η′-Cu6Sn5 is one of the main components of intermetallic compounds in the solder joint of electronic components. The research on improving its performance will help to solve the problem of increasing ...mechanical properties, electrical conductivity and thermal conductivity of solder joints of electronic devices. In this paper, we use the first-principles method to calculate the effects of 0.57 at.% and 1.14 at.% Zn doped on the Cu1, Cu2, Cu3 and Cu4 positions of η′-Cu6Sn5 on the mechanical and electronic properties of the structure. And we draw a 3D model to express the mechanical anisotropy of the doping system. The calculated results show that doping Zn makes η′-Cu6Sn5 more stable. However, the addition of Zn also reduces the fracture toughness of η′-Cu6Sn5, increases the anisotropy of η′-Cu6Sn5, and weakens the shear resistance of the solder joint of electronic devices.
The effect of solution treatment on the cavitation erosion behavior of a Fe-18Cr-16Mn-2Mo-0.66 N high-nitrogen austenitic stainless steel (HNSS) exposed in distilled water up to 8 h was investigated ...using magnetostrictive cavitation, micro-hardness, mass loss measurements, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the solution treatment slightly decreased the hardness of the HNSS but significantly increased its elasticity. The HNSS with an improved elastic property was shown to have a higher resistance to the absorption of energy produced by cavitation erosion, and hence a higher cavitation erosion resistance. The cavitation erosion damage of the HNSS in distilled water was found to be a deformation-controlled process which limited by the formation and development of plastic deformation during cavitation erosion tests.
•Cavitation erosion behavior of a nickel free high nitrogen stainless steel (HNSS) was investigated.•The effect of solution treatment on cavitation erosion behavior of HNSS was investigated.•Cavitation erosion damage of HNSS is a deformation-controlled process.
Contributions of 15 convex polyhedral particle shapes to the overall elastic properties of particle-reinforced composites are predicted using micromechanical homogenization and direct finite element ...analysis approaches. The micromechanical approach is based on the combination of the stiffness contribution tensor (N-tensor) formalism with Mori–Tanaka and Maxwell homogenization schemes. The second approach involves FEA simulations performed on artificial periodic representative volume elements containing randomly oriented particles of the same shape. The results of the two approaches are in good agreement for volume fractions up to 30%. Applicability of the replacement relation interrelating N-tensors of the particles having the same shape but different elastic constants is investigated and a shape parameter correlated with the accuracy of the relation is proposed. It is concluded that combination of the N-tensor components of the 15 shapes presented for three values of matrix Poisson's ratios with the replacement relation allows extending the results of this paper to matrix/particle material combinations not discussed here.
Finite element models are developed for the in-plane linear elastic constants of a family of honeycombs comprising arrays of cylinders connected by ligaments. Honeycombs having cylinders with 3, 4 ...and 6 ligaments attached to them are considered, with two possible configurations explored for each of the 3- (trichiral and anti-trichiral) and 4- (tetrachiral and anti-tetrachiral) connected systems. Honeycombs for each configuration have been manufactured using rapid prototyping and subsequently characterised for mechanical properties through in-plane uniaxial loading to verify the models. An interesting consequence of the family of ‘chiral’ honeycombs presented here is the ability to produce negative Poisson’s ratio (auxetic) response. The deformation mechanisms responsible for auxetic functionality in such honeycombs are discussed.
•An analytical framework is developed to predict the elastic properties of irregular auxetic structures.•A finite element code is developed to validate the analytical predictions.•The effects of the ...degree of irregularity and geometric parameters on the elastic properties are investigated.
This paper presents an analytical framework with a bottom-up multi-step approach to predict the in-plane mechanical properties including the effective Young’s modulus and Poisson’s ratio in two directions. There are deviations for the analytical predictions with respect to the numerical results because of the simplifications of boundary conditions of the representative unit cell. To remedy the deviations, a modification coefficient is embedded to revise the analytical model. A finite element code for obtaining elastic properties of the irregular auxetic structures is developed to validate the revised analytical model. The good agreement between the revised analytical predictions and numerical results affirms the accuracy of the revised analytical model. It is noticeable that the effects of irregularity on the effective Young’s modulus are more prominent than on the Poisson’s ratio.
