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Multi-flexible-body dynamics (MFBD) and the discrete element method (DEM) are well suited for co-simulation. This paper proposes an efficient, robust, and stable strategy for co-simulating between MFBD solvers and DEM solvers based on the conventional serial staggered (CSS) procedure for co-simulation. A standardized version of this strategy is also proposed that enables the DEM solver to be embedded into the MFBD software. If embedded in this manner, the MFBD software could be extended to create a single MFBD/DEM model, execute a co-simulation, and post process the results in one environment. The proposed strategy is coded into the commercial software RecurDyn. A simple DEM solver is formulated in this paper, embedded into RecurDyn, and numerical examples to demonstrate the feasibility of this proposal are presented.

Conventionally, macro-textured surfaces comprising several hundred micrometer-sized patterns are used to minimize silicone-based breast implant complications, including capsular contracture. However, because of the recent cases of breast implant-associated anaplastic large cell lymphoma from macro-textured implants, there is a strong demand for nano- or micro-textured silicone implants with dimensions smaller than sub-micrometers. Herein, we propose a simple and cost-effective topographical surface modification strategy for silicone-based implants. Several hundred nanometer to sub-micrometer wide groove-type micro-textures were fabricated on a polydimethylsiloxane surface using electrospun polyvinylpyrrolidone fibers as a sacrificial template. The aligned and randomly oriented micro-textures were prepared by controlling the electrospun fiber orientation. In vitro experiments demonstrated that the micro-textured polydimethylsiloxane was cytocompatible and suppressed differentiation of fibroblasts into myofibroblasts. Importantly, the aligned micro-texture promoted the polarization of macrophages into the anti-inflammatory M2 phenotype. Long-term in vivo studies established that the micro-textures potently suppressed various factors affecting foreign body reactions by downregulating profibrotic cytokine gene expression and reducing the fibroblast and myofibroblast counts, the cells playing important roles in the immune response. Thus, the thickness and collagen density of fibrous capsules were decreased, demonstrating that the micro-textured surface effectively inhibited capsular contracture. Although the aligned micro-textures contributed to the polarization of macrophages to the M2 phenotype both in vitro and in vivo, foreign body reaction by both the aligned and randomly oriented micro-textures are similar.

In this work, we propose a robust modeling and analysis technique of the piston-lubrication system considering fluid–structure interaction. The proposed schemes are based on combining the elastohydrodynamic analysis and multi-flexible body dynamics. In particular, multi-flexible body dynamics analysis can offer highly precise numerical results regarding nonlinear deformation of the piston skirt and cylinder bore, which can lead to more accurate results of film thickness for gaps filled with lubricant and of relative velocity of facing surfaces between the piston skirt and the cylinder block. These dynamic analysis results are also used in the elastohydrodynamic analysis to compute the oil film pressure and asperity contact pressure that are used as external forces to evaluate the dynamic motions of the flexible bodies. A series of processes are repeated to accurately predict the lubrication characteristics such as the clearance and oil film pressure. In addition, the Craig–Bampton modal reduction, which is a standard type of component mode synthesis, is employed to accelerate the computational speed. The performance of the proposed modeling schemes implemented in the RecurDyn™ multi-flexible body dynamics environment is demonstrated using a well-established numerical example, and the proposed simulation methods are also verified with the experimental results in a motor cycle engine (gasoline) which has a four cycle, single cylinder, overhead camshaft (OHC), air cooled.

To achieve real-time simulations for flexible multibody dynamics (FMBD) systems, we suggest data-driven modeling based on deep neural networks (DNNs). While a DNN can represent system dynamics accurately, two main factors of FMBD systems require demanding computational costs for training a DNN. One is a fine discretization of flexible bodies, which produces a large number of training data. The other is the nonlinearity of FMBD, which requires train DNN models to have numerous weight and bias parameters. To overcome these difficulties, we propose a data-driven modeling algorithm for training a DNN efficiently that consists of two steps. First, sets of randomly chosen coarse data sequentially train a DNN model. This helps speed up the training process, even for highly parametrized DNNs. At some point, the model no longer improves, and introducing an error correction step increases the performance of the model. The proposed algorithm is easy to employ and utilizes an efficient size of training data while achieving high performance of the DNN as demonstrated by numerical examples.

