PBX 9501炸药动态增强因子的预测公式

为量化应变率效应对PBX炸药力学性能的影响,引入动态增强因子的概念。以PBX 9501炸药为研究对象,总结并收集了其在不同温度和不同应变率下的压缩强度和拉伸强度数据,利用WLF时温等效原理将不同温度下的数据换算成室温条件对应应变率下的值,补充了缺少的强度数据。基于实验数据,分别拟合了PBX 9501炸药压缩强度和拉伸强度的动态增强因子的预测公式。结果表明,随着应变率的变化,PBX 9501炸药的压缩强度和拉伸强度在双对数坐标下均呈现双线性增长趋势,但是压缩强度和拉伸强度的变化趋势是不同的。在给定的应变率范围内,压缩动态增强因子的最大变化值超过40,而拉伸动态增强因子的最大变化值小于10。用这些经验公式,可预测不同应变率下PBX 9501炸药的强度变化,便于工程应用。     

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。     

含预制缺陷PBX炸药的力学性能及破坏形式

为探索裂纹缺陷对炸药力学性能和破坏形式的影响,以压装HMX基PBX炸药为对象,采用改进后的圆弧巴西试验,研究了不同预制缺陷条件下炸药的破坏过程,并与无缺陷炸药的试验结果进行对比。结果表明,在所研究的范围内,压装PBX炸药的力学强度随缺陷的空间位置变化显著,最高降幅达75.3%;不同缺陷下炸药的破坏形式差异较大,缺陷与加载方向存在夹角时,炸药存在二次承载的现象,且裂纹从缺陷端部向炸药加载面扩展。     

低拉伸应力下PBX的老化实验研究

为了研究PBX在超长时低应力拉伸下的老化问题,设计了一种能进行超长时恒定拉伸应力加载的新实验装置,并验证了装置的可靠性.对以HMX和TATB为基的PBX炸药进行不同拉伸应力下的常温长时加载和45℃下的高温长时加载试验,研究了应力水平和温度环境对样品抗长时拉伸能力的影响,比较了相同条件下模压样品和等静压样品抗长时低应力拉伸的能力.结果表明,本实验能够有效研究PBX在低应力拉伸下的承载能力,并获得了在一定温度一定拉伸应力条件下PBX的老化寿命.     

基于液压致裂法的PBX炸药内部拉伸应力测试可行性研究

为了满足高聚物黏结炸药(PBX)内部拉伸应力测试的需要,利用液压致裂法和孔边应力状态修正实验,建立了基于液压致裂法的PBX炸药内部拉伸应力测试方法。为验证测试方法的有效性,采用材料万能试验机模拟构件内部拉伸应力,结合自主搭建的PBX液压致裂测试平台,开展了不同拉伸应力下的液压致裂应力测试实验。结果表明,直接利用液压致裂法能定性描述PBX炸药的内部拉伸应力,测试结果与预加拉伸应力有较好的相关性(相关系数为98.90%),但不能定量描述;通过对带孔试样进行单轴拉伸实验,获得孔边有效应力集中系数,对液压致裂法的孔边应力状态进行修正,修正后的应力值与预加应力吻合较好,平均相对误差10.67%。建立的测试方法不受测试深度限制,理论上可以测出拉伸应力的大小和方向,是一种基于液压致裂法的PBX炸药内部拉伸应力定量测试方法。     

RDX基PBX炸药烤燃试验与数值计算

对RDX基PBX炸药进行了烤燃试验,建立了炸药烤燃计算模型,其中加入了Frank-Kamenetskii、SestakBerggreen和McGuire-Tarver反应模型,采用流体力学计算软件Fluent进行了数值模拟.试验结果表明,PBX炸药在1K/min升温速率下发生剧烈反应的时间为176.0min,此时试样中...     

碳纤维支杆与金属接头两种连接方式的拉伸试验

碳纤维支杆与金属接头的连接方式通常有两种:胶接和胶-销连接。为了比较二者连接强度的大小,根据当前需求,设计并制作了拉伸试样,然后利用试验机对试样进行了拉伸试验。试验结果表明,胶接方式所能承受的最大拉伸载荷为42.25kN,连接强度为5.83MPa;胶-销连接方式所能承受的最大拉伸载荷为42.10kN,连接强度为5.81MPa。与胶接相比,胶-销连接对支杆和接头的连接强度没有较明显的提升,反而略有下降。     

