利用纳米压入加载曲线确定金属薄膜的屈服强度和硬化指数 Ⅰ.数值模拟

针对纳米压入仪上普遍使用Berkovich三棱锥压头,本文分别考虑理想与纯化两种压头尖端几何情况,并使用三维弹塑性大应变有限元分析软件ABAQUS,对沉积在陶瓷基体上金属薄膜的纳米压入加载过程进行模拟计算,建立了膜、基材料基本力学性能参量及压头相对钝化量同纳米区入加载曲线间的函数关系,进而提出了利用纳米压入仪测得的连续压入加载曲线确定陶瓷基体上金属薄膜屈服强度和硬化指数的一般方法     

利用纳米压入加载曲线确定金属薄膜的屈服强度和硬化指数：Ⅱ.实 …

通过比较实测与计算所得整体材料纳米压入加载曲线及Ｂｅｒｋｏｖｉｃｈ压头的面积函数,对已建立的Ｂｅｒｋｏｖｉｃｈ压头绝对钝化量的确定方法进行了实验验证。在此基础上,测定了蒸发镀制在Ｓｉ单晶上三种不同膜厚Ａｌ膜的屈服强度和硬化指数。并与拉伸分离法获得的结果进行了比较。结果表明,利用纳米压入加载曲线确定陶瓷基体上金属薄膜基本力学性能的方法是可行的。     

利用纳米压入加载曲线确定金属薄膜的屈服强度和硬化指数：Ⅰ.数 …

针对纳米压入仪上普遍使用Ｂｅｒｋｏｖｉｃｈ三棱锥压头。本文分别考虑理想与钝化两种压头尖端几何情况,并使用三维弹塑性大应变 有限元分析软件ＡＢＡＱＵＳ,对沉积在陶瓷基体上金属薄膜的纳米压入加载过程进行了模拟计算,建立了膜、基材料基本力学性能参量及压头相对钝化量同纳米压入加载曲线间的函数关系,进而提出了利用纳米压入仪测得的连续压入加载曲线确定陶瓷基体上金属薄膜屈服强度和硬化指数的一般方法。     

测定金属薄膜屈服强度的纳米压入法研究

利用有限元数值分析方法,对球形刚性压头压入由金属膜与硅基体组成的膜－基体系的加载过程进行了模拟计算。建立了薄膜硬化指数同载荷－位移曲线的特征值, 服强度,硬化指数及扬氏模量同最大压入载荷间的关系。据此,可由纳米压入仪实测所得载荷－位移曲线的特征值与最大压入载荷,确定金属薄膜材料的应变硬化指数和屈服强度。     

基于Berkovich压痕的金属材料弹塑性参数仪器化压入识别方法

针对Berkovich压痕提出一个独立的仪器化压入响应参数-中边距与名义中边距之比d/dn,用于衡量压痕鼓凸/沉陷程度。基于量纲分析和有限元数值仿真,建立中边距与名义中边距之比d/dn、名义硬度Hn、比功We/Wt与金属材料弹塑形参数之间的无量纲函数关系式,并以此为基础建立了基于Berkovich压痕的金属材料弹塑形参数仪器化压入识别方法。该方法仅利用单一Berkovich压头仪器化压入金属材料所得载荷-位移曲线及Berkovich压痕即可确定金属材料的弹性模量E、应变硬化指数n、条件屈服强度σ0.2及强度极限σb。4种常用金属结构材料弹塑性参数的仪器化压入识别结果验证了该方法的有效性。     

多晶铜膜纳米压入蠕变性能

在JGP560V磁控溅射镀膜设备上镀制多晶铜膜,利用纳米压入技术测量了其室温下的蠕变性能.结果表明:由于不同加载方式下,材料加工硬化程度的不同造成了应力指数的差异,因而,不同加载方式对测得的铜膜蠕变应力指数有比较大的影响;由于材料在高载荷时在压头下端产生更多的位错,阻碍了压头的压入,使蠕变率降低,因而,随着保载载荷的升高,蠕变应力指数变大.     

