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10 December 2009, Volume 31 Issue 6
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    Education Study
    2009, 31(6):  80-81.  doi:10.6052/1000-0879-2008-151
    Abstract ( 1088 )   PDF (667KB) ( 535 )  
    Application study
    2009, 31(6):  35-41.  doi:10.6052/1000-0879-2008-172
    Abstract ( 1522 )   PDF (2268KB) ( 616 )  
    The 3-D nonlinear meso-mechanics of the concrete column wrapped with tubular was numerically studied in this paper, including the tube of variable elasticity modulus, taking the concrete as a type of three-phase composite material composed of mortar matrix , aggregates and bonds connecting the matrix and aggregates. In order to establish the numerical model, a program is used to define the random coordinate of the aggregates. With the results, we discussed the relationship between the failure of the concrete column wrapped with different material(PE, HDEP, PVC, Steel etc.) and the meso-mechanics of the different interior material(mortar matrix, aggregates and bonds connecting the matrix and aggregates). The results achieved could be a good referee to the practical application of concrete column wrapped with tube.
    CONSTITUTIVE RELATION AND COMPRESSIVE STRENGTH OF OCEANIC ICE
    Zhang Xiao-Zhong Ruoyang BAI Ai-min JIANG
    2009, 31(6):  50-52.  doi:10.6052/1000-0879-2008-267
    Abstract ( 1307 )   PDF (547KB) ( 703 )  
    A mathematical model based on the actual state of oceanic ice is established. According to this model, the constitutive relation is derived and compared with the experiment of uniaxial anti-pressure strength. The formule for the maximum anti-pressure strength is derived to describe the relations between compressive strength and strain rate of oceanic ice, and is verified by tests. This formula can be used for related structural analysis.
    Education Study
    2009, 31(6):  69-70.  doi:10.6052/1000-0879-2008-305
    Abstract ( 1496 )   PDF (489KB) ( 596 )  
    In traditional teaching of force method in structure mechanics, it is needed to carry on at the same basic structure regardless of establishment of fundamental equation or the solution of coefficients and the free items in equations. However, it is shown in this paper that force method could simultaneously solve questions of statically indeterminate structures based on two different basic structures and simplify the calculation process. Through calculation and comparison, the physical and scientific significance are explained with overlay method when two basic structures selected are different. Using this method in teaching is helpful for students to understand the force method deeply.
    2009, 31(6):  71-73.  doi:10.6052/1000-0879-2008-320
    Abstract ( 1084 )   PDF (517KB) ( 602 )  
    Based on the review about the concept of member bar, some examples in classical textbooks were discussed. The results showed the necessity about standardized equilibrium analysis of load. On the other hand, the purpose about analytic type of member bar was investigated.
    2009, 31(6):  74-75.  doi:10.6052/1000-0879-2008-328
    Abstract ( 1132 )   PDF (300KB) ( 467 )  
    2009, 31(6):  75-76.  doi:10.6052/1000-0879-2008-356
    Abstract ( 1081 )   PDF (345KB) ( 647 )  
    Abstract:Visualizing the fluid object in question can directly observe the fluid flow status. According to the relative theory in fluid dynamics, this paper analyzes the following characteristic of solid tracer element which is used to display air current. With the white powder of MgCO3 as tracer element which is directly put into the air stream, the result of the experiment are compared with that of the theoretical analysis. The results show that it is an effective way to display the air current with powder of MgCO3 as tracer element directly put into the air stream, which has characteristic of good visualization and easy track.
    Application study
    2009, 31(6):  21-24.  doi:10.6052/1000-0879-2008-407
    Abstract ( 1149 )   PDF (928KB) ( 571 )  
    By using MTS series 815.02 model servo-controlled stiff rock mechanics testing system, the stress-strain characteristics of the sandstone specimen were studied in unloading process under tri-axial condition with different unloading rates. The relation between strength and unloading rate was analyzed and a formula was obtained. The fracture mechanism in unloading process was studied by observing the crack characteristics. The findings can provide some theoretical reference for engineering practice when analyzing the rock mass unloading problems.
