爆炸压实工艺参数对钢管能量与变形的影响

为了指导研究爆炸压实工艺参数的选择,通过改变爆轰速度与装药厚度来改变爆炸冲击能,重点研究爆炸压实工艺参数对钢管能量与变形的影响.研究表明:当其他工艺因素相同、仅爆轰速度不同时,将导致爆轰压力、钢管壁速度、爆炸冲击能、粉末压实能等显著不同,但钢管的变形与能量却几乎不变;当采用爆轰速度极高的黑索今炸药时,由于爆轰压力与爆炸冲击能过高,导致钢管头部被切掉;对硝酸脲炸药而言,随着装药厚度与炸药/钢管质量比增加,钢管的能量与变形、爆炸冲击能与粉末压实能单调增加.     

后续烧结对爆炸压实CuCr合金性能的影响

采用机械合金化工艺由Cu,Cr元素粉按重量比各半合成CuCr预合金粉,尔后爆炸压实工艺制坯,再加后续烧结制备了电触点材料CuCr合金,着重研究了后续烧结对爆炸实CuCr合金性能的影响,结果表明,真空烧结略微提高爆炸压实的CuCr合金的密度,而氢气烧结处理反而使其密度降低,真空烧结和氢气烧结都能显著降低CuCr合金硬度,而且氢气烧结降低得更明显,真空烧结和氢气烧结都显著提高CuCr合金的电导率,而且真空烧结提高更显著。     

后续烧结对爆炸压实CuCr合金显微组织的影响

对爆炸压实CuCr合金坯采用两种低温烧结处理工艺,通过观察其显微组织变化研究了后续烧结对爆炸压实CuCr合金显微组织的影响.结果表明,氢气烧结处理后的CuCr组织呈现出液相烧结的特征,而真空烧结处理后表现为固相烧结的特征,经烧结处理后的组织比爆炸坯的组织细小.Cu、Cr合金坯经低温烧结处理后,仍由Cu相、Cr相以及少量氧化物组成.另外,微区内出现轻微的成分偏析,烧结体含有大量的应变条纹和位错.     

爆炸压实中爆轰压力与粉末致密度的关系

在粉末材料爆炸压实试验中,爆轰压力是一个重要的工艺参数.本文结合质量不变条件、粉末材料泊松比与相对密度之间的关系、粉末材料的屈服准则以及粉末材料塑性变形时应力应变关系,研究爆炸压实工艺中爆轰压力与粉末致密度之间的关系,以便为实际的爆炸压实试验选择爆轰压力时提供理论依据.结果表明,随着爆轰压力增加,粉末爆炸压实坯的致密度也增加;当采用与其屈服强度相等的爆轰压力时,只能获得80.4%理论密度的棒坯;只有采用16倍屈服应力的爆轰压力时,爆炸压实才有可能获得99%理论密度的棒坯;无论爆轰压力多么大,爆炸压实法也不能得到完全致密的棒坯.     

ITO纳米粉末爆炸压实烧结致密化陶瓷靶材研究

对ITO商业复合粉末应用爆炸冲击方法压实烧结,并对样品进行了XRD和ESM检测.通过粉末和压实后样品的XRD图及SEM照片的比较,发现在爆炸冲击压实纳米ITO陶瓷粉末时,能够使晶粒度减小,有助于后续烧结密实过程中控制ITO靶材的晶粒度的过分长大;SEM图片显示,在1200℃烧结的靶材微观结构比较均匀.本文探索了纳米ITO粉末冲击压实烧结的微观机理,并与以往人们对粉末的冲击沉能结论进行了比较,得出结论:压实烧结的主要机理是破碎填充效应,使得一部分粉末颗粒表面原子间的距离达到了点阵量级,从而产生键合力;一部分表面原子间的距离达到了一定小的程度,Vander Waals力使其结合.     

