The derivation of the equations of moderately thick plates by the method of successive approximations

In this article the equations of a moderately thick plate are derived by the method of successive approximations. The derived equations exactly satisfy all the elastostatic equations, the plate equilibrium equations and traction free face boundary conditions.     

Experimental investigation and 3D finite element prediction of the heat affected zone during laser assisted machining of Ti6Al4V alloy

An experimental study was conducted to characterize the heat affected zone produced when laser heating a Ti6Al4V alloy plate workpiece. The emissivity and absorptivity of the Ti6Al4V alloy were determined experimentally. A 3D transient finite element method for a moving Gaussian laser heat source was developed to predict the depth and width of the heat affected zone on the Ti6Al4V alloy workpiece. There was a close correlation between the experimental data and the simulation results. It was found that the depth and width of the heat affected zone were strongly dependent on the laser parameters (laser power, laser scan speed, the angle of incidence and the diameter of the laser spot) and material properties (thermal conductivity, specific heat and density). Parametric studies showed that the depth and width of the heat affected zone increased with an increase in the laser power and decreased with an increase of the laser spot size and the laser scan speed. The thermal model can be used to determine the laser parameters for a given cut geometry that will yield no residual heat affected zone in the material after cutting. This provides the basis to optimize and improve laser assisted machining technique.     

Experimental behaviour of the reverse channel joint component at elevated and ambient temperatures

The reverse channel connection appears to have the best combination of desirable features under fire loading: moderate construction cost, ability to develop catenary action and extremely high ductility through deformation of the web channel (Ding and Wang, 2007). This paper presents the results of an experimental investigation of a reverse channel component conducted at the University of Coimbra as part of the European RFCS COMPFIRE Project, the main focus of which is to characterise the behaviour of steel joints that connect steel beams to concrete-filled tubular columns under natural fire loading. A series of tensile and compressive tests at ambient and elevated temperatures was conducted. The purposes of the experimental tests were to characterise the strength, stiffness and ductility of this joint component and to establish a relationship between force, displacement and temperature.     

High-pressure liquid chromatography fingerprinting of petroleums and petroleum products

Combined GC/HPLC fingerprinting of petroleums and process streams derived therefrom gives detailed information on their constituents. The silica gel-heptane system affords separation into classes of hydrocarbons which, together with dual u.v. and R.I. modes of detection, gives abundant information on the composition of such samples. GC on a medium-efficiency SCOT column is used as a complementary technique only. Interpretations of HPLC chromatograms for samples ranging from gasolines to bitumens are given.     

Development of direct ELISA for the determination of 4-nonylphenol and octylphenol

Development of direct competitive enzyme-linked immunoadsorbent assays (ELISAs) based on polyclonal and monoclonal antibodies raised against 4-n-alkylphenol hapten mimics is described. A strong tendency to recognize 4-nonylphenol (NP) and 4-octylphenol (OP) as a total analyte amount was indicated by cross-reactivity pattern established for two polyclonal antibodies. These antibodies were employed for development of class-selective assays exhibiting IC(50) values around 40 microg.L(-1) for technical 4-NP. Specificity of the monoclonal antibody 4H6 and additional two polyclonal antibodies allowed sensitive detection of linear long-chain forms of 4-n-alkylphenols (4-n-AP). The assays incorporating these antibodies offer a potential for detecting the minor fraction of NP/OP isomer spectrum having IC(50) = 11.5 microg.L(-1) for 4-n-NP. No cross-reactivity interference was indicated for linear alkylbenzene sulfonates and phenolic compounds. To interpret the measured data in terms of analytical equivalents, a reliable relationship between the assay responses and AP content of contaminated samples should be verified and validated.     

The analysis of condensation products of 2,6-xylenol and formaldehyde in the presence of cresols

Methylenebisphenols, commonly used as antioxidants for polyolefines, are prepared by condensation of suitably alkylated phenols and formaldehyde in the presence of acid catalyst. Usually by-products are produced from the impurities in starting raw materials. In this work the condensation of 2,6-dimethylphenol with formaldehyde and the influence of cresols was studied. By-products, namely bisphenols and trisphenols were separated by means of gel chromatography and analyzed by reversed phase liquid chromatography, mass spectrometry and nuclear magnetic resonance.     

Diagnose von Korrosionsfällen an einer Saturationskolonne für Synthesegas

Diagnosis of case histories from a synthesis gas saturation column The saturation column, made of steel type 1Cr18Ni9Ti (wall thickness: 8 mm), in which the gas is cooled down to 240°C by a water jet and, simultaneously saturated with water vapour, failed after only 3000 hours' operation; the failure was attributable to a damaged footing tube. An analysis of the damaged parts suggested, that the main cause of the failure was not the design of the equidistant shells, i. e. the welding connection between the tubes and the two shells, which had originally been assumed to be faulty, but in a first line the material selection which was wrong in view of possible corrosion. The tensile stresses resulting from the rigid connection of the footing pipes are but one of the factors contributing to the development of stress corrosion cracking. This opinion concerning the reason of the first failure was confirmed when another failure occurred after another 1000 hours' operation of the column: a thorough inspection revealed some spots where stress corrosion cracking bad developed.