泡沫铜有效热导率的有限元研究

以超声波辅助电沉积工艺制备得到的泡沫铜为研究对象,综合利用显微CT断层扫描技术和数字图像处理技术,实现了对泡沫铜结构的三维重构,进一步提出了一种能比较真实地反映泡沫铜三维结构特征的有限元简化模型。基于傅里叶热传导方程,利用有限元方法对泡沫铜的有效热导率进行有限元计算,建立了有效热导率与孔隙率之间的定量关系模型,并进一步研究了十四面体三棱柱单胞模型与热应力之间的关系。     

电沉积法制备泡沫铜

以聚氨酯软泡沫为基体，经预处理、化学沉积、电沉积和焚烧及热还原工艺制备了均匀分布三维网状孔结构的、高空隙率（〉９５％）且具有一定拉伸强度的泡沫铜材料，通过电子显微镜及生物显微镜观察了制备过程各步骤产品的形貌，用图像分析仪测定了泡沫铜的孔径分布，并运用线性电位扫描法对在泡沫上电沉积的阴极过程进行了研究。     

前驱体浸渍法制备泡沫镍屈服强度与孔结构的关系

采用有限元模拟技术计算不同孔结构泡沫镍的屈服强度,并以气雾化Ni-20Cr合金粉末为原料,以不同孔径的聚氨酯泡沫为模板,控制浸渍工艺制备出不同孔径与不同密度的泡沫镍铬合金,研究合金屈服强度随密度与孔径尺寸的变化关系。有限元模拟计算结果表明,开孔泡沫金属材料的屈服强度符合Gibson-Ashby方程,在开孔泡沫金属材料密度一定的情况下,材料的屈服强度不随孔径的变化而变化。实验结果表明,对于相同孔径的泡沫金属材料,其屈服强度和相对密度的关系为σ/σs与相对密对(即ρ/ρs)的1.5次方呈线性关系(σ和σs分别为泡沫材料与致密材料的屈服强度;ρ和ρs分别为泡沫材料与致密材料的密度);而具有相同密度和不同孔径的泡沫镍铬合金,其屈服强度很接近,验证了开孔泡沫金属材料屈服强度随密度的变化规律符合Gibson-Ashby方程。     

电沉积法制备泡沫镍的研究

采用聚氨脂泡沫为基体,经预处理、化学镀、电沉积工艺制备了均匀分布三维网状孔结构的高空隙率泡沫镍。通过电子扫描电镜(SEM)观察了制备过程中泡沫的形貌,并测定了泡沫镍的主要物理性能。     

电沉积法制备多层泡沫铜/镍

采用聚氨脂泡沫为基体,经预处理、化学镀、电沉积制备了均匀分布三维网状孔结构的高空隙率多层泡沫金属铜/镍。通过电子扫描电镜(SEM)观察了泡沫的形貌,并测定了多层泡沫材料的主要物理性能。     

新一代新能源车驱动电机的高强硅钢应用技术研发

阐述了电驱动汽车所用电机的特点以及对硅钢的需求标准,并通过实验对比分析了高屈服强度无取向硅钢和传统无取向硅钢的电磁性能以及力学性能,通过有限元模型验证分析应用了高屈服强度硅钢的电机在高转速时可以达到低损耗、高机械强度等需求,为软磁材料的应用与电机结构的优化形成闭环模式提供了帮助。     

泡沫铝制备与其压缩性能研究

采用粉末致密化发泡（PCF）工艺制备了泡沫纯铝,对制备过程及影响孔结构的因素进行了分析.系统研究了压力、发泡温度、发泡时间、发泡剂含量和粒度对泡沫纯铝结构变化的影响规律,用自行设计的软件FoamScan对孔结构进行了描述.得出了试验条件下的优化工艺参数配置.进行了泡沫铝压缩性能测试,通过理论模型、性能测试数据作图对比的方法获得了孔隙率83%～87%泡沫纯铝的屈服强度表达式.确定了泡沫纯铝的制备工艺、结构、性能的相互关系.     

