Dynamics and scaling of explosion cratering in granular media

Granular cratering is a ubiquitous phenomenon occurring in various natural and industrial contexts. Although impact‐induced granular cratering has been extensively studied, fewer experiments have been conducted on granular cratering via low‐energy explosions. Here, we study the dynamics and scaling of explosion granular cratering by injecting short pulses of pressurized air in quasi‐two‐dimensional granular media. Through an analysis of the dynamics of explosion processes at different explosion pressures, explosion durations, and burial depths, we identify two regimes, the bubbling and the eruption regimes, in explosion granular cratering. Our experiments explore the distinctive dynamics and crater morphologies of these regimes and show the energy scaling of the size of explosion craters. We compare high‐energy and low‐energy explosion cratering as well as explosion and impact cratering in terms of their energy scalings. Our work illustrates complex granular flows in explosion cratering and provides new insights into the general scaling of granular cratering processes. © 2017 American Institute of Chemical Engineers AIChE J, 64: 2972–2981, 2018     

Damage and rock-volatile mixture effects on impact crater formation

We explored simple geologic strength and material response models to determine which have the capability to simulate impact-induced faulting, complicated ejecta patterns and complex crater shapes. This led us to develop models for material damage, dilatancy, and inhomogeneous materials (mixtures). We found that a strength degradation (damage) model was necessary to produce faulting in homogeneous materials. Both normal and thrust ring faults may occur and extend relatively deeply into the planet during the transient cavity radial expansion. The maximum depth of fault development is about the depth of maximum penetration by the projectile. Dilatancy in geologic materials may reduce the final bulk density compared to the pristine state because of irreversible fracturing. When we include the effects of dilatancy, the radial position of faulting is displaced because of greater upward motions. In addition, the late time crater profile is shallower and the expression of features such as central peaks and rings may be more pronounced. Both damage and rock-ice mixtures effect the distribution of ejecta. The excavation flow field within the heavily damaged region is similar to flow fields in Mohr-Coulomb materials with no zero-pressure strength. In the outer, less damaged zone within the excavation cavity, the material trajectories collapse back into the crater. This effect creates a zone of reduced ejecta emplacement near the edge of the final crater. In the case of rock-ice mixtures, energy is preferentially deposited in the more compressible volatile component and the ejecta pattern is dependent upon the location of shock-induced phase changes in the volatile material.     

露天爆破大块控制试验

露天矿产生爆破大块受炮孔间距、炮孔排距、爆破方法、装药方式、充填距离等因素控制。以某露天钼矿为例,应用经验公式设计、爆破漏斗试验及爆破工业试验,确定了炮孔排距、间距、装药方式、起爆方法和充填方式,改善了爆破效果。试验发现,同时应用孔间和孔内微差是改善爆破效果的最有效方式,后排应用孔间或孔内微差时爆破后震较大。     

束状孔双漏斗爆破分段采矿法研究

采用束状孔当量球形药包(ESC)漏斗爆破分层落矿,爆破落矿的分层高度为单漏斗爆破的高度,且同一炮孔中需进行多次分层爆破,可造成分层爆破顶板不平整、塌孔等问题。基于束状孔爆破理论,通过现场试验,确定漏斗爆破参数,研发了束状孔双漏斗爆破分段采矿法。该方法矿块中布置平行束状炮孔,炮孔内分上下两层布置药包。药包同时起爆,爆破方向分别指向分段采场上部的凿岩硐室及下部的临空面,实现分段采场组合爆破漏斗水平落矿。一次爆破分段的高度为两组爆破漏斗深度及间隔距离之和。分段高度14～20 m,一次崩落爆破规模达10万t级,矿石回采率≥85%,贫化率≤10%,大块率<5%,采场生产能力≥2 500 t/d。该方法解决了爆破过程中炮孔破坏问题,并增加了采场一次爆破的规模,极大提高了采矿效率。     

强脉冲离子束辐照GH202镍基高温合金表面改性

为改善GH202镍基高温合金的表面性能,使用成分为C~(n+)和H~+、加速电压为250kV的强脉冲离子束(IPIBs)对其进行表面辐照处理。采用光学显微镜、X射线衍射仪、扫描电子显微镜和显微硬度计等分别对不同参数辐照后的试样的表面形貌及性能进行测试。结果表明:辐照后GH202合金表面产生了熔坑,熔坑的尺寸随能量密度的增加而增加,最大可至70μm。熔坑的产生源于表层低熔点组分的喷发。表层的γ'相消失,辐照之后的试样表层产生了M_(23)C_6结构的碳化物并在辐照过程中受到压应力作用。辐照后试样表层近百微米深度内显微硬度均获得不同程度的提高。在高温氧化时,辐照后的样品表面更易于形成Cr_2O_3和Al_2O_3连续膜层氧化物,阻碍O元素向基体扩散,使得抗高温氧化性能得到改善。     

