装药结构对爆破震动能量传递及爆破效果影响研究

 由于装药结构作为爆破设计的重要参数,对爆破影响不可忽视,由阻抗匹配角度对3种不同装药(耦合、空气不耦合及水不耦合)结构爆破能量传递进行理论分析,获得能量传递与装药结构关系,即不耦合装药时存在合理的不耦合系数使爆破能量高效传递给岩石。通过具体爆破开挖工程对爆破震动进行测试及能量传递公式验证,结果表明,以水作为不耦合介质的不耦合装药能有效降低爆破震动能量,减小爆破粉尘危害,且使块度更均匀。     

On the ballistic performance of metallic materials

The paper presents a ballistic performance index for metallic armour materials in terms of the commonly determined mechanical properties such as strength and modulus. The index is derived using an energy-balance approach, where the kinetic energy of the projectile is assumed to be absorbed by the elastic and the plastic deformation involved in the penetration process as well as the kinetic energy imparted to the target material during deformation. The derivation assumes two distinct stages to exist during the penetration of the projectile. At the striking face of the armour, the material is assumed to flow radially in a constrained deformation region but longitudinally at the rear surface leading to typically observed bulging of the armour without constraint. The index is validated using the available experimental and empirical data obtained in the case of small arm projectiles for an impact velocity of about 800 m/sec. This index is expected to facilitate the development of metallic armour, since the number of the ballistic experiments can be reduced significantly and only the promising materials need to be considered.     

High velocity penetration of homogeneous, segmented and telescopic projectiles into alumina targets

Segmented and telescopic projectiles are designed to make efficient use of the higher impact velocities achievable with new acceleration techniques. This concept has been found to work against steel armour. In this study, we compare the penetration capability into an alumina target for these unconventional projectiles with that of a homogeneous projectile. The influence of segment separation distance and core-to-tube diameter ratio were simulated for the impact velocities 2.5, 3.0 and 3.5 km/s. The simulated final penetrations are compared to test results for one type of each of the homogeneous, segmented and telescopic projectiles at 2.5 and 3.0 km/s. Both simulations and tests show that the unconventional projectiles have better penetration capability than a homogeneous projectile with the same initial geometry.     

An experimental study on the shattering behavior of a high strength armour steel under blast and long rod penetrator impact

Armour steel plates with drilled holes are filled with explosive and subjected to single or multiple blasts to induce shattering. The critical diameter for shattering under explosive detonation, found from the experiments matches closely with that of the long rod penetrator impacted plates. The damage pattern and fracture surface of the tested samples under blast effect have been compared with plates impacted with long rod penetrators for matching the observed shattering behavior. Difference in the shattering behavior of the armour steel subjected to single and multiple blasts has also been presented.     

PVDF薄膜传感器用于测试块状岩石表面爆炸应力的研究

采用PVDF（聚偏二氟乙烯）薄膜传感器对岩石表面爆炸应力进行测量,并分析炮孔内不同填塞介质对爆炸应力波在岩石介质中传播的影响。在直径为28 mm、孔深为25 cm的炮孔内填塞不同的介质（空气、水或沙子）,采用不同的装药结构分别进行爆破试验,通过PVDF薄膜传感器得到了不同工况下岩石表面应力波时程曲线。分析炮孔内不同填塞介质对爆炸应力波透射的影响发现,水作为炮孔填塞介质时,爆炸应力波透射能力强,炸药爆炸产生的能量用于岩石破碎的比例高。水作为炮孔填塞介质时,为达到岩石开裂效果,装药结构设计为1发8^#雷管加2 g传爆药（聚黑-14）;当沙子作为炮孔填塞介质时,为达到岩石的开裂效果,装药结构设计为1发8^#雷管、2 g传爆药（聚黑-14）和20 g炸药（聚黑-2）;前者炸药用量仅为后者的15.3%。炸药使用量减少,也降低了爆破次生危害的影响程度。用PVDF薄膜传感器在岩石表面直接测量爆炸应力的方法是可行的。     

