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15 December 2012, Volume 34 Issue 6
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    2012, 34(6):  1-6,22.  doi:10.6052/1000-0879-12-187
    Abstract ( 1279 )   PDF (2306KB) ( 1500 )  

    Electronic and opto-electronic systems are being used in many different industries. Roughness of these systems under different kinds of shock and vibration during assembly, transportation and ordinary operation is a major concern. Particularly, with numerous new technologies emerging and new materials being used, the evaluation and the protection of electronic and opto-electronic systems against shock and vibration are becoming increasingly important. Studies of the dynamic response of these systems are highly desirable.

    FATIGUE CHARACTERISATION BASED ON QUANTITATIVE INFRARED THERMOGRAPHY
    FAN Junling, GUO Xinglin, WU Chengwei
    2012, 34(6):  7-17.  doi:10.6052/1000-0879-12-178
    Abstract ( 1149 )   PDF (2902KB) ( 1307 )  
    The quantitative infrared thermography, as a non-destructive, full-field, real-time and non-contact measurement technique, can not only be used to detect the internal defect of materials, but also can identify the fatigue damage evolution of structures in situ. Moreover, it can also be applied to rapidly predict the fatigue limit and the S-N (stress-number of cycles) curve of materials in a short test period with a low cost. This paper systematically reviews the current development and applications of the quantitative infrared thermography, and discusses some important problems in this research field. Finally, the future development and application of the quantitative infrared thermography are discussed.
    2012, 34(6):  18-22.  doi:10.6052/1000-0879-11-380
    Abstract ( 1111 )   PDF (1782KB) ( 940 )  
    There were many theoretical studies but few experimental demonstrations in the structural topology optimization (STO) field. In order to promote the technology of STO in the aeronautical engineering, this paper proposes to use the ‘sensitive threshold'(ST) approach to obtain an ‘innovative structure' and to make test comparisons and analyses of conventional and innovative structures. From the test results, not only a good consistency can be seen as compared with the numerical calculation, but also some findings are made that the stiffness is increased (by more than 10%~30%) and the stresses are lower (less than 10%~20%) for the innovative structure. By using the concept of the ‘structural energy' and the principle of energy, a reasonable explanation of the previous phenomena is made. The comparison tests also demonstrate that the ST approach can obtain the invocative structure effectively, meanwhile, provide precious test support data as well for the application of STO.
    2012, 34(6):  23-26.  doi:10.6052/1000-0879-12-134
    Abstract ( 962 )   PDF (511KB) ( 838 )  
    The determination of cable's parameters is one of key problems in mega steel frame and cable hanging structure. The equations for the internal force and deformation under vertical load are deduced based on a simplified model, then according to Newton's law, the inffiuence of the gliding cable on the mechanical property and the structural deformation under horizontal load is analyzed, and the maximum internal force increment of the cables is obtained. At last, according to the rule that the deffiection of a mega beam in a regular service meets the requirement of codes, the method of first determining the sectional area then the initial pre-stress is presented. This theory is useful for preliminary designs and the performance judgement for this new structure.
    2012, 34(6):  27-31.  doi:10.6052/1000-0879-12-248
    Abstract ( 1149 )   PDF (2856KB) ( 813 )  
    Based on experiment and numerical simulation, the feasibility of the blasting cutter applied in drill jam problems is explored. To deal with the drill jamming accident in the Anqing copper mine, with consideration of the geological characteristics under the well and the drill-jamming conditions, a new type of underwater blasting cutter is invented. The linear shaped charge is introduced into the new type of underwater blasting cutter by adding 12 copper pipes into it, and then the drill pipe would be penetrated by the charge jet. The blasting cutting experiment and the engineering practice show that the new type of underwater blasting cutter is effective in dealing with the drill jamming accident, and can also be used for the similar blasting engineering.
