基于流固耦合的弹载电子设备瞬态热仿真分析方法

在导弹飞行过程中由于工况环境剧烈变化,其整流罩蒙皮温度和热载荷急剧变化,这将对导弹的作战性能产生重大影响。为保证弹载电子设备的设计满足精度要求,提出了一种基于流固耦合非定常数值模拟的设计计算方法。针对弹载电子设备在高速运行过程中的瞬态热载荷是一个典型流固耦合问题,通过求解流体与固体表面的热传递方程,计算获得流场内各点的能量分段函数。运用MATLAB软件计算拟合出流场每块结构微元对应的瞬态功率曲线分段函数,采用将功率曲线分段函数加载至Fluent的热仿真分析方法,直观预测整个弹载电子设备的工作温度及其环境温度的瞬态变化。通过对某型号反辐射导引头及其弹载电子设备气动加热问题进行具体计算分析,获得了该型号装备在各个时刻流场内导引头及其弹载电子设备的瞬态温度空间分布,所得结果与实际有较好的吻合度。结果表明该方法对同类电子设备的瞬态热分析和相应散热设计具有一定参考作用。     

高抗ESD瞬态电压抑制器的研究

瞬态电压抑制器是一种用来保护芯片的分立器件,它能有效避免芯片受到高能瞬态脉冲的损坏。目前,静电损伤已经成为造成电子设备损坏的一个主要因素,为了能更好更有效地保护芯片,需要瞬态电压抑制器将高能脉冲钳位在一个对其本身和芯片都没有损伤的电位下,同时尽快将电流通过瞬态电压抑制器自身泄放掉。本文通过结构设计的改进,对一种常用的平面结构单向瞬态电压抑制器的反向三极管进行优化,通过TLP测试,并结合Tsuprem4、Medici的模拟和理论分析显示,这种改进方法使得瞬态电压抑制器具有了更强的抗静电放电的能力,从而可以更好地保护电子设备。     

圆锥薄壳体瞬态动力响应分析

运用有限元分析软件ANSYS／LS-DYNA对在余弦脉冲载荷作用下某圆锥薄壳体的瞬态动力响应过程进行分析，得出了不同时刻下壳体等效应力场的分布，考察了该壳体结构的动强度性能。同时通过对一些典型节点位移、速度和应力响应曲线的分析，归纳总结出了在余弦脉冲加载条件下圆锥薄壳体瞬态响应的规律，对该壳体的结构设计和改型提出了合理化建议，并定性地分析了该脉冲加载对壳体内部电子设备的影响。最后，将理论计算和试验结果进行对比分析，验证了计算模型的正确性。     

关于EFT试验中容性耦合夹使用的注意事项

本文结合耦合原理对进行群脉冲(EFT)实验时使用容性耦合夹的注意事项进行分析讨论,并得出在使用耦合夹的EFT实验中,使用退耦钳的重要性,对EFT试验现行的标准IEC61000-4-4:2012[1]中的容性耦合夹使用条款给出改进建议。     

某系留气球锚泊车车载电子设备电磁兼容性设计

本文结合某系留气球锚泊车车载电子设备具体案例，分析了锚泊车车载电子设备内、外部干扰因素，并针对各干扰因素提出了电源线滤波、天线近场分布计算、电缆布线、机箱屏蔽以及设备接地等电磁兼容设计策略。     

数字示波器在尖峰干扰脉冲强度测量中的应用

运用数字示波器瞬态捕获能力及面积测量功能,快速、准确、不遗漏地测量电子设备的尖峰干扰信号(脉冲信号),用公式将脉冲强度单位换算为脉冲频谱密度单位。     

干耦合超声波激励信号研究

为保证干耦合超声波探头的正常工作,采用理论分析与实验相结合的方法对其激励信号进行选择。干耦合超声波探头与试件直接接触,入射能量低,不同粘接状况下接收信号能量(E)差异较大,品质因数(Q)能够表征接收信号的带宽及强度分布,两者可作为激励信号的选择依据。根据各信号表达式分别采用方波、锯齿波及高斯窗、海明窗和汉宁窗调制的正弦脉冲信号进行试验。试验结果表明:在重复频率和电压幅值不变的条件下,对于玻璃纤维/丁腈橡胶复合材料粘接板,最优激励波形为5周期汉宁窗调制正弦波脉冲信号,激励频率约为100 k Hz,为干耦合超声波探头的检测应用提供基础。     

