Browsing by Author "dos Santos, Jorge F."

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  • Fundamentals of force-controlled friction riveting: Part I-joint formation and heat development
    (2018-11-15) Cipriano, Gonçalo Pina; Blaga, Lucian A.; dos Santos, Jorge F.; Vilaça, Pedro; Amancio-Filho, Sergio T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This work presents a systematic study on the correlations between process parameters and rivet plastic deformation, produced by force-controlled friction riveting. The 5 mm diameter AA2024 rivets were joined to 13 mm, nominal thickness, polyetherimide plates. A wide range of joint formations was obtained, reflecting the variation in total energy input (24-208 J) and process temperature (319-501 °C). The influence of the process parameters on joint formation was determined, using a central composite design and response surface methodology. Friction time displayed the highest contribution on both rivet penetration (61.9%) and anchoring depth (34.7%), and friction force on the maximum width of the deformed rivet tip (46.5%). Quadratic effects and two-way interactions were significant on rivet anchoring depth (29.8 and 20.8%, respectively). Bell-shaped rivet plastic deformation-high mechanical interlocking-results from moderate energy inputs (~100 J). These geometries are characterized by: rivet penetration depth of 7 to 9 mm; maximum width of the deformed rivet tip of 9 to 12 mm; and anchoring depth higher than 6 mm. This knowledge allows the production of optimized friction-riveted connections and a deeper understanding of the joining mechanisms, further discussed in Part II of this work.
  • Fundamentals of force-controlled friction riveting: Part II-Joint global mechanical performance and energy efficiency
    (2018-12-07) Cipriano, Gonçalo Pina; Blaga, Lucian A.; dos Santos, Jorge F.; Vilaça, Pedro; Amancio-Filho, Sergio T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The present work investigates the correlation between energy efficiency and global mechanical performance of hybrid aluminum alloy AA2024 (polyetherimide joints), produced by force-controlled friction riveting. The combinations of parameters followed a central composite design of experiments. Joint formation was correlated with mechanical performance via a volumetric ratio (0.28-0.66 a.u.), with a proposed improvement yielding higher accuracy. Global mechanical performance and ultimate tensile force varied considerably across the range of parameters (1096-9668 N). An energy efficiency threshold was established at 90 J, until which, energy input displayed good linear correlations with volumetric ratio and mechanical performance (R-sq of 0.87 and 0.86, respectively). Additional energy did not significantly contribute toward increasing mechanical performance. Friction parameters (i.e., force and time) displayed the most significant contributions to mechanical performance (32.0% and 21.4%, respectively), given their effects on heat development. For the investigated ranges, forging parameters did not have a significant contribution. A correlation between friction parameters was established to maximize mechanical response while minimizing energy usage. The knowledge from Parts I and II of this investigation allows the production of friction riveted connections in an energy efficient manner and control optimization approach, introduced for the first time in friction riveting.
  • Single-phase friction riveting: metallic rivet deformation, temperature evolution, and joint mechanical performance
    (2020-01-01) Pina Cipriano, Gonçalo; Ahiya, Aakash; dos Santos, Jorge F.; Vilaça, Pedro; Amancio-Filho, Sergio T.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The present work explores the feasibility of single-phase friction riveting on unreinforced thermoplastics. In single phase, the load is kept constant throughout the process, avoiding the forging phase with higher axial force, used in the conventional process. This process variant can constitute an answer when payload restrictions exist. The results demonstrate the feasibility of single-phase friction riveting on unreinforced polyetherimide plates joined by AA2024 rivets with 5 mm of diameter. A Box-Behnken design of experiments and analysis of variance were used to set parameter matrix and understand the correlations between parameters and joint properties. A large variation of the mechanical energy input was observed (151–529 J). Over-deformation and material rupture were observed in higher energy conditions. Lower energy input yielded a bell-shaped rivet plastic deformation, corresponding to the best performance. The maximum process temperatures varied between 461 and 509 °C. This friction riveting process variant allowed a considerable high mechanical strength to be achieved, with ultimate tensile force of 7486 N, comparable with the two-phase friction riveting process, albeit applying lower axial forces, such as 2400 N. Within the investigated conditions, this study proves the feasibility of the single-phase process, achieving good global mechanical performance and energetically efficient conditions, without forging phase.