高速粒子撞击作用下LF6合金多层靶结构防护能力研究

针对总厚度为４ｍｍ的ＬＦ６合金双层靶和总厚度为２ｍｍ的三层靶进行了直径为２ｍｍ,速度分别为５．８和７．２ｋｍ／ｓ的ＧＣｒ１５粒子 撞击试验,并对双层靶进行了不同前靶厚度和靶间距的撞击试验,试验结果表明：与同样碰撞条件下半无限体靶上产生的破坏情况相比,多层靶被击穿的总厚度远淖于半无限体靶上形成的弹坑深度,采用多层靶结构可显著提高材料的抗高速粒子撞击能力,并大大降低航天器抗高速粒子撞击的防护结构的重量     

超高速弹丸撞击靶板的脉冲X光照相实验研究

双层靶结构是一种有效的太空防护结构,对速度为5～7km/s的小颗粒弹丸具有极好的防护作用。为研究双层靶结构的防护作用,用二级轻气炮发射超高速弹丸撞击靶板,用脉冲X光摄影系统拍摄弹丸撞击靶板后形成的碎片粒子云团。对照见证靶被侵彻的形态,可以得到内涵十分深刻的实验数据。自动跟踪式脉冲X光摄影系统是一种新型的脉冲X光摄影系统。应用该系统成功地拍摄了高速弹丸撞击靶板后弹、靶形成碎片粒子云团的形态。文章披露了铝弹撞击铝靶,钢弹撞击铅靶后某一时刻的X光拍摄的图象,并对实验结果作了初步分析。     

高聚物夹层材料对层压减振复合钢板拉伸剪切强度的影响

研究了高聚物夹层材料对层压减振复合钢板的拉伸剪切强度的影响。结果指出，高聚物夹层材料较厚时，层压减振复合钢板的拉伸剪切变形规律与高聚物夹层材料的一致；高聚物夹层厚度较小时，复合钢板的拉伸剪切强度较高。与酚醛树脂氯丁橡胶相比，聚氨酯作夹层的层压减振复合钢板具有较高的拉伸剪切强度。     

层压减振复合钢板的拉伸剪切特性

本文选用1.67×10-2、1.67×10-3、1.67×10-4、1.67×10-5s-1四种形变速率,在20～150℃试验温度范围内研究了用酚醛树脂氯丁胶作夹层的层压减振复合钢板的拉伸剪切特性。结果指出,在较低温度和较高形变速率下,层压减振复合钢板具有较高的拉伸剪切强度,其破坏形态呈高聚物撕裂和界面破坏的混合破坏特征;在80℃附近,拉伸剪切强度最低,其破坏形态为具有滑移特征的高聚物内聚破坏;在80～150℃温度范围内,随温度升高,拉伸剪切强度增加,这是由于高聚物夹层材料中的氯丁橡胶发生了交联反应的缘故。     

八十年代节能型涂层工艺的展望(一)

当今世界随着民用建筑业、运输业、电器业及日用工业等部门的急剧发展,对各种涂层钢板的需求与日俱增.据不完全统计,至1981年为止,全世界约有涂层作业线二百余条,总产量六百万吨以上,还有继续猛增的趋势.众所周知,涂层钢板大致可分为有机涂层钢板、无机涂层钢板和复合涂层钢板三种类型,而使用寿命能保证在15年甚至20年以上的合成树脂等涂层钢板是需求量最大的一种,其中有六种产品已大量投入市场销售.这六种产品是: 1.聚氯乙烯薄膜层压钢板; 2.丙烯酸薄膜层压钢板; 3.聚氟树脂涂层钢板; 4.聚氯乙烯复合薄膜层压钢板; 5.聚氟、聚氯乙烯复合薄膜层压钢板; 6.沥青浸渍石棉层压钢板. 目前,国外生产的有机涂层钢板、无机涂层钢板和生产采用的原板.对有机涂层钢板使用的有机材料,现在随着高分子化学的发展,涂层方法的改进,实际上可以提供各种各样的有机材料.     

