Mathematical Modeling of an Electromagnetic Forming System with Flat Spiral Coils as Actuator

This study presents mathematical modeling and calculation procedure for problems of electromagnetic forming of thin circular metal sheets using flat spiral coil as actuator. The method focuses specifically on the calculation of the electromagnetic field generated by the flat coil and analysis of the circuit that models the electromagnetic forming system. The flat coil is approximated by concentric circles carrying the current discharge from the capacitors. The calculation of electromagnetic force and magnetic couplings between the coil and metal sheet are made to the initial time, before the plastic deformation of the sheet. The method is based on the Biot-Savart law, and the solution of magnetic induction integral equations is performed by numerical methods specifically with the use of Matlab commercial software. A routine calculation, which models the problem as a set of differential equations was implemented in the Matlab, this provides important information that serves as feedback for system design. Free bulging experiments were performed to demonstrate a good relationship with the mathematical model predictions for electrical discharge current in the coil and induced currents in the metal sheet, behavior of the transient electromagnetic force between coil and workpiece and, distribution of magnetic field and electromagnetic density force along the coil. Also, achieved results showed that there is a strong dependence of the back electromagnetic force with respect to plate thickness for the system analyzed. The difference phase between the current induced in the coil and workpiece with higher negative peaks generate the back electromagnetic force

Proposal for a Test Bench for Electromagnetic Forming of Thin Metal Sheets

This paper presents a proposal to build a test bench for electromagnetic forming processes. The project considers the analysis of the electrical circuit and forces involved in the system for selection of low voltage capacitors, resistors, buses, main discharge switch and material choice for actuator s insulation and rigidity, considering also the manufacturing process of actuators and dies. Among the aspects considered for the design, energy efficiency has been prioritized by the use of non-conducting material to the dies. Main switches by mechanical contact and spark gap types were used and its wear and functionality was assessed. Free bulging experiments were performed with aluminium AA1100 plates for a system configured with a flat coil actuator. Test measurements of electric currents in the coil actuator with and without the workpiece as the secondary circuit were performed, as well as an evaluation of wear and functionality of the system. It is observed that the main switch discharge is one of the most critical items of the system

Epidemiological features and disease-related concerns of a large cohort of Italian patients with active Crohn's disease

BACKGROUND-AIMS: The SOLE study was conducted on a large cohort of Italian patients with moderate-severe Crohn's disease (CD) to assess epidemiological and disease characteristics and their correlation with disease-related worries, treatment satisfaction and adherence, workability. METHODS: The following tools were used over 12 months to assess: Results were correlated with demographic and clinical variables with linear regression models. RESULTS: 552 patients with active CD (51% men) were recruited. Higher worries were having an ostomy bag and undergoing surgery. Variables associated with a higher RFIPC score included female sex, higher disease activity, lower treatment adherence (p\u202f<\u202f0.001), previous surgical treatments (p\u202f=\u202f0.003). 60% of patients claimed difficulties with activities of daily living. Lower VAS scores were reported by patients with disease duration >6years; treatment satisfaction/adherence was higher with anti-TNF-\u3b1 treatment. Decreased hospitalizations during follow-up and improved workability/daily activities occurred with adalimumab, infliximab, azathioprine (p\u202f<\u202f0.001). CONCLUSION: Worries included having an ostomy bag, undergoing surgery, developing cancer: conditions significantly associated with worsened disease activity and low treatment adherence. Higher treatment adherence scores/greater workability improvements were observed in patients treated with anti-TNF-\u3b1 agents