In this study,the effects of particle shape of rigid sand and soft rubber materials on macro-scale shear response were reasoned based on micro-scale parameters.For this purpose,first,the shape properties of three different sand and two different rubber samples were quantified using image processing techniques,and the contact model parameters were calibrated through physical experiments.The direct shear test was simulated in a two-dimensional discrete element software with realistic particle forms.The soft nature of rubber particles was reflected using body-centered cubic packing with a linear-parallel bond contact model.As a result,coordination number,distribution of contact forces(i.e.,strong contact,and fabric anisotropy),and contact sliding were derived by the numerical analyses.It has been observed that the particle shape leads to distinctive micro-scale responses due to the variations in the stiffness of the contacts.
Geomaterials with inferior hydraulic and strength characteristics often need improvement to enhance their engineering behaviors.Traditional ground improvement techniques require enormous mechanical effort or synthetic chemicals.Sustainable stabilization technique such as microbially induced calcite precipitation(MICP)utilizes bacterial metabolic processes to precipitate cementitious calcium carbonate.The reactive transport of biochemical species in the soil mass initiates the precipitation of biocement during the MICP process.The precipitated biocement alters the hydro-mechanical performance of the soil mass.Usually,the flow,deformation,and transport phenomena regulate the biocementation technique via coupled bio-chemo-hydro-mechanical(BCHM)processes.Among all,one crucial phenomenon controlling the precipitation mechanism is the encapsulation of biomass by calcium carbonate.Biomass encapsulation can potentially reduce the biochemical reaction rate and decelerate biocementation.Laboratory examination of the encapsulation process demands a thorough analysis of associated coupled effects.Despite this,a numerical model can assist in capturing the coupled processes influencing encapsulation during the MICP treatment.However,most numerical models did not consider biochemical reaction rate kinetics accounting for the influence of bacterial encapsulation.Given this,the current study developed a coupled BCHM model to evaluate the effect of encapsulation on the precipitated calcite content using a micro-scale semiempirical relationship.Firstly,the developed BCHM model was verified and validated using numerical and experimental observations of soil column tests.Later,the encapsulation phenomenon was investigated in the soil columns of variable maximum calcite crystal sizes.The results depict altered reaction rates due to the encapsulation phenomenon and an observable change in the precipitated calcite content for each maximum crystal size.Furthermore,the permeability and deformation of the soil mass were affected by the sim
The study is focused on the use of nanofluids in a micro-open tall cavity,which is a type of micro heat exchanger(MHE).The cavity is heated from the bottom sidewall in a sinusoidal pattern,and the effects of four input parameters(Ra,Ha,Kn,and Vf)on heat transfer and irreversibility are investigated using numerical simulations based on Lattice Boltzmann Method(LBM).The findings of the study suggest that the local heat transfer on the bottom sidewall is strongly influenced by Ra and Ha,while the surface distribution of entropy generation is mainly dependent on Kn.The study also shows that the optimization of the magnitude and wavelength of the sinusoidal temperature can improve both local heat transfer and surface distribution of entropy generation.The results of the study provide valuable insights into the design of micro heat exchangers and suggest that the optimization of micro-porous geometries using DOE could lead to increased energy efficiency.The study contributes to our understanding of the complex interactions between input parameters in micro heat exchangers and highlights the importance of considering multiple parameters in the design process.
Understanding the interaction between cyclic stresses and corrosion of magnesium(Mg)and its alloys is increasingly in demand due to the continuous expansion of structural applications of these materials.This review is dedicated to exploring the corrosion-fatigue mechanisms of these materials,with an emphasis on microscale processes,and the possibility of expanding current knowledge on this topic using scanning electrochemical techniques.The interaction between fatigue and corrosion of Mg alloys is analyzed by considering the microstructural aspects(grain size,precipitates,deformation twins),as well as the formation of pits.Furthermore,in the case of coated alloys,the role of coating defects in these phenomena is also described.In this context,the feasibility of using scanning electrochemical microscopy(SECM),scanning vibrating electrode technique(SVET),scanning ion-selective electrode technique(SIET),localized electrochemical impedance spectroscopy(LEIS)and scanning Kelvin probe(SKP)methods to study the corrosion-fatigue interaction of Mg alloys is examined.A comprehensive review of the current literature in this field is presented,and the opportunities and limitations of consolidating the use of these techniques to study the microscale processes involved in Mg corrosion-fatigue are discussed.
Mara Cristina Lopes de OliveiraRejane Maria Pereira da SilvaRicardo M.SoutoRenato Altobelli Antunes