プラズマアーク切断機構に関する研究 Ｉ 熱源の半径方向熱流分布特性推定のための境界最小２乗選点法の利用

Abstract

Radial heat flux distribution of plasma arc on a surface of cutting plate influences not only on the cutting groove shape but also on the maximum cut thickness. No available technique, however, have been realized to estimate the radial heat flux distribution in cutting groove until now.So, a new technique was developed for measuring the radial heat flux distribution in the cutting groove with two information on cutting front shape and position of the plasma arc, since the required heat flux to melt the cutting front balances with the heat flux from arc to the cutting front. Each arc position in the groove was measured with snapshots of the arc and the cutting front. The required heat flux value was estimated by a numerical calculation with a least squares-collocation method on the cutting boundary, which belongs to the Method of We ghted Residuals (MWR). A set of functions derived by separation of variable for the two-dimensional heat conduction equation in quasi-stationary state was selected for trial functions in the MWR, which satisfies the differential equation and boundary conditions except those on the cutting front and side surface.Following results are clarified by the new technique;1) Heat flux distribution on the cutting front can be estimated by using the new technique even though wide unknown regoin of boundary condition exists near solidifying line of cut surface.2) The degree of symmetry of radial heat flux distribution in plasma arc cutting groove scarcely changes in comparison with that in free boundary condition.3) Values of melting efficiency in ordinary plasma arc cutting pretty differs from those in moving line heat source model.