The design and development of Roll-to-Roll (R2R) system has been mainly executed by the expert’s experience. There are some important issues in the numerical analysis method about a roller path and the control of the R2R system. This study proposes the efficient R2R system analysis methods. The first one is an Approximated Winding Length Estimation (AWLE) algorithm which can calculate the analytic winded length of a workpiece. The winder can be approximated with line and arc segments at this algorithm. As a result, in the numerical model of the R2R system, we can replace the winder characteristics with the AWLE algorithm. The second one is the contact algorithm between workpiece and rollers. This contact algorithm must be stable and fast for precise analysis. The third one is the flexible workpiece model. The workpiece can be modeled by finite elements. By describing the implementation of these important methods, this paper proposes an efficient R2R system analysis method.

When the power transmission systems are designed or improved, an understanding of gear dynamics is essential and very important. Gear systems are not easy to investigate because gear noise has to be carefully controlled. As a result, when designing and developing gear transmission systems, it is very important to grasp the noise and reduce it. Also, it is necessary to make a clear distinction between rattle noises and whine noises. The rattle noise occurs by mainly hitting the tooth, and whine noise occurs by mainly rubbing the tooth in meshing. Therefore, the whine noise is relatively related to high frequency characteristics. Our aim was to find a good way to evaluate whine noise with a numerical approach. When the gear dynamics are investigated to evaluate the whine noise, the dynamic transmission error (DTE) can be utilized. But, it is very difficult to obtain the DTE results by means of not only experimental ways but also numerical calculations. Although multi-body dynamics software has not been able to calculate the DTE practically yet, there is a possibility that the software can get the DTE results. Therefore, we propose a numerical modeling method to obtain the DTE results by using multi-body dynamics software (RecurDyn). To reduce the calculation time and represent flexibility, a rotational joint and force element with the bending stiffness are applied between gear teeth and trunk. Also the numerical results have been compared with the experimental data. The results show a good agreement with the experimental results.

Roll-to-roll (R2R) systems have been mainly designed and developed based on expert experience. There are some important issues in the numerical analysis for R2R systems with the winding web that are included in most general R2R systems. We propose numerical modeling improvements for R2R system analysis to make the numerical methods more efficient. The first is the approximated winding length estimation (AWLE) algorithm, which can calculate the length of the flexible web that is wound around a rotating roller. The winder is approximated with line and arc segments in this algorithm. The second is the contact algorithm between the web and rollers. This contact algorithm has to be stable and fast. This paper proposes an efficient R2R system analysis method.

The analysis of multi-flexible-body dynamics (MFBD) has been an important issue in the area of the computational dynamics. This technique has been developed and improved in RecurDyn solver. This paper reviews the formulation which is applied in the RecurDyn solver. Basically, in order to solve the multi-flexible-body dynamics problem, an incremental finite element formulation using a corotational procedure is used. In particular, in order to solve the rigid and flexible bodies together, a constraint equation between a rigid body and a flexible body is applied, in which a virtual body and a flexible body joint are introduced.

An analysis for operating characteristics of piston lubrication system is performed based on the numerical model in the area of fluid-structure interaction. A numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD) is developed to analyze lubrication characteristics such as oil film thickness and pressure. In particular, elastic deformation of components in piston lubrication system through modal reduction method is reflected on elastohydrodynamic analysis. The oil film pressure evaluated from elastohydrodynamic analysis is used as external force to calculate the elastic deformation of flexible bodies in multi-flexible-body dynamics (MFBD) again. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Moreover, asperity contact effect is also implemented. Finally, a numerical example for the piston lubrication system is also demonstrated.

