多功能电真空实验装置设计

设计了一套多功能电真空实验装置。该装置结构简单，操作方便，实验过程和结果易于观察，用较少的投资就能完成十个以上的真空实验。这些实验不仅涵盖了与真空技术有关的基础实验，而且还包涵了真空应用方面的提高实验，为真空专业以及相近专业提供了一个良好的实验平台。     

材料化学专业实验建设的探索与实践

文章介绍了材料化学专业实验课程教学的探索及实践建设。内容包括：实验课程建设,实验项目设计,实验平台构建,实验内容和高新仪器的引入等等。通过具体探索和实践,学生培养了实验兴趣,锻炼了操作技能,激发了创新动力,还为将来的科研或实践打下了基础。     

如何利用紫外分光光度法测定水中硝酸根离子

文章首先介绍了实验原理和需要使用的仪器和试剂,然后分析了测定实验的方法以及步骤,并对实验的精度进行了验证,在确保实验精度的前提下得出了实验结果。     

基于VRML-Java平台的工程图学网络实验系统研究与实现

对工程图学网络实验系统的设计进行了研究。针对工程图学实验的特点及对实验系统的要求,确定了实验系统基于VRML-Java的构建平台;深入分析探讨了系统中的实验立体构建方法,通过分析VRML场景中形体构造的原理,设计了实验系统的模型数据结构和模型实时变形时数据修改的算法;系统设计了具有较强交互性的操作界面,实现了一个基于Internet的工程图学实验系统。     

红珠实验软件的设计与开发

红珠实验是一个重要的质量管理学实验，本文在分析红实验软件的目标和需求基础上，对软件实验系统进行了设计，并原原实验加了人机工程学的反应时测试验。用Delphiclient/ServersSuite开发实现了单机版的实验系统。     

网络环境下的管理实验及其可拓相似建模方法

管理实验是管理研究的重要方法之一。文章介绍了管理实验的发展历程，分析了管理实验发展缓慢的两大原因，剖析了网络环境给管理实验发展带来的新契机，提出了管理实验的可拓相似建模方法，并介绍了该建模方法的基本思路。     

淡水中的声饱和及参量阵的实验研究

本文介绍了淡水中的声饱和实验及参量阵的测量。给出了实验方框图和结果，并将实验结果与理论计算进行了比较。此外，还对实验精度作了分析和讨论     

定位定向接收机校准技术研究

介绍了全球导航卫星系统的组成与应用,利用本实验室的短基线场,对定位定向接收机进行实际大地坐标的定位与定向校准实验。给出了实验原理、实验过程及实验结果;并通过仿真机产生标准信号对接收机进行校准实验,对两种校准实验结果进行比较,分析了影响因素。     

石墨炉原子吸收法测定水中镉含量研究浅析

本文阐述了石墨炉原子吸收法测定水中镉含量实验研究的基本原理，所需设备器材，实验试剂，实验注意事项及实验步骤，对影响实验准确度相关因素进行了探讨分析。     

竖直管蓄冰多孔介质局部自然对流的实验研究

根据目前缺乏对多孔介质局部非热平衡的自然对流传热实验研究现象,设计了对竖直管外蓄冰过程中多孔介质局部自然对流传热的实验装置,并对实验装置进行了验证。结果也证实了本实验装置的可行性及实验数据的准确性。     

Study on Reloading Stress Relaxation Behaviour for High Temperature Bolted Steel

Designing and maintenance of mechanical elements is very important to clarify the effect of retightening (reloading) on stress relaxation behaviour of high temperature bolts. Experiments of stress relaxation simulates the real engineering problem of the long-term loosening of tightened bolts and other fasteners. Stress relaxation curves for a bolted steel 25 NiCrMo 8 are analyzed at three levels of test temperature (400, 450 and 500°C). The effect of the specified relaxation stresses on the reloading stresses behaviour is studied using five levels of the specified relaxation stress ratio (0.9, 0.8, 0.7, 0.6 and 0.5). Discussions are made on the relation between the testing time at each cycle and the number of loading with the variable of the specified relaxation stress ratio and the test temperature. The plastic strains accumulated during the course of the testing are analyzed and calculated by using empirical equation. Moreover, the apparent activation energy of relaxation behaviour which is determined as a relation of the testing time and of the specified relaxation stress ratio can be calculated.     

Viscoplastic–plastic modelling of IN792

At high temperatures metallic materials behave in a viscous manner exemplified by strain rate dependence, stress relaxation and creep deformation. At low temperatures however, these effects are extremely small, and the behaviour is strain rate independent and shows no or very small relaxation effects. Finally there exists an intermediate region, in which the material behaviour is close to strain rate independent for high strain rates but at the same time shows time dependent inelastic effects, such as stress relaxation and creep. For IN792 this occurs at temperatures around 650 °C. The article describes the extension of a power-law viscoplastic model describing the behaviour of IN792 at 850 °C, also to describe the behaviour at 650 °C, by bounding the elastic–viscoplastic stress-space by a plastic yield surface. The model parameters have been estimated using data from creep test and tailored step relaxation tests, and the model fits well to both the step relaxation data aimed at resembling relevant component conditions and long term creep data.     

