JOB-9003炸药"激热"冲击损伤破坏及超声特征

进行了未经热处理的JOB-9003塑料粘结炸药(PBX)标准压缩试样的"激热"冲击损伤破坏试验,对试样热冲击试验前后的超声波特性参量进行了检测,试验显示出JOB-9003炸药存在一个明显的"激热"冲击损伤破坏临界温度差,并获得了试样热冲击损伤破坏的超声波参量特征.     

HMX基PBX的温度环境适应性

对HMX基PBX进行了-40～+75℃温度循环试验和温度冲击试验,采用超声波参量检测方法对炸药的内部损伤进行了分析和表征。并对环境试验前后炸药的力学性能和破坏方式进行了实验研究。结果表明,温度循环试验和温度冲击试验将导致HMX基PBX产生热损伤,使HMX基PBX压缩强度轻微下降,而对拉伸强度影响不大。     

PBX炸药细观损伤的实验研究

为研究PBX炸药在冲击作用下的物理损伤、化学损伤及成热的物理机制,采用炸药爆炸驱动隔板实验技术对PBX炸药进行了冲击压缩实验,回收炸药试样并对其不同位置处的断面形貌进行SEM分析.结果表明,随着冲击能量的增加,其温度效应的影响越来越显著,损伤模式从物理损伤向化学损伤过渡.这为XDT问题中的"热点"形成机制等研究提供了实验基础.     

RDX基含铝炸药的剪切试验及损伤模式

利用分离式霍普金森压杆(SHPB)试验设备及剪切装置,对RDX基含铝炸药进行剪切试验,获得了剪切力随时间的变化规律以及剪切应力,结合工业CT图像及电镜扫描(SEM)图像分析,探讨了剪切加载条件下,炸药试样破坏的宏观及微观损伤模式。结果表明,在剪切作用下,炸药装药的轴向应力-应变曲线出现两个阶段:第一阶段,较小的应变下,应力快速增加,最大值为50~60MPa;第二阶段,随着应变的增加,应力先增大后卸载。试验加载过程中的剪切应力为38~73kN;剪切应力小的试样,剪切带主要集中于加载面的中部,剪切应力大的试样,剪切带主要集中于剪切面附近;试样厚度较小时,损伤模式主要是晶体的微裂纹及晶体与黏结剂基体的脱粘,试样厚度增加时,损伤模式主要为晶体的多种形态。     

RTM碳纤维复合材料宏观缺陷超声表征及分析

以RTM碳纤维复合材料为研究对象,通过超声特征扫描成像系统对大量试样进行检测,由理论可知,超声波的反射特性会随着宏观缺陷类型的不同而不同。首先从理论上分析各缺陷的反射特性,然后找出不同的宏观自然缺陷,归纳总结各种缺陷对应的图像特点,再采取破坏方法对试样进行切割、打磨,通过显微镜观察不同缺陷形貌特征。结果表明,超声特征扫描成像系统可以检测并分辨出不同的宏观缺陷,通过观察缺陷金相图可知不同类型缺陷形貌特征也各不相同,为RTM碳纤维复合材料宏观缺陷检测及形貌研究提供了一种可行方案。     

塑料制品超声波焊接表面热破坏行为研究

对塑料制品超声波焊接表面热破坏行为进行了研究。功率超声波本身特性及热传导作用致使焊件表面造成热破坏,它与工艺参数设置不当有关,提出了减少塑料制品表面热破坏的措施。     

炸药损伤及损伤炸药环境适应性的实验研究

为研究炸药损伤及损伤炸药的安全性,对有边界限定的压装PBX炸药,采用高、低温贮存、温度冲击的方法进行温度损伤实验;采用冲击、振动、跌落的方法进行冲击损伤实验,并利用CT扫描对炸药的损伤情况进行观察;同时通过冲击、振动、跌落实验,对损伤炸药的环境适应性进行了实验研究.结果表明,低温贮存、温度冲击、冲击实验都会使炸药产生裂纹损伤,温度冲击条件下更易引起炸药裂纹损伤.存在裂纹损伤的炸药经过环境适应性实验,未发生爆炸或燃烧现象.     

