铸造湿型砂弹性模量测量及粘弹性的研究

弹性模量是一个与型砂性能密切相关的重要物理参数。基于流变学和型砂微变形理论,用所研制的智能化型砂多项性能测试仪对型砂的弹性模量进行了测量研究。评述了型砂弹性模量的测试方法。试验研究了膨润土含量和紧实率对型砂弹性模量值的影响。并对湿型砂的粘弹性本质进行了分析,认为型砂的粘弹性变形主要是粘土膜开尔文体的弹性变形,型砂弹性模量取决于砂粒间粘土膜开尔文体弹性元件的弹性模量,可以将弹性模量作为型砂性能检测参数之一,用于评定型砂的粘弹性性能。     

An innovative tester system for measuring mechanical property of foundry molding sand

1 .Introduction Molding sand ProPerties are elosely relevant to castingquality.During molding Proeess,molding sand ProPertiesean direetly affeet the quality of molds ineluding strength,dimension aeeuracy of mold     

Effect of precipitation on elastic modulus of Al-Zn-Mg-Cu-Li alloys

Al-5.6Zn-3.0Mg- 1.6Cu- 1.1Li-0.24Cr alloys and Al-8.0Zn-2.4Mg-2.4Cu- 1.1Li-0.18Zr altoys （mass fraction, %） were aged by different processes. The microstructure and mechanical properties were determined by transmission electron microscopy（TEM）, tensile test and Vicker＇s hardness test. The experimental results show that the most signified hardening is obtained by double-ageing or multi-ageing for the Al-Zn-Mg-Cu-Li alloys. The yield strength and the elastic modulus of the Li-containing alloys have relationships with ageing processes. The elastic modulus of Li-containing alloys decreases with the increment of precipitates though it is higher than that of Al-Zn-Mg-Cu alloy.     

钢的高温弹性模量E值的测定研究

介绍了根据实际生产需要测试20#钢的高温弹性模量E值的方法和依据的原理、试件的设计、加热温度设定和试验结果。     

Simplified prediction model for elastic modulus of particulate reinforced metal matrix composites

Some structural parameters of the metal matrix composite, including particulate shape and distribution do not influence the elastic modulus. A prediction model for the elastic modulus of particulate reinforced metal matrix Al composite was developed and improved. Expressions of rigidity and flexibility of the rule of mixing were proposed. A five-zone model for elasticity performance calculation of the composite was proposed. The five-zone model is thought to be able to reflect the effects of the MMC interface on elastic modulus of the composite. The model overcomes limitations of the currently-understood rigidity and flexibility of the rule of mixing. The original idea of a five-zone model is to propose particulate/interface interactive zone and matrix/interface interactive zone. By integrating organically with the law of mixing, the new model is found to be capable of predicting the engineering elastic constants of the MMC composite.     

An investigation on the elastic modulus and density of vacuum casted aluminum alloy 2024 containing lithium additions

The elastic modulus and density of (2024+LiX) alloys are investigated. To the alloy of 2024, the weight percentages of lithium added are 2,3, and 4. Melting is carried out in an induction furnace under argon gas protection; casting is done under vacuum. To obtain the maximum strength and hardness, the specimens are solution heat treated under 495 C and quenched in water at room temperature. Then, they are aged naturally and artificially. For the purposes of comparing, some of the specimens are melted under argon gas, but casting is done without vacuum. All the specimens are subjected to tension tests. As a result of this work, the alloys of aluminum that are difficult to manufacture by the known methods are manufactured safely by the vacuum casting method. For 1% of lithium added to the alloy, an increase of 6% in the elastic modulus and 3% decrease in the density are obtained. The specific elastic modulus, E/ρ, ratio increases by about 10% for each 1% addition of lithium.     

