State-of-the-art Review of Springback Behavior of Polymers
DOI:
https://doi.org/10.31181/smeor11202423Keywords:
Metal-polymer sandwich, Springback, Metal-polymer laminates, Punch radius, Fiber Metal LaminatesAbstract
The spring-in and spring-back behavior of polymers is intricate and influenced by various process parameters and mechanisms, including interply slip, anisotropic thermal expansion, and crystallization, all of which can lead to residual stresses. Composite materials made of metal and polymer are being investigated by researchers as a promising alternative to monometallic materials due to their superior properties. However, the number of studies related to metal/polymer/metal laminates on the same topics is relatively limited. A comprehensive review study was carried out with a focus on research works that were conducted with the consideration of different process parameters, such as radius of die and punch, friction, and force applied by blank holder, in order to observe their impact on the springback behavior of polymers. Springback on polymer components depends on the accuracy of appropriate materials and the consideration of appropriate experimental strategies. However, due to their viscoelastic properties, polymers demonstrate distinctive springback behavior. Furthermore, when subjected to deformation, polymers experience a combination of elastic and viscous responses, resulting in immediate elastic recovery and time-dependent viscoelastic relaxation. This intricate behavior presents difficulties in precisely forecasting and managing springback. To enhance the control and optimization of springback in polymer-based manufacturing processes, it is essential to improve the understanding of polymer behavior under diverse loading conditions and to refine simulation techniques accordingly. This review focuses on springback prediction models specific to polymers.
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Miller, W. K. (1980). Metal-Plastic laminates for vehicle weight reduction. SAE Transactions, 481–490.
Yang, B., Nunez, S. W., Welch, T. E., & Schwaegler, J. R. (2001). Laminate dash ford taurus noise and vibration performance. SAE Technical Paper.
Reda, R. (2019). Equal Channel Angular Pressing (ECAP): Die Design, Processing Handicaps and Mechanical Characterization. Evol. Mech. Eng, 2(5).
Harris, B. (1991). A perspective view of composite materials development. Materials & Design, 12(5), 259–272.
Huang, Y.-M., & Leu, D.-K. (1995). Finite-element simulation of the bending process of steel/polymer/steel laminate sheets. Journal of materials processing technology, 52(2–4), 319–337.
Reddy, P., Padhy, C. P., & Janaki Ramulu, P. (2024). AA5052-PVC-AA5052 (Al-PVC-Al) Sandwich Sheets Forming Analysis through In-Plane Plane Stretching Tests. The Scientific World Journal, 2024.
Yang, J., Han, S., & Yu, W.-R. (2023). Detection of delamination of steel–polymer sandwich composites using acoustic emission and development of a forming limit diagram considering delamination. Heliyon, 9(6).
Colombo, C., Carradó, A., Palkowski, H., & Vergani, L. (2015). Impact behaviour of 3-layered metal-polymer-metal sandwich panels. Composite structures, 133, 140–147.
Carradò, A., & Ravindra, N. M. (2023). Metal/Polymer/Metal Sandwich Systems: An Overview. JOM, 75(12), 5126–5140.
Kirubakaran, R., Kaliyamoorthy, R., Munusamy, R., & Annamalai, B. (2023). Mechanical and vibration behavior of surface‐modified titanium sheet interleaved with woven basalt/flax fiber metal laminates. Polymer Composites, 44(12), 8442–8453.
Asundi, A., & Choi, A. Y. N. (1997). Fiber metal laminates: an advanced material for future aircraft. Journal of Materials processing technology, 63(1–3), 384–394.
Vogelesang, L. B., & Vlot, Ajj. (2000). Development of fibre metal laminates for advanced aerospace structures. Journal of materials processing technology, 103(1), 1–5.
Vlot, A., & Krull, M. (1997). Impact damage resistance of various fibre metal laminates. Le Journal de Physique IV, 7(C3), C3-1045.
Kim, K. J., Rhee, M. H., Choi, B.-I., Kim, C.-W., Sung, C.-W., Han, C.-P., … Won, S.-T. (2009). Development of application technique of aluminum sandwich sheets for automotive hood. International Journal of Precision Engineering and Manufacturing, 10, 71–75.
Carradò, A., Faerber, J., Niemeyer, S., Ziegmann, G., & Palkowski, H. (2011). Metal/polymer/metal hybrid systems: Towards potential formability applications. Composite Structures, 93(2), 715–721.
Paudel, P., Dulal, S., Bhandari, M., & Tomar, A. (2016). Study on pre-fabricated modular and steel structures. International Journal of Civil Engineering (SSRG-IJCE), 3(5).
Shawkat, W., Honickman, H., & Fam, A. (2008). Investigation of a novel composite cladding wall panel in flexure. Journal of composite materials, 42(3), 315–330.
Miranda, S. S., Santos, A. D., Amaral, R. L., & Malheiro, L. T. (2019). Experimental and numerical analysis of springback and bending behavior of a composite sandwich metal-polymer material. In AIP Conference proceedings (Vol. 2113, p. 20020). AIP Publishing LLC.
Weiss, M., Rolfe, B., Dingle, M., & Hodgson, P. (2004). The influence of interlayer thickness and properties on spring-back of SPS-(steel/polymer/steel) laminates. Steel Grips, 2, 445–449.
Jain, P. S., Kagzi, S. A., Patel, S., & Vasava, J. (2021). An analysis of the effect of various parameters on surface roughness, springback and thinning while performing single point incremental forming on polypropylene sheet. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, 09544089211047203.
Shahi, K., & Ramachandran, V. (2022). Theoretical and experimental investigation of shape memory polymers programmed below glass transition temperature. Polymers, 14(13), 2753.
Zhu, P., Lin, J., Xiao, R., & Zhou, H. (2022). Unravelling physical origin of the Bauschinger effect in glassy polymers. Journal of the Mechanics and Physics of Solids, 168, 105046.
Wang, B., Chang, Y., Zang, S., Li, X., Yu, S., & Wang, C. (2023). Effect of complicated deformation behaviors during cold stamping on springback prediction of DP980 steel. The International Journal of Advanced Manufacturing Technology, 1–19.
Díaz, R., Nguyen, K., Montáns, F. J., & Sánz, M. A. (2022). Analysis of springback of aluminum and high-strength steels through a new large strain anisotropic elastoplastic formulation based on elastic corrector rates. International Journal of Material Forming, 15(4), 52.
