基于虚拟仪器的瞬态爆炸参数测试系统

瞬态爆炸参数测试系统是研究粉尘、气体爆炸机理的主要测试系统,其中传感器的可靠性、测试系统的灵活性是爆炸参数系统研究的热点和难点.本文开发了基于虚拟仪器的爆炸参数测试系统,并自制了K型热电偶作为温度测试传感器,压力测试采用Kistler 211M0160型传感器.构建了瞬态爆炸参数测试系统,同时编写了爆炸测试系统程序框图.使用5 L爆炸罐测试了甲烷气体爆炸参数,通过试验验证了构建的瞬态爆炸参数测试系统能够满足爆炸参数的测试要求,为研究粉尘、气体爆炸参数提供了仪器设备.

有限空间爆炸瞬态温度的动态补偿方法研究

为改善铠装绝缘型热电偶的动态特性,采用集总热容法建立了热电偶传热模型,将其系统特性简化为一阶惯性系统。为验证系统阶次的合理性并确定传递函数参数,建立了最小二乘支持向量机系统辨识模型。采用高温油浴法进行了热电偶动态标定实验,基于动态标定数据和粒子群优化算法,建立了热电偶动态补偿模型。实验结果表明:由集总热容法和系统辨识模型确定的系统传递函数能够较为准确的描述铠装绝缘型热电偶的动态特性,传递函数在阶跃激励下的响应曲线与动态标定实验中传感器的输出曲线具有较高的一致性;基于粒子群优化算法的动态补偿模型表现出较好的补偿效果,经补偿后系统响应时间由7.124 s减小为1.187 s,且传感器工作频带得以有效扩展。将该方法应用于有限空间爆炸瞬态温度的动态补偿中,能够在一定程度上减小传感器的动态测量误差。

锅炉热态爆炸能量的实验研究

介绍了国内首次对三种材料（钢、铸铁及铝）制成的大量不同锅炉模型进行的热态爆炸实验并得出实际爆炸能量相对绝热等熵过程爆炸能量的偏离值,据此可对锅炉爆炸原因进行有根据的分析。另外,从数量上揭示了对爆炸能量的影响因素,还定性地得出铸铁片式锅炉属于非爆炸型的重要结论。

低失真爆炸冲击信号零漂分析和处理方法

短时的爆炸瞬态冲击信号,具有冲击频带宽、幅值高特点,在测试过程中,常常会有信号失真的零漂现象。本文中详细分析零漂现象产生的原因,对比各种修正方法的优缺点,提出基于经验模态分解(empirical mode decomposition,EMD)改进高效算法,结合频域窗函数滤波方法,这种新修正方法,能够较好弥补现行修正方法的缺陷,可为瞬态冲击信号时域模拟提供失真较小的环境条件数据。

钛-钢爆炸复合板的热轧制

本文叙述热轧工艺对钛-钢爆炸复合板的成分、组织和性能的影响。试验指出,该复合板的热轧应在不高于850℃的温度下加热并以较大的压下率进行轧制。

基于红外辐射的爆炸火焰温度补偿测算技术

应用辐射测温法进行爆炸火焰温度测试时,火焰发射率取经验定值的方法与火焰燃烧机理存在较大的偏差,同时测点距离与环境温湿度也会导致不同程度的热辐射衰减,从而影响爆炸火焰温度的测量精度。本文针对上述两个问题,基于大气辐射理论与光学传播规律,提出了辐射路径衰减补偿模型,结合由红外热像仪和比色测温仪测量的爆炸火焰动态发射率,对爆炸场火焰真温进行联合反演,并将测算结果与比色测温仪测得的火焰表面温度进行对比,得到了反演温度误差范围。试验结果表明,利用本文所提出的补偿模型测算得到的爆炸火焰温度,误差由补偿前的55.699%-89.847%降低到11.292%-59.077%,有效提高了外场爆炸瞬态火焰温度的测算精度。

Theoretical analysis of ultra-short pulsed laser ablation of SiO_2 material based on a Coulomb explosion model

Based on the kinetic theoretical Vlasov-Poisson equation, a surface Coulomb explosion model of SiO2 material induced by ultra-short pulsed laser radiation is established. The non-equilibrium free electron distribution resulting from the two mechanisms of multi-photon ionization and avalanche ionization is computed. A quantitative analysis is given to describe the Coulomb explosion induced by the self-consistent electric field, and the impact of the parameters of laser pulses on the surface ablation is also discussed. The results show that the electron relaxation time is not constant, but it is related to the microscopic state of the electrons, so the relaxation time approximation is not available on the femtosecond time scale. The ablation depths computed by the theoretical model are in good agreement with the experimental results in the range of pulse durations from 0 to 1 ps.

