Distance Control and Positive Security for Intrinsic Equipment Working in Explosive Potential Atmospheres

In this paper, intrinsic safety and positive security distance control for an up/down elevator which extracts the materials from an underground coal mine is approached. For a better understanding of intrinsic safety and positive security, the first part of the paper describes the potential risk the workers are facing while working in dangerous environments like coal mining with “grisou” atmospheres and what the conditions of an unfortunate event to take place are. We presented the diagram and working principle for intrinsic safety equipment used in potential explosive areas based on which we modeled and simulated the intrinsic and positive security distance control in order to get a software solution for it. We created an algorithm and simulated the process in Matlab Simulink. The simulation results done in Matlab Simulink were then entered into a Moeller PLC using a ladder-type programming language. For protection against explosive atmospheres, the PLC is inserted into a metal housing with intrinsic protection and Positive Security.

Simulations of explosion-induced damage to underground rock chambers

A numerical approach is presented to study the explosion-induced pressure load on an underground rock chamber wall and its resultant damage to the rock chamber.Numerical simulations are carried out by using a modified version of the commercial software AUTODYN.Three different criteria,i.e.a peak particle velocity (PPV) criterion,an effective strain (ES) criterion,and a damage criterion,are employed to examine the explosion-induced damaged zones of the underground rock chamber.The results show that the charge chamber geometry,coupling condition and charge configuration affect significantly the dynamic pressure exerted on the rock chamber wall.Thus the chamber is damaged.An inaccurate approximation of pressure boundary ignoring the influences of these factors would result in an erroneous prediction of damaged area and damage intensity of the charge chamber.The PPV criterion yields the largest damaged zone while the ES criterion gives the smallest one.The presented numerical simulation method is superior in consideration of the chamber geometry,loading density,coupling condition and rock quality.The predicted damage intensity of rock mass can be categorized quantitatively by an isotropic damage scalar.Safe separation distance of adjacent chambers for a specific charge weight is also estimated.

Experimental investigations on small-and full-scale ship models with polyurea coatings subjected to underwater explosion

Nowadays, the mitigation of damage to a ship caused by the underwater explosion attracts more and more attention from the modern ship designers. In this study, two kinds of scale tests were conducted to investigate the effects of polyurea coatings on the blast resistance of hulls subjected to underwater explosion. Firstly, small-scale model tests with different polyurea coatings were carried out. Results indicate that polyurea has a better blast resistance performance when coated on the front face, which can effectively reduce the maximum deflection of the steel plate by more than 20% and reduce the deformation energy by 35.7%-45.4%. Next, a full-scale ship(approximately 50 m × 9 m) under loadings produced by the detonation of 33 kg of spherical TNT charges was tested, where a part of the ship was coated with polyurea on the front face(8 mm + 24 mm) and not on the contrast area. Damage characteristics on the bottom were statistically analyzed based on a 3D scanning technology, indicating that polyurea contributes to enhancing the blast protection of the ship. However, damage results of this test were different from those of the small-scale tests. Moreover, the deformation area of the bottom with polyurea was greatly increased by 40.1% to disperse explosion energy, a conclusion that cannot be drown from the small-scale tests.

Effects of heat treatment on the intermetallic compounds and mechanical properties of the stainless steel 321–aluminum 1230 explosive-welding interface

The effects of heat treatment on the microstructure and mechanical properties of intermetallic compounds in the interface of stainless steel 321 explosively bonded to aluminum 1230 were investigated in this study. Experimental investigations were performed by optical microscopy, scanning electron microscopy, and microhardness and shear tensile strength testing. Prior to heat treatment, increasing the stand-off distance between samples from 1 to 2.5 mm caused their interface to become wavy and the thickness of intermetallic layers to increase from 3.5 to 102.3 μm. The microhardness increased from HV 766 in the sample prepared at a stand-off distance of 1 mm to HV 927 in the sample prepared at a stand-off distance of 2.5 mm; in addition, the sample strength increased from 103.2 to 214.5 MPa. Heat treatment at 450°C for 6 h increased the thickness of intermetallic compound layers to 4.4 and 118.5 μm in the samples prepared at stand-off distances of 1 and 2.5 mm, respectively. These results indicated that increasing the duration and temperature of heat treatment decreased the microhardness and strength of the interface of explosively welded stainless steel 321-Al 1230 and increased the thickness of the intermetallic region.