Abhyankar, H., Webb, D. P., West, G. D., & Hutt, D. A. (2020). Characterization of metal‐polymer interaction forces by AFM for insert molding applications. Polymer Engineering & Science, 60(12), 3036–3045.
Sharma, P. K., Gautam, V., & Agrawal, A. K. (2021). Experimental and numerical investigations of springback and residual stresses in bending of a three-ply clad sheet. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 235(12), 2823–2838.
Cong, H., Zhao, M., Zhang, J., & Liu, Y. (2023). Design and mechanical analysis of shear thickening fluid/polyurethane composite sandwich. In MATEC Web of Conferences (Vol. 380, p. 1030). EDP Sciences.
Gomez, A., Barbero, E., & Sanchez-Saez, S. (2022). Modelling of carbon/epoxy sandwich panels with agglomerated cork core subjected to impact loads. International Journal of Impact Engineering, 159, 104047.
Wang, M., Cai, Z., Zhang, X., Gao, J., & Zhang, W. (2022). A universal elastoplastic equivalent method for sandwich panels and its application in plastic forming. Thin-Walled Structures, 181, 110114.
Zhang, Y., Chen, Q., Wang, M., Zhang, X., & Cai, Z. (2021). Plastic Forming of Sandwich Panels and Numerical Analyses of the Forming Processes Based on Elastoplastic Equivalent Model. Materials, 14(17), 4955.
Vo, T. M., Poulsen, J. G., Palmer, A. R., & Stallbaumer, L. D. (2019). Experimental Investigation of Spring-back Behavior of Composite Sandwich Structures: Part One. SAMPE 2019-Charlotte, NC, May 2019.
Tiwari, R., & Garcia, E. (2011). The state of understanding of ionic polymer metal composite architecture: a review. Smart Materials and Structures, 20(8), 83001. https://doi.org/10.1088/0964-1726/20/8/083001
Mallakpour, S., Radfar, Z., & Hussain, C. M. (2021). Current advances on polymer-layered double hydroxides/metal oxides nanocomposites and bionanocomposites: Fabrications and applications in the textile industry and nanofibers. Applied Clay Science, 206, 106054.
Zhang, R., & Pang, H. (2021). Application of graphene-metal/conductive polymer based composites in supercapacitors✰. Journal of Energy Storage, 33, 102037.
Gupta, A. K., Bafna, M., Srivastava, S., Khanna, R. K., & Vijay, Y. K. (2021). Study of electromagnetic shielding effectiveness of metal oxide polymer composite in their bulk and layered forms. Environmental Science and Pollution Research, 28(4), 3880–3887.
Shin, K. S., Kim, K. J., Choi, S.-W., & Rhee, M. H. (1999). Mechanical properties of aluminum/polypropylene/aluminum sandwich sheets. Metals and Materials, 5, 613–618.
Weiss, M., Dingle, M. E., Rolfe, B. F., & Hodgson, P. D. (2007). The influence of temperature on the forming behavior of metal/polymer laminates in sheet metal forming.
Jafaria, P. S., Hashemi, R., Kazemi, F., & Kaleybar, S. P. (n.d.). An experimental investigation of mechanical properties, forming limit curves, and bending behavior of aluminum-polymer sandwich composites.
Kella, C. K., & Mallick, P. (2023). Formability Analysis of Aluminum-Aluminum and AA5182/Polypropylene/AA5182 Laminates. SAE Technical Paper.
Parsa, M. H., Mohammadi, S. V, & Aghchai, A. J. (2014). Al3105/polypropylene/Al3105 laminates springback in V-die bending. The International Journal of Advanced Manufacturing Technology, 75, 849–860.
Liu, L., & Wang, J. (2004). Modeling springback of metal-polymer-metal laminates. J. Manuf. Sci. Eng., 126(3), 599–604.
Samuel, M. (2000). Experimental and numerical prediction of springback and side wall curl in U-bendings of anisotropic sheet metals. Journal of Materials Processing Technology, 105(3), 382–393.
Zhang, D., Cui, Z., Ruan, X., & Li, Y. (2007). An analytical model for predicting springback and side wall curl of sheet after U-bending. Computational Materials Science, 38(4), 707–715.
Liao, J., Zhou, S., & Xue, X. (2022). Twist springback and microstructure analysis of PEEK sheets in ultrasonic-assisted thermal incremental forming. The International Journal of Advanced Manufacturing Technology, 121(7–8), 5269–5282.
Xu, W., Zhang, B., Zhang, Z., & Yang, L. (2019). Experimental Study of Springback (Side-Wall-Curl) of Sheet Metal based on the DBS System. SAE Technical Paper.
Lawanwong, K., Hamasaki, H., Hino, R., & Yoshida, F. (2020). Double-action bending for eliminating springback in hat-shaped bending of advanced high-strength steel sheet. The International Journal of Advanced Manufacturing Technology, 106, 1855–1867.
Pritima, D., Veerappan, G., Patel, V. D., & Parthasarathy, N. R. (2022). Analysis of spring back behaviour during bending of AISI 1045 sheet metal. Materials Today: Proceedings, 59, 1575–1580.
Wang, C., Wang, S., Wang, S., Chen, G., & Zhang, P. (2019). Investigation on springback behavior of Cu/Ni clad foils during flexible die micro V-bending process. Metals, 9(8), 892.
Aminanda, Y., Legowo, A., & bin Mohd Nasir, M. N. (2019). The Effect of Curvature and Layup of Aircraft Type CFRP Laminate on the Springback After Curing Process. In 2019 Advances in Science and Engineering Technology International Conferences (ASET) (pp. 1–5). IEEE.
Lu, Y., Li, Y., Zhang, Y., & Dong, L. (2022). Manufacture of Al/CF/PEEK curved beams by hot stamping forming process. Materials and Manufacturing Processes, 37(14), 1597–1609.
Chanda, A., Dutta, S., & Bhattacharyya, D. (2020). Shape conformance via spring-back control during thermo-forming of veneer plywood into a channel section. Materials and Manufacturing Processes, 35(7), 859–868.
Wang, C., Yu, G., Zhao, J., & Liu, W. (2022). Pure-Bend and Over-Bend Straightening Theory for In-Plane Curved Beams with Symmetrical Section and Straightening Mechanism Analysis. Metals, 12(8), 1362.