A new model to describe effect of plastic deformation on elastic modulus of aluminum alloy

In order to improve the prediction capability of spring-back in aluminum sheet metal forming, the influence of the plastic deformation on elastic modulus is considered when the material undergoes a large plastic deformation. The present work focused on establishing a new model to accurately describe the relation of elastic modulus and plastic deformation. The tensile tests were performed to investigate the influence of plastic deformation on elastic modulus at low strain rate. Two different aluminum sheets were used, AA2024-T3 and LY12-CZ, and the thickness of sheet metals was 1.3 mm and 2.0 mm, respectively. In order to overcome the drawback, which is directly measuring the slope of tension curve to obtain elastic modulus, an extrapolation method was adopted. The proposal macroscopic piecewise sinusoidal function can accurately model the elastic modulus variation.     

粉末冶金工艺制备的钛基复合泡沫材料的压缩性能和弹性模量(英文)

钛基复合泡沫材料由于其优异的生物相容性、抗腐蚀性以及可改的弹性模量,具有极大的生物医用潜力。采用粉末冶金工艺制备嵌入厚壁陶瓷微珠的钛基复合泡沫材料。分析和测试这种钛基复合泡沫材料的微观结构、压缩性能以及弹性模量。结果表明:厚壁陶瓷微珠能够显著提高材料的抗压强度;提高厚壁陶瓷微珠的体积分数,能够使材料的抗压强度获得极大的提高,同时,这种强度的提高并没有引起弹性模量的显著提高。该材料的弹性模量仍然与人体骨骼相近。     

Influence of random shrinkage porosity on equivalent elastic modulus of casting: A statistical and numerical approach

Shrinkage porosity is a type of random distribution defects and exists in most large castings.Different from the periodic symmetry defects or certain distribution defects,shrinkage porosity presents a random "cloud-like" configuration,which brings difficulties in quantifying the effective performance of defected casting.In this paper,the influences of random shrinkage porosity on the equivalent elastic modulus of QT400-18 casting were studied by a numerical statistics approach.An improved random algorithm was applied into the lattice model to simulate the "cloud-like" morphology of shrinkage porosity.Then,a large number of numerical samples containing random levels of shrinkage were generated by the proposed algorithm.The stress concentration factor and equivalent elastic modulus of these numerical samples were calculated.Based on a statistical approach,the effects of shrinkage porosity's distribution characteristics,such as area fraction,shape,and relative location on the casting's equivalent mechanical properties were discussed respectively.It is shown that the approach with randomly distributed defects has better predictive capabilities than traditional methods.The following conclusions can be drawn from the statistical simulations:(1) the effective modulus decreases remarkably if the shrinkage porosity percent is greater than 1.5％;(2) the average Stress Concentration Factor (SCF) produced by shrinkage porosity is about 2.0;(3) the defect's length across the loading direction plays a more important role in the effective modulus than the length along the loading direction;(4) the surface defect perpendicular to loading direction reduces the mean modulus about 1.5％ more than a defect of other position.     

硅化镍对镍硅合金表面气体渗硼层硬度、弹性模量和断裂韧性的影响

在N2?H2?BCl3气氛下对镍硅合金进行两级气体渗硼(910℃、2 h)制备双区硼化层.显微组织由两种具有不同相成分的区域组成.外层区域仅含有硼化镍的混合物(Ni2B,Ni3B),内层区域除了硼化镍还含有硅化镍(Ni2Si,Ni3Si).研究硅化镍的存在对镍基合金表面硼化层力学性能的影响.使用带有Berkovich金...     

Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser-simulated engine heat flux tests. For a 0.25 mm thick ZrO₂-8% Y₂O₃ coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m K to 1.15, 1.19, and 1.5 W/m K after 30 h of testing at surface temperatures of 990, 1100, and 1320 °C, respectively, Hardness and elastic modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and microindentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface and to 7.5 GPa at the ceramic coating surface after 120 h of testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced microporosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various TBC applications.     