车载电子设备抗振设计研究

随着军工技术的不断发展,车载电子设备越来越多的被应用到军事领域,但由于工作环境恶劣,设备在运输或工作过程中常受到振动的干扰,影响设备的性能,为保证设备的可靠性和寿命,必须加强对车载电子设备的抗振设计。分析机械振动对车载电子设备的影响,并从电子设备的加固设计和隔振缓冲设计两个方面提出提高军用电子设备抗振性能和使用寿命的策略。     

浅谈桥丝式电火工品瞬态脉冲试验的研究现状

文章主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状.包括试验仪器、热参数计算和分析的进展,以及瞬态脉冲试验在电火工品质量检测中的作用.收集并分析了瞬态脉冲试验的应用范围和局限性,结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势.     

灼热桥式电火工品瞬态脉冲试验的现状和趋势

主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状,包括试验仪器、热参数计算和分析的进展;同时介绍了瞬态脉冲试验在电火工品质量检测中的作用;并讨论了现在瞬态脉冲试验的应用范围和局限性;结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势。     

Energy transfer induced by femtosecond two-beam coupling in two Kerr liquids

Femtosecond two-beam coupling is demonstrated in N,N′-dimethylformamide and dimethyl sulfoxide by using a time-resolved pump-probe system at a wavelength of 800 nm. As the temporal delay between pulses is varied within the coherence time, transient energy transfer from one pulse to another occurs. Because of the asymmetry of the normalized transmittance, two-photon absorption is considered in the two liquids. A theory based on two-beam coupling in perpendicular linear polarization is used to interpret the experimental results. Good agreement is obtained between the theory and experiment. Moreover, by introducing a valuable variable, the ratio of the relaxation times of the two Kerr liquids is directly characterized.     

Laser Pulses Shortening at Transient Backward SRS and Forward Scattering Suppression

Abstract

Mathematical simulation of the transient SRS process is performed taking into account backward scattering and Stokes-anti-Stokes parametric coupling of the forward waves. It is shown that the parametric coupling has a slight influence on the suppression of forward scattering. A main contribution to the SRS asymmetry is made by pumping exhaustion by the backward Stokes waves. The dynamics of scattering radiation formation is studied and the conditions for obtaining high-contrast pulses at SRS compression are formulated.     

Coherent transient optical signal processing without brief pulses

The temporal processing operations of convolution and correlation are demonstrated through optical coherent transient techniques, in which two long, low-intensity frequency-chirped pulses replace the single, brief reference pulse of a traditional three-pulse excitation sequence (brief pulse, pattern pulse, and data pulse). Here, a four-pulse excitation sequence is used (two frequency-chirped pulses, pattern pulse, and data pulse) in which the particular order and timing of the chirped pulses with respect to the other waveforms determine the processing operation. An experiment is performed with biphase-coded pattern and data pulses to demonstrate both the correlation and the convolution operations. A new atomic rephasing process that we call delayed rephasing is demonstrated.     

载荷脉宽对圆柱壳瞬态响应的影响分析

为认识载荷脉宽对圆柱壳瞬态响应及其对X射线冲击响应模拟等效性的影响规律,定义了等效性评价指标即平均应变差异。以四种不同尺寸的典型圆柱壳为对象,分别加载六种冲量相同、脉宽不同的三角形脉冲载荷,通过数值模拟,获得了平均应变差异Δε随脉宽变化的关系,从结构特性角度分析了变化的原因。发现Δε主要受t/τ(脉宽占比)控制,t/τ≤0.45时,平均应变差异在20%以内。所得结果可为模拟X射线冲击环境的试验设计、结果评估和数值模拟提供参考。     

Phase-transitions in GeSb induced by customized ultrafast optical pulses

The use of ultrafast laser pulses to initiate solid-state phase-transitions in certain materials has shown promise in achieving sub-nanosecond phase changes with different optical properties. These phase changes have been well studied using pulse durations between femtoseconds and nanoseconds to determine the dynamics for the reversible phase changes on multiple time scales. In this study femtosecond pulse shaping techniques, driven by evolutionary algorithms, were used to obtain optimized temporally shaped ultrashort laser pulses to induce and control permanent phase changes in GeSb thin-films. Through monitoring the pulse effects it has been determined that the crystalline-to-amorphous phase transition is minimized using optical pulses with pulse widths less than the electron-phonon coupling time. It is maximized by using pulses longer than the time required for energy transfer from the excited carriers to the lattice.     

