测试方法对聚合物玻璃化温度的影响

选取环氧树脂固化物为样品,分别采用DSC法和DMA法测定了其玻璃化转变温度。结果表明,玻璃化转变温度随测定方法和条件的不同而变化,因此,在给出某种材料的玻璃化转变温度时,必须注明测定方法和条件。

聚酯纤维的热分析

采用差式扫描量热法（ＤＳＣ）和热机械分析法（ＴＭＡ），对聚酯纤维在各个加工阶段的温度、张力等变化进行了实验及分析，从中得出的结论对实际生产具有指导作用。

凝胶／聚乙烯醇混合生物降解膜的热机械性能

用差示扫描量热法（DSC）和动力-机械特性分析法（DMA）讨论了聚乙烯醇（PVA）浓度对凝胶／PVA混合薄膜热、粘弹性能的影响。先扫描混合薄膜，后在116℃-134℃的温度下熔解结晶部分，在所得DSC曲线上可观察到43℃和49℃间有一个玻璃化点，但是用DMA分析结果表明，含10％PVA的薄膜在tanδ光谱上仅有一个峰，随着PVA浓度的增加，动力tanδ光谱上会出现两个峰，表明有两个玻璃化温度Tg。并成功地应用Gordon和Taylor模块将Tg做成混合膜组成的关联函数，测出k=7．47，在DMA频率实验中，该光谱表明储能模量随温度的升高而降低，用TTS（Tr=100℃）原理可得到PVA／凝胶薄膜叠加曲线，用WLF模块测量常数C1和C2,这些常数随混合物中PVA浓度的增加而增大：C1=49—66，C2=463—460，它们可用来计算在玻璃化温度Tg下混合膜的自由体积份数和高于Tg时的热膨胀系数。

Simulation and analysis of resin flow in injection machine screw

A method with simulation and analysis of the resin flow in a screw is presented to ease the control of some problems that may affect the efficiency and the quality of the product among existing screws in an injection machine. The physical model of a screw is established to represent the stress, the strain, the relationship between velocity and stress, and the temperature of the cells. In this paper, a working case is considered where the velocity and the temperature distributions at any section of the flow are obtained. The analysis of the computational results shows an ability to master various parameters depending on the specifications.

Kinematic Characteristics Analysis of 3-PRS Parallel Manipulator

The 3-PRS parallel mechanisms,whose kinematic chain is connected by prismatic joint P,revolute joint R and spherical joint S,have two rotational and one translational DOF.But the DOF of 3-PRS parallel mechanism cannot be explained by the Grubler-Kutzbach method or Herve method.To illuminate the special kinematic characteristics of 3-PRS parallel mechanism,a novel analytical approach is proposed in this paper.All the feasible instantaneous motions of 3-PRS mechanism are studied by using this method.The analysis of kinematic characteristics of 3-PRS mechanism help to understand the mechanism and estimate the motion capacity of mechanism.Finally,it is also helpful to optimize the topology of the mechanism and the trajectory for desired performance.

Mechanical analysis on deformation of surrounding rock with road-in packing of gob-side entry retaining in fully-mechanized sub-level caving face

Based on the movement regularity of surrounding rock with road-in packing of gob-side entry retaining in fully-mechanized sub-level caving face(RPGERFCF),the me- chanical model of its surrounding rock was established and the calculating formulas of the deformation of the roof,coal wall and filling body were attained.By the mechanical analy- sis to the deformation of the surrounding rock of RPGERFCF,the major factors influencing the deformation of the surrounding rock were found out and the technologic approaches reduced the deformation and enhanced the stability of the surrounding rock were put for- ward.Consequently,the scientific bases were provided for the stability control of the sur- rounding rock of RPGERFCF.

Extremum response surface method of reliability analysis on two-link flexible robot manipulator

In order to present a new method for analyzing the reliability of a two-link flexible robot manipulator,Lagrange dynamics differential equations of the two-link flexible robot manipulator were established by using the integrated modal method and the multi-body system dynamics method.By using the Monte Carlo method,the random sample values of the dynamic parameters were obtained and Lagrange dynamics differential equations were solved for each random sample value which revealed their displacement,speed and acceleration.On this basis,dynamic stresses and deformations were obtained.By taking the maximum values of the stresses and the deformations as output responses and the random sample values of dynamic parameters as input quantities,extremum response surface functions were established.A number of random samples were then obtained by using the Monte Carlo method and then the reliability was analyzed by using the extremum response surface method.The results show that the extremum response surface method is an efficient and fast reliability analysis method with high-accuracy for the two-link flexible robot manipulator.