仿生预置晶种对钛基体表面电沉积制备羟基磷灰石涂层的影响

采用仿生预置晶种法在Ti基体表面构筑HAP晶种,为HAP涂层的形成提供核点,后通过电沉积在低温条件下获得HAP涂层。通过扫描电镜、X射线衍射和红外光谱以及拉曼光谱研究仿生预置晶种对电沉积制备HAP涂层的微观结构进行分析,并用MTT法进行细胞毒性测试。结果表明:随着仿生预置晶种时间从24 h延长至48 h,电沉积制备的HAP涂层表面形貌从三维网状结构向蜂窝状结构转变。相对于无预置晶种电沉积制备的HAP涂层,仿生预置晶种后电沉积得到的HAP涂层更为均匀致密,与基体结合强度更高,且更有利于成骨细胞的增殖、代谢和生长。     

方坯连铸结晶器三维热力耦合分析

采用ANSYS软件建立方坯连铸结晶器三维热力耦合模型,利用节点温度传递法模拟拉坯过程,对模型进行分析。通过瞬态分析得出结晶器铜壁和铸坯的三维稳态温度场,以铜壁温度场为热载荷,通过间接耦合方法分析结晶器铜壁受力状态。结果表明:铜壁最高温度点出现在结晶器热面中心距顶端约150 mm处(距弯月面约50 mm),最高温度142℃低于铜壁再结晶温度;铜壁热面最大位移出现在距铜壁顶端200 mm区域(弯月面下100 mm区域)角部位移为0. 112 mm;在弯月面附近等效应力达到最大值,从等效应力来看,整体应力值都在结晶器应力屈服强度之内,因此结晶器不会永久变形。     

稀土对电沉积法制备泡沫铜化学预镀工艺的影响

通过实验手段，研究了稀土对电沉积法制备泡沫铜化学预镀工艺的影响。结果表明，在化学镀液中加入稀土元素，镀液稳定，使用次数多，产生的铜粉较少，且镀层厚平整。     

Deformation Behavior Estimation of Aluminum Foam by X-ray CT Image-based Finite Element Analysis

Aluminum foam is a lightweight material owing to the existence of a large number of internal pores. The compressive properties and deformation behavior of aluminum foam are considered to be directly affected by the shape and distribution of these pores. In this study, we performed image-based finite element (FE) analyses of aluminum foam using X-ray computed tomography (CT) images and investigated the possibility of predicting its deformation behavior by comparing the results of FE analyses with those of actual compressive tests. We found that it was possible to create an analytic model reflecting the three-dimensional (3D) pore structure using image-based modeling based on X-ray CT images. The stress distribution obtained from image-based FE analysis correctly indicates the layer where deformation first occurs as observed in actual compressive tests. Also, by calculating the mean stress of each plane perpendicular to the direction of compression based on the stress distribution obtained from image-based FE analysis, it was found that deformation begins in the layer containing the plane with maximum stress. It was thus possible to estimate the layer where deformation begins during the compression of aluminum foam.     

CFRP?泡沫铝夹芯结构控制臂优化设计

为满足控制臂的轻量化设计需求,提出了一种采用碳纤维复合材料（CFRP）?泡沫铝夹芯结构的汽车悬架控制臂,并对CFRP面板进行结构优化设计。通过泡沫铝准静态压缩试验验证了泡沫铝六面体胞孔模型的准确性,利用CFRP力学性能试验获得了碳纤维复合材料的性能参数,设计一种由CFRP?泡沫铝夹芯结构本体和铝合金连接件组成的悬架控制臂,控制臂本体与连接件之间采用胶?螺混合连接。在此基础上,建立CFRP?泡沫铝夹芯结构控制臂有限元模型,利用多层次优化方法对CFRP面板进行铺层优化。结果表明,相较于钢制控制臂,优化后夹芯结构控制臂的质量减少了26%,同时强度、刚度和模态性能都有所改善。      

Synthesis and characterization of Al foam, Al alloy foam and Al-SiC composite foam

Open-celled Al foam, Al-Mg alloy foam and Al-SiC composite foams were prepared by means of sintering and dissolution process. The microstructures and compressive behaviour of these foams were studied. It was found that at the same relative density, the compressive strength increases with the addition of alloying element and silicon carbide. Energy absorption capacity curves show that the energy absorption capacity increases with the increase in strain.     

2219铝合金网格壁板应力松弛时效行为分析

整体网格壁板在航天器结构应用中,采用热压罐成形作为2219T87铝合金网格壁板的成形工艺。在壁板与模具贴模之后,通过应力计算和有限元仿真可得到不同厚度层受到的应力大小。在热压罐中时效时,由于拉、压应力的影响,壁板不同位置材料性能有所差异。结果表明:应力的计算值和仿真值吻合,说明模型的有效性;在透射电子显微镜下观察发现,受拉、压应力区的析出相较低应力区的细小、密集,压应力区又比拉应力区的析出相更加细小密集,这是因为受应力区会产生大量的位错,从而为沉淀物的析出提供更多的形核位置,产生更多细小、针状的析出物,在宏观上反映为析出相越细小、密集,抗拉强度及硬度越高。     