钨丝/铜合金复合材料高速撞击后的变形分析

为研究钨丝增强铜合金复合材料弹体撞击混凝土靶后的弹体变形,采用渗流铸造的方法将铜合金与钨丝相复合制备出钨丝增强铜合金复合材料,并用二级轻气炮来完成高速撞击试验,试验速度为2 km/s.撞击后对复合材料弹体宏观形貌进行了观察,发现弹体内部钨丝的排布发生了变化,呈现双曲线排布条纹.用数学和力学的方法对撞击后钨丝的排布方式变化进行了分析,发现钨丝排布的变化是由于钨丝束发生绕中心轴的扭转造成的,说明棒状弹体高速撞击混凝土靶时发生了扭转.     

7A04-T6高强铝合金板对平头杆弹抗侵彻行为的试验与数值模拟研究

为了解高强铝合金对动能杆的抗侵彻性能,在一级轻气炮上开展了直径5.98 mm的平头刚性弹侵彻6mm厚7A04-T6铝合金靶板的打靶试验,撞击速度范围为73.9~446.5 m/s。获得了弹体贯穿靶板后的剩余速度以及靶板的断裂行为,通过拟合初始-剩余速度数据得到了弹道极限。同时,在ABAQUS/Explicit中建立了三维有限元模型对打靶试验进行了数值计算,7A04-T6的力学行为通过Johnson-Cook本构模型和修正的Johnson-Cook断裂准则描述。试验结果表明,7A04-T6高强铝合金靶板在平头弹撞击下发生剪切冲塞,塞块表面有明显裂纹产生,弹道极限为156.0 m/s,剪切冲塞可在撞击速度不低于约0.90倍弹道极限时形成。数值仿真发现,有限元计算可成功再现靶板的剪切冲塞及冲塞表面的断裂;预报的弹道极限为168.8 m/s,比试验结果高约9%;撞击速度不低于0.92倍弹道极限时靶板发生剪切冲塞破坏,与试验结果十分接近。     

刚性卵形头弹撞击角度对编织复合材料层合板侵彻特性的影响

利用一级气炮发射卵形头弹撞击2 mm厚度的编织复合材料层合板,撞击角度分别为0°、30°和45°,通过高速相机记录弹靶撞击过程,并获得弹体速度数据。基于拟合公式处理试验数据,计算获取弹道极限,分析撞击角度对弹道极限、靶板能量吸收率及其失效模式的影响规律及机制。结果表明：弹体撞击角度为45°时,靶板弹道极限最高,其次为0°,撞击角度为30°时最小。随着冲击角度增加,层合板损伤形状从菱形逐渐转变为椭球形,损伤面积随冲击速度增加而增大,且45°冲击时层合板损伤面积最大,0°和30°冲击时损伤面积近似相等。弹体初始撞击角度对靶体失效模式存在影响,弹体撞击角度为0°时,纤维断口主要是剪切应力导致的横截面。撞击角度为30°时,纤维断口主要是剪切应力和拉伸应力导致的斜截面。45°斜撞击时,纤维断口主要是拉伸应力导致的横截面。     

超高车辆撞击钢桥上部结构模型试验研究

针对当前城市交通中凸显的车桥碰撞问题,设计了超高罐车撞击钢箱梁桥和钢板梁桥的缩尺模型试验,并采用动力非线性有限元对撞击试验进行了数值模拟。试验结果表明不同桥型在超高车辆的撞击下,其破坏模式有着明显的差别,钢箱梁桥以整体变形为主,钢板梁桥以局部冲切变形为主。文中建立的有限元模型和试验结果吻合良好     

单层A3钢薄靶在不同头型弹体斜撞击下的失效模式和防护性能研究

利用轻气炮设备对平头、卵形弹进行了以5种角度撞击2 mm单层A3钢薄靶的斜穿甲试验,得到了不同头型弹体在各个角度撞击单层靶的初始-剩余速度曲线及靶板的弹道极限,获得并对比分析了弹体头部形状、撞击角度对靶板的防护性能及失效模式的影响。结果发现,平头弹在各个撞击角度下较卵形弹更容易击穿靶板,撞击角度较大时卵形弹较平头弹更容易发生跳飞现象;靶板的防护性能与弹体造成的靶板损伤和失效模式紧密相关,随着斜撞击角度变大,平头弹造成的靶板局部穿孔毁伤模式逐步由剪切冲塞失效转向以拉伸撕裂失效为主,同时整体结构弯曲和膜变形减小,而薄板在卵形弹斜撞击下的失效模式则以局部斜形非对称花瓣开裂为主。     

