Advanced Plastic Forming Processes: Theory, Experiments and Numerical Simulations

1. Introduction and Scope

Plastic-forming technologies represent an essential component of advanced manufacturing, as they enable not only the fabrication of components with complex geometries but also the simultaneous achievement of excellent comprehensive in-service performance [1]. The rapid development of major engineering equipment in aerospace, aviation, high-speed rail, and nuclear power industries has posed significant challenges to the fundamental theories of plastic forming, advanced forming processes, the accuracy of process simulations, and the control of characteristic component dimensions.

Springback is a key factor that affects the forming accuracy of metal profiles, and its reliable prediction requires an accurate constitutive model [2]. The degradation behavior of the elastic modulus and its nonlinear response [3,4,5,6], plastic hardening behavior [7,8], Bauschinger effect [9], and strength-differential effect [10,11] are critical factors that limit the springback prediction accuracy. By embedding accurate constitutive models into finite element simulation software, high-precision prediction of bending springback in metal sheets and tubes has been achieved [12,13,14]. In recent years, with the rapid development of the microforming process, the theory of plastic forming has evolved from the macroscopic to the microscopic scale [15,16,17].

For materials with poor deformability and structures with difficult forming, the field-assisted plastic-forming process can improve the mechanical properties of the materials, unlock the forming potential of the materials and enhance the forming limit. A series of new field-assisted plastic-forming processes has been developed, such as impact hydraulic forming [18,19], electric-assisted forming [20,21,22], thermal-assisted forming [23,24], low-temperature forming [25,26], viscous pressure bulging [27], and electromagnetic forming [28,29,30,31]. The proposal and development of these advanced plastic-forming processes have provided new technical approaches for the high-precision forming of complex components.

2. Contributions

This Special Issue features 11 original contributions in the advanced plastic-forming field, covering topics such as ultrasonic vibration-assisted forming, hydraulic forming, electromagnetic forming, forging processes, bar straightening, stiffened plates for anti-buckling structural design, and composite material structure design.

Li et al. (contribution 1) investigated ultrasonic vibration-assisted superplastic forming of amorphous alloys, demonstrating that the introduction of ultrasonic vibration significantly reduces the flow stress of the amorphous alloy and thereby enhances its plastic deformation capability. Numerical simulations revealed that ultrasonic vibration induces periodic interfacial separation between the indenter and the specimen, leading to the cyclic disappearance of frictional forces. In addition, ultrasonic vibration effectively decreases the apparent viscosity of the amorphous alloy, thereby improving its material filling ability.

Liu et al. (contribution 2) investigated the influence of forming process parameters on the dimensional accuracy of multilayer metal bellow hydroforming. Process parameter optimization was carried out using response surface methodology in conjunction with a genetic algorithm. The bellows formed under the optimized conditions were demonstrated to satisfy the dimensional tolerances specified by the EJMA standard.

Jia et al. (contribution 3) investigated the effects of inclination angle, roll reduction, straightening speed, and roll gap on the straightening quality of 20CrMnTi bars during the eleven cross-roll straightening process.

Lancanova et al. (contribution 4) investigated the influence of geometric configurations on the buckling load-carrying capacity and structural stability of stiffened plates, demonstrating that an appropriate distribution of stiffener height and plate thickness can significantly enhance buckling resistance.

Alves et al. (contribution 5) employed constructal design coupled with exhaustive search to optimize the geometry of transverse hat-stiffeners in steel plates under bending. The optimized configuration achieved a substantial reduction in deflection and demonstrated superior structural performance over longitudinal stiffeners under equivalent material volume.

Zhang et al. (contribution 6) investigated the effects of pass number and die channel angle in equal channel angular pressing (ECAP) on the microstructure, mechanical properties, and corrosion resistance of the nano-MgO/Mg–Zn–Ca composite material. By optimizing ECAP processing parameters, a synergistic enhancement of strength, ductility, and corrosion resistance in the composite material was achieved.

Dou et al. (contribution 7) investigated the influence of electrically assisted forming parameters on the mechanical behavior and springback of 7075-T6 aluminum alloy. Electrically assisted three-point bending tests revealed that increasing current density effectively reduces the springback angle.

Wang et al. (contribution 8) investigates the effects of electric pulse treatment on the interfacial properties of roll-bonded Cu/304 stainless steel composite thin strips, revealing that electric pulses promote interfacial diffusion and metallurgical bonding, thereby rapidly enhancing interfacial strength as an alternative to conventional annealing.

Wang et al. (contribution 9) analyzes the multi-physical field coupling behavior in electro-controlled permanent magnet blank holder processes. A coupled electromagnetic–thermal model considering magnetic losses is established, revealing the influence of magnetic degradation on blank holding force stability and forming accuracy.

Niu et al. (contribution 10) studied near-net shape forging of large marine crank throws through numerical simulation and experiments. Metal flow behavior and defect evolution were clarified, enabling improved forming accuracy and material utilization for large-scale marine crank components.

Yan et al. (contribution 11) investigated the influence of asymmetric roll bending forces on metal deformation and strip shape in cold rolling using a three-dimensional elastic–plastic finite element model. The results clarify the linear regulation mechanisms of thickness, crown, edge drop, and flatness, providing guidance for controlling asymmetric strip shape defects.

3. Conclusions and Outlook

This Special Issue highlights recent advances in plastic forming through the integration of novel forming techniques, multi-physical field assistance, and advanced numerical modeling. The collected studies demonstrate that auxiliary fields, such as ultrasonic vibration, electric current, and electromagnetic control, effectively improve formability, dimensional accuracy, and interfacial or structural performance. Meanwhile, simulation-based optimization methods and refined constitutive models enable accurate prediction and efficient control of complex deformation behaviors. Future research is expected to further emphasize multi-field coupling mechanisms, intelligent optimization strategies, and precision plastic-forming process.