Jian Jun Wu

A study on the forming limits of the hydromechanical deep drawing of components with stepped geometries

Abstract FE simulations using ABAQUS/Explicit were conducted to examine the upper and lower forming limits of the hydromechanical deep drawing (HDD) of stepped components. Comparison of FE simulations and experimental results reported previously suggests that FE analysis may replace experimental trials to derive “master curves” of HDD, and hence renders higher efficiency of the tool design and process control of HDD, particularly for the forming of complex component-forms.

Digital Research of Unmanned Aerial Vehicle Avionics System Based on CAN Bus

Small unmanned aircraft for civil and military has a wide range of applications. The design of traditional UAV avionics system is use discrete lines which link one point to another to communicate. It will make the system complexity, and the anti-jamming performance is poor. A new kind of design idea of unpiloted aircraft digital avionics system based on CAN bus is introduced, and this article also made a further study in the avionics systems’ critical subsystems, components and redundant design. The new avionics system, which used bus communication system has many good points, such as strong anti-interference ability, easily extended, simply configuration and so on. The system also has a certain value to promotion.

Minimum bending radius of Al-Li alloy extrusions in stretch bending

In this investigation, the attention is focused on the minimum bending radii of 2196-T8511 and 2099-T83 Al-Li alloy extrusions. To predict the failure of Al-Li alloys, sheet and extrusion stretch bending tests are developed, carried out and simulated using finite element model. The theoretical minimum bending radius is introduced to derive a safe lower limit for the bending radius which can serve as a guideline for tool and product design. Stretch bending tests of Al-Li alloys are performed using the three-point bending test and displacement-controlled stretch bending test at room temperature. The finite element model incorporates three-dimensional solid elements and ductile damage modeling. The experimental results show that Al-Li alloy extrusions in stretch bending show three types of failures, occurring at the unbent region near the entrance of the jaws, at the region below the exit of the die and within the region in contact with the die, respectively. Comparison between predicted values and experimental results has been made, a consistent agreement being achieved, reflecting the reliability of the present model. The three types of failure mechanisms which compete with each other are tensile localization failure, die-corner failure and shear failure, respectively. Based on the analytical models, experiments and simulations, it appears that the three distinct failures need to be applied to predict the minimum bending radius and range of failures that can occur with 2196-T8511 and 2099-T83 Al-Li alloy extrusions in stretch bending.

Software Design of Aircraft Electrical Load Management Center Based on μC/OS-II

This paper introduces that embedded real time operating system μC/OS-II is applied in software design of aircraft electrical load management center. Firstly, the μC/OS-II and its running on ARM are briefly presented. Then the method of two system running modes is given in details. And the tasks assignment, priority allocation and communication between tasks under both two modes are also provided. Results show that multitask schedule managements of real-time system has solved the problem of poor real-time in a single task system. And the reliability of the system has been greatly improved.

Numerical Simulation of Residual Stress in Quenching 2024 Honeycomb Aluminum Alloy Thin Plates

The heat transfer coefficient during the aluminum thin plate quenching is difficult to measure experimentally. In this paper, according to the warping deformation characteristics of the 2024 honeycombed aluminum thin plate quenching, the heat transfer coefficient is obtained using finite element software ABAQUS. During the calculation process of the heat transfer coefficient, the sheet practical quenching process of immersion and the air-cooling has been considered. Using the heat transfer coefficient above, the quenching temperature field is solved through the simulation. Based on the temperature field, the residual stress field is simulated. Depending on the simulation results, the magnitude and the distribution of the residual stress is obtained. By X - ray diffraction method, the simulation results have been compared to the experiment results and they are in better agreement. It proves that the simulation method is available and effectively.

Design of Aircraft Electrical Load Management Center

Aircraft Electrical Load Management Center, an important part of the aircraft power supply system, solves the automatic management of aircraft load via a multi-channel transmission bus and a solid-state power controller. Using micro-computer technology, instead of manual operation, for automatic control and management of the load has improved the existing method of distribution and load management, which has enhanced performance of aircraft and its maintenance of power system. This paper studies the overall structure and composition principle of ELMC and details ELMC’s functions of each component modules and the implementation of hardware and software. System test results show that the automatic load management techniques greatly improve the aircraft power system reliability and maintainability.

Cutting Line Design Method for Woven Composite Materials Fitting to Free Surface

On the fitting process simulation, the dangerous area related with buckling or tearing phenomena is identified with special colors and values, then deleting, cutting line designing, refitting and spreading processes are implemented to obtain a reasonable blank shape with dart feature. Moreover, a so called expanding surface method was presented in order to realize the fitting and spreading of free surface with hole feature. The above provided methods are realized through software codes and used in some cases effectively.

Hybrid-Knowledge-Models-Based Intelligent Fault Diagnosis Strategies for Liquid-Propellant Rocket Engines

This paper focuses on a qualitative fault diagnosis method based on the integration and fusion of shallow and deep knowledge for liquid-propellant rocket engines (LR E). The paper firstly clarifies the concept and the types of LRE diagnosis knowledge. L ater, from the isomorphic transform point of view, the paper analyses the correlation of diffe rent knowledge and knowledge representation, and formulate the LRE fault diagnosis. Then, the ways of cquisition, representation and organization for knowledge-based hybrid models constructed by sign ed directed graphs, rules, prepositional logic models, and qualitative deviation models are given. The intelligent diagnosis strategies for LRE, which reason and make a decision by multiple and synthetically utilizing all kinds of diagnosis knowledge such as experience, causality, system s tructure, and models, are presented.

QUALITATIVE -DEVIATION -MODEL -BASED FAULT DIAGNOSIS FOR LIQUID -PROPELLANT ROCKET ENGINES

Based on the qualitative modeling and consistency checking techniques, the qualitative - deviation -model -based fault diagnosis method for liquid -propellant rocket engine s (LRE) was proposed and developed i n this paper. Firstly , the ways of acquisition, representation and organization for the diagnostic knowledge by the form of qualitative deviation models was formulated . The n, the fault diagnosis method , which reason and make a decision by producing the con flict sets, was presented . The results for case study show that the diagnosing ability of the method proposed is better than the method based on the rule knowledge.