Dynamic response of a SDOF elastic-plastic system subjected to aircraft impact pulses

In this paper the responses of elastic-plastic SDOF systems subjected to aircraft impact pulses are calculated. The results are compared with simpler pulse models and represented in the useful form of design charts. Two well-known approaches to seismic spectra are examined for the design of aircraft impact spectra.     

Dynamic fracture analysis of a transverse wedge-loaded compact specimen

The J-integral method cannot be applied to the elastic plastic dynamic crack propagation, because unloading and inertia force may take place. From this point of view dynamic elastic plastic scheme using J-integral is developed.Using this dynamic finite element program an MRL type specimen is analyzed. As the result, the property of path-independence of the J-integral under the existence of inertia force and unloading is confirmed. Dynamic effects are considerably small in the MRL type specimen. Also the influence of plastic zone on the crack arrest toughness is shown.Finally the present result is compared with the request of ASTM 2nd round robin test program for crack arrest toughness.     

Dynamic response of a clamped/free hollow circular cylinder under travelling torsional impact loads

Impact-induced vibrations in the casing of a gas centrifuge due to a sudden failure of the spinning rotor (crash) can cause structural disintegrity of the casing. In order to study the influence of the rotor failure behaviour and the impact load histories on the dynamic response of the casing, a simple crash model is proposed in this paper to analyse the transient torsional response due to tangential components of the impact loads. The casing is modeled as a linear-elastic hollow circular cylinder, clamped at the lower end and free at the upper end. The rotor is thought to break up in identical sections in a sequence determined by its fracture behaviour. Each section is assumed to cause an axi-symmetric load distribution at the inner surface of the casing. Therefore the problem is essentially reduced to the analysis of a clamped/free cylinder under travelling torsional impact loads. The problem is solved by representing the impact loads as local pulses acting over the length of the sections. A perturbation method is used to show that the general two-dimensional theory of axi-symmetric torsional wave propagation in circular cylinders, for the problem under consideration, may be approximated by the elementary one-dimensional theory. Solutions are obtained according to the usual modal expansion approach. Measurements of transient torsional responses are shown to be in good agreement with the calculated responses by choosing a suitable shape of the pulses. The effects of travelling velocity and pulse shape are investigated. Finally the transfer of kinetic energy in the rotor to vibrational energy of torsion in the casing is studied.     

电子枪束流截面测量系统

电子枪束流截面测量系统采用单片机控制步进电机驱动测试丝在束流下快速扫描,同时完成束流的数据采集,通过Matlab实现立体图的输出,从而判断电子枪的工作情况。用此系统在5mA束流下进行了测试,得到了束斑直径(13-14mm)和截面束流密度矩阵。     

Dynamic response of target electrons upon low and medium energy ion impact

We found that differential scattering cross sections for medium and low energy He⁺ and Ne⁺ impact on high Z-atoms were significantly enhanced compared with those calculated from the inter-atomic potential based on the Hartree–Fock–Slater atomic model coupled with the bare nuclear charge of a projectile. The enhanced scattering cross sections determined experimentally are reproduced well by a simple model that the center of gravity of target electrons is shifted toward the projectile during a large-angle collision. The shift from the target nucleus is expressed as a function of inter-nuclear distance in terms of a dipole moment (Z₁ and Z₂: atomic numbers of projectile and target, : polarizability, e: electron charge). The effective polarizability β (≡Z₁/Z₂) is expressed as a function of ion velocity v [10⁷ cm/s], in the form β = 0.079 exp[−0.46v].     

Damping of the transverse impulsive motion of a timoshenko beam resting on a thin fluid layer

A discrete model for the one-dimensional incompressible transient axial squeeze potential flow within the thin fluid layer between two adjacent LMFBR sub-assembles caused by the impulsive transverse bending of these beam-type core components is described. The numerical schemes used to determine the time- and space-dependent velocity and pressure fields are outlined. Emphasis is placed on the combined Lagrangian particle/Euler cell approach newly proposed here. In particular two different notions of Lagrangian particles, the convected Lagrangian particle (CLP) and the displaced Lagrangian particle (DLP) are introduced and evaluated. Some remarks on the coupling technique for the fluid—structure interaction are also given. Preliminary results recommend the DLP because of its higher computational efficiency.     

Coupling effects in an elastic-plastic beam subjected to heat impact

The problem of thermally induced vibrations of a simply supported elastic-plastic Timoshenko beam with a linear work hardening is studied. The applied load is a short time thermal flow acting on the upper beam surface. The problem is solved using two models: the joint thermo-elasto-plastic equations and decoupled ones.Numerical results are obtained for three types of heat flow pulse loads (rectangular and two triangular pulses) with different durations and amplitudes. The coupling effects on the transverse beam displacements and on the temperature bending moment are studied. The influence of the pulse shape and pulse duration on the beam response is considered also.     