Suppression effect of solid inertants on coal dust explosion

The effect of solid inertants like rock dust on explosion suppression was experimentally tested.By adding solid inertants with different concentrations into three kinds of coal dust,the maximum explosion pressure P max and the rate of explosion pressure rise(d p/d t)max were acquired.Based on this,the suppression effect of rock dust on coal dust explosion was analyzed.The experimental and analytical results show that there are two major factors that play an important role in explosion suppression:composition of solid inertant and particle size of solid inertant.The higher the concentration of solid inertant and the smaller the particle size of solid inertant,the better the suppression effect.In addition,the smaller the particle size of coal dust,the larger the amount of rock dust.

Numerical simulation of liquid aluminum leakage in casting process

A model was built to simulate liquid aluminum leakage during the casting process,including transient trough flow,orifice outflow,and spread,to prevent the explosion.A comparison between the simulation data and the theoretical calculation results verifies that the model has remarkable adaptability and high accuracy.Although the height of liquid aluminum in the mixing furnace and outlet radius are changed,the molten aluminum will not leak during the casting process.The aluminum in the trough moves forward in a wave-like motion and causes a leakage.The spread of the leaked aluminum resembles a long strip on the ground.The leakage amount and spread area of liquid aluminum increase with increasing the height of liquid aluminum in the mixing furnace.

Dynamic responses of deep underground explosions based on improved Grigorian model

It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.

Numerical Simulation of Dynamic Response of an Existing Subway Station Subjected to Internal Blast Loading

In order to design and retrofit a subway station to resist an internal blast, the distribution of blast loading and its effects on structures should be investigated firstly. In this paper, the behavior of a typical subway station subjected to different internal blast Ioadings was analyzed. It briefly introduced the geometric characteristics and material constitutive model of an existing two-layer and three-span frame subway station. Then three cases of different explosive charges were consid- ered to analyze the dynamic responses of the structure. Finally, the maximum principal stress, dis- placement and velocity of the columns in the three cases were obtained and discussed. It con- cluded that the responses of the columns are sensitive to the charge of explosive and the distance from the detonation. It＇s also found that the stairs between the two layers have significant effects on the distribution of the maximum principal stress of the columns in the upper layer. The explicit dynamic nonlinear finite element software ANSYS/LS-DYNA was used in this study.

Piezoelectric responses of brittle rock mass containing quartz to static stress and exploding stress wave respectively

The electromagnetic emission(EME) induced from the rock containing piezoelectric materials was investigated under both static stress and exploding stress wave in the view of piezoelectric effect. The results show that the intensity of the EME induced from the rock under static stress increases with increasing stress level and loading rate; the relationship between the amplitude of the EME from the rock under different modes of stress wave and elastic parameters and propagation distance was presented. The intensity of the EME relates not only to the strength and elastic moduli of rock masses,but also to the initial damage of the rock. The intensity of EME induced by stress wave reaches the highest at the explosion-center and attenuates with the propagation distance. The intensity of EME increases with increasing the elastic modulus and decreases with increasing initial damage. The results are in good agreement with the experimental results.

Structure and flaws of CuCr alloys by explosive compaction

CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractured surface displays ductile characteristics. In the metallurgical structure, CuCr alloys are composed of two phases of uniform distribution; the SEM morphology is like thin strips with an end arrangement that is bonded to each other and the two-phase distribution of CuCr alloys is more homogenous. It is in only in a very small zone that formation of Cu-rich and Cr-rich phases take place. The flaws of the compaction samples are mainly central-holes and cracks.

Translating Linear Temporal Logic Formula s into Automata

To combat the well-known state-space explosion problem in Prop ositional Linear T emp o- ral Logic （PLTL） model checking, a novel algo- rithm capable of translating PLTL formulas into Nondeterministic Automata （NA） in an efficient way is proposed. The algorithm firstly transforms PLTL formulas into their non-free forms, then it further translates the non-free formulas into their Normal Forms （NFs）, next constructs Normal Form Graphs （NFGs） for NF formulas, and it fi- nally transforms NFGs into the NA which ac- cepts both finite words and int-mite words. The experimental data show that the new algorithm re- duces the average number of nodes of target NA for a benchmark formula set and selected formulas in the literature, respectively. These results indi- cate that the PLTL model checking technique em- ploying the new algorithm generates a smaller state space in verification of concurrent systems.

Numerical Simulation of Concrete Plate Damaged Under Explosive Loading

The grisliness after-effects can be induced by explosion accident with the collapsing of the structures, the demolishing of the equipments and the casualty of the human beings. Isolation belt constructed between the blast point and the construction is one of the useful design schemes for blast resistance. The nonlinear procedure ANSYS/LSDYNA970 is used to simulate the contact detonation and the isolation belt of blast resistance filled with the air or water respectively. The results indicate that the maximal damage can be caused by the contact detonation, and the isolation belt of blast resistent filled with water can reduce the damage greatly.

