50 SiMnVB 钢椭圆凹坑疵病原因分析

基于某产品壳体用50SiMnVB钢在冲拔过程中毛坯内膛出现椭圆形凹坑疵病的现象,采用理化检测和工艺试验等手段对该疵病产生的原因机理进行了系统分析与验证,准确地找到了该疵病产生的原因,使生产顺利进行,有效保证了产品质量.     

身管内膛检测系统设计及实现

针对目前火炮内膛检测存在的问题,结合计算机图像拼接技术,设计并实现了一种高精度、高可靠性、智能化的身管内膛疵病检测系统,主要由内膛观测硬件系统和图像拼接分析软件系统组成.观测硬件系统主要是通过CCD摄像头获取内膛疵病图像,由液晶屏实时显示并保存,包括CCD摄像头分系统、计算机分系统和便携式控制箱三大分系统;图像拼接分析软件系统是基于特征点稀少的图像拼接算法对内膛图像进行处理拼接,提供完整的分析图像.系统应用实验结果表明,能获得无缝、清晰、完整火炮身管内膛图像,满足炮管实时检测需要.该系统为实现直观、快速、准确地对火炮的质量、寿命等性能做出判断有较大的实用意义.     

某产品823钢壳体内膛疵病原因分析

目的研究某产品关键零件用壳体823钢在冲拔过程中,毛坯内膛出现侧壁拉裂和底部缩孔疵病的原因。方法通过理论分析毛坯在冲拔过程中的变形机理和金属流动规律,结合理化检测和工艺试验等手段,对该疵病产生的原因进行了系统分析与验证。结果准确找到了该疵病产生的原因。结论 823钢原材料存在缩孔残余及二次缩孔,是造成弹体毛坯底部缩孔疵病和侧壁拉裂疵病的根本原因;通过靶场射击动态考核试验和增加超声波探伤检验工序的产品,即使存在缩孔残余及二次缩孔,也不影响产品使用性能。     

基于激光投影法的火炮身管内膛疵病深度测量

本文介绍了基于激光投影法的火炮身管内膛疵病深度测量的原理，从理论上分析该方法的测量精度，结果表明该方法的精度可达到0．014mm，满足疵病深度定量测量的要求。文章最后对该种方法实现工程上的应用提出了建议。     

某炮弹弹体内膛裂纹原因分析

目的某弹体作为某炮弾一重要零件,材料采用9260钢。研究其在冲压过程中,毛坯内膛出现侧壁拉裂和底部裂纹疵病的原因。方法利用理论分析毛坯在冲压过程中的变形机理和金属流动规律,结合理化检测等手段,对弹体疵病产生的原因进行了系统分析。结果通过对毛坯成形原理分析和理化检测分析,对裂纹产生的原因进行逐一排查,最终准确找到了该弹体疵病产生的原因。结论弹体用9260钢原材料存在缩孔残余及沿晶低熔点物质,是造成弹体毛坯侧壁拉裂和裂纹的根本原因。     

新型压装含铝炸药应用于大口径榴弹发射安全性模拟研究

利用大落锤模拟加载装置,模拟大口径榴弹发射时炸药装药所受的主要应力特性,对新型压装含铝炸药无宏观装药疵病条件进行了膛内应力响应数值计算及模拟实验研究。结果表明,在模拟大口径火炮膛压轴向加载曲线的刺激下,新型高能压装含铝炸药未发生燃烧爆炸反应;在模拟强化加载刺激下,新型压装含铝炸药在2倍最大膛压的模拟加载下是安全的,显示新型高能压装含铝炸药具有较好的安全性能,具备在大中口径弹药中推广应用的基础。     

基于功率-幅值谱的炮膛疵病图像识别

在基于机器视觉的炮膛疵病检测中,针对计算机不能以"目标分割-特征提取-特征分析-判定"的经典思路实现疵病图像识别的难题,采用二次谱分析方法从图像全局性特点中挖掘疵病的信息.定义图像二次谱为"图像功率谱的对数幅值谱",提取其亮线长宽比以及谱图能量均值、能量方差和能量矩4个参量采分析炮膛图像中是否存在疵病.通过实验验证了参量的有效性.     

