

    Interstitial-free (IF) and dual-phase (DP) steel sheets of 1-mm thickness were joined by friction stir spot welding with a convex shoulder tool. Two different combinations were used; one with IF as top sheet (IF/DP) and another with DP as top sheet (DP/IF). Material intermixing between the overlapping sheets takes place within the stirred zone. The truncated sheet interface curls upward into the top sheet, more so in case of IF/DP, due to lower resistance offered by the top (IF) sheet to the upward migrating bottom (DP) sheet material. Material from the IF steel contains ferrite phases, while that from the DP steel contains acicular ferrite and lath martensite. Under quasi-static loading, the crack passes along the dissimilar interface and into the top sheet thickness, resulting in pull-out failure. Under cyclic loading, the failure is brought about by the initiation of kinked fatigue cracks and their subsequent propagation through the top and bottom sheet thickness. The dominant fatigue crack moves through the reduced top sheet thickness. The mechanical performance of DP/IF is better than IF/DP owing to higher strength of the stirred zone. The mechanical performances of the dissimilar joints are intermediate to that of the similar material joints.

  18. Material Flow Tracking for Various Tool Geometries During the Friction Stir Spot Welding Process

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Ching; Liu, Ju-Jen; Chen, Jiun-Nan

    2013-12-01

    This study applied powder-tracing techniques to mount Cu and W powders on A6061-T6 aluminum sheets to investigate the material flow mechanism of friction stir spot welding (FSSW) using various geometric tools. The experimental results showed that the geometry of the tools plays a crucial role and determines the entrances of material flow during FSSW. It was believed that instantaneous voids were filled up with material flow in all directions for triangular pins, and the voids were located at the pin bottom for cylindrical pins. In accordance with the plastic rule of material flow, the pressure gradient is the necessary condition to cause material flow during FSSW; therefore, the transient constraint space (TCS) is required to generate pressure in this space. Enlargement of the TCS accompanies the evolution of the stir zone (SZ). A generated void causes a steep pressure gradient, which is regarded as the entrance of material flow. A tool with screw threads causes downward driving force, which determines the intermixing behavior between the upper and lower sheets, and also affects the size of the SZs.

  19. Temperature and Material Flow Prediction in Friction-Stir Spot Welding of Advanced High-Strength Steel

    NASA Astrophysics Data System (ADS)

    Miles, M.; Karki, U.; Hovanski, Y.

    2014-10-01

    Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11-14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge® software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within 4%, and the position of the joint interface to within 10%, of the experimental results.

  20. Temperature and Material Flow Prediction in Friction-Stir Spot Welding of Advanced High-Strength Steel

    NASA Astrophysics Data System (ADS)

    Miles, M.; Karki, U.; Hovanski, Y.

    2014-09-01

    Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11-14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge® software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within 4%, and the position of the joint interface to within 10%, of the experimental results.

  1. Temperature and Material Flow Prediction in Friction-Stir Spot Welding of Advanced High-Strength Steel

    SciTech Connect

    Miles, Michael; Karki, U.; Hovanski, Yuri

    2014-10-01

    Friction-stir spot welding (FSSW) has been shown to be capable of joining advanced high-strength steel, with its flexibility in controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding if tool life is sufficiently high, and if machine spindle loads are sufficiently low that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8 kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11–14 kN. Therefore, in the current work, tool speeds of 5000 rpm were employed to generate heat more quickly and to reduce welding loads to acceptable levels. Si3N4 tools were used for the welding experiments on 1.2-mm DP 980 steel. The FSSW process was modeled with a finite element approach using the Forge* software. An updated Lagrangian scheme with explicit time integration was employed to predict the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate. Material flow was calculated from a velocity field that is two-dimensional, but heat generated by friction was computed by a novel approach, where the rotational velocity component imparted to the sheet by the tool surface was included in the thermal boundary conditions. An isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures to within percent, and the position of the joint interface to within 10 percent, of the experimental results.

  2. Friction plug welding

    NASA Technical Reports Server (NTRS)

    Takeshita, Riki (Inventor); Hibbard, Terry L. (Inventor)

    2001-01-01

    Friction plug welding (FPW) usage is advantageous for friction stir welding (FSW) hole close-outs and weld repairs in 2195 Al--Cu--Li fusion or friction stir welds. Current fusion welding methods of Al--Cu--Li have produced welds containing varied defects. These areas are found by non-destructive examination both after welding and after proof testing. Current techniques for repairing typically small (<0.25) defects weaken the weldment, rely heavily on welders' skill, and are costly. Friction plug welding repairs increase strength, ductility and resistance to cracking over initial weld quality, without requiring much time or operator skill. Friction plug welding while pulling the plug is advantageous because all hardware for performing the weld can be placed on one side of the workpiece.

  3. Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  4. Friction stir welding tool

    DOEpatents

    Tolle; Charles R. , Clark; Denis E. , Barnes; Timothy A.

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  5. Friction Stir Weld Tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  6. Friction stir weld tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  7. IR Spot Weld Inspect

    SciTech Connect

    Chen, Jian; Feng, Zhili

    2014-01-01

    In automotive industry, destructive inspection of spot welds is still the mandatory quality assurance method due to the lack of efficient non-destructive evaluation (NDE) tools. However, it is costly and time-consuming. Recently at ORNL, a new NDE prototype system for spot weld inspection using infrared (IR) thermography has been developed to address this problem. This software contains all the key functions that ensure the NDE system to work properly: system input/output control, image acquisition, data analysis, weld quality database generation and weld quality prediction, etc.

  8. IR Spot Weld Inspect

    Energy Science and Technology Software Center (ESTSC)

    2014-01-01

    In automotive industry, destructive inspection of spot welds is still the mandatory quality assurance method due to the lack of efficient non-destructive evaluation (NDE) tools. However, it is costly and time-consuming. Recently at ORNL, a new NDE prototype system for spot weld inspection using infrared (IR) thermography has been developed to address this problem. This software contains all the key functions that ensure the NDE system to work properly: system input/output control, image acquisition, datamore » analysis, weld quality database generation and weld quality prediction, etc.« less

  9. Orbital friction stir weld system

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Carter, Robert W. (Inventor)

    2001-01-01

    This invention is an apparatus for joining the ends of two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. The apparatus holds the two cylindrical sections together and provides back-side weld support as it makes a friction stir weld around the circumference of the joined ends.

  10. Impact Modeling of Spot Welds

    NASA Astrophysics Data System (ADS)

    Yancey, Robert N.

    2004-06-01

    Resistance spot welds in most current finite element crash models are characterized as a rigid link at the location of the weld which transfers the load but is not designed to fail. Newer weld elements in the popular finite element analysis codes include the option of incorporating a failure criteria for the weld element. As many automotive companies move towards the use of high-strength steels, the dynamic behavior of the spot welds will become increasingly important and the failure of any welds should be incorporated during the simulation. The failure criteria will be influenced by mesh size, weld element properties, weld element type, surrounding material properties, strain rate, and weld placement. The influence of some of these parameters using current spot weld modeling techniques will be discussed along with recommendations for future work in this area.

  11. Measurement of nugget size of spot weld by digital shearography

    NASA Astrophysics Data System (ADS)

    Yang, Lianxiang; Samala, Praveen R.; Liu, Sheng; Long, Kah Wah; Lee, Yung-Li

    2005-08-01

    Resistance spot welding is now widely used in the fabrication of sheet metals, mainly due to the cost and time considerations. Friction stir spot welding is getting more and more acceptance in the automotive industries. Such spot welds are found in nearly all products where sheet metal is joined. Obviously the quality of the spot weld has a direct impact on the quality of the product. The most important quality target of spot welds is the size of the weld nuggets. If the weld nuggets are improperly or incompletely formed, or the area surrounding the nugget is smaller than required, the structural integrity of the entire part may be uncertain. Furthermore these inconsistencies are usually internal and are seldom visible to optical inspection. This study is focused on the quality analysis of the spot welds by using "Digital Shearography". The paper mainly focuses on developing a novel, whole field technique for non-destructive inspecting the size of spot-welds, both for the resistance spot weld and the friction stir spot weld.

  12. Versatile Friction Stir Welding/Friction Plug Welding System

    NASA Technical Reports Server (NTRS)

    Carter, Robert

    2006-01-01

    A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

  13. Effect of formation and state of interface on joint strength in friction stir spot welding for advanced high strength steel sheets

    NASA Astrophysics Data System (ADS)

    Taniguchi, Koichi; Matsushita, Muneo; Ikeda, Rinsei; Oi, Kenji

    2014-08-01

    The tensile shear strength and cross tension strength of friction stir spot welded joints were evaluated in the cases of lap joints of 270 N/mm2 grade and 980 N/mm2 grade cold rolled steel sheets with respect to the stir zone area, hardness distribution, and interface condition between the sheets. The results suggested that both the tensile shear strength and cross tension strength were based on the stir zone area and its hardness in both grades of steel. The "hook" shape of the interface also affected the joint strength. However, the joining that occurred across the interfaces had a significant influence on the value of the joint strength in the case of the 270 N/mm2 grade steel.

  14. Deformation During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    White, Henry J.

    2002-01-01

    Friction Stir Welding (FSW) is a solid state welding process that exhibits characteristics similar to traditional metal cutting processes. The plastic deformation that occurs during friction stir welding is due to the superposition of three flow fields: a primary rotation of a radially symmetric solid plug of metal surrounding the pin tool, a secondary uniform translation, and a tertiary ring vortex flow (smoke rings) surrounding the tool. If the metal sticks to the tool, the plug surface extends down into the metal from the outer edge of the tool shoulder, decreases in diameter like a funnel, and closes up beneath the pin. Since its invention, ten years have gone by and still very little is known about the physics of the friction stir welding process. In this experiment, an H13 steel weld tool (shoulder diameter, 0.797 in; pin diameter, 0.312 in; and pin length, 0.2506 in) was used to weld three 0.255 in thick plates. The deformation behavior during friction stir welding was investigated by metallographically preparing a plan view sections of the weldment and taking Vickers hardness test in the key-hole region.

  15. Non-Dimensional Characterization of the Friction Stir/Spot Welding Process Using a Simple Couette Flow Model Part I: Constant Property Bingham Plastic Solution

    NASA Astrophysics Data System (ADS)

    Buck, Gregory A.; Langerman, Michael

    2004-06-01

    A simplified model for the material flow created during a friction stir/spot welding process has been developed using a boundary driven cylindrical Couette flow model with a specified heat flux at the inner cylinder for a Bingham plastic material. Non-dimensionalization of the constant property governing equations identified three parameters that influence the velocity and temperature fields. Analytic solutions to these equations are presented and some representative results from a parametric study (parameters chosen and varied over ranges expected for the welding of a wide variety of metals) are discussed. The results also provide an expression for the critical radius (location of vanishing material velocity) as functions of the relevant non-dimensional parameters. A final study was conducted in which values for the non-dimensional heat flux parameter were chosen to produce peak dimensional temperatures on the order of 80% of the melting temperature for a typical 2000 series aluminum. Under these conditions it was discovered that the ratio of the maximum rate of shear work within the material (viscous dissipation) to the rate of energy input at the boundary due to frictional heating, ranged from about 0.0005 % for the lowest pin tool rotation rate, to about 1.3 % for the highest tool rotation rate studied. Curve fits to previous Gleeble data taken for a number of aluminum alloys provide reasonable justification for the Bingham plastic constitutive model, and although these fits indicate a strong temperature dependence for critical flow stress and viscosity, this work provides a simple tool for more sophisticated model validation. Part II of this study will present numerical solutions for velocity and temperature fields resulting from the non-linear coupling of the momentum and energy equations created by temperature dependent transport properties.

  16. Laser based spot weld characterization

    NASA Astrophysics Data System (ADS)

    Jonietz, Florian; Myrach, Philipp; Rethmeier, Michael; Suwala, Hubert; Ziegler, Mathias

    2016-02-01

    Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contact-free, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

  17. Fatigue Damage Evaluation of Friction Stir Spot Welded Cross-Tension Joints Under Repeated Two-Step Force Amplitudes

    NASA Astrophysics Data System (ADS)

    Joy-A-Ka, Sutep; Ogawa, Yuki; Akebono, Hiroyuki; Kato, Masahiko; Sugeta, Atsushi; Sun, Yufeng; Fujii, Hidetoshi

    2015-06-01

    This paper investigates an approach to evaluate the fatigue damage of FSSW cross-tension specimens under two-step force amplitude conditions. In fatigue tests with repeated two-step force amplitude, the fatigue limit of the welded joint disappeared. However, the fatigue damage evaluation using the modified Miner's rule erred too much on the side of safety, as the modified Miner's rule tends to overestimate the damage by applied forces below the fatigue limit. Thus, it was determined that, within the testing conditions used in this study, the fatigue damage evaluation using Haibach's method yielded an accurate evaluation. In the case where significant plastic deformation caused by the applied force occurred near the welded zone, the cumulative fatigue damage value based on Miner's rule was often larger than unity. Therefore, it is important to consider a cumulative damage estimation that takes into account the effect of pre-strain from the high force amplitude.

  18. Certification of a weld produced by friction stir welding

    DOEpatents

    Obaditch, Chris; Grant, Glenn J

    2013-10-01

    Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

  19. Friction Stir Welding and Processing

    SciTech Connect

    Hovanski, Yuri; Carsley, John; Clarke, Kester D.; Krajewski, Paul E.

    2015-05-01

    With nearly twenty years of international research and collaboration in friction stir welding (FSW) and processing industrial applications have spread into nearly every feasible market. Currently applications exist in aerospace, railway, automotive, personal computers, technology, marine, cutlery, construction, as well as several other markets. Implementation of FSW has demonstrated diverse opportunities ranging from enabling new materials to reducing the production costs of current welding technologies by enabling condensed packaging solutions for traditional fabrication and assembly. TMS has sponsored focused instruction and communication in this technology area for more than fifteen years, with leadership from the Shaping and Forming Committee, which organizes a biannual symposium each odd year at the annual meeting. A focused publication produced from each of these symposia now comprises eight volumes detailing the primary research and development activities in this area over the last two decades. The articles assembled herein focus on both recent developments and technology reviews of several key markets from international experts in this area.

  20. Gimbaled-shoulder friction stir welding tool

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Lawless, Kirby G. (Inventor)

    2010-01-01

    A gimbaled-shoulder friction stir welding tool includes a pin and first and second annular shoulders coupled to the pin. At least one of the annular shoulders is coupled to the pin for gimbaled motion with respect thereto as the tool is rotated by a friction stir welding apparatus.

  1. Wiping Metal Transfer in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Much evidence suggests that as the friction stir pin-tool moves along a weld seam the displacement of metal takes place by a wiping action at the surface of a plug of metal that rotates with the tool. The wiping model is explained and some consequences for the friction stir welding process are drawn.

  2. Spot-Welding Gun Is Easy To Use

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E.; Nguyen, Francis H.

    1991-01-01

    Electrical-resistance spot-welding gun designed to produce more welds per unit time by decreasing technician's effort and fatigue. Vacuum cups on frame secure welding gun to workpiece while compressed air drives welding tip against workpiece to make spot resistance weld. When weld completed, vacuum in frame cups released so frame and gun moved to position of next spot weld.

  3. Method and device for frictional welding

    DOEpatents

    Peacock, H.B.

    1991-01-01

    A method for friction welding that produces a seal having essentially no gas porosity, comprises two rotationally symmetric, generally cylindrical members, spaced apart and coaxially aligned, that are rotated with respect to each other and brought together under high pressure. One member is preferably a generally cylindrical cannister that stores uranium within its hollow walls. The other member is preferably a generally cylindrical, hollow weld ring. An annular channel formed in the weld ring functions as an internal flash trap and is uniquely designed so that substantially all of the welding flash generated from the friction welding is directed into the channel`s recessed bottom. Also, the channel design limits distortion of the two members during the friction welding, process, further contributing to the complete seal that is obtained.

  4. Method and device for frictional welding

    DOEpatents

    Peacock, Harold B.

    1992-01-01

    A method for friction welding that produces a seal having essentially no gas porosity, comprises two rotationally symmetric, generally cylindrical members, spaced apart and coaxially aligned, that are rotated with respect to each other and brought together under high pressure. One member is preferably a generally cylindrical cannister that stores uranium within its hollow walls. The other member is preferably a generally cylindrical, hollow weld ring. An annular channel formed in the weld ring functions as an internal flash trap and is uniquely designed so that substantially all of the welding flash generated from the friction welding is directed into the channel's recessed bottom. Also, the channel design limits distortion of the two members during the friction welding process, further contributing to the complete seal that is obtained.

  5. Method and device for frictional welding

    DOEpatents

    Peacock, H.B.

    1992-10-13

    A method is described for friction welding that produces a seal having essentially no gas porosity, comprises two rotationally symmetric, generally cylindrical members, spaced apart and coaxially aligned, that are rotated with respect to each other and brought together under high pressure. One member is preferably a generally cylindrical canister that stores uranium within its hollow walls. The other member is preferably a generally cylindrical, hollow weld ring. An annular channel formed in the weld ring functions as an internal flash trap and is uniquely designed so that substantially all of the welding flash generated from the friction welding is directed into the channel's recessed bottom. Also, the channel design limits distortion of the two members during the friction welding process, further contributing to the complete seal that is obtained. 5 figs.

  6. Friction Stir Welding of Steel Alloys

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The friction stir welding process has been developed primarily for the welding of aluminum alloys. Other higher melting allows such, as steels are much more difficult to join. Special attention must be given to pin tool material selection and welding techniques. This paper addresses the joining of steels and other high melting point materials using the friction stir welding process. Pin tool material and welding parameters will be presented. Mechanical properties of weldments will also be presented. Significance: There are many applications for the friction stir welding process other than low melting aluminum alloys. The FSW process can be expanded for use with high melting alloys in the pressure vessel, railroad and ship building industries.

  7. Laser Peening Effects on Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Hatamleh, Omar

    2011-01-01

    Friction Stir Welding (FSW) is a welding technique that uses frictional heating combined with forging pressure to produce high strength bonds. It is attractive for aerospace applications. Although residual stresses in FSW are generally lower when compared to conventional fusion welds, recent work has shown that significant tensile residual stresses can be present in the weld after fabrication. Therefore, laser shock peening was investigated as a means of moderating the tensile residual stresses produced during welding. This slide presentation reviews the effect of Laser Peening on the weld, in tensile strength, strain, surface roughness, microhardness, surface wear/friction, and fatigue crack growth rates. The study concluded that the laser peening process can result in considerable improvement to crack initiaion, propagation and mechanical properties in FSW.

  8. Macrostructure of Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Aloor, S.; Nowak, B.; Vargas, R.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    This paper will discuss two of the well know large scale features of friction stir welds: the "onion rings" seen in transverse sections, and the striations on the surface of the work piece. It will be shown that the surface features (sometimes called "tool marks") are the result of irregularities on the rotating shoulder of the pin tool and disappear when the shoulder is polished. The "onion ring" structure seen in transverse cross sections is formed by parts of the "carousel", the zone of material adjacent to and rotating with the pin tool, that are shed off in each rotation. The relation between the carousel and the "ring vortex", a rotational flow extending both in and out of the carousel and resembling a smoke-ring with the hole centered on the pin tool, will be discussed.

  9. Recent Developments in Friction Stir Welding of Al-alloys

    NASA Astrophysics Data System (ADS)

    Çam, Gürel; Mistikoglu, Selcuk

    2014-06-01

    The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).

  10. The Effect of Friction on Penetration in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Rapp, Steve

    2002-01-01

    "Friction stir butt welding," as it was originally termed by Wayne Thomas and Christopher Dawes, in the early 1990s, but now commonly called "friction stir welding," has made great progress as a new welding technique. Marshall Space Flight Center has been investigating the use of FSW for assembly of the Shuttle's external fuel tank since the late 1990s and hopes to have the process in use by the summer of 2002. In FSW, a cylindrical pin tool of hardened steel, is rotated and plunged into the abutting edges of the parts to be joined. The tool is plunged into the weldment to within about .050 in of the bottom to assure full penetration. As the tool moves along the joint, the tool shoulder helps produce frictional heating, causing the material to plasticize. The metal of the two abutting plates flows from the front of the tool to the back where it cools and coalesces to form a weld in the solid phase. One quarter inch thick plates of aluminum alloy 2219 were used in this study. Two samples, each consisting of two 4 in x 12 in plates, were friction stir welded. The anvil for one sample was coated with molybdenum sulfide, while for the other sample a sheet of roughened stainless steel was placed between the anvil and the sample. The retractable pin tool was used so that the depth of the pin tool penetration could be varied. As welding proceeded, the length of the pin tool was gradually increased from the starting point. The purpose of this investigation is to find out at what point, in the down ramp, penetration occurs. Differences in root structure of the friction stir weld due to differences in anvil friction will be observed. These observations will be analyzed using friction stir weld theory.

  11. Friction Pull Plug Welding in Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Brooke, Shane A.; Bradford, Vann

    2012-01-01

    NASA's Marshall Space Flight Center (MSFC) has recently invested much time and effort into the process development of Friction Pull Plug Welding (FPPW). FPPW, is a welding process similar to Friction Push Plug Welding in that, there is a small rotating part (plug) being spun and simultaneously pulled (forged) into a larger part. These two processes differ, in that push plug welding requires an internal reaction support, while pull plug welding reacts to the load externally. FPPW was originally conceived as a post proof repair technique for the Space Shuttle fs External Tank. FPPW was easily selected as the primary weld process used to close out the termination hole on the Constellation Program's ARES I Upper Stage circumferential Self-Reacting Friction Stir Welds (SR-FSW). The versatility of FPPW allows it to also be used as a repair technique for both SR-FSW and Conventional Friction Stir Welds. To date, all MSFC led development has been concentrated on aluminum alloys (2195, 2219, and 2014). Much work has been done to fully understand and characterize the process's limitations. A heavy emphasis has been spent on plug design, to match the various weldland thicknesses and alloy combinations. This presentation will summarize these development efforts including weld parameter development, process control, parameter sensitivity studies, plug repair techniques, material properties including tensile, fracture and failure analysis.