Effect of postweld heat treatment on interface microstructure and metallurgical properties of explosively welded bronze–carbon steel

The effects of postweld heat treatment on the microstructure and metallurgical properties of a bronze–carbon steel(st37)explosively bonded interface were studied.Explosive welding was done under 1.5-and 2-mm standoff distances and different conditions of explosive charge.Samples were postweld heat treated for 4 and 16 h in the furnace at 250°C and 500°C and then air cooled.Laboratory studies using optical microscopy,scanning electron microscopy,and microhardness testing were used to evaluate the welded samples.Microstructural examinations showed that by increasing the standoff distance and the explosive charge,the interface of bronze to steel became wavier.The microhardness test result showed that the hardness of the samples was higher near the joint interface compared with other areas because of the intensive plastic deformation,which was caused by the explosion force.The results show that increasing the heat treatment temperature and time caused the intermetallic compounds’layer thickness to increase,and,because of the higher diffusion of copper and tin,the iron amount in the intermetallic compounds decreased.Also,because of the increase in heat treatment temperature and time,internal stresses were released,and the interface hardness decreased.

偏心药型罩在D型装药中的设计及成型性能研究

为改进整体式多爆炸成型弹丸(Multiple Explosively Formed Projectile,MEFP)战斗部中位于边缘位置处的药型罩口部闭合较差的问题,设计一种沿周向壁厚不同的偏心药型罩。将该药型罩应用于D型装药结构战斗部中,通过理论分析以及数值仿真方法,针对药型罩较厚一侧朝向和偏心距大小对药型罩成型的影响规律进行研究,开展爆炸成型弹丸(Explosively Formed Projectile,EFP)软回收试验。研究结果表明:偏心药型罩较厚侧朝向及偏心距大小对EFP各方向速度基本无影响,对EFP成型效果影响较大;药型罩较厚侧朝向战斗部中心时成型效果最佳;偏心距的大小能够调整药型罩周围微元向中心压合的速度差,改善药型罩口部包合情况;试验中回收到的EFP成型结果与仿真结果吻合度较高;偏心药型罩通过调整药型罩壁厚与爆轰波强度的匹配关系能够改善非对称爆轰下EFP的成型,有效解决D型装药结构MEFP战斗部位于边缘位置处药型罩成型较差的问题,为整体式MEFP战斗部边缘位置处药型罩结构设计提供参考。

环境温度对TATB/RDX传爆药起爆及驱动性能的影响

为了获得环境温度对TATB/RDX传爆药起传爆性能及驱动性能的影响特性,采用激光多普勒测速技术及瞬态太赫兹波多普勒干涉测速技术,对TATB/RDX传爆药在隔层起爆条件下的起爆、传播及驱动性能开展实验研究,获取了-45~70℃温度环境中TATB/RDX传爆药的到爆轰距离、爆轰反应区时间宽度、爆轰传播速度及驱动飞片的飞行速度曲线。结果表明:TATB/RDX传爆药的到爆轰距离及爆轰反应区时间宽度随环境温度的降低均近乎呈线性增长趋势;爆轰传播速度随环境温度的降低而逐渐提高;驱动飞片的速度随环境温度的变化特性在飞片主体-层裂层融合前后存在明显不同。

爆炸冲击波超压非均匀分布特性及最优测点数量

为掌握炸药爆炸冲击波超压的非均匀分布特性,根据非理想爆轰波特征及空气冲击波的形成机制,探讨了炸药爆炸冲击波超压峰值时空非均匀分布的原因和表现形式,得到了实验影像和测试数据的验证;开展了公斤级和百公斤级装药爆炸冲击波实验,分析了相同对比距离的多个超压峰值测试结果之间的偏离特性,结果表明炸药组分非理想程度越高、装药质量越大、距离装药越近,冲击波超压峰值非均匀特征越显著。在实验数据偏离分析基础上,提出了满足非均匀分布超压准确测试的最优测点数量,将爆炸场划分为对比距离小于1.5 m/kg^(1/3)、1.5~3.0 m/kg^(1/3)、3~5 m/kg^(1/3)和大于5 m/kg^(1/3)共4个区域,对应的最优测点数量分别为6个、5个、4个和2个。

