Measurement of Young's Modulus and Poisson's Ratio of Thermal Barrier Coatings

In gas turbines, thermal barrier coatings （TBCs） applied by air plasma spraying are widely used to lower the temperature of hot components. To analyze the characteristics of TBCs such as residual stress, bond strength, fracture toughness, and crack propagation ratio, the Young＇s modulus and Poisson＇s ratio are important parameters. For TBC is a brittle and thin film, it is desirable to evaluate those properties while the coatings are bonded to a substrate. An atmospheric plasma spray MCrAIY bond coat and Yttria stabilized zirconia （YSZ） top coat are deposited onto a nickel-base superalloy GH150 substrate. The Young＇s modulus and Poisson＇s ratio are measured by cantilever beam bending with NDI. The method will be developed to test the Young＇ s modulus and Poisson ratio of other multilayer systems.

Analysis of the elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus

The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.

Self-adapting extraction of matrix mineral bulk modulus and verification of fluid substitution

Gassmann＇s equations are commonly used for predicting seismic wave velocity in rock physics research.However the input matrix mineral bulk modulus parameters are not accurate,which greatly influences the prediction reliability.In this paper,combining the Russell fluid factor with the Gassman-Biot-Geertsma equation and introducing the dry-rock Poisson＇s ratio,we propose an effective matrix mineral bulk modulus extraction method.This method can adaptively invert the equivalent matrix mineral bulk modulus to apply the Gassmann equation to fluid substitution of complex carbonate reservoirs and increase the fluid prediction reliability.The verification of the actual material fluid substitution also shows that this method is reliable,efficient,and adaptable.

Topological Design of Microstructures of Materials Containing Multiple Phases of Distinct Poisson’s Ratios

A methodology for achieving the maximum bulk or shear modulus in an elastic composite composed of two isotropic phases with distinct Poisson’s ratios is proposed.A topology optimization algorithm is developed which is capable of finding microstructures with extreme properties very close to theoretical upper bounds.The effective mechanical properties of the designed composite are determined by a numerical homogenization technique.The sensitivities with respect to design variables are derived by simultaneously interpolating Young’smodulus and Poisson’s ratio using different parameters.The so-called solid isotropicmaterial with penalizationmethod is developed to establish the optimization formulation.Maximum bulk or shearmodulus is considered as the objective function,and the volume fraction of constituent phases is taken as constraints.Themethod ofmoving asymptotes is applied to update the design variables.Several 3D numerical examples are presented to demonstrate the effectiveness of the proposed structural optimization method.The effects of key parameters such as Poisson’s ratios and volume fractions of constituent phase on the final designs are investigated.A series of novel microstructures are obtained fromthe proposed approach.It is found that the optimized bulk and shearmoduli of all the studied composites are very close to the Hashin-Shtrikman-Walpole bounds.

实时剪切波弹性成像检测甲状腺结节杨氏模量值及Ratio值鉴别良恶性的临床价值

目的探讨剪切波弹性成像（SWE）检测甲状腺结节杨氏模量值及Ratio值鉴别良恶性的价值。方法选取2014年10月~2015年1月在本院手术治疗的39例甲状腺实性结节患者作为研究对象,术前均行SWE检测,记录甲状腺组织弹性杨氏模量的平均值（E_（mean））、最小值（E_（min））及最大值（E_（max））及以颈前肌为参照的Ratio值,应用ROC曲线分析杨氏模量值（最大值）及Ratio值在甲状腺结节良恶性鉴别中的价值。结果良、恶性结节的杨氏模量值（最大值）及Ratio值比较,差异有统计学意义（P〈0.05）,ROC曲线下面积（AUC）分别为0.90、0.81。结论 SWE可定量测量甲状腺组织的杨氏模量值及Ratio值,获得客观的组织硬度信息,能够为甲状腺疾病的诊断提供更多依据。

硅和镁质量分数对Al-Si-Mg合金机械力学性能参数影响的计算分析

基于第一性原理,利用CASTEP模块,通过虚拟晶体近似的方法建模,采用GGA+PBE泛函关联函数,研究了Al-Si7-Mg X(X=0.1~0.5)、Al-Si X-Mg0.3(X=6~9)合金中的Si、Mg质量分数的变化对机械力学性能参数的影响。研究表明,随着研究组元质量分数的增加,晶格常数有所减小,最大值与最小值相差约0.265%;弹性常数C_(11)、C_(12)、C_(44)满足结构稳定性条件;体积模量B、剪切模量G、杨氏模量E、泊松比u随着A356中Si、Mg质量分数变化而变化;Mg质量分数的变化对剪切模量G、杨氏模量E的影响比Si质量分数的变化更敏感。计算结果与现有实验数据对比表明,计算结果接近实验数据,第一性原理计算Al-Si-Mg合金材料参数可行。

