Generalized differential quadrature for frequency of rotating multilayered conical shell

10.1061/(ASCE)0733-9399(2000)126:11(1156)Journal of Engineering Mechanics126111156-1162JENM

Functionally graded shells subjected to underwater shock

This paper deals with the problem of functionally graded (FG) cylindrical shells subjected to underwater shock. A computational approach to predict the dynamic response of the FG cylindrical shells to underwater shock is presented. The effective material properties of functionally graded materials (FGMs) for the cylindrical shells are assumed to vary continuously through the shell thickness and are graded in the shell thickness direction according to a volume fraction power law distribution. Based on Doubly Asymptotic Approximation (DAA) method, the fluid-structure interaction equation for a submerged structure is derived, in which the constitutive relation for functional graded material is implemented. The coupled fluid-structure equations, relating structure response to fluid impulsive loading, are solved using coupled finite-element and boundary-element codes. The computational procedure for the prediction of transient response of the FG graded cylindrical shells subjected to underwater shock is described, with a discussion of the results.Published versio

Development of a novel fatigue damage model with AM effects for life prediction of commonly-used alloys in aerospace

In the aerospace industry, more and more alloy parts with requirements of complex geometry and light weight are fabricated by additive manufacturing (AM) process, which has significant influence on their high-cycle fatigue properties. However, so far no work has been done to predict fatigue life of AM alloy parts through the damage mechanics based method. In this paper, a novel fatigue damage model with AM effects is proposed to address the issue, in which laser power, scan speed, hatch spacing and powder layer thickness are integrated in terms of the volumetric energy density, and the material parameters are calibrated with reported experimental data for the damage-coupled elastoplastic constitutive equations. After that, a good agreement is achieved numerically between the present theoretical model and published experimental results. Then the three most commonly-used alloy (SS316L, Ti6Al4V and AlSi10Mg) parts fabricated by AM process are studied in detail to investigate their several important characteristics, including the variation of fatigue life with the volumetric energy density, the variation of damage evolution rate with fatigue life subject to different volumetric energy densities, the relations between Young's modulus and fatigue life, and so on. Finally, several recommendations are presented for selection of the commonly-used AM alloy parts in aerospace, based on the engineering requirements and economy consideration.Accepted versio

Optimization of deformable magnetic-sensitive hydrogel-based targeting system in suspension fluid for site-specific drug delivery

For optimization of the targeting performance of the magnetic hydrogel subject to the magneto-chemo-hydro-mechanical coupled stimuli, a multiphysics model for a suspension fluid flow in a blood vessel is developed, in which a deformable magnetic-sensitive hydrogel-based drug targeting system moves with fluid. In this model, the fluid-structure interaction of the movable and deformable magnetic hydrogel with surrounding fluid flow is characterized through the fully coupled arbitrary Lagrangian-Eulerian algorithm. Moreover, the four physicochemical responsive mechanisms are considered, including hydrogel magnetization, solvent diffusion, fluid flow, and nonlinear large deformation. After the present model is examined by the experimental data in open literature, the transient behaviors of the motion and deformation of the magnetic hydrogel are investigated in suspension flow. It is found that the higher flow velocity and/or the larger hydrogel size accelerate the movement of the hydrogel, while the smaller hydrogel size contributes to the larger swelling ratio. Furthermore, the performance of the magnetic targeting system is optimized for delivering the drug-loaded hydrogel to the desired site by tuning the maximum magnetic field strength, the maximum inlet flow velocity, and the magnet position. Therefore, it is confirmed that the present optimizable magnetic hydrogel-based drug targeting system via the multiphysics model may provide a promising efficient platform for site-specific drug delivery

Modeling of a fast-response magnetic-sensitive hydrogel for dynamic control of microfluidic flow