    2009, 31(6):  30-34.  doi:10.6052/1000-0879-2008-418
    Abstract ( 1413 )   PDF (926KB) ( 714 )  
    The determination of equivalent shear modulus of concrete filled steel tube (CFST) by experiment is very difficult. A method based on finite element analysis is proposed in this paper to numerically calculate the shear modulus. Based on the analysis of various factor, regressive formulas for equivalent shear modulus of concrete filled circular steel tube and concrete filled square steel tube are obtained. Comparisons of different methods for shear modulus of CFST are made and their different results are discussed. The results show that the method of finite element analysis is more reasonable with respect to the equivalent shear modulus of composite members.
    2009, 31(6):  42-45.  doi:10.6052/1000-0879-2008-539
    Abstract ( 1163 )   PDF (743KB) ( 495 )  
    In the cylindrical-cavity-expansion-theory-based penetration calculation for all types of projectile bodies and the concrete targets, only the static parameters of the concrete targets are taken into consideration, which does not account faithfully for the dynamic interaction between the projectiles and the targets. Therefore, the cylindrical-cavity-expansion-theory-based model is modified by taking account of the dynamic response of the targets under dynamic loads and their strain rate sensitivity. Case studies show that the modified model can produce calculation results more consistent with the experimental data.
    2009, 31(6):  63-66.  doi:10.6052/1000-0879-2008-562
    Abstract ( 987 )   PDF (802KB) ( 869 )  
    Stretcher is an important medical apparatus in field rescue operations, but for a common stretcher, it is not easy to keep its board horizontal when used on slopes (such as on stairs or steep mountain roads). This paper studies the parallel four-bar mechanism and its mechanical characteristics. Based on the analysis, a new type medical stretcher can be designed. This new type stretcher can keep its board and handles horizontal not only on a plain ground, but also on slope situations, with easy operations. This apparatus holds a bright prospect for its applications in the field rescue operations.
    STUDY ON MECHANICAL MODEL OF SETTLEMENT IN MUNICIPAL SOLID WASTE LANDFILL
    sun hong-jun li liang xuezhi wang lihong zhao
    2009, 31(6):  53-56.  doi:10.6052/1000-0879-2008-592
    Abstract ( 1251 )   PDF (771KB) ( 560 )  
    Landfill is a cost-effective method for urban waste disposal. Prediction of landfill settlement is the most essential issue in order to increase the municipal solid waste landfill capacity and improve the utilization of landfill. In this paper, a mechanical model of the settlement under the combined action of load, creep and biodegradation is proposed based on the settlement mechanism of municipal solid waste landfill and the relationship between stress and strain in classical mechanics. The expression of yield surface stress increment is obtained under load, creep and biodegradation. The example computed of landfill settlement shows that the model is satisfactory in forecasting.
    2009, 31(6):  17-20.  doi:10.6052/1000-0879-2008-625
    Abstract ( 1244 )   PDF (896KB) ( 505 )  
    The rheological characteristics of suspensions of microencapsulated phase change materials (MPCM) in the presence of nano-particles are investigated experimentally. Such type of novel suspensions is found to behave as Newtonian fluids under relevant conditions studied in this work. Temperature affects the viscosity of suspensions significantly, and viscosity of base liquid and that of suspensions change with temperature in a similar fashion. It is also found that viscosity of the suspensions increases in a nonlinear fashion with increasing concentration of nano-particles. The increment of viscosity is about 23{\%} when the mass concentration of nano-particles is up to 5%.
