The smoothed finite element methods (S-FEM) are a family of methods formulated through carefully designed combinations of the standard FEM and some of the techniques from the meshfree methods. Studies have proven that S-FEM models behave softer than the FEM counterparts using the same mesh structure, often produce more accurate solutions, higher convergence rates, and much less sensitivity to mesh distortion. They work well with triangular or tetrahedral mesh that can be automatically generated, and hence are ideal for automated computations and adaptive analyses. Some S-FEM models can also produce upper bound solution for force driving problems, which is an excellent unique complementary feature to FEM. Because of these attractive properties, S-FEM has been applied to numerous problems in the disciplines of material mechanics, biomechanics, fracture mechanics, plates and shells, dynamics, acoustics, heat transfer and fluid–structure interactions. This paper reviews the developments and applications of the S-FEM in the past ten years. We hope this review can shed light on further theoretical development of S-FEM and more complex practical applications in future.

Smoothed Finite Element Methods (S-FEM): An Overview and Recent Developments

Numerical simulation of two-dimensional sine-Gordon solitons via a local weak meshless technique based on the radial point interpolation method (RPIM)

Smoothed particle hydrodynamics (SPH) for complex fluid flows: Recent developments in methodology and applications

In ocean engineering, the applications are usually related to a free surface which brings so many interesting physical phenomena (e.g. water waves, impacts, splashing jets, etc.). To model these complex free surface flows is a tough and challenging task for most computational fluid dynamics (CFD) solvers which work in the Eulerian framework. As a Lagrangian and meshless method, smoothed particle hydrodynamics (SPH) offers a convenient tracking for different complex boundaries and a straightforward satisfaction for different boundary conditions. Therefore SPH is robust in modeling complex hydrodynamic problems characterized by free surface boundaries, multiphase interfaces or material discontinuities. Along with the rapid development of the SPH theory, related numerical techniques and high-performance computing technologies, SPH has not only attracted much attention in the academic community, but also gradually gained wide applications in industrial circles. This paper is dedicated to a review of the recent developments of SPH method and its typical applications in fluid-structure interactions in ocean engineering. Different numerical techniques for improving numerical accuracy, satisfying different boundary conditions, improving computational efficiency, suppressing pressure fluctuations and preventing the tensile instability, etc., are introduced. In the numerical results, various typical fluid-structure interaction problems or multiphase problems in ocean engineering are described, modeled and validated. The prospective developments of SPH in ocean engineering are also discussed.

Smoothed particle hydrodynamics and its applications in fluid-structure interactions

Meshless Local Petrov--Galerkin (MLPG) method for the unsteady magnetohydrodynamic (MHD) flow through pipe with arbitrary wall conductivity

Low velocity impact behavior and simulation of parametric effect analysis for UHMWPE/LLDPE thermoplastic composite laminates

An algorithm has been developed to identify the position of voids in structures by coupling level set method and finite element method (FEM). The identification problem is transformed into a minimum problem whose objective function is defined as a least square form of displacement error. A perimeter constraint term is also added in the objective function to make the solution well posed. The level set is applied in the present algorithm to represent the position and geometry of the voids. The velocity field of level set function is obtained by analyzing the shape derivative of objective function. FEM based on Euler description is employed for solving the forward problem. The same fixed meshes adopted by the solution of forward problem are used for finite difference computation of the level set function. The procedure of this algorithm has been applied to the voids identification of two-dimensional (2D) and three-dimensional (3D) structures, the examples of single void and multiple voids are considered. The results indicate that the voids in structure can be identified effectively by the present algorithm and the algorithm is also stable to noise.

Identification of Voids in Structures Based on Level Set Method and FEM

Soft robots are a nascent field that aims to provide a safe interaction with humans and better adaptability to unstructured environments. Many tentacle-like one-dimensional soft robots that can mimic the basic motion in nature are developed owing to ease of design and fabrication. To expand the spectrum of soft robots, this paper gives a detailed introduction of a new type of sheet-like two-dimensional soft robot. This soft robot is called soft robotic surface (SRS), which is actuated by pneumatic network bending actuators. An analytical model of the SRS is constructed based on the minimum potential energy method, which considers both its geometry complexity and material nonlinearity. The comparisons among the analytical, experimental, and numerical results demonstrate that the analytical model can accurately predict the SRS deformation. The maximum root mean squared error for the surface morphing is 3.429 mm, which is less than 5% of the maximum displacement for the free end. The effects of the actuating pressure and structural parameter on the SRS deformation are also investigated. The results reveal that the deformation shape of the SRS can be reconfigured by controlling the applied pressure. And the bending angle of the two actuators both decreases with the increase of the width and thickness of the soft surface. The SRS extends the research on soft robots and the developed analytical model also solves the fundamental problem of how to programme the surface morphing of soft robot surfaces. Finally, we fabricate a soft gripper that can grasp object objects with different sizes, shapes, and stiffness, which demonstrates the application of the SRS.

Dean Hu

Papers

Low velocity impact behavior and simulation of parametric effect analysis for UHMWPE/LLDPE thermoplastic composite laminates

Identification of Voids in Structures Based on Level Set Method and FEM

Modeling and analysis of soft robotic surfaces actuated by pneumatic network bending actuators

CFD-DEM simulation of the hydrodynamic filtration performance in balaenid whale filter feeding

Structure Design and Energy Absorption Mechanism of a New Type of Armor Inspired from Armadillos