TC4钛合金消音蜂窝结构钎焊工艺

采用Ti基钎料真空钎焊方法进行了TC4钛合金消音蜂窝钎焊试验,对不同钎料添加厚度钎焊后消音蜂窝堵孔、钎焊界面焊合率、钎焊界面组织和力学性能进行了对比分析,确定了TC4钛合金消音蜂窝钎料添加厚度和钎焊工艺参数.结果表明,随着钎料添加厚度的增加,消音蜂窝带孔面板堵孔率增加,同时钎料元素对钎焊界面原始组织溶解加剧,蜂窝的拉伸力学性能下降明显.增加钎料添加厚度能够显著提高钎焊界面焊合率,当钎料添加厚度增加至30 μm以上时,能够获得焊合率良好的消音蜂窝结构.钎料添加厚度为30 μm,钎焊温度920℃,保温时间90 min时,钎焊后的钛合金消音蜂窝力学性能良好,且消音蜂窝声学性能试验测试结果和理论模型计算结果一致.     

钢质蜂窝夹芯减振板的实验研究

采用多目标优化方法设计了3种不同规格减振板的面板、芯材以及蜂窝芯尺寸。面板和芯材之间采用自制助复剂,利用瞬间液相扩散焊原理实现复合,并进行了力学性能和减振性能试验,试验结果表明,设计的蜂窝板满足力学性能要求,并提高了减振性能。     

不锈钢-3003铝合金蜂窝夹芯板轧制复合工艺

研究了采用轧制复合方法生产不锈钢-3003铝合金蜂窝夹芯板的工艺.结果表明:经过表面清理的面板和芯板,在加热至500～550℃后进行轧制复合,在变形率为25%以上时即可以实现牢固的初结合,面板与芯板间的结合主要依靠"裂口机制";轧制过程中芯板上的圆孔出现了类似于墩粗的情况,为使芯板上孔系能够发挥作用,轧制变形率应当控制在25%～40%之间;经过退火热处理后,夹芯板的抗拉强度、弯曲强度和延伸率等力学性能均达到相关产品标准.     

泡沫铝芯体夹层板压缩力学性能的试验研究

本文对泡沫铝芯体夹层板材的准静态和动态力学性能进行了试验研究.在SHPB设备上测试了不同冲击速度时的动态压缩响应,为了对比,也测试了静态压缩力学性能.结果表明泡沫铝芯体夹层板准静态和动态压缩过程均具有明显的三阶段特征.即弹性区、屈服平台区和致密区.随着应变率的增加,泡沫铝芯体夹层板的动态屈服强度增加,具有明显的应变率效应.     

SP700/TC4钛合金蜂窝夹层结构钎焊工艺分析

采用非晶态Ti-Zr-Cu-Ni箔带钎料对SP700/TC4钛合金蜂窝结构进行钎焊工艺研究,分析了钎焊温度和保温时间对钎焊接头组织和力学性能的影响. 结果表明,当钎焊温度在875～890 ℃之间变化时,随温度升高,钎焊接头中元素扩散更为充分,接头拉脱强度持续增长;在890 ℃下保温2～4 h不同时长进行钎焊,接头的拉脱强度先逐渐增加,在保温时间为3.5 h时达到最大值,随后逐渐降低. 获得SP700/TC4钛合金蜂窝结构的较优钎焊工艺为890 ℃/3.5 h,该工艺下钎焊接头的室温拉脱强度、三点弯曲强度、平面压缩强度、L及W方向抗剪强度分别达到14.64,224.05,11.21,4.43及3.76 MPa,破坏部位均为TC4蜂窝芯.     

三明治结构中T形焊接接头力学性能测试分析

提出双剪切试验模型和T形接头的弯矩试验模型,用于测定焊缝及接头在不同工作应力状态下的不均匀变形和失效过程,并利用有限元计算对接头中焊缝变形及应力状态进行分析.结果表明,金属三明治板在承受弯矩载荷时面板和芯板连接处的焊接接头主要承受平行于面板的剪应力和弯矩作用;随着加载,损伤起始于焊缝焊根处,并向纵深扩展.针对接头失效分析,试验与数值计算得到了较统一的结果.     