Full-Heusler合金V2MnGa磁性和力学性能

利用第一性原理计算方法,对Full-Heusler合金V 2MnGa整体结构进行了优化,并在最优的晶格常数的基础上计算磁矩,并绘制能带结构图,分析V 2MnGa的磁学性质,以及计算V 2MnGa的力学性能,通过计算合金的体积模量B,Voigte-Reusse-Hill平均剪切模量G、泊松比ν和杨氏模量Y,证明V 2MnGa化合物属于延展性合金。计算V 2MnGa各向异性因子A为2.01,说明该化合物不是弹性各向同性的。结果表明,V 2MnGa合金平衡态晶格常数为5.74(7),属于半金属材料,力学性能表明该合金具有较好的延展性。

FDTD软件中S参数提取方法的讨论与分析

利用基于时域有限差分(FDTD)的电磁场数值仿真软件,如XFDTD等对传输线、天线等结构进行仿真计算时,只能提取激励点的S参数,而在实际应用中,需要提取传输线等结构任意截面的S参数。针对该问题,本文采用坡印亭矢量和驻波比两种方法,通过XFDTD软件输出的稳态场分布获得S参数,并与传输线理论计算所得S参数进行比较,验证了这两种方法的可行性。

基底材料对MoS2的应变场影响

利用有限元法分析对生长在Au、Cu、Al2O3、SiO2、Ni这5种不同基底上的层状MoS2的应变分布进行模拟仿真.研究结果表明:基底材料的泊松比不同会使得基底和MoS2的y方向形变都不相同;基底的杨氏模量不同会使得不同基底底部与二硫化钼(MoS2)顶部的应变差别不同.在膨胀过程中,y方向底端的拉伸应变大于中间的拉伸应变,这会导致基底与顶端应变高于中间的应变.因此,基底材料的杨氏模量和泊松比与MoS2的应变分布密切相关.根据仿真结果可得,由于MoS2在Au和SiO2基底上所受到的应变较小,导致MoS2的顶端和基底底部应变差较大,因此容易造成剥离脱落;而在Al2O3基底上,由于基底材料具有较高的杨氏模量,且与MoS2比较接近,所以MoS2顶端和基底底部呈现的应变差接近.由此可见,在这些材料当中,Al2O3更适合作为MoS2的基底材料.通过研究基底材料的应变场分布,能更好地对纳米材料进行调控,从而改善器件的相关性能.

A methodology to determine the elastic properties of anisotropic rocks from a single uniaxial compression test

This paper introduces a new methodology to measure the elastic constants of transversely isotropic rocks from a single uniaxial compression test.We first give the mathematical proof that a uniaxial compression test provides only four independent strain equations.As a result,the exact determination of all five independent elastic constants from only one test is not possible.An approximate determination of the Young’s moduli and the Poisson’s ratios is however practical and efficient when adding the Saint-Venant relation as the fifth equation.Explicit formulae are then developed to calculate both secant and tangent definitions of the five elastic constants from a minimum of four strain measurements.The results of this new methodology applied on three granitic samples demonstrate a significant stress-induced nonlinear behavior,where the tangent moduli increase by a factor of three to four when the rock is loaded up to 20 MPa.The static elastic constants obtained from the uniaxial compression test are also found to be significantly smaller than the dynamic ones obtained from the ultrasonic measurements.

Size dependency and potential field influence on deriving mechanical properties of carbon nanotubes using molecular dynamics

A thorough understanding on the mechanical properties of carbon nanotube （CNT） is essential in extending the advanced applications of CNT based systems. However, conducting experiments to estimate mechanical properties at this scale is extremely challenging. Therefore, development of mechanistic models to estimate the mechanical properties of CNTs along with the integration of existing continuum mechanics concepts is critically important. This paper presents a comprehensive molecular dynamics simulation study on the size dependency and potential function influence of mechanical properties of CNT. Commonly used reactive bond order （REBO） and adaptive intermolecular reactive bond order （A1REBO） potential functions were considered in this regard. Young＇s modulus and shear modulus of CNTs are derived by integrating classical continuum mechanics concepts with molecular dynamics simulations. The results indicate that the potential function has a significant influence on the estimated mechanical properties of CNTs, and the influence of potential field is much higher when studying the torsional behaviour of CNTs than the tensile behaviour.