Fragmentation of Spherical Shells under Internal Blast Loading

We present experimental data on the fragmentation, scattering, and penetration into barriers of fragments of thin-walled spherical shells made of soft steel or an aluminum alloy, which are loaded internally by blasting a sphere-shaped explosive charge. The speed, number, and average sizes of fragments formed of shells of different sizes as well as the maximum depths of penetration of fragments into barriers made of a number of homogeneous and heterogeneous materials have been determined. Some characteristic features of the fragmentation of spherical shells under internal blast loading have been elucidated. An attempt has been made to describe the characteristic (average) fragment size by a formula derived from the balance of elastic energy and the work of fracture. Thicknesses of fragmentation protective layers of some structural materials have been chosen, which enable catching soft steel or aluminum alloy fragments which are formed by the explosion of particular sphere-shaped explosive charges.     

A new concept of shock mitigation by impedance-graded materials

Over the last several decades, homogenous single-layer armor has been replaced by multi-layer integral armor to improve ballistic penetration resistance. This has led to better attenuation of shock wave energy by multiple interface reflections and transmissions. Efforts have been reported to improve the penetration resistance by providing higher energy dissipation at higher levels of impedance mismatch. However, high stress concentrations and stress reversals have made these interfaces the primary sources of failure. This paper discusses a concept for a new class of blast and penetration resistant (BPRM) materials which are layer-less but designed to have a continuous gradient of impedance that can dissipate the shock energy without material failure. In a simplistic approach by applying the classical theory of uniaxial stress propagation, it has been shown that attenuation of the stress wave energy would be possible by controlling the impedance distribution within the body of such a material. The development of such material to resist blast or impact will overcome the current common difficulty of interfacial delamination failure in any protective barrier system or armors.     

A note on the behind armour effects from perforated alumina/aluminium targets

A thin, ceramic-faced armour, separated from a thick metal block, has been subjected to high-velocity impact by a 6.35 mm diameter steel sphere. Experimental work was carried out which compared firings into ceramic-faced aluminium armour, separated from thick aluminium “witness” blocks, with firings into the thick aluminium blocks alone. The depth of penetration and the area of damage were measured and an estimated percentage weight saving due to the inclusion of the ceramic-faced armour was calculated at varying velocity. This note yields useful information for the design and application of ceramic appliqué systems.     

Non-explosive methods for simulating blast loading of structures with complex geometries

Characterizing structural responses and applied loads during the entire course of a blast event is problematic due to the harsh conditions of the explosive environment. A procedure for the distribution of blast-like pressures to structures of complex geometries using custom water bladders has been developed using the University of California, San Diego’s (UCSD) Blast Simulator. The methodology was motivated by an effort to test the blast resistance of structures subject to internal, or external, blasts where attention would be focused on areas such as joints, corners, or other areas within occluded geometry.Three series of experiments were conducted in an effort to characterize the use of water bladders for blast simulations. Bladder material, geometry, use of baffles and strapping methods were varied along with Simulator input parameters such as impact velocity and impacting mass geometry. The effects of these variables have been quantified through the comparison of measured pressures, pulse durations and impulses. The experimental methodology demonstrates the ability to tailor load curves to simulate a wide range of blast scenarios.     

The use of digital speckle radiography to study the ballistic deformation of a polymer bonded sugar (an explosive simulant)

This paper reports an initial study into the benefits of determining two-dimensional flow fields for low velocity impact on a small-scale model of explosive reactive armour (ERA) using digital speckle radiography (DSR). The model system consisted of a polymer-bonded sugar (PBS) (otherwise known as a sugar mock) confined between two mild steel plates. The DSR technique relies upon creating a layer within the specimen that is seeded with lead particles. So although radiography itself is mechanically non-invasive, the lead layer needed may change the mechanical properties of the material. DSR revealed where regions of intense shear occurred in normal impact. These regions are likely to be where a polymer-bonded explosive (PBX) would initiate.     