    2009, 31(6):  46-49.  doi:10.6052/1000-0879-2009-094
    Abstract ( 1213 )   PDF (1350KB) ( 629 )  
    Parallel computations are needed for effectively analyzing the concrete-faced rockfill dam using 3D nonlinear finite element method. Parallelism is to be found during modeling stage and some neighbouring dam sections are made into a substructure. It is convenient and can satisfy the demands of the domain decomposition. A parallel multi-frontal code for COW is developed and applied to the numerical analysis of Xilongchi lower reservoir dam, an asphalt concrete faced rockfill dam, with the same result as in a serial calculation. From the speedup ratios and parallel efficiency, it is shown that the parallel multi-frontal method can be used to reliably analyze the concrete-faced rockfill dam and it is simple and easy to realize, without requiring an accessorial task assignment subroutine.
    Education Study
    2009, 31(6):  67-68.  doi:10.6052/1000-0879-2009-164
    Abstract ( 1344 )   PDF (670KB) ( 722 )  
    According to the official publication of the literature, from the teaching and exploration of the concept of reform, reform and innovation in teaching content, teaching methods Reform and the practice of reform and supporting the teaching assessment, teaching facilities and computer applications to improve the five areas, an overview of our country over the past 20 years experimental curriculum material mechanics theory and practice of teaching reform and put forward therecommendations of the author.
    Application study
    2009, 31(6):  25-29.  doi:10.6052/1000-0879-2009-183
    Abstract ( 1180 )   PDF (819KB) ( 667 )  
    Propagation of nonlinear waves in a fluid-filled thin elastic foundation is studied in this paper. The material of the tube is assumed to be linear elastic, the reaction of foundation is calculated based on Winkler model, and the fluid is incompressible and inviscid. Initially, the tube subjected to a uniform inner pressure $P_0 $ is in a state of static equilibrium. The dynamic displacement field and the variations of inner pressure and fluid velocity are considered as a disturbance superimposed on this static deformation. The nonlinear equations of motion are obtained by considering the mass conservation and the balance of linear momentum. With the reductive perturbation method, the KdV equation is derived in the longwave approximation. It is shown that the system can have a solitary wave solution.
    2009, 31(6):  57-62.  doi:10.6052/1000-0879-2009-245
    Abstract ( 1228 )   PDF (898KB) ( 550 )  
    This paper briefly describes the structure and principle of the cable type derrick crane with a drag rope operating with the hoist rope for increasing the working range, The loads on its main components are analyzed and the formulas are obtained for determining their loads. The calculation and comparison indicates that pulling the hoist rope in an inclined angle within the permitted limits in operation is feasible and safe. The appropriate parameters for this kind of cranes are suggested for design.
    Review
    A REVIEW ON FROZEN ROCK MECHANICS
    Yang Geng-she
    2009, 31(6):  9-16.  doi:10.6052/1000-0879-2009-306
    Abstract ( 1567 )   PDF (2084KB) ( 853 )  
    To meet the demands of construction of infrastructural facilities, the study on frozen rock mechanics in cold regions is necessary. The research progress of rock mechanics under the frost and thaw conditions at home and abroad is reviewed in this paper, with emphasis on the main achievements of authors and colleagues on frozen rock mechanics in recent years. Some issues that are worth further studies are pointed out.
    Interesting mechanics story
    2009, 31(6):  95-96.  doi:10.6052/1000-0879-2009-398
    Abstract ( 1236 )   PDF (349KB) ( 614 )  
    Review
    2009, 31(6):  1-8.  doi:10.6052/1000-0879-2009-469
    Abstract ( 1320 )   PDF (1635KB) ( 738 )  
    Auto-ignition is an essential phenomenon in engine combustion process, which is controlled by chemical kinetics. The concept of knock integral approach proposed by Lenvingood and Wu is verified by the author's research on sketch kinetics of n-heptane. It is shown that during the auto-ignition of fuel, the radical OH plays an important role. Only if the heat release and CO in the low temperature reaction are accumulated to a certain level, at which the reaction H+O$_{2}$ = O+OH can take place and the concentration of radical OH increases rapidly to transfer CO into CO$_{2}$ and with more heat release, the auto-ignition occurs. The advanced combustion technology based on the concept of auto-ignition control in engines is discussed in this paper.