Numerical Simulation of the Flat Ribbon Wound Explosion Containment Vessels Subjected to Internal Blast Loading

In order to constitute engineering design methods of the flat ribbon wound explosion containment vessels, the dynamic response of such vessels subjected to internal explosion loading is simulated using LS-DYNA3D. Three winding angles, 10°, 15°and 20°, are considered. It is shown that among ribbon vessels investigated, the center displacement of outermost ribbons of the vessel with 10°winding angle is the smallest under the same blast loading. The response of vessels loaded in inner core is local. From the center of the cylindrical shell to the bottom cover, the maximum strain gradually decreases. The ribbons are subjected to tension in the length direction and compression in the width direction. Blasting shock energy concentrates on where is close to center section of blasting. For comparison, numerical simulation of a monobloc thick-walled explosion containment vessel is also investigated. It can be found that the biggest deformation of the flat ribbon wound explosion containment vessels is bigger than that of the monobloc thick-walled explosion containment vessel in the center section of blasting under the same TNT. Numerical results are approximately in agreement with experimental ones. It is proved that the ribbon vessels have the valuable properties of ' leak before burst at worst' compared with the monobloc vessels through numerical simulation.

A network security situation awareness method based on layered attack graph

The real-time of network security situation awareness(NSSA)is always affected by the state explosion problem.To solve this problem,a new NSSA method based on layered attack graph(LAG)is proposed.Firstly,network is divided into several logical subnets by community discovery algorithm.The logical subnets and connections between them constitute the logical network.Then,based on the original and logical networks,the selection of attack path is optimized according to the monotonic principle of attack behavior.The proposed method can sharply reduce the attack path scale and hence tackle the state explosion problem in NSSA.The experiments results show that the generation of attack paths by this method consumes 0.029 s while the counterparts by other methods are more than 56 s.Meanwhile,this method can give the same security strategy with other methods.

Influence of Vapor Cloud Shape on Temperature Field of Unconfined Vapor Cloud Explosion

In order to analyze the influence of vapor cloud shape on temperature field effect of unconfined vapor cloud explosion(UVCE)and obtain creditable prediction method of explosion temperature effect,the transient temperature fields of cylindrical and hemispherical UVCEs with same methane concentration and mass were numerically studied by computational fluid dynamics(CFD)technology.According to numerical simulation results, the concepts of UVCE’s temperature-near-field and temperature-far-field were proposed,the corresponding ranges were given,and the temperature attenuation laws and differences in corresponding regions with different vapor cloud shapes were presented.Through comparing with Baker fireball model,the accuracy and visualizability in acquisition of entire temperature effect based on numerical simulation were further validated.The functional relations among maximum temperature,horizontal distance,initial temperature and vapor cloud mass in temperature-near-field and temperature-far-field were deduced by means of data fitting,respectively.These conclusions provided quantitative basis for forecast and protection of UVCE disaster.

The explosive-concussion jet:a new type fire distinguisher

Based on the fluid transient theory and explosive dynamics, a new type explosive driven jet is put forward. The generator of the proposed jet system comprises an explosive power source, a dynamic cavity, a spacing block, a water storage chamber, and a rubber membrane. The dynamic explosive source of power for the jet is composed of a cartridge and a bullet. The pressure in the dynamic cavity goes up to a range from 300 MPa to 350 MPa very quickly when the bullet is emitted. Driven by such a high pressure, the speed of the jet reaches 120 m/s. The effective distance to distinguish a fire is within 40 m. The jet has the following advantages over a conventional high-pressure water jet system: 1)strong power and strong transient force produced by dynamic source; 2) the energy of the dynamical source concentrated in a small scope with very little loss; 3) extensive applicability; and 4) safe usage without sparkling and smoke.

Status of the OECD-SERENA Project for the Resolution of Ex-vessel Steam Explosion Risks

OECD/NEA （Organization for Economic Cooperation and Development/Nuclear Energy Agency） launched the SERENA （steam explosion resolution for nuclear application） project to resolve internationally the ex-vessel steam explosion issue, which is one of major unresolved issues after a TMI-2 （three mile island-2） accident. One of main conclusions of OECD/NEA SERENA Phase 1, which was completed in 2005, was that some damage to the cavity is to be expected for an ex-vessel explosion. One major uncertainty that does not allow for a convergence toward consistent predictions was that there are no data on the component distribution in a pre-mixture at the time of an explosion, especially the level of the void. The other major uncertainty is the explosion behavior of corium melts. Therefore, SERENA Phase 2 was launched on October 1, 2007 to resolve the uncertainties of the coolant void and material effect by performing a limited number of well-designed tests with advanced instrumentation reflecting a large spectrum of ex-vessel melt compositions and conditions, and the required analytical work to bring the code capabilities to a sufficient level for use in reactor case analyses. The recent status of the OECD-SERENA Phase 2 project for the resolution of ex-vessel steam explosion risks will be described.