Characterization of mechanical relaxation processes

The experimental observation of power-law behaviour in the spectral response of dielectric relaxation has been extended to other relaxation processes, particularly mechanical loss. Examples of the power-law behaviour are given and summarized diagrammatically. It is shown that there is an essential difference between the magnitudes of the power-law exponents for mechanical and dielectric relaxation. A relationship between the two is proposed and shown to be experimentally valid.     

Cyclic deformation behaviour and morphology of polypropylene

The viscoelastic-plastic behaviour and stress relaxation in polypropylene after uniaxial simple tension or cyclic preloading are studied by an electrohydraulic, servo-controlled testing machine. The stress-strain curve data of simple tension at different strain rates show that the magnitude of stress depends strongly on strain rate. The stress relaxation behaviour after simple tension and cyclic preloading indicates complex features and reveals differences in the deformation of molecular chains in polypropylene subjected to different cyclic preloadings. The stress-strain curves and the stress relaxation curves under three mean strains are fairly different from each other. The microstructural changes in samples subjected to different cyclic preloadings were determined by scanning electron microscopy (SEM). The results of the stress-strain curves and the stress relaxation behaviour are discussed in comparison with the observation of SEM fractographs.     

Stress relaxation of high impact polystyrene

The stress relaxation behaviour of high impact polystyrene has been correlated with the microstructural changes observed in tensile tests. The inhomogeneity of plastic deformation, manifested as stress whitening, has been measured using microhardness tests. This method has been found to be sensitive to the amount of crazing in the material. The stress relaxation behaviour changed at the onset of crazing, but did not change appreciably as the volume fraction of crazes increased. An analysis of the relaxation in terms of a site population model based on White's approach suggests the macroscopic stress relaxation is related to the crazes in the boundary regions between the stress whitened and unwhitened material.     

New models to explain the compaction and relaxation behaviour of some pharmaceutical excipients submitted to low strain

Seven commercially available pharmaceutical excipients used for direct tableting were studied. Flowability, true and tap density, loss on drying, particle size, specific surface area and scanning electron micrographs were used to characterize these powders with low compaction pressures (lower than 10 MPa). The relaxation mode was analysed to describe the behaviour of each product under strain. Three new models are proposed to aid understanding the physical phenomena involved in the compaction phase, and the Peleg model was applied to the relaxation phase. The models were related with the physical properties measured, and illustrate the sliding friction, the viscoelastic behaviour and the aptitude of particles to fragment during compaction, as well as the elastic behaviour during the stress relaxation of powders.     

Relaxation in elastic and viscoelastic materials

The mechanical compliance and modulus retardation/relaxation functions are examined in terms of a general behaviour which contains more than one process. An analytical approach to the transformation in the anelastic response between the compliance and the modulus is derived and applied to a cooperative model of relaxation behaviour. In particular it is shown that mechanical viscoelasticity is equivalent to the anomalous low frequency dispersion process that has been observed in dielectrics containing quasifree charges. Comparison with published experimental data over a wide range of solid materials shows the validity of the cooperative model to mechanical relaxation.     

Constitutive equations of ageing polymeric materials

In a previous paper, a constitutive equation of relaxation behaviour of time-dependent chemically unstable materials has been developed by employing the irreversible thermodynamics of internal variables and Eyring's absolute reaction theory. In that paper, a theoretical expression for the effect of chemical crosslink density,v, on the relaxation rate has been developed. In this paper the creep behaviour of a network polymer undergoing a scission process has been developed. The temperature effect using the WLF equation on the coupled chemomechanical behaviour has also been incorporated into the equation.     

Experimental Study and Numerical Modelling of Creep and Stress Relaxation of Dielectric Elastomers

Dielectric elastomers (DEs) are gaining acceptance as potential actuator materials because of their exhibition of a large amount of deformation when stimulated by electrostatic forces. However, time‐dependent behaviour such as creep and stress relaxation still pose a great challenge for the design, modelling and control of the DE‐based actuators. In this work, attempts are made for experimental estimation and modelling of creep and relaxation properties of one of the most widely used dielectric acrylic elastomers, VHB 4910. Experimental investigation shows that the material possesses strong time‐dependent creep and stress relaxation. It has been shown that creep and stress relaxation characteristics vary with the holding stress and holding strain respectively. Creep and stress relaxation properties are also shown to depend on the number of cycles in the case of cyclic loading. Results also show that Findley's power law can successfully model the creep and stress relaxation behaviour of the VHB 4910 elastomer.     

Structural aspects of the ferroelectric phase transition in lanthanum-substituted lead titanate

The structural characteristics and ferroelectric phase transition behaviour of chemically derived lanthanum-substituted lead titanate powders have been investigated by high-temperature X-ray diffraction and differential scanning calorimetry. Using X-ray line profile analyses and precise lattice parameter determinations, the important influence of strain coupling through lanthanum/vacancy-induced defect fields on the first-order character of the ferroelectric phase transition was demonstrated. The relaxation of the lattice to the defects as observed in the X-ray measurements was correlated with the onset of diffuse phase transition behaviour revealed by the calorimetry experiments. The lattice relaxation mechanism was connected with the appearance of mesoscopic modulations of the ferroelectric domain structure, and with anomalies in the dielectric behaviour near the transition.