    2012, 34(6):  32-37.  doi:10.6052/1000-0879-12-328
    Abstract ( 940 )   PDF (1184KB) ( 849 )  
    Because of the lack of the research of the mechanical properties of the dewatered sewage sludge, this paper carried out geotechnical experiments, to study the relationship among the void ratio, the compressibility coefficient, the stress-strain relation, the shearing strength and the vertical pressure, and to analyze the inffiuence of the properties of the sludge on the storage bin. Results show that the water ratio and the void ratio of the sludge are much higher than those of the average mucky sludge. For the solid sludge, the shearing strength and the cohesion are much higher than those of the loose sludge. The loose sludge has a high compression, with a minimum compression coefficient under a vertical pressure around 62.5~100 kPa, and the particle structure of the sludge is relatively stable. When the vertical pressure exceeds 60 kPa, the sludge is apparently over- consolidated, the internal friction angle is close to that of the solid sludge. Before putting the sludge into the bunker, it should be crushed to avoid to be over-consolidated.
    THE MECHANISM OF CRACK EXTENSION IN NON-UNIFORM ROCK
    WANG Suling, ZHANG Yiming, JIANG Minzheng, LI Yang
    2012, 34(6):  38-41,45.  doi:10.6052/1000-0879-12-194
    Abstract ( 1059 )   PDF (2781KB) ( 1784 )  
    A clear understanding of the extension of hydraulic fractures on the sandstone-mudstone boundary is the key issue of effectively developing the thin and poor reservoir. In order to simulate the extension property of the fractures on the sandstone-mudstone boundary, with ABAQUS as a platform, the fracture extension process on the sandstone-mudstone boundary is simulated using the separated fracture model with the extended finite element framework. A preset virtual node method is proposed, to make the fracture extension independent of the grid boundary and the extension evolution on the sandstone-mudstone boundary is obtained through the introduction of additional enhancements in the interpolation function of displacement. The fracture extension on the low permeability reservoir sandstone-mudstone boundary is also tracked in real-time by using the white light speckle experiment. The extension process is in good agreement with the numerical simulation, which indicates that the extended finite element method is an effective means of quantitative analysis for fracture extension, and the fracture extension process on the boundary is also studied.
    2012, 34(6):  42-45.  doi:10.6052/1000-0879-12-169
    Abstract ( 661 )   PDF (406KB) ( 637 )  
    The reinforcement of soil can be regarded as an equivalent confining pressure. Through analyzing Mohr's circle, the increase in the minor principal stress is obtained. Assuming that the soil is in a limit state at failure, a limit equilibrium equation is developed to calculate the strength of the reinforced soil while the cohesion and the internal friction angle of the reinforced soil change simultaneously. The formula is discussed in detail, the major principal pressures of the six kinds of reinforced soils under triaxial compression loading are calculated, and it is found that the calculated major principal pressures are entirely consistent with those obtained by the tri-axial tests.
    2012, 34(6):  46-49,87.  doi:10.6052/1000-0879-12-301
    Abstract ( 853 )   PDF (2336KB) ( 520 )  
    Considering the real gradient conditions, a multi-real-time mechanics model for monitoring vehicle's safe travel speed and center of gravity based on the pressure sensor is proposed. The safe travel speed mechanical model is established based on the inffiuence of the center of gravity of the vehicle, the road vertical gradient, the horizontal gradient and the radius of curvature of the road. The mechanism of monitoring and warning the safe travel speed is studied based on the multi-dimensional mechanical model. This model can be used to calculate the safe travel speed and the center position in real time of the motor vehicles, and provide important parameters for developing the monitoring system in real time for the safe travel speed of automobiles.
    2012, 34(6):  50-54.  doi:10.6052/1000-0879-12-196
    Abstract ( 1211 )   PDF (524KB) ( 804 )  
    Using the three wire- pendulum to measure the moment of inertia is a common practice. The cycloid is usually assumed in an ideal state theoretically (i.e the mass of the cycloid approaches 0). But actually, if the workpiece measured is heavy, the mass of the cycloid can not be neglected, we have to consider the mass of the cycloid in the moment of inertia of the empty turning wheel. This paper uses the Halmiltonian theory and the variable substitution to derive the variable tension string vibration equation of the three wire-pendulum cycloid. And from the state of the point in the junction of the cycloid and the turning wheel (x=0), we obtain a computational formula for the moment of inertia by using the three wire-pendulum without neglecting the mass of the cycloid. In addition, we can make calculations by MATLAB.