冷爆炸压实中纳米陶瓷粉末摩擦传热研究

对纳米陶瓷颗粒在爆炸冲击波作用下的受力特点进行了分析,利用准静态弹性力学方法研究了颗粒间的冲击摩擦力大小,并利用热传导的尺寸效应和冲击摩擦的强瞬态性(忽略传热的边界散射影响),研究了摩擦引起的颗粒内部温度变化和温度场分布.ITO纳米陶瓷粉末参数的计算分析表明,冷爆炸压实中纳米陶瓷粉末颗粒间很难形成摩擦焊接.要提高纳米陶瓷粉末爆炸压实后的结合强度,必须加强陶瓷颗粒在压实过程中的烧结行为,建议在纳米陶瓷粉末的爆炸压实中采取预热爆炸压实的工艺路线.     

粉末的爆炸压实工艺

为指导粉末爆炸压实工艺,综述了影响粉末爆炸压实的各种工艺参数,阐述了爆炸装置、装粉套筒、原始粉末、炸药以及其他因素的选择原则,分析了这些工艺因素对粉末爆炸成型质量的影响,提出了粉末爆炸压实中工艺参数优化的复杂性,并展望了爆炸压实工艺在粉末成型中的应用前景.     

添加Fe对CuCr触头材料显微组织的影响

采用机械合金化制粉、爆炸压实制坯、低温烧结成形制备了CuCr以及添加第三组元的CuCrFe触头材料,借助金相、扫描电镜和透射电镜等分析CuCr合金以及CuCrFe合金的显微组织,重点研究添加Fe对CuCr触头材料爆炸态和烧结态显微组织的影响.结果表明,添加Fe对CuCr机械合金化粉、CuCr合金爆炸态和烧结态的显微组织影响较大,即显著细化CuCr合金的显微组织;Fe主要固溶于Cr相中;添加Fe后CuCr合金的应变条纹和位错不仅没有消失,反而出现位错缠结的花纹,因而使CuCr合金的电导率进一步降低.     

CuCr合金在NaCl盐膜下的腐蚀行为

为了丰富CuCr合金的高温腐蚀研究,扩大其应用,采用金相、X射线衍射、扫描电镜/能谱及热重分析法研究了CuCr合金在700～900℃NaCl盐膜下的腐蚀行为,并讨论了在该环境下变形对CuCr合金腐蚀的影响及NaCl加速CuCr合金腐蚀作用的机制.结果表明:合金在NaCl盐膜下发生严重的腐蚀,其腐蚀产物疏松且易剥落,Cr相较Cu易腐蚀,且在腐蚀区以下的合金基体中有贫铬现象,变形能加速CuCr合金的腐蚀速率.     

添加Zr对快速凝固CuCr29合金液相分解微观组织的影响

使用限速熔体快淬技术研究了添加Zr对CuCr29合金液相分解微观组织的影响.研究结果表明,添加Zr可以有效地抑制快速凝固CuCr29合金的液相分解行为.当Zr元素的添加量大于1.0at%,快速凝固CuCr29合金的液相分解微观组织明显地得到细化.EDS分析和微观组织观察都表明,添加Zr元素后,在合金组织中只存在着富Cu基体和富Cr相,Zr元素以固溶形式影响着CuCr合金的凝固行为.由热力学分析可知,在CuCr29合金中添加Zr会降低过冷CuCr液体的混合自由能和液相分解的驱动力,从而增加液/固转变临界过冷度,使临界形核半径减小和形核速度增加,则快速凝固CuCr29合金的液相分解微观组织得到细化.     

