金属丝弹性模量的测量方法研究

通过用纳米压入法和静态拉伸法对β-Ti丝、不锈钢丝以及3种NiTi丝进行弹性模量的测量。实验表明，纳米压入法弹性模量比静态拉伸法弹性模量大，并且材料的弹性模量越低，二者相差越大，其原因同试样的表面硬化层和尺寸效应有关。通过分析比较，建立了金属丝弹性模量的纳米压入法和静态拉伸法所得值之间的相关关系。     

金属纤维弹性模量的振动法测量

针对测量金属纤维弹性模量传统方法存在的局限,提出了一种用振动法测量金属纤维弹性模量的新方法。详细介绍了该方法的测量原理、测量装置、测量过程及误差分析。分别选择了钼丝和铂铱25合金纤维为测量对象,将被测材料制备成微悬臂梁试样,通过瞬态激励使悬臂梁产生短暂振荡,然后获得悬臂梁固有频率,再通过计算公式求出金属纤维材料的弹性模量。与静态拉伸法测量结果进行了比对,试验证明两者测试结果较为吻合。分析了悬臂梁长对测试结果的影响,结果表明:只有当梁长大于或等于8倍梁高(直径)时,这种影响才可忽略不计。     

梁三点弯曲法测量薄膜弹性模量

用电刷技术在不锈钢基体一侧表面上刷镀了Cu膜，用电镀技术在不锈钢基体一侧表面或双侧表面上制备Ni膜。用梁三点弯曲法在自制的设备上测量不锈钢基体以及不锈钢基体上不同厚度Cu膜和Ni膜的弹性模量E。研究表明：在测量的膜厚范围内(7μm-15μm)，Cu膜和Ni膜的弹性模量E不随膜厚变化，并且接近各自块材的弹性模量。     

超声相控阵法测量材料的弹性模量

提出了一种基于超声相控阵测速的材料弹性模量测量方法。采用相控阵列的声速测量方法能获得精细的超声信号波组,从而能分析出超声信号的幅值与相位,对材料纵波声速与横波声速的测量精度可达到5位有效数字,进而能高精度地测量材料的弹性模量,以便对材料的力学性能进行无损评价。     

“敲击法”测量弹性模量的研究

超声振动系统设计及分析时要用到声速,声速计算时要用到弹性固体材料的弹性模量、密度.固体密度易测量,弹性模量较难测量.实验证明:"敲击法"测量弹性模量的原理、方法是简便有效的.     

鼓泡法测量高分子和金属薄膜弹性模量的方法探讨

在自制的鼓泡仪上对高分子薄膜和金属镍膜的弹性模量进行了测量,并研究了孔径对薄膜弹性模量测量的影响。结果表明,高分子薄膜的弹性模量为2.7±0.2GPa,孔径对薄膜弹性模量的测量没有影响;受仪器精度限制,该仪器目前尚难用于金属镍膜的弹性模量的精确测量。     

异质金属丝电弧喷涂工艺的试验研究

本文主要介绍利用电弧做热源,通过电弧喷涂的工艺方法,使不锈钢丝和铝丝瞬间同时熔化后喷射粘附在基体金属表面上,得到一种复合材质涂层。试验中通过改变送丝速度和电弧电压等参数,制备一些涂层试样,并对涂层进行了宏观和微观组织结构检测、X射线衍射分析和显微硬度测量。由试验分析结果可以得到以下结论: (1)通过调节送丝速度和电弧电压等参数,铝和钢的异丝喷涂是可以实现的;(2)涂层的颗粒大小可以通过改变工艺参数来控制;(3)铝和钢异丝喷涂层中有Fe-Al化合物生成,其硬度高于铁、铝纯金属;(4)利用电弧喷涂装置有望使异质金属丝同时熔化并发生冶金反应,从而制备具有特殊性能的金属化合物涂层。     

弹性模量与塑性变形变化规律试验研究

弹性模量是影响冲压回弹量的重要材料性能参数,在工程应用和回弹数值模拟中一般认为弹性模量为常数.而实际上,弹性模量随塑性变形的增大不断变化,因此其变化对工程中的回弹量评估和数值模拟回弹预测精度有很大的影响.本文针对在汽车和航空工业中广泛应用的铝合金和钢板,采用动力试验方法,对ST14钢及3A21、2024-T3和2A12铝合金的弹性模量在塑性变形中的变化规律进行了试验研究,得到了弹性模量值与等效塑性应变的变化规律,并采用分段线性函数进行了描述.研究结果为进一步研究弹性模量随塑性变形的变化规律及探讨其本质提供了依据,也预示了一种提高有限元回弹预测精度的解决办法.     