Impact damage behavior of sandwich composite with aluminum foam core

Impact property of the sandwich composite with aluminum foam core was investigated by experiment and simulation analysis. Impact energies of 50, 70 and 100 J were applied to the specimens in impact tests. The results show that the striker penetrates the upper face sheet, causing the core to be damaged at 50 J test but the lower face sheet remains intact with no damage. At 70 J test, the striker penetrates the upper face sheet and the core, and causes the lower face sheet to be damaged. Finally at 100 J test, the striker penetrates both the upper face sheet and the core, and even the lower face sheet. The experimental and simulation results agree with each other. By the confirmation with the experimental results, all these simulation results can be applied on structure study of real sandwich composite with aluminum foam core effectively.     

Evaluation of the in-service performance behavior of honeycomb composite sandwich structures

When honeycomb composite structures are fabricated for the aerospace industry, they are designed to be closed to their operating environment for the life of the composite structure. However, once in service, this design can break down. Damage can set in motion a chain reaction of events that will ultimately degrade the mechanical integrity of the composite structure. Through thermographic analysis, the tendency of honeycomb composite structures to absorb and retain water was investigated, and an attempt was made to quantify the extent of water ingression in the Boeing 767 aircraft. Through thermographic analysis, the exterior honeycomb composite structures were found to contain less than 50 kg of water per plane. On average, over 90% of the water found on an aircraft was contained in five problematic parts, which included the outboard flap wedge, the nose landing gear doors, the main landing gear doors, the fixed upper wing panels, and the escape slide door. Kevlar lamina induced microcracking, skin porosity problems, and cracked potting compound were the root causes of water ingression and migration in these structures. Ultimately, this research will aid in the fundamental understanding and design of future honeycomb composite sandwich structures.     

TC4钛合金/304不锈钢异种材料蜂窝结构钎焊工艺

采用Ti-37.5Zr-15Cu-10Ni和Ag-28Cu两种钎料分别对TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝结构进行了钎焊,对钎焊界面组织和蜂窝结构的力学性能进行了对比分析. 结果表明,Ti基钎料与304不锈钢蜂窝芯箔材界面润湿反应性能较差且Ti基钎料钎缝显微硬度较高,导致钎焊界面强度低,蜂窝拉伸力学性能差. Ag基钎料与304不锈钢蜂窝芯箔材和TC4面板均发生显著的界面反应,钎焊温度830 ℃,保温时间10 min时,蜂窝抗拉强度为10.35 MPa,呈蜂窝芯破坏特征. Ag基钎料蜂窝抗拉强度明显优于Ti基钎料结果,适用于TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝钎焊.     

金属夹芯复合板及其制备技术的发展

简要介绍了各种金属夹芯复合板的结构形式、特点及其应用领域。阐述了金属夹芯复合板按照芯材的分类以及不同种类芯材的制备方法．结合芯材的制备技术重点介绍了蜂窝芯材的制备。在金属板面与芯材的各种连接技术中介绍了胶接、钎焊连接、缝焊、激光焊以及界面瞬间液相扩散轧制等连接方法。     

Aluminum alloy foam core sandwich panels fabricated from die casting aluminum alloy by friction stir welding route

An aluminum foam sandwiches (AFSs) consisting of ADC12 Al–Si–Cu die casting aluminum alloy foam and ADC6 Al–Mg die casting aluminum alloy face plates were fabricated. Using ADC12 die casting plates containing large amounts of gases as the starting material of the foam, ADC12 foam can be fabricated without using a blowing agent. Using FSW, both the uniform dispersion of the segregated gases and pore stabilization powder in the ADC12 die casting plates used to fabricate a foamable ADC12 precursor and the bonding of the ADC12 precursor to the ADC6 plates can be simultaneously achieved. Namely, the AFS precursor is expected to be obtained in fewer processing steps. From the visual observation of the fabricated AFSs, no deformation of the ADC6 plates occurred and the ADC6 plates on both sides of the aluminum foam remained parallel. From the X-ray CT observation of the fabricated AFSs, good pore structures without the infiltration of ADC12 foam into the ADC6 plates can be obtained at a holding temperature of 948 K and holding times of t = 10 and 11 min. In tensile tests on the fabricated AFSs, fracture occurred in the ADC12 foam parts but no fractures were observed at the bonding interface between the ADC12 foam and the ADC6 plates, that is, good bonding was obtained between the ADC12 foam and the ADC6 plates.     

