水雷不同外形目标强度的计算与测量

根据水雷隐身需要，分析了不同外形水雷的目标强度与隐身之间的关系，并对一些典型外形进行了目标强度计算．同时．在非消声水池中对按比例缩小的外形样品进行了声脉冲测量，将试验测得的目标强度值与理论计算的目标强度值相比较，认为波纹盒形水雷有较好的外形隐身效果．     

船坞登陆舰声散射时频特征数值及试验研究

阐述了基于虚源法的板块元基本原理,以及目标强度和时域回波的计算方法。通过建立三维船坞登陆舰的网格模型,考虑水面反射以及船艉部分浸水的影响,计算得到了水平方位上的目标强度、由远场到近场回声强度的变化规律以及浅海水域下通过水雷正上方时回声强度的通过特性,并对这些结果进行的分析。通过开展运动水面舰船模型声散射湖上试验,获取了舰船模型时域回波特征,并与计算结果对比。研究结果表明,采用基于虚源法的板块元能够对船坞登陆舰的目标强度、回声强度以及时域回波结构给出比较准确的预报。研究结果将对提高船坞登陆舰声隐身特性,避开鱼雷和水雷等水中兵器的攻击提供一定的参考价值。     

马迹山港堆场区域岩—土界面的抗震稳定性

本文根据宝钢马迹山港矿石堆场地质特点。采用有限元法和直接积分法对地震荷载作用下堆场区域岩－土界面及附近地层动力响应进行时域计算分析,得出地层运动量和应力时程曲线。结合库仑强度理论推算出,只要界面附近不出现软弱夹层,岩－土界面有足够的抗剪切滑移安全度。     

水雷总体的声学问题

提出了水雷隐身的总体声学问题概念。通过对水雷声隐身的两种手段：壳体上涂涂层和改变外形进行比较，发现隐身的关键在于外形设计。讨论了改变水雷外形以降低其目标强度（TS）途径，分析了几种不同水雷外形对声纳探测距离的影响，认为改变水雷外形是降低声探测距离的有效手段。     

双相介质界面附近裂纹的断裂力学特征

复合材料界面附近的力学性态对于材料的性能和强韧化影响是非常重要的。首先研究和讨论了含裂纹的双相介质的J 积分守恒定律的适用性问题, 采用有限元法证明了当裂纹平行靠近界面时, 其J 积分数值与裂纹位置无关的假设。文中建立了一种双相介质界面附近存在斜裂纹的分析模型, 用有限元和数值拟合相结合的方法, 得到了在远场单轴拉应力作用下, 斜裂纹处在不同介质中, 近界面一端裂尖的é 型能量释放率近似计算公式, 和相应的应力强度因子的计算方法。     

智能化水雷引信及其评估方法

讨论了智能化水雷引信的内涵，建立了考核水雷引信智能化水平的指标体系及模糊评估框架和模型．水雷引信智能化水平评估的计算实例表明，该方法和模型是完备可行的。     

力、热载荷作用下纤维在复合材料中的界面应力传递行为

采用三维光弹性实验应力分析和有限元计算两种方法,在拉拔载荷和热残余应力联合作用下,对单丝拔出树脂基复合材料三维冻结切片界面剪应力进行了研究。实验结果和计算表明,在单纤维与基体界面的埋入端及埋入末端附近出现界面残余剪应力的极值;力、热载荷作用下纤维界面剪应力呈抛物线分布,单丝埋入端附近是应力的主要传递区域,最先达到危险应力,出现界面脱胶破坏,然后剪应力沿纤维埋入长度由纤维埋入端附近向埋入末端逐渐传递;界面热残余应力对界面剪应力的影响是使纤维埋入末端应力集中程度降低,使界面剪应力最大值增大。      

大面积Inconel625薄壁双面肋加强板爆炸焊接研究

中国新型核聚变实验堆HL-2M的真空室需要一种内含密闭流体通道的inconel625薄壁双面肋加强板,其难以采用常规加工工艺制备。本文在爆炸焊接装药参数计算与优化、复合支承模板设计、模板设置与脱模技术、双面分步爆炸焊接和应力退火工艺等方面开展试验研究,成功制备了该双面肋加强板,并对其进行了显微金相、电镜扫描、显微硬度检验和力学试验。检验结果表明：结合界面附近金属组织晶体细密,实现了冶金结合;界面的剪切强度超过母材的强度;界面附近组织的显微硬度明显提升。     

水下目标特征提取方法研究

有效的特征提取技术是水雷目标识别的基础。文章采用了两种前期研究中较为有效的水雷目标特征提取方法(频域离散小波变换法和常数Q滤波子带能量法),并引入了一种应用在水下目标识别领域中的特征提取方法(波形结构法)。应用此三种特征提取方法提取的特征来识别实雷目标以及假目标,分类器采用三层BP算法的前向神经网络,给出了具体的识别率,说明该特征提取算法是有效的,用波形结构法进行水雷目标的特征提取是可行的。     