氯代磺酚S吸光度比差测量法测定地表水中痕量铝

在pH5.4的乙酸盐缓冲介质中,氯代磺酚S与铝(Ⅲ)反应生成结合比为1比1的配合物,其波峰于649nm,波谷于552nm波长处。分别于649nm及552nm处测得含铝显色液及试剂空白液吸光度,按所给公式计算吸光度比和吸光度比差(△A_r),将此吸光度比差测量法应用于地表水中痕量铝的分光光度法测定。结果表明:铝(Ⅲ)的质量浓度在0.050mg·L^(-1)范围内与△A_r值呈线性关系,其检出限(3s/k)为0.8μg·L^(-1)。用此方法测定了长江水、黄浦江水、太湖水及自来水水样中痕量铝的含量,所得结果与石墨炉原子吸收光谱法测得结果相符,加标回收率在93.0%～107.0%之间。

2022年芦山M_(S)6.1和马尔康M_(S)6.0地震前地震调制比异常分析

扫描2022年芦山M_(S)6.1地震和马尔康M_(S)6.0地震震前不同震级档调制比图像,同时给出震前b值分布图像,结果表明:2次6级地震前震中附近不同震级档调制比均出现高值异常。最小扫描震级越高,调制比扫描结果越稳定清晰,调制比高值异常出现时间越晚,同时最小扫描震级越高,异常范围、幅度也越大,异常与震中位置和发震时间关联性越强。调制比异常的幅度和范围与应力水平有关,2次地震震前震中附近均出现低b值区域,且马尔康M_(S)6.0地震震中附近调制比异常和低b值异常都比芦山M_(S)6.1地震更突出,推断马尔康M_(S)6.0地震孕震区应力水平可能高于芦山M_(S)6.1地震孕震区应力水平。

Experimental study on dynamic elastic parameters of coal samples

Dynamic elastic parameters of coal are closely linked to crack characteristics and are lithology indicators in seismic exploration. This experimental study measured ultrasonic wave velocity of coal samples considering both parallel(90°) and perpendicular(0°) to bedding planes, and then calculated the dynamic elastic parameters(Edand ld) and their anisotropy values(AEdand Ald). The variations of Edand ld,as well as AEdand Aldwere analyzed under various confining stresses. The results show that: Firstly, a critical confining pressure exists, and significant variation in the parameters can be seen below this point and weak variation appears above it. Secondly, a positive correlation exists between Edand the square of P-wave velocity(VP2), and between AEdand the P-wave velocity anisotropy(AEP) as well; however, there is no clear correlation between ldand P-wave velocity(VP). Thirdly, according to the major controlling factors of anisotropy, the coal samples with different Edand ldas well as AEdand Aldcan be divided into two types: one is mainly controlled by bedding and cracks and the other one is mainly controlled by differences of mineral compositions in directions. Consequently, this study can provide theoretical basis for future research on the dynamic elastic parameters and anisotropy of coal.

Effect of Axial Deformation on Elastic Properties of Irregular Honeycomb Structure

Irregular honeycomb structures occur abundantly in nature and in man-made products,and are an active area of research.In this paper,according to the optimization of regular honeycomb structures,two types of irregular honeycomb structures with both positive and negative Poisson’s ratios are presented.The elastic properties of irregular honeycombs with varying structure angles were investigated through a combination of material mechanics and structural mechanics methods,in which the axial deformation of the rods was considered.The numerical results show that axial deformation has a significant influence on the elastic properties of irregular honeycomb structures.The elastic properties of the structure can be considered by the enclosed area of the unit structure,the shape of the unit structure,and the elastic properties of the original materials.The elastic properties considering the axial deformation of rods studied in this study can provide a reference for other scholars.

激光选区熔化制备负泊松比椭圆多孔AlSi10Mg合金性能的数值模拟

将椭圆孔的长/短轴之比、短轴半轴长和初始胞元的边长作为设计参数,提出了一种简化的负泊松比椭圆多孔材料设计方法,通过几何关系建立了材料泊松比与设计参数间的数学模型,基于Gibson-Ashby模型建立了弹性模量与设计参数间的数学模型;通过准静态压缩试验对采用激光选区熔化技术制备的负泊松比椭圆多孔AlSi10Mg合金的泊松比数学模型进行验证,并确定弹性模量数学模型中的常数C。结果表明:采用所建立的泊松比与设计参数数学模型计算得到负泊松比椭圆多孔AlSi10Mg合金的泊松比与试验值相吻合,相对误差在10%~15%;椭圆长/短轴之比、短轴半轴长与泊松比呈负相关,而初始胞元边长与泊松比呈正相关;计算得到泊松比椭圆多孔AlSi10Mg合金弹性模量数学模型中的常数C约为4.123。

Experimental Study for Improving the Toughness of Harden Cement Using Carbon Fiber

Many measures, such as water injection, acid fracturing, thermal recovery, have been taken in the oilfield development. These can easily induce brittle fracture of set cement. Most of all, there are greater potential for fractures in set cement in slim holes. Therefore, it is necessary to improve the toughness of the cement mantle. Results obtained from experiments show that carbon fiber, with a concentration of 0.12%-0.19% in cement and a length of 700 to 1,400μm, plays an important role in improving cement quality. Addition of carbon fiber can improve the bending strength of set cement by up to 30%. At the same time, the increase in fiber concentration can lower the elastic modulus and increase the Poisson＇s ratio of set cement. Thin-section analysis shows that fiber can effectively prevent the propagation of fractures and enhance the plasticity of the matrix and the ability to prevent fracture.