The evolution of Young’s modulus and damping is investigated for Czech kaolins in situ via the impulse excitation technique (IET) from room temperature to 1250 and 1400 °C. During heating the ...processes of drying, dehydroxylation, spinel formation, mullitization, silica release and glass melting are clearly discernible. During cooling Young’s modulus increases, exhibiting a flat maximum around 800 °C and a steep decrease below 200 °C when the cristobalite content is high. Differential IET curves are introduced as a new representation of IET results, and damping curves are shown to provide additional information. The phase composition is determined via XRD, including the glass phase. Based on the densities, Young’s moduli and volume fractions of the individual phases, the densities and Young’s moduli of the kaolin-based ceramics are calculated and compared to theoretical predictions, showing that Young’s modulus is nicely predicted by a benchmark relation for partially sintered ceramics with concave pores.
Ceramics from the magnesia-alumina-silica (MAS) system are common products of the ceramic industry. The phase composition of these systems can be rather complex, especially when feldspar is added as ...a flux, and thus attempts to correlate the composition and structure of these ceramics to their properties are quite rare, especially when considerable amounts of glass phase and sapphirine appear after firing. In this paper an attempt is made to correlate, for a talc-kaolin-alumina-feldspar mixture resulting in cordierite-sapphirine ceramics after firing to 1250 °C, the resulting elastic properties (Young’s modulus), as determined via the impulse excitation technique (IET), with the phase composition, determined via X-ray diffraction (XRD). Moreover, it is shown how the evolution of the phase composition and microstructure is reflected in the temperature dependence of Young’s modulus and damping during heating-cooling cycles with maximum temperatures ranging from 1000 to 1250 °C.
Young’s modulus and damping of partially sintered and almost fully dense zirconia ceramics (tetragonal zirconia polycrystals with 3 mol.% yttria), obtained by firing to different temperatures (range ...1000–1400°C), have been determined via impulse excitation, and the evolution of Young’s modulus and damping of partially sintered zirconia with temperature has been monitored from room temperature to 1400°C and back to room temperature. The room-temperature Young’s modulus of the partially sintered materials obeys the Pabst-Gregorová exponential prediction, which is relatively unusual for partially sintered materials. With increasing temperature Young’s modulus decreases, until the original firing temperature is exceeded and sintering (densification) continues, resulting in a steep Young’s modulus increase. During heating and cooling the temperature dependence obeys a master curve with a typical inflection point at approximately 200 °C, the temperature where damping (internal friction) exhibits a maximum. The reasons for this characteristic behavior of doped zirconia are recalled.
Numerical calculations of relative Young’s modulus and thermal conductivity have been performed on computer-generated microstructures of wall-based (closed-cell) and strut-based (open-cell) cellular ...materials (foams) and inverse foams. The results are compared to rigorous upper bounds (Wiener-Paul, Hashin-Shtrikman), model-based predictions (power-law, exponential) and cross-property predictions (CPRs). It is shown that closed-cell foams exhibit higher property values than open-cell and inverse foams, Kelvin foams higher than random foams, and the difference between closed-cell and open-cell foams is larger than that between Kelvin and random foams. While the properties of closed-cell foams are higher than the power-law prediction, those of inverse and open-cell random foams are between the exponential and power-law predictions, and open-cell Kelvin foams follow the Gibson-Ashby power-law prediction for open-cell foams. The Pabst-Gregorová CPR is shown to predict Young’s modulus with accuracy better than ±0.02 relative property units (better than any model-based relation and any other CPR).
Cubic boron nitride (cBN) has been used as a tool material for several decades due to its high hardness and thermal stability. Various binders are commonly added to cBN to synthesise cBN composites ...for better cutting performance. However, most studies have only investigated properties such as hardness and bulk modulus, without comprehensively studying elastic properties through experiments. In this study, the sound velocities and elastic properties of cBN with AlN binder were determined by using the ultrasonic interferometry technique. The bulk and shear moduli with their pressure dependence were determined as B0 = 351 (3) GPa, G0 = 344 (3) GPa, B0′ = 4.32 (4) and G0′ = 1.74 (2) using the finite strain equation-of-state approaches. Elasticity-related thermal properties, such as Debye temperature, Grüneisen parameter, thermal conductivity and coefficient of thermal expansion were also estimated. The results show that the elastic properties of the cBN composite with vol. 8.8% AlN-binder are comparable to the pure cBN compact. Additionally, the thermal conductivity and coefficient of thermal expansion have little effect on cBN composite with AlN binder compared to pure cBN.
PDF