Pulse shape effects on the dynamic stress intensity factor

The interaction of a transient stress pulse with a penny-shaped crack embedded in an infinite elastic solid is investigated. The front of the incident stress pulse is assumed to be planar and parallel to the crack surfaces. A time-domain boundary integral equation method is applied for computing the time history of the crack opening displacement, from which the time dependence of the dynamic stress intensity factor is subsequently calculated. Numerical calculations are carried out for several stress pulses of different shape and time dependence, to explore the effects of the shape, duration, rise and descent time of a transient stress pulse, or the period and the mean stress of a cyclic stress pulse on the dynamic stress intensity factor. Implications regarding crack surface penetrations or crack surface interactions caused by certain stress pulses are also discussed.     

Ultrafast transient generation of spin-density-wave order in the normal state of BaFe2As2 driven by coherent lattice vibrations

The interplay among charge, spin and lattice degrees of freedom in solids gives rise to intriguing macroscopic quantum phenomena such as colossal magnetoresistance, multiferroicity and high-temperature superconductivity. Strong coupling or competition between various orders in these systems presents the key to manipulate their functional properties by means of external perturbations such as electric and magnetic fields or pressure. Ultrashort and intense optical pulses have emerged as an interesting tool to investigate elementary dynamics and control material properties by melting an existing order. Here, we employ few-cycle multi-terahertz pulses to resonantly probe the evolution of the spin-density-wave (SDW) gap of the pnictide compound BaFe(2)As(2) following excitation with a femtosecond optical pulse. When starting in the low-temperature ground state, optical excitation results in a melting of the SDW order, followed by ultrafast recovery. In contrast, the SDW gap is induced when we excite the normal state above the transition temperature. Very surprisingly, the transient ordering quasi-adiabatically follows a coherent lattice oscillation at a frequency as high as 5.5 THz. Our results attest to a pronounced spin-phonon coupling in pnictides that supports rapid development of a macroscopic order on small vibrational displacement even without breaking the symmetry of the crystal.     

电火工品瞬态脉冲试验无损性研究

通过电点火头的对比试验研究了瞬态脉冲试验对电火工品发火性能的影响,试验结果表明,由于瞬态脉冲试验电流较小,对电火工品的性能没有显著影响,且是无损的.     

Heat pulse transmission from sodium fluoride into helium I

Heat pulse transmission across a NaF-He I interface reveals behavior not observed at a He II interface. Longitudinal and transverse crystal modes are resolved at the detector with the longitudinal pulse exhibiting a unique characteristic structure. The detected longitudinal pulse appears with an initial overshoot lasting about 100 nsec and a reduced rear portion lasting the duration of the input pulse. The initial overshoot component echoes repeatedly between opposite surfaces of the crystal, and is indicative of the small transmission predicted by the acoustic mismatch theory. No echoing of the rear portion has been observed, and apparently the rear portion has a different coupling process at the interface. For the transverse pulse, a change in shape and a delay in arrival time are noted upon transmission into liquid, suggesting that certain portions of the pulse are not transmitted. Measurements of the amplitude dependence of the various pulses are made, and compared with a model having a frequency-selective coupling at the interface.     

灼热桥式电火工品瞬态脉冲试验的现状和趋势

主要介绍了近年来电火工品瞬态脉冲试验在国内外的发展现状,包括试验仪器、热参数计算和分析的进展;同时介绍了瞬态脉冲试验在电火工品质量检测中的作用;并讨论了现在瞬态脉冲试验的应用范围和局限性;结合现有的仪器和软件,展望了瞬态脉冲试验今后在硬件和软件方面的发展趋势。