Etching technique for revelation of plastic deformation zone in low carbon steel

Abstract

In this study, an etching technique to detect the localised plastic deformation behaviour in a low carbon steel was developed. With this technique, etching with Fry solution under ultrasonic vibration was carried out on samples plastically deformed and then heated at 550°C for a certain period of time. The plastic zone was revealed by different degrees of etching in the plastically deformed and non-deformed regions; the plastic zone was found to be only slightly etched, whereas the other region was deeply etched. From the surface offset after etching, the deformation zone was found to be observable even at low magnification, such as 10 times. As the heating duration increased, the plastic zone became clearer. The mechanism for such an etching reaction is discussed on the basis of electrochemical analysis.     

Numerical modelling for rotational moulding with non-isothermal heating

Abstract

In the rotational moulding process, the internal air temperature has been widely recognised as a tool to predict an optimum cycle time. This paper presents a new numerical approach to predict the internal air temperature in a two-dimensional (2-D) static model without requiring the consideration of the tumbling motion of polymer powder. The initial non-isothermal heating of the static model is actually formed by two changeable plastic beds (stagnant and mixing beds), which represent the actual stagnant and mixing pools inside a rotating mould respectively. In the numerical approach, the lumped-parameter system and coincident node technique are proposed to incorporate with the Galerkin Finite Element Method in order to account for the complex thermal interaction of the internal air. It helps to overcome the difficulty of multidimensional static models in predicting an accurate internal air temperature during the heating stage of rotationally powdery plastic. Importantly, the predicted temperature profiles of the internal air, oven times for different part thicknesses and process conditions accord with the available experimental results.     

微胶囊技术在棉织物阻燃整理中的应用

以二乙烯三胺和环氧氯丙烷为原料,利用界面聚合的方法,制备了聚磷酸酯阻燃剂微胶囊,借助红外光谱仪、生物显微镜等对微胶囊制备的过程进行分析,确定了最佳制备条件,利用制备的阻燃剂微胶囊与丁烷四羧酸联用,对棉织物进行阻燃整理,对阻燃整理后棉织物进行了热分析(TG)和阻燃性能测试,阻燃性能优异.且织物白度和吸湿性保留率良好.     

Measurement of residual stresses in austenitic stainless steel weld joints using ultrasonic technique

Abstract

A methodology has been developed using a non-destructive ultrasonic technique for measuring surface/subsurface residual stresses in 7 mm thick AISI type 316LN stainless steel weld joints made by activated tungsten inert gas and multipass tungsten inert gas welding processes. Measurement of residual stresses using an ultrasonic technique is based on the effect of stresses on the propagation velocity of elastic waves. Critically refracted longitudinal L _CR wave mode was employed and accurate transit time measurements were made across the weld joints. Quantitative values of the longitudinal residual stresses across the weld joints were estimated from the measured transit times and predetermined value of acoustoelastic constant for AISI type 316LN stainless steel. The nature of the residual stress profiles and their variations across the two types of weld joints were compared and interpreted.     

42—THE ESTIMATION OF CROSS-LINKS IN WOOL FROM THE EXTENT OF SWELLING IN FORMIC ACID

An account is given of the application of a gravimetric method for measuring the extent of swelling of wool in formic acid to a series of wool samples containing decreasing amounts of randomly distributed disulphide bonds. In accordance with the Flory-Rehner equation, a linear relation was observed between disulphide content and V 5/3, where V is the volume of dry wool expressed as a fraction of the volume of swollen wool. This calibration curve was then used in conjunction with swelling data to assess the number of cross-links introduced on the treatment of wool with formaldehyde and other bifunctional reagents. The method is particularly useful for ranking in order relatively high levels of cross-linking.     

Atom probe characterisation of high temperature materials

Abstract

An atom probe is capable of quantitatively analysing materials at the atomic level. Modern atom probes are derived from the field ion microscope, and are coupled with time-of-flight mass spectrometers, permitting identification of individual atoms. The introduction of position-sensitive detectors enables the reconstruction of a small volume of the sample owing to simultaneous determination of the x, y, and zcoordinates and the mass to charge ratios of individual atoms. This paper focuses on the application of atom probe techniques to the microstructural analysis of high temperature materials. Illustrations include carbide precipitation in creep resistant power plant steels and analyses of model and commercial multicomponent nickel based superalloys. It is demonstrated that atom probe field ion microscopy and atom probe tomography are valuable techniques in the development and understanding of technologically important alloys for high temperature service.     

Hydrophobically Functionalized Chitosan Particles

Particles of chitosan have a very polar surface, and thus they are easily wetted by water and also dissolve in acidic media. The hydroxyl and amino groups offer a high potential for grafting reactions. Aldehydes and carbonic acid derivatives were covalently grafted, preferably onto the amino groups. The reactions were carried out in solution as homogeneous phase reactions as well as on the particle surfaces as heterogeneous phase reactions. Covalently bonded alkyl chains impart the chitosan molecules with hydrophobic properties. We employed different methods such as NMR, XPS, elemental analysis and FT-IR spectroscopy to study the reactions and to estimate the degree of functionalization. The wetting behavior of the particles was investigated by a modified Wilhelmy technique, where an adhesive tape completely coated with the particles was dipped in water. Some of the samples having a high degree of functionalization showed super-hydrophobic surface properties. The observed super-hydrophobic effect results from a combination of the hydrophobic properties of the modified particles and the roughness of the particle coating.     

Through thickness residual stresses in large rolls and sleeves for metal working industry

Abstract

There is little experimental knowledge about the initial state of through thickness residual stresses in rolls and sleeves for the steel rolling industry. This is surprising bearing in mind the impact that residual stress has on the performance of the roll and sleeve materials in the highly aggressive loading environments of the metal working industry. Previous work has been confined to measurement of very near surface residual stresses and numerical predictions of residual stress distributions. In the present paper through thickness residual stress measurements were carried out using a deep hole drilling technique on a series of rolls and sleeves representative of those used in the rolling industry. Different features of the manufacturing processes used in their production are shown to influence the magnitude and distribution of the residual stresses. It is also shown that the measurements can be used, together with a finite element analysis, to determine the volumetric distribution of the residual stresses.     

The Photography of Radioactive Materials

This paper discusses some or the many problems peculiar to the photography or radioactive materials. Specialized apparatus and techniques are described, such as telephotography via mirrors, illumination systems and macro techniques.