The Studies Of The Thermo-Mechanical Effects Induced By Pulsed Beam Radiation

The thermo-mechanical effects induced by pulsed beam radiation have been studied systematically based on the experiment, theoretical analysis and numerical simulation. The primary contents are as follows:(1) We summarized the calculating methods of energy deposition in beam radiation, and especially derived an analytical formula to calculate the electron's energy deposition which is the basis in the study of thermo-mechanical effects. Firstly, we calculated the energy deposition in C/Ph and GFRP with Lombard theorem and the results showed that the peak value of energy deposition from soft X-rays is higher than that from hard X-rays, but the depth of energy deposition results from soft X-rays is much less than that from hard X-rays. Secondly, we calculated the electron's energy deposition with Monte Carlo method and analytical formula respectively. Monte Carlo method is used in the energy deposition according to the single collision and continuum slowing theorem and the analytical formula for calculating electron's energy deposition is derived. Finally, we studied the energy deposition characteristics of one kind of multi-layered material induced by X-rays and electron beam radiation. The results show that the multi-layered material can not only provides effective protection from X-rays radiation, but also can provided protection from electron beam radiation.(2) A new kind of numerical scheme to simulate the irradiation free surface is proposed by Taylor expansion, the thermal shock wave and blow off impulse effects induced by X-rays and electron beam radiation are studied by numerical simulation based on uniaxial strain elastic-plastic hydrodynamics model, and an attenuation formula of the amplitude of the thermal shock wave is derived. The new free surface scheme, which is a fourth order accuracy, is more suitable than Richtmyer's for solving thermal mechanical effects of material irradiated by X-rays. According to irreversible energy dissipation, the thermal shock wave's amplitude attenuation formula is proposed based on the Hugoniot equations. The calculating results using this analytical formula agree well with those from Langley formula. The thermal shock wave effects in material subjected to soft and hard X-rays radiation are simulated and different mechanism of thermal shock wave is revealed: the thermal shock wave induced by soft X-rays is from the removal of vaporing material and it is from thermal expansion when induced by hard X-rays. Finally, the blow off impulse in Ly-12 aluminum subjected to intense pulsed X-rays is simulated and the calculating results accord well with the experimental data.(3) Two sets of thermal shock wave measuring systems and two sets of blow off impulse measuring systems are developed. The guard-ring piezoelectric quartz measuring system is suitable for the composites with about 10mm thickness and the transducer using PVDF is suitable to the study on peak attenuation of the thermal shock wave in its propagating routes. The light transducing impulse probe is suitable to the measurement of impulses induced by electron beam or X-rays.The experimental studies of the thermal shock wave induced by electron beam are discussed. The target material is Ly-12 aluminum alloy with the thickness of 2～5 mm. The range of energy fluxes on target is 187～196 J/cm² and experimentally measured stress peaks of the thermal shock wave is 1.65～0.97 GPa.The 3-D braided composites (3DBCP) possess good property which can attenuate thermal shock waves. When electron beam energy fluxes were in the range from 570 to 970 J/cm², for 3DBCP with thickness of 10mm, the peak stresses of thermal shock wave were in the range from 0.15 to 0.39 Gpa. These values only were approximately 6 % that of Ly-12 aluminum alloy under identical conditions.The threshold flux used for producing blow off impulse in 3DBCP is about 77 J/cm². When electron beam energy fluxes were in the range from 101 J/cm² to 297 J/cm², for 3DBCP, the coupling coefficients of blow off impulse were in range from 0.20Pa. s/ (J·cm^-2) to 0.62Pa. s/ (J·cm^-2). These values only were approximately 1/ 3 that of LY-12 aluminum alloy under identical conditions. These show that 3DBCP possess good property which can reduce blow off impulses.The experimental studies on the impulse induced by soft X-rays show that: under the radiation of X-ray with mean energy (E=0.30keV) and time duration (43ns), the mean coupling coefficient of the blow off impulse of paint A is 0. 42 Pa. s/( J·cm^-2 ) at the mean energy flux of E_?, = 147 J/cm², the corresponding coefficient of paint B is 0. 45 Pa. s/( J ? cm^-2) at the mean E_? = 135J/cm², the corresponding coefficient of GFRP is 0. 75 at the mean E_?= 123J/cm² , and 0. 54 Pa. s/( J ? cm^-2 ) for Ly-12 aluminum at the mean E_? 125 J/cm².Propagation behaviors of thermal shock wave in one kind of multi-layered material subjected to pulsed electron beam were studied. The experimental results show that it can provide protection from electron beam with energy flux of 100cal/cm². (4) The optimization design are applied to obtain a mild detonating fuse (MDF) impulse which has a nearly cosine distribution around the shell, and the experimental validation is carried out to prove the cosine distribution of impulse around shell. The structural responses of cylindrical shell are experimental studied with the loads from MDF. By designing the spacing between the MDF strands and the standoff distance from the strands to the shell, the MDF impulse, which has a nearly cosine distribution around the shell, are obtained. The maximum deviation between the impulses at several positions measured by impulse transducer and the impulses, which has a cosine distribution around the shell, is less than 10%. The strain signals at different positions produced by MDF loads are successfully recorded. The obvious dynamic plastic flections appear in ranges from -Ï€/3 toÏ€/3 at the side of the shell where the impulse, which has a cosine distribution and its peak value is 506 pas, is loaded.(5) The structure response and the dynamic plastic flections of the cylindrical shell made from Ly-12 aluminum with two ends fixed are simulated. The dynamic plastic flections appear in the range from -Ï€/3 toÏ€/3 at the loaded side of the shell, and it accords well with experiment.