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15 October 2011, Volume 33 Issue 5
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    2011, 33(5):  90-92.  doi:10.6052/1000-0879-lxysj2011-045
    Abstract ( 2170 )   PDF (7767KB) ( 652 )  
    2011, 33(5):  74-75.  doi:10.6052/1000-0879-lxysj2011-050
    Abstract ( 852 )   PDF (5832KB) ( 1587 )  
    2011, 33(5):  38-41.  doi:10.6052/1000-0879-lxysj2011-084
    Abstract ( 992 )   PDF (7113KB) ( 513 )  
    By analyzing the roll stability of hydraulic module assembled trailer of three columns with arbitrary axis, the general formulas are obtained for the side tumbling stability and the puncture stability about the loading, the height of the loading centroid and the athwartships angle of the road, and the roll stability of the typical trailer, together with the corresponding curves.
    2011, 33(5):  72-73.  doi:10.6052/1000-0879-lxysj2011-032
    Abstract ( 845 )   PDF (5834KB) ( 467 )  
    2011, 33(5):  63-64.  doi:10.6052/1000-0879-lxysj2011-023
    Abstract ( 1021 )   PDF (5196KB) ( 884 )  
    2011, 33(5):  33-37.  doi:10.6052/1000-0879-lxysj2011-060
    Abstract ( 756 )   PDF (8989KB) ( 367 )  
    The symmetrical hysteretic nonlinearity system of RC structures with clearance crack is studied with a piecewise linear symmetrical hysteretic model. With the equivalent linearizaion approximate method, the equivalent damping and stiffness coefficients are calculated, and the equivalent linearizaion dynamic response of symmetrical hysteretic system is obtained. Comparisons are made between chaotic dynamic characteristics of chaotic vibro-impact systems with and without clearance crack. The results show that vibro-impact system without clearance crack is in a periodic motion; however, vibro-impact system with clearance crack is often in a chaotic motion, and with parameters in a particular range, the system is definitely in disorderly chaotic motion.
    2011, 33(5):  65-66.  doi:10.6052/1000-0879-lxysj2011-056
    Abstract ( 859 )   PDF (5149KB) ( 719 )  
    2011, 33(5):  61-62.  doi:10.6052/1000-0879-lxysj2011-068
    Abstract ( 833 )   PDF (4339KB) ( 439 )  
    By using the superposition principle of motions to decompose the projectile motion of the shot into a combination of two rectilinear motions, this paper proposes a new simple method to analyze the optimum release angle in shot put. The results are compared with those obtained by the traditional methods under two different conditions.
    DYNAMICS OF BASEBALL BAT
    Tang Luming Shui Xiaoping Shen Zhenxing
    2011, 33(5):  57-60.  doi:10.6052/1000-0879-lxysj2011-103
    Abstract ( 1146 )   PDF (7166KB) ( 610 )  
    In this paper, a relationship is obtained between the best hitting point of the baseball and the natural frequency and the modal shape of the baseball bat through a finite element model. Assume that the material of the baseball bat model is linear elastic, and both ends of the bat are traction free, as is consistent with the actual situation, then we may discuss the `corking' of the bat (digging a cylindrical cavity at the head of the bat, putting a cork or rubber into it, and then covering it with a wood cap) or the use of metal bats. Both methods can increase the effect of `the sweet point'. The validity of the model is verified by experiments.
    DYNAMIC CALIBRATION OF THIN-FILM MANGANIN PIEZORESISTANCE GAUGES
    Wang Changli Li Yan Liu Wenxiang Wang Dengwang Li Jie Wang Hui
    2011, 33(5):  46-50.  doi:10.6052/1000-0879-lxysj2011-041
    Abstract ( 759 )   PDF (8949KB) ( 826 )  
    This paper discusses the dynamic calibration technique for a new kind of thin-film manganin piezoresistance gauge by means of planar impact. The calibration experiments were carried out on a $\Phi $130\,mm gas-gun, with PMMA, Cu, and W as the materials of flyers and targets. The compact pressure was obtained in the range from 0.66\,GPa to 25.4\,GPa by the planar impact in different velocities. The experimental data are correlated by two kinds of methods, that is, geometry relation calibration and $D$-$u$ relation calibration. The dynamic calibration and relation curves are obtained.
