NEPE推进剂拉伸断裂行为研究

通过单向拉伸力学性能实验,考察了不同测试温度和不同拉伸速率条件下NEPE推进剂力学性能的变化情况。采用扫描电镜(SEM)和原位拉伸SEM观察了推进剂拉伸断面形貌。结果表明,在低温测试条件下,NEPE推进剂最大伸长率较常温条件下显著降低,最大抗拉强度较常温和高温条件下显著升高,NEPE推进剂的破坏主要表现在黏合剂的撕裂和固体颗粒的断裂;在高温、慢拉伸速率的测试条件下,推进剂断裂时结构被破坏的程度较大,NEPE推进剂的破坏首先发生在固体颗粒堆积处,再到黏合剂网络结构。推进剂断裂的过程是推进剂拉伸取向与裂纹扩展之间的竞争过程。     

NEPE推进剂热安全性的尺寸效应

为了解NEPE推进剂热安全性的尺寸效应,在不同温度下对不同尺寸的NEPE推进剂药柱进行了热爆炸试验,测得其热爆炸延滞期,并计算得到不同尺寸NEPE推进剂药柱在90、100、110、120℃下的热分解反应速率;通过在药柱内部布置热电偶监测了尺寸为Ф100mm×100mm和Ф150mm×150mm药柱在90℃和100℃环境温度下的内部温度变化。结果表明,当温度高于76.2℃时,NEPE推进剂药柱的尺寸越大,反应速率常数越大;活化能与药柱的比表面积呈线性相关,比表面积越小,活化能越大,当NEPE推进剂药柱的比表面积小于0.02mm-1时,活化能(Ea)为179.3kJ/mol,指前因子(A)为4.62×1019s-1。硝酸酯增塑剂的存在是NEPE推进剂在200℃以下发生热爆炸的主要原因。     

低铝含量NEPE推进剂燃烧性能研究

研究了铝粉含量为8％的NEPE推进剂。采用配浆浇铸法制备推进剂，并用恒压静态燃速仪测试了推进剂的燃烧性能。考察了NG／DEGDN的比例、AP粒度、HMX粒度对燃速及燃速压力指数的影响。发现增大NG／DEGDN的比例、减小AP粒径或增加细粒度AP含量，将提高NEPE推进剂的燃烧速度，压力指数升高；而HMX粒度降低，NEPE推进剂燃速降低，压力指数降低；不同来源的PbCO3对NEPE推进剂燃烧性能影响很大。     

Experimental Investigation on Laser Ignition and Combustion Characteristics of NEPE Propellant

The ignition and combustion property of solid propellant is the main content in internal ballistic research, which has a great significance for propulsion application and combustion mechanism. In this study, the detailed gas‐phase reaction mechanism of Nitrate Ester Plasticized Polyether Propellant (NEPE) was developed. It is helpful to understand the intricate processes of solid‐propellant combustion. The factors which may have influences on ignition delay time and temperature distribution of propellant surface was analyzed by laser ignition experiment. Using high‐speed camera and an infrared thermometer, the ignition and combustion process and the surface temperature distribution of NEPE propellant under laser irradiation were measured. Laser heat flux, ambient pressure and initial temperature of NEPE propellant have an influence on the ignition delay time and the surface temperature. Results show that the ignition delay time decreases with the increase of laser heat flux, ambient pressure and initial temperature of NEPE propellant. At the same time, with the increase of laser heat flux, the influences of ambient pressure and initial temperature on the ignition delay time decrease. Besides, laser irradiation, ambient pressure and initial temperature have significant influences on the surface temperature distribution of the propellant.     

三官能度PET对胶片和NEPE推进剂力学性能的影响

为了改进NEPE推进剂常温力学性能,研究了三官能度环氧乙烷-四氢呋喃共聚醚(PET)对PET/N100胶片及NEPE推进剂力学性能的影响。结果表明,在胶片固化比R分别为1.0、1.1、1.2时,随着三官能度PET(f=3.2)在预聚物中所占质量分数的增大,胶片交联密度相应提高,最大增幅达45.69%,胶片强度随之提高,最大抗拉强度σm增幅达101%,断裂伸长率εb相应减小;三官能度PET应用于NEPE推进剂时,能有效改善推进剂常温力学性能,强度与延伸率均有所提高,当粘合剂预聚物中三官能度PET的质量分数达62.5%时,σm可达0.570 4 MPa,比空白样提高了50%以上。     

Study of the Effects of Aging under Humidity Control on the Thermal Decomposition of NC/NG/BTTN/RDX Propellants

The effects of aging under controlled humidity on the thermal decomposition of two nitrate ester/RDX propellants are examined. Propellant samples are artificially aged at 60 °C and 70 °C at various levels of relative humidity. Differential scanning calorimetry is used to study the post aged samples to determine the activation energy of the peak exotherm and peak temperature of these events. For each humidity level, differential scanning calorimetry is conducted on an aged and an unaged sample that is conditioned to the humidity of the environment to distinguish between aging effects and residual moisture effects. Nitrate ester stabilizer depletions rates are presented as a function of aging and humidity. The results of the study show that moisture level during aging irreversibly alters the activation energy of the primary heat release events and significantly influences the stabilizer depletion rates.     