    Mechanicist
    2009, 31(6):  82-83.  doi:10.6052/1000-0879-2009-470
    Abstract ( 1413 )   PDF (220KB) ( 582 )  
    2009, 31(6):  82-82.  doi:10.6052/1000-0879-2009-471
    Abstract ( 1373 )   PDF (472KB) ( 562 )  
    Education Study
    2009, 31(6):  69-70.  doi:10.6052/1000-0879-lxysj2008-305
    Abstract ( 1355 )  
    In traditional teaching of force method in structure mechanics, it is needed to carry on at the same basic structure regardless of establishment of fundamental equation or the solution of coefficients and the free items in equations. However, it is shown in this paper that force method could simultaneously solve questions of statically indeterminate structures based on two different basic structures and simplify the calculation process. Through calculation and comparison, the physical and scientific significance are explained with overlay method when two basic structures selected are different. Using this method in teaching is helpful for students to understand the force method deeply.
    2009, 31(6):  71-73.  doi:10.6052/1000-0879-lxysj2008-320
    Abstract ( 1032 )  
    Based on the review about the concept of member bar, some examples in classical textbooks were discussed. The results showed the necessity about standardized equilibrium analysis of load. On the other hand, the purpose about analytic type of member bar was investigated.
    2009, 31(6):  75-76.  doi:10.6052/1000-0879-lxysj2008-356
    Abstract ( 1036 )  
    Abstract:Visualizing the fluid object in question can directly observe the fluid flow status. According to the relative theory in fluid dynamics, this paper analyzes the following characteristic of solid tracer element which is used to display air current. With the white powder of MgCO3 as tracer element which is directly put into the air stream, the result of the experiment are compared with that of the theoretical analysis. The results show that it is an effective way to display the air current with powder of MgCO3 as tracer element directly put into the air stream, which has characteristic of good visualization and easy track.
    2009, 31(6):  67-68.  doi:10.6052/1000-0879-lxysj2009-164
    Abstract ( 1275 )  
    According to the official publication of the literature, from the teaching and exploration of the concept of reform, reform and innovation in teaching content, teaching methods Reform and the practice of reform and supporting the teaching assessment, teaching facilities and computer applications to improve the five areas, an overview of our country over the past 20 years experimental curriculum material mechanics theory and practice of teaching reform and put forward therecommendations of the author.
    Mechanicist
    2009, 31(6):  82-83.  doi:10.6052/1000-0879-lxysj2009-470
    Abstract ( 1306 )  
    Interesting mechanics story
    2009, 31(6):  95-96.  doi:10.6052/1000-0879-lxysj2009-398
    Abstract ( 1221 )  
    Application study
    2009, 31(6):  50-52.  doi:10.6052/1000-0879-lxjzJ2008-064
    Abstract ( 1219 )  
    In this paper, on the basis of the former experiments on the mechanics of ice, a mathematical model relatively consistent with the actual state of oceanic ice is established. According to this model, the constitute relation is derived and compared with the experiment of uniaxial anti-pressure intensity. The maximum anti-pressure intensity formula is established which describes the relations between compressive strength and strain rate of oceanic ice. This curve and other scholars have made the biggest test compressive strength and strain-rate trends in the relationship between the curves match that this formula is correct. This formula for the structure of the anti-ice oceans provide a theoretical basis for calculating.
    2009, 31(6):  35-41.  doi:10.6052/1000-0879-lxysj2008-172
    Abstract ( 1460 )  
    The 3-D nonlinear meso-mechanics of the concrete column wrapped with tubular was numerically studied in this paper, including the tube of variable elasticity modulus, taking the concrete as a type of three-phase composite material composed of mortar matrix , aggregates and bonds connecting the matrix and aggregates. In order to establish the numerical model, a program is used to define the random coordinate of the aggregates. With the results, we discussed the relationship between the failure of the concrete column wrapped with different material(PE, HDEP, PVC, Steel etc.) and the meso-mechanics of the different interior material(mortar matrix, aggregates and bonds connecting the matrix and aggregates). The results achieved could be a good referee to the practical application of concrete column wrapped with tube.