  12. Friction Pull Plug Welding in Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Brooke, Shane A.; Bradford, Vann; Burkholder, Jonathon

    2011-01-01

    NASA fs Marshall Space Flight Center (MSFC) has recently invested much time and effort into the process development of Friction Pull Plug Welding (FPPW). FPPW, is a welding process similar to Friction Push Plug Welding in that, there is a small rotating part (plug) being spun and simultaneously pulled (forged) into a larger part. These two processes differ, in that push plug welding requires an internal reaction support, while pull plug welding reacts to the load externally. FPPW was originally conceived as a post proof repair technique for External Tank. FPPW was easily selected as the primary process used to close out the termination hole on the Constellation Program fs ARES I Upper Stage circumferential Self ] Reacting Friction Stir Welds (SR ]FSW). The versatility of FPPW allows it to also be used as a repair technique for both SR ]FSW and Conventional Friction Stir Welds. To date, all MSFC led development has been concentrated on aluminum alloys (2195, 2219, and 2014). Much work has been done to fully understand and characterize the process fs limitations. A heavy emphasis has been spent on plug design, to match the various weldland thicknesses and alloy combinations. This presentation will summarize these development efforts including weld parameter development, process control, parameter sensitivity studies, plug repair techniques, material properties including tensile, fracture and failure analysis.

  13. Friction stir welding tool and process for welding dissimilar materials

    DOEpatents

    Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

    2013-05-07

    A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

  14. Comparing Laser Welding Technologies with Friction Stir Welding for Production of Aluminum Tailor-Welded Blanks

    SciTech Connect

    Hovanski, Yuri; Carsley, John; Carlson, Blair; Hartfield-Wunsch, Susan; Pilli, Siva Prasad

    2014-01-15

    A comparison of welding techniques was performed to determine the most effective method for producing aluminum tailor-welded blanks for high volume automotive applications. Aluminum sheet was joined with an emphasis on post weld formability, surface quality and weld speed. Comparative results from several laser based welding techniques along with friction stir welding are presented. The results of this study demonstrate a quantitative comparison of weld methodologies in preparing tailor-welded aluminum stampings for high volume production in the automotive industry. Evaluation of nearly a dozen welding variations ultimately led to down selecting a single process based on post-weld quality and performance.

  15. Gimballed Shoulders for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert; Lawless, Kirby

    2008-01-01

    In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding. Some definitions of terms, recapitulated from related prior NASA Tech Briefs articles, are prerequisite to a meaningful description of the proposed improvement. In friction stir welding, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a pin that rotates with the shoulder and protrudes from the shoulder into the depth of the workpiece. In conventional friction stir welding, the main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional friction stir welding is augmented with an auto-adjustable pin-tool (APT) capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or forcecontrol system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding as practiced heretofore, there are two shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. Both shoulders rotate with the pin and remain aligned coaxially with the pin. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft into the friction-stir-welding machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. This concludes the prerequisite definitions of terms.

  16. A fundamental study on the structural integrity of magnesium alloys joined by friction stir welding

    NASA Astrophysics Data System (ADS)

    Rao, Harish Mangebettu

    The goal of this research is to study the factors that influence the physical and mechanical properties of lap-shear joints produced using friction stir welding. This study focuses on understanding the effect of tool geometry and weld process parameters including the tool rotation rate, tool plunge depth and dwell time on the mechanical performance of similar magnesium alloy and dissimilar magnesium to aluminum alloy weld joints. A variety of experimental activities were conducted including tensile and fatigue testing, fracture surface and failure analysis, microstructure characterization, hardness measurements and chemical composition analysis. An investigation on the effect of weld process conditions in friction stir spot welding of magnesium to magnesium produced in a manner that had a large effective sheet thickness and smaller interfacial hook height exhibited superior weld strength. Furthermore, in fatigue testing of friction stir spot welded of magnesium to magnesium alloy, lap-shear welds produced using a triangular tool pin profile exhibited better fatigue life properties compared to lap-shear welds produced using a cylindrical tool pin profile. In friction stir spot welding of dissimilar magnesium to aluminum, formation of intermetallic compounds in the stir zone of the weld had a dominant effect on the weld strength. Lap-shear dissimilar welds with good material mixture and discontinues intermetallic compounds in the stir zone exhibited superior weld strength compared to lap-shear dissimilar welds with continuous formation of intermetallic compounds in the stir zone. The weld structural geometry like the interfacial hook, hook orientation and bond width also played a major role in influencing the weld strength of the dissimilar lap-shear friction stir spot welds. A wide scatter in fatigue test results was observed in friction stir linear welds of aluminum to magnesium alloys. Different modes of failure were observed under fatigue loading including crack

  17. Self-Reacting Friction Stir Welding for Aluminum Alloy Circumferential Weld Applications

    NASA Technical Reports Server (NTRS)

    Bjorkman, Gerry; Cantrell, Mark; Carter, Robert

    2003-01-01

    Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation. The high weld forge force is reacted against an anvil and a stout tool structure. A variation of friction stir welding currently being evaluated is self-reacting friction stir welding. Self-reacting friction stir welding incorporates two opposing shoulders on the crown and root sides of the weld joint. In self-reacting friction stir welding, the weld forge force is reacted against the crown shoulder portion of the weld pin tool by the root shoulder. This eliminates the need for a stout tooling structure to react the high weld forge force required in the typical friction stir weld process. Therefore, the self-reacting feature reduces tooling requirements and, therefore, process implementation costs. This makes the process attractive for aluminum alloy circumferential weld applications. To evaluate the application of self-reacting friction stir welding for aluminum alloy circumferential welding, a feasibility study was performed. The study consisted of performing a fourteen-foot diameter aluminum alloy circumferential demonstration weld using typical fusion weld tooling. To accomplish the demonstration weld, weld and tack weld development were performed and fourteen-foot diameter rings were fabricated. Weld development consisted of weld pin tool selection and the generation of a process map and envelope. Tack weld development evaluated gas tungsten arc welding and friction stir welding for tack welding rings together for circumferential welding. As a result of the study, a successful circumferential demonstration weld was produced leading

  18. Laser spot welding of electronic micro parts

    NASA Astrophysics Data System (ADS)

    Ostendorf, Andreas; Temme, Thorsten; Zeadan, Jeihad

    2004-10-01

    This paper deals with parameter optimization and online monitoring of laser spot welding (LSW). Using Nd:YAG laser, a wide range of experiments regarding the welding process have been carried out for both successful and failed welds. The typical failures appearing during packaging of surface mounted devices (SMDs) on flexible printed circuits (FPC) include gaps, a loss of connection between the welded components, and damage of the printed circuit boards. A flip-flop device called SO16 and lead frames as two components of widely used SMDs were packaged on FPCs in the experiments. The reproducibility of the weld quality for SO16 (FeNi) is greater than for lead frames (CuFe2P); this points out the difficulties appearing during copper or copper alloy welding. However, a correlation between the weld quality and the detected emission signals recorded during the weld process has been found for both components. The detected signals of the optical process emission for successful welds depict identical characterisics which are divided into three relevant signal phases. Changes in the signal characteristics, especially in these phases, imply information about the weld quality. While monitoring the welding processes for both components are possible, the detected signals for SO16 are less sensitive to process variations compared to those for lead frames. Based on spectral analysis, the intensity of the detected emission due to SO16 welding is slightly higher than the intensity due to lead frames welding.

  19. Ferrous friction stir weld physical simulation

    NASA Astrophysics Data System (ADS)

    Norton, Seth Jason

    2006-04-01

    Traditional fusion welding processes have several drawbacks associated with the melting and solidification of metal. Weld defects associated with the solidification of molten metal may act as initiation sites for cracks. Segregation of alloying elements during solidification may cause local changes in resistance to corrosion. The high amount of heat required to produce the molten metal in the weld can produce distortion from the intended position on cooling. The heat from the electric arc commonly used to melt metal in fusion welds may also produce metal fumes which are a potential health hazard. Friction stir welding is one application which has the potential to make full thickness welds in a single pass, while eliminating fume, reducing distortion, and eliminating solidification defects. Currently the friction stir welding process is used in the aerospace industry on aluminum alloys. Interest in the process by industries which rely on iron and its alloys for structural material is increasing. While friction stir welding has been shown to be feasible with iron alloys, the understanding of friction stir welding process effects on these materials is in its infancy. This project was aimed to better that understanding by developing a procedure for physical simulation of friction stir welding. Friction stir weld material tracer experiments utilizing stainless steel markers were conducted with plates of ingot iron and HSLA-65. Markers of 0.0625" diameter 308 stainless steel worked well for tracing the end position of material moved by the friction stir welding tool. The markers did not produce measurable increases in the loading of the tool in the direction of travel. Markers composed of 0.25" diameter 304 stainless steel did not perform as well as the smaller markers and produced increased loads on the friction stir welding tool. The smaller markers showed that material is moved in a curved path around the tool and deposited behind the tool. Material near the surface

  20. Deconvoluting the Friction Stir Weld Process for Optimizing Welds

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C.

    2008-01-01

    In the friction stir welding process, the rotating surfaces of the pin and shoulder contact the weld metal and force a rotational flow within the weld metal. Heat, generated by the metal deformation as well as frictional slippage with the contact surface, softens the metal and makes it easier to deform. As in any thermo-mechanical processing of metal, the flow conditions are critical to the quality of the weld. For example, extrusion of metal from under the shoulder of an excessively hot weld may relax local pressure and result in wormhole defects. The trace of the weld joint in the wake of the weld may vary geometrically depending upon the flow streamlines around the tool with some geometry more vulnerable to loss of strength from joint contamination than others. The material flow path around the tool cannot be seen in real time during the weld. By using analytical "tools" based upon the principles of mathematics and physics, a weld model can be created to compute features that can be observed. By comparing the computed observations with actual data, the weld model can be validated or adjusted to get better agreement. Inputs to the model to predict weld structures and properties include: hot working properties ofthe metal, pin tool geometry, travel rate, rotation and plunge force. Since metals record their prior hot working history, the hot working conditions imparted during FSW can be quantified by interpreting the final microstructure. Variations in texture and grain size result from variations in the strain accommodated at a given strain rate and temperature. Microstructural data from a variety of FSWs has been correlated with prior marker studies to contribute to our understanding of the FSW process. Once this stage is reached, the weld modeling process can save significant development costs by reducing costly trial-and-error approaches to obtaining quality welds.

  1. Ocular hazards of industrial spot welding.

    PubMed

    Chou, B R; Cullen, A P

    1996-06-01

    Any welding process is perceived to be a radiation hazard to the eye. Site visits were made to an automotive assembly plant to assess the levels of optical radiation and other hazards on the production line. Measurements were taken with a scanning spectro-radiometer and optical power and energy meters at operating working distances at spot welding stations where nonrobotic procedures were performed. Ultraviolet (UV) irradiance levels produced while spot welding with electrodes operating at 10 to 15 kA and 10 to 20 V were several orders of magnitude below recommended safety limits for industrial exposure. Flashes were rich in visible light and infrared (IR) radiation, but not at hazardous levels. The principal hazards in manual spot welding with high-current electrodes are high-speed droplets of molten metal produced by the process. These are easily defended against by wraparound polycarbonate eye shields. PMID:8807655

  2. Nuclear Fuel Plate Fabrication Employing Friction Welding

    SciTech Connect

    Douglas E. Burkes; Neil P. Hallinan; Curtis R. Clark

    2008-09-01

    This paper provides an overview of the friction bonding process, a novel modification of the more conventional friction stir welding process. The process has been modified to enable the fabrication of plate-type nuclear fuels for the conversion of research and test reactors currently operating using highly enriched uranium to low-enriched uranium. Discussions related to the specific modifications of the friction bonding process have been provided, in addition to challenges associated with these modifications. Progression of the process and solutions to the challenges are provided so that users of the friction stir welding process and those investigating fabrication of other laminar composites, where joining of one or more layers is essential, might draw from the authors’ experiences discussed in this paper.

  3. Nondestructive Ultrasonic Inspection of Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Tabatabaeipour, M.; Hettler, J.; Delrue, S.; Van Den Abeele, K.

    Friction Stir Welding (FSW) is a relatively new solid-state welding procedure developed at The Welding Institute (TWI-UK) and the technique is widely employed for welding aluminum alloys in various applications. In order to examine the quality of the welds and to detect a variety of welding flaws such as wormholes and root-flaws, it is required to develop a methodical inspection technique that can be used for the identification and localization of such defects. The most prevalent and risky defect in this type of welding is the barely visible root flaw with a length varying from 100-700 μm. Due to the extreme characteristics of the flaw, off-the-shelf ultrasonic weld inspection methods are not always able to readily detect this type of minute defect feature. Here, we propose a novel approach to characterize root flaws using an oblique incident ultrasonic C-scan backscattering analysis. The implementation consists of an immersion ultrasonic testing method in pulse echo (i.e. backscatter) mode with a 3.5 MHz transducer, and makes use of an empirical procedure to engender of a shear wave dominated excitation at the root surface, and to properly gate the received signal for root flaw examination. By scanning the surface above the welded component, a C-scan image displaying the backscatter response from the root surface of the nugget zone can be obtained which allows a simple interpretation of the root flaw status of the weld.

  4. Spot-Welding Gun With Pivoting Twin-Collet Assembly

    NASA Technical Reports Server (NTRS)

    Nguyen, Francis; Simpson, Gareth; Hoult, William S.

    1996-01-01

    Modified spot-welding gun includes pivoting twin-collet assembly that holds two spot-welding electrodes. Designed to weld highly conductive (30 percent gold) brazing-alloy foils to thin nickel alloy workpieces; also suitable for other spot-welding applications compatible with two-electrode configuration.

  5. Tool For Friction Stir Tack Welding of Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Bjorkman, Gerald W.; Dingler, Johnny W.; Loftus, Zachary

    2003-01-01

    A small friction-stir-welding tool has been developed for use in tack welding of aluminum-alloy workpieces. It is necessary to tack-weld the workpieces in order to hold them together during friction stir welding because (1) in operation, a full-size friction-stir-welding tool exerts a large force that tends to separate the workpieces and (2) clamping the workpieces is not sufficient to resist this force. It is possible to tack the pieces together by gas tungsten arc welding, but the process can be awkward and time-consuming and can cause sufficient damage to necessitate rework. Friction stir tack welding does not entail these disadvantages. In addition, friction stir tack welding can be accomplished by use of the same automated equipment (except for the welding tool) used in subsequent full friction stir welding. The tool for friction stir tack welding resembles the tool for full friction stir welding, but has a narrower shoulder and a shorter pin. The shorter pin generates a smaller workpiece-separating force so that clamping suffices to keep the workpieces together. This tool produces a continuous or intermittent partial-penetration tack weld. The tack weld is subsequently consumed by action of the larger tool used in full friction stir welding tool.

  6. Damage Tolerance Assessment of Friction Pull Plug Welds

    NASA Technical Reports Server (NTRS)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process developed and patented by The Welding Institute in Cambridge, England. Friction stir welding has been implemented in the aerospace industry in the fabrication of longitudinal welds in pressurized cryogenic propellant tanks. As the industry looks to implement friction stir welding in circumferential welds in pressurized cryogenic propellant tanks, techniques to close out the termination hole associated with retracting the pin tool are being evaluated. Friction pull plug welding is under development as a one means of closing out the termination hole. A friction pull plug weld placed in a friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite, plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size in the test or service environments. Test data relating residual strength capability to flaw size in two aluminum alloy friction plug weld configurations is presented.

  7. Tool Forces Developed During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Tang, W.; Schmidt, C.; McClure, J. C.; Nunes, A. C.; Murr, L. E.

    2003-01-01

    This paper will describe a technique for measuring the various forces and the torque that exist on the Friction Stir Welding pin tool. Results for various plunge depths, weld speeds, rotational speed, and tool configurations will be presented. Welds made on 6061 aluminum with typical welding conditions require a downward force of 2800 lbs. (12.5 kN) a longitudinal force in the direction of motion of 300 lbs (1.33 kN), a transverse force in the omega x v direction of 30 lbs (135 N). Aluminum 2195 under typical weld conditions requires a downward force of 3100 lbs. (1.38 kN), a longitudinal force of 920 lbs. (4.1 kN), and a transverse force of 45 lbs. (200 N) in the omega x v direction.

  8. Microstructure analysis in friction welding of copper and aluminum

    NASA Astrophysics Data System (ADS)

    Wibowo, A. G. Wahyu; Ismail, Rifky; Jamari, J.

    2016-04-01

    The Friction welding is a welding method with utilizing heat generated due to friction. Surfaces of two materials to be joined, one rotates the other being idle, is contacted by a pressure force. Friction on the second contact surface is done continuously so that the heat generated by the continuous friction will continue to rise. With the heat and the pressure force on the second surface to the second meeting of the material reaches its melting temperature then there is the process of welding. This paper examines the influence of the pressure force, rotational speed and contact time on friction welding of Aluminum (Al) and Copper (Cu) to the quality of welded joints. Friction welding process is performed on a friction welding machine that is equipped with the loading mechanism. The parameters used are the pressure force, rotational speed and friction time. Determination of the quality of welding is done by testing the tensile strength, hardness, and micro structure on the weld joint areas. The results showed that the friction welding quality is very good, this is evidenced by the results of a tensile strength test where the fault occurs outside the weld joint and increased violence in the weld joint. On the results visually cuts the welding area did not reveal any porosity so that it can be concluded that each metal contacts have melted perfectly and produce a connection with good quality.

  9. Flow Patterns During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Guerra, M.; Schmidt, C.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Friction Stir Welding is a relatively new technique for welding that uses a cylindrical pin or nib inserted along the weld seam. The nib (usually threaded) and the shoulder in which it is mounted are rapidly rotated and advanced along the seam. Extreme deformation takes place leaving a fine equiaxed structure in the weld region., The flow of metal during Friction Stir Welding is investigated using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a zone of material that rotates and advances with the nib. The material undergoes a helical motion within the rotational zone that both rotates and advances and descends in the wash of the threads on the nib and rises on the outer part of the rotational zone. After one or more rotations, this material is sloughed off in its wake of the nib, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side.

  10. Effects of Fusion Tack Welds on Self-Reacting Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Pendleton, M. L.; Brooke, S. A.; Russell, C. K.

    2012-01-01

    In order to know whether fusion tack welds would affect the strength of self-reacting friction stir seam welds in 2195-T87 aluminum alloy, the fracture stresses of 144 tensile test coupons cut from 24 welded panels containing segments of friction stir welds were measured. Each of the panels was welded under unique processing conditions. A measure of the effect of the tack welds for each panel was devised. An analysis of the measures of the tack weld effect supported the hypothesis that fusion tack welds do not affect the strength of self-reacting friction stir welds to a 5% level of confidence.

  11. Metal Flow in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2006-01-01

    The plastic deformation field in Friction Stir Welding (FSW) is compared to that in metal cutting. A shear surface around the FSW tool analogous to the metal cutting shear plane is identified and comprises the basis of the "rotating plug" flow field model and the "wiping" model of tool interaction with weld metal. Within the context of these models: The FSW shear rate is estimated to be comparable to metal cutting shear rates. The effect of tool geometry on the FSW shear surface is discussed and related to published torque measurements. Various FS W structural features are explained, including a difference in structure of bimetallic welds when alloys on the advancing and retreating sides of the weld seam are exchanged. The joining mechanism and critical parameters of the FSW process are made clear.

  12. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur; McClure, John; Avila, Ricardo

    2005-01-01

    Torque and plunge force during the initial plunge phase in Friction Stir Welding were measured for a 0.5 inch diameter pin entering a 2219 aluminum alloy plate. Weld structures were preserved for metallographic observation by making emergency stops at various plunge depths. The plunging pin tool is seen to be surrounded by a very fine grained layer of recrystallized metal extending substantially below the bottom of the pin, implying a shear interface in the metal below and not at the tool-metal interface. Torque and plunge force during the initial plunge phase in Friction Stir Welding are calculated from a straight forward model based on a concept to plastic flow in the vicinity of the plunging tool compatible with structural observations. The concept: a disk of weld metal seized to and rotating with the bottom of the pin is squeezed out laterally by the plunge force and extruded upwards in a hollow cylinder around the tool. As the shear surface separating rotating disk from stationary weld metal engulfs fresh metal, the fresh metal is subjected to severe shear deformation, which results in its recrystallization. Encouraging agreement between computations and measured torque and plunge force is obtained.

  13. A Brief Introduction to the Theory of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and is already an important welding process for the aerospace industry, where welds of optimal quality are demanded. The structure of welds determines weld properties. The structure of friction stir welds is determined by the flow field in the weld metal in the vicinity of the weld tool. A simple kinematic model of the FSW flow field developed at Marshall Space Flight Center, which enables the basic features of FSW microstructure to be understood and related to weld process parameters and tool design, is explained.

  14. Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

  15. Initial Study of Friction Pull Plug Welding

    NASA Technical Reports Server (NTRS)

    Rich, Brian S.

    1999-01-01

    Pull plug friction welding is a new process being developed to conveniently eliminate defects from welded plate tank structures. The general idea is to drill a hole of precise, optimized dimensions and weld a plug into it, filling the hole perfectly. A conically-shaped plug is rotated at high angular velocity as it is brought into contact with the plate material in the hole. As the plug is pulled into the hole, friction rapidly raises the temperature to the point at which the plate material flows plastically. After a brief heating phase, the plug rotation is terminated. The plug is then pulled upon with a forging force, solidly welding the plug into the hole in the plate. Three aspects of this process were addressed in this study. The transient temperature distribution was analyzed based on slightly idealized boundary conditions for different plug geometries. Variations in hole geometry and ram speed were considered, and a program was created to calculate volumes of displaced material and empty space, as well as many other relevant dimensions. The relation between the axially applied forging force and the actual forging pressure between the plate and plug surfaces was determined for various configurations.

  16. Effects of friction stir welding on microstructure of 7075 aluminum

    SciTech Connect

    Rhodes, C.G.; Mahoney, M.W.; Bingel, W.H.; Spurling, R.A.; Bampton, C.C.

    1997-01-01

    Friction stir welding is a relatively new technique developed by The Welding Institute (TWI) for the joining of aluminum alloys. The technique, based on friction heating at the faying surfaces of two pieces to be joined, results in a joint created by interface deformation, heat, and solid-state diffusion. In evaluating friction stir welding, critical issues (beyond a sound joint) include microstructure control and localized mechanical property variations. A serious problem with fusion welding, even when a sound weld can be made, is the complete alteration of microstructure and the attendant loss of mechanical properties. Being a solid-state process, friction stir welding has the potential to avoid significant changes in microstructure and mechanical properties. The objective of this study was to evaluate the microstructural changes effected by friction stir welding of 7075 Al.