特种模型材料弹性模量的测量

层状复合方法适用于测定高阻尼材料的弹性模量。特种模型材料由环氧树脂、增韧剂、固化剂和金属粉构成。用层状复合方法测定了特种模型材料的弹性模量，得到的数据分散性小。特种模型材料的弹性模量随着金属粉的增加而增加。     

板材杨氏模量对称三点弯曲测试方法及测试装置

金属板材在弹性对称三点弯曲时最大挠度与集中力呈线性比例关系,由该关系可求出板材的杨氏模量。文章提出利用对称三点弯曲的原理测量金属板材杨氏模量的方法,并设计加工了相应的试验装置,该装置结构简单,制作成本低,挠度测量采用百分表,测量精度高。实测了1mm厚铝板和铜板及3.1mm厚钢板的杨氏模量,测量结果稳定可靠。     

Determination of Young's modulus and Poisson's ratio for coatings

Designing thin-film coatings to meet engineering needs requires the knowledge of accurate mechanical properties of the coatings. Young's modulus and Poisson's ratio are two basic mechanical properties of materials, which should be conveniently measured. This paper reports a direct and non-destructive method for the measurement of the Young's modulus and Poisson's ratio of a thin-film coating and its substrate based on the extended Hertz theory for the contact of coated bodies. The theory is used to analyze load-displacement data from a spherical indentation in the elastic range, in which the substrate effect is intrinsically modeled. The Young's modulus and Poisson's ratio are determined at the same time through minimizing the difference between the measured and specially defined modified Young's moduli. Two sets of validation experiments are also reported. This new method does not require any assumptions on pressure distribution and Poisson's ratio and can be easily incorporated into current indentation analysis systems.     

Determination of Young's modulus and yield stress of porous low-k materials by nanoindentation

In the present study, the concept of the ‘effectively shaped indenter’ was used to analyse nanoindentation data of rather soft films on hard substrates. This approach was introduced for monolithic materials by Pharr and co-workers some years ago [G.M. Pharr, A. Bolshakov: J. Mater. Res. 17 (2002) 2660, A. Bolshakov, W.C. Oliver, G.M. Pharr, MRS Symp. Proc 356 (1995) 675]. Substrate to layer moduli ratios range from nearly 60 to 160. With such soft and brittle materials (Young's modulus nearly 3 GPa or smaller, yield strength around 100 MPa), no completely elastic measurements can be performed even at low loads. Hence, an established method for the determination of yield stresses by means of nanoindentation, namely that of loading-partial-unloading [N. Schwarzer: ASME J. Tribology 122 (2000) 672, T. Chudoba, N. Schwarzer, F. Richter: Thin Solid Films 355-356 (1999) 284, T. Chudoba, N. Schwarzer, F. Richter: Surf. Coat. Technol. 127 (2000) 9] was not applicable. However, the ‘effectively shaped indenter concept’ allows one to separate the elastic stresses due to the penetration from the residual stresses caused by the inelastic deformation, assuming that their influence on the elastic stress field is small. Thus, by using this approach critical yield stresses of soft porous materials have been obtained. Additionally, the Young's modulus of these materials has also been determined by means of laser-generated surface acoustic wave (LSAW) measurements and the Oliver and Pharr method. In the latter case, a special extrapolation method for the indentation modulus had to be applied to correct for the substrate influence. The results by the different methods are compared and their deviations are discussed. As there is no complete solution available for the correction of the substrate influence on Young's modulus of the film when plastic deformation occurs during indentation, the authors are searching for an approach to approximate the elastic properties of a soft film on a hard substrate. It seems that the determination of the Young's modulus of very soft films cannot be separated from the determination of the yield stress. As an example for a low-k material actually of interest, porous silica xerogel films on silicon with porosities of 38 up to 51 vol.% were investigated.     

A constitutive model for spring-back prediction in which the change of Young's modulus with plastic deformation is considered

In order to improve the prediction capability of spring-back in the computational analysis of sheet metal forming processes, a stress–strain constitutive formulation of non-linear combined hardening rule has been proposed in this paper according to non-linear kinematic hardening theory of Lemaitre and Chaboche and Hill's 1948 anisotropic yielding function. Traditionally, Young's modulus is considered as a constant in engineering application and numerical simulation. In fact, it decreases with plastic deformation. So the effect of the change of Young's modulus with plastic strain on spring-back is considered in the constitutive model. The algorithm of stress update is elastic prediction, plastic correcting and radial returning. Numerical results and experimental results show that the proposed constitutive model significantly improves the prediction accuracy of spring-back.     

