Nianli Lu

Due to the low cost and short erection period, the flexible protection system is gradually replacing the traditional cross-frame design based on a large steel structure and becoming the main means of protection in power construction. The accurate dynamic analysis of the process of wire falling into a nylon rope net after tension failure is the key to the design and optimization of the flexible protection system. Efficient modeling and analysis of rope network are the core problems. In this investigation, the absolute nodal coordinate formulation cable element is used to model the transmission wire and the nylon rope net. The form finding of the net is performed based on the iterative force density method. The static condensation method is introduced to perform the dynamic analysis of the net to ensure the simulation efficiency. An experiment is carried out to verify the proposed modeling and analysis method. Configurations are compared between the simulation and experimental results so that the feasibility of the proposed method can be demonstrated.

The construction of high-order shape function is a key and difficulty for unstructured grid mesh and sliding boundary problem. In this paper, a construction method of space-time absolute nodal coordinate formulation quadrilateral cable (SACQ) is proposed and the accuracy of SACQ element is studied and verified with 3 different applications. First, the shape function of SACQ is constructed with spatiotemporal reduction coordinate and the action integral of SACQ is composed with Lagrangian function and discrete with perspective transformation. second, numerical convergence region is discussed and determined with Courant number. Furthermore, a space-time nodal dislocation and its relation with Courant number is studied. The simulation and verification are focusing on some realistic problems. Finally, one-sided impact, free-flexible pendulum, taut string with sliding boundary and a deployable guyed mast under impact transverse wave are simulated. In these problems, unstructured grid meshed with SACQ has similar energy convergence and accuracy with structured grid but shows better efficiency.

In this paper, a space-time absolute nodal coordinate formulation cable (SAC) element forming technique based on the Lagrange family of shape functions is proposed. Two distinct SAC elements, each with a distinct spatial shape function, have been generated by this method. Moreover, the external forces such as the bending moment and the air resistance formula have been accounted for. The Lagrange multiplier method, along with the concepts of replacement constraint and supplementary constraint, has been employed to provide a solution for the dynamics of constrained mechanical systems. Additionally, a constraint conversion strategy has been suggested. The solver has been constructed through Hamilton’s law of varying action. The space-time finite element method is used to solve dynamic problems, employing the Newton algorithm and quasi-Newton algorithm. The accuracy and efficiency of the solution has been verified by three simulations and one experiment. The circle-bending static simulation and the double-ended velocity impact dynamic simulation demonstrate the accuracy of the two elements. The correlation between statics and dynamics has been studied for different discretization methods and different solvers’ calculation accuracy and efficiency. Different modeling methods, time steps, order and the application of the quasi-Newton method all have a bearing on the efficiency of the solution. Finally, a comparison with an experiment in the free-pendulum simulation reveals the capability of this model to simulate dynamic problems with air resistance.

Typical engineering cable structures, such as high-voltage wire and wire rope, usually bring a damping effect which cannot be ignored due to the technological problems of manufacturing. For such problems, especially the damping of cable structures undergoing large displacement and severe deformation, few studies have been reported in the past. In this work, the fractional derivative viscosity model is introduced into the cables described by the absolute nodal coordinate formulation. The computer implementation algorithm of the proposed cable damping model is given based on the three-parameter fractional derivative model. Two numerical examples demonstrate the effectiveness and convergence property of the proposed cable damping model. An experiment is proposed in which a wire is tensioned and released. Configurations are captured by the high-speed camera and compared with the results obtained from the numerical simulation. The agreement of the simulation and experimental results validates the proposed cable damping in application.

In contact analysis, reducing the computing time has been an issue under the premise of ensuring calculation accuracy around the region with violent stress changes. To improve computational efficiency for contact analysis in flexible multibody system, this paper proposes an adaptive local mesh refinement and coarsening approach based on analysis-suitable T-splines (ASTS). First, the kinematic model of thin plate is established based on analysis-suitable T-spline surface, and large deformation of flexible thin plate is described by the elastic model created by nonlinear Green–Lagrange strain. Second, to reduce computing time in contact analysis and ensure analysis accuracy, based on contact state and refinement distance, an effective adaptive local element mesh update method is proposed, which only refine locally on subject's refinement region and integrate redundant elements to reduce the degree-of-freedom (DOF) of system. Third, to analyze the system with varying mesh, a new solving algorithm with dynamic variables and geometry update routine is developed. Finally, performance of the proposed method in static and dynamic simulation is validated by four numerical examples. Results and consuming time of ASTS-based varying mesh prove the feasibility of the proposed method in contact problems.