  17. Attachment of marine fasteners utilizing portable friction stud welding systems

    SciTech Connect

    Grey, I.C.; Steel, R.L.

    1995-10-01

    A fast, economical and structurally reliable method for attachment of fasteners in marine environments has long been sought by engineers and marine structure owners. A new portable friction stud welding system is one possible solution. The paper will present an explanation of friction welding, a description of portable friction stud welding equipment, as well as laboratory test results evidencing the integrity of this method of material joining. A method of providing improved electrical continuity is also presented.

  18. Mechanistic Models of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Stewart, Michael B.

    1998-01-01

    Friction stir welding is a welding process developed at The Welding Institute (TWI) in England. The method uses very large strain plastic deformation of the material to join two pieces of metal together. The material is deformed using a tool which is forced between the two pieces which rotates causing a bond. Beyond this, very little is actually known although many people working in the field are willing to speculate on the detailed mechanisms involved. Some measurements made using sacrificial thermocouples at the weld joint indicate that the maximum temperature during the weld process is on the order of 370C - well below the melting temperature of the material. However, at this temperature, the material properties are highly temperature dependent, and the yield stress is approximately an order of magnitude less at this temperature than it is at room temperature. As expected, there are many interpretations of the physical mechanisms occurring during the weld process. Although there is very little published concerned with FSW, some of the anecdotal theories will be described. One describes the primary mechanism as frictional heating at the front of the tool caused by slip between the tool and the material. At elevated temperatures, the weld material becomes soft and deforms around the tool but not essentially altered by the tool rotation, similar to an extrusion. As the material meets again at the rear of the tool, the temperatures and pressures are sufficient to cause the material to bond. All other structures seen are secondary and unimportant. Another theory examined last summer at NASA's Marshall Space Flight Center (MSFC) was that there was no slip between the tool and the material resulting in a rotating mass of plastic weld material traveling at a variety of angular velocities - the greatest at the tool surface diminishing to zero at the outer edge of the plastic mass surrounding the tool. This conceptual model was followed by simplified calculations which

  19. Friction Stir Welding at MSFC: Kinematics

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.

    2001-01-01

    In 1991 The Welding Institute of the United Kingdom patented the Friction Stir Welding (FSW) process. In FSW a rotating pin-tool is inserted into a weld seam and literally stirs the faying surfaces together as it moves up the seam. By April 2000 the American Welding Society International Welding and Fabricating Exposition featured several exhibits of commercial FSW processes and the 81st Annual Convention devoted a technical session to the process. The FSW process is of interest to Marshall Space Flight Center (MSFC) as a means of avoiding hot-cracking problems presented by the 2195 aluminum-lithium alloy, which is the primary constituent of the Lightweight Space Shuttle External Tank. The process has been under development at MSFC for External Tank applications since the early 1990's. Early development of the FSW process proceeded by cut-and-try empirical methods. A substantial and complex body of data resulted. A theoretical model was wanted to deal with the complexity and reduce the data to concepts serviceable for process diagnostics, optimization, parameter selection, etc. A first step in understanding the FSW process is to determine the kinematics, i.e., the flow field in the metal in the vicinity of the pin-tool. Given the kinematics, the dynamics, i.e., the forces, can be targeted. Given a completed model of the FSW process, attempts at rational design of tools and selection of process parameters can be made.

  20. Meshless Simulation of Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Alfaro, I.; Fratini, L.; Cueto, E.; Chinesta, F.; Micari, F.

    2007-05-01

    This paper encompasses our first efforts towards the numerical simulation of friction stir welding by employing a Lagrangian approach. To this end, we have employed a meshless method, namely the Natural Element Method (NEM). Friction Stir welding is a welding process where the union between the work pieces is achieved through the extremely high deformation imposed by a rotating pin, which moves between the two pieces. This extremely high strain is the main responsible of the difficulties associated with the numerical simulation of this forming process. Eulerian and Arbitrary Lagrangian-Eulerian (ALE) frameworks encounter difficulties in some aspects of the simulation. For instance, these approaches need additional techniques for the description of the boundary between materials, such as level sets, boundary markers or similar. In this paper we address the issue of employing a Lagrangian framework, which adequately describes the evolution in time of the interphase. The meshless character of the technique also ensures that no degeneracy on the accuracy is obtained due to mesh distortion. Some examples are presented that show the potential of the technique in simulating such a process.

  1. Effect of friction stir welding parameters on defect formation

    NASA Astrophysics Data System (ADS)

    Tarasov, S. Yu.; Rubtsov, V. E.; Eliseev, A. A.; Kolubaev, E. A.; Filippov, A. V.; Ivanov, A. N.

    2015-10-01

    Friction stir welding is a perspective method for manufacturing automotive parts, aviation and space technology. One of the major problems is the formation of welding defects and weld around the welding zone. The formation of defect is the main reason failure of the joint. A possible way to obtain defect-free welded joints is the selection of the correct welding parameters. Experimental results describing the effect of friction stir welding process parameters on the defects of welded joints on aluminum alloy AMg5M have been shown. The weld joint defects have been characterized using the non-destructive radioscopic and ultrasound phase array methods. It was shown how the type and size of defects determine the welded joint strength.

  2. Friction Stir Weld Modeling at MSFC: Kinematics

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2000-01-01

    A "merry-go-round" computation model makes it easier to visualize how tracer experiments of varied sorts (chemical, shot, wire) are consistent with a "moving plug model" of flow around the friction stir welding pin-tool. The moving plug model comprises a twofold flow: 1. a primary rotation of a plug of metal with the tool, which moves metal around the tool by wiping it on and off the plug, and 2. a secondary, relatively slow circulation induced by the threads on the tool resembling a circular vortex ring around the tool.

  3. FRICTION-STIR-LAP-WELDS OF AA6111 ALUMINUM ALLOY

    SciTech Connect

    Yadava, Manasij; Mishra, Rajiv S.; Chen, Y. L.; Gayden, X.; Grant, Glenn J.

    2007-01-09

    Lap joints of 1 mm thick AA6111 aluminum sheets were made by friction stir welding, using robotic and conventional machines. Welds were made for advancing as well as retreating side loading. Thinning in welds was quantified. Lap shear test of welds was conducted in as-welded and paint-baked conditions. Conventional machine welds showed less thinning and better strength than robotic machine welds. Process forces in conventional machine welding were higher. Paint bake treatment improved the weld strength; but the improvement varied with process parameters. Advancing side loaded welds achieved higher strength than the retreating side loaded welds. Fracture location was found to occur on the loaded side of the weld and along the thinning defect.

  4. Spot-Welding Gun With Adjustable Pneumatic Spring

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1990-01-01

    Proposed spot-welding gun equipped with pneumatic spring, which could be bellows or piston and cylinder, exerts force independent of position along stroke. Applies accurate controlled force to joint welded, without precise positioning at critical position within stroke.

  5. Process Model for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Adams, Glynn

    1996-01-01

    Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the

  6. Metallography of Battery Resistance Spot Welds

    NASA Technical Reports Server (NTRS)

    Martinez, J. E.; Johannes, L. B.; Gonzalez, D.; Yayathi, S.; Figuered, J. M.; Darcy, E. C.; Bilc, Z. M.

    2015-01-01

    Li-ion cells provide an energy dense solution for systems that require rechargeable electrical power. However, these cells can undergo thermal runaway, the point at which the cell becomes thermally unstable and results in hot gas, flame, electrolyte leakage, and in some cases explosion. The heat and fire associated with this type of event is generally violent and can subsequently cause damage to the surrounding system or present a dangerous risk to the personnel nearby. The space flight environment is especially sensitive to risks particularly when it involves potential for fire within the habitable volume of the International Space Station (ISS). In larger battery packs such as Robonaut 2 (R2), numerous Li-ion cells are placed in parallel-series configurations to obtain the required stack voltage and desired run-time or to meet specific power requirements. This raises a second and less obvious concern for batteries that undergo certification for space flight use: the joining quality at the resistance spot weld of battery cells to component wires/leads and battery tabs, bus bars or other electronic components and assemblies. Resistance spot welds undergo materials evaluation, visual inspection, conductivity (resistivity) testing, destructive peel testing, and metallurgical examination in accordance with applicable NASA Process Specifications. Welded components are cross-sectioned to ensure they are free of cracks or voids open to any exterior surface. Pore and voids contained within the weld zone but not open to an exterior surface, and are not determined to have sharp notch like characteristics, shall be acceptable. Depending on requirements, some battery cells are constructed of aluminum canisters while others are constructed of steel. Process specific weld schedules must be developed and certified for each possible joining combination. The aluminum canisters' positive terminals were particularly difficult to weld due to a bi-metal strip that comes ultrasonically

  7. Seam-Tracking for Friction Stir Welded Lap Joints

    NASA Astrophysics Data System (ADS)

    Fleming, Paul A.; Hendricks, Christopher E.; Cook, George E.; Wilkes, D. M.; Strauss, Alvin M.; Lammlein, David H.

    2010-11-01

    This article presents a method for automatic seam-tracking in friction stir welding (FSW) of lap joints. In this method, tracking is accomplished by weaving the FSW tool back-and-forth perpendicular to the direction of travel during welding and monitoring force and torque signals. Research demonstrates the ability of this method to automatically track weld seam positions. Additionally, tensile and S-bend test result comparisons demonstrate that weaving most likely does not reduce weld quality. Finally, benefits of this weave-based method to FSW of lap joints are discussed and methods for incorporating it into existing friction stir welding control algorithms (such as axial load control) are examined.

  8. The Plunge Phase of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    McClure, John C.

    2005-01-01

    The many advantages of Friction Stir Welding have led to a relatively rapid acceptance in the often conservative welding community. Because the process is so different from traditional fusion welding, with which most investigators are most familiar, there remain many aspects of FSW for which there is no clear consensus. For example, the well known onion rings seen in transverse sections have been variously interpreted as grain size variations, variation in density of second phase particles and parts of the carousel of material rotating with the pin that have been shed from the carousel. Using Orientation Imaging Microscopy, Schneider has recently noted that the onion rings have a different orientation (and hence etch differently) than the surrounding material, and this orientation is consistent with slip plane orientations at the edge of the carousel. Likewise, the forces and torque exerted by the FSW tool on the work piece largely remain unaccounted for. Although these forces are routinely measured by investigators with commercial instrumented welders, they are rarely reported or even qualitatively analyzed. This paper will introduce a model based on a carousel or disk of material that rotates with the tool to estimate the torque and plunge force required to plunge a tool into the work piece. A stationary tool is modeled rather than the moving tool because effects such as thermal transients and metallurgical changes in the sample (primarily aging in aluminum) can be more easily accounted for. It is believed, however, that with some modifications the model should be applicable to a moving tool also.

  9. Metal Flow During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Guerra, M.; Schmidt, C.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in its wake, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  10. Material Flow During Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Guerra, M.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported in two distinct streams or currents. One stream is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug. After one or more rotations, this material is sloughed off the plug in the wake of the tool primarily on the advancing side. The second stream of material is an entrainment of material from the retreating side of the nib that fills in between the sloughed off pieces from the advancing side. These two processes produce material with different mechanical properties and the strength of a weld should depend on the relative importance of the processes.

  11. Metallurgical Evaluation of AZ31B-H24 Magnesium Alloy Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Pareek, M.; Polar, A.; Rumiche, F.; Indacochea, J. E.

    2007-10-01

    Friction Stir welding of 3.175 mm (0.125 in.) thick plates of AZ31-H24 magnesium alloy was performed using several travel velocities and tool-rotation speeds. After production the welds were cross-sectioned and a metallurgical characterization was performed using optical microscopy, and scanning electron microscopy. Assessment of the weld nugget or “stirred zone” shows evidence of dynamic recrystallization and the start of grain growth in some spots of this region compared to the parent metal. Recrystallization was identified in the thermomechanically affected zone (TAZ) as well. The mechanical properties of the weld are correlated with the corresponding microstructures present in the weld nugget and TMAZ. Corrosion resistance of the weld was assessed using Electrochemical Impedance Spectroscopy (EIS) techniques and immersion tests in a corrosive environment; it showed better corrosion resistance than the base metal.

  12. Ultrasonic assessment of tension shear strength in resistance spot welding

    NASA Astrophysics Data System (ADS)

    Moghanizadeh, Abbas

    2015-05-01

    Resistance spot welding is extensively used to join sheet steel in the automotive industry. Ultrasonic non-destructive techniques for evaluation of the mechanical properties of resistance spot welding are presented. The aim of this study is to develop the capability of the ultrasonic techniques as an efficient tool in the assessment of the welding characterization. Previous researches have indicated that the measurements of ultrasonic attenuation are sensitive to grain- size variations in an extensive range of metallic alloys. Other researchers have frequently described grain sizes which are able to have significant effects on the physical characteristics of the material. This research provides a novel method to estimate the tension-shear strengths of the resistance spot welding directly from the ultrasonic attenuation measurements. The effects of spot welding parameters on the ultrasonic waves are further investigated. The results confirm that it is possible to determine the spot welding parameters for individual quality by using ultrasonic test.

  13. Friction pull plug welding: top hat plug design

    NASA Technical Reports Server (NTRS)

    Coletta, Edmond R. (Inventor); Cantrell, Mark A. (Inventor)

    2001-01-01

    Friction Pull Plug Welding is a solid state repair process for defects up to one inch in length, only requiring single sided tooling, or outside skin line (OSL), for preferred usage on flight hardware. The most prevalent defect associated with Friction Pull Plug Welding (FPPW) was a top side or inside skin line (ISL) lack of bonding. Bonding was not achieved at this location due to the reduction in both frictional heat and welding pressure between the plug and plate at the end of the weld. Thus, in order to eliminate the weld defects and increase the plug strength at the plug `top` a small `hat` section is added to the pull plug for added frictional heating and pressure.

  14. Friction pull plug welding: top hat plug design

    NASA Technical Reports Server (NTRS)

    Coletta, Edmond R. (Inventor); Cantrell, Mark A. (Inventor)

    2002-01-01

    Friction Pull Plug Welding is a solid state repair process for defects up to one inch in length, only requiring single sided tooling, or outside skin line (OSL), for preferred usage on flight hardware. The most prevalent defect associated with Friction Pull Plug Welding (FPPW) was a top side or inside skin line (ISL) lack of bonding. Bonding was not achieved at this location due to the reduction in both frictional heat and welding pressure between the plug and plate at the end of the weld. Thus, in order to eliminate the weld defects and increase the plug strength at the plug `top` a small `hat` section is added to the pull plug for added frictional heating and pressure.

  15. Material Flow during Friction Stir Welding of HSLA 65 Steel

    NASA Astrophysics Data System (ADS)

    Young, John; Field, David; Nelson, Tracy

    2013-07-01

    Material flow during friction stir welding of HSLA-65 steel was investigated by crystallographic texture analysis. During the welding process, the steel deforms primarily by local shear deformation in the austenite phase and then transforms upon cooling. Texture data from three weld specimens were compared to theoretical textures calculated using ideal Euler angles for shear in face centered cubic (FCC) structures transformed by the Kurdjumov-Sacks (KS) relationship. These theoretical textures show similarities to the experimental textures. Texture data from the weld specimens revealed a rotation of the shear direction corresponding to the tangent of the weld tool on both the area directly under the weld tool shoulder and weld cross sections. In addition, texture data showed that while the shear plane of the area under the weld tool shoulder remained constant, the shear plane of the weld cross sections is influenced by the weld tool pin.

  16. Flow Trajectories in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Bernstein, Edward L.

    1999-01-01

    In the Friction Stir Welding (FSW) process, a rotating, shouldered tool with a threaded pin is inserted under pressure along the seam of two pieces of metal which are tightly clamped together, and secured against a rigid anvil underneath. The rotating pin travels along the seam and through a combination of pressure and friction heating produces a zone of plastic deformation around the pin within the workpiece on either side of the seam. As the pin is moved in the direction of welding, the plasticised material moves around the tool and bonds together behind it. The elements of the material flow behavior are a combination of three elements. There is a rotational transport of material being carried around the tool, extrusion of material being forced around the pin on both sides into the cavity created behind it, and a lifting and dropping of material as it is stirred and mixed by the rotating action of the pin. It was assumed that rotational motion of the plastic zone is the primary mechanism for transport of material around the welding tool. A kinematic mathematical model was used to compute trajectories of material movement for various distributions of rotational slip within the plastic zone. These trajectories were then compared with the results of an experiment that produced radiographs of markers embedded in a workpiece that was welded with the FSW process. It was assumed that the copper wire markers retained their original length as the aluminum material flowed around them. The kinematic model included a constraint so that the displacements were such that the total length of the wire markers did not increase after deformation. There was good agreement between the calculated trajectories for the case of localized slip at the outer surface of the plastic deformation zone and the radiographs of the copper wire markers. The trajectories differed markedly from the radiograph traces when a distributed slip zone was assumed. It was concluded that the flow field could

  17. Mechanism for Self-Reacted Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Venable, Richard; Bucher, Joseph

    2004-01-01

    A mechanism has been designed to apply the loads (the stirring and the resection forces and torques) in self-reacted friction stir welding. This mechanism differs somewhat from mechanisms used in conventional friction stir welding, as described below. The tooling needed to apply the large reaction loads in conventional friction stir welding can be complex. Self-reacted friction stir welding has become popular in the solid-state welding community as a means of reducing the complexity of tooling and to reduce costs. The main problems inherent in self-reacted friction stir welding originate in the high stresses encountered by the pin-and-shoulder assembly that produces the weld. The design of the present mechanism solves the problems. The mechanism includes a redesigned pin-and-shoulder assembly. The welding torque is transmitted into the welding pin by a square pin that fits into a square bushing with set-screws. The opposite or back shoulder is held in place by a Woodruff key and high-strength nut on a threaded shaft. The Woodruff key reacts the torque, while the nut reacts the tensile load on the shaft.

  18. Friction stir welding process to repair voids in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

    1999-01-01

    The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

  19. 2195 Aluminum-Copper-Lithium Friction Plug Welding Development

    NASA Technical Reports Server (NTRS)

    Takeshita, Rike P.; Hartley, Paula J.; Baker, Kent S.

    1997-01-01

    Technology developments and applications of friction plug welding is presented. This friction repair welding technology is being studied for implementation on the Space Transportation System's Super Light Weight External Tank. Single plug repairs will be used on a vast majority of weld defects, however, linear defects of up to several inches can be repaired by overlapping plug welds. Methods and results of tensile, bend, simulated service, surface crack tension and other tests at room and cryogenic temperatures is discussed. Attempts to implement Friction Plug Welding has led to both tool and process changes in an attempt to minimize expansive tooling and lengthy implementation times. Process control equipment and data storage methods intended for large scale production will also be addressed. Benefits include increased strength and toughness, decreased weld repair time, automated and highly reliable process, and a lower probability of having to re-repair defect locations.

  20. Low-temperature friction-stir welding of 2024 aluminum

    SciTech Connect

    Benavides, S.; Li, Y.; Murr, L.E.; Brown, D.; McClure, J.C.

    1999-09-10

    Solid-state, friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction (proportional to the product of strain and strain-rate) will all influence both the recrystallization and grain growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low-temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature ({approximately} 30 C) and low temperature ({minus} 30 C).

  1. Weld Spot Detection by Color Segmentation and Template Convolution

    SciTech Connect

    Cambrini, Luigi; Biber, Juergen; Hoenigmann, Dieter; Loehndorf, Maike

    2007-12-26

    There is a need of non-destructive evaluation of the quality of steel spot welds. A computer-vision based solution is presented performing the analysis of the weld spot imprints left by the electrode on the protection bands. In this paper we propose two different methods to locate the position of the weld spot imprint as a first step in order to verify the quality of the welding process; both methods consist of two stages: (i) the use of the X channel of the XYZ color space as a proper representation, and (ii) the analysis of this image channel by employing specific algorithms.

  2. Friction pull plug welding: dual chamfered plate hole

    NASA Technical Reports Server (NTRS)

    Coletta, Edmond R. (Inventor); Cantrell, Mark A. (Inventor)

    2001-01-01

    Friction Pull Plug Welding (FPPW) is a solid state repair process for defects up to one inch in length, only requiring single sided tooling (OSL) for usage on flight hardware. Early attempts with FPPW followed the matching plug/plate geometry precedence of the successful Friction Push Plug Welding program, however no defect free welds were achieved due to substantial plug necking and plug rotational stalling. The dual chamfered hole has eliminated plug rotational stalling, both upon initial plug/plate contact and during welding. Also, the necking of the heated plug metal under a tensile heating/forging load has been eliminated through the usage of the dual chamfered plate hole.

  3. REAL TIME ULTRASONIC ALUMINUM SPOT WELD MONITORING SYSTEM

    SciTech Connect

    Regalado, W. Perez; Chertov, A. M.; Maev, R. Gr.

    2010-02-22

    Aluminum alloys pose several properties that make them one of the most popular engineering materials: they have excellent corrosion resistance, and high weight-to-strength ratio. Resistance spot welding of aluminum alloys is widely used today but oxide film and aluminum thermal and electrical properties make spot welding a difficult task. Electrode degradation due to pitting, alloying and mushrooming decreases the weld quality and adjustment of parameters like current and force is required. To realize these adjustments and ensure weld quality, a tool to measure weld quality in real time is required. In this paper, a real time ultrasonic non-destructive evaluation system for aluminum spot welds is presented. The system is able to monitor nugget growth while the spot weld is being made. This is achieved by interpreting the echoes of an ultrasound transducer located in one of the welding electrodes. The transducer receives and transmits an ultrasound signal at different times during the welding cycle. Valuable information of the weld quality is embedded in this signal. The system is able to determine the weld nugget diameter by measuring the delays of the ultrasound signals received during the complete welding cycle. The article presents the system performance on aluminum alloy AA6022.

  4. Inspecting Friction Stir Welding using Electromagnetic Probes

    NASA Technical Reports Server (NTRS)

    Kinchen, David G.

    2004-01-01

    A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

  5. Fatigue Crack Growth in Peened Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; Hatamleh, Omar

    2008-01-01

    Friction stir welding induces residual stresses that accelerates fatigue crack growth in the weld nugget. Shot peening over the weld had little effect on growth rate. Laser peening over the weld retarded the growth rate: Final crack growth rate was comparable to the base, un-welded material. Crack tunneling evident from residual compressive stresses. 2195-T8 fracture surfaces were highly textured. Texturing makes comparisons difficult as the material system is affecting the data as much as the processing. Material usage becoming more common in space applications requiring additional work to develop useful datasets for damage tolerance analyses.