The response of carbon fibre composites to blast loading via the Europa CAFV programme

Modern military vehicles must balance the need for occupant protection against the competing requirements for high mobility and payload capacity. As such, there is continuing interest in the development of lightweight vehicle structures that reduce the overall mass of the hull and armour system, leading to a lighter vehicle. One way to achieve this is through the use of materials that can perform both structural and protective roles, reducing the mass of appliqué armour required to achieve a given level of protection. The aim of the 3-year EUROPA Carbon Fibre for Armoured Fighting Vehicles (CAFV) programme was to investigate the use of carbon fibre composites for use in military vehicle structures. Six nations took part in the programme, each assessing the benefits of carbon fibre composites in terms of their application to at least part of an armoured fighting vehicle (AFV) hull. For the UK, a lower hull section was selected as the focus for the research programme and, as part of the programme, assessed against mine blast threats.     

Experimental study on hybrid CFRP-PU strengthening effect on RC panels under blast loading

Recently, fiber reinforced polymer (FRP) usages for strengthening RC infrastructures have been continuously increasing. Especially, the use of FRPs to strengthen structures against a blast terror or an impact accident is receiving great interests from specialists in the structural retrofitting and strengthening field. In order to achieve better protections from blast or impact loading, a new retrofit composite material has been proposed by combining highly stiff and strong material of carbon fiber reinforced polymer (CFRP) with highly ductile material of Polyurea (PU). The combination of CFRP and PU can result in a retrofit composite with enhanced stiffness and ductility properties as well as fragment catching characteristic. To estimate the hybrid composite’s blast resistant capacity, nine 1000 × 1000 × 150 mm RC panel specimens retrofitted with either CFRP, PU, or hybrid composite sheets were blast tested. The blast load was generated by detonating a 15.88 kg ANFO explosive charge at 1.5 m standoff distance. The data of free field incident and reflected blast pressures, maximum and residual displacements, and steel and concrete strains, etc. are measured from the test. Also, the failure mode and crack patterns were evaluated to determine the failure characteristic of the panels. The results from the experiments showed that the hybrid composite has better blast resistant capacity than ordinary retrofit FRPs. The study results are discussed in detail in the paper. The test results will not only provide blast resistant capacity of each retrofit material, but they will be valuable backup data for preliminary estimation of RC structural members’ blast protection performances.     

Microplane finite element analysis of tube‐squash test of concrete with shear angles up to 70°

Finite element analysis of the response of concrete structures to impact events such as missile penetration, explosive driving of anchors, blast, ground shock or seismic loading, requires knowledge of the stress–strain relations for concrete for finite strain at high pressures. A novel type of material test achieving very large shear angles of concrete at very large pressures, called the tube‐squash test, can be used to calibrate a concrete model taking into account plastic deformation at extreme pressures. A finite element analysis of such a test is performed by using a finite strain generalization of microplane models for concrete and steel. The results obtained are in good agreement with those previously obtained with a simplified method of analysis. Thus, they provide a validation of the microplane model, which is shown to be capable of reproducing the response of concrete not only for small strains at small pressures, which is predominantly brittle, but also for high pressures and large finite strains, which is predominantly frictional plastic. Copyright © 2001 John Wiley & Sons, Ltd.     