单晶金刚石微观性能的纳米压入测量研究

研究单晶金刚石的微观机械性能,可为金刚石工具的研磨和使用性能评价提供技术依据。提出以纳米压入技术研究单晶金刚石微观尺度机械性能,分析了纳米压入技术的主要原理及其技术特点,进行了纳米压入测量实验并分析了各种因素的影响。研究表明:采用10mN的ADO载荷和小于10mN的最大压入载荷对单晶金刚石{100}晶面进行纳米压入测量,可显著减小甚至避免金刚石压头的变形和损伤,获得有效的压入曲线及数据;但在多次测量后会出现金刚石压头的累积钝化。基于测量过程和结果的分析,提出了提高测量有效性的方法。     

基于原子力显微镜的薄膜原位压痕力学性能研究

基于原子力显微镜(AFM)和扫描电子显微镜(SEM)建立了一套原位纳米压痕测试系统。该系统可以实现控制带有金刚石(Cube corner)压头的AFM微悬臂梁对样品进行压入实验,并得到载荷-位移曲线,同时可以对压痕过程进行原位SEM实时观察。发展了一种基于AFM微悬臂梁加载和原位SEM压痕图像分析的力学性能测试方法,通过测量压入最大载荷和原位SEM测量压痕残余面积得到塑性薄膜的硬度和弹性模量。利用此方法对磁控溅射硅衬底上纳米晶银薄膜进行了压痕实验,并与Nanoindenter G200型纳米压痕仪实验进行对比研究。结果表明,原位AFM压痕方法具有高的载荷和位移分辨率,可以实现纳牛至微牛级的压痕实验,通过测量压痕面积得到塑性薄膜的硬度值,减小了使用Oliver-pharr方法中软膜硬基底上凸起(Pile-up)效应的影响,计算结果也具有好的测试精度和可靠性。     

加载速率对Al膜纳米压入蠕变性能的影响

纳米压入仪对Si片上晶Al膜进行的压入蠕变实验表明,加载方式对Al膜的蠕变性能有明显影响.随加载速率和载荷的增大, Al膜的总蠕变量和应力指数均有较大升高 且蠕变初期可能存在异常高蠕变率.分析认为这与是加载过程中未及发生的塑性变形的持续释放有关.对于确定的薄膜材荆及组织结构,加载过程中积攒的塑性变形量及其释放速率将影响不同加载条件下的总蠕变量和应力指数.     

加载速率对Al膜纳米压人蠕变性能的影响

纳米压入仪对Si片上多晶Al膜进行的压入蠕变实验表明，加载方式对Al膜的蠕变性能有明显影响随加载速率和载荷的增大，Al膜的总蠕变量和应力指数均有较大升高．且蠕变初期可能存在异常高蠕变率．分析认为这与是加载过程中未及发生的塑性变形的持续释放有关．对于确定的薄膜材料及组织结构，加载过程中积攒的塑性变形量及其释放速率将影响不同加载条件下的总蠕变量和应力指数。     

板料成形中材料模型的研究进展

介绍了板料成形数值模拟中材料模型的研究进展。将材料模型的理论研究分为屈服准则、强化模型、流动法则、加卸载历史4个方面,并进行简要综述;对材料在循环加载条件下应力应变曲线的实验获取方法进行了探讨,重点介绍了板料压缩、三点弯曲实验确定材料反向加载应力应变曲线的原理和方法;对当前屈服准则、强化模型的研究热点和发展方向进行了分析。     

Anisotropy and texture in thin copper films—an elasto-plastic analysis

The role of elastic anisotropy on the stress inhomogeneity and effective behavior of columnar grained textured Cu thin films have been analyzed within a continuum framework. The analysis is based on a three-dimensional model of a film/substrate system. The film exhibits a fiber texture with (111), (001) and randomly oriented grains. Mainly two load cases have been considered. Biaxial loading of a film deposited on a silicon substrate and tensile loading of a film deposited on a polyimide substrate. The stress distributions in the (111) and (001) grains were generally found to be very different when subjected to biaxial loading and quite similar when subjected to tensile loading. When plastic behavior is invoked, a structural hardening effect is observed. The plastic behavior differs significantly between biaxial and tensile cyclic loading respectively. A new orientation dependent hardening law is proposed. This hardening law causes the plastic hardening behavior to be orientation dependent and scale with elastic anisotropy. The newly proposed hardening law is demonstrated on a film with small grain aspect ratio.     

Experimental investigation of plastic deformation of stainless steel for cyclic loading at low temperature

Cyclic plastic deformation of stainless steel SUS 304 is experimentally investigated at low temperature of liquid nitrogen (77 K) under various cyclic loading conditions Thin walled tubular specimens are subjected to cyclic loading under constant strain ranges. At low temperature, the material shows remarkable hardening by cyclic loading comparing with cyclic loading at room temperature. The hysteresis curves of stress-strain relations by cyclic loading are saturated by increasing the cycle numbers. The saturation tendency depends on loading direction. The saturated stress values are related with cumulative plastic strain of cyclic loading. The prestraining is given at 77 K by axial and torsional loadings, and subsequent cyclic loading under constant strain range is conducted at 77 K. The cyclic stress-strain curves are saturated by increasing cyclic numbers. At small cyclic numbers, cyclic plastic deformation depends on the prestrain direction. The directional effect of pre-strain on cyclic loading becomes small with increasing number of cycles.     