基于数字高程模型的月海地貌信息重建

有效载荷激光高度计获得的高程数据描述了月球的真实地形地貌.依据中国科学院国家天文台发布的源数据进行DEM建模和数据预处理,提取坑谷状地形的地理信息,提出基点弥散方法,通过计算平面曲率寻找坑唇点,确定非规则边界月球坑搜寻的终止条件,对全月陨石坑进行了识别标定及特征参数计算.按照所得不同年龄陨石坑的统计分布规律,结合坡度坡向矩阵,重建月海地貌仿真地形,得到输入参数用户控制的三维高程数据,可据此重构大量月海地貌,进行着陆安全概率计算.     

强流脉冲电子束作用下镍基高温合金GH4169的微观结构及腐蚀性能

利用强流脉冲电子束(High current pulsed electron beam,HCPEB)技术对镍基高温合金GH4169进行表面处理,利用X射线衍射仪(X-ray diffraction,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)和透射电子显微镜(Transmission electron microscopy,TEM)对HCPEB诱发的微观结构进行详细的表征,并考察HCPEB辐照处理后样品表面的腐蚀性能。试验结果表明,HCPEB辐照后GH4169合金表面发生熔化并形成熔坑,熔坑密度随辐照次数的增加而降低,尺寸较大的第二相颗粒等可随着熔坑的喷发而清除,进而实现表面净化。HCPEB辐照后GH4169合金表面形成3~5μm厚的重熔层,重熔层内部以尺寸在100 nm左右的纳米晶为主,HCPEB辐照还可在表层诱发强烈的塑性变形,形成高密度的位错及变形孪晶等变形结构。HCPEB辐照显著地改善了GH4169合金的耐蚀性能,腐蚀性能的改善主要归因于表面净化效应以及表层纳米重熔层和高密度的晶体缺陷的形成,这些微观结构促进了表层钝化膜的形成,起到保护基体的作用。     

用重砂矿物分布规律辨认火山口和砂矿类型——以海南含蓝宝石玄武岩区为例

玄武岩浆携带深源包体、蓝宝石和其他重砂“巨晶”矿物高速从火山口喷出,离开火山口后由于压力突然降低、流动速度急剧减小,以致于在火山日附近沉淀许多深源包体和重矿物;而离开火山口愈远,重砂矿物愈轻、颗粒愈小。依此规律,确认海南蓬莱岭为一火山口。玄武岩区同一层的人工重砂矿物特别是比重较大的磁铁矿“巨晶”大量富集于火山口附近,而蓝宝石和锆石却常离火山口1～3。5km,宝石分布区常处于几个火山口之间。对主要宝石矿区牛姆岭的残坡积层,沿勘探网(100m×100m)取样,不同点重砂矿物与不同层位玄武岩中人工重砂及岩石对比证明,牛姆岭砂矿以残积为主,坡积为辅。     

CAVITY MODELS FOR SOLID AND HOLLOW PROJECTILES

Two analytical models for the crater size generated by long-rod and thick-walled tube projectiles are presented. The first is based on energy; in a steady-state penetration, the kinetic energy loss of a projectile is related to the total energy deposited in the target. This simple approach provides an upper bound for the crater size. The second approach is based on the observation that two mechanisms are involved in cavity growth due to long projectiles: flow of projectile erosion products, which exerts radial stress on the target and opens a cavity, and radial momentum of the target as it flows around the projectile nose (cavitation). This analysis includes the centrifugal force exerted by the projectile, radial momentum of the target, and the strength of the target. Thus, it can estimate the extent of cavity growth due to projectile mushrooming, which cannot be predicted by other analyses. This model is shown to be in good agreement with experimental data.     

电泳缩孔与FMEA质量工具

对FMEA工具的应用进行介绍,分析了引起电泳缩孔缺陷的FMEA文件,同时介绍了运用FMEA工具解决电泳缩孔问题的案例。