浅海沉积层中界面波的传播以及掩埋目标的回波

根据地声界面波的相关理论,采用时域有限差分法建立浅海沉积层中界面波传播模型。以沉积层中掩埋小目标为例,计算界面波对空腔掩埋物和实心掩埋物的不同作用结果。根据运动方程和应力应变关系采用中心差分网格建立声场的有限差分模型,计算了声场瞬态情况和质点振动的时间序列结果,从不同角度比较分析了地声界面波对掩埋目标的作用。根据浅海沉积层的性质计算了界面波的传播损失和对掩埋物体的目标强度,由于界面波传播衰减主要由沉积层的能量耗散引起,其规律接近横波的传播衰减,在高频情况下界面波在沉积层中传播的距离不远。文章试图建立一种对浅海沉积层中掩埋小尺度目标的探测新方法。通过一些典型模型的分析,从理论角度证明地声界面波对目标探测的可行性。     

消声瓦声参数匹配与水下目标的回波消声效果

覆盖消声瓦是水下目标隐身的一个主要方法,对敷瓦消声效果的预报是敷瓦工程的一个重要环节。预报的关键是对消声瓦吸声效果的数值分析和目标回波强度的计算方法。本文分析了消声瓦的吸声机理,据此,采用传递矩阵法和参数匹配方法求得敷瓦多层结构在任意方向的反射系数,再通过物理声学方法计算目标回波强度,给出预报值,并同实验结果进行了比较。     

Ti(C,N)/Ni扩散焊接界面的组织和性能

以铜和铌作为中间夹层,真空扩散焊接Ti(C,N)/Ni,研究温度和时间等主要工艺参数对Ti(C,N)/Ni界面微观组织和性能的影响.结果表明,当扩散焊接的温度低于1273 K时,界面的夹层材料基本保持不变,界面的微观组织为Cu/Nb层状物,铜在镍中有少量扩散;而当扩散焊接的温度为1523K时,界面微观组织在初期为Ni8Nb的金属问化合物 离散析出的CuNi固溶体,到后期变为靠近Ti(C,N)侧为(Ti,Nb)(C,N) NbT(Ni,Ti,Cu)6 NbNia层,靠近Ni侧为NiCu NbNis层.这表明,液态Cu为过渡液相,通过Ni的溶解而形成CuNi过渡液相,加速了Nb在CuNi过渡液相中的溶解.由此产生的NiNbCu过渡液相能浸润Ti(C,N),并在界面处形成少量的(Ti,Nb)(C,N)固溶体合金,从而提高了界面的结合性能,界面剪切强度可达到140 MPa.     

基于板块元的水面舰船远场声目标强度预报方法

提出了一种基于板块元的水面舰船水下远场声目标强度数值预报方法,首先根据水面舰船水下船体及附体的型线进行等效建模,采用板块元方法进行网格划分,建立了水面舰船特有的复杂附体二次反射、海面散射效应的数值模型,将各板块元的声散射视为一种"滤波",各板块元的散射声传输函数具有不同幅度、相位、时延,将其叠加之和进行反傅氏变换后,获得水面舰船波形级的远场声目标强度及方位分布特征。通过分析比较典型声呐探测信号下水面舰船的声目标强度,验证了该方法的有效性,为优化与控制水面舰船目标强度,分析水面舰艇水声对抗的作战效能提供了物理依据。     

Comparison of cohesive zone model and linear elastic fracture mechanics for a mode I crack near a compliant/stiff interface

Cohesive zone model has been widely applied to simulate crack growth along interfaces, but its application to crack growth perpendicularly across the interface is rare. In this paper, the cohesive zone model is applied to a crack perpendicularly approaching a compliant/stiff interface in a layered material model. One aim is to understand the differences between the cohesive zone model and linear elastic fracture mechanics in simulating mode I crack growth near a compliant/stiff interface. Another aim is to understand the effects of elastic modulus mismatch and cohesive strength of the stiff layer on the crack behavior near the interface. To simulate crack growth approaching an interface, the cohesive zone model which incorporates both the energy criterion and the strength criterion is an effective method.     

Effect of continuous cooling heat treatment on interface characteristics of S45C/copper compound casting

The bonding of an S45C steel insert to copper during cast welding and continuous cooling treatment (including: furnace cooling; air cooling; oil quenching and water quenching) was investigated. The interface shear strength was determined using a push-out test. A cast welding layer formed between S45C steel and copper. After continuous cooling heat treatment, a cast welding layer was present near the S45C steel, an irregular layer near the copper matrix, and a middle layer between these two. X-ray diffraction analysis was used to determine that the interface layer consisted of carbon and CuFeO₂.Electron probe microanalysis (EPMA) demonstrated that most iron atoms and carbons diffused into the copper matrix. The interface shear strength of the compound casting under furnace-cooling was the largest and that of the compound casting formed by water-quenching was the smallest, and all fractures in the cast welding layer occurred near the S45C steel matrix.     