Near-field microwave identification and quantitative evaluation of liquid ingress in honeycomb sandwich structures

Honeycomb sandwich structures are susceptible to liquid ingress, which causes a serious degradation of performance. Herein, a near-field microwave nondestructive detection technique was proposed to detect, identify, and quantitatively evaluate liquid ingress in honeycomb sandwich structures. Based on the microwave reflection spectrums, liquids of different polarity properties were identified. The amplitude of reflection microwaves was found nearly linear with respect to the height of the intruding liquids in the near field of the coaxial adapter probe. A simple characteristic peak method (CPM) based on line scans was presented and applied to quantify the size of liquid ingress region, and it turned out to be quite accurate with relative errors less than 0.5%. In summary, the near-field microwave testing technique proposed in this study is effective to detect, identify, and quantify liquid ingress in honeycomb sandwich structures.     

泡沫铝填充金属波纹板耦合增强机理研究

将闭孔泡沫铝填充到空心金属波纹板孔隙当中即可获得泡沫铝填充波纹板结构,对其准静态压缩吸能特性进行实验表征。研究表明,泡沫铝填充波纹板其压缩应力远高于泡沫铝与空心波纹板二者单独压缩应力之和,表现出明显的耦合增强效应,其单位质量峰值抗压缩强度及单位质量能量吸收率(SEA)可分别高达对应空心结构的6.3及14.8倍,即使和泡沫铝相比,其SEA仍可提高50%以上。进一步通过对空心波纹芯体结构的屈曲变形模式研究表明,泡沫铝的填充给予了波纹芯体单元足够强的横向支撑,使其变形模式转变为空心结构难以产生的更加高阶的屈曲变形模式,屈曲波长变短,产生耦合增强效应。     

金属泡沫夹芯梁的压入力学行为(英文)

研究集中载荷作用下金属泡沫夹芯梁的准静态压入力学行为。考虑到夹芯梁表板弯曲和拉伸的相互作用,提出了一个金属泡沫夹芯梁局部压入大挠度变形行为的新理论模型,并详细讨论芯材剪切对局部压入行为的影响。为了验证理论模型的有效性,对夹芯梁的局部压入行为进行有限元数值模拟,理论预测结果与有限元模拟结果吻合得很好。结果表明:当压入挠度超过夹芯梁表板厚度后,塑性膜力控制着夹芯梁的局部压入行为。     

TC4钛合金蜂窝板钎焊接头组织性能分析

研究了TC4钛合金蜂窝板的钎焊工艺,试验采用Ti-Zr-Ni-Cu钎料,真空度不低于2×10-3 Pa,钎焊温度为930℃,保温时间为30 min.对焊后试件的钎焊界面组织进行超声无损检测,检测结果表明面板与蜂窝芯钎焊效果极好,未发现有脱焊、虚焊等现象.采用扫描电镜（SEM）和能谱分析（EDS）法进行了试验分析.结果表明,母材和钎料发生相互扩散渗透反应,并出现有新的析出相.该工艺下蜂窝板的界面平均拉脱强度为12.8 MPa,抗剪强度为9.01 MPa,钎焊接头属于脆性断裂.     