  6. Microstructural evolution of 6063 aluminum during friction-stir welding

    SciTech Connect

    Sato, Y.S.; Kokawa, Hiroyuki; Enomoto, Masatoshi; Jogan, Shigetoshi

    1999-09-01

    The microstructural distribution associated with a hardness profile in a friction-stir-welded, age-hardenable 6063 aluminum alloy has been characterized by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The friction-stir process produces a softened region in the 6063 Al weld. Frictional heating and plastic flow during friction-stir welding create fine recrystallized grains in the weld zone and recovered grains in the thermomechanically affected zone. The hardness profile depends greatly on the precipitate distribution and only slightly on the grain size. The softened region is characterized by dissolution and growth of the precipitates during the welding. Simulated weld thermal cycles with different peak temperatures have shown that the precipitates are dissolved at temperatures higher than 675 K and that the density of the strengthening precipitate was reduced by thermal cycles lower than 675 K. A comparison between the thermal cycles and isothermal aging has suggested precipitation sequences in the softened region during friction-stir welding.

  7. Surface roughness and friction coefficient in peened friction stir welded 2195 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Hatamleh, Omar; Smith, James; Cohen, Donald; Bradley, Robert

    2009-05-01

    The tribological properties of friction stir welded 2195 aluminum alloy joints were investigated for several laser- and shot-peened specimens. The first portion of this study assessed the surface roughness changes at different regions of the weld resulting from the various peening processes and included an atomic force microscopy (AFM) study to reveal fine structures. The second portion investigated the friction characteristics for various conditions when slid against a 440C ball slider. Shot peening resulted in significant surface roughness when compared to the unpeened and laser-peened samples. The initial friction for all types of specimens was highly variable. However, long-term friction was shown to be lowest for samples with no peening treatment. Laser peening caused the friction to increase slightly. The shot peening process on the other hand resulted in an increase of the long-term friction effects on both sides of the weld.

  8. Analysis and validation of laser spot weld-induced distortion

    SciTech Connect

    Knorovsky, G.A.; Kanouff, M.P.; Maccallum, D.O.; Fuerschbach, P.W.

    1999-12-09

    Laser spot welding is an ideal process for joining small parts with tight tolerances on weld size, location, and distortion, particularly those with near-by heat sensitive features. It is also key to understanding the overlapping laser spot seam welding process. Rather than attempting to simulate the laser beam-to-part coupling (particularly if a keyhole occurs), it was measured by calorimetry. This data was then used to calculate the thermal and structural response of a laser spot welded SS304 disk using the finite element method. Five combinations of process parameter values were studied. Calculations were compared to experimental data for temperature and distortion profiles measured by thermocouples and surface profiling. Results are discussed in terms of experimental and modeling factors. The authors then suggest appropriate parameters for laser spot welding.

  9. Friction-Stir Welding of Aluminum For the Space Program

    NASA Technical Reports Server (NTRS)

    Jones, Clyde S.; Smelser, Jerry W. (Technical Monitor)

    2002-01-01

    The Marshall Space Flight Center is developing and characterizing the friction stir welding process for the Space Shuttle and other space programs. This revolutionary process, invented and patented by The Weld Institute in England, offers tremendous advantages for joining aluminum for high performance applications. It is particularly suited for advanced aluminum-lithium alloys, such as 2195, the primary structural alloy used in the External Tank. The friction stir welding process joins metals with minimal heat input, resulting in high-strength joints with high ductility. It is a simple process to demonstrate using a common milling machine for sample parts, but relatively expensive to implement on large-scale hardware, due to the high cost of tooling needed to handle the high forging pressures characteristic of the process. Recent developments at the Marshall Space Flight Center have demonstrated friction stir welding on linear joints up to 5 meters (15 ft.), with material thickness ranging between 2.5 mm and 16.5 mm (0.100" to 0.650"). High efficiency weld joints have been produced in aluminum from the 2000, 5000, and 6000 series alloy systems. A "retractable pin tool" system was patented by MSFC that allows use of friction stir welding for joints with changing material thickness, and with less rigid tooling than previously considered. This presentation will describe the details of alloys welded to-date and technical advances under development at MSFC. These developments could have substantial benefit to industrial applications for welding aluminum.

  10. Defect Detectability Improvement for Conventional Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Hill, Chris

    2013-01-01

    This research was conducted to evaluate the effects of defect detectability via phased array ultrasound technology in conventional friction stir welds by comparing conventionally prepped post weld surfaces to a machined surface finish. A machined surface is hypothesized to improve defect detectability and increase material strength.

  11. Pulse shaping effects on weld porosity in laser beam spot welds : contrast of long- & short- pulse welds.

    SciTech Connect

    Ellison, Chad M.; Perricone, Matthew J.; Faraone, Kevin M.; Norris, Jerome T.

    2007-10-01

    Weld porosity is being investigated for long-pulse spot welds produced by high power continuous output lasers. Short-pulse spot welds (made with a pulsed laser system) are also being studied but to a much small extent. Given that weld area of a spot weld is commensurate with weld strength, the loss of weld area due to an undefined or unexpected pore results in undefined or unexpected loss in strength. For this reason, a better understanding of spot weld porosity is sought. Long-pulse spot welds are defined and limited by the slow shutter speed of most high output power continuous lasers. Continuous lasers typically ramp up to a simmer power before reaching the high power needed to produce the desired weld. A post-pulse ramp down time is usually present as well. The result is a pulse length tenths of a second long as oppose to the typical millisecond regime of the short-pulse pulsed laser. This study will employ a Lumonics JK802 Nd:YAG laser with Super Modulation pulse shaping capability and a Lasag SLS C16 40 W pulsed Nd:YAG laser. Pulse shaping will include square wave modulation of various peak powers for long-pulse welds and square (or top hat) and constant ramp down pulses for short-pulse welds. Characterization of weld porosity will be performed for both pulse welding methods.

  12. Friction Stir Welding of Lightweight Vehicle Structures: Final Report

    SciTech Connect

    Sanella, M L

    2008-08-31

    The purpose of this Cooperative Research and Development Agreement (CRADA) between UTBattelle, LLC and Ford Motor Company was to establish friction stir welding (FSW) and friction stir processing as viable options for use in construction of lightweight substructures for trucks and cars, including engine cradles, suspension sub frames, instrument panel supports, and intake manifolds.

  13. Retractable Pin Tools for the Friction Stir Welding Process

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Two companies have successfully commercialized a specialized welding tool developed at the Marshall Space Flight Center (MSFC). Friction stir welding uses the high rotational speed of a tool and the resulting frictional heat created from contact to crush, 'stir' together, and forge a bond between two metal alloys. It has had a major drawback, reliance on a single-piece pin tool. The pin is slowly plunged into the joint between two materials to be welded and rotated as high speed. At the end of the weld, the single-piece pin tool is retracted and leaves a 'keyhole,' something which is unacceptable when welding cylindrical objects such as drums, pipes and storage tanks. Another drawback is the requirement for different-length pin tools when welding materials of varying thickness. An engineer at the MSFC helped design an automatic retractable pin tool that uses a computer-controlled motor to automatically retract the pin into the shoulder of the tool at the end of the weld, preventing keyholes. This design allows the pin angle and length to be adjusted for changes in material thickness and results in a smooth hole closure at the end of the weld. Benefits of friction stir welding, using the MSFC retractable pin tool technology, include the following: The ability to weld a wide range of alloys, including previously unweldable and composite materials; provision of twice the fatigue resistance of fusion welds and no keyholes; minimization of material distortion; no creation of hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing; automatic retraction of the pin at the end of the weld; and maintaining full penetration of the pin.

  14. Langangian Particle Model of Friction Stir Welding

    SciTech Connect

    Tartakovsky, Alexandre M.

    2006-12-13

    Since its invention fifteen years ago, Friction Stir Welding (FSW) has found commercial application in the marine, aerospace, rail, and now automotive industries. Development of the FSW process for each new application, however, has remained largely empirical. Few detailed numerical modeling techniques have been developed that can explain and predict important features of the process physics. This is particularly true in the areas of material flow, mixing mechanisms, and void prediction. In this paper we present a novel modeling approach to simulate FSW processes that may have significant advantages over current traditional finite element or finite difference based methods. The proposed model is based on the Smoothed Particle Hydrodynamics (SPH) method. Unlike traditional grid-based methods, Lagrangian particle methods such as SPH can simulate the dynamics of interfaces, large material deformations, void formations and the material's strain and temperature history without employing complex tracking schemes. Two- and three-dimensional FSW simulations for different tool designs are presented. Preliminary numerical results are in qualitative agreement with experimental observations. Detailed comparisons between experimental measurements and larger scale FSW simulations are required to further validate and calibrate the SPH based FSW model.

  15. Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

    NASA Technical Reports Server (NTRS)

    Petter, George E.; Figert, John D.; Rybicki, Daniel J.; Burns, Timothy

    2006-01-01

    A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility. This method of heat treatment is a superior alternative to a specification-required heat treatment that caused the formation of large columnar grains, which are undesired. Workpieces subjected to the prior heat treatment exhibited elongations <2 percent, and standard three-point bend specimens shattered. The development of the present heat treatment method was guided partly by the principles that (1) by minimizing grain sizes and relieving deformation stresses, one can minimize or eliminate stress corrosion cracking and (2) the key to maximizing strength and eliminating residual stresses is to perform post-weld solution heating for as long a time as possible while incurring little or no development of large columnar grains in friction stir weld nuggets. It is necessary to perform some of the solution heat treatment (to soften the alloy and improve machine welding parameters) before welding. The following is an example of thickness- dependent pre- and post-weld heat treatments according to the present method: For plates 0.270 in. (approx.6.86 mm) thick milled from plates 4.5 in. (114.3 mm) thick, perform pre-weld solution heating at 890 F (477 C) for 1 hour, then cool in air. After friction stir welding, perform solution heating for 10 minutes, quench, hold at room temperature for 96 hours, then age at 250 F (121 C) for 5 hours followed by 325 F (163 C) for 27 hours.

  16. SLI Complex Curvature Friction Stir Weld Risk Reduction Program

    NASA Technical Reports Server (NTRS)

    Hartley, Paula J.; Schneider, Jules; Jones, Chip; Lawless, Kirby; Russell, Carolyn

    2003-01-01

    The Space Launch Initiative Program (SLI) in conjunction with the National Center for Advanced Manufacturing (NCAM) will demonstrate the ability to produce large-scale complex curvature hardware using the self-reacting friction stir welding process. This multi-phased risk reduction program includes friction stir welding process development and manufacture of a 22-ft diameter quarter dome using a conventional tooling approach; it culminates in a 27.5-ft diameter quarter dome demonstration performed on a 5-axis Universal Weld System. The design, fabrication, and installation of the Universal Weld System is made possible through a collaboration between the State of Louisiana, NASA, and the University of New Orleans. The Universal Weld System, manufactured by MTS Systems Corporation, will be installed at the Michoud Assembly Facility in New Orleans, Louisiana, and will be capable of manufacturing domes up to 30 ft in diameter. All welding will be accomplished using the Adaptable Adjustable Pin Tool (AdAPT) weld head and controller manufactured by MTS. Weld parameters will be developed for an aluminum alloy in gauges ranging from 0.320 to 0.400 in. thick. Weld quality will be verified through radiography, mechanical property testing at ambient and LN2 temperatures, and metallurgical analysis. The AdAPT weld head will then be mounted on a 22-ft diameter dome tool, which will be modified to include a welding track and drive system for moving the AdAPT weld head along the weld joint. This tool will then be used to manufacture a 22-ft diameter dome of an aluminum alloy, with 0.320-in. constant thickness joints, consisting of three individual gore panels. Finally, the 27.5-ft diameter quarter dome will be welded on the Universal Weld System. The quarter dome will consist of three individual gore panels with weld lands tapering from 0.320 to 0.360 in. in thickness. With the demonstration of these welds, the ability to manufacture large diameter domes using the friction stir

  17. Tracing Material Flow Paths in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Sanders, Johnny; Schneider, Judy; Numes, Arthur, Jr.

    2005-01-01

    Heat and mechanical work are coupled in the friction stir welding process. The process variables are RPM, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the process variables plus the individual flow path taken by the particular filament of metal flowing around the tool and ending on flat point. The strain-temperature history determines the properties of a metal element on the weld cross-section. The strain-temperature history is carefully controlled in metal processes where direct control is feasible. Indirect estimates of the flow paths and the strain-temperature histories of filaments comprising friction stir welds can be made from a model, if the model is good enough. This paper describes marker studies of flow path geometries for various process parameters. Observed geometries are compared with geometries estimated from models.

  18. The Formability of Friction Stir Welds in Automotive Stamping Environments

    SciTech Connect

    Grant, Glenn J.; Davies, Richard W.; Stephens, Elizabeth V.; Wazny, Scott; Kaunitz, Leon; Waldron, Douglas J.

    2006-02-01

    Automobile body and truck cab structures are composed primarily of stampings formed from monolithic and constant gage blanks. Cost and weight penalties can arise when strength or other requirements in one small area of the part leads to the use of a material or gage that is overmatched to the needs of the rest of the stamping. Tailor Welded Blanks (TWBs) are hybrid sheet products composed of either different materials or different thickness sheets that are joined together, then subjected to a stamping operation to create a formed assembly. The strategy is employed generally to save weight and material costs in the formed assembly by placing higher strength or thicker sections only where needed. The forming or stamping process requires the joint to be severely deformed along with the parent sheets. Aluminum TWBs for automotive applications are particularly problematic because of the low formability of aluminum weld metal. Friction Stir Welding (FSW) is a process recently applied to Aluminum TWBs that has the potential to produce a higher quality weld. The current study presents data on the mechanical properties, formability, and FSW weld process parameter development for friction stir welded aluminum, Tailor Welded Blanks. Friction stir welded TWBs can be shown to have higher formability, higher ductility, and lower defect content than many competing joining processes, and they can be fabricated at speeds appropriate for automotive manufacturing.

  19. Thermo-Mechanical Processing in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, Judy

    2003-01-01

    Friction stir welding is a solid-phase joining, or welding process that was invented in 1991 at The Welding Institute (TWI). The process is potentially capable of joining a wide variety of aluminum alloys that are traditionally difficult to fusion weld. The friction stir welding (FSW) process produces welds by moving a non-consumable rotating pin tool along a seam between work pieces that are firmly clamped to an anvil. At the start of the process, the rotating pin is plunged into the material to a pre-determined load. The required heat is produced by a combination of frictional and deformation heating. The shape of the tool shoulder and supporting anvil promotes a high hydrostatic pressure along the joint line as the tool shears and literally stirs the metal together. To produce a defect free weld, process variables (RPM, transverse speed, and downward force) and tool pin design must be chosen carefully. An accurate model of the material flow during the process is necessary to guide process variable selection. At MSFC a plastic slip line model of the process has been synthesized based on macroscopic images of the resulting weld material. Although this model appears to have captured the main features of the process, material specific interactions are not understood. The objective of the present research was to develop a basic understanding of the evolution of the microstructure to be able to relate it to the deformation process variables of strain, strain rate, and temperature.

  20. Friction Stir Welding Development at NASA, Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    McGill, Preston; Gentz, Steve (Technical Monitor)

    2001-01-01

    Friction stir welding (FSW) is a solid state process that pan be used to join materials without melting. The process was invented by The Welding Institute (TWI), Cambridge, England. Friction stir welding exhibits several advantages over fusion welding in that it produces welds with fewer defects and higher joint efficiency and is capable of joining alloys that are generally considered non-weldable with a fusion weld process. In 1994, NASA-Marshall began collaborating with TWI to transform FSW from a laboratory curiosity to a viable metal joining process suitable for manufacturing hardware. While teamed with TWI, NASA-Marshall began its own FSW research and development effort to investigate possible aerospace applications for the FSW process. The work involved nearly all aspects of FSW development, including process modeling, scale-up issues, applications to advanced materials and development of tooling to use FSW on components of the Space Shuttle with particular emphasis on aluminum tanks. The friction stir welding process involves spinning a pin-tool at an appropriate speed, plunging it into the base metal pieces to be joined, and then translating it along the joint of the work pieces. In aluminum alloys the rotating speed typically ranges from 200 to 400 revolutions per minute and the translation speed is approximately two to five inches per minute. The pin-tool is inserted at a small lead angle from the axis normal to the work piece and requires significant loading along the axis of the tool. An anvil or reaction structure is required behind the welded material to react the load along the axis of the pin tool. The process requires no external heat input, filler material, protective shielding gas or inert atmosphere typical of fusion weld processes. The FSW solid-state weld process has resulted in aluminum welds with significantly higher strengths, higher joint efficiencies and fewer defects than fusion welds used to join similar alloys.

  1. Unraveling the Processing Parameters in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C., Jr.

    2005-01-01

    In friction stir welding (FSW), a rotating threaded pin tool is translated along a weld seam, literally stirring the edges of the seam together. To determine optimal processing parameters for producing a defect free weld, a better understanding of the resulting metal deformation flow path or paths is required. In this study, various markers are used to trace the flow paths of the metal. X-ray radiographs record the segmentation and position of the wire. Several variations in the trajectories can be differentiated within the weld zone.

  2. Friction Stir Weld Restart+Reweld Repair Allowables

    NASA Technical Reports Server (NTRS)

    Clifton, Andrew

    2008-01-01

    A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data for initial FSW, confirming no change to the critical flaw size or inspection requirements for the repaired weld. Testing of VPPA fusion/FSW intersection weld specimens exhibited acceptable strength and exceeded the minimum design value. Porosity, when present at the intersection was on the root side toe of the fusion weld, the "worst case" being 0.7 inch long. While such porosity may be removed by sanding, this "worst case" porosity condition was tested "as is" and demonstrated that porosity did not negatively affect the strength of the intersection weld. Large, 15-inch "wide panels" FSW repair welds were tested to demonstrate strength and evaluate residual stresses using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no significant stress gradients due to the presence of the restart and multi-pass FSW repair weld.

  3. Heat Control via Torque Control in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Venable, Richard; Colligan, Kevin; Knapp, Alan

    2004-01-01

    In a proposed advance in friction stir welding, the torque exerted on the workpiece by the friction stir pin would be measured and controlled in an effort to measure and control the total heat input to the workpiece. The total heat input to the workpiece is an important parameter of any welding process (fusion or friction stir welding). In fusion welding, measurement and control of heat input is a difficult problem. However, in friction stir welding, the basic principle of operation affords the potential of a straightforward solution: Neglecting thermal losses through the pin and the spindle that supports it, the rate of heat input to the workpiece is the product of the torque and the speed of rotation of the friction stir weld pin and, hence, of the spindle. Therefore, if one acquires and suitably processes data on torque and rotation and controls the torque, the rotation, or both, one should be able to control the heat input into the workpiece. In conventional practice in friction stir welding, one uses feedback control of the spindle motor to maintain a constant speed of rotation. According to the proposal, one would not maintain a constant speed of rotation: Instead, one would use feedback control to maintain a constant torque and would measure the speed of rotation while allowing it to vary. The torque exerted on the workpiece would be estimated as the product of (1) the torque-multiplication ratio of the spindle belt and/or gear drive, (2) the force measured by a load cell mechanically coupled to the spindle motor, and (3) the moment arm of the load cell. Hence, the output of the load cell would be used as a feedback signal for controlling the torque (see figure).

  4. Recent developments in Micro Friction Stir Welding: A review

    NASA Astrophysics Data System (ADS)

    Sithole, Keydon; Vasudeva Rao, Veeredhi

    2016-02-01

    The advent of friction stir welding (FSW) in 1991 has been evolutionary in the joining of metals and related materials. Friction stir welding has enabled the joining of metals that could not be joined by other welding processes. Research has shown that dissimilar materials with very different properties, plastics, composites and even wood can be joined by FSW. Recent activities in the application of FSW has seen the development of micro friction stir welding (μFSW), which is the FSW of very thin sections of thickness 1000 μm (1 mm) or less. Micro friction stir welding further extends the applications of FSW to areas such as copper electrical contacts, tailor-welded blanks, wood. Though μFSW is relatively new development significant work has been done to date with interesting research findings being reported. This paper aims to review developments in μFSW to date. The focus of the paper will be on problems peculiar to μFSW due to downscaling to the micro scale and other practical considerations.

  5. Analysis of integrity and microstructure of linear friction welded Waspaloy

    SciTech Connect

    Chamanfar, A.; Jahazi, M.; Gholipour, J.; Wanjara, P.; Yue, S.

    2015-06-15

    Nickel-base superalloy, Waspaloy, was linear friction welded (LFWed) under different axial shortening conditions of 2.0, 3.4, and 4.6 mm. The tensile properties and microhardness of the weldments were investigated in the as-LFWed condition and compared with those in the post-weld heat treated (PWHTed) condition. Mechanical properties were related to microstructures following examination by optical microscopy, high resolution scanning electron microscopy, and electron backscatter diffraction (EBSD). Analyses of the EBSD results in terms of the misorientation angle distribution, which represents the stored energy, were performed. In the as-LFWed condition, the yield strength (YS) and ultimate tensile strength (UTS) increased with axial shortening due to greater expulsion of the softened interfacial material toward the periphery as flash. In contrast, with increasing axial shortening the total elongation initially remained constant and then decreased. This was also related to the expulsion of the softened interfacial material into the bifurcated flash. Extensive dissolution of the strengthening phase (γ′) in the weld area during linear friction welding (LFW) contributed to the lower YS and UTS in the as-welded condition compared to the PWHTed condition where the γ′ particles were recovered. After performing post-weld heat treatment (PWHT), the total elongation improved due to the relaxation of stored energy and grain growth in the thermomechanically affected zone (TMAZ). - Highlights: • Tensile property and microstructure in Waspaloy linear friction welds were studied. • Yield strength and ultimate tensile strength increased with axial shortening. • Elongation initially remained constant and then decreased with axial shortening. • Post-weld heat treat recovered dissolved γ′ particles and increased weld strength. • Stored energy relaxation during post-weld heat treatment improved weld elongation.

  6. The Formability of Friction Stir Welds in Automotive Stamping Environments

    SciTech Connect

    Grant, Glenn J.; Davies, Richard W.; Stephens, Elizabeth V.; wazny, scott; Kaunitz, Leon; Waldron, D.

