Topology Optimization of Stiffener Layout Design for Box Type Load-Bearing Component under Thermo-Mechanical Coupling

The structure optimization design under thermo-mechanical coupling is a difficult problem in the topology optimization field.An adaptive growth algorithm has become a more effective approach for structural topology optimization.This paper proposed a topology optimization method by an adaptive growth algorithm for the stiffener layout design of box type load-bearing components under thermo-mechanical coupling.Based on the stiffness diffusion theory,both the load stiffness matrix and the heat conduction stiffness matrix of the stiffener are spread at the same time to make sure the stiffener grows freely and obtain an optimal stiffener layout design.Meanwhile,the objectives of optimization are the minimization of strain energy and thermal compliance of the whole structure,and thermo-mechanical coupling is considered.Numerical studies for square shells clearly show the effectiveness of the proposed method for stiffener layout optimization under thermo-mechanical coupling.Finally,the method is applied to optimize the stiffener layout of box type load-bearing component of themachining center.The optimization results show that both the structural deformation and temperature of the load-bearing component with the growth stiffener layout,which are optimized by the adaptive growth algorithm,are less than the stiffener layout of shape‘#’stiffener layout.It provides a new solution approach for stiffener layout optimization design of box type load-bearing components under thermo-mechanical coupling.

Effect of Exogenous Gibberellin on Wheat Seed Germination under Salt Stress

[Objectives]In this experiment,wheat seeds were treated with different concentrations of gibberellin and different concentrations of salt solution to study the change of germination index of wheat seeds.[Methods]The germination rate,germination potential and germination index of wheat seeds were measured by routine methods,and the effect of exogenous gibberellin on germination of wheat seeds under salt stress was observed.[Results]The germination rate,germination potential and germination index of wheat seeds under salt stress were significantly increased after exogenous treatment of 0.25 and 0.50 g/L gibberellin within the range of salt concentration gradient.However,when the concentration of gibberellin was too high,it would inhibit the germination of seeds.[Conclusions]Appropriate concentration of gibberellin can effectively alleviate the stress caused by salt on wheat seed germination.In this experiment,the best concentration of gibberellin to alleviate salt stress was 0.25 g/L.

Skeleton-Based Volumetric Parameterizations for Lattice Structures

Lattice structures with excellent physical properties have attracted great research interest.In this paper,a novel volume parametric modeling method based on the skeleton model is proposed for the construction of threedimensional lattice structures.The skeleton model is divided into three types of nodes.And the corresponding algorithms are utilized to construct diverse types of volume parametric nodes.The unit-cell is assembled with distinct nodes according to the geometric features.The final lattice structure is created by the periodic arrangement of unit-cells.Several different types of volume parametric lattice structures are constructed to prove the stability and applicability of the proposed method.The quality is assessed in terms of the value of the Jacobian matrix.Moreover,the volume parametric lattice structures are tested with the isogeometric analysis to verify the feasibility of integration of modeling and simulation.

Investigation of electrostatically tunable adhesion and instability of flying head slider

The interfacial adhesion between microstructures is inevitable in a micro-electro-mechanical system(e.g.,hard disk drive(HDD)),which may lead to complicated microtribodynamics problems.This research has investigated the effect of surface potential on the interfacial adhesion and microtribodynamics of the head–disk interface(HDI)in an HDD.A dynamic continuum surface force model,where the electrowetting is considered,is proposed to evaluate the interfacial interaction,and then employed into a two-degree-of-freedom(2DOF)model to theoretically analyze the potential influence mechanism on the microtribodynamics.The results confirm that the elimination of potential can effectively repress the adhesion retention,which is further proved by the measured slider response with a laser Doppler vibrometer(LDV).Moreover,the effect of the potential on the adhesion-induced instability is also analyzed through the phase portrait.It tells that the critical stable flying height can be lowered with the elimination of potential.

Parametric Structural Optimization of 2D Complex Shape Based on Isogeometric Analysis

The geometric model and the analysis model can be unified together through the isogeometric analysis method,which has potential to achieve seamless integration of CAD and CAE.Parametric design is a mainstream and successful method in CAD field.This method is not continued in simulation and optimization stage because of the model conversion in conventional optimization method based on the finite element analysis.So integration of the parametric modeling and the structural optimization by using isogeometric analysis is a natural and interesting issue.This paper proposed a method to realize a structural optimization of parametric complex shapes by using isogeometric analysis.By the given feature curves and the constraints,a feature frame model is built.Based on the feature frame model,a parametric representation of complex shape is obtained.After adding some auxiliary curves,the feature frame model is divided into many box-like patches in three dimension or four-sided patches in two dimension.These patches are built into parametric patches by using volume interpolation methods such as Coons method.Based on the parametric patches,isogeometic analysis is applied.Thus,the relationships are constructed among the size parameters,the control points and the physical performance parameters.Then the sensitivity matrix could be derived based on the relationships.The size optimization is carried out in the first stage by taking the size parameters as variables.Based on the result of size optimization,shape optimization with the constraints of stress is carried out in the second stage by taking the control points as variables.Serval planar complex shapes are taken as example to verify our method.The results verify that the parametric modeling and structural optimization can be united together without model conversion.Benefit from this,the optimization design can be executed as a dark box operation without considering the concrete modeling and analysis by input of the sizes,constraints and loads.