材料热力学作业

absorption coefficient is larger than normal temperature, absorption of laser energy more. Considering the shell material on the laser absorption coefficient under different temperature change, can more accurately predict under laser irradiation of laser absorption coefficient change, can more accurately predict the temperature of the shell under laser irradiation field, in the back of the numerical calculation of this revised to reflect the absorption coefficient of incident laser power density.

According to the distribution of the beam symmetry and symmetry model loading mode, the model is simplified to a quarter part, and the model reasonable pressure load, define the symmetric boundary conditions. Cylindrical shell model USES the entity unit, along the direction of the shell thickness divided eight units to ensure that the direction of the thickness of temperature calculation accuracy. Due to large scale model calculation, finite element unit optimized, so need to ensure the beam irradiation area and surrounding have sufficient number of units. Calculation process includes two steps, first of all for laser heat flux cylindrical shell under the action of transient thermal analysis, and calculate some irradiation moment in the thermal stress distribution of cylindrical shell structure.

2 Thermodynamic response pressurized cylindrical shell under laser irradiation

Different beam irradiation after 1.0 s column temperature field distribution on the surface of the shell under uniformly distributed beam spot internal temperature is almost the same, on the edge of the light spot trends.

Fig.5 Temperature distributions of cylindrical shell under different laser beam

temperature have mutations in gaussian beam, makes the facula center highest temperature in the flare edges smooth transition temperature, super gaussian beam as N increases, shell temperature change trend gradually by gaussian situation to the uniform change. Beam fill factor of small beam spot local area rapid heating, materials at high temperature on the laser absorption coefficient is bigger, so to further accelerate the temperature rising rate of strong laser area materials.

Beam intensity distribution differences led to the shell flare internal heating efficiency, and affects the thermal stress distribution. The toroidal shell stress distribution under different beam irradiation had a great influence on the stress distribution, stress of the gaussian beam on the edge of the light spot, no obvious mutations in the uniform beam with mutations in the stress on the edge of the light spot trends. Super gaussian beams, with the increase of N stress distribution trend with gaussian situation to the uniform change. Spot center stress value is not big, this is mainly

because facula center temperature is higher, the material into plastic state in advance.

Fig.6 The hoop stress distribution of cylindrical shell under differen laser beam

Pressurized cylindrical shell and the displacement reaction of the thermal deformation of cylindrical shell, the damage morphology is of great significance for predicting the column shell. As beam fill factor since the childhood, the expansion of the facula center displacement also from large to small, the gaussian beam to shell bulge is most serious, and evenly distributed beam on the spot close to the expansion of the internal displacement, super gaussian beams caused by displacement between the two. Gaussian beam will lead to first failure), and evenly distributed beam shell overall failure can lead to light irradiation area, cause the burst of large area.

3 conclusion

The author USES the numerical method to study the thermal response of the pressurized cylindrical shell under laser irradiation, the results show that the thermodynamic behavior of beam intensity distribution on ChengLiZhu shell has an important influence, fill factor small laser light beam will lead to local by rapid heating shell, early into the plastic state, which leads to the local damage occurred in advance, and the intensity of the speed of light, close to the uniform distribution of light beam to shell uniform heating, and make the spot edge shell temperature, stress and displacement mutation. So the intensity distribution differences will lead to the pressurized cylindrical shell with different thermodynamic response, shell and affect the final failure mode and failure moment.