    2005-04-01

    Automobile body and truck cab structures are composed primarily of stampings formed from monolithic and constant gage blanks. Cost and weight penalties can arrise when strength or other requirements in one small area of the part leads to the use of a material or gage that is overmatched to the needs of the rest of the stamping. Tailor Welded Blanks (TWBs) are hybrid sheet products composed of either different materials or different thickness sheets that are joined together, then subjected to a stamping operation to create a formed assembly. The strategy is employed generally to save weight and material costs in the formed assembly by placing higher strength or thicker sections only where needed. The forming or stamping process requires the joint to be severely deformed along with the parent sheets. Aluminum TWBs for automotive applications are particularly problematic because of the low formability of aluminum weld metal. Friction Stir Welding (FSW) is a process recently applied to Aluminum TWBs that has the potential to produce a higher quality weld. The current study presents data on the mechanical properties, formability, and FSW weld process parameter development for friction stir woined, aluminum, Tailor Welded Blanks. Friction stir welded TWBs can be shown to have higher formability, higher ductility, and lower defect content than many competing joining processes, and they can be fabricated at speeds appropriate for automotive manufacturing.

  7. Dissimilar friction welding of titanium alloys to alloy 718

    SciTech Connect

    Kuo, M.; Albright, C.E.; Baeslack, W.A. III

    1994-12-31

    The design of advanced, high-performance gas-turbine engines will require the utilization of elevated-temperature titanium-based materials, including conventional alloys, titanium aluminides, and titanium metal-matrix composites. The most efficient utilization of these materials in the engine compressor section would be achieved by directly joining these materials to existing nickel-base superalloys, such as Alloy 718. To date, the dissimilar welding of titanium alloys to nickel-based alloys has not been common practice because intermetallic compounds form in the weld and cause embrittlement. Special welding techniques must be developed to inhibit this compound formation and to provide high strength welds. In this investigation, a friction welding process was developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to nickel-based superalloy Alloy 718. An interlayer system comprised of copper and niobium sheet layers was employed as a diffusion barrier and weld deformation enhancer. A postweld heat treatment (PWHT, 700{degrees}C for 20 min in vacuum) under axial pressure (Ksi) was used to improve the joint strength consistency. The following conclusions can be drawn from this investigation: (1) A friction welding technique has been developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to Alloy 718 using an interlayer system of niobium and copper. Joint strengths averaging approximately 50 Ksi were achieved. (2) Deformation was concentrated in the interlayers, especially the copper interlayer, during friction welding. Increased reduction in length (RIL) during friction welding resulted in a decrease in the interlayer thicknesses. (3) The EDS results showed that the niobium and copper interlayers prevent interdiffusion between the two parent metals, producing formation of detrimental phases.

  8. Enabling high speed friction stir welding of aluminum tailor welded blanks

    NASA Astrophysics Data System (ADS)

    Hovanski, Yuri

    Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding (FSW) has traditionally been applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translate to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum FSW components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability using a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.

  9. Investigation of the Microstructure of Joints of Aluminum Alloys Produced by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Kolubaev, E. A.

    2015-02-01

    Special features of the microstructure of joints of aluminum-magnesium and aluminum-copper alloys produced by friction stir welding are analyzed. It is demonstrated that a layered structure with ultradisperse grains is produced by friction stir welding at the center of the weld joint. An analogy is drawn between the microstructures of joints produced by friction stir welding and surface layer produced by sliding friction.

  10. Effect of Weld Tool Geometry on Friction Stir Welded AA2219-T87 Properties

    NASA Technical Reports Server (NTRS)

    Querin, Joseph A.; Schneider, Judy A.

    2008-01-01

    In this study, flat panels of AA2219-T87 were friction stir welded (FSWed) using weld tools with tapered pins The three pin geometries of the weld tools included: 0 (straight cylinder), 30 , and 60 angles on the frustum. For each weld tool geometry, the FSW process parameters were optimized to eliminate defects. A constant heat input was maintained while varying the process parameters of spindle rpm and travel speed. This provided a constant heat input for each FSW weld panel while altering the hot working conditions imparted to the workpiece. The resulting mechanical properties were evaluated from tensile test results of the FSW joint.

  11. Study of mechanical joint strength of aluminum alloy 7075-T6 and dual phase steel 980 welded by friction bit joining and weld-bonding under corrosion medium

    SciTech Connect

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; Miles, Michael; Song, Guang-Ling; Wang, Yanli; Feng, Zhili

    2014-12-30

    We have employed a unique solid-sate joining process, called friction bit joining (FBJ), to spot weld aluminum alloy (AA) 7075-T6 and dual phase (DP) 980 steel. Static joint strength was studied in the lap shear tension configuration. In addition, weld-bonding (adhesive + FBJ) joints were studied in order to evaluate the ability of adhesive to mitigate the impact of corrosion on joint properties. Accelerated laboratory cyclic corrosion tests were carried out for both FBJ only and weld-bonding joints. Furthermore, the FBJ only joints that emerged from corrosion testing had lap shear failure loads that were significantly lower than freshly prepared joints. However, weld-bonding specimens retained more than 80% of the lap shear failure load of the freshly prepared weld-bonding specimens. Moreover, examination of joint cross sections confirmed that the presence of adhesive in the weld-bonding joints mitigated the effect of the corrosion environment, compared to FBJ only joints.

  12. Microstructural issues in a friction-stir-welded aluminum alloy

    SciTech Connect

    Flores, O.V.; Kennedy, C.; Murr, L.E.; Brown, D.; Pappu, S.; Nowak, B.M.; McClure, J.C.

    1998-02-03

    Recent observations of microstructures associated with friction-stir welding (FSW) in a number of aluminum alloys have consistently demonstrated the actual weld zone to consist of a (dynamically) recrystallized grain structure resulting from the extreme, solid-state, plastic deformation characterizing the process. Because of solubilities associated with the various precipitates in 7075 and 6061 aluminum alloys, and the fact that the precipitates were either homogeneously distributed throughout both the original (unwelded) work-piece plates and the well zones (or formed varying densities of Widmanstaetten patterns within the original and recrystallized grains), it has been difficult to follow the stirring of stable, second-phase particles from the base metal (work-piece) into the weld zone. In the present investigation, a compositionally modified 1100 aluminum alloy (nominally 99.2% Al, 0.5% Fe, 0.15% Cu, 0.12% Si, 0.05 Mn, 0.04 Ti, balance in weight percent of Be and Mg), forming a stable microdendritic (second-phase), equiaxed, cell structure was friction-stir welded. These thermally stable, geometrically specific, precipitates in the base metal were compared with their disposition within the friction-stir-weld zone. In addition, as-cast plates of this alloy were cold-rolled 50% and friction-stir-welded in order to compare these two schedules (as-cast and 50% cold-rolled) in terms of residual hardness variations and related microstructural issues as well as the effect of prior deformation on the friction-stir welding process.

  13. Texture and grain evolutions in a 2195 friction stire weld

    SciTech Connect

    Fonda, R. W.; Bingert, J. F.; Colligan, K. J.

    2004-01-01

    Variations in microstructure, crystallographic texture, and grain distributions were determined in a conventional transverse cross section of the deposited weld and in a planview cross section around the embedded welding tool in an Al 2195 friction stir weld that had been prepared to preserve a static representation of the dynamic deformation field surrounding the tool. These results reveal important new details about the development of grain structure and crystallographic texture around the FSW tool that cannot be determined from observations on the transverse cross section alone. Two orthogonal views of a friction stir weld were analyzed to determine the microstructure, crystallographic texture, and grain structure of the deposited weld and how these characteristics initially developed in the vicinity of the weld tool. The transverse cross section reveals many interesting features. There is a complex precipitation sequence across the different weld regions. The strengthening precipitates from the matrix become coarsened across the HAZ, then are gradually replaced by a separate precipitate distribution, which forms during cooling of the weld, in the TMAZ. A third precipitate distribution that includes the equilibrium T{sub B} phase is observed in the weld nugget and is responsible for the lower microhardness of that region. A coarsening of grains is observed in the TMAZ adjacent to the weld nugget, accompanied by an in-plane rotation of the grains towards <110>{parallel} welding direction. The latter observation suggests that this texture evolution is primarily in response to a simple-shear deformation field surrounding the tool. A plan-view section through the embedded FSW tool of this stop-action weld was prepared to reveal the initial development and evolution of the grain structure and crystallographic texture during friction stir welding. This analysis revealed bands of refined grains developing ahead of the fully refined region, likely reflecting different

  14. Thermo-Mechanical Processing in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, J. A.; Nunes, A. C., Jr.

    2002-01-01

    In Friction Stir Welding (FSW) a rotating pin-tool inserted into a weld seam literally stirs the edges of the seam together. In this study, two flow paths are proposed that define the FWS zone. Studies using a longitudinal tungsten wire (0.0025 dia.) were used to visualize and document the material flow. The material flow path is described using a mathematical model.

  15. Temporarily alloying titanium to facilitate friction stir welding

    SciTech Connect

    Hovanski, Yuri

    2009-05-01

    While historically hydrogen has been considered an impurity in titanium, when used as a temporary alloying agent it promotes beneficial changes to material properties that increase the hot-workability of the metal. This technique known as thermohydrogen processing was used to temporarily alloy hydrogen with commercially pure titanium sheet as a means of facilitating the friction stir welding process. Specific alloying parameters were developed to increase the overall hydrogen content of the titanium sheet ranging from commercially pure to 30 atomic percent. Each sheet was evaluated to determine the effect of the hydrogen content on process loads and tool deformation during the plunge phase of the friction stir welding process. Two materials, H-13 tool steel and pure tungsten, were used to fabricate friction stir welding tools that were plunged into each of the thermohydrogen processed titanium sheets. Tool wear was characterized and variations in machine loads were quantified for each tool material and weld metal combination. Thermohydrogen processing was shown to beneficially lower plunge forces and stabilize machine torques at specific hydrogen concentrations. The resulting effects of hydrogen addition to titanium metal undergoing the friction stir welding process are compared with modifications in titanium properties documented in modern literature. Such comparative analysis is used to explain the variance in resulting process loads as a function of the initial hydrogen concentration of the titanium.

  16. Heat Treatment of Friction Stir Welded 7X50 Aluminum

    NASA Technical Reports Server (NTRS)

    Petter, George E. (Inventor); Figert, John D. (Inventor); Rybicki, Daniel J. (Inventor); Burnes, Timothy H. (Inventor)

    2004-01-01

    A method for treating alloy before and after friction stir welding, the method comprising the following steps. First solution heat treating a multiplicity of aluminum-zinc alloy engineered components for a first time period at a first temperature. First air cooling the components in ambient air at room temperatwe until the components are cooled to room temperature. Friction stir welding the components to form an assembly. Second solution heat treating the assembly for a second time period at a second temperature. Additional steps and embodiments are considered.

  17. Near Net Manufacturing Using Thin Gage Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Takeshita, Jennifer; Potter, David; Holquin, Michael

    2006-01-01

    Friction Stir Welding (FSW) and near net spin forming of FSW aluminumn blanks were investigated for large-scale pressure vessel applications. With a specific focus on very thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability, reliability and performance of pressure vessels larger than 10 ft. diameter.

  18. Friction stir weld tools having fine grain structure

    DOEpatents

    Grant, Glenn J.; Frye, John G.; Kim, Jin Yong; Lavender, Curt A.; Weil, Kenneth Scott

    2016-03-15

    Tools for friction stir welding can be made with fewer process steps, lower cost techniques, and/or lower cost ingredients than other state-of-the-art processes by utilizing improved compositions and processes of fabrication. Furthermore, the tools resulting from the improved compositions and processes of fabrication can exhibit better distribution and homogeneity of chemical constituents, greater strength, and/or increased durability. In one example, a friction stir weld tool includes tungsten and rhenium and is characterized by carbide and oxide dispersoids, by carbide particulates, and by grains that comprise a solid solution of the tungsten and rhenium. The grains do not exceed 10 micrometers in diameter.

  19. Tensile and Impact Toughness Properties of Gas Tungsten Arc Welded and Friction Stir Welded Interstitial Free Steel Joints

    NASA Astrophysics Data System (ADS)

    Lakshminarayanan, A. K.; Balasubramanian, V.

    2011-02-01

    Welded regions of interstitial free (IF) steel grades in the vicinity of weld center exhibits larger grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties. In the present study, tensile properties, charpy impact toughness, microhardness, microstructure, lowest hardness distribution profile, and fracture surface morphology of the gas tungsten arc welded (GTAW) and friction stir welded joints were evaluated, and the results are compared. From this investigation, it is found that friction stir welded joint of IF steel showed superior tensile and impact properties compared with GTAW joint, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.

  20. Investigation of Torsional Strength of the VT6 Weld Joint Produced by Linear Friction Welding

    NASA Astrophysics Data System (ADS)

    Suleimanova, G. R.; Kabirov, R. R.; Karavaeva, M. V.; Ershova, Yu. A.; Zhilyaev, A. P.

    2015-10-01

    Results of measurement of torsional strength of the weld joint of the VT6 titanium alloy produced by linear friction welding are presented. For a comparison, the same method was used to test monolithic specimens of the VT6 alloy. Torsional strength values of the weld joint (τUS = 861 MPa and φ = 110°) correspond to the strength of the monolithic material. In this case, the specimens fail along the base metal.

  1. A theoretical study of the influence of technological friction stir welding parameters on weld structures

    NASA Astrophysics Data System (ADS)

    Astafurov, Sergey; Shilko, Evgeny; Kolubaev, Evgeny; Psakhie, Sergey

    2015-10-01

    Computer simulation by the movable cellular automaton method was performed to study the dynamics of friction stir welding of duralumin plates. It was shown that the ratio of the rotation rate to the translational velocity of the rotating tool has a great influence on the quality of the welded joint. A suitably chosen ratio of these parameters combined with an additional ultrasonic impact reduces considerably the porosity and the amount of microcracks in the weld.

  2. Friction Stir Welding of Tapered Thickness Welds Using an Adjustable Pin Tool

    NASA Technical Reports Server (NTRS)

    Adams, Glynn; Venable, Richard; Lawless, Kirby

    2003-01-01

    Friction stir welding (FSW) can be used for joining weld lands that vary in thickness along the length of the weld. An adjustable pin tool mechanism can be used to accomplish this in a single-pass, full-penetration weld by providing for precise changes in the pin length relative to the shoulder face during the weld process. The difficulty with this approach is in accurately adjusting the pin length to provide a consistent penetration ligament throughout the weld. The weld technique, control system, and instrumentation must account for mechanical and thermal compliances of the tooling system to conduct tapered welds successfully. In this study, a combination of static and in-situ measurements, as well as active control, is used to locate the pin accurately and maintain the desired penetration ligament. Frictional forces at the pin/shoulder interface were a source of error that affected accurate pin position. A traditional FSW pin tool design that requires a lead angle was used to join butt weld configurations that included both constant thickness and tapered sections. The pitch axis of the tooling was fixed throughout the weld; therefore, the effective lead angle in the tapered sections was restricted to within the tolerances allowed by the pin tool design. The sensitivity of the FSW process to factors such as thickness offset, joint gap, centerline offset, and taper transition offset were also studied. The joint gap and the thickness offset demonstrated the most adverse affects on the weld quality. Two separate tooling configurations were used to conduct tapered thickness welds successfully. The weld configurations included sections in which the thickness decreased along the weld, as well as sections in which the thickness increased along the weld. The data presented here include weld metallography, strength data, and process load data.

  3. High-Speed Friction-Stir Welding To Enable Aluminum Tailor-Welded Blanks

    SciTech Connect

    Hovanski, Yuri; Upadhyay, Piyush; Carsley, John; Luzanski, Tom; Carlson, Blair; Eisenmenger, Mark; Soulami, Ayoub; Marshall, Dustin; Landino, Brandon; Hartfield-Wunsch, Susan

    2015-05-01

    Current joining technologies for automotive aluminum alloys are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding has been traditionally applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translate to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum welded components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability utilizing a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.

  4. Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

    NASA Astrophysics Data System (ADS)

    Patterson, Erin E.; Hovanski, Yuri; Field, David P.

    2016-03-01

    This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld

  5. Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

    NASA Astrophysics Data System (ADS)

    Patterson, Erin E.; Hovanski, Yuri; Field, David P.

    2016-06-01

    This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld

  6. A model of material flow during friction stir welding

    SciTech Connect

    Hamilton, Carter Dymek, Stanislaw; Blicharski, Marek

    2008-09-15

    Tin plated 6061-T6 aluminum extrusions were friction stir welded in a 90 deg. butt-weld configuration. A banded microstructure of interleaved layers of particle-rich and particle-poor material comprised the weld nugget. Scanning and transmission electron microscopy revealed the strong presence of tin within the particle-rich bands, but TEM foils taken from the TMAZ, HAZ and base material showed no indication of Sn-containing phases. Since tin is limited to the surface of the pre-weld extrusions, surface material flowed into the nugget region, forming the particle-rich bands. Similarly, the particle-poor bands with no tin originated from within the thickness of the extrusions. A model of material flow during friction stir welding is proposed for which the weld nugget forms as surface material extrudes from the retreating side into a plasticized zone surrounding the FSW pin. The extruded column buckles between the extrusion force driving the material into the zone and the drag force of the in-situ material resisting its entry. A banded microstructure of interleaved surface material and in-situ material, therefore, develops. The model successfully describes several of the experimentally observed weld characteristics, but the model is limited to specific conditions of material flow and assumptions regarding steady-state.

  7. Metal Cutting Theory and Friction Stir Welding Tool Design

    NASA Technical Reports Server (NTRS)

    Payton, Lewis N.

    2003-01-01

    Friction Stir Welding (FSW) is a relatively new industrial process that was invented at The Weld Institute (TWI, United Kingdom) and patented in 1992 under research funded by in part by the National Aeronautics and Space Administration (NASA). Often quoted advantages of the process include good strength and ductility along with minimization of residual stress and distortion. Less well advertised are the beneficial effects of this solid state welding process in the field of occupational and environmental safety. It produces superior weld products in difficult to weld materials without producing any toxic fumes or solid waste that must be controlled as hazardous waste. In fact, it reduces noise pollution in the workspace as well. In the early days of FSW, most welding was performed on modified machine tools, in particular on milling machines with modified milling cutters. In spite of the obvious milling heritage of the process, the techniques and lessons learned from almost 250 years of successful metalworking with milling machines have not been applied in the field of modern Friction Stir Welding. The goal of the current research was to study currently successful FSW tools and parameterize the process in such a way that the design of new tools for new materials could be accelerated. Along the way, several successful new tooling designs were developed for current issues at the Marshall Space Flight Center with accompanying patent disclosures

  8. Pin Tool Geometry Effects in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Querin, J. A.; Rubisoff, H. A.; Schneider, J. A.

    2009-01-01

    In friction stir welding (FSW) there is significant evidence that material can take one of two different flow paths when being displaced from its original position in front of the pin tool to its final position in the wake of the weld. The geometry of the pin tool, along with the process parameters, plays an important role in dictating the path that the material takes. Each flow path will impart a different thermomechanical history on the material, consequently altering the material microstructure and subsequent weld properties. The intention of this research is to isolate the effect that different pin tool attributes have on the flow paths imparted on the FSWed material. Based on published weld tool geometries, a variety of weld tools were fabricated and used to join AA2219. Results from the tensile properties and microstructural characterization will be presented.

  9. Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

  10. Space Shuttle ET Friction Stir Weld Machines

    NASA Technical Reports Server (NTRS)

    Thompson, Jack M.

    2003-01-01

    NASA and Lockheed-Martin approached the FSW machine vendor community with a specification for longitudinal barrel production FSW weld machines and a shorter travel process development machine in June of 2000. This specification was based on three years of FSW process development on the Space Shuttle External Tank alloys, AL2 195-T8M4 and AL22 19-T87. The primary motivations for changing the ET longitudinal welds from the existing variable polarity Plasma Arc plasma weld process included: (1) Significantly reduced weld defect rates and related reduction in cycle time and uncertainty; (2) Many fewer process variables to control (5 vs. 17); (3) Fewer manufacturing steps; (4) Lower residual stresses and distortion; (5) Improved weld strengths, particularly at cryogenic temperatures; (6) Fewer hazards to production personnel. General Tool was the successful bidder. The equipment is at this writing installed and welding flight hardware. This paper is a means of sharing with the rest of the FSW community the unique features developed to assure NASA/L-M of successful production welds.

  11. The Influence of Friction Stir Weld Tool Form and Welding Parameters on Weld Structure and Properties: Nugget Bulge in Self-Reacting Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C., Jr.; Brendel, Michael S.

    2010-01-01

    Although friction stir welding (FSW) was patented in 1991, process development has been based upon trial and error and the literature still exhibits little understanding of the mechanisms determining weld structure and properties. New concepts emerging from a better understanding of these mechanisms enhance the ability of FSW engineers to think about the FSW process in new ways, inevitably leading to advances in the technology. A kinematic approach in which the FSW flow process is decomposed into several simple flow components has been found to explain the basic structural features of FSW welds and to relate them to tool geometry and process parameters. Using this modelling approach, this study reports on a correlation between the features of the weld nugget, process parameters, weld tool geometry, and weld strength. This correlation presents a way to select process parameters for a given tool geometry so as to optimize weld strength. It also provides clues that may ultimately explain why the weld strength varies within the sample population.

  12. Low-Temperature Friction-Stir Welding of 2024 Aluminum

    NASA Technical Reports Server (NTRS)

    Benavides, S.; Li, Y.; Murr, L. E.; Brown, D.; McClure, J. C.

    1998-01-01

    Solid state friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. However, the average residual, equiaxed, grain size in the weld zone has ranged from roughly 0.5 micron to slightly more than 10 micron, and the larger weld zone grain sizes have been characterized as residual or static grain growth as a consequence of the temperatures in the weld zone (where center-line temperatures in the FSW of 6061 Al have been shown to be as high as 480C or -0.8 T(sub M) where T(sub M) is the absolute melting temperature)). In addition, the average residual weld zone grain size has been observed to increase near the top of the weld, and to decrease with distance on either side of the weld-zone centerline, an d this corresponds roughly to temperature variations within the weld zone. The residual grain size also generally decreases with decreasing FSW tool rotation speed. These observations are consistent with the general rules for recrystallization where the recrystallized grain size decreases with increasing strain (or deformation) at constant strain rate, or with increasing strain-rate, or with increasing strain rate at constant strain; especially at lower ambient temperatures, (or annealing temperatures). Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction )proportional to the product of strain and strain-rate) will all influence both the recrystallization and growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low temperature welding. This

  13. Auto-Adjustable Tool for Self-Reacting and Conventional Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor)

    2002-01-01

    A friction stir welding dcvice that is configured to perform convention friction stir welding as well as self-reacting friction stir welding is described. A pin passes hrough an upper shoulder and can selectively attach 10 and detach from a lower shoulder in a preferred embodiment. A controller maintains thc discrete position of, and/or force applied by, the upper and lower shoulders during self-reacting friction stir welding, or maintains the pin at a desired depth and/or applied force during conventional friction stir welding.