低易损性PBX炸药烤燃试验方法研究

烤燃试验是评估和检验炸药易损性能的重要试验之一。通过分析炸药的安全可靠性及战场生存能力阐明了PBX炸药烤燃试验的意义和重要性,论述了PBX炸药烤燃试验国内外的发展现状,介绍了烤燃试验的方法,分析了影响烤燃试验结果的主要因素。     

不同老化阶段沥青混合料力学性能变化与调控

为了明确不同老化阶段沥青混合料力学性能的变化规律,通过间接拉伸试验研究了不同老化时期模量、强度的差异指数,并使用不同掺量的抗氧剂对其进行抗老化调控.结果表明:在相同试验温度下,模量对老化的敏感性高于强度,说明老化沥青混合料的破坏可能是因为模量不足而造成的;掺入抗氧剂均能提升老化前后的沥青混合料性能,当掺量为5％时,沥青...     

粘结剂增强对TATB基PBX力学性能的影响

采用熔融共混法制备了氟聚合物/增强剂复合粘结剂体系,考察了增强剂含量对复合粘结剂体系性能的影响。动态力学分析(DMA)结果显示,增强剂的玻璃化转变温度大大高于氟聚合物,复合粘结剂体系的储能模量随增强剂含量的增加而增加。随着增强剂含量增加,复合粘结剂体系的拉伸强度明显增加。采用水悬浮法制备了TATB基高聚物粘结炸药(PBX),探讨了粘结剂增强对其力学性能的影响。实验结果表明,随着增强剂含量增加,TATB基PBX的力学性能显著提高。当复合粘结剂体系中增强剂含量为20%时,PBX的力学性能最佳:20℃和60℃下压缩强度为32.15 MPa和20.00 MPa,60℃下劈裂强度为2.84 MPa。     

The preparation and characterization of porous alumina ceramics using an eco-friendly pore-forming agent

This work presents the preparation of porous alumina ceramics through the sacrificial phase method, using an eco-friendly material, namely waste coffee grounds, as a pore-forming agent. The effects of coffee grounds content in the green ceramic bodies on the linear and volumetric shrinkage, as well as the total and open porosity of the sintered product, were evaluated. The influence of the resulting porosity on mechanical properties of the prepared porous alumina was determined using Brazilian disk compression test for the determination of the indirect tensile strength of the prepared samples. Microstructure and pores morphology were characterized by scanning electron microscopy. Porosities in the range 35-54 vol% were achieved, by varying the coffee grounds content from 0 to 50 wt% in the green bodies. The indirect tensile strength of the final obtained porous alumina ceramic decreased accordingly from 57.4 MPa to 17.7 MPa.     

Dynamic tensile mechanical properties and failure mode of zirconium diboride-silicon carbide ceramic composites

Dynamic indirect tension experiments were performed on zirconium diboride-silicon carbide (ZrB₂−20%SiC) ceramic. Flattened Brazilian disc specimens of ZrB₂−20%SiC were prepared to conduct dynamic tensile tests using the modified Split Hopkinson pressure bar system. The tensile experiments were completed at the range of loading rates from 7.53 to 74.71 GP s⁻¹. The tensile experimental results revealed that the zirconium diboride-silicon carbide ceramic composite is rate-sensitive in terms of the tensile strength and failure mode. The dynamic tensile strength increases linearly with the loading rate and changes from 195 MPa at 7.53 GP s⁻¹ to 654 MPa at 74.71 GP s⁻¹. Moreover, the dynamic tensile strength decreases with the increase in critical fracture time, which conforms to Tuler and Butcher's fracture criterion. In dynamic experiments, a high-speed camera was used to examine the tensile failure process, and fragments were collected to analyze the dynamic tensile failure mechanism. The tensile fracture mode of ZrB₂−20%SiC obviously showed the sensitivity of the loading rate. The fragment size of ZrB₂−20%SiC ceramic decreased but the quantity of fragments increased as the loading rate increased.     

Combination of Brazilian test and digital image correlation for mechanical characterization of refractory materials

Flexibility of refractories is an interesting property to improve thermal shock resistance of refractories. It can often be obtained by promoting a nonlinear mechanical behaviour which reduces brittleness. Among industrial refractory materials developed in this aim, magnesia hercynite is of a particular interest for cement industry. As linings for rotary kilns, magnesia hercynite can be submitted to tensile and compressive stresses. Since tensile strength is usually much lower than compressive one for brittle materials, the mechanical characterization is, in such case, more significant in tension than in compression. To overcome difficulties involved by direct tensile test, an indirect tensile test (Brazilian test) has been applied here and combined to digital image correlation in order to measure kinematic fields on the surface of the sample during loading. This combination has allowed to accurately measure initial elastic properties (Young’s modulus and Poisson ratio), to detect crack initiation and to analyze fracture process.     