Finite element analysis of dynamic response and structure borne noise of gearbox

A dynamic finite element method combined with finite element mixed formula for contact problem is used to analyze the dynamic characteristics of gear system. Considering the stiffness excitation, error excitation and meshing shock excitation, the dynamic finite element model is established for the entire gear system which includes gears, shafts, bearings and gearbox housing. By the software of I-DEAS, the natural frequency, normal mode, dynamic time-domain response, frequency-domain response and one-third octave velocity grade structure borne noise of gear system are studied by the method of theoretical modal analysis and dynamic response analysis. The maximum values of vibration and structure borne noise are occurred at the mesh frequency of output grade gearing.

Mechanical Analysis for Progressive Failure of Debris Landslide

It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands.

Morphology and Properties of Miktoarm Star Styrene-Butadiene Rubber

In order to obtain the optimized structure rubber, a novel miktoarm star styrene-butadiene rubber （MS- SBR） was initiated by a multifunctional macromolecular initiator with polydiene arm and Sn-C bond. The properties of MS-SBR were investigated with respect to the morphology, mechanical properties, and dynamic viscoelasticity in comparison with those of the blends, natural rubber （NR）/star styrene-butadiene random rubber （S-SBR） blend rubber and cis-l,4-polybutadiene rubber （cis-BR）/S-SBR blend rubber. The samples were analyzed using transmission elec- tron microscopy （TEM）, dynamic mechanical thermal analyzer （DMTA）, and mechanical properties test. The analy- sis results show that MS-SBR possesses the desired combination of low rolling resistance and high antiskid resistance, and is promising for application in high performance tire tread.

Analysis of Unbalances Forces Using Methods of Identification and Finite Elements

The study of damage in rotating machineries is of fundamental interest in the fields of machine and structure design. A rotating system, supported by bearings and under some dynamic conditions, can generate a variety of problems that are encountered in many different types of rotating machines. One of these problems is the unbalance due to non-homogeneous mass distribution along the shaft. One of the techniques which are widespread today is the identification of parameters and excitation forces that may well followed by monitoring the evolution and change of possible variations of these parameters. Although several methods for the identification of unbalance excitation force are available in the literature, none of them can be considered unrestricted to be applied for all rotating systems. In this study, two methodologies to identify unknown excitations, such as unbalance, have been proposed. This project refers to the analysis of unbalanced forces from displacement parameters and speed by using methods of identification by Fourier series and Legendre polynomials together with the finite element method, state observers in reasons of the problem of absence of signs of rotational displacement, bandpass filter were used to noise suppression of the data collected from the experimental part, Quasi-Newton method to minimize a function in which the bearing stiffness and its damping are unknowns, and also the experimental verification of the methodology, using for this system owned by a rotary mechanical vibrations of the Department of Mechanical Engineering of Faculty of Engineering, campus of llha Solteira.

热固性聚合物的交联密度测试方法研究进展

综述了热固性聚合物交联密度测定方法的研究进展,重点介绍了平衡溶胀法、应力-应变法、动态机械热分析法、流变法、核磁共振法5种常用方法。

A Comprehensive Evaluation Method for Kinematic Accuracy of Space Manipulator Based on Analytic Hierarchy Process

The kinematic accuracy of space manipulator determines whether the spacecraft performs normally or not. Problems pertaining to structural deformation have received increased attention in recent times. In the space manipulator systems, flexible arms and joints can induce drastic dynamic instabilities. In applications such as the space station, kinematic error due to structural deformation can jointly affect the performance characteristics. And it is crucial for accuracy control of space manipulator to establish a precision index. Here we analyze the dynamics characteristic of flexible space manipulator considering the hysteresis of harmonic reducer based on method of nonconstraint boundary modal. For the sake of describing the output accuracy, we integrate the method of analytic hierarchy process(AHP) to establish a comprehensive evaluation index. A numerical simulation is performed to analyze the nonlinear dynamic characteristics of space manipulator with harmonic reducer. With the analysis of accuracy assessment, the relation among the hysteresis angle, rigidity and output accuracy is revealed. Considering the elastic modulus of flexible space manipulator and the hysteresis angle of harmonic reducer, we conduct an evaluation of output characteristics of flexible space manipulator with the proposed comprehensive evaluation index. The accuracy evaluation of output characteristics based on the proposed comprehensive evaluation index is implemented in the initial stage of space manipulator's design, which can not only solve the problems existing in the design but also save cost savings for ground tests. The results can be used in designing and optimizing future space manipulators, which may provide valuable references for design and thermal control of the space manipulator.