近距爆炸装药形状对板架结构的损伤规律研究

为了研究近距爆炸时柱形装药长径比对板架结构变形损伤的影响规律,以某典型缩比板架结构作为研究对象,采用经实验验证的有限元模型,分析了5种不同长径比装药爆炸对板架变形损伤的影响,并对比分析了药柱与板架夹角为0°和90°两种情形的区别。研究结果表明:随着装药长径比的增大,夹角为90°情况下冲击波反射超压和冲量逐渐减小,夹角0°情况下冲击波反射超压和冲量逐渐增大,高压区逐渐从装药轴线方向到径向方向移动;板架的残余位移与装药质量近似满足线性关系,装药长径比增大时,夹角为90°时靶板的残余位移逐渐减小,夹角为0°时位移逐渐增大;基于板架中心点最大残余位移D,拟合得到了药柱轴线与靶板表面夹角为90°和0°时的轴向等效形状因子β_(1)和径向等效因子β_(2),当比例距离在0.4~0.7 m/kg^(1/3)范围内时,预测误差小于15%,能较好的预估不同装药长径比下板架的中心点残余位移,获取结构的损伤水平。

直流激励下桥丝型电火工品电弧发火预测模型

为了研究桥丝型电火工品在直流激励下的电弧发火特性,预测其电弧发火安全阈值,采用模拟电荷法计算了脚‐壳二维切面电场强度,利用电击穿理论计算了脚‐壳电击穿系数,提出了桥丝型电火工品电弧发火的量化判据并建立模型。结果表明,环境温度在25°左右,气压为大气压强时,桥丝型电火工品脚‐壳之间距离对其电弧发火阈值影响较大,脚‐壳距离越短,电弧发火阈值越低。桥丝型电火工品脚‐壳间电击穿电压预测模型计算结果与实测值相对误差不超过3.3%,且利用COMSOL仿真计算所得电击穿系数与预测模型计算结果相对误差约1%。

基于PHAST的苯海上运输船泄漏模拟分析

为预防苯海上运输中的泄漏安全事故,利用PHAST软件,以苯海上运输船为研究对象,探究不同泄漏孔径、风速对苯泄漏后的扩散距离及泄漏导致的池火、闪火、喷射火与超压爆炸范围的影响规律。结果表明,事故发生后,云团泄漏扩散距离、喷射火辐射影响半径及爆炸超压影响半径与泄漏孔径尺寸成正比,泄漏扩散距离、爆炸超压影响半径与风速成反比。浓度100×106以及风速3 m/s下,泄漏孔径由25 mm增加到时75 mm,顺风扩散最大距离扩大了近4倍,云团最大单侧宽度增加了3倍。风速越小,越不利于苯的扩散,使得安全距离较远,且超压半径较大,风险较高。

柱形装药空中爆炸冲击波荷载研究

受比例距离、装药长径比、起爆方式、方位角、冲击波入射角以及反射面相对位置等多种因素的影响,球形装药空中爆炸冲击波荷载的计算方法不适用于柱形装药。为探究柱形装药空中自由场爆炸冲击波入射和反射荷载,首先,开展柱形TNT装药单端起爆的空中爆炸试验,并基于显式动力学分析软件AUTODYN进行数值模拟,通过与试验和规范进行对比,验证了采用的有限元分析方法的适用性。进一步开展考虑比例距离、长径比、起爆方式、方位角和刚性反射等因素的1000余组柱形装药空中爆炸工况的数值模拟。基于模拟结果,揭示了柱形装药空中爆炸入射冲击波峰值超压和最大冲量及其形状因子的分布特征,提出峰值超压和最大冲量临界比例距离的判定准则和确定方法,阐明了刚性反射冲击波峰值超压和反射系数的变化规律。最后,提出柱形装药空中爆炸入射和反射冲击波荷载的计算方法,并得到360余组试验数据的验证。该方法可快速计算作用于建筑结构上的爆炸荷载,并为弹药毁伤效能评估、结构动态响应和破坏分析及其抗爆设计提供参考。

