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Measurement and Prediction of Insertion Force for the Mosquito Fascicle Penetrating into Human Skin

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Journal of Bionic Engineering 2009年第2期6卷 143-152页

作者： X Q Kong C W Wu state key laboratory of Structural analysis for industrial equipment Department of Engineering MechanicsDalian University of Technology

Mosquitoes are exceptional in their ability to pierce into human skin with a natural ultimate painless microneedle, named fascicle. Here the structure of the Aedes albopictus mosquito fascicle is obtained using a Scanning Electron Microscope (SEM), and the whole process of the fascicle inserting into human skin is observed using a high-speed video imaging technique. Direct measurements of the insertion force for mosquito fascicle to penetrate into human skin are reported. Results show that the mosquito uses a very low force (average 18 μN) to penetrate into the skin. This force is at least three orders of magnitude smaller than the reported lowest insertion force for an artificial microneedle with an ultra sharp tip to insert into the human skin. In order to understand the piercing mechanism of mosquito fascicle tip into human multilayer skin tissue, a numerical simulation is conducted to analyze the insertion process using a nonlinear finite element method. A good agreement occurs between the numerical results and the experimental measurements.

关键词： biomimetic microneedle mosquito fascicle mechanics penetration

A Symplectic Method of Numerical Simulation on Local Buckling for Cylindrical Long Shells under Axial Pulse Loads

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Structural Durability & Health Monitoring 2021年第1期15卷 53-67页

作者： Kecheng Li Jianlong Qu Jinqiang Tan Zhanjun Wu Xinsheng Xu state key laboratory of structure analysis for industrial equipment Department of Engineering MechanicsDalian University of TechnologyDalian116024China

In this paper,the local buckling of cylindrical long shells is discussed under axial pulse loads in a Hamiltonian *** this system,critical loads and modes of buckling of shells are reduced to symplectic eigenvalues and eigensolutions *** the symplectic method,the solution of the local buckling of shells can be employed to the expansion series of symplectic eigensolutions in this *** a result,relationships between critical buckling loads and other factors,such as length of pulse load,thickness of shells and circumferential orders,have been *** the same time,symmetric and unsymmetric buckling modes have been ***,numerical results show that modes of post-buckling of shells can be Bamboo node-type,bending type,concave type and so *** in this paper provides analytical supports for ultimate load prediction and buckling failure assessment of cylindrical long shells under local axial pulse loads.

关键词： Hamiltonian system symplectic method local buckling buckling analysis cylindrical long shell axial pulse load

A Gradient-Based Optimization Method for the Design of Layered Phononic Band-Gap Materials

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Acta Mechanica Solida Sinica 2016年第4期29卷 429-443页

作者： Yu Huang Shutian Liu Jian Zhao state key laboratory of Structural analysis for industrial equipment Department of Engineering MechanicsDalian University of Technology

Phononic materials with specific band-gap characteristics at desired frequency ranges are in great demand for vibration and noise isolation, elastic wave filters, and acoustic devices. The attenuation coefficient curve depicts both the frequency range of band gap and the attenuation of elastic wave, where the frequency ranges corresponding to the none-zero attenuation coefficients are band gaps. Therefore, the band-gap characteristics can be achieved through maximizing the attenuation coefficient at the corresponding frequency or within the corresponding frequency range. Because the attenuation coefficient curve is not smooth in the frequency domain, the gradient-based optimization methods cannot be directly used in the design optimization of phononic band-gap materials to achieve the maximum attenuation within the desired frequency range. To overcome this difficulty, the objective of maximizing the attenuation coefficient is transformed into maximizing its Cosine, and in this way, the objective function is smoothed and becomes differentiable. Based on this objective function, a novel gradient-based optimization approach is proposed to open the band gap at a prescribed frequency range and to further maximize the attenuation efficiency of the elastic wave at a specific frequency or within a prescribed frequency range. Numerical results demonstrate the effectiveness of the proposed gradient-based optimization method for enhancing the wave attenuation properties.

关键词： optimization band gap gradient-based optimization two-step optimization approach

Assumed stress quasi-conforming triangular element for couple stress theory

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Acta Mechanica Solida Sinica 2017年第4期30卷 335-344页

作者： Changsheng Wang Xiangkui Zhang Ping Hu School of Automotive Engineering State Key Laboratory of Structural Analysis for Industrial EquipmentDalian University of Technology

In this paper, a 3-node triangular element for couple stress theory is proposed based on the assumed stress quasi-conforming method. The formulation starts from polynomial approx- imation of stresses. Then the stress-function matrix is treated as the weighted function to weaken the strain-displacement equations. Finally, the string-net functions are introduced to calculate strain integration and the stress smooth technique is adopted to improve the stress accuracy. Numerical results show that the proposed new model can pass the Co- 1 patch test with excellent precision, does not exhibit extra zero energy modes and can cap- ture the scale effects of microstructure.