超声检测信号的特征分析

目的 在无损检测中提高疵病实时检测和识别的正确性和可靠性。方法 提出了利用检测信号的波形特征分析进行疵病实时检测和识别的方法。结果 通过一应用实例,表明该方法对于提高检测可靠性是行之有效的。结论 用波形特征分析的方法可实现疵病的实时检测和提高检测精度。     

美国军用规范MIL-PRF-13830B表面疵病要求详解

以各种不同外形、尺寸、疵病大小的光学零件为例,从表面疵病的标识、量值、换算及判定等各方面对美国军用规范MIL-PRF-13830B进行详细解析,介绍根据美国军用规范MIL-PRF-13830B进行光学零件表面疵病检验与判定的方法。并将该标准与我国国家标准进行对比,重点介绍二者的不同之处。     

高频发射武器内弹道的数值模拟

为研究超高射频武器的内弹道发射过程,建立了弹丸膛内运动数学模型和内弹道基本方程,采用Matlab软件对40mm口径金属风暴武器弹药内弹道进行数值模拟,分析了弹丸超高射频时不同发射频率的膛内运动规律,获得了不同发射频率时弹丸的膛内运动速度和膛压变化规律.研究结果表明:非耦合发射时,各发弹丸的行程不一致导致弹丸最大膛压和出炮口速度不同;耦合发射时,主要是各发弹丸的弹前阻力不同而导致弹丸最大膛压和出炮口速度变化较大.     

Shear strength of highly drawn linear polyethylene sheets

The shear strength of highly drawn linear polyethylene (HDLPE) sheets has been measured using sample shapes suggested by the lap joint technique. Several variables were investigated, including different parent polymers, irradiation dose, draw ratio, drawing methods and geometrical parameters. The lap joint theory has been successfully applied to several qualitative aspects of these experiments.     

拔钎器的设计与使用

用手持式轻型凿岩机在节理裂隙发育的岩石或泥岩中进行钻孔施工时,钎杆通常难以拔出,为此设计了一种手动式拔钎器,可拔出各种出露长度的孔内钎杆,很好的解决了这个问题.     

薄板铝铜搭接搅拌摩擦焊工艺

目的研究铝铜异种材料的搅拌摩擦焊搭接工艺,揭示搭接接头界面行为演变的基本规律。方法对1mm的6061铝合金与1 mm的紫铜薄板进行搅拌摩擦焊搭接焊接,测试焊缝的力学性能,对焊缝组织进行分析。结果焊缝表面成形良好,焊缝内部无缺陷。接头的最高拉伸强度达到1447 N,观察拉伸接头断口形貌,发现断裂均发生在上层铝合金的热影响区。结论接头连接界面区域生成钩状"自锁紧"结构,这种钩状"自锁紧"结构增加了铝铜之间的有效接触面积,有利于提高焊缝连接强度。     

Effect of cold expansion on the fatigue life of Al 2024-T3 in double shear lap joints: Experimental and numerical investigations

In this paper the effect of cold expansion on fatigue life improvement of aluminum alloy 2024-T3 plates used in double shear lap joints is investigated experimentally by conducting fatigue tests and numerically by implementing finite element simulations. In the experimental part, fatigue tests were carried out on the plates with cold expansion levels of 0%, 1.5% and 4.7% which were used in double shear lap joints. In the numerical study, three-dimensional finite element models were employed to predict stress distributions in the cold expanded plates used in the double shear lap joint. The results obtained from finite element simulation, have been employed to explain the trends which were observed in the experimentally attained S–N data and the fatigue crack initiation location. The experimental and numerical results showed that cold expansion improves fatigue life at low load levels and the life enhancement is more for the bigger cold expansion size. However, the fatigue life improvement is smaller in double shear lap joints compared to a single cold expanded plate.     

Effect of tool rotational speed and probe length on lap joint quality of a friction stir welded magnesium alloy

The effects of tool rotational speed and probe length on lap joint quality of friction stir welded 2-mm AZ31B-H24 magnesium alloy were investigated in terms of welding defects, microstructure and mechanical properties. Tensile shear load initially increases with increasing tool rotational speed but decreases with further increase. However, the tensile shear load always increases with increasing probe length. The highest shear strength is obtained using a set of welding parameters resulting in a downward hooking defect at the maximum stress location of the top sheet. Sound lap joints with low distortion, lack of cavity, minor kissing bond and preferable hooking defects, and high tensile shear strength were successfully obtained, indicating the great potential of friction stir welding technique for magnesium alloys.     