Interface strength of structured nanocolumns grown by glancing angle deposition

In order to investigate the mechanics of interfacial fracture in structured nano-elements grown by glancing angle deposition (GLAD), fracture experiments were conducted on oblique Ti nanocolumns grown on a Si substrate using a micro-brick specimen. Two types of specimens, a Forward specimen (loading with the column tilt direction) and a Reverse specimen (loading against the column tilt), were prepared to clarify the effect of an asymmetric nanostructure on the interface strength. The specimens fractured at the interface or near the interface between the Ti nanocolumns and the Si substrate for both specimens. The critical force and displacement at fracture in the Forward specimens were about 2.0 times and 1.6 times as large as those in the Reverse specimens, respectively, showing clear anisotropy in the interface strength. The local stress distribution along the interface in the single nanocolumn at fracture was analyzed by finite element analysis. While the stress singularity in the Reverse specimen was greater than that in the Forward specimen, the normal stresses in a region 1–3 nm near the interface edge were almost identical regardless of the loading direction, suggesting that intensified stress in the nanoscale region dominated fracture.     

Impact and compression after impact experimental study of a composite laminate with a cork thermal shield

The aim of this paper is to present an experimental study of impact and compression after impact (CAI) tests performed on composite laminate covered with a cork thermal shield (TS) intended for launchers fairing. Drop weight impact tests have been performed on composite laminate sheets with and without TS in order to study its effect on the impact damage. The results show the TS is a good mechanical protection towards impact as well as a good impact revealing material. Nevertheless, totally different damage morphology is obtained during the impact test with or without TS, and in particular at high impact energy, the delaminated area is larger with TS. Afterwards, CAI tests have been performed in order to evaluate the TS effect on the residual strength. The TS appears to increase the residual strength for a same impact energy, but at the same time, it presents a decrease in residual strength before observing delamination. In fact, during the impact tests with TS, invisible fibres’ breakages appear before delamination damage contrary to the impacts on the unshielded sheets.     

Weld overlay cladding of high strength low alloy steel with austenitic stainless steel – Structure and properties

The present work aims at studying structure–property correlations in a weld overlay clad high strength low alloy steel with austenitic stainless steel of American Institute for Steel and Iron (AISI) 347 grade. Optical microscopy studies revealed that the interface between the two steels was nearly flat. The base plate had ferrite plus bainite microstructure adjacent to the interface and tempered bainite/martensite structure away from the interface. Grain coarsening and decarburization were observed near the interface. The stainless steel exhibited austenite dendritic structure. Tensile strength, notch-tensile strength and charpy impact energy of the base plate were found to be higher than those for the interface. The microhardness was observed to be maximum on the clad layer near interface. The shear bond strength of the weld overlay-interface was higher than the shear strength of the base plate. Fractography was carried out using scanning electron microscope on tensile, notch-tensile and shear bond test specimens of the interface as well as shear test specimens of the base plate. It revealed the presence of predominantly dimpled rupture. Charpy impact specimens of the interface failed in mixed mode while impact specimens of the base plate failed in ductile mode. Electron probe microanalysis across the bond interface indicated linear change in concentrations of Cr, Ni, Mn, Cu, Mo, Nb and Si between the levels appropriate to the clad layer and base metal.     

红外弱小目标检测跟踪并行处理系统

针对红外弱小目标的实时检测与跟踪,本文设计了一套基于4×ADSP TS201S-600处理器的多DSP并行处理系统.该系统拥有LVDS数字视频输入输出接口,利用TS201S的链路口构建了松耦合并行处理系统,支持多DSP间的两两交叉互联和板级互联,定点运算的峰值速度可达19.2 GMAC@16 bit/s,浮点运算的峰值速度可达14.4 GFLOPS.实验结果表明,该并行处理系统具有高实时性、良好的适用性和扩展性等特点,可以实现对大画面,高帧频的红外弱小目标实时检测跟踪.     

Influence of bimaterial interface on kinking behaviour of a crack growth emanating from notch

The mechanism of crack deviation by an interface modifies considerably the behaviour of bimaterials fracture. Their fracture resistance is highly affected by the difference of the elastic properties of the bonded materials. In this work, the finite element method is applied to analyze the behaviour of a crack emanating from semicircular notch root growing in interface ceramic/metal composites and perpendicularly to this interface. The obtained results showed that the crack grew to interface from harder material, its energy decreased at the approach of the interface, in this case was retarded; an inverse phenomenon occurs if the crack is propagated towards a lower strength material and its energy increases, it has tendency to accelerate. The effects of geometry on the crack deflection near the interface are also discussed.