关键词： Quasi-conforming Couple stress theory Fundamental analytical solutions

Flow characteristics of nonspherical granular materials simulated with multi-superquadric elements

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Particuology 2021年第1期19卷 25-36页

作者： Siqiang Wang Shunying Ji state key laboratory of Structural analysis for industrial equipment Dalian University of TechnologyDalian 116023China

The superquadric equation is typically used to mathematically describe nonspherical particles and construct particle shapes with different surface sharpness and aspect ***,nonspherical elements constructed using the superquadric equation are strictly convex,limiting their engineering *** this study,a multi-superquadric model based on a superquadric equation is *** model combines several superquadric elements that can be used to construct concave and convex particle *** tests are performed to examine the applicability of the multi-superquadric *** first involves a comparison of theoretical results for a single spherocylinder impacting a flat *** second involves the formation of a nonspherical granular *** third investigates the effects of the particle shape on the hopper discharge and angle of *** final test evaluates the mixing behaviors of granular materials within a horizontally rotating *** tests demonstrate the applicability of the multi-superquadric approach to nonspherical granular ***,the effects of particle shape on the packing density,discharge rate,angle of repose,and Lacey mixing index are *** indicate that concave particles have a lower packing density,flow rate,and mixing rate and higher angles of repose than convex *** of elements becomes more pronounced for concave particles and results in local cluster structures,thereby enhancing the stability of granular systems and limiting sliding or rotation between nonspherical particles.

关键词： Multi-superquadric approach Nonspherical elements Concave particles Discrete element method Granular materials

An iterative algorithm for analysis of coupled structural-acoustic systems subject to random excitations

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Acta Mechanica Sinica 2012年第2期28卷 458-467页

作者： Guo-Zhong Zhao Gang Chen Zhan Kang state key laboratory of Structural analysis for industrial equipment Dalian University of Technology116024 DalianChina

This paper analyzes the random response of structural-acoustic coupled systems. Most existing works on coupled structural-acoustic analysis are limited to systems under deterministic excitations due to high computational cost required by a random response analysis. To reduce the computational burden involved in the coupled random analysis, an iterative procedure based on the Pseudo excitation method has been developed. It is found that this algorithm has an overwhelming advantage in computing efficiency over traditional methods, as demonstrated by some numerical examples given in this paper.

关键词： Random excitation Coupled structural-acoustic systems Pseudo excitation method

Lateral Vibration Behavior analysis and TLD Vibration Absorption Design of the Soft Yoke Single-Point Mooring System

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China Ocean Engineering 2017年第3期31卷 284-290页

作者： LYU Bai-cheng WU Wen-hua YAO Wei-an DU Yu state key laboratory of Structural analysis for industrial equipment Dalian University of Technology Dalian 116023 China

Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.

关键词： FPSO soft yoke mooring system vibration absorption TLD prototype monitoring system Bohai Bay

A version of Hill's lemma for Cosserat continuum

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Acta Mechanica Sinica 2009年第4期25卷 499-506页

作者： Xikui Li Qipeng Liu The state key laboratory for Structural analysis of industrial equipment Dalian University of Technology 116024 Dalian China

On the basis of Hill＇s lemma for classical Cauchy continuum, a version of Hill＇s lemma for micro-macro homogenization modeling of heterogeneous Cosserat continuum is presented in the flame of average-field theory. The admissible boundary conditions required to prescribe on the representative volume element for the modeling are extracted and discussed to ensure the satisfaction of Hill-Mandel energy condition and the first-order average field theory.

关键词： Hill's lemma Hill-Mandel condition Cosserat continuum Average-field theory RVE boundary conditions

TIME DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD FOR DYNAMIC ANALYSES IN SATURATED PORO-ELASTO-PLASTIC MEDIUM

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Acta Mechanica Sinica 2004年第1期20卷 64-75页

作者：李锡夔姚冬梅 The state key laboratory for Structural analysis of industrial equipment Dalian University of TechnologyDalian 116024China

A time-discontinuous Galerkin finite element method for dynamic analyses in saturated poro-elasto-plastic medium is *** compared with the existing discontinuous Galerkin finite element methods,the distinct feature of the proposed method is that the continuity of the displacement vector at each discrete time instant is automatically ensured,whereas the discontinuity of the velocity vector at the discrete time levels still *** computational cost is then obviously reduced, particularly,for material non-linear *** the implicit and explicit algorithms to solve the derived formulations for material non-linear problems are *** results show a good performance of the present method in eliminating spurious numerical oscillations and providing with much more accurate solutions over the traditional Galerkin finite element method using the Newmark algorithm in the time domain.

关键词： time discontinuous Galerkin FEM saturated porous medium seepage-dynamics coupling wave propagation elasto-plasticity