Meng, Q., Zhai, R., Zhang, Y., Fu, P., & Zhao, J. (2022). Analysis of springback for multiple bending considering nonlinear unloading-reloading behavior, stress inheritance and Bauschinger effect. Journal of Materials Processing Technology, 307, 117657.
Meng, Q., Zhao, J., Mu, Z., Zhai, R., & Yu, G. (2022). Springback prediction of multiple reciprocating bending based on different hardening models. Journal of Manufacturing Processes, 76, 251–263.
Xu, Z., Qiu, D., Shahzamanian, M. M., Zhou, Z., Mei, D., & Peng, L. (2023). An improved springback model considering the transverse stress in microforming. International Journal of Mechanical Sciences, 241, 107947.
Zhang, H., & Hu, Y. (2022). Research on the axial elongation and springback law of thick-walled tubes in cold bending forming. The International Journal of Advanced Manufacturing Technology, 120(1–2), 669–689.
Alexandrov, S., Rynkovskaya, M., & Hwang, Y.-M. (2022). Ideal Flow Design of Plane-Strain Bending Driven by Springback. Processes, 10(8), 1601.
Zhang, M., Tian, X., & Wang, G. (2022). Residual stress analysis and its effect on springback for multi-step pressbrake bending. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 09544054221139551.
Farhadi, A., Hosseini-Hooshyar, A., & Nayebi, A. (2023). Springback Investigation of a Thick-Walled Tube Under Combined Torsion-Bending and Internal Pressure by Using Continuum Damage Mechanics. International Journal of Precision Engineering and Manufacturing, 1–12.
Wei, B., Wei, Y., Zhang, F., He, K., Dang, X., & Du, R. (2021). Springback control and plastic deformation of metal plates with large curvature in heat-assisted incremental bending process. The International Journal of Advanced Manufacturing Technology, 112, 1483–1500.
Lin, C., Chu, G., Sun, L., Chen, G., Liu, P., & Sun, W. (2021). Radial hydro-forging bending: a novel method to reduce the springback of AHSS tubular component. International Journal of Machine Tools and Manufacture, 160, 103650.
Ma, R., Ma, C., Zhai, R., & Zhao, J. (2022). Research on Control Technology of Variable Curvature Bending Springback Based on Iterative Compensation Method. International Journal of Precision Engineering and Manufacturing, 23(5), 489–501.
Cui, X., Du, Z., Xiao, A., Yan, Z., Qiu, D., Yu, H., & Chen, B. (2021). Electromagnetic partitioning forming and springback control in the fabrication of curved parts. Journal of Materials Processing Technology, 288, 116889.
Wasif, M., Iqbal, S. A., Tufail, M., & Karim, H. (2020). Experimental analysis and prediction of springback in v-bending process of high-tensile strength steels. Transactions of the Indian institute of metals, 73, 285–300.
Zhang, S., Fu, M., Wang, Z., Fang, D., Lin, W., & Zhou, H. (2021). Springback prediction model and its compensation method for the variable curvature metal tube bending forming. The International Journal of Advanced Manufacturing Technology, 112, 3151–3165.
Ma, J., & Welo, T. (2021). Analytical springback assessment in flexible stretch bending of complex shapes. International Journal of Machine Tools and Manufacture, 160, 103653.
Pérez Caro, L., Odenberger, E.-L., Schill, M., Niklasson, F., Åkerfeldt, P., & Oldenburg, M. (2021). Springback prediction and validation in hot forming of a double-curved component in alloy 718. International Journal of Material Forming, 1–19.
Yue, T., & Liu, C. (2020). A springback prediction method for double-curved plate bent with the multi-point forming method. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 234(12), 1939–1952.
Liu, C., Li, M., & Yue, T. (2021). Springback prediction method for double-curved workpiece considering plate anisotropy in multi-point forming. Journal of Mechanical Science and Technology, 35(6), 2623–2636.
Liu, P., Zhang, T., Guo, B., Yang, L., Shan, D., & Zong, Y. (2019). Deformation path and springback behavior in double-curved bending at high temperature. Journal of Mechanical Science and Technology, 33, 4361–4370.
Naik, R. K., Panda, S. K., & Racherla, V. (2022). Failure analysis of metal-polymer-metal sandwich panels with wire mesh interlayers: Finite element modeling and experimental validation. Composite Structures, 280, 114813.
Murzin, S. P., Palkowski, H., Melnikov, A. A., & Blokhin, M. V. (2022). Laser welding of metal-polymer-metal sandwich panels. Metals, 12(2), 256.
Andersson, A. (2005). Numerical and experimental evaluation of springback in a front side member. Journal of Materials Processing Technology, 169(3), 352–356.
Richter, J., Kuhtz, M., Hornig, A., Harhash, M., Palkowski, H., & Gude, M. (2021). A mixed numerical-experimental method to characterize metal-polymer interfaces for crash applications. Metals, 11(5), 818.
Link, T. M. (2001). Formability and performance of steel-plastic-steel laminated sheet materials. SAE transactions, 48–55.
Mosse, L., Compston, P., Cantwell, W. J., Cardew-Hall, M., & Kalyanasundaram, S. (2005). The effect of process temperature on the formability of polypropylene based fibre–metal laminates. composites part a: applied science and manufacturing, 36(8), 1158–1166.
Zhou, X., Zhao, Y., Chen, X., Liu, Z., Li, J., & Fan, Y. (2021). Fabrication and mechanical properties of novel CFRP/Mg alloy hybrid laminates with enhanced interface adhesion. Materials & Design, 197, 109251.
Zhu, W., Xiao, H., Wang, J., & Li, X. (2021). Effect of coupling agent quantity on composite interface structure and properties of fiber metal laminates. Polymer Composites, 42(7), 3195–3205.
Tekkaya, A. E., Hahn, M., Hiegemann, L., Weddeling, C., & Khalifa, N. Ben. (2015). Umformen faserverstärkter thermoplastischer Kunststoff-Halbzeuge mit metallischen Deckblechen für den Leichtbau. In Proceedings of (Vol. 35, pp. 185–199).