储存环中快速束团横向尺寸检测器的设计

一种利用可见光的快速束团横向尺寸检测器(Fast Beam Transverse Profile Monitor,FBPM)正在研制过程中,并用于测量快速束流位置和尺寸,该装置将应用到升级改造完成后的合肥光源。FBPM基于日本滨松公司生产的多阳极光电倍增管(Multi-Anode Photo-Multiplier Tube,MAPMT)R5900U-00-L16,它每个通道拥有的有效感光区域为0.8 mm?16 mm,典型上升时间为0.6 ns,因此拥有足够的空间分辨率和时间分辨率。本文介绍了同步光成像系统,设计了低噪声宽带前置放大器,基于光电倍增管4个相邻通道设计了对数处理算法。离线测试结果表明,透镜焦距的测量误差小于?1 mm,放大器带宽达到420 MHz,4个通道相对参考通道2的增益偏差小于0.2 d B,4通道峰值信号偏差不超过2%。     

Dynamic response of reactor internals to pipe breaks

This paper investigates the horizontal responses of the reactor internals to a 14 inch safety injection nozzle break, which is expected to cause the largest loads of the branch line pipe breaks defined for a nuclear power plant. It examines the effects of two forcing terms, reactor vessel motions and internal hydraulic loads, and suggests a new procedure which can be used for tributary pipe break analysis. The analysis result confirms the applicability of the suggested procedure to small size tributary pipe break analysis. Also, this paper calculates the horizontal responses of the reactor internals to a 3 inch pressurizer spray line nozzle break, which is the only one remaining on the primary side after leak-before-break evaluation, and secondary side pipe breaks such as main steam line and economizer feedwater line. The responses are compared with those of safe shutdown earthquake to show that seismic loads with a conservative margin may be used for the pipe break loads in the preliminary design.     

Dynamic response of pipeline conveying fluid to random excitation

An approach was presented to analyze the dynamic response of Timoshenko pipeline conveying fluid under random excitation. Considering the fluid-structure interaction and the effect of shear deformation, the dynamic equation of Timoshenko pipeline conveying fluid was established via the finite element method. The pseudo excitation method in conjunction with the complex mode superposition method was deduced to solve this equation. In the example, the natural frequencies of a cantilever pipeline with different velocities were determined. By the proposed method, the displacement and velocity of pipeline were calculated, and their power spectrum densities and spectral moments were also obtained. Then, the influences of fluid velocities on the natural frequencies and the standard deviation of dynamic response were researched.     

Present status of study on development of materials resistant to radiation and beam impact

Pulsed spallation neutron sources for the materials structure science are severely influenced by beam impact and radiation damage. We have developed the materials strong to these influence since 2004. In this paper, recent topics are described concerning the development of intergranular corrosion (IGC)-resistant austenitic stainless steel for target vessel and window, radiation-resistant ultra-fine grained tungsten materials (W-TiC) for a solid target, CrN film on a tungsten target by means of a molten-salt method, surface treatment of stainless steel for pitting damage in mercury target. Bubble behavior at the interface of mercury and window glass was also observed to clarify the phenomenon of the pitting damage.     

Dynamic behaviour of tunnels under impact loads

Safety related structures of a nuclear power plant are often required to withstand the effects of an aircraft impact load. Underground tunnels, carrying cables and pipes between buildings, also belong to this class of structures. For the design of components located inside the tunnels one must know the response of the structure of the connection points of the components. Acceleration response spectra and relative displacements are of major interest. Using finite element techniques in order to idealize the tunnel and the surrounding soil the effects of the various parameters on the dynamic response of the tunnels are investigated.It is found that some of the main parameters which influence the dynamic response of a tunnel are: soil stiffness and layering, depth of embedment and the thickness of the concrete, protective slab. Vertical accelerations are also affected by the stiffness of the tunnel.     

Non-intercepting electron beam transverse diagnostics with optical diffraction radiation at the DESY FLASH facility

Linear colliders (LCs) and short wavelength free electron lasers (FELs) require ultra-high brilliant electron beams of so much power density that no intercepting device can sustain it. The development of suitable beam diagnostics, non-invasive and non-intercepting, is necessary to measure the properties of such beams.Optical diffraction radiation (ODR) is considered as one of the most promising candidates, as testified by the interest of many laboratories all around the world.An experiment based on the detection of ODR has been set-up at DESY FLASH Facility and it is under operation to measure the electron beam transverse parameters. The radiation is emitted by a high energetic electron beam passing through a sub-millimeter slit, opened on a screen made of aluminum deposited on a silicon substrate. Radiation is then detected by a low noise, high sensitivity CCD camera.We report here the preliminary results for a 680 MeV electron beam energy going through a 0.5 mm slit.     

动态测量强脉冲离子束辐照产生的冲击波

当强脉冲离子束(Intense pulsedion beam,IPIB)辐照材料表面时,在靶材料表面引发快速升温、熔融、气化、烧蚀以及随后的快速固化,并产生热应力与冲击波.本文通过构建并改进以聚偏二氟乙烯(Polyvinylidenefluoride,PVDF)膜为核心的测量系统,成功地对强脉冲离子束辐照所产生的冲击波进行了动态的探测,实验测量与我们自行开发的理论模拟计算相比较,获得较好的吻合.     

Numerical studies of impact on reinforced concrete beam of hard missile

The safety design of concrete containment structures in nuclear power stations has thus far covered only accidents due to internal pressure, temperature loading and earthquake loading. Recently, designers and researchers have become interested in the important effects of the impact load of a projectile on nuclear power stations. This paper develops an FEM model for analyzing the collision of a hard missile against reinforced concrete structures and compares the results with impact tests conducted at our institute.     

Dynamic structural response of LMFBR head closures to hypothetical core disruptive accidents

Presented here is an investigation of the dynamic structural response of the primary vessel's head closure to a hypothetical core disruptive accident (HCDA). Two head-closure designs were considered: the first represents a loop-type design and the second represents a pool-type design. Using representative configurations of liquid metal fast breeder reactors (LMFBR), independent models were used (1) to derive loading pressure histories and (2) to study the structural response of the head closures. Results for loading pressures, displacement histories, deformed profiles, stress magnitudes and plastically deformed regions are presented.