Zhuojin Pipe Fitting Co., LtdEnergy Utilization Rate in Simultaneous Plate and Pipe Electromagnetic Forming Using a Dual-Plate-Pipe Model
Literature Overview
This paper, published in the Journal of Plasticity Engineering in 2022 (Vol. 29, No. 7, pp. 58-65), was authored by Jiang Chenfei, Qiu Li, Liu Hongchi, Wang Chenglin, and Li Zhi from the College of Electrical Engineering and New Energy at China Three Gorges University, supported by the National Natural Science Foundation of China (Grants No. 51877122 and 51707104). The study addresses the critically low energy utilization rate in electromagnetic forming processes and proposes a novel dual-plate-pipe model that simultaneously forms both plate and pipe workpieces using a single drive coil.
Core Technical Content
The Energy Utilization Challenge
Electromagnetic forming is a high-speed, non-contact forming process that uses the Lorentz force generated by the interaction between a pulsed magnetic field and induced eddy currents to plastically deform conductive workpieces. Despite its numerous advantages—including high forming speeds, excellent surface finish, and the ability to form complex geometries—the process suffers from a fundamentally low energy utilization rate. In conventional electromagnetic forming, the majority of the electrical energy stored in the capacitor bank is dissipated as heat in the discharge circuit, the drive coil, and the workpiece, with only a small fraction contributing to useful plastic deformation.
The typical energy utilization rates in electromagnetic forming range from 1% to 10%, depending on the process configuration, workpiece geometry, and discharge parameters. This low efficiency is a major barrier to industrial adoption, as it limits the process economics and scalability. Improving the energy utilization rate is therefore a critical research objective in the field of electromagnetic forming.
Proposed Dual-Plate-Pipe Model
The authors propose a novel dual-plate-pipe electromagnetic bulging model in which a single drive coil is used to simultaneously form both a plate workpiece and a pipe workpiece. The key innovation lies in the strategic arrangement of the two workpieces around the drive coil such that the magnetic flux distribution and electromagnetic force fields act on both workpieces simultaneously, thereby improving the overall energy utilization rate of the system.
The physical principle underlying this approach is that the magnetic flux generated by the drive coil current must pass through the magnetic concentrator and interact with the workpieces. In a conventional single-workpiece configuration, a significant portion of the magnetic flux does not contribute to useful work on the workpiece. By introducing a second workpiece (the pipe) in addition to the plate, the magnetic flux path is more effectively utilized, and a greater proportion of the electromagnetic energy is converted into useful plastic deformation energy.
Key Results and Technical Analysis
Energy Utilization Rate Comparison
| Forming Configuration | Optimal Energy Utilization Rate | Relative Improvement |
|---|---|---|
| Traditional single-plate electromagnetic bulging | 5.05% | Baseline |
| Traditional single-pipe electromagnetic bulging | 9.80% | 94% improvement over single-plate |
| Dual-plate-pipe electromagnetic bulging | 11.85% | 134% improvement over single-plate |
The results clearly demonstrate that the dual-plate-pipe configuration achieves the highest energy utilization rate of 11.85%, representing a 134% improvement over the traditional single-plate configuration and a 20.9% improvement over the traditional single-pipe configuration. This finding validates the hypothesis that simultaneous forming of multiple workpieces can improve the overall energy efficiency of the electromagnetic forming system.
Magnetic Flux Density Distribution
The magnetic flux density distribution in the dual-plate-pipe configuration differs significantly from the single-workpiece configurations. In the single-plate model, the magnetic flux concentrates primarily on one side of the drive coil, with a significant portion of the flux "leaking" or passing through regions that do not contribute to useful forming work. In the dual-plate-pipe model, the pipe workpiece occupies the region where flux would otherwise be wasted, effectively capturing and utilizing this flux for forming work on the pipe.
The magnetic flux density distribution analysis reveals that the dual-plate-pipe configuration achieves a more uniform and efficient flux distribution. The plate workpiece captures the flux on one side of the coil, while the pipe workpiece captures the flux on the other side, creating a more balanced and efficient magnetic circuit.
Effect of Equivalent Pulse Width
The study investigates the influence of the equivalent pulse width of the drive coil current on the energy utilization rate. The equivalent pulse width is a measure of the duration and shape of the current pulse, which directly affects the magnetic field strength, electromagnetic force magnitude, and energy delivery rate to the workpieces.
The results show that there exists an optimal equivalent pulse width for each forming configuration that maximizes the energy utilization rate. For the dual-plate-pipe configuration, the optimal pulse width is different from those of the single-plate and single-pipe configurations, reflecting the different electromagnetic and mechanical coupling characteristics of the dual-workpiece system.
Energy Conversion Mechanism
The energy conversion chain in electromagnetic forming involves several stages:
- Electrical energy stored in the capacitor bank
- Electrical energy delivered to the drive coil through the discharge circuit
- Magnetic energy stored in the magnetic field generated by the drive coil
- Electromagnetic force (Lorentz force) acting on the workpiece
- Kinetic energy of the workpiece
- Plastic deformation energy (useful work)
- Dissipated energy (heat, sound, etc.)