钢面板泡沫铝夹心板的三点弯曲行为

采用胶粘法制备大尺寸钢质泡沫铝夹心板,测试夹心板的三点弯曲强度,分析面板厚度、芯层厚度对夹心板弯曲性能的影响规律,研究弯曲载荷作用下的夹心板失效机理。结果表明：钢质泡沫铝夹心板可承受很高的弯曲载荷,夹心板抗弯强度随着芯层泡沫铝厚度的提高而提高。增加钢面板的厚度,夹心板抗弯强度整体呈增强趋势。当面板厚度为8 mm、芯层厚度为50 mm时,夹心板的极限抗弯强度可达66.06 kN。芯层泡沫铝内泡壁表面的大尺寸裂纹是夹心板在弯曲载荷作用下失效的主要原因;采用熔体发泡法制备的泡沫铝板材,因冷却强度过大而导致的附加应力使泡壁的强度下降,也是影响夹心板力学性能的主要因素。     

基于数字散斑相关法的蜂窝板拉伸力学性能测试

作为金属热防护系统的重要组成部分,金属蜂窝夹芯板的性能和结构可靠性关系到使用寿命。本研究采用数字散斑相关技术和时间序列散斑检测技术,对蜂窝夹芯板共面拉伸性能进行试验研究,测得共面拉伸弹性模量,与利用等刚度法计算得到的蜂窝夹芯板的等效弹性模量进行对比,结果吻合较好,验证了数字散斑相关技术的有效性和实用性。     

复合蛋盒型夹层结构动态压缩的力学性能研究

蛋盒型结构是一种新型的周期性单胞轻质结构,该结构具有低密度、高比强度和吸能能力强等特性.本研究通过有限元法建立了平面蛋盒型夹芯板与曲面蛋盒型夹心板的落锤冲击模型,对比分析了其抗冲击特性,并且对不同条件下蛋盒型结构的动态压缩力学性能进行对比分析.结果 表明:受到冲击时的夹芯板会经历3个阶段,其中压缩阶段为主要的吸能阶段,...     

钎焊方法制备泡沫铝/铝夹芯板的组织及性能

采用Al-Si钎料真空钎焊的方法制备了泡沫铝/铝夹芯板,对夹芯板钎焊界面处微观组织进行了金相、SEM形貌、EDS能谱分析,并对夹芯板弯曲力学性能进行了研究,分析了钎焊工艺参数对泡沫铝/铝焊缝微观组织及力学性能的影响.结果表明,在605~625℃温度下保温20 min,夹芯板钎缝中心区微观组织主要由α（Al）固溶体、块状CaAl₂Si₂化合物、骨骼状CaAl₄组成;随着焊接温度的升高,钎料中合金元素向母材中扩散速度加快,块状CaAl₂Si₂分布更加均匀、分散,提高了焊缝中心区的韧性;当焊接温度为625℃时,泡沫铝/铝夹芯板抗弯强度达到最高的67.97 MPa.     

Mechanical properties of aluminum/polypropylene/aluminum sandwich sheets

The aluminum/polypropylene/aluminum (A1/PP/A1) sandwich sheets have been developed for potential application of these materials for automotive body panels in future high performance automobiles with significant weight reduction. The tensile properties of the A1/PP/A1 sandwich sheets were examined in the present study as well as those of the aluminum skin and the polypropylene core at room and elevated temperatures. It was found that the sandwich sheet with hard skin and low volume fraction of the polypropylene core showed the highest tensile strength, whereas that with soft skin and high volume fraction of the polypropylene core showed the lowest strength. The sandwich sheet with hard skin showed much smaller work hardening rate than that with soft skin. All sandwich sheets showed serration phenomena on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of polypropylene core. The tensile strength of the sandwich sheet was compared with that calculated from the rule of mixture based on the tensile strengths of the aluminum skin and the polypropylene core. The results showed that there were good agreements between the experimentally obtained values and the calculated values. From the tensile tests at elevated temperatures, it was found that the tensile strength of the sandwich sheet with high volume fraction of polypropylene core was more sensitive to temperature than that with low volume fraction of polypropylene core. During tensile deformation of the sandwich sheet, it was found that fracture first took place in the aluminum skin and then in the polypropylene core and at the interface. The interface strength was found to be strong enough to avoid premature debonding at the interface before fracture took place in the entire sandwich sheet.