Showing papers by "Benliang Zhu published in 2022"

Optimum design and thermal modeling for 2D and 3D natural convection problems incorporating level set‐based topology optimization with body‐fitted mesh

Abstract: Passive heat sinks cooled by natural convection are reliable, compact, and low‐noise. They are widely used in telecommunication devices, LEDs, and so forth. This work builds upon the recent advancements in fluid topology optimization (TO) to present a case study of two‐ and three‐dimensional optimum design and thermal modeling for the natural convection problems using a reaction–diffusion equation (RDE)‐based level‐set method. To this end, first, a high‐fidelity thermal‐fluid model is constructed where the full Navier–Stokes equations are strongly coupled with the energy equation through the Boussinesq approximation. We benchmark our simulation solver against the experimental analysis and other numerical analysis methods. Next, we carefully investigate the flow behavior under different Grashof numbers using a fully transient simulation solver. Then, we revisit the RDE‐based level‐set TO methodology and construct an open‐source parallel TO framework. The main findings reveal that using the body‐fitted mesh adaptation, the proposed methodology can capture the explicit fluid–solid boundary and we are free of the continuation approach to penalize the design variable to the binary structure. A moderately large‐scale TO problem with 3.56×106 DOFs can be solved in parallel on a standard multi‐process platform. Our numerical implementation uses FreeFEM for finite element analysis, PETSc for distributed linear algebra, and Mmg for mesh adaptation. For comparison and for accessing our various techniques, a variety of 2D and 3D benchmarks are presented to support these remarkable features.

An Approach for Geometrically Nonlinear Topology Optimization Using Moving Wide-Bézier Components With Constrained Ends

Abstract: Standard moving morphable component (MMC)-based topology optimization methods use free components with explicitly geometrical parameters as design units to obtain the optimal structural topology by moving, deforming, and covering such components. In this study, we intend to present a method for geometrically nonlinear explicit topology optimization using moving wide-Bézier components with constrained ends. Not only can the method efficiently avoid the convergence issues associated with nonlinear structural response analysis, but it can also alleviate the component disconnection issues associated with the standard MMC-based topology optimization methods. The numerical investigations proposed in this work indicate that the proposed method allows us to obtain results in accordance with the current literature with a more stable optimization process. In addition, the proposed method can easily achieve minimum length scale control without adding constraints.

A Novel Force Sensor Based on Optical Fibers Used for Semicircular Flexure Beam Unit

Abstract: In this article, a novel force sensor is designed based on the optical fiber bending loss theory utilizing a structure with periodically corrugated semicircular flexure beam units. The fiber bending loss theory composed of the pure bending loss and the transition loss is related to the curvature radius according to the theoretical analysis. Both the optical working modes and the mechanical properties of the designed sensor are discussed. The output voltage attenuation of different curvature radii is tested and the curvature radius of 6 mm is selected for further experiment. The actual sensing results are acquired using a commercial force sensor. The result shows that the nonlinear errors of the forward and the reverse force applying process are 11.82% and 17.86%, respectively. The sensitivity is 13 mV/N and the precision is 160 mN. The experiment under different temperatures ensures the temperature-insensitive characteristics of the sensor.

A Phase Diagram-Based Stability Design Method for a Symmetrical Origami Waterbomb Base

Abstract: The symmetrical origami Waterbomb(WB) base shows promising applications in engineering due to its considerable mechanical behaviors. As the common phenomenon in actual origami, the stability performance of the WB base has attracted more and more attention. However, there are few studies on graphical design for the stability of WB base. Based on the phase diagram of the intrinsic parameters, this paper proposes an intuitive and synthesized stability design method for the WB base. First, the basic principles are demonstrated by using the Euler-Lagrange functional equation. Besides, the detail of the method is illustrated by two typical WB bases with the given stiffness ratio. Second, according to the proposed design method, the case studies are presented, and the stability behaviors are evaluated by the analytical method and Finite Element Analysis(FEA) simulation. Finally, the prototypes of the case study are designed, the measurement experiment of the stable statuses is carried out. Both FEA simulation and the experimental result can demonstrate the effectiveness of the proposed design method.

A Flexible Hand-Eye and Tool Offset Calibration Approach Using the Least Square Method

Abstract: AbstractHand-eye calibration is the basis of machine vision. The calibration method determines the motion accuracy of the manipulator. In the presented method, the point coordinate in camera frame and robot frame are separately obtained. By stacking the formula, the hand-eye transformation matrix can be calculated using the least square method. Otherwise, a tool offset calibration method is presented and some guidance also of conducting the tool offset calibration experiment is given. Finally, the validity of the proposed method is demonstrated by and experimental studies.KeywordsHand-eye calibrationTool offset calibrationThe least square method

Topology Optimization Method for Designing Compliant Mechanism with Given Constant Force Range

Abstract: This paper presents a modified evolutionary topology optimization method for designing compliant constant force mechanismS (CFMs). CFM is defined as mechanism that can generate constant force in the desired input displacement range, which is known as constant force range. The force variation, i.e. fluctuation of output forces over the constant force range, is a critical parameter, which reflects the stability of the output force. The key idea of the new method is that the design variables are increased or decreased for a certain small value instead of being changed between 0 (or x_{min} ) and 1 in other evolutionary structural optimization (ESO) method. As the CFMs have to experience a large deformation when it works, the influence of the nonlinearity need to be considered. An additive hyperelasticity technique is utilized to alleviate the instability of the finite element analysis, which is introduced by the low stiffness elements. The numerical examples show that the proposed design method can generate CFMs with desired constant force range and aspect ratio. The optimized CFM is manufactured by the 3D printing and the experimental result indicates that it can output an almost constant force(force variation ≤=2%) in a large relative constant force range(56.7%).

Cassini Oval Scanning for High-Speed AFM Imaging

Abstract: Atomic force microscopy (AFM) generally scans the sample surface following a raster pattern signal, which contains discontinuities at turning points and frequencies beyond mechanical bandwidth of scanning stage. Consequently, raster scanning at high speed brings distortions to the resulting image. This paper describes a non-raster scanning method based on Cassini oval pattern. In this method, by adopting Cassini oval pattern, the input control signals of the two axes of scanner are replaced by sinusoid-like smooth signals, thereby reducing the harmonic vibration and improving scanning bandwidth. In addition, details on how to formulate the scanning pattern and generate the Cassini oval signals are analyzed. Experimental results of implementing this method in a commercial AFM and a compensated piezoelectric scanner indicate its feasibility on imaging.