The energy utilization rate is defined as the ratio of plastic deformation energy to the total electrical energy input. The dual-plate-pipe configuration improves this ratio by increasing the fraction of magnetic energy that is converted into useful plastic deformation work on both workpieces simultaneously.
Engineering Practice Integration
Implications for Production Efficiency
From a production engineering perspective, the 11.85% energy utilization rate achieved by the dual-plate-pipe configuration is still relatively low in absolute terms, but it represents a meaningful improvement over existing configurations. For industrial electromagnetic forming systems, which typically operate at discharge energies of 50 kJ to 500 kJ, even a small improvement in energy utilization rate can translate into significant energy savings and cost reductions over the lifetime of the system.
System Design Considerations
The implementation of the dual-plate-pipe forming concept requires careful consideration of several system design aspects:
| Design Aspect | Key Consideration | Impact on Performance |
|---|---|---|
| Drive coil geometry | Must accommodate both plate and pipe workpieces | Determines flux distribution and force balance |
| Magnetic concentrator design | Must guide flux to both workpieces | Critical for energy utilization efficiency |
| Workpiece positioning | Relative placement of plate and pipe | Affects force distribution and deformation quality |
| Discharge circuit parameters | Capacitor voltage, pulse width, resistance | Determines energy delivery characteristics |
| Workpiece material properties | Conductivity, permeability, yield strength | Affects electromagnetic force and deformation response |
Connection to Fitting Manufacturing
While the study focuses on the energy utilization rate rather than the forming quality, the dual-plate-pipe concept has implications for fitting manufacturing. In a production environment, the ability to form both plates (which can be used for flanges, covers, or other components) and pipes (which can be used for elbows, tees, or reducers) simultaneously using a single drive coil could significantly improve production throughput and reduce energy costs.
Standards and Quality Considerations
The quality of workpieces formed using the dual-plate-pipe method must comply with applicable standards. For plate workpieces, standards such as ASME B16.5 (for flanges) or EN 1092-1 (for steel flanges) specify dimensional tolerances, material requirements, and testing requirements. For pipe workpieces, standards such as ASME B16.9 (for butt-weld fittings) or ASTM A234 (for wrought carbon steel and alloy steel fittings) apply. The electromagnetic forming process, regardless of the configuration, must produce workpieces that meet these standards in terms of dimensional accuracy, mechanical properties, and surface quality.
Study Insights and Independent Reflection
The fundamental insight of this work is that the energy utilization rate in electromagnetic forming can be improved not only by optimizing the interaction between the magnetic field and a single workpiece but also by strategically arranging multiple workpieces to make more efficient use of the available magnetic flux. This concept is analogous to the principle of "multiplexing" in signal processing, where multiple signals are transmitted over a single channel to improve channel utilization efficiency.
One reflection worth noting is the trade-off between energy utilization rate and forming quality. While the dual-plate-pipe configuration achieves a higher energy utilization rate, it also introduces additional complexity in terms of workpiece positioning, force balance, and deformation control. In practice, the forming quality of each individual workpiece must be verified independently, and the process parameters must be optimized to ensure that both workpieces meet their respective quality requirements.
Another consideration is the scalability of this approach. The study uses a single drive coil to form two workpieces. Could this concept be extended to three or more workpieces? While theoretically possible, the practical limitations of magnetic flux distribution, force balance, and workpiece positioning would become increasingly challenging as the number of workpieces increases. The optimal number of workpieces for a given drive coil geometry and discharge energy would need to be determined through both simulation and experimental investigation.
The 11.85% energy utilization rate, while an improvement, is still far from the theoretical maximum. The fundamental limitation lies in the inherent energy losses in the electromagnetic forming system, including resistive heating in the drive coil and discharge circuit, magnetic hysteresis losses in the magnetic concentrator, and eddy current heating in the workpieces. Future research should focus on reducing these losses through advanced materials (such as superconducting drive coils or low-loss magnetic concentrators) and improved discharge circuit design.
Conclusion and Outlook
This study demonstrates that the simultaneous forming of plate and pipe workpieces using a single drive coil can significantly improve the energy utilization rate of electromagnetic forming systems. The 11.85% energy utilization rate achieved by the dual-plate-pipe configuration represents a 134% improvement over the traditional single-plate configuration, validating the concept of multi-workpiece electromagnetic forming as a viable approach to improving process efficiency. The magnetic flux density and electromagnetic force distribution analyses provide valuable insights into the physical mechanisms underlying this improvement. For industrial implementation, further work is needed on process optimization, quality control, and integration with existing production systems. The concept of multi-workpiece electromagnetic forming opens up new possibilities for improving the energy efficiency and economic viability of electromagnetic forming processes in the manufacturing of pipe fittings and other components.