Determination of reduced Young＇s modulus of thin films using indentation test

The flat cylindrical indentation tests with different sizes of punch radius were investigated using finite element method (FEM) aimed to reveal the effect of punch size on the indentation behavior of the film/substrate system. Based on the FEM results analysis, two methods was proposed to separate film's reduced Young's modulus from a film/substrate system. The first method was based on a new weight function that quantifies film's and substrate's contributions to the overall mechanical properties of the film/substrate system in the flat cylindrical indentation test. The second method, a numerical approach, including fitting and extrapolation procedures was put forward. Both of the results from the two methods showed a reasonable agreement with the one input FE model. At last, the effect of maximum indentation depth and the surface micro-roughness of the thin film on the reduced Young's modulus of the film/substrate system were discussed. The methods proposed in the present study provide some new conceptions on evaluating other properties of thin films, e.g. creep, for which a flat-ended punch is also employed.     

针状铁素体钢的高温屈服应力及弹性模量

用热模拟试验机研究了C-Mn-Mo-Nb针状铁素体钢的相变特性,采用拉伸和压缩方法检测了试验钢在奥氏体化加热后冷却至不同温度时的屈服应力和弹性模量,采用高温拉伸试验机对比检测了加热至奥氏体化以下,试验温度时钢的屈服应力和弹性模量。结果表明：在奥氏体化后冷却过程中,钢的屈服应力在650～500℃相变温度范围内从约75 MPa提高至约450 MPa,但弹性模量在针状铁素体相变温度区间（600℃左右）出现谷值。在550℃以上,从室温加热至试验温度拉伸方法获得钢的屈服应力和弹性模量较奥氏体化加热法的高。相变过程中,晶体结构转变及位错密度增加是弹性模量波谷产生的主要原因;晶体结构转变、位错密度增加和析出使屈服应力急剧增加。而相同组织状态下,钢的屈服强度和弹性模量主要受温度影响。不同测试方法所得数据的差异,主要是由不同的组织结构转变而非测试方法造成。     

Tensile testing as a method for determining the Young''s modulus of thin hard coatings

The present paper describes and evaluates a tensile testing method for determination of the Young's modulus of thin hard coatings. When applied to PVD TiN and NbN coatings on stainless steel foils, the elastic modulus obtained through force—strain plots ranged between 380 and 425 GPa for TiN coatings, and was 350 GPa for the single NbN coating tested. It is concluded that the method is easy to perform and allows reliable determination of the Young's modulus of thin hard coatings, and that it can be applied to almost any kind of coating on a wide range of substrate materials.     

Young's modulus and stress intensity factor determination of high velocity electric arc sprayed metal-based ceramic coatings

In this paper, a commercial metal-based ceramic coating has been used to prepare the specimen adopting high velocity electric arc spraying (HVAS) technology. The three-point bend tests were proposed to measure the Young's modulus (E) of the coating. A test specimen capable of measuring the complex stress intensity factor of bi-material interfacial crack has been devised. The finite element method (FEM) was conducted to investigate the stress fields in the vicinity of the crack for the bend specimen, and the complex stress intensity factor and its phase angle have been computed through the stress field. The test results of determining E of the coatings showed the Young's modulus increased with the increase of coating thickness. The reason was that the rise of coating thickness resulted in the reduction of porosity in the coatings, so the Young's modulus followed it. The toughness test results showed that crack initiation of the interfacial crack occurred in the range of linear elastic for the whole specimen. In addition, the analysis on validity of K showed that the stress intensity factor was able to be used as the fracture-controlled parameter of interface crack for the specimen geometry and loading pattern in this paper.     

Cooling rate effect on Young's modulus and hardness of a Zr-based metallic glass

It is known that cooling rate can affect the atomic structure and thus may possibly affect the mechanical properties of metallic glasses (MGs). In spite of the considerable efforts on the cooling rate, its effect on the mechanical properties is controversial at the present time. In this study, we present a micromechanical study of the cooling-rate effect on Young's moduli and hardness of the cast bulks and melt-spun ribbons for a Zr₅₅Pd₁₀Cu₂₀Ni₅Al₁₀ metallic glass. Using the classic nanoindentation method, the Young's moduli of the ribbon samples obtained at higher cooling rates were measured which appeared to be much lower than those of the bulk samples. However, through further experiments on slice samples cut from the as-cast bulks and finite-element (FE) analyses, we have clearly demonstrated that the measured difference in elastic moduli was mainly caused by the sample thickness effect in nanoindentation tests. To overcome such a confounding effect, microcompression experiments were performed on the as-cast and as-spun MG samples, respectively. Being consistent with the findings from nanoindentation, the microcompression results showed that the cooling rate, as ranging from ∼10² to ∼10⁶ K/s, essentially has no influence on the Young's modulus and hardness of the metallic glasses.