基于EFG方法的PBX炸药圆弧巴西实验的数值模拟

为了对准静态圆弧巴西实验过程中PBX试样的裂纹形成和扩展过程进行模拟,基于EFG方法和内聚力模型,利用LS-DYNA软件的隐式分析模拟计算了实验过程。结果表明,计算结果和文献报道的实验结果吻合较好,证明了该方法的可行性;采用线性内聚力模型可较好地描述PBX炸药的断裂过程,PBX试样的起裂发生在压缩载荷达到峰值后,随着压头的进一步压缩,试样中心的裂纹沿直径向压头方向扩展。     

聚醚醚酮核用电缆料拉伸性能测量不确定度评定

选择GUM法对核用电缆料聚醚醚酮(PEEK)薄膜的拉伸强度和断裂拉伸应变,进行测试结果的测量不确定度评定,分别从A类不确定度和B类不确定度进行评定,A类不确定度主要通过重复测试来分析PEEK试样的均匀性产生的测量不确定度,拉伸强度的B类不确定度主要考察了仪器设备引入的测量不确定度,断裂拉伸应变的B类测量不确定度还考察了测试结果的数值修约引入的测量不确定度。结果表明,厚度为1.00 mm的PEEK试样,拉伸速率为20 mm/min,拉伸强度的测试结果为112 MPa,k=2时,测量不确定度为5 MPa;断裂拉伸应变的测试结果为150%,k=2时,测量不确定度为10%。     

被动围压下PBX的冲击动态力学性能

采用铝套筒和TATB基PBX,应用霍普金森压杆被动围压试验方法,研究了PBX在围压下的动态力学响应,得到了该PBX不同应变率下的屈服强度.结果表明,随着应变率的提高,屈服强度有所提高;围压状态下PBX承受的应力远高于无围压状态,变形从脆性向塑性转变,样品未发生明显的破坏.     

Effect of electron beam radiation on the performance of biodegradable Bionolle-jute composite

To study the radiation effect on the physical, thermal, mechanical and degradable properties of biodegradable polymer Bionolle (chemosynthetic polyester poly(1,4-butylene succinate)), Bionolle films prepared by compression molding process and were irradiated with electron beam (EB) radiation of different doses. Gel content was found to increase with increase of radiation dose. Tensile strength of Bionolle was enhanced when Bionolle film was exposed under 20 kGy radiation. The loss of tensile strength of both unirradiated and irradiated Bionolle is 70% and 8% due to thermal aging at 70°C for 30 days. Both irradiated and unirradiated films of Bionolle were subjected to different degradation test in compost (soil burial), enzyme and storage degradation both in outdoor and indoors conditions. The loss of weight due to soil (compost) degradation test decreased with increase of radiation dose. The loss of weights of irradiated samples were found to be very less within the first three months of compost degradation. After 120 days, tensile strength of the Bionolle films irradiated at 20 kGy and 100 kGy were 68 MPa and 40 MPa, respectively, compared to the value (30 MPa) of the unirradiated Bionolle samples. Loss of tensile strength of irradiated Bionolle due to storage degradation like in roof, ground and indoors was minimum compared to unirradiated Bionolle. The weight loss due to enzymatic degradation was found to be decreased with increase of radiation dose. The tensile strength of jute reinforced Bionolle composites (23 wt.-% jute content) irradiated at 20 kGy was found to be higher (22%) than that of an unirradiated composite.     

在单方向往复低剪切力场中生成双向自增强HDPE试样的研究——(Ⅰ)试样制备及工艺条件对力学性能的影响

介绍在动态保压注塑成型技术提供的单方向往复低剪切应力场作用下来制备双向自增强试样。作者设计并制造了成型装置，初步研究了其成型原理、成型工艺、探讨了自增强效果与各工艺条件之间的关系。结果表明，采用本文所述的动态保压注塑成型技术显著提高了ＨＤＰＥ试样的力学性能——流动方向和垂直流动方向的拉伸强度均从２５ＭＰａ提高到３６ＭＰａ以上，达到了双向自增强的效果。自增强ＨＤＰＥ试样的拉伸强度强烈依赖于熔体的流动条件：流动方向的拉伸强度随液压站输出压力的提高而提高，垂直流动方向的拉伸强度则有一个对应最大拉伸强度的液压站输出压力；模具温度对拉伸强度的影响与压力对拉伸强度的影响相类似；熔体温度的提高有利于两个方向拉伸强度的提高；保压周期太长或太短均会使拉伸强度下降。