多排钢管冲击波压扁行为研究

多排钢管吸能元件在冲击波作用下的大变形问题，对于抗爆结构的吸能装置设计具有重要意义。在单个钢管的动力压扁过程清楚的基础上，根据实验分析了多排钢管受径向冲击塑性行为，建立了八塑性铰机构，描述了钢管压扁位移速度场。给出了塑性铰附近的塑性弯矩值计算方法。     

Energy and deformation in implosive compression of axisymmetrical metal cylinders

Implosive powder consolidation of axisymmetrical components is based on the utilization of the available impact energy in both deforming plastically the cylindrical powder container and affecting the compaction of its contents. The level of the energy available for actual compaction depends not only on the mass and radial velocity of the container, but also, for the given overall impact energy delivered, on its material and geometry. In the course of extensive investigations of the process of explosive consolidation of polymer powders and their mixtures, the relationships between the reduction in the outer diameter and the explosive/tube mass and, further, between the generalized strain and impact have been established experimentally. This information in conjunction with the calculated energy data, enables an assessment of the deformation and compaction components of the impact energy to be made. It also provides an insight into the response of a cylinder to implosive shock loading.     

Microstructural characteristics of shock consolidated 2124 Al alloy compacts

2124 alloy powders have been compacted using explosive compaction. The effect of process parameters like explosive pad thickness and impact energy imparted to the powders on the microstructure and hardness across the cross-section of the compact have been investigated. When the thickness of the explosive pad was increased to 9.5 mm, three distinct microstructures with different hardness values were found across the cross-section of the compact. The size and shape of the θ phase precipitates were different in the fine grained structure when compared with that of the original particles and triple point junctions. Central porosity and pipe formation were observed when the thickness of the explosive pad was increased beyond 14.5 mm. Variation in the microstructure of the compact across the cross-section disappeared when the diameter of the compact was increased from 11 to 25 mm. This revised version was published online in November 2006 with corrections to the Cover Date.     

压实系数对内填砂卵石薄壁方钢管柱在冲击载荷下力学性能的影响分析

利用落锤冲击装置完成了不同压实系数下内填砂卵石薄壁方钢管柱侧向冲击试验,试验中记录了冲击力时程曲线,并获得了试件的破坏形态以及残余变形量。基于剩余承载力损伤评估准则,定义损伤度来判定冲击荷载下内填砂卵石薄壁方钢管柱损伤破坏程度,分析压实系数与柱损伤度的关系。试验结果表明:试件在侧向冲击荷载作用下,主要以局部破坏为主,并伴有一定量的整体弯曲变形;除了试件塑性变形中产生的塑性铰能消耗部分冲击能量外,内填砂卵石也能耗散一部分冲击能量,且压实越紧密,能量消耗越多,该组合柱表现出了较好的抗冲击性能;在一定压实系数范围内,损伤度随着压实系数增大出现先增大后减小的趋势,且砂卵石离散程度越小,损伤度的变化速率就越大。     

Energy Absorption Characteristics of Dual Phase Steel Tubes Under Static and Dynamic Loading

Abstract: Thin walled tubes are used as energy absorbing elements in automobile applications. The circular tube proves to be a popular energy absorber because it provides a reasonably constant operating force which is the prime characteristics of the energy absorber. Square and rectangular tubes are widely used in automobile structures as these cross sections are suitable for welding with other components in the structure and hence highly preferred. Advanced high strength steels can be utilised to absorb crash energy and minimise intrusion in the occupant zone. In this work circular, square and rectangular tubes made up of dual phase steel are tested in static and dynamic conditions. All the tubes are subjected to same amount of input impact energy but the specific energy absorption is higher in circular steel tubes. The results are compared with those for annealed tubes of same cross section. The effect of impact velocity is also studied by keeping the impact mass constant and varying the drop height. The experimental results are compared with the theoretical results and good agreement is found.     