无监督数据挖掘辅助激光诱导击穿光谱用于铜冶炼光谱结构解析

在有色冶炼领域,元素成分检测是保证冶炼质量的重要一环。目前国内有色冶炼企业多采用X射线荧光光谱法进行检测,该方法需要样品制备,造成冶炼状态无法实时反馈,严重影响冶炼过程优化。研究了无监督数据挖掘算法辅助激光诱导击穿光谱技术用于铜冶炼光谱结构解析。实验中,首先选择4种铜冶炼物料作为实验样品,然后利用激光诱导击穿光谱技术(LIBS)激发样品获得18750个光谱数据,通过盲源分离技术对所有光谱进行分析,最终提取得到3个特征光谱。进一步研究发现,3个特征光谱与Cu、Fe、Ca元素光谱有一一对应关系。在此基础上,提出了LIBS光谱的定量化评价指标,量化结果表明分解模型对18750个光谱都能达到很高的评分,说明铜冶炼光谱能够良好地被3个特征光谱重构,即铜冶炼光谱存在显著的光谱结构。以上结论在实际应用中具有重要研究价值,可用于光谱快速评价、异常光谱剔除、光谱信号提纯、元素谱线选取、样品定性/半定量分析等,为LIBS技术应用于在线铜冶炼成分分析奠定基础。     

无监督数据挖掘辅助激光诱导击穿光谱用于铜冶炼光谱结构解析

在有色冶炼领域,元素成分检测是保证冶炼质量的重要一环。目前国内有色冶炼企业多采用X射线荧光光谱法进行检测,该方法需要样品制备,造成冶炼状态无法实时反馈,严重影响冶炼过程优化。研究了无监督数据挖掘算法辅助激光诱导击穿光谱技术用于铜冶炼光谱结构解析。实验中,首先选择4种铜冶炼物料作为实验样品,然后利用激光诱导击穿光谱技术(LIBS)激发样品获得18750个光谱数据,通过盲源分离技术对所有光谱进行分析,最终提取得到3个特征光谱。进一步研究发现,3个特征光谱与Cu、Fe、Ca元素光谱有一一对应关系。在此基础上,提出了LIBS光谱的定量化评价指标,量化结果表明分解模型对18750个光谱都能达到很高的评分,说明铜冶炼光谱能够良好地被3个特征光谱重构,即铜冶炼光谱存在显著的光谱结构。以上结论在实际应用中具有重要研究价值,可用于光谱快速评价、异常光谱剔除、光谱信号提纯、元素谱线选取、样品定性/半定量分析等,为LIBS技术应用于在线铜冶炼成分分析奠定基础。     

Three-Dimensional Characterization of SiC Particle-Reinforced Al Composites Using Serial Sectioning Tomography and Thermo-mechanical Finite Element Simulation

In this study, a serial sectioning technique was employed in order to visualize the three-dimensional (3D) structure, and to accurately simulate the mechanical and thermal behaviors of SiC particle-reinforced Al composites. Sequential, two-dimensional (2D) optical images of the microstructure were acquired after polishing, and then reconstructed to develop 3D geometries for microstructural analyses and finite element modeling. Experimental compressive and thermal expansion tests were performed for comparison with the finite element method results. The Young’s modulus and thermal expansion coefficient of the composite, predicted using the 3D microstructure-based finite element analyses, were in good agreement with the experimental results. Furthermore, the 3D microstructure-based finite element model showed anisotropic thermal expansion behavior that was previously disregarded in the other models used in this study. Therefore, it was confirmed that the combined approach of serial sectioning and finite element modeling provides a significant improvement over 2D and 3D unit-cell modeling.     

The strain rate effect of an open cell aluminum foam

The dynamic compressive behavior of an open-cell commercially pure aluminum foam was experimentally investigated with a split Hopkinson bar (SHPB) and numerically simulated using the finite element (FE) method. It is found that the flow stress increases with increasing strain rate, demonstrating the existence of strain rate dependence in the present aluminum foam. This dependence is believed to originate from the polygonal pore architecture, the relatively high density, the intrinsic property of aluminum, as well as the friction force between the contacted cell walls.     

Hydroxyapatite fiber reinforced poly(alpha-hydroxy ester) foams for bone regeneration

A process has been developed to manufacture biodegradable composite foams of poly(DL-lactic-co-glycolic acid) (PLGA) and hydroxyapatite short fibers for use in bone regeneration. The processing technique allows the manufacture of three-dimensional foam scaffolds and involves the formation of a composite material consisting of a porogen material (either gelatin microspheres or salt particles) and hydroxyapatite short fibers embedded in a PLGA matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength.