Joining of Advanced and Specialty Materials XXI: Friction and Friction Stir Welding II / Welding Proceses
Program Organizers: Mathieu Brochu, McGill University; Anming Hu, University of Tennessee; Hiroaki Mori, Osaka University; Yuri Hovanski, Brigham Young University; Darren Barborak, WeldQC inc; Akio Hirose, Osaka University; Peng He, Harbin Institute of Technology; Zhiyong Gu, University of Massachusetts Lowell; Zhenzhen Yu, Colorado School of Mines

Monday 2:00 PM
September 30, 2019
Room: Portland Ballroom 252
Location: Oregon Convention Center

Session Chair: Judy Schneider, University of Alabama at Huntsville; Carolin Fink, Ohio State University

2:00 PM  
Thermal Modeling of Continuous Drive Friction Welding for Al6061: Mohammed Tashkandi1; 1Northern Border University
    Continuous Drive Friction Welding is a solid-state joining technique used to weld similar and dissimilar materials. The study aims at exploring the process of CDFW of Al6061 alloys and its thermal profile through modeling and experimental validation. Comsol Multyphysics® was used to simulate the welding phenomenon by utilizing the heat transfer and structure dynamics models while incorporating the phase change of the material during the welding process. The results showed that the model was adequate and reliable as far as the maximum welding temperature is concerned; although some misalignment was observed in the heating part of the curve that was explained by the mechanism of the flash formation. The location at which the temperature was measured at the contact surface changes during the experiments while stays constant during modeling and hence the differences among the model and the experiment.

2:20 PM  
Reducing Cycle Time of Refill Friction Stir Spot Welding: Yuri Hovanski1; Brigham Larsen1; Arnold Wright1; Michael Miles1; 1Brigham Young University
    With much more complicated motion than the traditional friction stir spot welding, refill friction stir spot welding originally published cycle times of ten seconds. With more than a decade of development, and significant refinement of both tooling and machinery it is now possible to reduce weld cycle times below one second. We show the process loads required to refill friction stir spot weld in less than one second, and demonstrate how linking process kinematics to a 2-D axisymmetric finite element model enabled further refinement of the process. Welding was performed in numerous automotive aluminum alloys, demonstrating the ability to use solid-state spot joining for automotive aluminum assembly.

2:40 PM  
Material Properties of Friction Stir Spot Welded Joint of Steel and Heat-treatable Aluminum Alloys: Kun Gao1; Mounarik Mondal1; Hrishikesh Das1; Mi Na Jeong1; Sung-Tae Hong1; 1University of Ulsan
    Friction stir spot welding (FSSW) of aluminum alloys and steel is conducted with an offset of a tool toward the steel side. The microstructure of FSSW joint is characterized using scanning electron microscopy and electron back scattered diffraction analysis. The mechanical property of joints is evaluated by microhardness measurements. The result of the microstructural analysis shows successful formation of FSSW joint. However, intermetallics are also observed in the stir zone, which may affect the strength of the joint.

3:00 PM  
Joining of Magnesium to Carbon Fiber Reinforced Polymers using Friction Stir Interlocking technique: Tianhao Wang1; Piyush Upadhyay1; Scott Whalen1; Keerti Kappagantula1; 1Pacific Northwest National Laboratory
    Requirements to reduce fuel consumption and carbon dioxide release in the automobile industry necessitate the use of lightweight structural materials such as magnesium alloys and carbon fiber reinforced polymers (CFRP). Magnesium alloys have the lowest density among all the structural alloys; CFRP possess even higher strength-to-weight ratio comparatively. A mechanically reliable joint between magnesium alloys and CFRP can decrease vehicle weight and boost design flexibility in the automotive industry. However, joining between metals and polymers is challenging due to the large differences in their physical, chemical, and mechanical properties. Friction Stir Interlocking technique was developed to fabricate joints between magnesium and CFRP by introducing pre-machined interlocking features made of magnesium inserts, while minimizing polymer degradation. Design of interlocking parts and welding tools were optimized. In addition, mechanical properties of welded joints were evaluated with different test methods.

3:20 PM  
Joining of Carbon Fiber Reinforced Composites to AZ31B using Friction Self-piercing Riveting: Yong Chae Lim1; Charles Warren1; Jian Chen1; Jiheon Jun1; Zhili Feng1; 1Oak Ridge National Laboratory
    Multi-materials autobody concept using high specific strength materials has been focused for automotive industries to improve fuel efficiency while maintaining safety and performance requirements. However, joining of such dissimilar materials poses a technical barrier to enable and widespread of lightweight vehicle structures. In the present work, friction self-piercing riveting (F-SPR) that is a unique solid-state joining process was applied for joining of carbon fiber composites to AZ31B. One particular issue of magnesium alloy is a low ductility at room temperature. This cracking issue can be avoided by the localized frictional heat generated between the rotating rivet and underneath sheet. Joint integrity was evaluated by lap shear tensile and cross tension testing. The joint interface from the cross-sectioned F-SPR specimen was evaluated by optical and electron microscopy techniques. Salt spray testing according to ASTM B117 specification was used to access an initial corrosion performance of F-SPR specimens.