  14. Crystallographic Texture in Bobbin Tool Friction-Stir-Welded Aluminum

    NASA Astrophysics Data System (ADS)

    Shen, Junjun; Wang, Feifan; Suhuddin, Uceu F. H.; Hu, Siyi; Li, Wenya; dos Santos, Jorge F.

    2015-07-01

    Bobbin tool friction-stir welding was used to join 3.2-mm-thick AA2198. The textural results show that four sub zones are formed vertically in the stirred zone. The materials in upper and lower two zones underwent negative and positive shears, respectively; they are uniformly recognized as dominate C and minor A simple shear components.

  15. Microstructures and electrochemical behaviors of the friction stir welding dissimilar weld.

    PubMed

    Shen, Changbin; Zhang, Jiayan; Ge, Jiping

    2011-06-01

    By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials. PMID:25084589

  16. Friction Stir Process Mapping Methodology

    NASA Technical Reports Server (NTRS)

    Kooney, Alex; Bjorkman, Gerry; Russell, Carolyn; Smelser, Jerry (Technical Monitor)

    2002-01-01

    In FSW (friction stir welding), the weld process performance for a given weld joint configuration and tool setup is summarized on a 2-D plot of RPM vs. IPM. A process envelope is drawn within the map to identify the range of acceptable welds. The sweet spot is selected as the nominal weld schedule. The nominal weld schedule is characterized in the expected manufacturing environment. The nominal weld schedule in conjunction with process control ensures a consistent and predictable weld performance.

  17. FRICTION STIR LAP WELDING OF ALUMINUM - POLYMER USING SCRIBE TECHNOLOGY

    SciTech Connect

    Upadhyay, Piyush; Hovanski, Yuri; Fifield, Leonard S.; Simmons, Kevin L.

    2015-02-16

    Friction Stir Scribe (FSS) technology is a relatively new variant of Friction Stir Welding (FSW) which enables lap joining of dissimilar material with very different melting points and different high temperature flow behaviors. The cutter scribe attached at the tip of FSW tool pin effectively cuts the high melting point material such that a mechanically interlocking feature is created between the dissimilar materials. The geometric shape of this interlocking feature determines the shear strength attained by the lap joint. This work presents first use of scribe technology in joining polymers to aluminum alloy. Details of the several runs of scribe welding performed in lap joining of ~3.175mm thick polymers including HDPE, filled and unfilled Nylon 66 to 2mm thick AA5182 are presented. The effect of scribe geometry and length on weld interlocking features is presented along with lap shear strength evaluations.

  18. Influence of microstructure on the properties of resistance spot welds

    SciTech Connect

    Santella, M.L.; Babu, S.S.; Riemer, B.W.; Feng, Z.

    1998-11-01

    An integrated model approach was proposed for relating resistance welding parameters to weldment properties. A key element of the approach is microstructure modeling. It was demonstrated that existing process models and microstructure models can be used to determine the spatial distribution of microstructures and properties in resistance spot welds of a plain carbon steel. It was also shown by finite element analysis that the existence of microstructure gradients in the welds is expected to reduce their ability to support shear loads by about 50%.

  19. Study of Mechanical Properties and Characterization of Pipe Steel welded by Hybrid (Friction Stir Weld + Root Arc Weld) Approach

    SciTech Connect

    Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; Wasson, Andrew J; Fairchild, Doug P; Wang, Yanli; Feng, Zhili

    2015-01-01

    Friction stir welding (FSW) has recently attracted attention as an alternative construction process for gas/oil transportation applications due to advantages compared to fusion welding techniques. A significant advantage is the ability of FSW to weld the entire or nearly the entire wall thickness in a single pass, while fusion welding requires multiple passes. However, when FSW is applied to a pipe or tube geometry, an internal back support anvil is required to resist the plunging forces exerted during FSW. Unfortunately, it may not be convenient or economical to use internal backing support due to limited access for some applications. To overcome this issue, ExxonMobil recently developed a new concept, combining root arc welding and FSW. That is, a root arc weld is made prior to FSW that supports the normal loads associated with FSW. In the present work, mechanical properties of a FSW + root arc welded pipe steel are reported including microstructure and microhardness.

  20. Friction Stir Welding of ODS and RAFM Steels

    NASA Astrophysics Data System (ADS)

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-01

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this work, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  1. Friction Stir Welding of ODS and RAFM Steels

    DOE PAGESBeta

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-14

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW onmore » grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.« less

  2. Prolegomena to the Study of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2010-01-01

    The literature contains many approaches toward modeling of the friction stir welding (FSW) process with varying treatments of the weld metal properties. It is worthwhile to consider certain fundamental features of the process before attempting to interpret FSW phenomena: Because of the unique character of metal deformation (as opposed to, say, viscous deformation) a velocity "discontinuity" or shear surface occurs in FSW and determines much of the character of the welding mechanism. A shear surface may not always produce a sound bond. Balancing mechanical power input against conduction and convection heat losses yields a relation, a "temperature index", between spindle speed and travel speed to maintain constant weld temperature. But many process features are only weakly dependent upon temperature. Thus, unlike modeling of metal forming processes, it may be that modeling the FSW process independently of the material conditions has some merit.

  3. Friction Stir Welding of ODS and RAFM Steels

    SciTech Connect

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-14

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  4. Weld-brazing of titanium. [resistance spot welding combined with brazing

    NASA Technical Reports Server (NTRS)

    Bales, T. T.; Royster, D. M.; Arnold, W. E., Jr.

    1973-01-01

    A joining process, designated weld-brazing, which combines resistance spot-welding and brazing has been developed at the NASA Langley Research Center. Resistance spot-welding is employed to position and aline the parts and to establish a suitable faying surface gap for brazing and contributes to the integrity of the joint. Brazing enhances the properties of the joint and reduces the stress concentrations normally associated with spotwelds. Ti-6Al-4V titanium alloy joints have been fabricated using 3003 aluminum braze both in a vaccum furnace and in a retort containing an inert gas environment.

  5. Friction stir welding and processing of oxide dispersion strengthened (ODS) alloys

    SciTech Connect

    Ren, Weiju

    2014-11-11

    A method of welding including forming a filler material of a first oxide dispersoid metal, the first oxide dispersoid material having first strengthening particles that compensate for decreases in weld strength of friction stir welded oxide dispersoid metals; positioning the filler material between a first metal structure and a second metal structure each being comprised of at least a second oxide dispersoid metal; and friction welding the filler material, the first metal structure and the second metal structure to provide a weld.

  6. Exploratory study of friction welds in Udimet 700 and TD-Nickel bar

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1971-01-01

    Friction welded butt joints were made in both Udimet 700 and TD-Nickel bar. Also, dissimilar metal friction welds were made between these materials. Friction welding of Udimet 700 shows great promise because the welds were found to be as strong as the parent metal in stress rupture and tensile tests at 760 and 980 C. The weld line was not detectable metallographically in the heat treated condition. Friction welding for TD-Nickel, however, holds little if any promise. TD-Nickel friction weldments could support only 9 percent as much stress as the base metal for a 10-hour stress-rupture life at 1090 C. Dissimilar Udimet 700/TD-Nickel friction welds could sustain only 15 percent as much stress as the TD-Nickel parent metal for a 10-hour rupture life at 930 C.

  7. Controlling Force and Depth in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Adams, Glynn; Loftus, Zachary; McCormac, Nathan; Venable, Richard

    2005-01-01

    Feedback control of the penetration force applied to a pin tool in friction stir welding has been found to be a robust and reliable means for controlling the depth of penetration of the tool. This discovery has made it possible to simplify depth control and to weld with greater repeatability, even on workpieces with long weld joints. Prior to this discovery, depths of penetration in friction stir welding were controlled by hard-tooled roller assemblies or by depth actuators controlled by feedback from such external sensors as linear variable-differential transformers or laser-based devices. These means of control are limited: A hard-tooled roller assembly confines a pin tool to a preset depth that cannot be changed easily during the welding process. A measurement by an external sensor is only an indirect indicative of the depth of penetration, and computations to correlate such a measurement with a depth of penetration are vulnerable to error. The present force-feedback approach exploits the proportionality between the depth and the force of penetration Unlike a depth measurement taken by an external sensor, a force measurement can be direct because it can be taken by a sensor coupled directly to the pin tool. The reading can be processed through a modern electronic servo control system to control an actuator to keep the applied penetration force at the desired level. In comparison with the older depth-control methods described above, this method offers greater sensitivity to plasticizing of the workpiece metal and is less sensitive to process noise, resulting in a more consistent process. In an experiment, a tapered panel was friction stir welded while controlling the force of penetration according to this method. The figure is a plot of measurements taken during the experiment, showing that force was controlled with a variation of 200 lb (890 N), resulting in control of the depth of penetration with a variation of 0.004 in. (0.1 mm).

  8. Simulation on friction taper plug welding of AA6063-20Gr metal matrix composite

    NASA Astrophysics Data System (ADS)

    Hynes, N. Rajesh Jesudoss; Nithin, Abeyram M.

    2016-05-01

    Friction taper plug welding a variant of friction welding is useful in welding of similar and dissimilar materials. It could be used for joining of composites to metals in sophisticated aerospace applications. In the present work numerical simulation of friction taper plug welding process is carried out using finite element based software. Graphite reinforced AA6063 is modelled using the software ANSYS 15.0 and temperature distribution is predicted. Effect of friction time on temperature distribution is numerically investigated. When the friction time is increased to 30 seconds, the tapered part of plug gets detached and fills the hole in the AA6063 plate perfectly.

  9. Interfacial characterization of joint between mild steel and aluminum alloy welded by resistance spot welding

    SciTech Connect

    Qiu Ranfeng; Shi Hongxin; Zhang Keke; Tu Yimin; Iwamoto, Chihiro; Satonaka, Shinobu

    2010-07-15

    The interfacial characteristics of resistance spot welded steel-aluminum alloy joint have been investigated using electron microscopy. The results reveal that reaction product FeAl{sub 3} is generated in the peripheral region of the weld while a reaction layer consisting of Fe{sub 2}Al{sub 5} adjacent to steel and FeAl{sub 3} adjacent to aluminum alloy forms in the central region of the weld, and that the morphology and thickness of the reaction layer vary with the position at the welding interface.

  10. Matrix phased array (MPA) imaging technology for resistance spot welds

    SciTech Connect

    Na, Jeong K.; Gleeson, Sean T.

    2014-02-18

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  11. Matrix phased array (MPA) imaging technology for resistance spot welds

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Gleeson, Sean T.

    2014-02-01

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  12. Developing Friction Stir Welding Process Model for ICME Application

    NASA Astrophysics Data System (ADS)

    Yang, Yu-Ping

    2015-01-01

    A framework for developing a product involving manufacturing processes was developed with integrated computational materials engineering approach. The key component in the framework is a process modeling tool which includes a thermal model, a microstructure model, a thermo-mechanical, and a property model. Using friction stir welding (FSW) process as an example, development of the process modeling tool was introduced in detail. The thermal model and the microstructure model of FSW of steels were validated with the experiment data. The model can predict reasonable temperature and hardness distributions as observed in the experiment. The model was applied to predict residual stress and joint strength of a pipe girth weld.

  13. Characterization of the Micro Textures in a Friction Stir Weld

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Nunes, Arthur C.

    2004-01-01

    In friction stir welding (FSW), a rotating threaded pin tool is inserted into a weld seam and literally stirs the edges of the seam together. The Dynamically-Recrystallized-Zone (DXZ) of a polished and etched FSW cross-section exhibits contrasting bands (the "onion-ring" structure), the origins of which are unclear. An orientation image mapping (OIM) study suggests that the corresponding bands may correspond respectively to a "straight-through" current of metal bypassing the pin tool in a single rotation or less and a "maelstrom" current rotating a number of times around the pin tool.

  14. Microstructural evolution of pure copper during friction-stir welding

    NASA Astrophysics Data System (ADS)

    Mironov, S.; Inagaki, K.; Sato, Y. S.; Kokawa, H.

    2015-02-01

    The microstructural evolution of pure copper during friction-stir welding was found to be principally influenced by welding temperature. At temperatures below ~0.5 Tm (where Tm is melting point), the microstructure was shown to be essentially determined by continuous recrystallization, leading to significant grain refinement and related material strengthening in the stir zone. In contrast, grain structure development at temperatures above ~0.5 Tm was dominated by discontinuous recrystallization producing a relatively coarse grain structure in the stir zone and giving rise to material softening.

  15. Computer simulation of resistance spot welding in aluminum: Part 1

    SciTech Connect

    Browne, D.J.; Chandler, H.W.; Evans, J.T.; Wen, J.

    1995-10-01

    A computer-based model of resistance spot welding with hemispherical electrode tips has been developed to include simulation of elastic-plastic mechanical deformation as well as ohmic heating and thermal conduction. The primary effect of the mechanical deformation is in its influence on the contact read and current density developed at the faying surface. The model was used to simulate spot welding in aluminum alloys. Preliminary results show the effects of variations in input current, contact resistance, applied force and position of the cooling water with respect to the electrode tip. It is shown that the value of the contact resistance has a large effect on nugget formation in the spot welding of aluminum alloys and that the applied force has a significant effect arising from its effect on the area of contact at the faying surface. The formation of a resistance spot weld in aluminum is also sensitive to the position of the cooling water-electrode interface because of the high thermal conductivity of aluminum alloys.

  16. Tensile Strength and Hardness Correlations with Microscopy in Friction welded Aluminium to Copper

    NASA Astrophysics Data System (ADS)

    Satish, Rengarajan; Seshagiri Rao, Vaddi; Ananthapadmanaban, Dattaguru; Ravi, Balappa

    2016-01-01

    Aluminium and copper are good conductors of heat and electricity, copper being the better conductor, is a costly metal indeed. On the other hand, aluminium is cheap, easily available and also has a lower density than copper. Hence, worldwide efforts are being made to partially replace copper wire. Solid state welding should be used to join aluminium to copper. This is because the use of fusion welding results in brittle phases formed in the weld interface. One of the solid state welding techniques used for joining aluminium to copper is friction welding. In this paper, an attempt has been made to join aluminium to copper by friction welding by varying the friction welding parameters, namely friction pressure, upset pressure, burn-off length and speed of rotation of the workpiece. Nine different friction welding parameter combinations were used during welding in accordance with ASTM standards and results have been reported. Tensile strength and hardness tests were carried out for each parameter combination. Optimum friction welding parameter combination was identified with respect to tensile strength. Scanning Electron Microscopy and Electron dispersive spectroanalysis were obtained to identify modes of fracture and presence of intermetallic phases for each friction welding combination with the aim to narrow down friction welding parameters that give good properties on the whole.

  17. Transition material improves spot welding of aluminum to steel

    SciTech Connect

    Not Available

    1994-06-01

    Weight is one of the primary enemies of improved fuel economy in automobiles. To help address this problem, a simple yet highly effective clad metal transition material has been developed. It allows automotive engineers to spot weld aluminum to steel using existing conventional production equipment and practices, thereby enabling them to use aluminum in place of heavier steel without expensive changes in production methods. The idea of the new materials technology is to permit the joining of aluminum to steel using conventional spot welding techniques. Numerous welding and corrosion studies have been conducted on the clad transition material approach by auto manufacturers, industry suppliers and various independent organizations. The success of these tests has prompted manufacturers in the US, Europe and Japan to accelerate production and field testing of clad transition materials on cars with an eye toward volume application.

  18. Identification of Damaged Spot Welds in a Complicated Joined Structure

    NASA Astrophysics Data System (ADS)

    Yunus, M. A.; Rani, M. N. Abdul; Ouyang, H.; Deng, H.; James, S.

    2011-07-01

    In automotive engineering, spot welds on assembled structures such as Body in White (BiW) have a significant effect on the vehicles' dynamic characteristics. Understandably, imperfections in the spot welds will cause variations in the dynamic properties such as natural frequencies and mode shapes of the structure. In this paper, a complicated welded structure which is a simplified Natural Gas Vehicle (NGV) platform is investigated. The structure fabricated from thin metal sheets consists of ten components. They are jointed together by a number of scattered spot welds. NASTRAN Solution 200 based on sensitivity analysis is used to identify the most sensitive parameters to natural frequencies. The numerical model of the undamaged structure is initially updated in order to minimise the discrepancies between the measured and numerical data using NASTRAN optimisation code. The initial updated model serves as a benchmark for the subsequent structural damage identification. The numerical data of the benchmark model is then compared with the measured data obtained from the damaged structure. The same updating procedure is applied to the benchmark model in order to bring the numerical data as close as possible to the measured data of the damaged structure. The disparity in certain parameter values from the parameter values used in the benchmark model shows a fault or damage in the location of a particular joint, depending on the severity of this disparity. The challenge in this work is to localise damaged area and quantify the damage of the complicated structure with multiple spot welds in the presence of uncertainty in the location and material properties of the welds.

  19. Advance in friction welding and ultrasonic welding of ceramics to metals

    SciTech Connect

    Greitmann, M.J.; Weib, R.

    1997-11-01

    The authors have joined four different ceramic materials (MgO-PSZ, Al{sub 2}O{sub 3}, SiC and Si{sub 3}N{sub 4} cylinders 10 mm in diameter and 50 mm in length) to the aluminum alloy Al-Si1MgMn by friction welding. Process parameters such as friction speed, axial force, burn-off and torque have been recorded continuously. For some specimens the authors recorded the temperature at the interface using thermocouples. The joints obtained were tested in tension. Fracture occurred either in the ceramic or at the interface. Heat conduction calculations to estimate the temperature distribution during welding have been conducted by the Finite Element Method (FEM), using experimental data for input. Afterwards, residual stresses introduced through thermal expansion mismatch and stresses introduced through a tensile test have been determined by FEM. Applying multiaxial Weibull statistics to the ceramic specimen, tensile strength for different geometries of the joint and different material combinations was estimated. Ultrasonic welded joints of MgO-PSZ and Steel X 4 CrNi 18-10 according to DIN EN (comparable to the US-steel AISI No. 304) could be realized using aluminum interlayers. In addition to a conventional ultrasonic welding equipment for metal welding a new molecular coldwelding technique (ultrasonic torsional welding system) was tested. In comparison to friction welding the ultrasonic welding technique results in limited deformation of the ceramic-metal joint parts and in a decreased welding time. Nevertheless a special solution must be found to the problem of tool wear and the vibration conditions.

  20. Preliminary investigation of inertia friction welding B2 aluminides

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Moore, Thomas J.; Kuruzar, Daniel L.

    1987-01-01

    An attempt is made to achieve inertia friction-welding in FeAl and NiAl samples, taking into account their intermetallics' compositions, extrusion parameters, and microstructural data. The energy required for the weld is stored in a rotating flywheel mass attached to one of the two pieces to be joined; when enough energy is introduced, the flywheel is disconnected and an axial load is applied which forces the spinning piece against the stationary one, converting the energy into heat by means of friction. Due to the inherent brittleness of the aluminides, a step-load program was used in which an initial, low-pressure heat buildup increased the work pieces' ductility.

  1. Mechanical Property and Microstructure of Linear Friction Welded WASPALOY

    NASA Astrophysics Data System (ADS)

    Chamanfar, A.; Jahazi, M.; Gholipour, J.; Wanjara, P.; Yue, S.

    2011-03-01

    The mechanical properties and microstructural evolution of WASPALOY joined by linear friction welding (LFW) were investigated in this study. In-situ temperature measurements using thermocouple probes indicated exposure of the weld area to a temperature of at least 1400 K (1126 °C). Based on electron backscatter diffraction (EBSD) mapping of the weldments, up to 50 pct reduction in γ grain size occurred within 0.9 mm of the weld interface as a result of dynamic recrystallization (DRX). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed that progressive dissolution of γ' precipitates took place from the base metal to the weld interface, where almost no γ' precipitates were observed. Within 3.3 mm of the weld interface, the γ' dissolution significantly influenced the hardness profile measured across the extended thermomechanically affected zones (TMAZs). Investigation of strain distributions during tensile testing using the optical Aramis system revealed weak bonding at the edge of the weld due to oxidation. To extrude out oxide layers into the flash, increasing the axial shortening to higher than 1.2 mm is recommended.

  2. Modal testing and finite element model updating of laser spot welds

    NASA Astrophysics Data System (ADS)

    Abu Husain, N.; Haddad Khodaparast, H.; Snaylam, A.; James, S.; Sharp, M.; Dearden, G.; Ouyang, H.

    2009-08-01

    Spot welds are used extensively in automotive engineering. One of the latest manufacturing techniques for producing spot welds is Laser Welding. Finite element (FE) modelling of laser welds for dynamic analysis is a research issue because of the complexity and uncertainty of the welds and thus formed structures. In this work, FE model of the welds is developed by employing CWELD element in NASTRAN and its feasibility for representing laser spot welds is investigated. The FE model is updated based on the measured modal data of hat-plate structures and cast as a structural minimisation problem by the application of NASTRAN codes.

  3. High-Speed Friction-Stir Welding to Enable Aluminum Tailor-Welded Blanks

    NASA Astrophysics Data System (ADS)

    Hovanski, Yuri; Upadhyay, Piyush; Carsley, John; Luzanski, Tom; Carlson, Blair; Eisenmenger, Mark; Soulami, Ayoub; Marshall, Dustin; Landino, Brandon; Hartfield-Wunsch, Susan

    2015-05-01

    Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and they have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high volumes. While friction-stir welding (FSW) has been traditionally applied at linear velocities less than 1 m/min, high-volume production applications demand the process be extended to higher velocities more amenable to cost-sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low-to-moderate welding velocities do not directly translate to high-speed linear FSW. Therefore, to facilitate production of high-volume aluminum FSW components, parameters were developed with a minimum welding velocity of 3 m/min. With an emphasis on weld quality, welded blanks were evaluated for postweld formability using a combination of numerical and experimental methods. An evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum TWBs, which provided validation of the numerical and experimental analysis of laboratory-scale tests.