冲击波作用下巷道破坏规律相似模拟研究

利用爆炸加载的方式,采用相似材料模拟试验方法,借助数字散斑观测手段(DSCM),研究不同炮孔位置和装药量条件下巷道变形破坏规律。试验结果表明,微量炸药引爆后,冲击应力波以巷道方向传递为主,巷道顶板附近形成裂纹、破碎或坍塌区;当装药量足够大时,冲击波对上部岩体破坏力明显增大,冲击能是影响巷道破坏程度的主要因素。试验结果还表明,高速冲击载荷作用下巷道围岩体破坏过程可分为拉剪裂缝、重复拉剪破碎和破坏三个阶段。其中,当炮孔距离巷道为450mm,装药量为6.0g时,巷道顶板附近出现裂缝,属于拉剪裂缝阶段;当炮孔距离巷道为300mm,装药量为6.0g时,巷道顶板附近裂缝较为发育,且巷道顶层出现部分塌落,属于重复拉剪破坏阶段;当炮孔距离巷道为200mm,装药量为8.0g时,巷道顶板出现塌落,且四周破坏,属于破坏阶段。研究结果为冲击地压巷道破坏预测和防治提供了有力参考。     

模拟破片杀伤战斗部空爆冲击波与高速破片群联合作用的等效试验方法

破片杀伤战斗部空爆冲击波与高速破片群联合毁伤作用下目标结构的毁伤特性、防护效能等是当前防护领域的热点和难点,但目前的试验研究手段和方法存在不足,为此,提出采用等效缩比战斗部(其原理为炸药爆炸驱动预制破片分散)来模拟破片杀伤战斗部,可作为进行空爆冲击波与高速破片群对防护结构的联合毁伤作用的实验方法。在确定防御目标战斗部、防御目标弹丸和几何缩尺比的基础上,根据爆炸力学相关经验公式,提出了求解等效缩比战斗部的装药和预制破片的相关参数的等效计算方法。该等效试验方法考虑了多破片侵彻的增强效应以及与爆炸冲击波的联合毁伤增强效应,且等效计算方法参数较少、简单实用。     

Simulations of fracture and fragmentation of geologic materials using combined FEM/DEM analysis

Results are presented from a study investigating the effect of explosive and impact loading on geological media using the Livermore distinct element code (LDEC). LDEC was initially developed to simulate tunnels and other structures in jointed rock masses with large numbers of intact polyhedral blocks. However, underground structures in jointed rock subjected to explosive loading can fail due to both rock motion along preexisting interfaces and fracture of the intact rock mass itself. Many geophysical applications, such as projectile penetration into rock, concrete targets, and boulder fields, require a combination of continuum and discrete methods in order to predict the formation and interaction of the fragments produced. In an effort to model these types of problems, we have implemented Cosserat point theory and cohesive element formulations into the current version of LDEC, thereby allowing for dynamic fracture and combined finite element/discrete element simulations. Results of a large-scale LLNL simulation of an explosive shock wave impacting an elaborate underground facility are also discussed. It is confirmed that persistent joints lead to an underestimation of the impact energy needed to fill the tunnel systems with rubble. Non-persistent joint patterns, which are typical of real geologies, inhibit shear within the surrounding rock mass and significantly increase the load required to collapse a tunnel.     

Numerical and experimental investigations into ballistic performance of hybrid fabric panels

Strong, low density fibres have been favoured materials for ballistic protection, but the choice of fibres is limited for making body armour that is both protective and lightweight. In addition to developments of improved fibres, alternative approaches are required for creating more protective and lighter body armour. This paper reports on a study on hybrid fabric panels for ballistic protection. The Finite Element (FE) method was used to predict the response of different layers of fabric in a twelve-layer fabric model upon impact. It was found that the front layers of fabric are more likely to be broken in shear, and the rear layers of fabric tend to fail in tension. This suggested that using shear resistant materials for the front layer and tensile resistant materials for the rear layer may improve the ballistic performance of fabric panels. Two types of structure, ultra-high-molecular-weight polyethylene (UHMWPE) woven and unidirectional (UD) materials, were analyzed for their failure mode and response upon ballistic impact by using both FE and experimental methods. It was found that woven structures exhibit better shear resistance and UD structures gives better tensile resistance and wider transverse deflection upon ballistic impact. Two types of hybrid ballistic panels were designed from the fabrics. The experimental results showed that placing woven fabrics close to the impact face and UD material as the rear layers led to better ballistic performance than the panel constructed in the reverse sequence. It has also been found that the optimum ratio of woven to UD materials in the hybrid ballistic panel was 1:3. The improvement in ballistic protection of the hybrid fabric panels allows less material to be used, leading to lighter weight body armour.     