玻璃纤维复合材料层合板冲击后的压缩强度

对不同厚度的二维编织环氧玻璃纤维层合板进行落锤冲击试验及冲击后压缩破坏试验,以研究低速冲击对复合材料层合板剩余压缩强度(CAI)的影响。用透光描影及热揭层方法对冲击损伤形式进行描述。讨论了损伤宽度、损伤面积与冲击能量及剩余压缩强度、模量间的关系,并建立有限元模型,采用开口等效及软化夹杂等分析方法对材料的冲击后压缩强度值进行估算。     

摩擦效应对某PBX炸药动态力学性能的影响

基于分离式霍普金森压杆(SHPB)围压加载下的试样受力模型,考虑试样与套筒间的摩擦效应,建立了动态力学性能参量(动态泊松比及动态杨氏模量)的修正方法,并以某浇注PBX炸药为例,分别以常规方法和修正方法计算了4种试样的动态力学性能,并进行了对比。结果表明,对于实验所用的浇注PBX炸药,在应变率300~2000s~(-1)内,修正方法与常规方法所获得的动态参量误差不超过5%,可以忽略摩擦效应对此PBX炸药动态参量的影响。     

基于声发射不同骨料含量胶结充填体损伤过程试验研究

利用RMT-150C型岩石力学测试系统与PCI-2声发射仪,对纯尾砂、骨料质量分数20%及40%三种胶结充填体试样进行单轴压缩破坏声发射监测试验,研究了3种不同骨料含量胶结充填体力学特性以及基于累计声发射事件率的损伤演化特征。试验结果表明:含骨料试样破坏脆性特征更加明显,同时骨料含量的变化在一定程度上影响了胶结充填体承载损伤演化速度,对其承载能力有较大影响;纯尾砂试样与含40%骨料试样在峰值应力前不同阶段均出现不同幅度的声发射活跃现象,可作为矿山充填体声发射监测破坏预警的前兆信息;适量骨料的加入可起到提升充填性能的作用,但声发射事件率作为预警前兆信息则可能失效。     

Estimating impact breakup and initiation parameters of condensed explosives

The existence of two critical states of an explosive material associated with the weakening of a layer of explosive and the excitation of an explosion is examined qualitatively on the basis of the general concepts of mechanical deformation and destruction of a thin layer of viscoplastic explosive material under impact and the resulting dissipative and chemical heat release. The critical conditions, i.e., the impact energy and the pressure created by it in the material, for destruction and initiation of the explosive material are estimated. The results are used to explain experimental data on the dependence of the initiation parameters on the thickness of a layer of explosive material which are of practical interest for analyzing tests of the sensitivity of explosive systems to mechanical interactions. Translated fromFizika Goreniya i Vzyva, Vol. 35, No. 2, pp. 88–95, March–April 1999.     

Acoustic emission from the initiation of plastic deformation of Polyethylenes during tensile tests

The acoustic emission (AE) technique has been used in the aim to detect and to observe the initiation of plasticity and damage of several Polyethylenes (PE) during tensile tests. The detection of acoustic signals originating from the deformation of the material is challenging since PE samples strongly attenuate ultrasonic waves. A weak acoustic activity has been recorded during the tests. The use of two types of PE specimens and two methodologies based on the elimination and the discrimination of spurious sources has shown that most of the AE signals truly originate from the plastic deformation of materials. We also observed that the acoustic activity increases with strain rate. Besides, some AE signals are located along the specimen length during tensile tests at high strain rate. The acoustic activity increases strongly with the crystallinity. Micro-cavities, formed before the yield point of PE samples with high crystallinity in particular, likely initiate the release of acoustic energy. In addition, some signals are collected on PE samples, which do not exhibit a formation of cavitation. Hence, the shearing of crystallites and/or the fragmentation of crystalline lamellae may also be a source of the release of acoustic energies.     