    2009, 31(6):  21-24.  doi:10.6052/1000-0879-lxysj2008-407
    Abstract ( 1088 )  
    By using MTS series 815.02 model servo-controlled stiff rock mechanics testing system, the stress-strain characteristics of the sandstone specimen were studied in unloading process under tri-axial condition with different unloading rates. The relation between strength and unloading rate was analyzed and a formula was obtained. The fracture mechanism in unloading process was studied by observing the crack characteristics. The findings can provide some theoretical reference for engineering practice when analyzing the rock mass unloading problems.
    2009, 31(6):  30-34.  doi:10.6052/1000-0879-lxysj2008-418
    Abstract ( 1322 )  
    The determination of equivalent shear modulus of concrete filled steel tube (CFST) by experiment is very difficult. A method based on finite element analysis is proposed in this paper to numerically calculate the shear modulus. Based on the analysis of various factor, regressive formulas for equivalent shear modulus of concrete filled circular steel tube and concrete filled square steel tube are obtained. Comparisons of different methods for shear modulus of CFST are made and their different results are discussed. The results show that the method of finite element analysis is more reasonable with respect to the equivalent shear modulus of composite members.
    2009, 31(6):  42-45.  doi:10.6052/1000-0879-lxysj2008-539
    Abstract ( 1094 )  
    In the cylindrical-cavity-expansion-theory-based penetration calculation for all types of projectile bodies and the concrete targets, only the static parameters of the concrete targets are taken into consideration, which does not account faithfully for the dynamic interaction between the projectiles and the targets. Therefore, the cylindrical-cavity-expansion-theory-based model is modified by taking account of the dynamic response of the targets under dynamic loads and their strain rate sensitivity. Case studies show that the modified model can produce calculation results more consistent with the experimental data.
    2009, 31(6):  63-66.  doi:10.6052/1000-0879-lxysj2008-562
    Abstract ( 926 )  
    Stretcher is an important medical apparatus in field rescue operations, but for a common stretcher, it is not easy to keep its board horizontal when used on slopes (such as on stairs or steep mountain roads). This paper studies the parallel four-bar mechanism and its mechanical characteristics. Based on the analysis, a new type medical stretcher can be designed. This new type stretcher can keep its board and handles horizontal not only on a plain ground, but also on slope situations, with easy operations. This apparatus holds a bright prospect for its applications in the field rescue operations.
    2009, 31(6):  53-56.  doi:10.6052/1000-0879-lxysj2008-592
    Abstract ( 1215 )  
    Landfill is a cost-effective method for urban waste disposal. Prediction of landfill settlement is the most essential issue in order to increase the municipal solid waste landfill capacity and improve the utilization of landfill. In this paper, a mechanical model of the settlement under the combined action of load, creep and biodegradation is proposed based on the settlement mechanism of municipal solid waste landfill and the relationship between stress and strain in classical mechanics. The expression of yield surface stress increment is obtained under load, creep and biodegradation. The example computed of landfill settlement shows that the model is satisfactory in forecasting.
    2009, 31(6):  17-20.  doi:10.6052/1000-0879-lxysj2008-625
    Abstract ( 1177 )  
    The rheological characteristics of suspensions of microencapsulated phase change materials (MPCM) in the presence of nano-particles are investigated experimentally. Such type of novel suspensions is found to behave as Newtonian fluids under relevant conditions studied in this work. Temperature affects the viscosity of suspensions significantly, and viscosity of base liquid and that of suspensions change with temperature in a similar fashion. It is also found that viscosity of the suspensions increases in a nonlinear fashion with increasing concentration of nano-particles. The increment of viscosity is about 23{\%} when the mass concentration of nano-particles is up to 5%.
