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A new payload swing control method considering the vibration of tower crane is proposed in this study. The coupling between the structural vibration and the payload swing is neglected in existing studies on tower crane swing suppression. Changes of sling length are considered as disturbances. They cause the existing methods of swing suppression method ineffectual in the actual working situation. In contrast, the structural vibration of the tower crane is taken into account in this study. At the same time, the sling length is regarded as a control variable to reduce the payload swing. A new swing suppression algorithm is proposed in conjunction with phase plane analysis method. In addition, a systematical tower crane multibody system dynamic analysis platform with changing of sling length is established to verify the effectiveness of the algorithm. The traditional finite element method is used to model the tower body and boom of tower crane while the Arbitrary Lagrange Euler Absolute Nodal Coordinate Formulation (ALE-ANCF) cable element is applied for modeling the sling. This two parts are connected with sliding joint obtaining the tower crane multibody system model. Numerical examples show that the proposed method can reduce the swing amplitude the payload effectively when considering the coupling between the structural vibration and the payload swing.

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.

To analyze the stability of non-uniform crane structures with stepped and tapered columns, equivalent element stiffness derived from hybrid of the transfer matrix method (TMM) and the finite element method (FEM) is proposed. The second-order theory is applied to establish the differential equations of the stepped column with any number of sections, and the exact slope-deflection equations of the equivalent element are derived by TMM. Furthermore, the slope-deflection equations are formulated into the exact symmetric tangent stiffness matrix in FEM. Based on the FEM buckling criterion, the critical forces of stepped columns can be obtained precisely in Bernoulli–Euler sense. Buckling criterion equations of the stepped column with three widely used constraints in crane structures are given as the application of the proposed stiffness. Meanwhile, the proposed stiffness matrix of the stepped column is extended to analyze the buckling of the tapered column, which can be simulated by the four-section stepped column with the selective equivalent inertia moment. Finally, verification examples demonstrate that the proposed method can be used to accurately and efficiently evaluate the critical load of the non-uniform crane structures.

This investigation is intended to develop a computer procedure for the integration of NURBS geometry and the rational absolute nodal coordinate formulation (RANCF) finite element analysis. A linear transformation is given that can be used to convert the NURBS curve to RANCF cable element mesh retaining the same geometry and the same degree of continuity, including the discussion of continuity control and mesh refinement. The green strain tensor is used to establish the nonlinear dynamic equations with numerical examples to demonstrate the use of the procedure in the dynamic analysis of flexible bodies.

The element created in this investigation is based on the it absolute nodal coordinate formulation (ANCF) which has been successfully used in flexible multibody system dynamic and integration of computer aid design and analysis (ICADA). When modeling a B-spline curve with ANCF beam element, it is the common manner to convert this curve into a series of Bezier curves because the systematical conversion between ANCF beam element and a Bezier curve has already been built. In order to avoid the constrain equation produced in this method and to express a B-spline curve using only one element, an alternative approach is developed, leading to the piecewise ANCF (PANCF) beam element. It is demonstrated that when two ANCF beam elements are connected according to a particular continuity, they can constitute a PANCF element. Besides, a new PANCF element will be produced when an ANCF element is connected to an existing PANCF element. The continuity condition can be automatically ensured by the selection of nodal coordinates and the calculation of the piecewise continuous shape functions. The algorithm for converting a B-spline curve to a PANCF beam element is then given. There also are discussions on the features of PANCF element. When two neighboring segments of PANCF element have the same assumed length, the position vector at the interface cannot be expressed by the other coordinates so the position vector is preserved in the $$C^{2}$$ continuous situation. Two examples are given to conclude the interpolation and continuity properties of the shape function and to demonstrate the feasibility of this PANCF in the ICADA.

A new approximate model for predicting the crack growth rate is proposed, which can condense the stable crack propagation stage curves for non-zero stress ratios to that for R = 0 in a narrow band. By using the new approximate model, the obtained material constants corresponding to R = 0 can be further widely used for different loading amplitude ratios. Many available experimental data taken from literature are analyzed using the proposed model for prediction of the crack growth rate. The results indicate that the new approximate model is accurate and effective to consider the R -ratio effect on the crack growth rate.

An elastic analysis of an internal crack with bridging fibers parallel to the free surface in an infinite orthotropic anisotropic elastic plane is studied, and asymmetrical dynamic fracture model of bridging fiber pull-out of unidirectional composite materials is presented for analyzing the distributions of stress and displacement with the internal asymmetrical crack under the loading conditions of an applied non-homogenous stress and the traction forces on crack faces yielded by the bridging fiber pull-out model. Thus the fiber failure is ascertained by maximum tensile stress, the fiber ruptures and hence the crack propagation should also appear in the modality of self-similarity. The formulation involves the development of a Riemann-Hilbert problem. Analytical solution of an asymmetrical propagation crack of unidirectional composite materials under the conditions of two increasing loads given is obtained, respectively. In terms of correlative material properties, the variable rule of dynamic stress intensity factor was depicted very well. After those analytical solutions were utilized by superposition theorem, the solutions of arbitrary complex problems could be gained.

The analyzed multi-body system is a complex mechanism whose component rigidities are quite different. If the multi-body system is considered as a rigid multi-body system to analyze its dynamic characteristics, false analysis results will be caused by ignorance of elastic deformation. If it is completely considered as a flexible multi-body system to establish the model, analyze and solve, the system equations are quite large which make them difficult to solve. The feasible method is as follows: the complex mechanical system is divided as a rigid-flexible coupled system with a few flexible components and an equivalent system. The equivalent system is formed by making dynamic characteristics of rigid components and elements to be equivalent. Then the equations are established according to the flexible multi-body system's way and the system equation dimensions are reduced by introduction of transition matrixes. Taking a harbor crane's jointed arm crane mechanism as an example, a modeling method for rigid elements and flexible elements coupling is presented, the rigid elements and rigid constraint conditions are introduced, the system model is reduced based on the flexible multi-body system and analysis efficiency is improved greatly. The feasibility and availability of rigid-flexible coupled system dynamic analysis method are verified.

A novel 3-DOF high speed and high precision manipulator, which combines direct driven planar parallel mechanism and linear actuator, is introduced. Through adding some constraints, workspace with well kinematics performance can be generated, and the optimization of geometric parameter is carried out in terms of a new performance index composed of speed and dexterity. Design study then is carried out in the software ADAMS environment to analyze the approximate design sensitivity of the variable; that is, the effects of parameter of each beam cross sectional area and relative position of linear actuator on model performance. Several conclusions are then drawn on the appropriate way of dynamics optimization to get a lightweight and small deformation manipulator. Dynamics simulation of an improved planar parallel mechanism with different cross section and another unrefined one are compared. The stiffness of them is almost equal, but the mass of the improved one decreases 30 percent compared with the initial one. That means this way of optimization is efficient