bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis for inversion load and energy absorption of a circular tube
Authors: Kinkead A N 
Published: July 2007

The basic theoretical approach in the mechanics of external or inside-to-outside inversion of circular tubes is examined and extended by the introduction of two additional and previously unperceived sub-structural mechanisms. It is shown that these refinements when applied to published results for ductile aluminium tubing inverted, in a non-frictional process, furnish very encouraging correlations. Since this analysis is made on an ‘engineering plastic strain’ basis a supplementary calculation is made employing ‘pure plastic strain’ or ‘natural strain’ in the predominant sub-structural processes. The resulting comparisons have shown that for rigid/plastic material characteristics the simplification derived in the use of engineering strain does not introduce serious errors in the evaluation of the inversion load. Here it might be mentioned that in many of the cited papers on external inversion, although the initial equations are set up in pure plastic strain terms, frequently the ensuing analysis is simplified by expressing the logarithmic strain as a series and eliminating all but the first term. This reverts the analysis to an engineering strain type. Hence the work described in this connection validates these previously adopted simplifications. In view of the satisfactory correlations achieved by introducing the above theoretical refinements for the external inversion process, the same procedure has also been applied to the case of internal or outside-to-inside tube inversion. Published analysis of the internal inversion process has previously neglected the pronounced thickening effect clearly demonstrated in all experimental results. (Tube-wall thickness change is not at all evident during external inversion and in fact this also assists in simplifying that analysis). In the present approach the effects of friction and work hardening in a compressive die process of internal inversion have been included in the manner already deduced in other research but in addition a further sub-structural process explaining and quantifying the associated thickening of the tube wall has been formulated. Here it should be mentioned that some uncertainty exists in relation to the application of strain hardening based on average plastic strains. However, since the four published experimental results available have been made with materials exhibiting strain hardening characteristics, the total newly developed and previously evolved analyses have been combined to enable some correlation to be made. The predicted internal inversion loads for two separate sets of results in three different materials are in very reasonable agreement with experimental values.
On angled crack initiation under biaxial loading
Authors: Woo C W , Ling L H 
Published: July 2007

The angled crack problem has been of growing interest to both designers and researchers for the prediction of the structural integrity of components under complex loading conditions. In the study of angled crack growth behaviour, it is invariably of interest to predict the initial crack growth direction θ0 and the fractures stress σc at which crack initiation occurs. In this paper the merits of the various proposed fracture criteria are reviewed. The biaxial loading effect on the parameter used in each criterion for the prediction of the fracture behaviour is studied. It is observed that the popular testing method employing uniaxial loading of a test specimen is inadequate to demonstrate the suitability of fracture criteria in the prediction of θ0 and σc. It is suggested that with the biaxial loading of a test specimen with an angled crack, a better appraisal of the fracture criteria can be obtained. The experimental results obtained in this study seem to support the maximum stress criteria for both uniaxial and biaxial loading conditions. Both tensions and compression biaxial loading effects have been considered.
Stress analysis of some unsymmetric screwed connections
Authors: Fessler H , Jiong-Hua Wang 
Published: July 2007

Unsymmetric shapes and loadings were studied using four frozen-stress photoelastic models. Pure tension was applied to all bolt heads. All the bolt shanks were necked. Three of the blocks were rectangular in cross-section, one was circular with a flat. Two tests represented clamping only; two tests modelled clamping and an offset separating force on a bolted joint causing bending. Results from two previously published tests with axisymmetric blocks are included as a basis for comparisons. The maximum stresses in screw and block always occur near the start of contact. Their values depend on thread configuration at the start of contact, not on the block cross-section. Using pitch-average curves as datum allowed analysis of the maximum variations from these curves. In the tests carried out, RMS values of these variations are doubled by making the block unsymmetric and quadrupled by introducing bending.
Theoretical analysis of a segmented locking ring for shell-bottom connection in pressure vessels
Authors: Strozzi A 
Published: July 2007

The internal forces and deflections of a segmented locking ring inserted in an annular slot in a cylindrical vessel, and supporting its bottom while the vessel is subjected to high internal pressure, are studied. The behaviour of the ring sectors is described in terms of a curved beam of rectangular cross section resting on elastic foundations. A closed form solution is obtained. The results presented show that the reaction force between the ring sectors and the cylindrical vessel exhibits peaks at the sector ends, and that the maximum value of the bending moment for the ring sectors is moticeably higher than that for a complete ring.
Tensile testing of a wire rope strand
Authors: Utting W S , Jones Norman 
Published: July 2007

