Applied Mechanics and Materials Vol. 163

Abstract: Removable steel refuge chamber is a very important device for lifesaving in coal mine disasters, such as fire, gas explosion, roof fall, and so on. So the chamber body should have good stiffness, strength, and tightness under disaster conditions. The stiffener structure in refuge chamber body has been investigated with FEM, and a kind of design was suggested.

Abstract: Operation sequencing is one of the most important tasks in process planning. The sequencing procedures associate manufacturing features from 3D CAD models and machining methods together to satisfy certain manufacturing process constraints. In order to simplify process constraint aggregations, two types of constraint matrixes, feature constraint matrix and the operation constraint matrix, are proposed in this paper, which take into account of the compulsive constraints, such as geometric topology constraints, manufacturing process knowledge criteria, custom compulsive constraints and so forth. Accordingly, an iterative genetic algorithm is proposed, which is naturally used in the manufacturing feature level and operation level. In the manufacturing feature level, feasible feature sequences are generated based on the analysis of feature constraint matrix. In the operation level, the information that is contained in the machining operation such as machine tools, set-ups and cutting tools is considered to optimize the operation sequences based on the results acquired in the feature level. Compared with the traditional simple genetic algorithm, the iterative genetic algorithm is proved to be superior in shortening the operation sequencing time.

Abstract: Remote sensing satellites equipped with large synthetic aperture radar (SAR) can image the earth in all weather and lighting conditions. For high packaging efficiency in launch and precise configuration on orbit, deployable mechanisms are designed to deploy the large SAR antenna panels. For the two-panel antenna, a six-bar-linkage deployable driving mechanism is designed. According to the design, a parameterized dynamic model is built in ADAMS software with secondary development technology to obtain its dynamics characteristics through simulation analysis. To improve the dynamic characteristics and the precision of deployment design of experiments and optimizations were carried through in this paper.

Abstract: Tower crane are widely used in construction and installation in our country, especially in high-rise building, tower crane is indispensable construction machinery. But the tower crane accident happen high frequency. This essay based on the accident tree analysis methods, combined with tower crane accident type which establish accident tree model, and then resolve the minimal segmental sets, analysis the accident cause factor, According to the qualitative analysis and quantitative analysis of fault tree analysis, we can put forward some prevention ways and control measures to the tower crane accident in those aspects of unsafe actions of the human beings, insecure status of objects and the defects in safety management.

Abstract: To investigate the effects of bony structure simplification methods on the biomechanics of tibiofemoral joint under compression and torsion effects in series of flexion angles, the MRI images of the normal human knee at flexion angles of 0°/25°/60°/80° were developed through SONATA MAESTRO 1.5T, then through the technology of threshold segmentation and registration assembly, bone tissue distinguished models and single material models were built based on these images. The results show that: (1) at the flexion angles of 0°/60°/80°, the maximum equivalent stress on femur and femoral cartilage significantly were slightly higher than single material models, only at 25 °, the maximum equivalent stress of the femoral cartilage in single material model was obviously larger; (2) difference of maximum equivalent stress on tibia and tibial cartilage between two kinds of models was not significant, and stress increased with the increase of flexion angle, only at 80 °, the stress on tibia of bone tissue distinguished models reduced; (3) The skeletal load was borne mainly by the cortical bone.

Abstract: Nowadays six axis machining robots are widely used in many fields of industry. Compared to machine tools, industrial robots offer a cheaper yet more flexible alternative to the machine-tools in the cleaning and pre-machining applications of aluminum castings. But the low stiffness has limited the application of industrial robots to the machining tasks with very low precision requirement. This paper presents a practical approach to improve the robot-machining accuracy by developing an off line simulation tool. Firstly we will complete the dynamic simulation of the 6-axis stiff model in CATIA-LMS for trajectory planning. Secondly we will set flexible joints and balancing system for the industry machining robot in LMS. Finally we will make some compare with the position trajectories generated by flexible joint and stiff joint, and then adjust the parameters under the references of the simulation result before the industry machining.

Abstract: Technology has evolved through the dynamic process of knowledge transfer. The exploration of technological evolution from a quantitative perspective has often been mentioned in the intellectual pursuit. The study applies bibliometric method to the articles published in the field of mechanism and machine theory (MMT). Afterward we analyzed the trends of MMT articles during the 30 years. We found that the ratios of the MMT papers in each journal have a trend of growth and have been centered on the certain two magazines. The articles of MMT exhibit a trend of growth. The USA, China and Canada are the major countries which frequently published the papers in the field of MMT and have significant performance in citations. China has rapidly grown in the quantity and the ratios of papers. In addition, the top 10 researchers with the highest h-index in the field of MMT are primarily affiliated with institutions in English-spoken countries, trumping the other countries.

Abstract: Disposable mechanical elements with extremely short lives are widely used in the aerospace and defense fields. To reliably evaluate the life of disposable mechanical elements, many attentions were concentrated in the fatigue properties of disposable mechanical elements. According to the different meanings of static strength for metals, disposable mechanical elements are divided into two groups with different fatigue properties: extremely low cycle fatigue module for Type I with ultimate strength as design stress and low cycle fatigue module for Type II with yield strength as design stress. The Kuroda model and a cumulative damage model consisting of the Miners rule and the sequential law are used in the fatigue design process of the Type I. To the Type II, the Manson-Coffin model is suitable for conventional applications but more attempts are still conducted to further improve stress levels. The Type II with increasing load sequences are specially treated, since the cyclic yield strength of certain materials under pulsating stress closing to the yield strength increase with the deepening of fatigue damage. Consequently, under the increasing pulsating cyclic loading, the later load whose amplitude is higher than the initial yield strength will be permitted.

Abstract: To study the dynamic behavior of the extendible support structure deployment, a digital simulation using the multibody system dynamics methodology is conducted. Floating frame of reference formulations are used to establish the flexible dynamics model, in which the deformation vector of each flexible part is modeled with the component mode synthesis technique based on the Craig-Bampton method. Modal truncation is implemented through modal participation factors to reduce the computational burden. Angular displacements results of antenna panels as well as those of truss rods are then obtained and show that all parts of the structure have reached accurate positions and keep stable after deployment as expected. Start torque of the driving motor is also acquired and proved acceptable according to the design requirements. Impact forces acting on the hinges at locking moment are finally extracted to evaluate performances of locking processes.

Abstract: Tool deflection is one of the important influencing factors for surface roughness and surface integrity of work piece in cutting process. The excessive deflection even causes seriously defects of work piece or failures of tool. This paper gives theory analysis and mathematic method to predict the tool deflection by means of the cantilever beam deflection theory. Based on modeling of 3-dimmsion milling force model, the finite element analysis has been performed for calculation of tool deflection. The experiment of tool deflection of solid end mill is performed to compare simulation and theory. Results show the correction and reliability of research method. It lays a foundation for fast calculation of tool deflection and optimization of milling parameters.