Study of Rock Mechanic Property and Mineralogy Relationship of the Huai Hin Lat Formation, Sap Phlu Basin, Northeastern Thailand: Implications for Understanding of Shale Gas Reservoir Rock

Thailand is lacked of gas that more information of probable (P2) and possible (P3) reserve data including shale gas can be acceptable to prove (P1) reserve data for new gas field. This research had implicated for understanding of unconventional reservoir rock by rock mechanical, micro-CT, and geochemistry analysis of the Huai Hin Lat Formation. The rock mechanical analysis is composed of average young’s modulus, Poisson’s ratio, and compressive strength of 1933.79 MPa, 0.1472, and 52.56 MPa. The average porosity of 6.89% consists of 5.41% and 1.48% of closed and open porosities. The average mineralogical results consist mainly of 57.60% and 42.40% of brittle and ductile minerals indicating more elasticity except Bed 6. The Bed 6 is significantly higher quartz (15%) and brittle minerals (64%) indicating to easier fracture are, therefore, lower compressive strength (25.93 MPa), young’s modulus (1729.10 MPa) and Poisson’s ratio (0.0705). The Beds 3B is slightly higher clay containing slightly higher closed porosity (5.46%) but the Bed 14 is slightly higher brittle mineral indicating to slightly higher open porosity.

Numerical Investigation into the Effect of Air Voids on the Anisotropy of Asphalt Mixtures

The aim of this study is to investigate the asphalt mixture anisotropy of both the modulus and Poisson＇s ratio due to air voids using a discrete element modeling simulation method. Three three-dimensional cubic digital samples of asphalt mixture with different shapes of single air void were built using discrete element software PFC^（3D）. The aggregate gradation, air voids and mastic included in the digital samples were modeled using different contact models, with due consideration of the volumetric fractions of the different phases. Laboratory uniaxial complex modulus test and indirect tensile strength test were conducted to obtain material input parameters for numerical modeling. Simulation of the uniaxial cyclic compressive tests was performed on the three cubic samples loaded in three different directions. Dynamic modulus in three directions and Poisson＇s ratio in six directions were calculated from the compression stress-strain responses. Results show that both the modulus and Poisson＇s ratio are dependent on the preferential orientation of air voids. The anisotropy of the modulus and Poisson＇s ratio increases as the pressure loading on the asphalt mixture increases. Compared to the modulus, Poisson＇s ratio due to air voids has been shown to be more anisotropic. The maximum of Poisson＇s ratio and modulus is shown to be up to 80% and 11% higher than the minimum, respectively.

The Effect of Stem Diameter on the <i>Brassica napus</i>(Type: Canola) (Cultivar: HYHEAR 3) Fiber Quality

A matured canola plant has different types of stems based on the diameter, such as narrow (immature), medium (mature), and wide (over mature). Therefore, this study was focused on investigating the properties of the extracted canola (HYREAR 3) fibers from 3 different diameter of stems (narrow, medium and wide). The physical (average length, aspect ratio, contact angle, and moisture regain) and mechanical (load at break, elongation at break, tensile stress, young’s modulus, and tenacity) properties of fibers were measured. ANOVA showed that stem diameter had effects on all fiber properties except for average length and elongation at break. Fiber diameter also had significant effects on load at break, elongation at break, aspect ratio, tensile stress, and young’s modulus. In corrgram, it was found that tensile stress, young’s modulus, and aspect ratio were negatively correlated to fiber diameter whereas load at break and tenacity were positively associated. Mean values showed that stem diameter had effects on all fiber properties except for average length. The mean values of fiber diameter, load at break, elongation at break, tenacity, and contact angle were highest and the lowest mean values were observed for tensile stress, young’s modulus and aspect ratio in fibers of 7 - 10 mm stems (medium matured), hence found to be less stiff. Moisture regain ability showed that canola fibers isolated from ≥8 mm stem diameter were more hydrophobic whereas contact angle measurement showed relatively more hydrophobic nature of 7 - 10 mm stem fibers. Therefore, this study provided an insightful understanding of the quality of the canola fibers of different stems which will ultimately help to choose the best stem to extract different qualities of fibers for commercial uses.