Experimental tests are reported on wire rope strands subjected to static axial loads. The wire rope strands are held with a polyester resin and silica filler in conical end grips which are capable of full end fixity, partial restraint, or zero torsional resistance (free ends). Strain gauge load cells monitor the tensile load and the associated twisting moment developed in a strand which is restrained at both ends. A new instrument (‘extrometer’) was designed to record simultaneously the extension and rotation over a predetermined gauge length. Strain gauges are used to measure the surface strains on the wires in the outer layer of the strand. Preliminary tests on seven-wire strands demonstrate that the extrometer instrument provides reliable results. The extension and rotation characteristics recorded on a seven-wire strand under tensile load agree reasonably well with the corresponding theoretical predictions, but the wire surface strains reveal an unequal load sharing between nominally identical helical wires. The experimental data presented here is more complete than previously published work on the tensile behaviour of strands and should assist in the development of theoretical methods and numerical schemes suitable for design purposes.
On the determination of boundary stresses in finite elements
Authors: Smart J 
Published: July 2007

A new method for determining the stresses in a finite element analysis on the surface of a body is proposed. The body is meshed using standard quadratic isoparametric elements and the nodal displacements determined in the normal way. The stresses are then determined within any surface element by letting the quadratic become a cubic element, applying the corner nodal displacements and known boundary stresses as penalty functions, and then performing a finite element analysis on the single element. The solution then yields a further set of displacements from which the stresses can be determined. The method is applied to various two-dimensional bodies and the improvements in the predicted boundary stresses shown.
Fabrication of small scale stiffened cylindrical shells
Authors: Scott N D , Harding J E , Dowling P J 
Published: July 2007

This paper describes a recently developed technique used for the fabrication of small scale welded steel models. The extensive use of jigging has allowed stiffened cylindrical models to be manufactured with plate thickness as low as 0.6 mm while maintaining fabrication geometrical tolerances to scaled equivalents of those found in full scale fabrication and within the ranges dictated by relevant design guidance documents. These models have been successfully loaded to destruction, with their performance correlated against that of larger scale models and the results of advanced non-linear numerical techniques.
Experimental studies to determine strain concentration factors for space tubular joints
Authors: Sundaravadivelu R , Nandakumar C G , Srivastava S K , Ganapathy C 
Published: July 2007

This paper presents studies carried out on grouted and ungrouted space tubular joints, with K in one plane and T in the orthogonal plane. Three models have been tested for different load cases adopting T, K, and both T and K (STK) configurations. The tubular joints used in offshore structures, especially in jacket platforms, are multiplanar and some are grouted and hence their study is essential. The stress concentration factor, SCF, as determined using the semi-empirical formulae which are applicable for planar joints are not appropriate for space, grouted joints. The results of the present study indicates that the SCF as determined by formulae for simple joints is unsafe in the plane of K and conservative in the plane of T for the space joint. The effect of the grout is to reduce the stress concentration.
An examination of the neutral loading condition in plasticity theory
Authors: Rees D W A 
Published: July 2007

An examination is made of a number of neutral loading experiments according to classical plasticity theory. For work hardening materials the question as to whether plastic deformation occurs during neutral loading depends strongly upon the deformation produced from initial loading. Initial elastic loading with a subsequent stress path that follows the boundary of the initial vield surface is truly neutral with a wholly elastic response. However, when plastic strain is produced from initial loading then plastic flow is produced from a subsequent stress path that follows the boundary of a surface that is an isotropic expansion of the initial yield surface. Since this violates the assumption of isotropic hardening the usefulness and limitations of the rule of kinematic hardening are examined. It is further shown that the results from recent experiments are particularly relevant to the appraisal of modern developments to plasticity theory. Neutral loading without work hardening will produce plastic flow. It is shown that the corresponding Prandtl—Reuss theoretical solutions are representative of observed behaviour for both severely pre-strained materials and for others that do not harden appreciably. The concept is introduced of lower and upper bounds on the deformation that can be expected from neutral loading. These correspond to the extreme purely elastic and non-work-hardening solutions, respectively.
A compact mixed-mode (cmm) fracture specimen
Authors: Hyde T H , Chambers A C 
Published: July 2007

A practical, compact mixed-mode (CMM) fracture specimen, which can be used for any combination of mode-I and mode-II stress intensities, is described. The loading system, which is suitable for high temperature testing, is also described. The specimen can be used for mixed-mode testing under static, fatigue, creep, or creep/fatigue conditions. The stress-intensity factors ( KI and KII) for the complete range of loading conditions have been obtained by finite element and photoelastic methods. Nodal displacement, stress, and contour integral methods, using the finite element results all gave practically the same stress intensity factors. These were in reasonably close agreement with the results obtained using shear stress distributions obtained from the photoelastic tests.
Torsion tests on large spiral strands
Authors: Raoof M , Hobbs R E 
Published: July 2007

