Experimental and theoretical results for bending of a soft ferromagnetic plate in a transverse magnetic field

Summary.  The results of an experimental and theoretical investigation of the bending behavior of a soft ferromagnetic cantilever beam-plate in a transverse magnetic field are presented. The theoretical model based on a beam-plate theory for magneto-elastic interactions in a soft ferromagnetic material predicts the deflection and strain for several values of the magnetic field and the geometrical parameter. The experiments were conducted on ferritic stainless steel SUS430 in the bore of a superconducting magnet at room temperature. The experiments show the predicted increase in the deflection and strain with increasing magnetic field. The theoretical results agree very well with the experimental data. Received April 15, 2002 Published online: May 8, 2003     

Kinetics of self-repair in inorganic glasses: modeling and experimental verification

A novel concept of self-repairable glass useful as seals in solid oxide fuel cells (SOFCs) is proposed, developed, and used for making metal-glass–ceramic seals for enhancing reliability and life. In this concept, cracks created during SOFC operation are repaired by the crack healing process driven by the viscous flow of the glass. An approach for studying the kinetics of crack healing in glasses responsible for the self-repair is described and used to study the crack healing behavior. The cracks are created by a microindenter, and the progression of healing of cracks thus created on a silicate glass surface is experimentally determined at different annealing temperatures and times. Sequential changes in the crack morphology during thermal healing are also studied to identify the three stages of crack healing process. A crack healing model, based on the relationship among crack length, time, temperature, glass viscosity, and its flow behavior is developed in order to describe and predict the time required for self-repair on a glass surface. The predictions from the developed model is then compared with the experimental data and found to be in good agreement. These results also demonstrated the relative importance of the different stages of crack healing on the overall healing or self-repair behavior.     

圆形阻尼层合板的拓扑优化设计及其实验验证

以阻尼材料的用量为约束,以最大化结构损耗因子为目标,利用有限元方法实现了圆形阻尼层合板的拓扑优化设计。对优化前、后的圆形阻尼层合板进行振动实验,测试结果表明优化后结构的阻尼比是优化前结构的1.3倍。基于结构阻尼比和单位体积结构损耗因子均表示结构件标准化阻尼能力和单调变化相同的特性,以实测的结构阻尼比来表征单位体积结构损耗因子,验证了结构拓扑优化设计的有效性。即优化设计圆形阻尼层合板的构型能够有效地降低阻尼层的用量,提高阻尼层的利用率,增强结构的阻尼特性。     

Acoustic streaming in micromachined flexural plate wave devices: numerical simulation and experimental verification

This paper presents the numerical simulation and experimental validation of acoustic streaming in micromachined flexural plate wave (FPW) devices. Two-dimensional and three-dimensional models of two device types were considered: the classical device with parallel interdigitated electrodes and the focused device with curved electrodes. Influences of different parameters on the time-averaged velocity were investigated. Thermal transport effects of the acoustic streaming were also considered. We observed the amplifying effect of the streaming in the second type numerically and experimentally. To verify simulation results, the method of the particle image velocimetry (PIV) was applied in the experimental investigation.     

In situ stabilization of toxic metals in polluted soils using phosphates: theoretical prediction and experimental verification

The in situ (in place) immobilization of toxic metals, using inexpensive "reactive" amendments, is considered as a simple and cost-effective approach for the treatment of soils, contaminated by the presence of heavy metals, when these soils are difficult or costly to be removed and treated ex situ. Several application studies have demonstrated that the stabilization of contaminated soils and groundwaters by the addition of apatite minerals has the potential to be a successful and widely applicable remediation strategy for the case of Pb, Cd, as well as for other toxic metals, existing in polluted soils. On the other hand, the specific immobilization mechanism(s) of these toxic metals remains rather elusive. The present work involves an interdisciplinary theoretical and experimental approach, designed to gain at the fundamental (molecular) level the understanding of respective mechanisms, considering the immobilization of Pb and Cd by the addition of apatites. The theoretical analysis of stability, regarding the apatite/Pb or apatite/Cd systems and the relevant results of sorption experiments, pointed out two different mechanisms for the immobilization of Pb or Cd by the use of apatites. The possible practical consequences of these findings for the selection/application of natural apatites for the remediation of contaminated soils by the presence of heavy metals have been also discussed.     