3:40 PM Break

4:00 PM  
Machine Learning Application for Active Exploration of Weld Sequence Scenarios: Mahyar Asadi1; Mohammad Mohseni1; Majid Tanbakuei Kashani1; Michael Fernandez1; Mathew Smith1; 1SKC Engineering (An Applus Company)
    Distortion is a common problem in welded structures, and the process of finding an effective weld sequence to mitigate the distortion is a challenging task given a large number of possible combinations. Despite efficient simulation tools and powerful supercomputers, yet simulation tools have been limited by CPU time to optimize a welding sequence and therefore not mature for practical designs. To this end, we constructed and integrated machine learning (ML) algorithms with the simulation capability. These ML models were then trained to increase the fidelity by a wisely chosen training-set of simulation to construct a meta-model for active exploration of various weld sequence scenarios in real time. As opposed to existing ML algorithms that require an extensive data set to train, our algorithm picks relatively small training-set to construct a meta-model. We present an example of our algorithm implemented in a real welded structure project.

4:20 PM  
Theoretical Analysis of Keyhole Dynamics Based on Calculation of Coupled Multiphase Transfer during Laser Beam Welding for Aluminum: Hiroaki Mori1; Qiaofeng Zhou1; Fumikazu Miyasaka1; 1Osaka University
    In order to clarify the mechanism of porosity formation during Laser beam welding (LBW) process, the fluid dynamics and molten pools were modeled using an original coupled phase transfer method and an adaptive heat source model was proposed for the absorption of laser beams into the molten metal. As using the developed calculation code, factors considered in the simulations include buoyancy force, Marangoni force and recoil pressure; furthermore, the models can also lead to the phenomenon of keyhole collapse. Models to calculate the shear stress on the keyhole surface and of the heat transfer into the molten pool via a plasma plume are introduced. As compared with the calculated bubbles’ formation and in-situ observation of bubble formed during LBW, the calculation was in good agreement with experimental results. Therefore, it suggested that the developed simulation method can be useful technique to predict the formation of porosity during LBW.

4:40 PM  
The Effects of Pre-pulse & Profile Force on Nugget Growth and Weldability for Resistance Spot Welding of A6014 Alloy: Changwook Ji1; Joo-Yong Cheon1; Jae-Hoon Kim1; Jun Hyun Uk1; 1Korea Institute of Industrial Technology
    This research presents a comparative study of nugget growth and weldability with pre-pulse and profile force welding condition in RSW(Resistance Spot Welding) for Al 6014 alloy. The previous studies have investigated that there is a standard welding condition including pre-heating in RSW for Al alloy. However, the welding conditions of only pre-heating in RSW on Al alloy have different guidelines by administrator of manufacturing automotive company. Also, there are many problems for the Al alloy RSW. Especially, wear and degradation of electrode tip and outermost layer such as oxide layer has been made decrease welding quality during welding. In this study, resistance spot weldability was explored by investigating the effects of pre-pulse and profile force welding condition on elimination Al2O3 layer on surface and nugget formation and growth during RSW.

5:00 PM  
Investigations on Welding Characteristics of Additively Manufactured Ti6Al4V and SS304: Timothy Pasang1; Sreenidhi Roshinkumar1; Zainab Manasawala1; Jia-Chang Wang2; Cho-Pei Jiang2; Alex Kirchner3; 1Auckland Technical University; 2National Taipei University of Technology; 3Fraunhofer - Institute for Advanced Materials
     Additive Manufacturing (AM) has attracted a great interest to many industries, namely, aerospace, biomedical, and automotive. AM enable to produce intricate designs, economising manufacturing. However, AM methods are constrained to long build times and relatively small-size parts. One way around this is to print small components follow by welding.The aim of this study was to analyse the weldability of additively manufactured Ti6Al4V and SS304. The coupons were manufactured using Selective Electron Beam Melting (SEBM) followed by welding using Gas Tungsten Arc Welding (GTAW). Microscopy examination revealed martensite structure in the fusion zone (FZ) of Ti6Al4V that increased its strength (hardness). Hardness of SS304 deceased at the fusion zone (FZ). Following tensile testing, it was revealed that fractured took place in the heat affected zone (HAZ) for Ti6Al4V and in the FZ for SS304, and both showed dimple fracture mechanism.