    2011, 33(5):  28-32.  doi:10.6052/1000-0879-lxysj2011-017
    Abstract ( 771 )   PDF (8837KB) ( 404 )  
    An improved particle swarm optimization (PSO) method is proposed for the position optimization of actuators in vibration control problems. The system energy is adopted as the optimal index in the method. A numerical example is calculated by the improved method and other optimal techniques. The results optimized by various methods are in good agreement, and the improved PSO method is more efficient for solving multi-position optimization problems of actuators in vibration control problems.
    2011, 33(5):  16-20.  doi:10.6052/1000-0879-lxysj2010-525
    Abstract ( 941 )   PDF (8865KB) ( 609 )  
    Based on the design methods and the interaction characteristic of anti-slide pile and soil, a program of contact FEM using contact element is designed. Then, the calculation model is set up; and the bending moment, displacement along the pile with different cable’s prestress and different thrusts are calculated. Finally, the optimum presstress is discussed, which has a significant guide to the landslide control.
    2011, 33(5):  42-45.  doi:10.6052/1000-0879-lxysj2010-402
    Abstract ( 730 )   PDF (6522KB) ( 442 )  
    Based on a method of measuring tiny deformation by scanning Fabry-Perot interferometer, a testing system for piezoelectric constants is proposed. In this paper, we discuss the measuring principle, the measuring apparatus, and experimental results for a typical example. The piezoelectric constants obtained by this method are in very good agreement with the experiment data by the IEEE method.
    Around the mechanics
    2011, 33(5):  1-7.  doi:10.6052/1000-0879-lxysj2011-300
    Abstract ( 1208 )   PDF (13325KB) ( 644 )  
    A modeling approach to the time-dependent behavior of salt rock is of special interest for many underground engineering such as underground storage of natural gas and crude oil, a permanent repository of CO$_{2}$ and high-level radioactive nuclear wastes. With respect to the large deformation and even loss of effective storage volume of salt cavities in long-term service, the developments in researches on time-dependent behaviors of salt rocks are reviewed in this paper, including creep experimental studies, creep constitutive relations of salt rock and long-term stability of salt cavity. It is pointed out that the combination analysis of creep constitutive relation modeling and physical mechanism of damage growth in salt rock at the micro- and meso- scales is an attractive topic in rheology of salt rock.
    2011, 33(5):  8-11.  doi:10.6052/1000-0879-lxysj2011-134
    Abstract ( 984 )   PDF (6672KB) ( 756 )  
    Based on the concept of the total cyclic strain energy, a new model is developed to predict the fatigue life of materials. Its validity is tested by comparing the calculated results and testing data for 30CrMnSiA and AISI 4340 steels.
    2011, 33(5):  51-56.  doi:10.6052/1000-0879-lxysj2011-018
    Abstract ( 786 )   PDF (12177KB) ( 397 )  
    With the help of scanning electronic microscope and optical microscope, the micro-adhesive systems of house ants are observed and studied experimentally, especially for the adhesive mechanisms on clean glass sheets and the climbing behaviors on glass sheets or wax surfaces with different surface roughness or tilted angles. Experimental observations show that the adhesion of ants depends largely on an arolium, which can extend freely. The surface roughness and tilted angles of glass sheets have no obvious effects on ants' climbing behaviors. However, ants' adhesion ability decreases when the tilted angle of wax surface increases, and becomes invalid beyond a critical tilted angle.
    2011, 33(5):  21-27.  doi:10.6052/1000-0879-lxysj2011-086
    Abstract ( 875 )   PDF (14716KB) ( 427 )  
    The cleavage initiation of notched specimens of a low alloy hot rolled steel (16\,MnR) with carbides and inclusions at $-196^\circ$C and $-130{^\circ}$C is studied in this paper. The results of tensile tests, four point bending tests of single and double notched specimens, microscopic observations and finite element method calculations show that two types of cleavage initiation sites in notched specimens can be identified, one is related to the inclusions ahead of the notch root (IC type) and the others related to the inclusions located ahead of string cracks far from the notch root (SIC type). The types of initiation sites are influenced strongly by temperature, changing from IC type at $-196{^\circ}$C to SIC type at $-130{^\circ}$C. In both IC and SIC initiation mechanisms, the crack nucleation is induced by inclusions and the final fracture is controlled by the propagation of a ferrite grain-sized crack into the matrix grain. The cleavage fracture of IC initiation type in notched specimens can be described by a dual-criterion model, i.e. a critical plastic strain $\varepsilon_{\rm p} \ge \varepsilon_{\rm pc} $ for initiating a crack nucleus and a critical tensile stress $\sigma_{yy} \ge \sigma_{f}$ for its propagation. While for SIC initiation type, the dual-criterion model is to be modified with the expression of $\varepsilon_{\rm p} + \varepsilon _{\rm ps} \ge \varepsilon_{\rm pc}$ and $\sigma _{yy} +\sigma_{yy{\rm s}} \ge \sigma_{f}$.