Coupled heat and fluid flow model and experimental verification of aluminium plate die casting

Abstract

The present work aims to forecast mould filling, void shape, location and size as well as columnar to equiaxed transition (CET) in commercial pure aluminium casting. A model coupling the momentum equations of the fluid flow and heat transfer equations is presented, in which metallostatic pressure, air gap and oxide layer are considered. Different casting parameters were investigated such as casting configuration by varying the plate thickness from 5 to 20 mm, melt superheat from 40 to 120°C, mould preheat up to 200°C and different pouring heads ranging from 0·3 to 0·6 m. Regarding the microstructure and void formation, the approach based on the Niyama criterion, was considered. The experimental verification of the model was achieved by gravity die casting in the form of a rectangular cavity. Voids inside aluminium plate were investigated by X-ray imaging. Microstructure and CET was investigated microscopically. The supposed model proves its validity for mould filling and in detecting the void features and CET.     

Experimental verification of a theoretical model for erbium-doped fibre ring lasers

A simple theoretical model for erbium-doped fibre ring lasers is presented. This model is experimentally verified by means of the comparison between theoretical values and measurements of efficiency, threshold pump power and output laser power employing a wide set of experimental situations. This model provides semi-analytical equations, which characterise the erbium-doped fibre, determining its absorption and emission spectral coefficients.     

Investigation of the mechanisms governing doxorubicin and irinotecan release from drug-eluting beads: mathematical modeling and experimental verification

Drug-eluting beads (DEBs) are embolising devices in clinical use for the treatment of liver cancer by transarterial chemoembolisation. In this study, release kinetics of doxorubicin (DOX) and irinotecan (IRI) were investigated by experimental evaluations and mathematical modeling, based on Langmuir isotherm and two phenomenological models (Boyd/Bhaskar) developed to determine the actual mechanisms controlling drug release rate. The model was validated through release studies, in particular by assessing how drug loading, ionic strength of the release medium and device swelling during release influence drug release kinetics. Results demonstrated that IRI is released much faster than DOX, and that DEB volume strongly depends upon drug loading and fractional release. This effect was properly taken into account in developing the mathematical model. Experimental results were well fit by numerical simulations, and two different rate-controlling mechanisms were found to govern DOX and IRI delivery.     

Particle modeling of dynamic fragmentation-I: theoretical considerations

This paper series adopts particle modeling (PM) to simulation of dynamic fracture phenomena in homogeneous and heterogeneous materials, such as encountered in comminution processes in the mining industry. This first paper is concerned with the setup of a lattice-type particle model having the same functional form as the molecular dynamics (MD) model (i.e., the Lennard–Jones potential), yet on centimeter length scales. We formulate four conditions to determine four key parameters of the PM model (also of the Lennard–Jones type) from a given MD model. This leads to a number of properties and trends of resulting Young’s modulus in function of these four parameters. We also investigate the effect of volume, at fixed lattice spacing, on the resulting Young modulus. As an application, we use our model to revisit the dynamic fragmentation of a copper plate with a skew slit [J. Phys. Chem. Solids, 50(12) (1989) 1245].     

Compressive response of Kevlar-epoxy composites: experimental verification

The initial misalignment of Kevlar fibres in Kevlar-epoxy composites is quantitatively investigated. This misalignment has been found to be one of the most important factors for determining the compressive response of these composites. A theoretical model, which considers initial fibre misalignment and assumes that the compressive response of Kevlar-epoxy composites is dominated by kink band failure, is in good agreement with experimental results. In addition, photomicrographs of the failure surfaces suggest that kink band formation is the predominant failure mode in this composite system.     

Numerical modeling and experimental verification of mold filling and evolved gas pressure in lost foam casting process

A simple mathematical model is developed to describe a lost foam casting process. Different aspects of the process, such as liquid metal flow, transient heat transfer, foam degradation and gas elimination were incorporated into this numerical model. Fluid velocity, temperature distribution within molten metal and pressure building-up in the mold cavity are predicted as a function of filling time and filling height. The model was verified by comparison of the predicted velocity profiles, temperature fields and back-pressures with the experimental data conducted in this work. Both coated and uncoated foam patterns were used in experimental part of this study. A good agreement between the predictions and the experimental data was found.     