Rajabi, A., Kadkhodayan, M., Hirt, G., & Tekkaya, A. E. (2011). An experimental and numerical investigation of wrinkling in deep drawing of fiber-metal laminates. In 10th International Conference on Technology of Plasticity, ICTP (pp. 438–443).
Mosse, L., Compston, P., Cantwell, W. J., Cardew-Hall, M., & Kalyanasundaram, S. (2006). Stamp forming of polypropylene based fibre–metal laminates: the effect of process variables on formability. Journal of Materials Processing Technology, 172(2), 163–168.
Nikhare, C. P. (2017). Springback analysis in bilayer material bending. In ASME International Mechanical Engineering Congress and Exposition (Vol. 58356, p. V002T02A062). American Society of Mechanical Engineers.
Kim, K. J., Kim, D., Choi, S. H., Chung, K., Shin, K. S., Barlat, F., … Youn, J. R. (2003). Formability of AA5182/polypropylene/AA5182 sandwich sheets. Journal of Materials Processing Technology, 139(1–3), 1–7.
Choi, K., Lee, J., Choi, W. J., & Myung, J. S. (2023). Dynamics of semi‐flexible and breakable fibers under Poiseuille flow. Polymer Engineering & Science, 63(3), 1032–1040.
Mrzljak, S., Trautmann, M., Wagner, G., & Walther, F. (2024). Very high cycle fatigue assessment of thermoplastic-based hybrid fiber metal laminate by using a high-frequency resonant testing system. International Journal of Fatigue, 186, 108361. https://doi.org/https://doi.org/10.1016/j.ijfatigue.2024.108361
Ouled Ahmed Ben Ali, R., & Chatti, S. (2023). Springback Prediction of Sandwich Panel Using Machine Learning Methods. Mechanics Of Advanced Composite Structures, 10(1), 11–20.
Solfronk, P., Sobotka, J., & Koreček, D. (2022). Effect of the Computational Model and Mesh Strategy on the Springback Prediction of the Sandwich Material. Machines, 10(2), 114.
Li, Y., Li, A., Yue, Z., Qiu, L., Badreddine, H., Gao, J., & Wang, Y. (2020). Springback prediction of AL6061 pipe in free bending process based on finite element and analytic methods. The International Journal of Advanced Manufacturing Technology, 109, 1789–1799.
Eggertsen, P.-A., & Mattiasson, K. (2010). On constitutive modeling for springback analysis. International Journal of Mechanical Sciences, 52(6), 804–818.
Grubenmann, M., Barth, K., Heingärtner, J., Manopulo, N., Hora, P., Torkabadi, A., … Rösen, H. (2018). Analysis of yield locus description on springback behaviour of CR700Y980T-DP steel. In IOP Conference Series: Materials Science and Engineering (Vol. 418, p. 12108). IOP Publishing.
Hou, Y., Min, J., Lin, J., Liu, Z., Carsley, J. E., & Stoughton, T. B. (2017). Springback prediction of sheet metals using improved material models. Procedia Engineering, 207, 173–178.
Liu, J. G., Fu, M. W., Lu, J., & Chan, W. L. (2011). Influence of size effect on the springback of sheet metal foils in micro-bending. Computational Materials Science, 50(9), 2604–2614.
Ghaei, A., Green, D. E., & Aryanpour, A. (2015). Springback simulation of advanced high strength steels considering nonlinear elastic unloading–reloading behavior. Materials & Design, 88, 461–470.
Qadeer, A., Hussain, G., Alkahtani, M., & Buhl, J. (2023). Springback behavior of a metal/polymer laminate in incremental sheet forming: stress/strain relaxation perspective. Journal of Materials Research and Technology, 23, 1725–1737.
Cheng, L., Ji, G., Fei, S., Li, J., & Ke, Y. (2022). Investigation on insertion mechanism of ultrasound guided insertion process based on numerical simulation. Polymer Composites, 43(10), 7303–7314.
Asyraf, M. R. M., Ishak, M. R., Syamsir, A., Nurazzi, N. M., Sabaruddin, F. A., Shazleen, S. S., … Abd Rashid, M. Z. (2022). Mechanical properties of oil palm fibre-reinforced polymer composites: A review. Journal of Materials Research and Technology, 17, 33–65.
Mousavi, S. R., Zamani, M. H., Estaji, S., Tayouri, M. I., Arjmand, M., Jafari, S. H., … Khonakdar, H. A. (2022). Mechanical properties of bamboo fiber-reinforced polymer composites: a review of recent case studies. Journal of Materials Science, 57(5), 3143–3167.
Haris, N. I. N., Hassan, M. Z., Ilyas, R. A., Suhot, M. A., Sapuan, S. M., Dolah, R., … Asyraf, M. R. M. (2022). Dynamic mechanical properties of natural fiber reinforced hybrid polymer composites: A review. Journal of Materials Research and Technology.
Kella, C. K., & Mallick, P. K. (2022). Springback Behavior of Aluminum/Polypropylene/Aluminum Sandwich Laminates. Journal of Manufacturing and Materials Processing, 6(6), 152.
Kella, C. K. (2022). Formability and Springback Analysis of Aluminum/Polypropylene/Aluminum Sandwich Laminates.
Feng, Y., Shi, S., Wang, Z., & Wang, Z. (2022). Research on mechanism of springback control by viscous medium with different mechanical properties. Journal of Materials Processing Technology, 304, 117548.
Rosa-Sainz, A., García-Romeu, M. L., Ferrer, I., Silva, M. B., & Centeno, G. (2023). On the effective peek application for customized cranio-maxillofacial prostheses: An experimental formability analysis. Journal of Manufacturing Processes, 86, 66–84.
Arunkumar, T., Ravichandran, M., Varatharajulu, M., & Maridurai, T. (2022). The experimental investigation of springback and roughness parameters in the three-point forming process using terpolymer punch. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 09544054221112144.
Nikhare, C. P. (2022). Channel deformation of bilayer material using tool rollers: Part I-Springback. Advances in Materials and Processing Technologies, 8(sup3), 1842–1864.
Gardiner, F. J. (1957). The spring back of metals. Transactions of the American Society of Mechanical Engineers, 79(1), 1–7.
