Papers by Author: Jun Ping Shi

Abstract: The goal of this paper is to present non-geodesic trajectories for filament wound truncated conical domes for pressure vessels. The fiber trajectories for non-geodesically overwound truncated conical shells are obtained based on differential geometry and the non-geodesic winding law. The influence of the slippage coefficient on non-geodesic trajectories is evaluated in terms of the winding angle distributions. The non-geodesic trajectories corresponding to various initial winding angles are also illustrated for the given slippage coefficient. The results show that the winding angle distribution of non-geodesics on a truncated conical dome has an overall increase with the increase of the slippage coefficient or the initial winding angle. The present method can provide a significant reference for developing non-geodesically overwound conical structures.

Abstract: In this paper we apply semi-geodesic trajectories to the creation of isotensoid domes for filament wound pressure vessels. The governing equations for the determination of the meridian shapes and related winding angle distributions of domes are derived using the netting analysis and the semi-geodesic winding law. The effects of the slippage coefficient on the geometry and fiber trajectories of the domes are respectively evaluated in terms of the resulting meridional curves and fiber angles. It is revealed that the semi-geodesic angles and the dome depth have an overall decrease with increasing the slippage coefficient. The results also demonstrate that the use of semi-geodesics significantly enlarge the design space for the geometry and adapted fiber trajectories of the domes. The present method can provide a significant reference for the design and production of the domes for semi-geodesically overwound pressure vessels.

Abstract: The experimental procedures of mixed mode fracture of several ductile materials are investigated. The position and direction of crack initiation are determined according to a new method. The variations of fracture caused by different physical mechanisms are analyzed. Through studying the changing regularity of different fracture mechanisms, it is believed that the main ways of the fracture in ductile materials can be divided into three groups. They are traction fracture and two different types of shear fracture. Void nucleation, expansion and coalescing are the dominant mechanism of traction fracture. The formation and development of localized shear bands are the dominant mechanism of the two different types of shear fracture. Localized large plastic deformation will cause damage within the material. The fundamental factor, which causes the occurrence of fracture in the material, is a certain stress parameter at the dangerous point has reached the critical fracture value of the material. Based on those phenomena listed above, several fracture controlling parameters for different fracture forms have been discussed, and several new parameters, which affect various fracture forms, have been proposed.

Abstract: Abstract. The optimal control strategy is introduced to improve the motion accuracy of planar 3-DOF parallel mechanism. The optimal control of error performance of mechanism is achieved by structuring and quantizing the quadratic form index of the error performance, and taking into account both the system response and energy control in state space, so we study the problem which can be boil down to solve two-point boundary value problem of differential equation. The simulation results show that the actual motion of mechanism keep the better tracking accuracy with the global motion while dynamics parameters is changing, and the controller is ease to accomplishment in the industrial due to the simply structure and the stable change of control energy.

Abstract: Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.

Abstract: During the process of elastic deformation, based on first law of thermodynamics, deformation energy value equals to the work done by external forces moving through elastic deformation, which can determine the amount of elastic deformation. According to second law of thermodynamics, the true deformation energy value should be the minimum of all possible deformations, which can determine the distribution rule of elastic deformation. From this, it can be realized that there are some problems existed in the derived process of the minimum potential energy principle. The total potential energy of system remains constant in all of possible elastic deformation. Applying the two characteristics of elastic deformation, a few application problems could be solved expediently.