Numerical and experimental verification of a damping model used in DEM

This paper presents a study on the damping ratio \(({\upbeta })\) used in discrete element simulations. Physical experiments are performed by dropping particles from a predetermined height. Two kinds of granular particles, aluminum and steel spheres, are used. The size of these particles are the same. The process of particle depositing under gravity is simulated using the discrete element method. The experimental observation is compared with the numerical result to identify the appropriate \({\upbeta }\). The result indicates that the appropriate damping ratio used in discrete element simulations is between 0.2 and 0.3 %. Various \({\upbeta }\) are then used in the numerical simulations to study the effect of \({\upbeta }\) on the dropping process. The final height of the sample relates to \({\upbeta }\) and the drop height. The effect of \({\upbeta }\) is more profound for small drop height. For greater drop height, the effect of \({\upbeta }\) is negligible.     

Experimental and theoretical study of Rayleigh-Lamb waves in a plate containing a surface-breaking crack

Scattering of Rayleigh-Lamb waves by a normal surface-breaking crack in a plate has been studied both theoretically and experimentally. The two-dimensionality of the far field, generated by a ball impact source, is exploited to characterize the source function using a direct integration technique. The scattering of waves generated by this impact source by the crack is subsequently solved by employing a Green's function integral expression for the scattered field coupled with a finite element representation of the near field. It is shown that theoretical results of plate response, both in frequency and time, are similar to those obtained experimentally. Additionally, implications for practical applications are discussed.     

Absorption spectroscopy in tissue-simulating materials: a theoretical and experimental study of photon paths

A diffusion model of noninvasive absorption spectroscopy was used to determine how the change in signal resulting from a point absorber depends on the position of that absorber relative to the source and detector. This is equivalent to calculating the relative probability that a photon will visit a certain location in tissue before its detection. Experimental mapping of the point-target response in tissue-simulating materials confirmed the accuracy of the model. For steady-state spectroscopy a simple relation was derived between the mean depth visited by detected photons, the source-detector separation, and the optical penetration depth. It was also demonstrated theoretically that combining a pulsed source with time-gated detection provides additional control over the spatial distribution of the photon-visit probability.     

横向常磁场中铁磁圆板的主共振特性与静载效应

针对横向常磁场中铁磁圆板的主共振问题进行研究.基于电磁基本理论,得到薄板在常磁场中所受的磁体力和洛伦兹力,应用哈密顿变分原理,推导出磁场中铁磁圆板磁弹性耦合横向振动微分方程.常磁场中铁磁圆板受到的磁体力为静载荷,根据伽辽金法得到周边夹支边界条件下铁磁圆板在静载荷作用下的初挠度,进一步应用多尺度法对周期载荷作用下的非线性...     

Laser-speckle angular-displacement sensor: theoretical and experimental study

A novel, to our knowledge, method for the measurement of angular displacement for arbitrarily shaped objects is presented in which the angular displacement is perpendicular to the optical axis. The method is based on Fourier-transforming the scattered field from a single laser beam that illuminates the target. The angular distribution of the light field at the target is linearly mapped on a linear image sensor placed in the Fourier plane. Measuring this displacement facilitates the determination of the angular displacement of the target. It is demonstrated both theoretically and experimentally that the angular-displacement sensor is insensitive to object shape and target distance if the linear image sensor is placed in the Fourier plane. A straightforward procedure for positioning the image sensor in the Fourier plane is presented. Any transverse or longitudinal movement of the target will give rise to partial speckle decorrelation, but it will not affect the angular measurement. Furthermore, any change in the illuminating wavelength will not affect the angular measurements. Theoretically and experimentally it is shown that the method has a resolution of 0.3 mdeg ( approximately 5 murad) for small angular displacements, and methods for further improvement in resolution is discussed. No special surface treatment is required for surfaces giving rise to fully developed speckle. The effect of partially developed speckle is considered both theoretically and experimentally.