  4. An Alternative Frictional Boundary Condition for Computational Fluid Dynamics Simulation of Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Chen, Gaoqiang; Feng, Zhili; Zhu, Yucan; Shi, Qingyu

    2016-07-01

    For better application of numerical simulation in optimization and design of friction stir welding (FSW), this paper presents a new frictional boundary condition at the tool/workpiece interface for computational fluid dynamics (CFD) modeling of FSW. The proposed boundary condition is based on an implementation of the Coulomb friction model. Using the new boundary condition, the CFD simulation yields non-uniform distribution of contact state over the tool/workpiece interface, as validated by the experimental weld macrostructure. It is found that interfacial sticking state is present over large area at the tool-workpiece interface, while significant interfacial sliding occurs at the shoulder periphery, the lower part of pin side, and the periphery of pin bottom. Due to the interfacial sticking, a rotating flow zone is found under the shoulder, in which fast circular motion occurs. The diameter of the rotating flow zone is smaller than the shoulder diameter, which is attributed to the presence of the interfacial sliding at the shoulder periphery. For the simulated welding condition, the heat generation due to friction and plastic deformation makes up 54.4 and 45.6% of the total heat generation rate, respectively. The simulated temperature field is validated by the good agreement to the experimental measurements.

  5. Weld-brazing - a new joining process. [combination resistance spot welding and brazing of titanium alloys

    NASA Technical Reports Server (NTRS)

    Bales, T. T.; Royster, D. M.; Arnold, W. E., Jr.

    1972-01-01

    A joining process designated weld brazing which combines resistance spot welding and brazing has been developed. Resistance spot welding is used to position and align the parts as well as to establish a suitable faying surface gap for brazing. Fabrication is then completed by capillary flow of the braze alloy into the joint. The process has been used successfully to fabricate Ti-6Al-4V titanium alloy joints using 3003 aluminum braze alloy. Test results obtained on single overlap and hat-stiffened structural specimens show that weld brazed joints are superior in tensile shear, stress rupture, fatigue, and buckling than joint fabricated by spotwelding or brazing. Another attractive feature of the process is that the brazed joints is hermetically sealed by the braze material.

  6. Microstructural Analysis of Linear Friction-Welded 718 Plus Superalloy

    NASA Astrophysics Data System (ADS)

    Vishwakarma, K. R.; Ojo, O. A.; Wanjara, P.; Chaturvedi, M. C.

    2014-12-01

    The microstructure of Allvac 718 Plus (718 Plus; ATI, Pittsburgh, PA, USA) superalloy was examined after linear friction welding (LFW) and after standard postweld heat treatment (PWHT). The liquid phase reaction of second-phase precipitates, which are known to constitutionally liquate during conventional fusion welding, was observed in the thermomechanically affected zone (TMAZ) of the welded material. These phases included MC-type carbides, Ti-rich carbonitrides, and δ phase precipitates. This observation is contrary to the general assumption that LFW is a completely solid-state joining process. However, unlike conventional fusion welding processes that cause heat-affected zone liquation cracking in 718 Plus and many other superalloys, the LFW process did not cause cracking in 718 Plus superalloy despite the liquation of precipitates. This absence of cracking during joining is attributed to the applied compressive stress during the forging stage of the LFW process. Also, no cracking was observed after PWHT, although PWHT resulted in a microstructure that had a nonhomogeneous distribution of precipitates in the weld and the TMAZ.

  7. Effect of Pre- and Post-weld Heat Treatments on Linear Friction Welded Ti-5553

    NASA Astrophysics Data System (ADS)

    Wanjara, Priti; Dalgaard, Elvi; Gholipour, Javad; Cao, Xinjin; Cuddy, Jonathan; Jonas, John J.

    2014-10-01

    Linear friction welding allows solid-state joining of near-beta ( β) titanium alloy Ti-5553 (Ti-5Al-5V-5Mo-3Cr). In the as-welded condition, the weld zone (WZ) exhibits β grain refinement and marked softening as compared with Ti-5553 in the solution heat treated and aged condition. The softening of the weldment is attributed to the depletion of the strengthening alpha ( α) phase in the WZ and the adjacent thermo-mechanically affected zone (TMAZ). Specifically, in near- β titanium alloys, the strength of the material mainly depends on the shape, size, distribution, and fraction of the primary α and other decomposition products of the β phase. Hence, a combination of pre- and post-weld heat treatments were applied to determine the conditions that allow mitigating the α phase depletion in the WZ and TMAZ of the welds. The mechanical response of the welded samples to the heat treatments was determined by performing microhardness measurements and tensile testing at room temperature with an automated 3D deformation measurement system. It was found that though the joint efficiency in the as-welded condition was high (96 pct), strain localization and failure occurred in the TMAZ. The application of post-weld solution heat treatment with aging was effective in restoring α, increasing the joint efficiency (97 to 99 pct) and inducing strain localization and failure in the parent material region.

  8. Auto-adjustable pin tool for friction stir welding

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Oelgoetz, Peter A. (Inventor)

    1999-01-01

    An auto-adjusting pin tool for friction stir welding is presented wherein the pin tool automatically adjusts for welding materials of varying thicknesses, and the pin can be incrementally withdrawn from the workpieces thus eliminating any crater or keyhole in the weld. The inventive apparatus is comprised of a welding head housing a motor connected to a controller instrument package and an arbor supported by bearings. The arbor forms an interior cylinder and is encircled by a stationary slip ring though which are ported hydraulic passageways into the interior cylinder of the arbor such that a piston housed therein may be moved axially. Coupled to the piston is a pin tool which is treaded on its lower end and which is moveably seated in, and extending through, a shoulder housing having concave lower face. When welding, the rotating treaded end of the pin enters and stirs the workpieces while the lower face of the shoulder housing compacts the workpieces. As the welding head traverses the shoulder housing the controller senses any rising pressure on the lower face of the shoulder housing and withdraws the arbor to keep the pressure constant. At the same time, the piston moves towards the workpieces thus extending the pin further from the shoulder. This keeps the pin at a proper depth in the workpieces regardless of their thicknesses. As the weld terminates this same operation can be used to incrementally withdraw the pin during the final part of the traverse, thus eliminating any keyhole or crater that would otherwise be created.

  9. Analysis of ripple formation in single crystal spot welds

    NASA Technical Reports Server (NTRS)

    Rappaz, M.; Corrigan, D.; Boatner, L. A.

    1997-01-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 micrometers and spacing, typically approximately 60 micrometers) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f(sub 0) given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v(sub s)/f(sub 0), where v(sub s) is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  10. Bobbin-Tool Friction-Stir Welding of Thick-Walled Aluminum Alloy Pressure Vessels

    SciTech Connect

    Dalder, E C; Pastrnak, J W; Engel, J; Forrest, R S; Kokko, E; Ternan, K M; Waldron, D

    2007-06-06

    It was desired to assemble thick-walled Al alloy 2219 pressure vessels by bobbin-tool friction-stir welding. To develop the welding-process, mechanical-property, and fitness-for-service information to support this effort, extensive friction-stir welding-parameter studies were conducted on 2.5 cm. and 3.8 cm. thick 2219 Al alloy plate. Starting conditions of the plate were the fully-heat-treated (-T62) and in the annealed (-O) conditions. The former condition was chosen with the intent of using the welds in either the 'as welded' condition or after a simple low-temperature aging treatment. Since preliminary stress-analyses showed that stresses in and near the welds would probably exceed the yield-strength of both 'as welded' and welded and aged weld-joints, a post-weld solution-treatment, quenching, and aging treatment was also examined. Once a suitable set of welding and post-weld heat-treatment parameters was established, the project divided into two parts. The first part concentrated on developing the necessary process information to be able to make defect-free friction-stir welds in 3.8 cm. thick Al alloy 2219 in the form of circumferential welds that would join two hemispherical forgings with a 102 cm. inside diameter. This necessitated going to a bobbin-tool welding-technique to simplify the tooling needed to react the large forces generated in friction-stir welding. The bobbin-tool technique was demonstrated on both flat-plates and plates that were bent to the curvature of the actual vessel. An additional issue was termination of the weld, i.e. closing out the hole left at the end of the weld by withdrawal of the friction-stir welding tool. This was accomplished by friction-plug welding a slightly-oversized Al alloy 2219 plug into the termination-hole, followed by machining the plug flush with both the inside and outside surfaces of the vessel. The second part of the project involved demonstrating that the welds were fit for the intended service. This

  11. Preliminary Study of a Pull Plug Friction Weld

    NASA Technical Reports Server (NTRS)

    Buchanan, George R.

    1999-01-01

    A pull plug friction weld, simply defined, comprises inserting a rotating cone-shaped cylinder into a somewhat cone-shaped hole in a plate. The rotating plug makes contact with the edge of the plate and the resulting friction generates heat. The temperature of the plate material eventually reaches a magnitude that will cause the plate material at the edge of the hole to flow. This can be termed a temperature dependent plastic flow. The rotation of the plug is terminated, additional pressure is applied and the metal at the interface of the two materials cools and welding occurs. This preliminary study addresses only three aspects of a complete analysis that is multi-faceted. The transient temperature distribution for different pull plug configurations has been studied in some detail even though the initial conditions and boundary conditions may still be deemed tentative. The stress distribution within the pull plug caused by the heating pressure was studied along with a preliminary analysis of the thermoelastic stress distribution caused by friction heating. There are no definitive results for the stress analysis. Additional study will be required.

  12. The application of statistically designed experiments to resistance spot welding

    NASA Technical Reports Server (NTRS)

    Hafley, Robert A.; Hales, Stephen J.

    1991-01-01

    State-of-the-art Resistance Spot Welding (RSW) equipment has the potential to permit realtime monitoring of operations through advances in computerized process control. In order to realize adaptive feedback capabilities, it is necessary to establish correlations among process variables, welder outputs, and weldment properties. The initial step toward achieving this goal must involve assessment of the effect of specific process inputs and the interactions among these variables on spot weld characteristics. This investigation evaluated these effects through the application of a statistically designed experiment to the RSW process. A half-factorial, Taguchi L sub 16 design was used to understand and refine a RSW schedule developed for welding dissimilar aluminum-lithium alloys of different thickness. The baseline schedule had been established previously by traditional trial and error methods based on engineering judgment and one-factor-at-a-time studies. A hierarchy of inputs with respect to each other was established, and the significance of these inputs with respect to experimental noise was determined. Useful insight was gained into the effect of interactions among process variables, particularly with respect to weldment defects. The effects of equipment related changes associated with disassembly and recalibration were also identified. In spite of an apparent decrease in equipment performance, a significant improvement in the maximum strength for defect-free welds compared to the baseline schedule was achieved.

  13. Effect of Weld Tool Geometry on Friction Stir Welded Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Querin, Joseph A.; Schneider, Judy A.

    2008-01-01

    In this study, flat 0.250" thick Ti-6Al-4V panels were friction stir welded (FSWed) using weld tools with tapered pins. The five different pin geometries of the weld tools included: 0 degree (straight cylinder), 15 degree, 30 degree, 45 degree, and 60 degree angles on the frustum. All weld tools had a smooth 7 degree concave shoulder and were made from microwave sintered tungsten carbide. For each weld tool geometry, the FSW process parameters were optimized to eliminate internal defects. All the welds were produced in position control with a 2.5 degree lead angle using a butt joint configuration for the panels. The process parameters of spindle rpm and travel speed were varied, altering the hot working conditions imparted to the workpiece. Load cells on the FSWing machine allowed for the torque, the plunge force, and the plow force to be recorded during welding. Resulting mechanical properties were evaluated from tensile tests results of the FSWjoints. Variations in the material flow were investigated by use of microstructural analysis including optical microscopy (OM), scanning electron microscopy (SEM), and orientation image mapping (aIM).

  14. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Mazumder, B.; Yu, X.; Edmondson, P. D.; Parish, C. M.; Miller, M. K.; Meyer, H. M.; Feng, Z.

    2016-02-01

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygen-enriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the size of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.

  15. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    DOE PAGESBeta

    Mazumder, Baishakhi; Yu, Xinghua; Edmondson, Philip D.; Parish, Chad M.; Miller, Michael K; Meyer, H. M.; Feng, Zhili

    2015-12-08

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygenenriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the sizemore » of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.« less

  16. Effect of friction stir welding and post-weld heat treatment on a nanostructured ferritic alloy

    SciTech Connect

    Mazumder, Baishakhi; Yu, Xinghua; Edmondson, Philip D.; Parish, Chad M.; Miller, Michael K; Meyer, H. M.; Feng, Zhili

    2015-12-08

    Nanostructured ferritic alloys (NFAs) are new generation materials for use in high temperature energy systems, such as nuclear fission or fusion reactors. However, joining these materials is a concern, as their unique microstructure is destroyed by traditional liquid-state welding methods. The microstructural evolution of a friction stir welded 14YWT NFA was investigated by atom probe tomography, before and after a post-weld heat treatment (PWHT) at 1123K. The particle size, number density, elemental composition, and morphology of the titanium-yttrium-oxygenenriched nanoclusters (NCs) in the stir and thermally-affected zones were studied and compared with the base metal. No statistical difference in the size of the NCs was observed in any of these conditions. After the PWHT, increases in the number density and the oxygen enrichment in the NCs were observed. Therefore, these new results provide additional supporting evidence that friction stir welding appears to be a viable joining technique for NFAs, as the microstructural parameters of the NCs are not strongly affected, in contrast to traditional welding techniques.

  17. Friction Stir Welded Thin Wall Cryogenic Tank Skins

    NASA Astrophysics Data System (ADS)

    Potter, David M.; Takeshita, Jennifer A.; Holguin, Michael J.

    2007-01-01

    A cryogenic propellant tank is the common element of trans-planetary transportation systems, in-space storage depots, lunar landers, in-space habitats/laboratories, ascent/descent, and launch vehicles. Lockheed Martin's (LM) cryogenic tank approach integrates Friction Stir Welding (FSW) with thin-gage aluminum monocoque structural design, common spin formed FSW domes and variable tank lengths to tailor the cryogenic tank from smaller stages, such as landers or ascent/descent stages, to very large on-orbit or In Space Resource Utilization (ISRU) storage systems. Thin gage corrosion resistant steel (CRES) construction combined with normal fusion welding as used on LM's Centaur has already been demonstrated to provide the highest cryogenic tank mass fraction (~.90) for large scale, cryogenic propellant storage. However, current fusion welding technology is limited by the alloys that are considered weldable and typically achieves only 50% of the parent material ultimate strength at the weld joint. Preliminary LM technology development indicates that in certain aluminum alloys, the FSW joint retains up to 100% of the parent material ultimate strength at LH2 temperatures. Combining FSW and aluminum monocoque tank design would create a large scale cryogenic tank with a mass fraction in excess of the current industry standard and therefore is ideal for affordable, reliable, high capacity propellant storage required for all facets of space exploration.

  18. Interfacial Reaction during Friction Stir Welding of Al and Cu

    NASA Astrophysics Data System (ADS)

    Genevois, C.; Girard, M.; Huneau, B.; Sauvage, X.; Racineux, G.

    2011-08-01

    Commercially pure copper was joined to a 1050 aluminum alloy by friction stir welding. A specific configuration where the tool pin was fully located in the aluminum plate was chosen. In such a situation, there is no mechanical mixing between the two materials, but frictional heating gives rise to a significant thermally activated interdiffusion at the copper/aluminum interface. This gives rise to the formation of defect-free joints where the bonding is achieved by a very thin intermetallic layer at the Cu/Al interface. Nanoscaled grains within this bonding layer were characterized using transmission electron microscopy (TEM). Two phases were identified, namely, Al2Cu and Al4Cu9 phases. The nucleation and growth of these two phases are discussed and compared to the standard reactive interdiffusion reactions between Cu and Al.

  19. Effects of Laser Peening, and Shot Peening, on Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Hatamleh, Omar; Hackel, Lloyd; Rankin, Jon; Truong, Chanh; Walter, Matt

    2006-01-01

    A viewgraph presentation describing the effects of laser peening and shot peening on friction stir welding is shown. The topics include: 1) Background; 2) Friction Stir Welding (FSW); 3) Microstructure; 4) Laser & Shot Peening; 5) Residual Stresses; 6) Tensile Behavior; 7) Fatigue Life & Surface Roughness; 8) Crack Growth; and 9) Benefits.

  20. IR-based spot weld NDT in automotive applications

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Feng, Zhili

    2015-05-01

    Today's auto industry primarily relies on destructive teardown evaluation to ensure the quality of the resistance spot welds (RSWs) due to their criticality in crash resistance and performance of vehicles. The destructive teardown evaluation is labor intensive and costly. The very nature of the destructive test means only a few selected welds will be sampled for quality. Most of the welds in a car are never checked. There are significant costs and risks associated with reworking and scrapping the defective welded parts made between the teardown tests. IR thermography as a non-destructive testing (NDT) tool has its distinct advantage — its non-intrusive and non-contact nature. This makes the IR based NDT especially attractive for the highly automated assembly lines. IR for weld quality inspection has been explored in the past, mostly limited to the offline post-processing manner in a laboratory environment. No online real-time RSW inspection using IR thermography has been reported. Typically for postprocessing inspection, a short-pulse heating via xenon flash lamp light (in a few milliseconds) is applied to the surface of a spot weld. However, applications in the auto industry have been unsuccessful, largely due to a critical drawback that cannot be implemented in the high-volume production line - the prerequisite of painting the weld surface to eliminate surface reflection and other environmental interference. This is due to the low signal-to-noise ratio resulting from the low/unknown surface emissivity and the very small temperature changes (typically on the order of 0.1°C) induced by the flash lamp method. An integrated approach consisting of innovations in both data analysis algorithms and hardware apparatus that effectively solved the key technical barriers for IR NDT. The system can be used for both real-time (during welding) and post-processing inspections (after welds have been made). First, we developed a special IR thermal image processing method that

  1. Some microstructural characterisations in a friction stir welded oxide dispersion strengthened ferritic steel alloy

    NASA Astrophysics Data System (ADS)

    Legendre, F.; Poissonnet, S.; Bonnaillie, P.; Boulanger, L.; Forest, L.

    2009-04-01

    The goal of this study is to characterize microstructure of a friction stir welded oxide dispersion strengthened alloy. The welded material is constituted by two sheets of an yttria-dispersion-strengthened PM 2000 ferritic steel. Different areas of the friction stir welded product were analyzed using field emission gun secondary electron microscopy (FEG-SEM) and electron microprobe whereas nanoindentation was used to evaluate mechanical properties. The observed microstructural evolution, including distribution of the yttria dispersoids, after friction stir welding process is discussed and a correlation between the microstructure and the results of nanoindentation tests is established.

  2. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    SciTech Connect

    Tang, Wei; Chen, Gaoqiang; Chen, Jian; Yu, Xinghua; Frederick, David Alan; Feng, Zhili

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  3. Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Russell, Carolyn

    2012-01-01

    Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.

  4. Friction Stir Welding of a Thick Al-Zn-Mg Alloy Plate

    NASA Astrophysics Data System (ADS)

    Buchibabu, V.; Reddy, G. M.; Kulkarni, D.; De, A.

    2016-03-01

    Al-Zn-Mg alloys are widely used as structural materials due to high strength-to-weight ratio and impact toughness. As fusion welds in these alloys commonly face hot cracking and macro porosity, friction stir welding is increasingly becoming the preferred recourse. We report here a detailed experimental study on friction stir welding of a specific Al-Zn-Mg alloy with its chemical compositions close to AA7039. The effect of tool rotational speed and welding speed on the weld profile, joint microstructure, and mechanical properties is studied extensively. The results show sound weld profiles and joint properties within the selected range of process conditions. Within the selected range of welding conditions, the welds made at a tool rotational speed of 350 rpm and welding speed of 3 mm/s have showed joint structure, tensile, and impact toughness properties fairly close to that of the base material.

  5. Thermal Performance Evaluation of Friction Stir Welded and Bolted Cold Plates with Al/Cu Interface

    NASA Astrophysics Data System (ADS)

    Lakshminarayanan, A. K.; Suresh, M.; Sibi Varshan, M.

    2015-05-01

    An attempt is made to design and fabricate a cold plate with aluminum-copper dissimilar interface joined by friction stir welding. Optimum welding conditions for obtaining sound-quality corner and T joints with an aluminum-copper interface were established. Welded cross sections of the friction stir welded cold plate were analyzed to understand the bonding characteristics. Computational fluid dynamics (CFD) was used to evaluate the fluid-flow characteristics and thermal resistance of friction stir welded cold plate and the resulted are compared with the conventional bolted cold plate configuration. For CFD modeling of a cold plate with a dissimilar interface, a new methodology is proposed. From the CFD analysis and experimental results, it is observed that friction stir welded cold plate offered better thermal performance compared to the bolted cold plate and it is due to the metallurgical bonding at the aluminum-copper interface with the dispersion of copper particles.

  6. Initial Development in Joining of ODS Alloys Using Friction Stir Welding

    SciTech Connect

    Ren, Weiju; Feng, Zhili

    2007-08-01

    Solid-state welding of oxide-dispersion-strengthened (ODS) alloy MA956 sheets using friction stir welding (FSW) was investigated. Butt weld was successfully produced. The weld and base metals were characterized using optical microscopy, scanning electronic microscopy, transmission electronic microscopy, and energy dispersion x-ray spectrum. Microhardness mapping was also conducted over the weld region. Analyses indicate that the distribution of the strengthening oxides was preserved in the weld. Decrease in microhardness of the weld was observed but was insignificant. The preliminary results seem to confirm the envisioned feasibility of FSW application to ODS alloy joining. For application to Gen IV nuclear reactor heat exchanger, further investigation is suggested.

  7. Microstructural Investigation of Friction-Stir-Welded 7005 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Xuesong; Lu, Yan; Zheng, Feiyan; Chen, Bin

    2015-11-01

    This paper is aimed to investigate the microstructure of 7005 aluminum sheets joined by friction-stir welding as well as their mechanical properties. Specimens with ten different sets of welding parameters were studied. Tensile test and fracture analysis determined that the joint of the best quality was obtained at the rotation speed of 1000 rpm matching with the travel speed of 200 mm/min, and the travel speed has more impact on the ultimate tensile strength. Optical microscope observation was applied to this high-quality specimen and gave evidence to explaining the formation of the onion ring structure. Electron back-scattered diffraction (EBSD) technique was employed to characterize the textures and revealed the evolution of microstructures during friction stir processing. The EBSD results showed that the grains maintain their original orientations at relatively low deformation while the orientations rotate under increasing strain. Accumulated rotation will turn the textures into mixed shear components, which finally results in grain refinement and contributes to the high quality of the joint.

