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Abstract: Kinetical, morphological and magnetic characteristics of thermally induced martensite in an Fe–30%Ni–3.6%Mo alloy has been studied by scanning electron microscopy, transmission electron microscopy and Mössbauer spectroscopy. Scanning electron microscope and transmission electron microscope observations revealed the occurrence of both athermal and isothermal martensitic transformation in the alloy. In addition, the magnetic properties of both the austenite and martensite phases were determined by the Mössbauer spectroscopy. The Mössbauer spectra showed a paramagnetic character for the austenite phase and an antiferromagnetic character for the martensite phase. [Copyright &y& Elsevier]

This paper presents experimental results obtained from the direct pull-out test using different types of rockbolts having different shape of lugs. These are smooth surface bars, ribbed bars, single conical lugged bars, double conical lugged bars and triple conical lugged bars. It is found that the failure mechanism of the conical lugged rock bolt is different from that of conventional rockbolts, in which the adhesion or the shear strength at the bolt–grout interface provides the load bearing capacity. From the results of experimental study, the use of the conical lugged rock bolts is suggested, because it provides a greater anchorage strength due to wedging effect that is a combination of the shear and compressive strength of the grouting material. [Copyright &y& Elsevier]

This paper represents the result of a project conducted with developing a safe, practical and economical support system for engineering workings. In rock engineering, untensioned, fully cement-grouted rock bolts have been used for many years. However, there is only limited information about the action and the pull-out load capacity of rock bolts, and the relationship between bolt–grout or grout–rock and the influence of the grout properties on the pull-out load capacity of a rock bolt. The effect of grout properties on the ultimate bolt load capacity in a pull-out test has been investigated in order to evaluate the support effect of rock bolts. Approximately 80 laboratory rock bolt pull-out tests in basalt blocks have been carried out in order to explain and develop the relations between the grouting materials and untensioned, fully grouted rock bolts. The effects of the mechanical properties of grouting materials on the pull-out load capacity of a fully grouted bolt have been qualified and a number of empirical formulae have been developed for the calculating of the pull-out load capacity of the fully cement-grouted bolts on the basis of the shear strength, the uniaxial compressive strength of the grouting material, the bolt length, the bolt diameter, the bonding area and the curing time of the grouting material. [Copyright &y& Elsevier]

Abstract: Kinetical, morphological, crystallographical and several thermal properties of thermally induced martensite in the austenite phase of Fe–30% Ni–5% Cu alloy were investigated. Scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) techniques were used during study. Kinetics of the transformation was found to be as athermal type. SEM and TEM observations revealed α′ (BCC) martensite formation in the austenite phase of alloy by thermal effect. These thermally induced α′ martensites exhibited a thin plate-like morphology with twinnings. [Copyright &y& Elsevier]

The petroleum industry spends millions of dollars each year to prevent and overcome sand control problems and their prediction has therefore become essential to minimize the adverse effects of sand production. This paper reviews existing experimental and modelling studies of the prediction of sand production. In experimental studies, the trapdoor system has been commonly used. The early experimental set-ups had a simple trapdoor configuration with a fluid inlet port to inject a single fluid to conduct qualitative tests. Other facilities were added over time, including facilities to conduct qualitative and quantitative tests, inject radial, axial and multiphase fluids and conduct tests in uniaxial and tri-axial stress environments. Experimental findings on sand production can be categorized into four different effects: the flowing fluid characteristics effect, the material characteristics effect, the loading effect, and the outlet size effect. However, the application of laboratory findings to field conditions has become doubtful due to the various assumptions used in laboratory studies, including the scaling down of the reservoir, the use of sieved river sands and/or synthetic samples, and the use of limited combinations of two-phase flows. In model development, some basic mechanisms have been recognized as responsible for sand production: shear and tensile failure, the critical pressure gradient and drawdown pressure, and erosion. Tensile failure occurs when the effective minimum principle stress applying on the rock mass reaches its tensile strength, and shear failure occurs when the applied stress on some planes in the wellbore area is higher than their bearing capacity. Reduction of reservoir pressure causes the effective hydrostatic stresses on it to be increased, breaking its pore structure, and the rock formation can be eroded internally and externally, producing sand by dynamic seepage drag forces. To date, both continuum and discrete element method (DEM) approaches have been considered in sand production models. Most approaches have been developed considering the hydro-mechanical or shear failure mechanisms and some have combined them. [ABSTRACT FROM AUTHOR]