Li, H., Zhang, L., Chen, G., Ma, J., Wei, D., Bian, T., … Yang, H. (2022). Time-dependent springback of high strength titanium tubular materials: Experiment and modeling. Journal of Materials Processing Technology, 299, 117354. https://doi.org/https://doi.org/10.1016/j.jmatprotec.2021.117354
Rathnasabapathy, M., Orifici, A. C., & Mouritz, A. P. (2022). Impact damage to fibre metal laminates under compression loading. Composites Communications, 32, 101148. https://doi.org/https://doi.org/10.1016/j.coco.2022.101148
Hahn, M., Ben Khalifa, N., Weddeling, C., & Shabaninejad, A. (2016). Springback behavior of carbon-fiber-reinforced plastic laminates with metal cover layers in V-die bending. Journal of manufacturing Science and Engineering, 138(12).
Garcia-Romeu, M. L., Ciurana, J., & Ferrer, I. (2007). Springback determination of sheet metals in an air bending process based on an experimental work. Journal of Materials Processing Technology, 191(1–3), 174–177.
Gao, J., Chen, W., Chen, J., Hu, J., Zhao, B., Zhang, D., … Peng, F. (2021). Large deformation bending of single‐ply fabric reinforced polymer composite. Polymer Composites, 42(11), 6038–6050.
Naik, R. K., Das, A. K., Mahale, P. R., Panda, S. K., & Racherla, V. (2023). Design optimization of high interface strength metal-polymer-metal sandwich panels. Composites Part A: Applied Science and Manufacturing, 107544. https://doi.org/https://doi.org/10.1016/j.compositesa.2023.107544
Tejyan, S., Kumar, N., Kant Ravi, R., Singh, V., & Gangil, B. (2024). Analysis of spring back effect for AA6061 alloy sheet using finite element analysis. Materials Today: Proceedings. https://doi.org/https://doi.org/10.1016/j.matpr.2024.05.122
Ashby, M. F., & CEBON, D. (1993). Materials selection in mechanical design. Le Journal de Physique IV, 3(C7), C7-1.
Parsa, M. H., & Ettehad, M. (2010). Experimental and finite element study on the spring back of double curved aluminum/polypropylene/aluminum sandwich sheet. Materials & Design, 31(9), 4174–4183.
Xu, Z., Peng, L., & Bao, E. (2018). Size effect affected springback in micro/meso scale bending process: Experiments and numerical modeling. Journal of Materials Processing Technology, 252, 407–420.
Serban, F. M., Grozav, S., Ceclan, V., & Turcu, A. (2020). Artificial neural networks model for springback prediction in the bending operations. Tehnički vjesnik, 27(3), 868–873.
Liu, Z., Simonetto, E., Ghiotti, A., & Bruschi, S. (2023). Inter-ply friction behaviour in the temperature assisted forming of magnesium/glass fibre reinforced thermoplastic polymer laminates. Composites Part A: Applied Science and Manufacturing, 107635.
Hashemi, S. J., Sadooghi, A., Rahmani, K., & Akbari, S. (2022). Experimental study of the effect of temperature and velocity in channel forming of polyvinyl chloride composite reinforced by 3D-fiberglass with an aluminum middle layer. SN Applied Sciences, 4(3), 66.
Balakumaran, V., Alagirusamy, R., & Kalyanasundaram, D. (2022). Manufacture of Composites with Flexible Towpregs. In Flexible Towpregs and Their Thermoplastic Composites (pp. 259–302). CRC Press.
Kim, S., Lakshmanan, S., Li, J., Anthamatten, M., Lambropoulos, J., & Shestopalov, A. A. (2022). Modulation of Interfacial Adhesion Using Semicrystalline Shape-Memory Polymers. Langmuir, 38(11), 3607–3616.
Zhao, F., Guo, W., Li, W., Mao, H., Yan, H., & Deng, J. (2022). A Study on Hot Stamping Formability of Continuous Glass Fiber Reinforced Thermoplastic Composites. Polymers, 14(22), 4935.
Uchida, A., Peng, J., & Brown, A. (2023). Regulation of neurofilament length and transport by a dynamic cycle of phospho-dependent polymer severing and annealing. Molecular Biology of the Cell, 34(7), ar68.
Boroumand, F., Seyedkashi, S. M. H., & Pol, M. H. (2022). Experimental analysis of the warm stamping of metal/thermoplastic polymer nanocomposite laminates. Polymer Composites, 43(2), 1090–1106.
Chen, L., Deng, T., Zhou, H., Huang, Z., Peng, X., & Zhou, H. (2021). A numerical simulation method for the one-step compression-stamping process of continuous fiber reinforced thermoplastic composites. Polymers, 13(19), 3237.
Du, Z., Yan, Z., Cui, X., Chen, B., Yu, H., Qiu, D., … Deng, Z. (2022). Springback control and large skin manufacturing by high-speed vibration using electromagnetic forming. Journal of Materials Processing Technology, 299, 117340.
Hsu, Q.-C., Lin, C.-L., Wu, C.-D., & Fang, T.-H. (2012). Nanoimprint Lithography Simulation of the Polymer Chains (CH. J. Comput. Theor. Nanosci, 9, 1–7.
Huang, X., Guan, B., Zang, Y., & Wang, B. (2023). Investigation of defect behavior during the stamping of a thin-walled semicircular shell with bending angle. Journal of Manufacturing Processes, 87, 231–244.
Zhu, Y. X., Liu, Y. L., Li, H. P., & Yang, H. (2013). Comparison between the effects of PVC mandrel and mandrel-cores die on the forming quality of bending rectangular H96 tube. International Journal of Mechanical Sciences, 76, 132–143.
Özdemir, A. O., SUBAŞI, M. S., & Karataş, Ç. (2021). Investigating the Effects of Forming Parameters on Molding Force and Springback in Deep Drawing Process of Thermoplastic Composite Laminates. Gazi University Journal of Science, 1.
Chan, W. M., Chew, H. I., Lee, H. P., & Cheok, B. T. (2004). Finite element analysis of spring-back of V-bending sheet metal forming processes. Journal of Materials Processing Technology, 148(1), 15–24. https://doi.org/https://doi.org/10.1016/j.jmatprotec.2003.11.038
Harhash, M., Gilbert, R. R., Hartmann, S., & Palkowski, H. (2020). Experimental characterization, analytical and numerical investigations of metal/polymer/metal sandwich composites – Part 2: Free bending. Composite Structures, 232, 111421. https://doi.org/https://doi.org/10.1016/j.compstruct.2019.111421
Kartik, T., & Rajesh, R. (2017). Effect of punch radius and sheet thickness on spring-back in V-die bending. Advances in Natural and Applied Sciences, 11(8), 178–183.
