In this study, forming limit diagram (FLD) of tubular material (Al 7020-T6) was determined numerically and experimentally. A set of experimental bulge tests were carried out to determine FLD under combined internal pressure and axial feeding. Also, a numerical approach which is based on the acceleration of plastic strain (i.e., the second derivation) was applied to compute the hydroforming strain limit diagram. Based on this method, the localized necking would be started when the acceleration of the max plastic strain got its maximum value. Finally, the numerical FLD was verified by experimental test results on the aluminum tube 7020-T6 and a good agreement between the proposed method and the experimental works was observed.
<p>In this paper, the efficiency and the quality factor (Q) of an infinitesimal loop antenna with the circumference of 0.01λ enclosed in a µ-negative (MNG) shell of 0.023λ diameter is investigated. It is demonstrated that an MNG shell can be designed to produce an electrically small system with a matched input impedance leading to total efficiency approaching unity. Simulation results show that the fractional bandwidth of significantly better than Chu limit can be obtained, especially if the material is regarded dispersionless. The calculated Q of the antenna with LL model, M model, and Z model MNG are 74.5%, 55.9%, and 37.5% of those predicted by Chu limit, respectively.</p>
<p>In this paper, the efficiency and the quality factor (Q) of an infinitesimal loop antenna with the circumference of 0.01λ enclosed in a µ-negative (MNG) shell of 0.023λ diameter is investigated. It is demonstrated that an MNG shell can be designed to produce an electrically small system with a matched input impedance leading to total efficiency approaching unity. Simulation results show that the fractional bandwidth of significantly better than Chu limit can be obtained, especially if the material is regarded dispersionless. The calculated Q of the antenna with LL model, M model, and Z model MNG are 74.5%, 55.9%, and 37.5% of those predicted by Chu limit, respectively.</p>
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