远距离捕捉网弹设计与仿真研究

为了对远距离捕捉网弹的发射稳定性进行分析,基于LS-DYNA平台建立远距离捕捉网弹弹体的有限元模型,分析爆炸后能量传递规律,评估了捕捉网弹的性能。结果表明,弹体在应力集中处能够完全扩爆撑开,在凹槽处最先产生较大的变形,然后能量逐步递减。该研究可为捕捉网弹的拓展应用提供依据。

考虑流场黏性的气泡与自由液面作用的数值模拟

[目的]旨在探究计入可压缩性和黏性效应流场中水下爆炸气泡与自由液面相互作用时液面水冢的演化规律。[方法]首先,基于OpenFOAM的可压缩两相流求解器和流体体积法(VOF),建立计入流场可压缩性和黏性效应的水下爆炸气泡与自由液面耦合作用的数值模型;然后,通过与试验结果进行对比,验证数值模型的有效性;最后,研究不同流场黏性和不同距离参数对气泡脉动过程及液面水冢运动的影响。[结果]结果显示,流场黏性效应对于水冢高度、气泡脉动周期、气泡脉动尤其是反弹阶段的气泡形态均有重要影响;低黏度流体中环状气泡形态不易于保持,易出现环状气泡的撕裂现象;随着距离参数的增大,自由表面和气泡之间的耦合效应逐渐减弱,气泡脉动周期增大,主峰和二次水冢尖峰的高度减小,同时主峰和射流的宽度逐渐增大。[结论]所做研究可为气泡在不同黏性流场中的演变机理提供参考。

不同爆心距条件对砌体结构振动响应规律研究

为了探究受爆破振动影响的楼层振速峰值分布规律,以青岛地铁1号线贵西区间隧道爆破工程为背景,通过对7层砌体结构的现场振动监测,采集爆破振动数据,并依据实际工况建立4种不同爆心距的数值模型,分析建筑物振动响应特征。结果表明:当爆心距分别为2、10、35 m时,砌体结构顶层的合振速呈现相对放大现象,相对放大系数依次为2.02、1.80、1.67;随着爆心距的不断减小,砌体结构的相对放大系数呈递增趋势;当爆心距为70 m时,砌体结构振速随着楼层的增高呈降低趋势,表现为绝对降低现象。研究结果对在实际工程中判断建筑物是否超过安全允许振速及城区隧洞开挖爆破参数优化具有一定的指导意义。

钢-混凝土-钢组合板爆炸冲击响应分析

基于钢-混凝土-钢(SCS)组合板爆炸试验,采用LS-DYNA显示动力分析程序对其抗爆性能进行数值模拟。通过与试验的对比验证了模型的可靠性,采用该模型分析了比例距离、混凝土厚长比、钢板厚度以及混凝土强度变化对SCS板动态响应的影响。结果表明,该有限元模型能够有效模拟SCS板在爆炸荷载下的动态响应过程;随着比例距离的减小,SCS板跨中位移逐渐增大,并由弹性变形转变为塑性变形;增加混凝土厚长比和钢板厚度能够有效降低SCS板跨中位移,而混凝土强度变化不会对SCS板抗爆性能产生显著影响。