Chai, G. B., & Manikandan, P. (2014). Low velocity impact response of fibre-metal laminates–A review. Composite Structures, 107, 363–381.
Asaee, Z., Shadlou, S., & Taheri, F. (2015). Low-velocity impact response of fiberglass/magnesium FMLs with a new 3D fiberglass fabric. Composite Structures, 122, 155–165.
Cortes, P., & Cantwell, W. J. (2005). The fracture properties of a fibre–metal laminate based on magnesium alloy. Composites Part B: Engineering, 37(2–3), 163–170.
Alderliesten, R. (2009). On the development of hybrid material concepts for aircraft structures. Recent Patents on Engineering, 3(1), 25–38.
Lange, G., Carradò, A., & Palkowski, H. (2009). Tailored sandwich structures in the focus of research. Materials and Manufacturing Processes, 24(10–11), 1150–1154.
Lebaupin, Y., Friedli, J., Caglar, B., Piccand, M., Pasquier, R., & Michaud, V. (2019). Crushing and intrusion resistance improvement of aluminum beams by carbon/epoxy composite patches. Composite Structures, 226, 111235.
Sinmazçelik, T., Avcu, E., Bora, M. Ö., & Çoban, O. (2011). A review: Fibre metal laminates, background, bonding types and applied test methods. Materials & Design, 32(7), 3671–3685.
Mezeix, L., Seman, A., Nasir, M. N. M., Aminanda, Y., Rivai, A., Castanié, B., … Ali, K. M. (2015). Spring-back simulation of unidirectional carbon/epoxy flat laminate composite manufactured through autoclave process. Composite Structures, 124, 196–205. https://doi.org/https://doi.org/10.1016/j.compstruct.2015.01.005
Zhu, S., & Chai, G. B. (2012). Low-velocity impact response of fibre–metal laminates–Experimental and finite element analysis. Composites Science and Technology, 72(15), 1793–1802.
Zhu, S., & Chai, G. B. (2014). Low-velocity impact response of fiber-metal laminates–a theoretical approach. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 228(4), 301–311.
Starikov, R. (2013). Assessment of impact response of fiber metal laminates. International Journal of Impact Engineering, 59, 38–45.
Morinière, F. D., Alderliesten, R. C., Sadighi, M., & Benedictus, R. (2013). An integrated study on the low-velocity impact response of the GLARE fibre-metal laminate. Composite Structures, 100, 89–103.
Yang, M., Liang, P., Zhang, Y., Fan, L., & Wang, G. (2023). Improvement of springback prediction accuracy applying a new constitute model considering damage and nonlinear elastic unloading-reloading behaviors. International Journal of Pressure Vessels and Piping, 204, 104961. https://doi.org/https://doi.org/10.1016/j.ijpvp.2023.104961
Chatti, S., & Fathallah, R. (2014). A study of the variations in elastic modulus and its effect on springback prediction. International journal of material forming, 7(1), 19–29.
Majidi, O., Barlat, F., & Lee, M.-G. (2016). Effect of slide motion on springback in 2-D draw bending for AHSS. International Journal of Material Forming, 9, 313–326.
Seo, K.-Y., Kim, J.-H., Lee, H.-S., Kim, J. H., & Kim, B.-M. (2017). Effect of constitutive equations on springback prediction accuracy in the TRIP1180 cold stamping. Metals, 8(1), 18.
Chen, Y., & Shang, X. (2021). Investigation on large elastoplastic deformation in expansion and springback for a composited bioresorbable stent. Journal of the Mechanical Behavior of Biomedical Materials, 119, 104500. https://doi.org/https://doi.org/10.1016/j.jmbbm.2021.104500
Henrard, C., Bouffioux, C., Eyckens, P., Sol, H., Duflou, J. R., Van Houtte, P., … Habraken, A. M. (2011). Forming forces in single point incremental forming: prediction by finite element simulations, validation and sensitivity. Computational mechanics, 47, 573–590.
Harhash, M., & Palkowski, H. (2021). Incremental sheet forming of steel/polymer/steel sandwich composites. Journal of Materials Research and Technology, 13, 417–430. https://doi.org/https://doi.org/10.1016/j.jmrt.2021.04.088
Maqbool, F., & Bambach, M. (2018). Dominant deformation mechanisms in single point incremental forming (SPIF) and their effect on geometrical accuracy. International Journal of Mechanical Sciences, 136, 279–292. https://doi.org/https://doi.org/10.1016/j.ijmecsci.2017.12.053
Harhash, M., Gilbert, R. R., Hartmann, S., & Palkowski, H. (2018). Experimental characterization, analytical and numerical investigations of metal/polymer/metal sandwich composites–Part 1: Deep drawing. Composite structures, 202, 1308–1321.
Azhdar, B., Stenberg, B., & Kari, L. (2006). Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction. Polymer Testing, 25(1), 114–123. https://doi.org/https://doi.org/10.1016/j.polymertesting.2005.09.002
Bikakis, G. S. E. (2017). Simulation of the dynamic response of GLARE plates subjected to low velocity impact using a linearized spring–mass model. Aerospace Science and Technology, 64, 24–30.
Kim, S. Y., Choi, W. J., & Park, S. Y. (2007). Spring-back characteristics of fiber metal laminate (GLARE) in brake forming process. The International Journal of Advanced Manufacturing Technology, 32, 445–451.
Kazemi, F., Hashemi, R., & Niknam, S. A. (2022). Formability and fractography of AA5754/polyethylene/AA5754 sandwich composites. Mechanics Based Design of Structures and Machines, 50(4), 1253–1267.
Pan, L., Wang, Y., Hu, Y., Lv, Y., Ali, A., Roy, N., … Tao, J. (2020). Investigation on the effect of configuration on tensile and flexural properties of aluminum/self-reinforced polypropylene fiber metal laminates. Journal of Sandwich Structures & Materials, 22(6), 1770–1785.
Zhang, Y., Wan, Y., Nakamura, T., & Takahashi, J. (2017). Effect of springback ratio on bending and impact property of carbon fiber reinforced thermoplastics sandwich structures. In Proceedings of the 21st International Conference on Composite Materials, Xi’an, China (pp. 20–25).