声学法评定M50NiL/M50轴承钢的弹性模量

根据固体中的弹性波理论,通过测量M50NiL及M50钢中超声横波、纵波声速及材料密度,评定了M50NiL钢退火、淬火和回火态及M50钢回火态的杨氏模量及泊松比.结果表明,M50NiL钢退火、淬火和回火态的杨氏模量差别很小,泊松比几乎相同;M50钢回火态比M50NiL钢回火态的杨氏模量大2.3％.声学法测得M50NiL钢回火态的杨氏模量与拉伸试验测定值及文献中的参考值相近,表明声学法评估材料弹性模量的方法可行.     

Synthesis of biodegradable Mg-Zn alloy by mechanical alloying: Statistical prediction of elastic modulus and mass loss using fractional factorial design

Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy. The effects of mechanical alloying parameters (i.e., milling time, milling speed, ball-to-powder mass ratio and Zn content) and their interactions were investigated involving 4 numerical factors with 2 replicates, thus 16 runs of two-level fractional factorial design. Results of analysis of variance (ANOVA), regression analysis and R² test indicated good accuracy of the model. The statistical model determined that the elastic modulus of biodegradable Mg-Zn alloy was between 40.18 and 47.88 GPa, which was improved and resembled that of natural bone (30–57 GPa). Corrosion resistance (mass loss of pure Mg, 33.74 mg) was enhanced with addition of 3%–10% Zn (between 9.32 and 15.38 mg). The most significant independent variable was Zn content, and only the interaction of milling time and ball-to-powder mass ratio was significant as P-value was less than 0.05. Interestingly, mechanical properties (represented by elastic modulus) and corrosion resistance (represented by mass loss) of biodegradable Mg-Zn alloy can be statistically predicted according to the developed models.     

Measurements of local elastic moduli by amplitude and phase acoustic microscope

A new method is suggested for the nondestructive measurement of elastic moduli in a localized area, 100–400 μm in diameter, by the complex V(z) curve using an amplitude and phase acoustic microscope. The inverse Fourier transform of the complex V(z) curve contains the reflectance function of a liquid-specimen interface. Therefore, the longitudinal, transverse and Rayleigh wave velocities for the specimen are simultaneously obtained by the inversion of the complex V(z) curve. The elastic moduli for glass obtained from wave velocities by acoustic microscope agree fairly well with those by other methods. The present method is applied to aluminium alloy, and it is shown that this method is useful in measuring the microscopic characteristics in inhomogeneous materials.     

Measurement of dynamic young’s modulus for molybdenum disilicide/pentatitanium trisilicide

The PUCOT (piezoelectric ultrasonic composite oscillator technique) has been used to measure the temperature dependence of dynamic Young’s modulus of molybdenum disilicide (M0S12) reinforced with 10, 30, and 50% volume fraction of pentatitanium trisilicide (Ti₅Si₃). The temperature ranges were room temperature to 600 °C for the 30 and 50 % specimens, and room temperature to 880 °C for the 10 % specimens. In all cases, the values of Young’s modulus decreased linearly with increasing temperature, although at different rates. A graph of Young’s modulus versus composition was used to estimate the value of Young’s modulus for MoSi₂. The value obtained (385 GPa) was in excellent agreement with the value of 388 GPa quoted in the literature.     

ZrCr2 Laves相弹性性质和堆垛层错能的第一性原理计算

采用缀加平面波加局域轨道方法和广义梯度近似对立方C15结构的ZrCr2Laves相金属间化合物的弹性性质，包括弹性常数和弹性模量，以及层错能进行理论计算。结果表明：计算得到的ZrCr2Laves相的弹性性质与实验结果相近，其泊松比和弹性各向异性系数大小说明ZrCr2中原子键合的方向性并不强烈；ZrCr2Laves相的内禀和外禀层错能分别为112mJ／m^2和98mJ／m^2。并计算了层错与位错的弹性交互作用。对ZrCr2Laves相的力学特性和变形机制进行了讨论。     