The surface of poly(dimethylsiloxane) (PDMS) is grafted with poly(acrylic acid) (PAA) layers via surface-initiated photopolymerization to suppress the capsular contracture resulting from a foreign body reaction. Owing to the nature of photo-induced polymerization, various PAA micropatterns can be fabricated using photolithography. Hole and stripe micropatterns ≈100-µm wide and 3-µm thick are grafted onto the PDMS surface without delamination. The incorporation of PAA micropatterns provides not only chemical cues by hydrophilic PAA microdomains but also topographical cues by hole or stripe micropatterns. In vitro studies reveal that a PAA-grafted PDMS surface has a lower proliferation of both macrophages (Raw 264.7) and fibroblasts (NIH 3T3) regardless of the pattern presence. However, PDMS with PAA micropatterns, especially stripe micropatterns, minimizes the aggregation of fibroblasts and their subsequent differentiation into myofibroblasts. An in vivo study also shows that PDMS samples with stripe micropatterns polarized macrophages into anti-inflammatory M2 macrophages and most effectively inhibits capsular contracture, which is demonstrated by investigation of inflammation score, transforming-growth-factor-β expression, number of macrophages, and myofibroblasts as well as the collagen density and capsule thickness.

The analysis of multi-flexible-body dynamics (MFBD) has been an important issue in the area of computational dynamics. Also, dynamic analysis of many mechanical systems often involves contacts among rigid and flexible bodies. But, until now, the contact analysis in the multi-flexible-body dynamics has still remains a big, challenging area. In order to simulate the contact phenomena, this study uses a compliant contact force model based on the Hertzian contact theory. When generating the contact force with a compliant contact force model, a penetration depth and a contact reference frame (a contact point and normal and tangent directions) must be determined from the geometrical information of the rigid and flexible body surfaces. For robust and efficient general purpose contact algorithms, the contact algorithms are divided into four main parts which are a surface representation, a pre-search, and a detailed search and a contact force generation. In the surface representation part, we propose a general surface representation method which can be used for complex rigid and flexible bodies. In the pre-search, the algorithm performs collision detection and composes the input data sets for the detailed search. Then, in the detailed search, the penetration depth and contact reference frame are calculated in order to generate the contact force by using the compliant contact force model. Finally, in the contact force generation part, we evaluate the contact force and the Jacobian matrix which can be used for the implicit integrator. The new general purpose contact algorithm is called GGEOM (General GEOMetry) contact, because it can use general rigid and flexible geometries.

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value, even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper, the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved.

The Absolute Nodal Coordinate Formulation (ANCF) is a relatively new nonlinear finite element type that uses Hermite splines for shape functions. In this investigation, the ANCF is examined as a possible tool for use in modeling the media in flexible media transport systems, such as printers, copy machines, and roll-to-roll systems. However, it is demonstrated using an example of a thin plate-type ANCF finite element that these elements can suffer from significant membrane locking, which can be problematic for paper or paper-like media. One source of this locking is identified to be a property of all parametric curves that are composed of polynomials. The property is that for parametric polynomial curves, changes in the state of curvature of the curve cause changes in the distribution of points along the curve. This property is labeled Curve-Induced Distortion (CID) by the authors of this paper. CID can cause axial and membrane strain distortion in elements, causing them to be overly stiff. A new solution method is proposed to directly counteract CID in finite elements that use cubic Hermite curves for shape functions, specifically for modeling problems in which bending occurs primarily around one axis, such as paper in printing and media transport machinery. This method is labeled Flat-Mapped Extension Modeling (FMEM). FMEM is a mixed field method that uses a 1D Hermite polynomial kinematically linked to the 3D Hermite curve to represent the axial displacement field. FMEM significantly reduces the effect of CID in the ANCF element tested here. This investigation demonstrates using a single ANCF plate element type that the ANCF’s accuracy can be significantly improved by FMEM with only a small increase in computational cost. It is shown with this plate-element example that without correcting CID, the ANCF element tested is computationally much slower than contemporary methods like the co-rotational formulation for similar accuracy. But with FMEM, the ANCF is significantly faster than the co-rotational formulation for similar accuracy.