  8. Microstructure of AA 2024 fixed joints formed by friction stir welding

    NASA Astrophysics Data System (ADS)

    Eliseev, A. A.; Kalashnikova, T. A.; Tarasov, S. Yu.; Rubtsov, V. E.; Fortuna, S. V.; Kolubaev, E. A.

    2015-10-01

    Friction stir welded butt joints on 2024T3 alloy have been obtained using different process parameters. The microstructures of all the weld joint zones have been examined and such structural parameters as grain size, particle size and volume content of particles have been determined in order to find correlations with the microhardness of the corresponding zones of the weld.

  9. Joining precipitation-hardened nickel-base alloys by friction welding

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1972-01-01

    Solid state deformation welding process, friction welding, has been developed for joining precipitation hardened nickel-base alloys and other gamma prime-strengthened materials which heretofore have been virtually unweldable. Method requires rotation of one of the parts to be welded, but where applicable, it is an ideal process for high volume production jobs.

  10. Manual adjustable probe tool for friction stir welding

    NASA Technical Reports Server (NTRS)

    Oelgoetz, Peter A. (Inventor); Ding, Jeff (Inventor)

    2000-01-01

    A friction stir welding tool is provided generally comprising three parts: a rotatable welding tool body (22) that has an outer threaded surface (32) and a probe (24) extending from a distal end of the body, a shoulder (26), which has a threaded inner surface (40) and a bore (36) at a distal end of the shoulder, and a jam nut (28), which has a threaded inner surface (42). The shoulder is threaded onto the tool body such that the probe extends from the shoulder through the bore by a preferred length. The jam nut is then threaded onto the tool body to secure the shoulder. The tool is operatively connected to a drive motor for rotating the tool body. The shoulder may include a knife edge projecting from the distal end (38) thereof adjacent the bore. The knife edge inhibits the weld material from migrating along the probe to intrude inside the shoulder, where it may prevent separation of the tool body and the shoulder when readjustment of the tool is necessary.

  11. Investigation of influence of friction stir welding regimes on the features of mass transfer and temperature distribution in forming welds

    NASA Astrophysics Data System (ADS)

    Astafurov, S. V.; Shilko, E. V.; Kolubaev, E. A.; Psakhie, S. G.

    2015-10-01

    Computer simulation by the movable cellular automaton method was performed to study the influence of friction stir welding regimes on the features of intensive mass transfer and temperature distribution in forming welded joints. The calculation results showed that there is a range of optimal values of the ratio of the angular velocity to the welding speed which provides sufficient mass transfer to form a welded joint with a minimum volume content of defects. The use of the optimal FSW regimes allows to obtain joints without significant overheating of the welded materials.

  12. Counterrotating-Shoulder Mechanism for Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2007-01-01

    A counterrotating-shoulder mechanism has been proposed as an alternative to the mechanism and fixtures used in conventional friction stir welding. The mechanism would internally react most or all of the forces and torques exerted on the workpiece, making it unnecessary to react the forces and torques through massive external fixtures. In conventional friction stir welding, a rotating pin tool is inserted into, and moved along, a weld seam. As the pin tool moves, it stirs together material from the opposite sides of the seam to form the weld. A large axial plunge force must be exerted upon the workpiece through and by the pin tool and a shoulder attached above the pin tool in order to maintain the pressure necessary for the process. The workpiece is secured on top of an anvil, which supports the workpiece against the axial plunge force and against the torque exerted by the pin tool and shoulder. The anvil and associated fixtures must be made heavy (and, therefore, are expensive) to keep the workpiece stationary. In addition, workpiece geometries must be limited to those that can be accommodated by the fixtures. The predecessor of the proposed counterrotating-shoulder mechanism is a second-generation, self-reacting tool, resembling a bobbin, that makes it possible to dispense with the heavy anvil. This tool consists essentially of a rotating pin tool with opposing shoulders. Although the opposing shoulders maintain the necessary pressure without need to externally apply or react a large plunge force, the torque exerted on the workpiece remains unreacted in the absence of a substantial external fixture. Depending on the RPM and the thickness of the workpiece, the torque can be large. The proposed mechanism (see figure) would include a spindle attached to a pin tool with a lower shoulder. The spindle would be coupled via splines to the upper one of three bevel gears in a differential drive. The middle bevel gear would be the power-input gear and would be coupled to the

  13. Study of mechanical joint strength of aluminum alloy 7075-T6 and dual phase steel 980 welded by friction bit joining and weld-bonding under corrosion medium

    DOE PAGESBeta

    Lim, Yong Chae; Squires, Lile; Pan, Tsung-Yu; Miles, Michael; Song, Guang-Ling; Wang, Yanli; Feng, Zhili

    2014-12-30

    We have employed a unique solid-sate joining process, called friction bit joining (FBJ), to spot weld aluminum alloy (AA) 7075-T6 and dual phase (DP) 980 steel. Static joint strength was studied in the lap shear tension configuration. In addition, weld-bonding (adhesive + FBJ) joints were studied in order to evaluate the ability of adhesive to mitigate the impact of corrosion on joint properties. Accelerated laboratory cyclic corrosion tests were carried out for both FBJ only and weld-bonding joints. Furthermore, the FBJ only joints that emerged from corrosion testing had lap shear failure loads that were significantly lower than freshly preparedmore » joints. However, weld-bonding specimens retained more than 80% of the lap shear failure load of the freshly prepared weld-bonding specimens. Moreover, examination of joint cross sections confirmed that the presence of adhesive in the weld-bonding joints mitigated the effect of the corrosion environment, compared to FBJ only joints.« less

  14. Ultrasonic Real-Time Quality Monitoring Of Aluminum Spot Weld Process

    NASA Astrophysics Data System (ADS)

    Perez Regalado, Waldo Josue

    The real-time ultrasonic spot weld monitoring system, introduced by our research group, has been designed for the unsupervised quality characterization of the spot welding process. It comprises the ultrasonic transducer (probe) built into one of the welding electrodes and an electronics hardware unit which gathers information from the transducer, performs real-time weld quality characterization and communicates with the robot programmable logic controller (PLC). The system has been fully developed for the inspection of spot welds manufactured in steel alloys, and has been mainly applied in the automotive industry. In recent years, a variety of materials have been introduced to the automotive industry. These include high strength steels, magnesium alloys, and aluminum alloys. Aluminum alloys have been of particular interest due to their high strength-to-weight ratio. Resistance spot welding requirements for aluminum vary greatly from those of steel. Additionally, the oxide film formed on the aluminum surface increases the heat generation between the copper electrodes and the aluminum plates leading to accelerated electrode deterioration. Preliminary studies showed that the real-time quality inspection system was not able to monitor spot welds manufactured with aluminum. The extensive experimental research, finite element modelling of the aluminum welding process and finite difference modeling of the acoustic wave propagation through the aluminum spot welds presented in this dissertation, revealed that the thermodynamics and hence the acoustic wave propagation through an aluminum and a steel spot weld differ significantly. For this reason, the hardware requirements and the algorithms developed to determine the welds quality from the ultrasonic data used on steel, no longer apply on aluminum spot welds. After updating the system and designing the required algorithms, parameters such as liquid nugget penetration and nugget diameter were available in the ultrasonic data

  15. Weld Bead Size, Microstructure and Corrosion Behavior of Zirconium Alloys Joints Welded by Pulsed Laser Spot Welding

    NASA Astrophysics Data System (ADS)

    Cai, Chuang; Li, Liqun; Tao, Wang; Peng, Genchen; Wang, Xian

    2016-07-01

    Pulsed laser spot welding of intersection points of zirconium alloys straps was performed. Weld bead size, microstructure and the corrosion behavior of weld bead were investigated. With the increasing laser peak power or number of shots, the weld width of the beads increased, the protrusion decreased and the dimple increased with further increase in heat input. The fusion zone consisted of a mixture of αZr and residual βZr phases. After annealing treatment, βNb and Zr(Fe, Nb)2 second phase particles were precipitated inter- and intragranular of αZr grains adequately. The oxide thickness of annealed weld bead was about 3.90 μm, decreased by about 18.1% relative to the 4.76 μm of as-welded specimen corroded at 400 °C and 10.3 MPa for 20 days. The corrosion resistance of annealed specimen was better than that of as-welded specimen, since the second phase particles exerted better corrosion resistance, and the content of Nb in βZr and the fraction of βZr decreased after the annealing treatment.

  16. Fundamental Study of Material Flow in Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Reynolds, Anthony P.

    1999-01-01

    The presented research project consists of two major parts. First, the material flow in solid-state, friction stir, butt-welds as been investigated using a marker insert technique. Changes in material flow due to welding parameter as well as tool geometry variations have been examined for different materials. The method provides a semi-quantitative, three-dimensional view of the material transport in the welded zone. Second, a FSW process model has been developed. The fully coupled model is based on fluid mechanics; the solid-state material transport during welding is treated as a laminar, viscous flow of a non-Newtonian fluid past a rotating circular cylinder. The heat necessary for the material softening is generated by deformation of the material. As a first step, a two-dimensional model, which contains only the pin of the FSW tool, has been created to test the suitability of the modeling approach and to perform parametric studies of the boundary conditions. The material flow visualization experiments agree very well with the predicted flow field. Accordingly, material within the pin diameter is transported only in the rotation direction around the pin. Due to the simplifying assumptions inherent in the 2-D model, other experimental data such as forces on the pin, torque, and weld energy cannot be directly used for validation. However, the 2-D model predicts the same trends as shown in the experiments. The model also predicts a deviation from the "normal" material flow at certain combinations of welding parameters, suggesting a possible mechanism for the occurrence of some typical FSW defects. The next step has been the development of a three-dimensional process model. The simplified FSW tool has been designed as a flat shoulder rotating on the top of the workpiece and a rotating, cylindrical pin, which extends throughout the total height of the flow domain. The thermal boundary conditions at the tool and at the contact area to the backing plate have been varied

  17. Tool for Two Types of Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Carter, Robert

    2006-01-01

    A tool that would be useable in both conventional and self-reacting friction stir welding (FSW) has been proposed. The tool would embody both a prior tooling concept for self-reacting FSW and an auto-adjustable pin-tool (APT) capability developed previously as an augmentation for conventional FSW. Some definitions of terms are prerequisite to a meaningful description of the proposed tool. In conventional FSW, depicted in Figure 1, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a rotating pin that protrudes from the shoulder into the depth of the workpiece. The main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional FSW is augmented with an APT capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or force-control system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding (SR-FSW), there are two rotating shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft, back into the FSW machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. A tool for SRFSW embodying this concept was reported in "Mechanism for Self-Reacted Friction Stir Welding" (MFS-31914), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 53. In its outward appearance, the proposed tool (see Figure 2) would fit the above description of an SR

  18. Finite element based simulation on friction stud welding of metal matrix composites to steel

    NASA Astrophysics Data System (ADS)

    Hynes, N. Rajesh Jesudoss; Tharmaraj, R.; Velu, P. Shenbaga; Kumar, R.

    2016-05-01

    Friction welding is a solid state joining technique used for joining similar and dissimilar materials with high integrity. This new technique is being successfully applied to the aerospace, automobile, and ship building industries, and is attracting more and more research interest. The quality of Friction Stud Welded joints depends on the frictional heat generated at the interface. Hence, thermal analysis on friction stud welding of stainless steel (AISI 304) and aluminium silicon carbide (AlSiC) combination is carried out in the present work. In this study, numerical simulation is carried out using ANSYS software and the temperature profiles are predicted at various increments of time. The developed numerical model is found to be adequate to predict temperature distribution of friction stud weld aluminium silicon carbide/stainless steel joints.

  19. Radiographic detection of defects in friction stir welding on aluminum alloy AMg5M

    SciTech Connect

    Tarasov, Sergei Yu. Kolubaev, Evgeny A.; Rubtsov, Valery E.

    2014-11-14

    In order to reveal weld defects specific to friction stir welding we undertook radiographic inspection of AMg5M aluminum alloy welded joints. Weld defects in the form of voids have been revealed in the weld obtained under the non-optimal rotation and feed rate. Both shape and size of these defects have been confirmed by examining metallographically successive sections prepared in the weld plane as well as in the plane transversal to the tool feed direction. Linear defects have been also found in the sections that are not seen in the radiographic images. Both the preferable localization and origination of the defects have been analyzed.

  20. A Review on Inertia and Linear Friction Welding of Ni-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Chamanfar, Ahmad; Jahazi, Mohammad; Cormier, Jonathan

    2015-04-01

    Inertia and linear friction welding are being increasingly used for near-net-shape manufacturing of high-value materials in aerospace and power generation gas turbines because of providing a better quality joint and offering many advantages over conventional fusion welding and mechanical joining techniques. In this paper, the published works up-to-date on inertia and linear friction welding of Ni-based superalloys are reviewed with the objective to make clarifications on discrepancies and uncertainties reported in literature regarding issues related to these two friction welding processes as well as microstructure, texture, and mechanical properties of the Ni-based superalloy weldments. Initially, the chemical composition and microstructure of Ni-based superalloys that contribute to the quality of the joint are reviewed briefly. Then, problems related to fusion welding of these alloys are addressed with due consideration of inertia and linear friction welding as alternative techniques. The fundamentals of inertia and linear friction welding processes are analyzed next with emphasis on the bonding mechanisms and evolution of temperature and strain rate across the weld interface. Microstructural features, texture development, residual stresses, and mechanical properties of similar and dissimilar polycrystalline and single crystal Ni-based superalloy weldments are discussed next. Then, application of inertia and linear friction welding for joining Ni-based superalloys and related advantages over fusion welding, mechanical joining, and machining are explained briefly. Finally, present scientific and technological challenges facing inertia and linear friction welding of Ni-based superalloys including those related to modeling of these processes are addressed.

  1. Formation of Oxides in the Interior of Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Schneider, Judy; Chen, Po; Nunes, Arthur C., Jr.

    2016-01-01

    In friction stir welding (FSWing) the actual solid state joining takes place between the faying surfaces which form the weld seam. Thus the seam trace is often investigated for clues when the strength of the weld is reduced. Aluminum and its alloys are known to form a native, protective oxide on the surface. If these native surface oxides are not sufficiently broken up during the FSW process, they are reported to remain in the FSW interior and weaken the bond strength. This type of weld defect has been referred to as a lazy "S", lazy "Z", joint line defect, kissing bond, or residual oxide defect. Usually these defects are mitigated by modification of the process parameters, such as increased tool rotation rate, which causes a finer breakup of the native oxide particles. This study proposes that there may be an alternative mechanism for formation of oxides found within the weld nugget. As the oxidation rate increases at elevated temperatures above 400ºC, it may be possible for enhanced oxidation to occur on the interior surfaces during the FSW process from entrained air entering the seam gap. Normally, FSWs of aluminum alloys are made without a purge gas and it is unknown how process parameters and initial fit up could affect a potential air path into the interior during the processing. In addition, variations in FSW parameters, such as the tool rotation, are known to have a strong influence on the FSW temperature which may affect the oxidation rate if internal surfaces are exposed to entrained air. A series of FSWs were made in 3 different thickness panels of AA2219 (0.95, 1.27 and 1.56 cm) at 2 different weld pitches. As the thickness of the panels increased, there was an increased tendency for a gap to form in advance of the weld tool. If sufficient air is able to enter the workpiece gap prior to consolidation, the weld temperature can increase the oxidation rate on the interior surfaces. These oxidation rates would also be accelerated in areas of localized

  2. Analysis of ripple formation in single crystal spot welds

    SciTech Connect

    Rappaz, M.; Corrigan, D.; Boatner, L.A.

    1997-10-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 {micro}m) and spacing (typically {approximately} 60 {micro}m) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f{sub 0} given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v{sub s}/f{sub 0}, where v{sub s} is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  3. Metal cutting analogy for establishing Friction Stir Welding process parameters

    NASA Astrophysics Data System (ADS)

    Stafford, Sylvester Allen

    A friction stir weld (FSW) is a solid state joining operation whose processing parameters are currently determined by lengthy trial and error methods. To implement FSWing rapidly in various applications will require an approach for predicting process parameters based on the physics of the process. Based on hot working conditions for metals, a kinematic model has been proposed for calculating the shear strain and shear strain rates during the FSW process, validation of the proposed model with direct measuring is difficult however. Since the shear strain and shear strain rates predicted for the FSW process, are similar to those predicted in metal cutting, validation of the FSW algorithms with microstructural studies of metal chips may be possible leading to the ability to predict FSW processing parameters.

  4. Resistance spot welding of Ti-6A1-4V alloy

    SciTech Connect

    Jarboe, D.M.

    1980-06-01

    The effects of weld power, electrode force, electrode tip radius, and elapsed time between cleaning and welding on resistance spot welds in Ti-6Al-4V alloy were evaluated. The alloy is weldable by this technique, and a wide latitude can be taken in processing variables.

  5. Integrated thermal-microstructure model to predict the property gradients in resistance spot steel welds

    SciTech Connect

    Babu, S.S.; Riemer, B.W.; Santella, M.L.; Feng, Z.

    1998-11-01

    An integrated model approach was proposed for relating resistance welding parameters to weldment properties. An existing microstructure model was used to determine the microstructural and property gradients in resistance spot welds of plain carbon steel. The effect of these gradients on the weld integrity was evaluated with finite element analysis. Further modifications to this integrated thermal-microstructure model are discussed.

  6. Loading Considerations for Implementing Friction STIR Welding for Large Diameter Tank Fabrication

    NASA Technical Reports Server (NTRS)

    Adams, Glynn

    1998-01-01

    The main objectives of the research presented here are to determine the reaction loads associated with friction stir welding (FSW) and to determine the suitability of an existing welding fixture for implementing this welding process in the fabrication of large diameter tanks. Friction stir welding is a relatively new process which is being investigated as a method for joining aluminum alloys. The aluminum-lithium alloy, Al-Li 2195, which is being used to fabricate the super-light-weight shuttle external tank has proven difficult to join using fusion techniques. Therefore, FSW and its potential applicability to joining Al-Li 2195 are of particular interest to NASA.

  7. Thermal analysis of friction welding process in relation to the welding of YSZ-alumina composite and 6061 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Uday, M. B.; Fauzi, M. N. Ahmad; Zuhailawati, H.; Ismail, A. B.

    2012-08-01

    The objective of this work is to establish an analytical data for heat generation by friction welding, based on different parameters of the contact condition between two dissimilar materials. The ceramic composite of Al2O3-YSZ and 6061 Al alloy, which is the example of joining materials by friction welding was used in the experiments. Alumina rods containing 0, 25 and 50 wt% yttria stabilized zirconia were produced by slip casting in Plaster of Paris molds and subsequently sintered at 1600 °C. The diameter of both the ceramic and metal rods was 16 mm. Rotational speeds for friction welding were between 630 and 2500 rpm. As a result, different data was evaluated for obtaining joint properties and operating conditions, and obtained results are useful in modeling the welding process and reliability joint under various conditions.

  8. Ultrasonic test of resistance spot welds based on wavelet package analysis.

    PubMed

    Liu, Jing; Xu, Guocheng; Gu, Xiaopeng; Zhou, Guanghao

    2015-02-01

    In this paper, ultrasonic test of spot welds for stainless steel sheets has been studied. It is indicated that traditional ultrasonic signal analysis in either time domain or frequency domain remains inadequate to evaluate the nugget diameter of spot welds. However, the method based on wavelet package analysis in time-frequency domain can easily distinguish the nugget from the corona bond by extracting high-frequency signals in different positions of spot welds, thereby quantitatively evaluating the nugget diameter. The results of ultrasonic test fit the actual measured value well. Mean value of normal distribution of error statistics is 0.00187, and the standard deviation is 0.1392. Furthermore, the quality of spot welds was evaluated, and it is showed ultrasonic nondestructive test based on wavelet packet analysis can be used to evaluate the quality of spot welds, and it is more reliable than single tensile destructive test. PMID:25454096

  9. Laser Welded versus Resistance Spot Welded Bone Implants: Analysis of the Thermal Increase and Strength

    PubMed Central

    Fornaini, Carlo; Meleti, Marco; Bonanini, Mauro; Lagori, Giuseppe; Vescovi, Paolo; Merigo, Elisabetta; Nammour, Samir

    2014-01-01

    Introduction. The first aim of this “ex vivo split mouth” study was to compare the thermal elevation during the welding process of titanium bars to titanium implants inserted in pig jaws by a thermal camera and two thermocouples. The second aim was to compare the strength of the joints by a traction test with a dynamometer. Materials and Methods. Six pigs' jaws were used and three implants were placed on each side of them for a total of 36 fixtures. Twelve bars were connected to the abutments (each bar on three implants) by using, on one side, laser welding and, on the other, resistance spot welding. Temperature variations were recorded by thermocouples and by thermal camera while the strength of the welded joint was analyzed by a traction test. Results. For increasing temperature, means were 36.83 and 37.06, standard deviations 1.234 and 1.187, and P value 0.5763 (not significant). For traction test, means were 195.5 and 159.4, standard deviations 2.00 and 2.254, and P value 0.0001 (very significant). Conclusion. Laser welding was demonstrated to be able to connect titanium implant abutments without the risk of thermal increase into the bone and with good results in terms of mechanical strength. PMID:25110731

  10. Processing-Microstructure Relationships in Friction Stir Welding of MA956 Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Baker, Bradford W.; Menon, E. Sarath K.; McNelley, Terry R.; Brewer, Luke N.; El-Dasher, Bassem; Farmer, Joseph C.; Torres, Sharon G.; Mahoney, Murray W.; Sanderson, Samuel

    2014-12-01

    A comprehensive set of processing-microstructure relationships is presented for friction stir welded oxide dispersion strengthened MA956 steel. Eight rotational speed/traverse speed combinations were used to produce friction stir welds on MA956 plates using a polycrystalline cubic boron nitride tool. Weld conditions with high thermal input produced defect-free, full-penetration welds. Electron backscatter diffraction results showed a significant increase in grain size, a persistent body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone sensitive to weld parameters. Micro-indentation showed an asymmetric reduction in hardness across a transverse section of the weld. This gradient in hardness was greatly increased with higher heat inputs. The decrease in hardness after welding correlates directly with the increase in grain size and may be explained with a Hall-Petch type relationship.