Ouled Ahmed Ben Ali, R., & Chatti, S. (2020). Simplified springback prediction of thick sandwich panel. Journal of Sandwich Structures & Materials, 22(4), 1019–1038.
Lepadatu, D., Hambli, R., Kobi, A., & Barreau, A. (2005). Optimisation of springback in bending processes using FEM simulation and response surface method. The International Journal of Advanced Manufacturing Technology, 27, 40–47.
Davarpanah, M. A., & Malhotra, R. (2018). Formability and failure modes in single point incremental forming of metal-polymer laminates. Procedia Manufacturing, 26, 343–348.
Mohammadi, S. V, Parsa, M. H., & Aghchai, A. J. (2011). Effect of the thickness distribution and setting condition on springback in multi-layer sheet bending. International Journal of engineering, science and technology, 3(4).
Seyed Yaghoubi, A., Liu, Y., & Liaw, B. (2012). Low-velocity impact on GLARE 5 fiber-metal laminates: influences of specimen thickness and impactor mass. Journal of Aerospace Engineering, 25(3), 409–420.
Tozawa, Y. (1990). Forming technology for raising the accuracy of sheet-formed products. Journal of materials processing technology, 22(3), 343–351.
El-Domiaty, A. A., Shabara, M. A. N., & Al-Ansary, M. D. (1996). Determination of stretch-bendability of sheet-metals. International Journal of Machine Tools and Manufacture, 36(5), 635–650.
Wang, C., Kinzel, G., & Altan, T. (1993). Mathematical modeling of plane-strain bending of sheet and plate. Journal of Materials Processing Technology, 39(3–4), 279–304.
Zhou, G., Sun, Q., Fenner, J., Li, D., Zeng, D., Su, X., & Peng, Y. (2020). Crushing behaviors of unidirectional carbon fiber reinforced plastic composites under dynamic bending and axial crushing loading. International Journal of Impact Engineering, 140, 103539. https://doi.org/https://doi.org/10.1016/j.ijimpeng.2020.103539
Megahed, M., Abd El-baky, M. A., Alsaeedy, A. M., & Alshorbagy, A. E. (2019). An experimental investigation on the effect of incorporation of different nanofillers on the mechanical characterization of fiber metal laminate. Composites Part B: Engineering, 176, 107277. https://doi.org/https://doi.org/10.1016/j.compositesb.2019.107277
Shah, D. B., Patel, K. M., Patel, A. I., Pariyal, V., & Joshi, S. J. (2018). Experimental investigation on spring-back deformation during autoclave curing of parabolic antenna reflectors. Composites Part A: Applied Science and Manufacturing, 115, 134–146. https://doi.org/https://doi.org/10.1016/j.compositesa.2018.09.017
Kumar, S. S., Akmal, J. S., & Salmi, M. (2023). 4D printing of shape memory polymer with continuous carbon fiber. Progress in Additive Manufacturing, 1–11.
Said, R. W., & Mehrabi, M. (2023). Parametric study of part dimensional variations due to spring-back effects in deep drawing: theory and experiment. The International Journal of Advanced Manufacturing Technology, 127(11–12), 5171–5183.
Dessie, J. E., & Lukacs, Z. (2023). Determination of influential springback parameters in U-bending test. Pollack Periodica, 18(2), 17–22.
Cheng, J., Cao, J., Wei, Z., Wang, X., Zhu, H., & Zhao, R. (2023). Modelling and prediction of twist springback for UHSS thin-walled component with asymmetric complex section in roll forming process. The International Journal of Advanced Manufacturing Technology, 129(9), 4257–4274.
Zhao, M., Cai, Y., Wang, N., Song, Y., & Wang, H. (2023). The research of cutting force prediction for worn ball-end tool considering spring back. The International Journal of Advanced Manufacturing Technology, 125(11), 5619–5629.
Ghafari, H., Alimirzaloo, V., & Farhadi, S. (2024). Improvement of electromagnetic calibration of springback in bent sheet metals using a novel tool coil. Journal of Manufacturing Processes, 117, 111–124.
Yu, T., & Zhang, L. (1996). Plastic bending: theory and applications (Vol. 2). World Scientific.
Zhang, Q.-F., Cai, Z.-Y., Zhang, Y., & Li, M.-Z. (2013). Springback compensation method for doubly curved plate in multi-point forming. Materials & Design, 47, 377–385.
Briesenick, D., & Liewald, M. (2022). Multistage Deep-Drawing with Alternating Blank Draw-in for Springback Reduction in Transfer and Progressive Dies. In Key Engineering Materials (Vol. 926, pp. 674–682). Trans Tech Publ.
Li, H., Tian, J., Fei, W., Han, Z., Tao, G., Xu, Y., … Tao, J. (2019). Spring-back and failure characteristics of roll bending of GLARE laminates. Materials Research Express, 6(8), 0865b2.
Jin, L., Yang, Y.-F., Li, R.-Z., Cui, Y.-W., Jamil, M., & Li, L. (2020). Study on springback straightening after bending of the U-Section of TC4 material under high-temperature conditions. Materials, 13(8), 1895.
Shang, W., Ren, H., Yi, Z., Xu, T., & Wu, X. (2022). High precision PCB Soldering With Pin Springback Compensation by Robotic Micromanipulation. IEEE/ASME Transactions on Mechatronics.
Saravanan, S., Saravanan, M., Jeyasimman, D., Vidhya, S., & Vairavel, M. (n.d.). Art of Single Step Analytical Analysis for Springback Formation in “U” Bending Forming Process.
Su, S., Jiang, Y., & Xiong, Y. (2020). Multi-point forming springback compensation control oftwo-dimensional hull plate. Advances in Mechanical Engineering, 12(4), 1687814020916094.
Behrouzi, A., Dariani, B. M., & Shakeri, M. (2009). A one-step analytical approach for springback compensation in channel forming process. In Proceedings of the World Congress on Engineering (Vol. 2, pp. 1757–1762).
Jung, W.-K., Chu, W.-S., Ahn, S.-H., & Won, M.-S. (2007). Measurement and compensation of spring-back of a hybrid composite beam. Journal of composite materials, 41(7), 851–864.
