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This study proposes a new wall boundary condition for the grid-stamping on a polygon (G-StoP) model, which enables a simpler and more efficient handling of boundary surfaces of arbitrarily complex-shaped bodies represented using polygons (or meshes). For example, computer-aided design surface data can be used to analyze flow using a particle-based fluid-solver moving particle semi-implicit method. For coupling simulations of fluid–multibody dynamics, the Pusan-National-University-modified MPS method is improved, and the coupling analysis is performed using RecurDyn, a commercial software package for multibody (or flexible multibody) dynamics. To confirm the applicability of the developed G-StoP model, hydrostatic pressure simulations are conducted in a rectangular tank at various corner angles. Then, the hydrostatic pressure results are compared with previously proposed polygonal wall boundary model results and theoretical solutions. That is, in the case with a corner angle of 30°, it was confirmed that the relative error to the experiment of the polygon model was 11.3%, while that of the G-StoP model was 1.3%. This demonstrates that the proposed G-StoP model is exceptional for numerical stability and robustness even when it is difficult to secure information on neighboring particles as the corner angle of the object becomes small. In addition, the G-StoP model was applied to dam breaking, subaerial landslide tsunami, and wine sloshing problems, and its accuracy and applicability were tested through comparison with experimental and other simulation results. As a result, it was shown that the present simulation results were much closer to the experiments than other simulations. [ABSTRACT FROM AUTHOR]

Multibody dynamic (MBD) models are required to be accurate if they are to be used with confidence. To determine the overall accuracy of an agricultural machine MBD model, the model needs to be validated through proper experimental design principles and error analysis. At a high-level, the main methodology concepts for the experimental design involve categorizing dynamic subsystems, creating a data acquisition plan, determining and completing experimental testing, and pre-processing of physical and virtual time series datasets. This paper provides a methodology and example validation process for an MBD model of an agricultural self-propelled sprayer. As part of the experimental testing, a tip test revealed that the vertical center of gravity of the MBD model resulted in a 2.8% error from the physical machine. Furthermore, to summarize simulation model performance against physical data, three error quantification metrics for time-series data comparison are proposed: (1) correlation coefficient, (2) two-sample t-test and two-sample F-test, and (3) standard deviation of absolute error. For determining whether there is an acceptable level of agreement, this study proposes that the correlation coefficient should be greater than 0.7, the two-sample t-test and two-sample F-test should both pass (but with special consideration of the resulting confidence intervals if they fail), and that the standard deviation of absolute error should be less than 25% of the standard deviation of physical time series data. These error metrics, together with their defined sets of agreement criteria, resulted in detecting where the self-propelled sprayer system was experiencing validation issues and eventually the overall practical validation of the MBD model. [ABSTRACT FROM AUTHOR]

Rarity of soft tissue preservation, including of articular cartilage, in the fossil record hinders creation of biologically-realistic mechanical models. Previous studies of articular cartilage in extant taxa have documented important aspects of cartilage shapes and thicknesses, but these insights remain generalized and have yet to see systematic implementation in biomechanical modeling. Herein, we present a new method for modeling joints that allows for testing of hypotheses about articular cartilage morphology in extinct taxa. Our case study examines the left elbow joint of the sauropod dinosaur Dreadnoughtus schrani using articular cartilage reconstructions constrained by extant phylogenetic bracketing (EPB). EPB investigations of alligator and chicken articular cartilage revealed the presence of a spherical anterior projection of cartilage on the distal humerus which articulates with the radius during flexion. Importantly, this shape does not directly mirror the underlying bone. Using multibody dynamic models created in Adams™ without a priori restrictions on joint degrees of freedom, we simulated the effects of three alternative cartilage reconstructions based on these EPB findings which differ in mediolateral placement of a cartilage sphere and its anteroposterior thickness, encompassing a range of possibilities for the condition in Dreadnoughtus. Bone kinematics and contact area (calculated in Geomagic®) were tracked. Additionally, we modeled the elbow of an alligator and turkey using the same methodology and compared the results to XROMM (X-ray Reconstruction of Moving Morphology) analysis of the same limbs. Each model produced distinct results but were generally similar supporting our modeling methodology. Based on these findings, we predict that Dreadnoughtus, and presumably other extinct archosaurs, had a spherical projection of cartilage on the anterior face of the distal end of the humerus for articulation with the radius. Though many valuable insights have been gained by existing modeling methodologies, we chose a different approach that focused on joint contact surfaces. Moreover, applying our methods within a quantitative hypothesis-testing framework can advance the field of paleobiology by testing hypotheses relating shape and kinematics that are not possible with prescribed joint motions.

This study proposes a new wall boundary condition for the grid-stamping on a polygon (G-StoP) model, which enables a simpler and more efficient handling of boundary surfaces of arbitrarily complex-shaped bodies represented using polygons (or meshes). For example, computer-aided design surface data can be used to analyze flow using a particle-based fluid-solver moving particle semi-implicit method. For coupling simulations of fluid–multibody dynamics, the Pusan-National-University-modified MPS method is improved, and the coupling analysis is performed using RecurDyn, a commercial software package for multibody (or flexible multibody) dynamics. To confirm the applicability of the developed G-StoP model, hydrostatic pressure simulations are conducted in a rectangular tank at various corner angles. Then, the hydrostatic pressure results are compared with previously proposed polygonal wall boundary model results and theoretical solutions. That is, in the case with a corner angle of 30°, it was confirmed that the relative error to the experiment of the polygon model was 11.3%, while that of the G-StoP model was 1.3%. This demonstrates that the proposed G-StoP model is exceptional for numerical stability and robustness even when it is difficult to secure information on neighboring particles as the corner angle of the object becomes small. In addition, the G-StoP model was applied to dam breaking, subaerial landslide tsunami, and wine sloshing problems, and its accuracy and applicability were tested through comparison with experimental and other simulation results. As a result, it was shown that the present simulation results were much closer to the experiments than other simulations.