NEPE推进剂老化过程中结构与力学性能的关系

为考察NEPE推进剂的老化特性,在60,65,70和75℃老化了推进剂样品,研究了其在常温时的抗拉强度σm,初始模量E0与黏合剂母体凝胶质量分数ω、化学交联密度υe、物理交联密度υp之间的关系.用动态热机械分析仪(DMA)测试了多个频率下老化样品的损耗因子tanδ、损耗模量半高峰宽D h/2.结果表明,高温加速老化过程中NEPE推进剂样品σm和E0下降的原因是推进剂黏合剂母体结构的ω,υe 和υp下降.NEPE推进剂降解和解聚由黏合剂母体结构变化引起.     

NEPE-5复合固体推进剂物理老化寿命的预估

用动态热机械分折仪(DMA)测定了老化NEPE—5推进剂的动态力学性能，确定了物理老化对其力学性能的影响，并以此作为失效的主要模式。依据时间一温度叠加原理，老化NEPE—5的贮能模量、贮能柔量和损耗柔量沿频率(横坐标)进行叠合得主曲线，而这些主曲线沿纵坐标与未老化的主曲线进行叠合所得的垂直位移因子随老化时间的增长有突变点，把该点所对应的老化时间视为失效时间。同时根据WLF方程获得了老化活化能，依据所得的话化能和失效时间，利用点斜法预估了NEPE—5推进剂的物理老化寿命。     

环境气体氧含量对NEPE推进剂激光点火过程的影响

为研究环境气体氧含量对硝酸酯增塑聚醚(NEPE)推进剂激光点火过程的影响,采用CO2激光辐射点火并利用高速摄影仪记录NEPE推进剂的点火过程,讨论了环境气体氧含量对NEPE推进剂初焰位置与点火延迟时间的影响。结果表明,当环境气体氧含量小于NEPE推进剂热解产物中氧化性气体含量时,NEPE推进剂点火的气相反应发生在推进剂热解产物的分散区,初焰紧靠NEPE推进剂表面,环境气体氧含量变化不影响NEPE推进剂的点火延迟时间;当环境气体氧含量大于NEPE推进剂热解产物中氧化性气体含量时,NEPE推进剂点火的气相反应发生在推进剂热解产物与环境气体的扩散区,初焰远离NEPE推进剂表面,此时由于扩散区氧含量高于NEPE推进剂热解产物分散区氧含量,NEPE推进剂的点火延迟时间减小。     

影响NEPE推进剂药柱结构完整性主要参数的分析

为研究某型NEPE推进剂药柱受温度、内压及过载等载荷联合作用下的结构完整性,基于近似不可压三维热粘弹性有限元法,建立了发动机药柱的三维有限元计算模型.针对NEPE推进剂的力学特性,采用最大应变能准则给出了不同工作温度下药柱结构的安全系数,讨论了松弛模量与泊松比两种材料参数对药柱结构完整性的影响.结果表明,工作温度较高时药柱结构的安全系数较低,适当降低推进剂的松弛模量或增大泊松比可提高药柱结构的完整性.     

铅盐对无烟NEPE推进剂燃烧性能的影响

通过测定不同压力下推进剂的燃烧性能以及熄火表面元素分析,研究了3种铅盐(LF、LP和LC)对无烟NEPE推进剂燃烧性能的影响。结果表明,LF、LP或LC使该推进剂的压强指数在3～5MPa压力范围内降至0.33～0.48,5～12MPa降至0.18～0.58。推进剂熄火表面元素分析结果表明,LF和LP中的铅元素在推进剂燃烧过程中更易于在燃面富集,而LC中铅元素在燃面上的富集程度相对较弱,这与3种铅盐对无烟NEPE推进剂的燃速催化效果一致。     

B12H12［N(C2H5)4］2对NEPE推进剂燃烧性能的影响

研究了硼氢化合物 B1 2 H1 2 [N(C2 H5 ) 4] 2 对 NEPE推进剂燃烧性能的影响 ,采用 DSC分析了 B1 2 H1 2 [N(C2 H5 ) 4] 2 与 NEPE推进剂主要组分硝酸酯的相容性以及对推进剂固化反应的催化作用和对高氯酸铵、硝胺常压热分解的催化作用 ,并利用恒压静态燃速仪测试了推进剂在 4～ 1 1 MPa的燃烧速度和燃速压力指数     

Active Sensing for Monitoring the Properties of Solid Rocket Motor Propellant Grains

Aging induced changes in the mechanical properties of solid propellant can lead to defects, such as cracks and grain‐liner separations, that limit the service lifetime of solid rocket motors. The use of embedded sensors is one approach that is being explored by various researchers to augment legacy inspection and prediction methods. We present herein an active sensing technique that is particularly suited for monitoring the properties of solid propellant, as it does not introduce electrical wires into the motor. Based on the use of magnetic induction for excitation and an optical fiber Bragg grating sensor to measure deformation, the method can be used to characterize the properties of a material with which it is in contact. In this paper, we first present proof‐of‐principal experiments demonstrating the utility of the method in characterizing the visco‐elastic properties of an adhesive, and in following changes in viscosity of an epoxy resin during cure. We next apply the method to solid propellant, and present data demonstrating that the method can be used to measure a deflection‐load curve of an aluminized HTPB propellant. In addition, we also show that the observed strain rate sensitivity matches that found in the literature and that the method had more than adequate resolution to observe the expected changes in material properties due to aging.     