Experiments and numerical analyses of blast and fragment impacts on concrete

Concrete structures are commonly used as protective structures. An important issue is how the blast wave and fragment impacts from an explosion affect the concrete. It is well known that the fragments penetrate or even perforate the structure. Moreover, spalling occurs in the impact zone and scabbing may occur on the reverse side of a wall that receives an impact. However, knowledge of how the blast wave and fragment impacts influence the material properties of concrete is quite limited. Experiments and numerical analyses were carried out to examine the extent to which the concrete, at various distances, is affected by the blast wave and fragment impacts. The fragments, which were spherical, were shot against thick concrete blocks by using the explosives octol or hexotol; the fragment velocity was approximately 1650 m/s. After the concrete blocks were shot, the depths of penetration and spalling were measured. Next, the concrete blocks were cut into halves, and the global macro-cracking could be observed. To study how the material properties of concrete were influenced, uniaxial compressive and splitting tensile tests were carried out on cylinders drilled from selected positions in the block. Furthermore, specimens from the blocks were thin-ground to facilitate analysing the micro-cracking with a microscope. The experiments and numerical analyses presented here showed that the damage in the concrete, from the blast wave and fragment impacts, is localized in the impact zone. The concrete below this zone, at a depth of approximately twice the depth of the maximum penetration, was hardly affected at all by the blast wave and fragment impacts. This indicates that it is possible to distinguish between the global load effects and the local damage effects that are caused by the fragment impacts. Consequently, it may be possible to separate the loads, at the design stage, from a blast wave and fragment impacts.     

Behaviour of sandwich panels subjected to intense air blast – Part 1: Experiments

Tests that investigate the inelastic response of blast-loaded sandwich structures, comprising mild steel plates and aluminium alloy honeycomb cores, are reported. The “uniform” loading was generated by detonating a disc of explosive and directing the blast through a tube towards the target. Localised blast loading was generated by detonating discs of explosive in very close proximity to the test structure. The sandwich panels responded in a more efficient manner to the uniformly distributed loading, and hence the majority of the paper is concentrated on uniform loading response. The honeycomb sandwich results are compared to test results on structures with air as the core. The failure modes and interaction between the components are discussed. Three phases of interaction are identified for each sandwich structure, based upon deformation, contact, crushing and tearing responses of the sandwich components. The compromise between load transfer through the core and improved energy absorption is discussed.     

Penetration mechanisms in glass laminate/resin structures

The ballistic response of composite structures comprising differing laminated float glass/polycarbonate replacement resin (PRR) elements was studied. In order to provide materials data for future modelling work, sphere-impact tests were employed to determine the high strain-rate response of the elastomeric resin. Larger-scale armour simulants comprising glass-laminate-fronted cylinders of PRR were also investigated using lead antimony-cored 7.62 mm × 51 mm NATO Ball rounds in order to interrogate their behaviour under impact. Penetration mechanisms were studied via the use of high-speed video equipment. Projectile defeat in the resin was observed to depend on the degree of projectile disruption, with a greater degree of comminution leading to enhanced behaviour. This confirmed the importance of the elastomeric properties of the resin in behaviour under ballistic impact in these structures. The interaction between the glass disrupting layer and the backing absorber was found to be key to minimising subsequent penetration. The use of asymmetric float glass laminates incorporating a thinner disrupting outer surface was found to reduce subsequent depth of penetration by as much as 52% compared to similar areal density monolithic systems. High-speed video footage implied that the thinner outer layer acted to blunt the incident projectile, while the backing thick layer of glass exhibiting a Hertzian cone-like “plugging” failure mechanism. In addition analysis of high-speed video showed that the penetration rate in the resin was initially constant, implying penetration analogous to hydrodynamic behaviour.