共查询到18条相似文献,搜索用时 140 毫秒
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含对流与蒸发表面的有限厚度材料的双曲型热传导分析 总被引:3,自引:0,他引:3
本文对于含有对流与蒸发表面的有限厚度材料,在遭受一脉冲表面热流作用时的双曲型热传导进行了分析,采用热势函数描述的双曲型热传导方程来描述该问题,并用有限差分法进行数值求解.同时,本文还就表面对流与蒸发对材料表面与内部瞬态温度变化的影响以及材料双曲型热传导对表面蒸发的影响进行了分析. 相似文献
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采用双重分布函数的格子玻尔兹曼模型,对单脉冲激光金属打孔过程中的快速相变传热进行研究.模型考虑了金属材料熔化后熔体的流动换热,并采用浸没移动边界方案对过程中的固液界面进行追踪.采用纯导热模型和考虑对流的换热模型计算,将结果和试验进行对比,结果表明:在激光打孔过程中熔体的流动对相变传热产生较大影响,采用考虑流动换热模型的结果与实验更接近.进而对熔化速度、熔化深度以及温度场的变化进行分析,并探讨不同激光工艺参数对相变过程的影响.模拟发现一个脉冲结束后,激光的脉宽越大,孔深越小,孔径越大,且最高温度较短脉冲激光越低. 相似文献
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利用高重复频率(1kHz)、吉瓦级飞秒激光脉冲实验验证了高强度飞秒脉冲在空气中的自 压缩现象,研究了入射脉冲在不同初始啁啾情况下经空气中聚焦成丝后,时域及频域特性随 入射脉冲能量的变化规律.实验结果表明,在无需后继色散补偿情况下,高强度飞秒脉冲仅 通过在空气中的非线性传输过程就可以实现脉冲压缩;在入射脉冲为负啁啾情况下,实验观 察到脉冲光谱及时域宽度同时得到压缩,并可获得比激光源所能提供的更短的近双曲正割型 变换限脉冲.
关键词:
高强度飞秒激光脉冲
自压缩
自聚焦 相似文献
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激光加热物体的三维模型计算 总被引:5,自引:4,他引:1
将物体的热传导系数、比热容、密度、物体对激光的吸收系数考虑成温度的函数,并考虑到物体向周围空间有热辐射和对流换热交换能量等情况下,用控制容积法对激光加热物体作三维真实边界的计算分析.这一结果在激光加热物体温度场的计算上有广泛的实用性. 相似文献
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提出了描述整个飞秒多脉冲激光烧蚀过程的物理模型,模型考虑了多脉冲烧蚀的新的特点,考虑靶材吸收率随温度的变化和蒸发效应,建立了激光烧蚀不同阶段的热传导方程,给出了相应的定解条件。以金靶材为例,利用有限差分法,求解了热传导动力学方程,分别给出单脉冲和多脉冲作用下相应的靶材电子和离子亚系统的温度演化图像,及多脉冲激光作用下能量剩余系数和脉冲个数的变化规律,发现理论曲线与相应的实验数据吻合较好。研究结果充分证明多脉冲激光烧蚀过程中剩余能量的存在。 相似文献
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In the present study, the hyperbolic heat conduction equation is derived from the Boltzmann transport equation and the analytical solution of the resulting equation appropriate to the laser short-pulse heating of a solid surface is presented. The time exponentially decaying pulse is incorporated as a volumetric heat source in the hyperbolic equation to account for the absorption of the incident laser energy. The Fourier transformation is used to simplify the hyperbolic equation and the analytical solution of the simplified equation is obtained using the Laplace transformation method. Temperature distribution in space and time are computed in steel for two laser pulse parameters. It is found that internal energy gain from the irradiated field, due to the presence of the volumetric heat source in the hyperbolic equation, results in rapid rise of temperature in the surface region during the early heating period. In addition, temperature decay is gradual in the surface region and as the depth below the surface increases beyond the absorption depth, temperature decay becomes sharp. 相似文献
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A hyperbolic model of non-Fourier heat conduction with non-uniform heat source is used to simulate the transient heat transfer in a high-pulse-pumped solid-state laser medium. The temperature fields are numerically analysed using the finite difference method combined with the TDMA algorithm for different pump power densities, pulse durations, thermal relaxation time and cooling intensities, respectively. The calculated results are compared with those predicted by the parabolic heat conduction model based on the Fourier law. The results indicate that the non-Fourier heat conduction phenomenon in laser media should be considered when the pump power density exceeds 104 W/m^2 or under low pulse duration. In addition, the conditions of non-Fourier effects and their influencing factors are analysed. 相似文献
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研究了半导体材料对激光的吸收机制。运用一维热传导方程以及载流子耦合扩散方程研究了激光与半导体材料相互作用的热输运、自由载流子输运过程。分析了半导体材料的热学损伤、力学损伤,以及光电探测器的击穿损伤机制。应用数值模拟的方法对Nd:YAG脉冲激光(1.06μm)辐照下感兴趣的半导体材料PbS内部瞬时温度场分布进行了模拟。 相似文献
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In picosecond ultrasonics experiments the absorption of a femtosecond laser pulse in a thin metallic transducer is used to generate very short acoustic pulses. These pulses are made of coherent longitudinal waves with a frequency spectrum that can reach 100-200 GHz. The laser pulse absorption gives rise to a heating of the film of a few Kelvin within a typical time of 1 ps. Later on, the heat goes in the substrate through an interface thermal resistance and is diffused by thermal conduction. At very low temperature and in pure crystals the thermal phonons emitted by the heated metallic film can propagate ballistically over large distances and produce a so-called heat pulse. We report on the experimental evidence of the coexistence of the coherent acoustic pulse and the incoherent heat pulse generated and detected by laser ultrasonics. 相似文献
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超快脉冲激光辐照金属薄膜热-力效应的模拟研究 总被引:4,自引:4,他引:0
基于双曲双温两步热传导和热电子崩力模型,考虑到超快脉冲激光辐照金属薄膜材料过程中的热-力耦合效应,得到了完全耦合的、非线性的超快热弹性模型.运用具有人工粘性和自适应步长的有限差分算法,以脉宽为100 fs的脉冲激光辐照200 nm厚金膜为例,对薄膜体内的电子-晶格温度及温度梯度、热应力和电子热流进行了数值模拟研究.结果表明:脉冲辐照早期为明显的非平衡加热阶段,同时形成较大的热电子崩力;电子热流出现双峰现象;超快加热引起的热应力是导致薄膜力学损伤的主要原因. 相似文献