水下爆炸作用下高桩码头损伤特性数值模拟研究

水下爆炸是战时威胁高桩码头保障能力的主要打击手段,为研究高桩码头外侧水下爆炸作用下的毁伤效应,通过有限元软件建立了高桩码头水下爆炸全耦合模型,分析了码头外侧水下接触爆炸和不同爆距爆炸下高桩码头的破坏过程和毁伤现象,探讨了爆炸距离对高桩码头的毁伤效应的影响规律。研究表明:外侧水下爆炸作用下,高桩码头桩基的顶部和炸深区域为主要毁伤部位,爆距直接影响桩基的破坏模式和高桩码头的毁伤程度。当炸药接触桩基爆炸时,临近桩基中部接触炸药区域冲切破坏,桩顶剪切破坏,横梁以及梁板连接区域轻微毁伤,比例爆距小于0.82时,由于桩基的桩顶或桩中断裂而失去承载能力,随着爆距的增加,临近桩基中部由冲切破坏转变为弯曲破坏,桩基顶部由剪切破坏转变为弯剪破坏;当比例爆距大于1.23时,仅临近桩基中部和顶部出现混凝土保护层破碎或塑性变形,横梁与桩基连接区域轻微损伤,不同爆距下桩顶和桩基炸深区域均为易损伤部位。

基于无人机量测的深孔爆破振速预测方法

当前高速公路路基爆破的智慧化水平较低,导致路基深孔爆破时爆破振速难以实现精准预测,爆破施工优化效果较差。依托济青中线潍青段路基深孔爆破工程,引入无人机航测技术,建立路基爆破的三维模型,提出基于无人机摄影量测和三维模型重建技术的爆心距计算方法,实现了路基深孔爆破的爆心距精准计算;通过爆破振动监测获取振速数据,基于药量、振速、爆心距等参数建立深孔路基爆破的振速预测方法,有效提高爆破振速预测公式的拟合度和精准度,为路基爆破智慧化设计优化、施工决策及现场安全管理提供科学依据。

水下爆炸气泡上浮量预报研究

采用理论分析与水下爆炸试验相结合的方法,对水下爆炸气泡上浮量进行了研究。首先,根据无量纲化气泡上浮量与脉动周期正比例关系,推导出了基于测量周期的气泡上浮量计算公式;根据气泡上浮量测量结果,对无限水域气泡上浮量计算公式进行修正,得到了考虑边界条件影响下气泡上浮量计算公式。其次,基于测量周期计算得到了水下爆炸气泡上浮量,经与试验测试结果进行比对,两者吻合较好;基于上浮量、冲击波峰值计算得到了气泡脉动实际峰值,进而得到了气泡脉动实际峰值与测量峰值之间的比例系数;基于测量冲击波峰压和修正后气泡峰压计算得到了上浮量,并由于脉动周期测量值计算得到的上浮量进行比较,两者平均误差仅为3.68%。最后,考虑边界条件的影响,对小当量装药的上浮量进行了测试,试验测试与理论计算结果平均误差为7%。研究表明:底部的存在使气泡周期变大,底部的吸引作用使上浮量变小,导致上浮量计算结果存在一定偏差;空化作用的影响,导致气泡脉动峰压测量值偏大;理论计算值与试验结果偏差在工程允许范围内,表明了论文中提出的计算模型可应用于工程实际。

爆炸冲击波与水膜相互作用的试验研究

为了研究爆炸冲击波与水膜的相互作用,基于水平激波管搭建冲击波与水膜相互作用的试验平台,设计一个水膜发生器,能够产生厚度为8 mm的稳定水膜。研究了1.31和1.42马赫的入射冲击波分别与距管口45、55和65 mm处的水膜相互作用,并采用纹影仪和高速摄影机对冲击波与水膜的相互作用进行了可视化研究,采用压力测试系统记录水膜前方和后方20 mm处的压力和冲量变化。研究结果表明:水膜前方的压力变化取决于冲击波的反射,且水膜产生的反射波低于刚性-固体壁面产生的反射波;水膜后方的压力变化取决于受冲击的水膜破碎时所吸收的能量,且这部分能量主要来源于冲击波后高速气流的作用,冲击波本身的作用并不明显;水膜后方的峰值压力和冲量显著增强,峰值压力的增强效果能达到50%以上,冲量的增强效果能达到10倍以上;水膜距管口越远,对峰值压力的增强效果越显著,对冲量的增强效果越微弱。