火炸药废水处理技术研究进展

火炸药在生产及销毁过程中会产生大量有毒、化学成分复杂且生物难以降解的污染物,对人类及其它生物体造成生命威胁。针对火炸药废水的产生原因、主要特点及处理现状进行了分析,重点介绍了物理法、化学法和生物法废水处理技术的研究现状,指出2种或多种废水处理技术相结合实现废水的快速、高效、无污染处理是未来火炸药废水处理技术的发展方向。     

Low‐velocity impacts in continuous glass fiber/polypropylene composites

The low‐velocity impact behavior of a continuous glass fiber/polypropylene composite was investigated. Optical microscopy and ultrasonic scanning were used to determine the impact‐induced damage. At low impact energy, the predominant damage mechanism observed was matrix cracking, while at high energy the damage mechanisms observed were delamination, plastic deformation, which produced a residual specimen curvature, and a small amount of fiber breakage at the edge of the indentation on the impacted face of the specimens. The impact load vs. time signals were recorded during impact and showed that the load corresponding to the onset of delamination was independent of the impact energy in the range tested. The load at which the onset of delamination occurred corresponded to the values obtained by performing a linear regression of the delaminated area, obtained by ultrasonic scanning, as a function of the impact force. Tensile and flexural tests performed on impacted specimens showed that the tensile and flexural residual strengths and the flexural modulus decreased with increasing incident impact energy, while the post‐impact residual tensile modulus remained constant. The dynamic interlaminar fracture toughness was evaluated from the critical dynamic (impact) strain energy release rate of specimens with a delamination simulated by an embedded insert. The results are compared with the interlaminar fracture toughness values obtained during subcritical steady crack growth.     

Controlling surface defects in assessing thermal damage to porous ceramics using the luminescent capillary method

Conclusions The results cited indicate the effectiveness of the method of capillary defectoscopy based on the use of ultrasonic capillary effects for testing the surface defects in assessing thermal damage to dense ceramic materials having a porous structure. The use of capillary control data in carrying out mechanical tests of heat damaged specimens may substantially increase the reliability of the test results.Translated from Ogneupory, No. 5, pp. 12–14, May, 1984.     

纳米LaCoO3对RDX基混合炸药的热分解特性和感度的影响

用DSC和DTA研究了LaCoO3对含AP的RDX基混合炸药热分解特性的影响。结果表明,纳米LaCoO3对含有AP的RDX基爆炸混合物的热分解具有一定的催化作用;纳米LaCoO3使RDX基混合炸药的撞击感度和热感度降低,摩擦感度增大。     

Cumulative damage of reinforced concrete subjected to repeated impact

This study was performed to develop methods of measuring the cumulative damage of steel reinforced concrete slabs subjected to repeated impact. Cumulative damage was monitored by measuring the crater depth and the reduction in ultrasonic pulse velocity across the impact region. Crater depth generally increased with increasing number of impacts and therefore was determined to be a reasonable indicator of cumulative damage. The percent reduction in velocity generally increased with increasing number of impacts up to about 40 percent or more of the total number of impacts to failure. Beyond that, interpretation of the ultrasonic results with respect to the failure mechanism appears necessary. The addition of steel fibers to the bar grid reinforcement resulted in substantial increases (about 2 to 7 times or more) in the total number of impacts to failure as compared to specimens with only bar grid or expanded metal placed at the midpoint of the slab thickness.     

The Flow Characteristics of High Explosives

A comparative study of flow properties of the explosive compound RDX is presented. The results were used to identify desirable free-flowing characteristics in the powders. Various static and free-flowing tests were conducted on the explosive powders. The results suggest that flow properties of the RDX powders tested were not influenced by particle size and surface roughness. However density, moisture content and cohesive strength between the particles had some effect on the flow properties. An increase in moisture content and cohesive strength of the particles reduced the flow rate. Whereas an increase in bluk density of the powders increased the flow rate.     

Application of the Scott Hydrodynamic Model for Analysis of Results of Impact Testing of High-Explosive Specimens

The solution of the hydrodynamic problem of a non-Newtonian medium flow squeezed by two approaching parallel disks, which was previously obtained by Scott, is used to determine the strain and ignition parameters of explosive specimens in drop tests at the lower threshold of their sensitivity.