A magnetic-sensitive hydrogel-based microfluidic system is designed via a magneto-chemo-hydro-mechanical model for replicating various physiological and pathological conditions in the human body, by which the desired flow patterns can be generated in real time due to the fast-response deformation of the magnetic hydrogel. In the model, the fluid-structure interaction is characterized between the deformable magnetic hydrogel and surrounding fluid flow through the fully coupled arbitrary Lagrangian-Eulerian (ALE) method. Moreover, the physicochemical mechanisms including hydrogel magnetization, fluid diffusion, fluid flow, and hydrogel large deformation are characterized. After validation of the present model with both the finite difference and experimental results in the open literature, the transient behavior of the magnetic hydrogel is investigated, and the results show that the response time for the magnetic hydrogel is improved significantly in a uniform magnetic field compared with that of a hydrogel without the magnetic effect. Furthermore, various patterns of pulsatile flow are generated for mimicking the cell physiological microenvironment experienced by bone marrow stromal cells, and also for the pathological condition at the femoral artery during diastole and systole, respectively. Therefore, the present magnetic-sensitive hydrogel-based microfluidic system via the multiphysics model may provide a relevant humanized manipulation platform to investigate cell behavior and function through microfluidic chips.Accepted versio

Effects of salt- and oxygen-coupled stimuli on the reactive behaviors of hemoglobin-loaded polymeric membranes

A high-performance polymeric membrane is usually associated with excellent electrochemical andmechanical behaviors. Thereby, this paper examines the effects of salt- and oxygen-coupled stimuli onreactive behaviors of hemoglobin-loaded polymeric membranes with varying initialfixed charge den-sities. For capturing the coupled chemo-electro-mechanical responses of the membrane, a multiphysicsmodel is mathematically formulated and then experimentally validated. The numericalfinding unveilsthat the Donnan potential strength of polyacidic membrane decreases with increase of ambient oxygenlevel, whereas the Donnan potential of present polyampholytic membrane, at neutral pH conditions, isalmost invariant towards changes of environmental salt concentration. When the environmental saltconcentration is smaller than the initialfixed charge concentration of the membrane, the surface con-ductivity of the system is enhanced bi-linearly with increase of the salt concentration due to weakenedDonnan potential strength acting over the polymer-solution, while the ion transport in the system isdominantly diffusion-governed if environmental salt concentration is greater than the initialfixed chargeconcentration of the membrane. Ultimately, thesefindings can be employed to systematically design andoptimize the dual salt-oxygen reactive hemoglobin-loaded polymeric membrane.Nanyang Technological UniversityAccepted versionThe authors gratefully acknowledge the financial support from Nanyang Technological University through the project (No:M4081151.050) and NTU Research Scholarships

Strip element method for characterization of flaws in sandwich plates

JSME International Journal, Series A: Mechanics and Material Engineering384554-562JSSM

Modeling the dual oxygen- and pH-stimulated response of hemoglobin-loaded polyampholyte hydrogel for oxygen-pH coupled biosensor platform

This paper presents the dual oxygen- and pH-stimulated responsive performances of hemoglobin-loaded polyampholyte hydrogel, where a multiphysics model is formulated for the numerical characterization of the hydrogel, incorporating electrical interactions of the fixed-mobile charge groups and chemical reactions of the hemoglobin-oxygen complexes. A developed constitutive relation is integrated into the model to capture bioactivity of the immobilized hemoglobin as a function of ambient oxygen coupled with environmental pH. After examination with published experimental observations, it is concluded that the multiphysics model can accurately characterize both neonatal hemoglobin oxygen saturation and pH-driven volume transition behaviors of hemoglobin-loaded hydrogel. The results show that the swelling deformation of polyampholyte hydrogel changes in a bowl-shaped like pattern with increase of environmental pH value, whereas the rate of oxygen loaded into the hydrogel enlarges linearly with increase of physiological oxygen level from 1 to 30 mmHg. Consequently, these findings demonstrate that hemoglobin-loaded polyampholyte hydrogel could provide an innovative avenue for sensing and storing both bioactive oxygen and hydrogen solutes in biological fluids, pointing to a novel material platform for developing oxygen-pH stimuli coupled responsive biosensor, as well as oxygen- and/or pH-driven bio-actuators.Accepted versio

Statistics of flaw interaction in brittle materials

Journal of the American Ceramic Society742352-357JACT