    2011, 33(5):  12-15.  doi:10.6052/1000-0879-lxysj2011-237
    Abstract ( 986 )   PDF (8057KB) ( 580 )  
    In order to solve the problems of non-uniform cross-section in the practice of deviation control, typtical mechanical models of non-uniform stiffness are discussed in this paper. Based on the differential equations of deflection curve and conditions of continuity and boundary of non-uniform stiffness beam-column, the analytical calculation formulae for deflection and end slope angles of beam-column are derived. Furthermore, appling beam-column theory principle of superposition, the mechanical problems of bottom hole assembly (BHA) with downhole control tool acted by a transverse concentrated force and BHA with variable gauge stabilizer can be solved. Non-uniform stiffness beam-column theory has been successfully used in the mechanical analysis of BHA and it provides theory foundations for downhole control tool design, BHA optimization and deviation control operation.
    2011, 33(5):  67-69.  doi:10.6052/1000-0879-lxysj2010-263
    Abstract ( 1489 )   PDF (5297KB) ( 960 )  
    Work of external forces and potential energy are key concepts in elastic mechanics of continuum. But it is found by the author that the expressions of these concepts listed in some classic textbooks are not real, which is verified using theorem of strain energy and then explained with an example of 1 dimension spring. Then the definitions and the relationships of total potential energy, potential energy / work of external forces and the reserved forces are analyzed, which make it easily for the primer students to understand these concepts clearly. At last, an advice is given that it is proper and necessary to tell clearly the fact that the expressions above are not real.
    2011, 33(5):  95-97.  doi:10.6052/1000-0879-lxysj2011-258
    Abstract ( 1260 )   PDF (5083KB) ( 599 )  
    Based on the hypothesis that the changes of the growth line number of nautilus’s shell reflect the changes of the moon’s cycle around the earth as time goes by, we draw two conclusions by the method of extrapolation: 1 The distance between the earth and the moon at first when the moon revolves around the earth which capture it is one fifth of that today. 2 It has been 7×108 years since the moon was captured by the earth at first. These support helpful enlightenment for far study about relation between the earth and the moon.
    2011, 33(5):  76-78.  doi:10.6052/1000-0879-lxysj2011-153
    Abstract ( 852 )   PDF (5524KB) ( 631 )  
    the basic mechanics analysis of the present problems existing in the course examination and the recent mechanical test reform based the analysis of the present situation, according to the basic mechanics curriculum content more, class, the features of the class size, puts forward the basic mechanical test reform new ideas, and operation method, and points out that the basic mechanics should be fully reflected in the examination reform curriculum teaching requirements, and of course should serve for the teaching and learning benign promotion.
    2011, 33(5):  79-85.  doi:10.6052/1000-0879-lxysj2011-288
    Abstract ( 884 )   PDF (13808KB) ( 573 )  
    What is the use of laser texturing technology for rolls? What kind of roll need to texture? What are the advantages of laser texturing roll technology? What defects still exist? Why is there more long service life of laser textured roll? Which performances are improved the steel plate rolled by laser texturing roll? What are their mechanisms? In this paper, it is discussed and explained that the several basic problems of laser texturing roll technology, and pointed out the direction of further improvement.
    2011, 33(5):  86-87.  doi:10.6052/1000-0879-lxysj2011-381
    Abstract ( 1030 )   PDF (5965KB) ( 520 )  
    2011, 33(5):  88-89.  doi:10.6052/1000-0879-lxysj2011-354
    Abstract ( 989 )   PDF (5307KB) ( 957 )  
    2011, 33(5):  93-94.  doi:10.6052/1000-0879-lxysj2010-281
    Abstract ( 1149 )   PDF (5200KB) ( 718 )  
    A rope can be knotted on a distant pole by using a sandbag connected at its end. Spin the rope to enhance the sandbag’s velocity and throw it out; pull the rope tightly to induce the sandbag rotating downward when it flies over the pole; shorten the rotating radius of the sandbag when it closes to the lowest point with increased velocity from the gravity potential energy. The sandbag’s velocity increases with the radius shortening on the momentum equilibrium, and then the rope may mound on the pole. The friction between the rope and pole can provide a great magnitude of load capacity.