Yield surface of polycrystalline thin films as revealed by non-equibiaxial loadings at small deformation

A biaxial device developed at DiffAbs beamline of the SOLEIL synchrotron facility has been employed to determine the applied strains in film–substrate composites using both X-ray diffraction and digital image correlation measurements. Such an experimental combination is used for the first time to determine the yield surface of a polycrystalline thin film deposited on a polyimide substrate. In situ biaxial tensile tests under different biaxial planar load ratios were performed on W/Cu nanocomposite thin films deposited on flexible substrates. The effect of loading path on the yield stress of W/Cu nanocomposites is presented by considering a large range of proportional loadings. By comparing experimental results with theoretical models, this study reveals the brittle behaviour of W/Cu nanocomposite thin films at small deformations.     

Si(100)衬底上(110)取向La_(2/3)Sr_(1/3)MnO_3薄膜的制备与性能

用脉冲激光沉积法在Si(100)衬底上制备了(110)择优取向的La2/3Sr1/3MnO3薄膜,研究了环境氧压对薄膜结晶度、取向、表面形貌和微结构的影响。结果表明:10Pa氧压下沉积的薄膜具有高结晶度的(110)择优取向,晶粒分布均匀,晶粒分布均匀,表面均方根粗糙度Rrms为1.35 nm。与无明显择优取向的薄膜相比,(110)择优取向的La2/3Sr1/3MnO3薄膜具有较高的饱和磁化强度(Ms)、金属-绝缘体相变温度(TM-I)和较低的电阻率(ρ)。     

Analysis and estimation of yield strength of API X80 linepipe steel pipe by low-cycle fatigue tests

In the present study, spiral piping was conducted on API X80 linepipe steel, and the outer and inner wall pipe yield strengths were measured. A low-cycle fatigue test was conducted on a leveled X80 steel sheet to simulate piping and flattening processes, and the strain hardening and Bauschinger effects, induced from different strain histories, were evaluated and combined using Swift??s equation and the Bauschinger stress parameter, respectively. By analyzing the stress-strain curves obtained from the low-cycle fatigue test, the yield strengths of the outer and inner walls were estimated to be 592 MPa and 492 MPa, respectively, which are lower by 20?C80 MPa than that of the actual pipe used. Possible reasons for measured and estimated yield strength differences could be the simulation determining procedure of the pre-strain and Bauschinger stress parameters, preposition of same strain hardening behavior depending on strain history, and pre-strain differences depending on thickness location in the steel sheet during piping.     

Derivation of mechanical characteristics for Ni/Au intermetallic surface with SAC305 solder

Many surface finish methods are used to connect a substrate with the electric components of IT products in the micro-packaging process, and various types of lead-free solder have been developed as alternative materials to lead-based solder to reduce environmental contamination. However, there has been little research on the mechanical properties of the inter-metallic surface which is generated in the bumping process between the lead-free solder and surface films such as Ni/Au. The present work is to derive the material properties of a Ni/Au inter-metallic surface with SAC305 solder. A series of indentation tests were carried out by changing four nano-scale indentation depths and two strain rates. Also, a reverse algorithm method was adopted to determine the elastic-plastic stress-strain curve based on the load-displacement curve from the indentation test data. As a result of the material characterization effort, the mean elastic modulus, yield strength and strain hardening exponent of IMC with Ni/Au finish were determined.     

High orientation Al films growth on LiNbO3 single crystal and its adhesion

High orientation Al films were deposited on 64°Y-XLiNbO3 substrate by DC magnetron sputtering and the influence of deposition temperature on microstructure and adhesion properties of Al films were investigated. The results show that crystallographic orientation of films varies with substrate temperature and the adhesion strength between LiNbO3 and Al films strongly depends on crystallographic orientation of Al films. The (111) orientated Al films shows stronger adhesion strength to LiNbO3 substrate than (100) orientated films. There is an optimum substrate temperature of 60 ℃ and hardening temperature of 200 ℃ for obtaining high (111) orientated Al films with good surface structure and adhesion property. Using this Al film, we have successfully fabricated the SAW filters with high frequency of about 1.89 GHz.