Papers by Author: Chao Hua Fan

Abstract: Interfacial delamination is a recognized failure mode in Integrated circuits (ICs). A major cause for this failure is the mismatch of Thermal Expansion Coefficients, Young’s modulus, and Poisson’s ratios of the package materials. Here, the influence of delamination between epoxy and dielectric layers on pattern shift and passivation cracking in IC package under aeronautical conditions, mainly temperature and load cycles, is studied by maximum plastic strain and maximum principal stresses theory using a certain 2D FEM model with different delamination length “L_c.right”. Delaminations are easy to introduce more dangerous impact to the package, because the IC microstructures endure serious thermo-mechanical loading under aeronautical working conditions. The method can be used to find the dangerous designed structure schedules and will provide a basis for selecting passivation materials of aeronautical IC packages.

Abstract: Genetic algorithm is introduced in the study of network authority values of BP neural network, and a GA-NN algorithm is established. Based on this genetic algorithm-neural network method, a predictive model for fatigue performances of the pre-corroded aluminum alloys under a varied corrosion environmental spectrum was developed by means of training from the testing dada. At the same time, a fuzzy-neural network method is established for the same purpose. The results indicate that genetic algorithm-neural network and fuzzy-neural network can both be employed to predict the underlying fatigue performances of the pre-corroded aluminum alloy precisely.

Abstract: When studying the growth of triaxial-stress-state crack, the plastic work rate consumed in the process zone at crack tip should be described clearly. Fracture for a cracked specimen is related to rupture of a simple uniaxial tensile specimen by nature. By equaling the crack tip stress-strain field to uniaxial stress-strain field, it is obtained that the plastic work rate consumed in the process zone at crack tip can be expressed by the plastic energy density WF multiplied by the equivalent size of the process zone hF. The plastic energy density WF can be expressed by virtue of uniaxial true stress-strain curve. And analytical form of hF for triaxial stress state is presented by recourse to three-dimensional analyses on material behaviors. The expression of plastic work rate consumed in the process zone is verified by the predicting fracture toughness.

Abstract: Based on the analyses of reliability and life characteristics in electronic equipment, a new concept of Electronic Equipment Life Envelope (EELE) is presented. The basic approach to EELE establishment is investigated in detail. The interrelationship between storage life and working life of electronic equipment is demonstrated by virtue of EELE, which validates its preliminary application and advantages. The new philosophy can be further applied to accelerated experiments and service life prediction for electronic equipments.

Abstract: In the paper, genetic algorithm is introduced in the study of network authority values of BP neural network, and a GA-NN algorithm is established. Based on this genetic algorithm-neural network method, a predictive model for fatigue performances of the pre-corroded aluminum alloys under a varied corrosion environmental spectrum was developed by means of training from the testing dada, and the fatigue performances of pre-corroded aluminum alloys can be predicted. The results indicate that genetic algorithm-neural network algorithm can be employed to predict the underlying fatigue performances of the pre-corroded aluminum alloy precisely, compared with traditional neural network.

Abstract: An effective energy criterion is presented and can be narrated as follows: only the effective release energy has an immediate effect on fatigue crack growth characteristics, and the crack extension in each load cycle is decided by the effective release energy. The effective release energy is considered as the energy released for crack extension after the fatigue crack fully opens and it is equal to the consumed energy in the same crack extension. And the consumed energy can be obtained by the cracking resistance of materials. An approach for determining cracking resistance curve is proposed and validated by experimental results. Based on effective energy criterion, a model for fatigue crack growth is presented. And fatigue life can be predicted by recourse to the model. Validation against calculations by the model and experimental data shows good agreement.

Abstract: To consider the corrosive effects on aircraft structural life under natural environments, we have the calendric life to represent its impact. A new concept of Aircraft Structural Life Envelope (ASLE) to consider the combined effects of fatigue loads and corrosive conditions is developed and the sketch of ASLE is presented, then the basic determining methods of ASLE under different corrosive conditions are obtained too. Finally the linear damage cumulative rules are employed to analyze the usage of aircraft in different corrosive conditions, and the residual fatigue life and calendric life of aircraft structures can be predicted and supervised.