Jung, W.-K., Kim, B., Won, M.-S., & Ahn, S.-H. (2006). Fabrication of radar absorbing structure (RAS) using GFR-nano composite and spring-back compensation of hybrid composite RAS shells. Composite Structures, 75(1–4), 571–576.
Zhang, P., Pereira, M., Rolfe, B., Daniel, W., & Weiss, M. (2017). Deformation in micro roll forming of bipolar plate. In Journal of Physics: Conference Series (Vol. 896, p. 12115). IOP Publishing.
Xiong, Z., Zhao, G., Zhang, R., Guo, Z., Tian, Y., & Yang, Z. (2024). Analysis of Springback Characteristics of Bending Unloading for Stainless Steel tubes. In Journal of Physics: Conference Series (Vol. 2706, p. 12004). IOP Publishing.
Bhola, L., Saurav, A. K., Mujumdar, P. M., & Guruprasad, P. J. (2023). A numerical approach for modeling response of shape memory polymer composite corrugated structure. Smart Materials and Structures, 32(8), 85004.
Zhang, C., Zhu, Q., Wang, Y., & Ma, P. (2020). Finite element simulation of tensile preload effects on high velocity impact behavior of fiber metal laminates. Applied Composite Materials, 27, 251–268.
Dou, X., & Tunggal, D. (2015). Finite element modeling of stamp forming process on thermoplastic-based fiber metal laminates at elevated temperatures. World Journal of Engineering and Technology, 3(03), 253.
Xin, S., Zheng, L., & Jiazhen, Z. (2011). Simulation study of fracture behavior in a FMLs specimen by 3D elastic-plastic finite element model. Polymers and Polymer Composites, 19(2–3), 209–212.
Soltani, P., Keikhosravy, M., Oskouei, R. H., & Soutis, C. (2011). Studying the tensile behaviour of GLARE laminates: a finite element modelling approach. Applied Composite Materials, 18, 271–282.
Zhu, Q., Zhang, C., Curiel-Sosa, J. L., Bui, T. Q., & Xu, X. (2019). Finite element simulation of damage in fiber metal laminates under high velocity impact by projectiles with different shapes. Composite Structures, 214, 73–82.
Smolnicki, M., Lesiuk, G., Duda, S., & de Jesus, A. M. P. (2023). A review on finite-element simulation of fibre metal laminates. Archives of Computational Methods in Engineering, 30(2), 749–763.
Zal, V., Naeini, H. M., Sinke, J., Bahramian, A. R., Abouhamzeh, M., & Benedictus, R. (2017). A new procedure for finite element simulation of forming process of non-homogeneous composite laminates and FMLs. Composite Structures, 163, 444–453.
Wagoner, R. H., Lim, H., & Lee, M.-G. (2013). Advanced issues in springback. International Journal of Plasticity, 45, 3–20.
Wu, T., Degener, S., Tinkloh, S., Liehr, A., Zinn, W., Nobre, J. P., Niendorf, T. (2022). Characterization of residual stresses in fiber metal laminate interfaces – A combined approach applying hole-drilling method and energy-dispersive X-ray diffraction. Composite Structures, 299, 116071. https://doi.org/https://doi.org/10.1016/j.compstruct.2022.116071
Kulkarni, S. S., Venkatraman, A., Senor, D. J., & Devanathan, R. (2023). A sensitivity analysis of twinning crystal plasticity finite element model using single crystal and poly crystal Zircaloy. Computational Materials Science, 230, 112425.
Liu, C., Li, M., & Yue, T. (2021). Thick anisotropy analysis for AA7B04 aluminum plate using CPFEM and its application for springback prediction in multi-point bending. The International Journal of Advanced Manufacturing Technology, 115(4), 1139–1153.
Kim, J. H., Lee, M.-G., Kang, J.-H., Oh, C.-S., & Barlat, F. (2017). Crystal plasticity finite element analysis of ferritic stainless steel for sheet formability prediction. International Journal of Plasticity, 93, 26–45.
Bong, H. J., Lee, J., Hu, X., Sun, X., & Lee, M.-G. (2020). Predicting forming limit diagrams for magnesium alloys using crystal plasticity finite elements. International Journal of Plasticity, 126, 102630.
Bong, H. J., Lee, J., Lee, M.-G., & Kim, D. (2019). Identification of mechanical responses of steel sheets under non-proportional loadings using dislocation-density based crystal plasticity model. International Journal of Mechanical Sciences, 155, 461–474.
Kraska, M., Doig, M., Tikhomirov, D., Raabe, D., & Roters, F. (2009). Virtual material testing for stamping simulations based on polycrystal plasticity. Computational materials science, 46(2), 383–392.
Barlat, F., Gracio, J. J., Lee, M.-G., Rauch, E. F., & Vincze, G. (2011). An alternative to kinematic hardening in classical plasticity. International Journal of Plasticity, 27(9), 1309–1327.
Joo, M., Wi, M.-S., Yoon, S.-Y., Lee, S.-Y., Barlat, F., Tomé, C. N., … Jeong, Y. (2023). A crystal plasticity finite element analysis on the effect of prestrain on springback. International Journal of Mechanical Sciences, 237, 107796.
Tang, W., Xu, Y., Hui, X., & Zhang, W. (2022). Multi-Objective Optimization of Curing Profile for Autoclave Processed Composites: Simultaneous Control of Curing Time and Process-Induced Defects. Polymers, 14(14), 2815.
Poursafar, A., Saberi, S., Tarkesh, R., Vahabi, M., & Fesharaki, J. J. (2022). Experimental and mathematical analysis on spring-back and bowing defects in cold roll forming process. International Journal on Interactive Design and Manufacturing (IJIDeM), 16(2), 531–543.
Kagzi, S. A., & Raval, H. K. (2022). Mathematical modelling to predict springback in bimetallic material including material anisotropy during bending. Advances in Materials and Processing Technologies, 1–13.
Ouled Ahmed Ben Ali, R., & Chatti, S. (2019). Modeling springback of thick sandwich panel using RSM. The International Journal of Advanced Manufacturing Technology, 103(9–12), 3375–3387.
Li, X., & Hu, S. (2023). Ultrasonic Vibration Theory and Its Application in Reducing Springback for Multi-point Forming. In Journal of Physics: Conference Series (Vol. 2437, p. 12091). IOP Publishing.
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