高氮量单基火药老化过程中分子量与特性粘度的变化规律

用体积排除色谱和毛细管粘度计研究了高氮量单基火药在加速老化过程中分子量、分子量分布及特性粘度的变化规律。结果表明：老化过程中高氮量单基火药的分子量和特性粘度与老化时间都成负指数函数的关系;将高氮量单基火药老化过程中的分子量与特性粘度进行了对比分析,给出了［η］与Ｍ的关系。对高氮量单基火药的生产和贮存性能的研究有一定的参考价值。     

铜盐和碳黑对微烟NEPE推进剂燃烧性能的影响

通过测定不同压力下推进剂的燃烧性能及熄火表面元素分析,研究了两种铜盐（AD和BC）和3种碳黑对微烟NEPE推进剂燃烧性能的影响.结果表明,适量AD可改善推进剂的燃烧性能,使推进剂在3～20 MPa压力范围内的压强指数降至0.45以下;AD在12～18 MPa压力范围内比等量BC对微烟NEPE推进剂燃烧性能的催化作用弱,这可能与AD所含铜元素在燃面的富集程度小于BC有关.3种碳黑均能改变微烟NEPE推进剂在3～18 MPa压力范围内的燃速.增加乙炔碳黑含量可使推进剂在3～20 MPa压力范围内的燃速提高,压力指数降低.     

含硝仿肼的固体推进剂能量特性研究

研究了三种含硝仿肼 (HNF)的固体推进剂 HNF/GAP/A1、NC/NG/HNF/RDX、NC/NG/HNF/RDX/Al的能量特性 ,绘制了等性能三角图 ,可形象、直观地看出这类推进剂的比冲、燃烧温度与配方组分之间的关系     

增强热塑性塑料管材高温水浴老化性能研究

老化易使高分子链断裂,使材料变脆、脱层、变色,严重制约了塑料管材在高温、高湿工况下的应用.以交联聚乙烯PEX、耐热聚乙烯PE-RT和高密度聚乙烯PE100为研究对象,进行90 ℃水浴老化.采用万能力学试验机、差示扫描量热仪、维卡软化温度测定仪研究了三种材料老化前后力学性能变化和耐热行为.结果表明,在90 ℃热水浴老化9...     

高温高盐对阳离子双子表面活性剂表面活性的影响研究

考察了25℃条件下商品化阳离子双子表面活性剂PF-CGS在纯水、饱和NaCl盐水及含1000mg·L-1Ca2+、Mg2+的饱和NaCl盐水溶液中的表面张力行为,并对上述条件下的表面活性剂溶液在130℃下热滚16h后测定表面张力以进行对比研究。研究发现,与在纯水中的表面活性相比,随着无机盐的加入,PF-CGS溶液的CMC、C20和γCMC均降低,表面活性升高;经高温老化后的PF-CGS溶液的(CMC无明显变化,但CMC和C20均比老化前有所下降,表面活性有一定程度提高。上述实验结果表明,高温、高盐不会削弱阳离子双子表面活性剂PF-CGS的表面活性,该类表面活性剂完全可以适用于高温、高盐的油气开采环境。     

陶瓷砖断裂模数测量结果的不确定度评定

对陶瓷砖断裂模数测量不确定度的来源进行了分析,并对各不确定度分量进行了分析和量化,求得合成标准不确定度和扩展不确定度分别为10.04%和20.08%。     

Effects of Tenascin C on the Integrity of Extracellular Matrix and Skin Aging

Tenascin C (TNC) is an element of the extracellular matrix (ECM) of various tissues, including the skin, and is involved in modulating ECM integrity and cell physiology. Although skin aging is apparently associated with changes in the ECM, little is known about the role of TNC in skin aging. In this study, we found that the Tnc mRNA level was significantly reduced in the skin tissues of aged mice compared with young mice, consistent with reduced TNC protein expression in aged human skin. TNC-large (TNC-L; 330-kDa) and -small (TNC-S; 240-kDa) polypeptides were observed in conditional media from primary dermal fibroblasts. Both recombinant TNC polypeptides, corresponding to TNC-L and TNC-S, increased the expression of type I collagen and reduced the expression of matrix metalloproteinase-1 in fibroblasts. Treatment of fibroblasts with a recombinant TNC polypeptide, corresponding to TNC-L, induced phosphorylation of SMAD2 and SMAD3. TNC increased the level of transforming growth factor-β1 (TGF-β1) mRNA and upregulated the expression of type I collagen by activating the TGF-β signaling pathway. In addition, TNC also promoted the expression of type I collagen in fibroblasts embedded in a three-dimensional collagen matrix. Our findings suggest that TNC contributes to the integrity of ECM in young skin and to prevention of skin aging.