Carefully conducted experimental studies of the torsional characteristics of substantial structural strands are reported. The match between experimental results for an old and fully bedded-in 39 mm diameter, 91 wire spiral strand and some theoretical predictions is very encouraging. The theory, which has been reported elsewhere, treats the individual layers of wires in a strand as orthotropic sheets and, via established results in contact stress theory, takes full account of the frictional interactions between wires. Static and dynamic torsional stiffness and hysteresis data are presented for axially-preloaded strands. Strain gauging of individual wires showed significant scatter, but the match between theory and the mean of the experimental data for a position remote from the termination was good, using the same assumed value of the friction coefficient for all tests. For an old strand, random loading can significantly increase the level of torsional hysteresis above that found for regular cyclic loading, provided that the interwire force changes are large enough to overcome the contact friction. Tests on a new 41 mm diameter strand indicated that hysteresis measurements on newly-manufactured strands could be misleading for long term applications.
A fully automated method for the alignment of x-ray stress-goniometers
Authors: Serruys W , Van Houtte P , Aernoudt E 
Published: July 2007

A method is proposed to align any goniometer for which the specimen and the detector can move independently. Originally the method was developed for a stress-goniometer, but it can also be used for other goniometers. The method consists of an algorithm that calculates the misalignment from the peak positions of the diffraction X-ray beam measured on a metal powder specimen, rotated in several positions (2θ—ψ curves). The algorithm then indicates quantitatively how much the different parts of the apparatus must be adjusted. Only numerical calculations are used and there is no need for special instruments. The algorithm can be easily written into a computer program and makes the alignment a fast and extremely accurate operation.
Imaging of photo-occlusion colour films for quantitative strain and stress analysis
Authors: Economikos L 
Published: July 2007

Digital image analysis and processing techniques have been applied to colour films obtained by a photo-occlusion method to quantitatively describe strain and stress distributions. The objective here is to outline the different colour areas (training areas) on each image accurately and consistently in order for a quantitative comparison of the induced stress on each film to be made based on the size of each colour area. To ensure that the outlined colour areas are uniform in terms of grey levels (isochromatic areas), a statistical analysis was pursued. To ensure consistency of the outline process on each image, an autocorrelation distance was used. The technique described allows direct quantitative judgement of strain fields obtained ‘before’ and ‘after’ treatment. The technique can be applied in any research area where a sequence of isochromatic areas can be recorded on a photographic film.
Photoelastic determination of mixed-mode stress intensity factors for inclined semi-circular cracks in thin tubes
Authors: Hyde T H , Warrior N A 
Published: July 2007

Metal shims have been used to produce internal and external, semicircular, surface, crack-like flaws in cast, photoelastic models of thin tubes. The effects of crack depth, crack orientation, crack inclination, and crack position (i.e., internal or external) have been determined from the analysis of results from 69 slices taken from 24 ‘crack’ types. It has been shown that by taking eleven terms in the solutions for the crack-tip stress fields, rather than taking only the singular solution, more accurate stress-intensity factors are obtained.
The failure of fibre composites: An overview
Authors: Beaumont P W R 
Published: July 2007

Static and cyclic loading, impact, and environmental attack all contribute to the accumulation of damage in composite laminates. The damage can take many forms: delamination and splitting during load cycling, matrix cracking during thermal fatigue, and so on. With this diversity of damage mechanisms, it is no wonder that variability in static strength is significantly enhanced by service in the field. We recognise, therefore, that damage is progressive and is accompanied by a gradual deterioration in strength and stiffness of the laminate. In other words, static strength and life-time are part of the same design phenomenon. One way forward is to identify the broad rules governing fibre composite behaviour. There are two directions: continuum modelling and microscopic modelling. Continuum modelling is useful, but generally demands a formidable experimental programme to determine important design parameters. On a much smaller scale, microscopic modelling provides insight into the damaging mechanisms, but alone is too imprecise to be of much practical use to the design engineer. In parallel, however, they can give guidance towards the development of constitutive laws, the path of model-informed empiricism, which leads to predictive design. In other words, extension of basic damage models of composite failure to generic design features can lead to a formulation of design procedures for composite hardware; this is a powerful route to take.
Modelling and characterization of textile structural composites: A review
Authors: Byun J-H , Chou T-W 
Published: July 2007

The development of innovative fibre architecture, such as two- and three-dimensional woven fabrics and knitted fabrics, as well as braided structure, provides an attractive form of reinforcement for advanced composites. These new materials require new techniques in analysis and design in order to fully utilize their unique mechanical properties.Several analytical models for predicting the thermoelastic properties of two- and three-dimensional fabric composites are reviewed in this paper. The applicability and limitation of the modelling techniques are examined.Recent advancements in the characterization of mechanical properties of three-dimensional fabric composites are also presented. Overall, three-dimensionally braided, angle interlock and orthogonal interlock fabric composites have demonstrated significant improvement in damage tolerance.
Comparison of simulated radiances, Jacobians and linear error analysis for the Microwave Humidity Sounder and the Advanced Microwave Sounding Unit‐B
Authors: Kleespies Thomas J. , Watts Philip 
Published: July 2007