In this paper, the CFD-MBD numerical coupled model has been proposed for an accurate evaluation of the behavior of the partially filled railway tank wagon. The vibration response of the wagon has been obtained by the fourth-order Runge-Kutta method based on the threedimensional multibody dynamic (MBD) model with 19 degrees of freedom comprising car-body, two bogies, and four wheel-sets. The model of transient fluid sloshing inside the tank has been analyzed using the computational fluid dynamics (CFD) method combined with the volume of fluid (VOF) technique for solving the Navier-Stokes equations and tracing the fluid free surface, respectively. Validation of the numerical results has been carried out using experimental data. Then, the simultaneous interaction of the transient fluid slosh and the wagon dynamics has been considered through the development of the numerical process of coupling CFD and MBD models. The dynamic characteristics of a partially filled tank wagon have been derived in braking conditions using parametric study on the filled-volume, tank cross-section shape, and fluid viscosity. The results indicate that the filled-volume increase decreases the amplitude of the fluid’s center of gravity coordinate. The lowest fluid slosh in the different filled-volumes has been related to the modified-oval cross-section. The fluid viscosity has a slight effect on the longitudinal fluid slosh force and the stopping distance of the railway tank wagon. [ABSTRACT FROM AUTHOR]

An important design challenge of modern vehicles is mass reduction. Hence in many cases, mechanical design of vehicle components covers different optimization processes. One important structural optimization technique which is highly utilised in weight reduction applications is the topology optimization. This paper contains a multi-stage optimization based on the topology and design optimizations. During this study, the mechanical design of a rear axle-chassis connection bracket is achieved. First of all, the design load of the bracket was determined through a multibody dynamics analysis. This load case was determined among various driving conditions and the most critical load case was indicated as the design load of the bracket. This process was executed by using Adams/Car? software. Subsequently, a design volume for the bracket was decided, which specifies the domain of topology optimization that will be employed later on. The determination of the design domain was made by considering the structural position of the design component, the neighbor components of the rear axle and the chassis. In this manner, the basic shape and dimensions of the bracket were created. The unnecessary volume of the draft design, which is not properly loaded under the design conditions was determined and removed from the design by means of topology optimization. The topology optimization was run in topology optimization module of ANSYS® Workbench 18.2 finite element analysis (FEA) software package. In the light of the primary shape obtained from the topology optimization study, a producible initial design model was built. This model was then subjected to FE analysis under the same circumstances with the draft model, in order to perform strength and deformation assessments of the initial design. Correspondingly, the critical regions were determined where stress concentrations were observed. The model was updated in a way that the stress values were reduced in these regions through the response surface methodology (RSM). The comparisons between the result and the initial geometries reveal that the mass of the connection bracket was reduced by 63%. Besides, the total deformation which was dropped by the design optimization is 13% lower than the initial design that was generated with the influence of topology optimization result. [ABSTRACT FROM AUTHOR]

Vehicle steering mechanisms are generally considered as safety sub-systems due to their control and stability functions. Therefore, structural elements of a steering linkage should strictly resist the service loads without any overload failure. This paper reports an exemplary case study on the buckling evaluation of the multi-axle steering linkage tie rods which will be used in an 8x8 special purpose vehicle. In the first part of the study, full multibody dynamics (MBD) model of the vehicle including the steering linkage was composed by using Adams/Car™ commercial software. With this model, handling simulations were carried out to determine the service loads for various driving conditions. In order to verify the MBD model, reaction forces occur at the linkage joints were also calculated by using detailed finite element (FE) model of the entire system for the same driving conditions. In the final part of the work, buckling safety of the tie rods was assessed for the critical load case. In this way suitability of the system was evaluated in terms of buckling. [ABSTRACT FROM AUTHOR]

As an inexhaustible and environmentally-friendly energy resource, ocean wave power, which is extracted from ocean waves through WECs (wave energy converters), is highly valued by coastal countries. Compared to other types of WECs, point-absorber WECs, the main body of which can be fixed on a platform (e.g. ship), save on installation costs and therefore have concentrated significant interest among researchers and technology developers. In the development of point-absorber WECs, it is crucial to develop a reliable structural model to accurately predict the structural dynamic responses of WECs subjected to wave loadings. In this work, a FMBD (flexible multibody dynamics) model, which is a combination of MBD (multibody dynamics) and FEA (finite element analysis), has been developed for point-absorber WECs. The FMBD model has been applied to the structural modelling of the NOTC (National Ocean Technology Centre) 10 kW multiple-point-absorber WEC. The floater arm tip displacement and velocity obtained from the FMBD model are validated against the values obtained from an analytical model, which is also developed in this work. The results from the FMBD model show reasonable agreement with those from the analytical model, with a relative difference of 10.1% at the maximum value of the floater arm tip displacement. The FMBD model is further used to calculate the stress distributions, fatigue life, deformations, modal frequencies and modal shapes of the structure. The results indicate that WECs are prone to experience fatigue failure, with the shortest fatigue life (2 years) observed in the floater arm. The FMBD model developed in this work is demonstrated to be capable of accurately modelling point-absorber WECs, providing valuable information for designers to further optimise the structure and assess the reliability of WECs. [ABSTRACT FROM AUTHOR]