Papers by Author: Li Bin Zhao

Abstract: A failure analysis of a single-lap single-bolt composite joint with a countersunk fastener was carried out using a progressive damage model. The FE model considering the distributions of fine and coarse meshes, appropriate contact pairs and the bolt preload was established. Based on the analysis, the five stages in the load-displacement curve and the changes of tilt angle were discussed in detail as well as failure contours of hole laminates at typical events during the damage propagation are illustrated. The inherent development tendency of the tilt angle accompanying with the damage propagation in the single-lap joint vividly depict its failure process.

Abstract: Damage resistance behaviors of CCF300/5428 laminates under five levels of impact energies have been researched by using progressive damage method. The progressive damage models (PDM) are composed of 3D finite element models, Hashin-type failure criteria and Camanhos degradation rules. The impact procedure has been simulated by the progressive damage analysis with user defined subroutines which have been developed and embedded into the general finite element analysis package. The history curves of the contact force and the impact point displacement are plotted. The global damage at typical events for various impact energies is investigated.

Abstract: Fatigue stiffness degradation behaviour of woven composite π joint subjected to tensile-tensile cycle loading is studied. Because of the complex structural configuration of woven composite π joints and a variety of failure modes, there exhibited four stiffness degradation modes in fatigue test. For example, stable slight reduction mode, abruptly decreasing mode, step decreasing mode and constant stiffness mode. Each stiffness degradation mode has a corresponding failure mode in fatigue test.

Abstract: Taylor series numerical method (TSNM) is extended to the field of transient heat conduction. Theoretical description of TSNM for transient heat conduction problems is presented. Furthermore, the algorithm is realized and embedded in commercial software ANSYS®. If a lumped mass heat capacity matrix provided, the governing equation of transient heat conduction problems, which is a differential equation, will be solved by a series of recursion calculation of Taylor expanding coefficients. A typical transient heat conduction problem with analytical solution was discussed to verify the TSNM. At last, the TSNM is applied in the transient heat analysis of an all-solid fiber optic gyro (FOG).

Abstract: Model updating techniques are used to modify structural model for more accurate predictions of dynamics behavior. A simple survey on the model updating methods and correlation criteria is presented. Based on the inverse eigensensitivity method (IESM) and modal assurance criterion (MAC), a scheme of model updating for structures is presented and realized by user defined subroutine combined with APDL in commercial software ANSYS®. A four-DOF spring-mass system is assumed and updated, from which the predicted frequencies and MAC values are satisfied compared to the actual dynamics characteristics. This gives evidence that the presented model updating scheme is feasible and efficient. Furthermore, a cylindrical shell structure containing global and local modal information is established to research the updating ability of the scheme on some focused local modal information. The results due to the updated model of cylindrical shell structure show that not only the global modal data but also the local modal data have a good agreement with that of the actual structure.

Abstract: All composite π joints, which can minimize structure redundancy and pave the way for much reduced assembly time, have been developed as a great achievement of the integrated structure technique. To obtain knowledge about the mechanics behavior of composite π joints after cycle loadings, especially residual strength, cycle fatigue test and tensile test for the joints are conducted. From this study, some significative remarks can be made: the strength of composite π joint has reduced slightly by fatigue crack; the residual strength and the general rigidity of the joint exhibit large scatter; the filler zones and tip zones are those of potential weakness in the joints, and the sample in residual strength test has similar failure patterns with that in static tensile test.

Abstract: Stitched woven composite π joints and paralleled samples without stitching were investigated by numerical analysis under tensile loading. The effects of stitching on the mechanics behavior of composite π joints are presented. Stitching technique can reduce initial failure load of composite π joint, but remarkably improve the rupture load. The failure process of composite π joint, including the damage onset, propagation path and final failure pattern, is also limited in the stitched area. The failure mechanisms are expatiated by the numerical data and failure picture to obtain more knowledge about the mechanics behavior of composite π joints.

Abstract: 3D finite element models of magnetic suspended control moment gyroscope structure are established by general finite element analysis software. Initial modal analysis scheme of the MS-CMG structure, in which the frame and gyro-chamber are analyzed separately, is described. A new modal analysis scheme that the MS-CMG is analyzed as a whole structure is presented. The connection between the gyro-chamber and frame is realized by defining a revolution pairs. The numerical predictions from two modal analysis schemes show obvious difference. The new scheme is more reliable since it simulates the real wok status of MS-CMG.

Abstract: The effects of humidity and ultraviolet radiation aging on fatigue properties of carbon/ bismaleimide composites and coating protection action were presented. Specimens with central hole are made of carbon/bismaleimide laminates. Compression-compression (C-C) fatigue tests under normal lab environment were operated respectively for four groups of specimen, (1) specimen under normal lab environment, (2) specimen under UV radiation aging with dryness, (3) specimen under UV radiation aging with moisture, and (4) specimen with coating under UV radiation aging with moisture. Variance analysis of experimental outcomes gave significances of the environment effects on C-C fatigue life of specimens. The results reveal that UV radiation have remarkable effects on the C-C fatigue life of the composite laminates under the same humidity, whereas combined action of UV radiation (300MJ/ m2) and humidity have no significant effects on the C-C fatigue life. Coating can provide effective protect the specimen from UV radiation aging.

Abstract: A progressive damage method is adopted to predict the structural strength of a woven out-of plane composite bonded π joint. A 3D progressive damage model is established and analyzed via a user defined subroutine embedded into the general FEA package. The numerical prediction gives the information of damage onset, damage propagation and final failure pattern, initial and final failure strength. Three samples of woven composite π joint under tensile load are tested to verify the numerical results. The numerical prediction agrees well with the experimental outcomes. All the numerical and experimental results provide insight into the basic understanding of static strength of woven composite bonded π joint.