钢纤维类型对超高性能混凝土高温爆裂性能的影响

为了探寻可以有效改善超高性能混凝土（Ultra-high-performance concrete,UHPC）抗火性能的钢纤维类型,本文试验测定了不同类型钢纤维（3种普通钢纤维和2种来自于废旧轮胎的再生钢纤维）增韧UHPC及空白组混凝土的从常温至800℃高温爆裂行为和断裂能。结果显示,未掺入任何钢纤维的空白组UHPC试件全都发生了严重高温爆裂,钢纤维可以显著减轻其高温爆裂但却不能避免爆裂的发生,而掺入端钩型普通工业钢纤维（长度为35 mm,直径为0.55 mm）的UHPC呈现出最优的抗高温爆裂性能,其次是掺入未附着橡胶颗粒（RSF）的再生钢纤维（RSFR）增韧UHPC。可见,钢纤维自身性能特征显著影响了钢纤维增韧UHPC的高温爆裂,相同掺量情况下混凝土单位体积内分布密度较大的钢纤维或者分布密度较小但可以显著增加混凝土断裂韧性（断裂能）的钢纤维比较适合应用于具有较高抗火要求的UHPC结构中。     

Static and dynamic axial crushing of spot-welded thin-walled composite steel–CFRP square tubes

Thin-walled metallic tubular components have long been adopted in the transportation industries, where the stable energy absorbing crushing process provides protection to occupants and cargo in the event of a collision. Fibre–epoxy tubes provide superior strength to weight ratios, however brittle failure modes may limit their energy absorbing capacity under large axial deformation. Composite steel–CFRP (carbon fibre-reinforced polymer) tubes are a recent advent, and combine the benefits of the stable, ductile plastic collapse mechanism of the steel and the high strength to weight ratio of the fibre/resin composite, to form a composite tube with high energy absorption capability. In this paper the applicability of steel–CFRP tubes to structures typical to the automotive industry is investigated. Thin-walled square tubes with width to thickness ratios up to 120 are cold-formed and spot-welded from high strength, low ductility steel, and subjected to static and dynamic axial compression. Four different steel tube geometries and two different carbon fibre matrix layouts are investigated, and comparisons are made between static and dynamic crushing, steel and composite steel–CFRP tubes, and regular and low ductility steels. It is shown that the crashworthiness properties of the steel–CFRP tubes exceed those of the steel tubes, however some issues particular to low ductility steels and such steels under impact conditions prove detrimental to the crashworthiness characteristics. Theoretical procedures are developed to design the crashworthiness characteristics of the composite tubes, and are shown to compare well with the experimental results.     

钢板夹泡沫铝组合板抗爆性能研究

鉴于泡沫铝材料优异的吸能特性和夹层结构在强度、刚度上的优势,提出了分层结构为钢板-泡沫铝芯层-钢板的抗爆组合板。对厚度为10 cm、7 cm和5 cm的组合板进行了5组不同装药量的爆炸试验,考察了各板在不同装药量爆炸条件下的变形及破坏情况,并对变形破坏过程进行了理论分析。研究表明:组合板承受爆炸冲击荷载时,通过局部压缩变形和整体弯曲变形吸收能量。钢板相同时,适当增大泡沫铝芯层厚度,增强面板与芯层间连接,可提高该组合板的抗爆性能,防止组合板发生剥离,减小其承受爆炸冲击荷载时产生的变形。     

玻璃钢纤维增强塑料薄壁管抗冲击性能的实验研究

本文采用分离式Hopkinson压杆（SHPB）实验系统,研究了玻璃钢纤维增强塑料（GFRP）薄壁管在低速冲击载荷作用下的抗冲击性能,探讨了薄壁管的截面形状和壁厚对其冲击破坏模式、动态应力-应变曲线和比吸能值（S_EA）的影响。实验结果表明：GFRP圆管的动态切线模量较方管的大,同壁厚的圆管的抗冲击性能较方管好;方管随壁厚的适当增加,抗冲击性能也增加。通过综合分析抗冲击性能评价参数,发现GFRP方管的吸能性能较圆管的好,且随壁厚的略微增加,吸能性能增强。与铝合金圆管相比,在相同实验条件下,GFRP圆管的动态压缩模量和冲击应力峰值较铝合金圆管大,峰值应变值较铝合金圆管小,比吸能值较铝合金圆管的大,GFRP管的抗冲击性能也较铝合金圆管好。其结果可为GFRP管类结构的优化设计及工程应用提供基础实验数据和给予理论指导。