Book Review “Fabrikant,V.I.Contact and Crack Problems in Linear Theory of Elasticity,Bentham Science Publishers,Sharjah,UAE(2010)”

As suggested by the title, this extensive book is concerned with crack and contact prob- lems in linear elasticity. However, in general, it is intended for a wide audience ranging from engineers to mathematical physicists. Indeed, numerous problems of both academic and tech- nological interest in electro-magnetics, acoustics, solid and fluid dynamics, etc. are actually related to each other and governed by the same mixed boundary value problems from a unified mathematical standpoint

Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.

An Elasto-plastic Contact Solving Method for Two Spheres

The traditional Hertz contact theory has been widely used in solving contact problems.However,it is only applicable to the elastic contact,and cannot truly reflect the contact stress distribution and contact radius in the elasto-plastic contact.In this work,based on the Hertz contact theory,a fast solving method is proposed to calculate the contact stress distribution and contact radius in the elasto-plastic contact between two spheres.It is assumed that the elastic contact only occurs at the outer edge of contact patch and its contact stress distribution satisfies the Hertz contact theory,and the contact stress distribution at the inner edge of contact patch can be superimposed by a constant contact stress and several small ellipsoidal contact stress distributions.Moreover,based on the equivalent relation between the resultant force of contact stress and the normal external load,the contact radius in the elasto-plastic contact can be solved.Finally,an elasto-plastic contact example of two spheres is given based on the power-law hardening material model,and the influences of material parameters,contact radii and normal external loads on the accuracy of the proposed method are discussed by comparing the differences between the numerical results by finite element method and the predicted ones by the proposed method.It is shown that the proposed method can accurately calculate the maximum contact stress and contact radius in the elasto-plastic contact,and the relative errors of both maximum contact stress and contact radius are within±5%.To sum up,the proposed fast solving method can be applied to perform the elasto-plastic contact analysis in engineering practice.

Effect of gauge corner lubrication on wheel/rail non-Hertzian contact and rail surface damage on the curves

Wheel/rail rolling contact is a highly nonlinear issue affected by the complicated operating environment(including adhesion conditions and motion attitude of train and track system),which is a fundamental topic for further insight into wheel/rail tread wear and rolling contact fatigue(RCF).The rail gauge corner lubrication(RGCL)devices have been installed on the metro outer rail to mitigate its wear on the curved tracks.This paper presents an investigation into the influence ofRGCL on wheel/rail nonHertzian contact and rail surface RCF on the curves through numerical analysis.To this end,a metro vehicle-slab track interaction dynamics model is extended,in which an accurate wheel/rail non-Hertzian contact algorithm is implemented.The influence of RGCL on wheel/rail creep,contact stress and adhesion-slip distributions and fatigue damage of rail surface are evaluated.The simulation results show that RGCL can markedly affect wheel/rail contact on the tight curves.It is further suggested that RGCL can reduce rail surface RCF on tight curves through the wheel/rail low-friction interactions.

Reshaping force for deformed casing repairing with hydraulic rolling reshaper and its influencing factors

Hydraulic rolling reshaper is an advanced reshaping tool to solve the problem of casing deformation,which has been widely used in recent years.When it is used for well repair operation,the reshaping force provided by ground devices is generally determined by experience.However,too large reshaping force may destroy the deformed casing,and too small reshaping force may also prolong the construction period and affect the repairing effect.In this paper,based on Hertz contact theory and elastic-plastic theory,combined with the process parameters of shaping,and considering the structural characteristics of the deformed casing and reshaper,we propose a mathematical model for calculating the reshaping force required for repairing deformed casing by hydraulic rolling reshaper.Meanwhile,the finite element model and numerical method of hydraulic rolling reshaper repairing deformed casing are established by using the finite element method,and the reliability of the mathematical model is verified by several examples.On this basis,the control variable method is used to investigate the influence of each parameter on the reshaping force,and the influence degree of each parameter is explored by orthogonal simulation test and Pearson correlation analysis.The research results not only provide an important theoretical basis for the prediction of reshaping force in on-site construction,but also provide a reference for the subsequent improvement of the shaping process.

Mechanical model of nanoparticles for material removal in chemical mechanical polishing process

Chemical mechanical polishing (CMP) is the most effective method for surface planarization in the semiconductor industry. Nanoparticles are significant for material removal and ultra-smooth surface formation. This research investigates the mechanical effects of the material removal in the CMP process. The various contact states of pad, individual particle, and wafer caused by the variations of working conditions and material properties are analyzed. Three different mechanical models for the material removal in the CMP process, i.e., abrasive wear, adhesive wear, and erosive wear are investigated, with a focus on the comparison of the results for different models. The conclusions and methods obtained could potentially contribute to the understanding and evaluation of the CMP process in further work.

Effects of surface texturing on microalgal cell attachment to solid carriers

The objective of this study was to understand the role of surface texturing in microalgal cell attachment to solid surfaces.Two microalgal species,Scenedesmus dimorphus and Nannochloropsis oculata,were studied on solid carriers made of nylon and polycarbonate.Ridge,pillar and groove at micro-scale were engineered on the solid carriers.Cell response to the textured surfaces was separately described by the Cassie and Wenzel models and the contact point theory.Comparison between measured and model-predicted contact angles indicated that the wetting behavior of the textured solid carriers fell into the Wenzel state,which implied that algal cells could fully penetrate into the designed textures,but the adhesion behavior would be dependent on the size and shape of the cell.Experimental results showed that the attachment was preferred when the feature size was close to the diameter of the cell attempting to settle.Larger or smaller feature dimensions had the potential to reduce cellular attachment.The observation was found to qualitatively comply with the contact point theory.