【作者】 林鹏；

【导师】 王肖钧； 林俊德；

【作者基本信息】 中国科学技术大学 ， 工程力学， 2007， 博士

【摘要】 本文围绕强脉冲X射线和电子束辐射产生的热—力学效应（即材料响应和结构响应），采用实验研究、理论分析和数值计算等方法进行了比较系统全面的研究，主要工作包括以下几个方面：（1）总结了能量沉积的计算方法，给出了电子能量沉积的解析计算公式。脉冲束流在材料中的能量沉积，是产生热—力学效应的基础和前提。首先，按照朗伯定理计算了软、硬X射线在新型碳酚醛和玻璃钢中的能量沉积。计算得出：软X射线的沉积峰值高，沉积深度浅；硬X射线的沉积峰值相对要低得多，但是穿透要更深。其次，根据连续慢化理论和单次大碰撞理论，用蒙特卡罗方法计算了电子在物质中的能量沉积，并给出了电子能量沉积的解析计算公式。最后，对一种多层结构在电子束和X射线辐射下的能量沉积特性进行了计算分析，结果表明该多层结构不仅能有效防护X射线的辐射，而且对低能强流电子束辐射也能提供有效防护。（2）推导了一种新的辐射自由面格式，采用弹塑性流体动力学模型对X射线和电子束辐射产生的热激波效应和冲量效应进行了数值模拟计算，并给出了一维辐射热激波的峰值衰减解析计算公式。基于Taylor展开，推导出了一种新的高精度的辐射自由面格式，与传统自由面格式相比，在X射线辐射热—力学效应计算中，可以提高计算精度。以冲击Hugoniot方程为基础，根据波传播过程中的不可逆能量损耗，推导出了辐射热激波传播衰减的解析计算公式，利用该公式对材料的热激波衰减行为进行了分析，并与Langley公式进行了计算对比，两者符合较好。对软、硬X射线在材料中的辐射热激波效应进行了计算。软X射线能量沉积较浅，热激波的产生机制主要为表面物质的汽化喷射；硬X射线能量沉积较深，热激波的产生机制主要为热膨胀。对强脉冲X射线辐射Ly-12铝产生的喷射冲量进行了数值计算，并与实验测量结果进行了比较，两者符合较好。（3）研制了两套热激波测量系统和两套冲量测量系统，并进行了辐射热激波效应和喷射冲量效应的实验研究，得到了一些有价值的数据。大尺寸的石英压电晶体热激波探头，可满足10mm左右厚度的复合材料热激波的测量要求。PVDF热激波探头可测量辐射热激波在传播路径上的衰减。红外通光冲量探头适用于电子束和软X射线的喷射冲量测量。对Ly-12铝的电子束辐射实验表明，对于靶上平均能通量为187～196J／cm²，厚为2～5mm的Ly-12铝靶，实测热激波平均应力峰值为1.65～0.97GPa。在电子束能通量约为570～970J／cm²，对厚度为10mm的三维编织复合材料，其热激波应力峰值为0.15～0.39GPa左右，只有相同条件下Ly-12铝的6％左右。实验得出电子束辐射三维编织复合材料产生冲量的能通量阈值为77J／cm²。在电子束能通量F为101～297J／cm²范围内，三维编织复合材料的喷射冲量耦合系数β为0.20～0.62Pa·s／（J／cm²）。在F为181～312J／cm²范围内，Ly-12铝的β为1.45～1.69Pa·s／（J／cm²）。三维编织复合材料的β值只有Ly—12铝的1／3左右，这说明三维编织材料具有良好的抗辐射性能。软X射线冲量实验得出：在平均能量为0.30keV、平均半高宽为43ns的脉冲软X射线作用下，对白漆A、灰漆B、玻璃钢和Ly-12铝，在平均能通量分别为147J／cm²、135J／cm²、123J／cm²和137J／cm²时，它们的冲量耦合系数分别为0.42、0.45、0.75和0.54Pa.s／(J.cm^-2)。对一种多层结构材料进行了电子束辐射热激波实验测量，结果表明，该多层材料能有效防护100卡／cm²的电子束辐射。（4）对柔爆索（MDF）余弦冲量分布加载进行了设计和实验验证，并进行了结构响应实验研究。通过设计柔爆索离圆柱壳表面的距离以及柔爆索之间的间距，可以得到柱壳表面环向呈余弦分布的冲量载荷。通过在圆柱壳环向不同位置的冲量测量，得出冲量余弦分布的最大偏差大约为10％。成功测得了圆柱壳内表面几个位置处的环向应变信号。在设计峰值比冲量为506Pa.·s的余弦载荷作用下，实验圆柱壳在受载面-π／3～π／3范围内，可观察到明显动塑性屈曲现象。（5）对两端固支、长径比为2的铝合金圆柱壳在余弦冲量分布载荷加载下的结构响应和动塑性屈曲进行了计算模拟。数值模拟表明，辐射脉冲载荷引起的动塑性屈曲发生在受辐射面的—π／3和π／3之间，与实验结果相符。更多还原

【Abstract】 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 -π/3 toπ/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 -π/3 toπ/3 at the loaded side of the shell, and it accords well with experiment.更多还原