Penetration Depth in Electron Beam Welding (Report 3)

Measurement of Electron Beam Energy Density Distribution

Abstract

It was shown in the reports already published that energy density was the most responsible parameter to penetration depth in electron beam welding. Up to date, there have been proposed various measurements of the density. Most of these, however, used a method, in which a rod or a plane cuts the beam rapidly and variation of beam current is measured so that density distribution obtained is in X or Y direction.
The authors developed a new apparatus able to measure current density distribution in raidal direction and carried out various experiments.
The results are summerized as follows;
1) The electron beam shows various types of density distribution along the objective distance.
2) Focal point or convergence angle of the electron beam always fluctuates according to ripple component of electron beam power source.
3) In comparison between the results by this apparatus and by the "AB-test" proposed by Dr. Arata et al, the AB-test is one of useful methods when the energy density of electron beam is sufficiently high.