Determining the Forward Loss Resistance of a UHF Switching Diode

Equivalent parameters of UHF switching diodes can be used to estimate the forward loss resistance. The standard method of measuring that resistance with microwaves involves difficulties and high random errors. Simulation and experimental data show that one is not justified in replacing the UHF loss resistance by the direct-current differential resistance. To estimate the microwave loss resistance, one can use the resistance measured by a pulse method.     

柔性纺织电阻传感器的研究进展

纺织电阻传感器具有质量轻、柔性好和可拉伸等优良特性,在可穿戴电子产品领域具有很大的应用价值。文中根据近年来不同纺织材料基电阻传感器的研究进展,介绍了无捻纤维(束)基电阻传感器、纱线(长丝纱、短纤维纱、复合纱)基电阻传感器和织物(针织物、机织物、非织造织物)基电阻传感器的制备、性能及应用研究。在纱线基电阻传感器中,主要基于导电涂覆纱线受力过程中纤维的内在弹性或长丝之间接触程度的变化所引起电阻改变的原理,制备电阻传感器;对于织物电阻传感器,主要利用织物结构体的变形特征并结合对织物进行导电涂覆或碳化等方法,制备电阻传感器。     

水机材料的抗磨蚀性判据研究

为了证实水机材料的抗磨蚀和抗空蚀性能与材料的常规宏观性能之间的相依关系，选取4种具代表性的材料（碳化钨涂层、NiCr合金涂层、硼不锈钢涂层和钛），进行空蚀和磨蚀试验，并测试了它们的硬度和抗腐蚀性。试验结果表明，材料的空蚀和磨蚀抗力与硬度和抗腐蚀性有着紧密的相依关系:高硬度是抗磨蚀性优的第一判据，较强的抗腐蚀性是第二判据；高抗腐蚀性是抗空蚀性优的第一判据，较高的硬度是第二判据。     

隧道级联大功率半导体激光器热特性分析

基于光谱法,通过测量靠近衬底的有源区波长的变化来表征其温度的变化,计算了隧道级联多有源区大功率半导体激光器的热阻。与普通半导体激光器相比,随着有源区数目的增多该热阻有增大的趋势,但并没有成倍增加,主要原因是隧道级联半导体激光器的串连电阻没有成倍增加。     

Molecular Simulations of Water Transport Resistance in Polyamide RO Membranes: Interfacial and Interior Contributions

Understanding the transport resistance of water molecules in polyamide (PA) reverse osmosis (RO) membranes at the molecular level is of great importance in guiding the design, preparation, and applications of these membranes. In this work, we use molecular simulation to calculate the total transport resistance by dividing it into two contributions: the interior part and the interfacial part. The interior resistance is dependent on the thickness of the PA layer, while the interfacial resistance is not. Simulation based on the 5 nm PA layer reveals that interfacial resistance is the dominating contribution (> 62%) to the total resistance. However, for real-world RO membranes with a 200 nm PA layer, interfacial resistance plays a minor role, with a contribution below 10%. This implies that there is a risk of inaccuracy when using the typical method to estimate the transport resistance of RO membranes, as this method involves simply multiplying the total transport resistance of the simulated value based on a membrane with a 5 nm PA layer. Furthermore, both the interfacial resistance and the interior resistance are dependent on the chemistry of the PA layer. Our simulation reveals that decreasing the number of residual carboxyl groups in the PA layer leads to decreased interior resistance; therefore, the water permeability can be improved at no cost of ion rejection, which is in excellent agreement with the experimental results.     

