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In order to study the effect of plywood’s thickness on vertical fire spread, small-sized experiment is conducted to study flame front position, pyrolysis front position and burnout front position at the thickness of 2,3,6 mm respectively. Through the effect of sample thickness on flame spread rate, flame height and pyrolysis height are analyzed, the experimental results show that the thickness has obvious influences on the process of the plywood vertical fire spread. Flame front position, pyrolysis front position and burnout front position, those three increases with the decrease on the sample thickness, which is consistent with the trend of flame spread rate with thickness. In the process of vertical combustion, flame height and pyrolysis height aren’t stable figures, but the change with time shows that the figures increase firstly and then stabilize. Flame height and pyrolysis height increase with the decrease of specimen’s thickness.

In order to study the vertical countercurrent fire spread of XPS with different widths in the space and wall adhesion conditions, the XPS vertical countercurrent fire spread experiment with different widths was carried out by self-made vertical countercurrent fire test platform. It is found that the spread rate and the average flame height of the XPS decrease first and then increase with the increasing of the width under the two working conditions. After the critical point, the countercurrent spread rate without constraint tends to be stable while the countercurrent spread with one side constraint is greatly accelerated. According to the change of the heat flux on the preheating zone, it is inferred that there are two different heat transfer modes in the two kinds of working conditions. The spread rate of XPS without constraint is mainly affected by gas-phase heat transfer. On the Contrary, The spread rate of XPS with one side constraint is affected by gas-phase heat transfer and solid-phase heat transfer. And with the increase of the width, the solid-phase heat transfer gradually replaced the gas-phase heat transfer to influence the heat-receiving area of the preheating area.

In order to improve cut quality for slot arrays, a new method of laser fine cutting under the consideration of the ratio of vapor to melt is presented. Laser cutting of 6063 aluminum alloy sheet, 0.5 mm in thickness, was carried out on a JK701H Nd:YAG pulse laser cutting system. The effects of vapor‐melt ratio on kerf width, surface roughness and recast layer were studied which relate cutting qualities. Observation on the cut samples with different vapor‐melt ratios (0.687, 1.574, 3.601 varied with laser power increasing, and 1.535, 3.601, 7.661 with decreasing of beam cutting speed) shows that high vapor‐melt ratio improves laser cut quality clearly. Kerf width 0.2 mm of smooth area on kerf top area and thickness 2.03 μm of recast layer are obtained. No dross was found on the kerf bottom and the percentage of the smooth area is up to 40% out of whole kerf side. The research on vapor‐melt ratio provides a deeper understanding of laser cutting and improves laser cut quality effectively.