The mathematic model of keyhole formation in double-side arc welding is established through considering all influencing dynamic factors, such as plasma arc pressure, gravity and surface tension.

For the elementary hologram,except normal holographic imaging,as the diverging angle of reconstructing curved surface sub wave is very small,by use of the principle of small hole imaging,it forms a standing upside down real image in the observation screen.

Then it points out that the phenomenon is not diffraction but the puncture forming picture and gives the new opinion to contents of the ancients.

This paper analyses some experiments that Fang Yizhi discussed in his theory about Guang Fei Ying Shou,points out that Fang s theory does not deal with the phenomenon of the light diffracted, but merely refers to the phenoemnon of the puncture forming picture and the atmosphere scattering light.

Seismic behavior of frame connection with some small round openings on beam web;

According to laser deep penetration welding existing the characteristics of keyhole,create a micron-size precise calculation model that coincidence with the keyhole profile.

Using the Gaussian rotating curved body heat source fitting for the keyhole profile and combining the material property of TC4 titanium alloy, the distribution characteristics of keyhole profile and transient welding temperature varying with the laser parameters have obtained.