两种粘结料对泡沫沥青冷再生混合料性能的影响

通过加速加载试验、低温弯曲试验、飞散试验研究了泡沫沥青和水泥两种粘结材料对泡沫沥青冷再生混合料(CRMFA)长期高温抗变形能力、低温抗裂性以及抗松散性能的影响。研究结果表明:对CRMFA的长期高温抗变形能力而言,存在一个最佳泡沫沥青用量;增加水泥掺量有助于提高CRMFA的长期高温抗变形能力。CRMFA的低温柔韧性随泡沫沥青用量的增大而提升,但随水泥掺量增加呈抛物线变化规律,为保证CRMFA具有良好的低温抗裂性能,水泥掺量宜小于2wt%。CRMFA的抗松散性能较差,增加泡沫沥青用量可有效降低其松散性;水泥掺量在1.5wt%~2.5wt%时,对CRMFA抗松散性的改善作用不显著。     

电阻加载偶极天线阻抗带宽及脉冲辐射特性研究

分析了偶极天线电阻加载方面的若干问题，包括不同电阻加载方式阻抗频率特性比较，连续与离散串联集中电阻加载脉冲辐射特性比较，证明其它加载方式具有与Wu-King电阻加载相似的特性，与未加载偶极天线相比，阻抗带宽较宽，辐射脉冲失真较小。     

金属箔饰面家具表面理化性能检测及标准化研究

本文提出了金属箔饰面家具的表面理化性能研究的必要性,并从表面胶合强度、表面漆膜理化性能(耐液性、耐湿热、耐干热、附着力、耐冷热温差、耐磨性、抗冲击)等多个方面提出了检测要求和试验方法,通过验证试验证明了良好的测试效果,并在最后展望了应用前景。     

Modeling of mechanical damage detection in CFRPs via electrical resistance

Carbon fiber reinforced polymer composites (CFRPs) are inherently multifunctional materials that, in addition to their primary function as a structural material, allow for the sensing and monitoring of in situ damage nucleation and evolution by the measurement of the material electrical resistance. Here an analytic model is developed for the transverse (perpendicular to the fibers) electrical resistance of pristine and damaged unidirectional composites, complementing earlier work on the longitudinal resistance. The ratio of transverse to longitudinal resistance for undamaged materials provides a direct measure of the internal density of fiber–fiber electrical contacts, a key material parameter in linking to the response of damaged materials. Under uniaxial loading with evolving fiber breakage, the normalized transverse resistance versus strain is predicted to have exactly the same form as that for the longitudinal resistance. Numerical studies show this agreement for uniform fiber–fiber contact distributions but, for random contact distributions, the longitudinal resistance is larger than predicted while the transverse resistance is smaller; these differences are shown to arise as a result of the statistically-preferential breaking of longer fiber segments. Analysis of multiple numerical simulations shows that variations in the electrical resistance are not directly correlated with variations in the stress–strain response. Thus, statistical methods are required to relate resistance to strain or damage. The Weibull modulus of the resistance change increases with increasing applied strain, with values exceeding 10 and 20 for the transverse and longitudinal resistance, respectively, demonstrating increasing reliability at higher damage levels and good correlation of average resistance change to applied strain. The present study shows that both longitudinal and transverse resistance changes are sensitive to damage in a predictable manner and can be used together to improve the reliability of damage assessment during loading of CFRPs.     

Method of sensing impact damage in carbon fiber polymer-matrix composite by electrical resistance measurement

The method of sensing impact damage in carbon fiber polymer-matrix structural composite by DC electrical resistance measurement was evaluated by measuring the resistance of the top surface (surface receiving impact). The resistance obtained by using the four-probe method is a more sensitive, more precise (less data scatter) and more accurate indicator of composite damage than that obtained by using the two-probe method. The data scatter is low for both four-probe and two-probe resistances for impact energy up to 5 J, but it is lower for the four-probe resistance than the two-probe resistance. The data scatter increases with damage. It is attributed to electrical contact degradation. The four-probe resistance of the 8-lamina composite increases upon impact, such that the fractional increase diminishes as the distance from the point of impact increases. The four-probe resistance of the 24-lamina composite increases upon impact for the specimen segment containing the point of impact, but decreases slightly upon impact for the segments within about 20 mm from the point of impact. The two-probe resistance has less tendency to decrease upon impact than the four-probe resistance.