In this paper we propose a new method for the recognition of facial expressions from single image frame that uses combination of appearance and geometric features with support vector machines classification. In general, appearance features for the recognition of facial expressions are computed by dividing face region into regular grid (holistic representation). But, in this paper we extracted region specific appearance features by dividing whole face region into domain specific local regions. Geometric features are also extracted from corresponding domain specific regions. The results of facial expressions recognition using features from domain specific regions are also compared with the results obtained using holistic representation. The performance of the proposed facial expression recognition system has been validated on two public databases: CK+ and MUG facial expression dataset.

This study proposes a systematic extension of a multiflexible-body dynamics (MFBD) formulation that is based on a recursive formulation for rigid body dynamics. It is extended to include nonlinear plastic and hyperelastic material models for the flexible bodies. The flexible bodies in the existing MFBD formulation use a finite element formulation based on corotational elements. The rigid bodies and flexible bodies are coupled using the method of Lagrange multipliers. The extensions to add plasticity and hyperelasticity are outlined. A solid, brick-type element and a shell element are adapted from the literature for use with the plastic material, and a constant volume constraint is introduced to enforce the approximation of incompressibility with the hyperelastic materials. A brief overview of the MFBD formulation and the details required to extend the formulation to incorporate these nonlinear material models are presented. Numerical examples are presented to demonstrate the feasibility of the model.

The contact analysis of multi-flexible-body dynamics (MFBD) has been an important issue in the area of computational dynamics because the realistic dynamic analysis of many mechanical systems includes the contacts among rigid and flexible bodies. But, until now, the contact analysis in the multi-flexible-body dynamics has still remained as a big, challenging area. Especially, the most of contact algorithms have been developed based on the facetted triangles. As a result, the contact force based on the facetted surface was not accurate and smooth because the geometrical error is already included in the contact surface representation stage. This kind of error can be very important in the precise mechanism such as gear contact or cam-valve contact problems. In order to resolve this problem, this study suggests a cubic spline surface representation method and related contact algorithms. The proposed contact algorithms are using the compliant contact force model based on the Hertzian contact theory. In order to evaluate the smooth contact force, the penetration depth and contact normal directions are evaluated by using the cubic spline surface interpolation. Also, for the robust and efficient contact algorithm development, the contact algorithms are divided into four main parts which are a surface representation, a pre-search, a detailed search and a contact force generation. In the surface representation part, we propose a smooth surface representation method which can be used for smooth rigid and flexible bodies. In the pre-search, the algorithm performs collision detection and composes the expected contact pairs for the detailed search. In the detailed search, the penetration depth and contact reference frame are calculated with the cubic spline surface interpolation in order to generate the accurate and smooth contact force. Finally in the contact force generation part, we evaluate the contact force and Jacobian matrix for the implicit time integrator.

In this paper, one method for the process of CAE software’s development is proposed. In order to develop CAE software efficiently and quickly 3 concepts are built, Engineering Application Framework, Plug-in Toolkit and Integration Platform. These concepts are based on object-oriented idea and include CAE’s characteristics. Engineering Application Framework is for the basic foundation of CAE software. Plug-in toolkit is for the fast and easy extension of CAE software. And integration platform will solve the problem of control and managing according to the various extensions. The theory and operating process of each concept is investigated.Copyright © 2005 by ASME

In this paper, we introduce a machine learning-based simulation framework of general-purpose multibody dynamics (MBD). The aim of the framework is to construct a well-trained meta-model of MBD systems, based on a deep neural network (DNN). Since the main advantage of the meta-model is the enhancement of computational efficiency in returning solutions, the modeling would be beneficial for solving highly complex MBD problems in a short time. Furthermore, for dynamics problems, not only the accuracy but also the smoothness in time of motion solutions, such as displacement, velocity, and acceleration, are essential aspects to consider. We analyze and discuss the influence of training data structures on both aspects of solutions. As a result of the introduced approach, the meta-model provides motion estimation of system dynamics without solving an analytical equation of motion or a numerical solver. Numerical tests demonstrate the performance of the proposed meta-modeling for representing several MBD systems.