Rheological properties of a dilute suspension of self-propelled particles

With a detail microscopic model for a self-propelled swimmer, we derive the rheological properties of a dilute suspension of such particles at small Peclet numbers. It is shown that, in addition to the Einstein's like contribution to the effective viscosity, that is proportional to the volume fraction of the swimmers, a contribution due to the activity of self-propelled particles influences the viscosity. As a result of the activity of swimmers, the effective viscosity would be a lower (higher) than the viscosity of the suspending medium when the particles are pushers (pullers). Such activity dependent contribution, will also results to a non-Newtonian behavior of the suspension in the form of normal stress differences

Entropic forces exerted on a rough wall by a grafted semiflexible polymer

We study the entropic force due to a fluctuating semiflexible polymer that is grafted from one end and confined by a rigid and rough wall from the other end. We show how roughness of the wall modifies the entropic force. In addition to the perpendicular force that is present in the case of a flat wall, roughness of the wall adds a lateral component to the force. Both perpendicular and lateral components of the force are examined for different values of amplitude and wavelength of the roughness and at different temperatures. The lateral force is controlled by the local slope of the wall while the perpendicular force is only sensitive to the curvature of the wall. We show that for small compression, the entropic force is increased by increasing the curvature of the confining wall. In addition to the biophysical relevance, the results may also be useful in developing an AFM based experimental technique for probing the roughness of surfaces.Comment: 6 pages, 5 figure

Coupled Sequential Process-Performance Simulation and Multi-Attribute Optimization of Structural Components Considering Manufacturing Effects

Coupling of material, process, and performance models is an important step towards a fully integrated material-process-performance design of structural components. In this research, alternative approaches for introducing the effects of manufacturing and material microstructure in plasticity constitutive models are studied, and a cyberinfrastructure framework is developed for coupled process-performance simulation and optimization of energy absorbing components made of magnesium alloys. The resulting mixed boundary/initial value problem is solved using nonlinear finite element analysis whereas the optimization problem is decomposed into a hierarchical multilevel system and solved using the analytical target cascading methodology. The developed framework is demonstrated on process-performance optimization of a sheetormed, energy-absorbing component using both classical and microstructure-based plasticity models. Sheetorming responses such as springback, thinning, and rupture are modeled and used as manufacturing process attributes whereas weight, mean crush force, and maximum crush force are used as performance attributes. The simulation and optimization results show that the manufacturing effects can have a considerable impact on design of energy absorbing components as well as the optimum values of process and product design variables

Coupled Sequential Process-Performance Simulation and Multi-Attribute Optimization of Structural Components Considering Manufacturing Effects

Coupling of material, process, and performance models is an important step towards a fully integrated material-process-performance design of structural components. In this research, alternative approaches for introducing the effects of manufacturing and material microstructure in plasticity constitutive models are studied, and a cyberinfrastructure framework is developed for coupled process-performance simulation and optimization of energy absorbing components made of magnesium alloys. The resulting mixed boundary/initial value problem is solved using nonlinear finite element analysis whereas the optimization problem is decomposed into a hierarchical multilevel system and solved using the analytical target cascading methodology. The developed framework is demonstrated on process-performance optimization of a sheetormed, energy-absorbing component using both classical and microstructure-based plasticity models. Sheetorming responses such as springback, thinning, and rupture are modeled and used as manufacturing process attributes whereas weight, mean crush force, and maximum crush force are used as performance attributes. The simulation and optimization results show that the manufacturing effects can have a considerable impact on design of energy absorbing components as well as the optimum values of process and product design variables