    2009, 31(6):  46-49.  doi:10.6052/1000-0879-lxysj2009-094
    Abstract ( 1154 )  
    Parallel computations are needed for effectively analyzing the concrete-faced rockfill dam using 3D nonlinear finite element method. Parallelism is to be found during modeling stage and some neighbouring dam sections are made into a substructure. It is convenient and can satisfy the demands of the domain decomposition. A parallel multi-frontal code for COW is developed and applied to the numerical analysis of Xilongchi lower reservoir dam, an asphalt concrete faced rockfill dam, with the same result as in a serial calculation. From the speedup ratios and parallel efficiency, it is shown that the parallel multi-frontal method can be used to reliably analyze the concrete-faced rockfill dam and it is simple and easy to realize, without requiring an accessorial task assignment subroutine.
    2009, 31(6):  25-29.  doi:10.6052/1000-0879-lxysj2009-183
    Abstract ( 1108 )  
    Propagation of nonlinear waves in a fluid-filled thin elastic foundation is studied in this paper. The material of the tube is assumed to be linear elastic, the reaction of foundation is calculated based on Winkler model, and the fluid is incompressible and inviscid. Initially, the tube subjected to a uniform inner pressure $P_0 $ is in a state of static equilibrium. The dynamic displacement field and the variations of inner pressure and fluid velocity are considered as a disturbance superimposed on this static deformation. The nonlinear equations of motion are obtained by considering the mass conservation and the balance of linear momentum. With the reductive perturbation method, the KdV equation is derived in the longwave approximation. It is shown that the system can have a solitary wave solution.
    2009, 31(6):  57-62.  doi:10.6052/1000-0879-lxysj2009-245
    Abstract ( 1139 )  
    This paper briefly describes the structure and principle of the cable type derrick crane with a drag rope operating with the hoist rope for increasing the working range, The loads on its main components are analyzed and the formulas are obtained for determining their loads. The calculation and comparison indicates that pulling the hoist rope in an inclined angle within the permitted limits in operation is feasible and safe. The appropriate parameters for this kind of cranes are suggested for design.
    2009, 31(6):  50-56.  doi:10.6052/1000-0879-lxysj2008-267
    Abstract ( 1206 )  
    A mathematical model based on the actual state of oceanic ice is established. According to this model, the constitutive relation is derived and compared with the experiment of uniaxial anti-pressure strength. The formule for the maximum anti-pressure strength is derived to describe the relations between compressive strength and strain rate of oceanic ice, and is verified by tests. This formula can be used for related structural analysis.
    Review
    2009, 31(6):  9-16.  doi:10.6052/1000-0879-lxysj2009-306
    Abstract ( 1448 )  
    To meet the demands of construction of infrastructural facilities, the study on frozen rock mechanics in cold regions is necessary. The research progress of rock mechanics under the frost and thaw conditions at home and abroad is reviewed in this paper, with emphasis on the main achievements of authors and colleagues on frozen rock mechanics in recent years. Some issues that are worth further studies are pointed out.
    2009, 31(6):  1-8.  doi:10.6052/1000-0879-lxysj2009-469
    Abstract ( 1277 )  
    Auto-ignition is an essential phenomenon in engine combustion process, which is controlled by chemical kinetics. The concept of knock integral approach proposed by Lenvingood and Wu is verified by the author's research on sketch kinetics of n-heptane. It is shown that during the auto-ignition of fuel, the radical OH plays an important role. Only if the heat release and CO in the low temperature reaction are accumulated to a certain level, at which the reaction H+O$_{2}$ = O+OH can take place and the concentration of radical OH increases rapidly to transfer CO into CO$_{2}$ and with more heat release, the auto-ignition occurs. The advanced combustion technology based on the concept of auto-ignition control in engines is discussed in this paper.