Dynamic elastic modulus and vibration damping behavior of porous silicon carbide ceramics at elevated temperatures

The piezoelectric ultrasonic composite oscillator technique (PUCOT) has been used to measure the Young’s modulus, E, the mechanical damping, Q ⁻¹, and the strain amplitude, ε, of a sintered silicon carbide containing pores (Hexoloy-SP). The silicon carbide material used in this study had at least 14 vol% porosity. Young’s modulus was found to have a linear temperature dependence from room temperature to 740 °C. The damping was near 10⁻⁴ and was independent of strain amplitude above room temperature.     

A cantilever beam method for evaluating Young’s modulus and Poisson’s ratio of thermal spray coatings

Young’s modulus and Poisson’s ratio for thermal spray coatings are needed to evaluate properties and characteristics of thermal spray coatings such as residual stresses, fracture toughness, and fatigue crack growth rates. It is difficult to evaluate Young’s modulus and Poisson’s ratio of thermal spray coatings be-cause coatings are usually thin and attached to a thicker and much stiffer substrate. Under loading, the substrate restricts the coating from deforming. Since coatings are used while bonded to a substrate, it is desirable to have a procedure to evaluate Young’s modulus and Poisson’s ratio in situ. The cantilever beam method to evaluate the Young’s modulus and Poisson’s ratio of thermal spray coat-ings is presented. The method uses strain gages located on the coating and substrate surfaces. A series of increasing loads is applied to the end of the cantilever beam. The moment at the gaged section is calcu-lated. Using a laminated plate bending theory, the Young’s modulus and Poisson’s ratio are inferred based on a least squares fit of the equilibrium equations. The method is verified by comparing predicted values of Young’s modulus and Poisson’s ratio with reference values from a three-dimensional finite ele-ment analysis of the thermal spray coated cantilever beam. The sensitivity of the method is examined with respect to the accuracy of measured quantities such as strain gage readings, specimen dimensions, ap-plied bending moment, and substrate mechanical properties. The method is applied to evaluate the Young’s modulus and Poisson’s ratio of four thermal spray coatings of industrial importance.     

Experimental investigation of the dynamic elastic modulus and vibration damping in MoSi2-30%Si3N4 as a function of temperature

The dynamic elastic modulus, E, and vibration damping of molybdenum disilicide (MoSi₂) with 30% volume addition of silicon nitride (Si₃N₄) were measured at varying temperatures using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The value of the elastic modulus of the composite was observed to decrease as temperature, T, was increased. The value of dE/dT of MoSi₂ was determined to be −0.03 GPa/K. The vibration damping of MoSi₂-30%Si₃N₄ increased as temperature was increased, with an effective activation energy of 0.076 eV/atom. This was an average over the entire temperature range, but two distinct slopes were observed in the plot of damping versus inverse temperature.     

Preparation of porous Ta-10%Nb alloy scaffold and its in vitro biocompatibility evaluation using MC3T3-E1 cells

A highly porous Ta-10%Nb alloy was successfully prepared for tissue engineering via the methods of the sponge impregnation and sintering techniques. The porous Ta-10%Nb alloy offers the capability of processing a pore size of 300-600 μm, a porosity of (68.0±0.41)%, and open porosity of (93.5±2.6)%. The alloy also shows desirable mechanical properties similar to those of cancellous bone with the elastic modulus and the comprehensive strength of (2.54±0.5) GPa and (83.43±2.5) MPa, respectively. The morphology of the pores in the porous Ta-Nb alloy shows a good interconnected three-dimension (3D) network open cell structure. It is also found that the rat MC3T3-E1 cell can well adhere, grow and proliferate on the porous Ta-Nb alloy. The interaction of the porous alloy on cells is attributed to its desirable pore structure, porosity and the great surface area. The advanced mechanical and biocompatible properties of the porous alloy indicate that this material has promising potential applications in tissue engineering.