AbstractThe Microwave Humidity Sounder (MHS) has scan characteristics similar to those of the Advanced Microwave Sounding Unit‐B (AMSU‐B). However, its radiometric characteristics are somewhat different, for two channels in particular. Both of these channels have more attenuation with the MHS than the AMSU‐B. Linear error analysis suggests that the improved noise characteristics of the MHS will let it have slightly lower errors than the AMSU‐B. Copyright © 2006 Royal Meteorological Society
Influence of May Atlantic Ocean initial conditions on the subsequent North Atlantic winter climate
Authors: Iwi A. M. , Sutton R. T. , Norton W. A. 
Published: July 2007

AbstractAnalyses of observational data have suggested a link between late spring/summer conditions in the North Atlantic Ocean and atmospheric conditions over the same region in the subsequent winter. This link, and its potential value for seasonal forecasting, is investigated using a coupled climate model, HadCM3. It is found that there is memory of ocean conditions from May through to the following winter, but that the model's sea‐surface‐temperature (SST) anomalies are too weak in the tropics in winter, partly because they are damped too strongly by comparison with observations and partly because of errors in the model SST anomalies in May, particularly in the east Atlantic where the mixed layer is found to be too deep. It is hypothesized that poor agreement between the winter atmospheric signals in the model and in observations is a consequence of the insufficient tropical SST anomalies. Nevertheless, it is demonstrated that, for suitable initial conditions, seasonal forecasts from 1 May could provide useful information about North Atlantic climate the following winter. Copyright © 2006 Royal Meteorological Society
Cloud‐resolving simulations of intense tropical Hector thunderstorms: Implications for aerosol–cloud interactions
Authors: Connolly P. J. , Choularton T. W. , Gallagher M. W. , Bower K. N. , Flynn M. J. , Whiteway J. A. 
Published: July 2007

AbstractThe Hector thunderstorm is studied with a numerical cloud‐resolving model. Special attention is given to modelling the mixed‐phase and glaciated cloud microphysical processes (along with the implications of aerosols) and their influence on the resulting microphysical and dynamical storm structure. Radiative impacts are also calculated. Simulations are performed for a typical storm case from the EMERALD‐II convective cloud experiment in November and December 2002.It is found that, for intense thunderstorms, aerosol indirect effects are generally modified from recently proposed theoretical considerations. Specifically, the proposed ‘glaciation’ indirect effect, resulting from increasing ice nuclei concentrations, is small for intense convection. More importantly, increasing ice number concentrations results in a ‘collection’ indirect effect (where aggregation and accretion processes lead to precipitation) rather than the ‘glaciation’, Bergeron–Findeisen process. There is a ‘thermodynamic’ indirect effect for Hector, as increasing the cloud droplet number concentration from maritime to continental values resulted in a suppression of the heterogeneous freezing process. However, for extreme continental cases, liquid and raindrop freezing by collection processes acquires higher importance; hence there is an optimal value for strong cumulonimbus development. The ‘glaciation’ indirect effect is found to be similar to increasing the rate of ice production by the Hallett–Mossop process. Another aspect of this study shows that there is a significant impact of microphysics on cloud dynamics, and so studying aerosol–cloud effects must also consider dynamical feedback, a strong component of which arises from the latent heat released during homogeneous freezing.The important indirect effects may be well described by recent theory for smaller, more common stratiform and cumulus clouds; however, in the tropics, the importance of Hector‐type storms cannot be ignored as they, and other similar storms, provide a mechanism for the production of widespread cirrus and the release of a large amount of precipitation. Copyright © 2006 Royal Meteorological Society
Use of potential vorticity for incremental data assimilation
Authors: Wlasak M. , Nichols N. K. , Roulstone I. 
Published: July 2007

AbstractDecomposing the mass and wind fields in a data assimilation scheme into balanced and unbalanced flow is part of the process of defining a covariance model. It is not uncommon to assume that the dynamic balanced part of the flow is approximated solely by the rotational part of the wind, which is obtained from a Helmholtz decomposition of the horizontal momentum (with an associated balanced pressure being diagnostically inferred from a balance equation, for example). The unbalanced flow is then represented by the divergence and the residual unbalanced pressure. The assumption that the rotational part of the momentum is a good approximation to the total balanced flow is only valid in certain regimes. We propose a new approach that incorporates flow regime dependence, where we assume that the balanced part of the flow is approximated instead by a linearized potential vorticity increment. We show the benefit of such a formulation in the context of shallow‐water equations defined on a hemisphere. Copyright © 2006 Royal Meteorological Society