一种通用钻孔柱状图的自动生成技术

目前的钻孔柱状图绘图软件大都针对某一专业应用,生成图形后的编辑工作量较大,缺乏通用性。通过对多种专业需求及多种柱状图绘图标准的研究,以国产GIS软件MapGis为平台,采用模板定制与编辑技术、面向对象技术和多层体系结构,实现了一个能够应用于工程地质、水文地质、第四纪地质、石油地质等多种专业的通用单井柱状图的生成、编辑与信息管理系统。生成的柱状图能够满足实际工作的要求。     

Influence of the properties of externally bonded CFRP on the shear behavior of concrete/composite adhesive joints

This paper concerns the strengthening of concrete structures with externally bonded composite reinforcement, and focuses mainly on the influence of the FRP characteristics on the mechanical behavior of the composite to concrete interface. An experimental investigation was conducted, based on the characterization of such bonded assemblies and using a double lap joint shear test. Twelve different series of specimens were studied in order to evaluate the influence of various parameters related to the FRP material (i.e. the use of carbon or aramid and of fiber reinforced systems, the type of manufacturing process, the values of the Young modulus, the thickness of the FRP and the bonded length) as well as several parameters related to the adhesive joint (i.e. the lap joint thickness, the curing conditions and the elastic modulus of the epoxy adhesive). Analyses of the strain and shear stress distributions along the lap joints emphasized significant effects of the FRP properties and epoxy curing conditions on the interfacial strength. In addition, a bond strength model is proposed in the last part of the study.     

Process optimisation and mechanical properties of friction stir lap welds of 7075-T6 stringers on 2024-T3 skin

This paper focuses on the results of process optimisation and mechanical tests that were used to ascertain the feasibility of using friction stir welding (FSW) to join stringers to skin. The effects of process parameters on weld quality of 1.5-mm 7075-T6 stringers lap-joined on 2.3-mm 2024-T3 skins were investigated. Advancing and retreating side locations on the joint configuration were alternated to determine optimal design arrangements. The effects of travel and rotation speeds on weld quality and defect generation were also investigated. Weld quality was assessed by optical microscopy and bending tests. It was found that: (i) the increase of the welding speed or the decrease of the rotational speed resulted in a reduction of the hooking size and top plate thinning but did not eliminated them, (ii) double pass welds by overlapping the advancing sides improved significantly the weld quality by overriding the hooking defect, and (iii) change of the rotational direction for a counter clockwise with a left-threaded probe eliminated the top sheet thinning defect. Subsequently, FSW lap joints were produced using optimum conditions and underwent extensive mechanical testing program. Several assembly configurations including discontinuous and continuous welds as well as single and double pass welds were produced. The results obtained for cyclic fatigue performance of FSW panels are compared with riveted lap joints of identical geometry. S–N curves, bending behaviour, failure locations and defect characterisation are also discussed. It was found that: (i) the tensile strength of FSW joints approached that of the base material but with a significant reduction in the fatigue life, (ii) the probe plunge and removal locations served as the key crack nucleation sites in specimens with discontinuous welds, and (iii) double pass welds with overlapping advancing sides showed outstanding fatigue life and very good tensile properties. The present work provided some valuable insight into both the fabrication and application of FSW on stringer/skin lap joints.     

Experimental and numerical investigations into the effect of an interference fit on the fatigue life of double shear lap joints

In this research the effect of bolt interference fit on the fatigue life of lap joints in double shear was investigated by conducting experimental fatigue tests and also analytically by FE simulation. In the experimental part, fatigue tests were carried out on specimens made from aluminium alloy 2024-T3 plates joined together as double lap joints and secured using bolts having fits ranging from zero clearance to different levels of interference. The results demonstrate how the failure is affected using different levels of interference fit. In the numerical study, 3-D FE models were used to simulate the different pin in hole fits considered and the results have been used to help explain the trends which were observed in the experimentally obtained S–N curve behaviour.     

铺层顺序对预成型体搭接复合材料拉伸性能影响的仿真与验证

使用有限元理论模拟分析了几种不同铺层顺序的预成型体搭接复合材料的拉伸性能,并且使用国产碳纤维与快速固化环氧树脂制备相应的单下陷搭接试样,测试其搭接接头的拉伸性能,对有限元计算结果进行了验证。结果表明,使用有限元计算与实验方法得到的结果基本相符。有限元模拟及实验验证发现不同铺层结构的预成型体搭接复合材料有两种不同的破坏损伤模式。搭接上层板的层间剥离强度与层板本身弯曲性能共同决定了搭接接头的破坏模式及拉伸性能,两者中强度较弱的先发生破坏,导致试样失效。在预成型体搭接接头中,0°铺层越靠近搭接面,对搭接性能的影响越明显,搭接强度越高。搭接界面处纤维层之间的相对角度不同,纤维铺层刚度不同,刚度差别越大,搭接强度就越低。