bluuebunny/crossref_metadata_2025 huggingface dataset:
A rigid plastic method for the determination of collapse loads of infilled panels with openings
Authors: May I M , Ma S Y A
Published: July 2007

The work done in a yield zone which is able to both shear and rotate has been obtained for a material with a square yield criterion. Yield zones which either rotate or shear only are shown to be special cases. These yield zones are then used in analyses to obtain upper bounds on the collapse loads for masonary infills with openings in framed structures. Lower bounds on the collapse load are also obtained. In all cases analysed the discrepancies between the upper and lower bounds on the collapse load are small. Using the results obtained from the analyses, proposals are made for a design method for infilled panels with openings.
Variable sensitivity shadow moire method
Authors: Asundi A
Published: July 2007

By simply rotating the reference grating in its own plane, the sensitivity of the shadow moire method can be continuously varied. This approach can additionally assist in distinguishing hills and valleys. Application to foot pressure measurement is demonstrated.
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.
Three-Dimensional axisymmetric elastic stresses in pressure vessels with torispherical drumheads (comparison of elasticity, photoelasticity, and shell theory solutions)
Authors: Kishida M , Ozawa H
Published: July 2007

The three-dimensional axisymmetric boundary value problem of pressure vessels with torispherical drumheads is analysed easily and accurately by the use of the ‘indirect fictitious-boundary integral method’. The analysed configurations are similar to each other but have different thicknesses. The comparison of the resent results with photoelasticity and shell theory solutions makes it clear that the shell theory based on Love's first approximation is very reasonable. Additionally, a vessel with hemispherical drumheads with varying thickness from cylinder to head, which is noteworthy for reducing the maximum stresses in the vessel, is studied.
Stress intensity factors for a cracked half plane
Authors: Uzel A R , Hills D A , Sackfield A
Published: July 2007

Mode I and mode II stress intensity factors are found for a slant straight crack buried in an elastic half-plane. Loading is in the form of point forces applied to the crack faces so that the solutions given can then be used as Green's functions in solving half-plane problems where the surface load is arbitrary. The form of the solutions is appropriate only for cases in which the crack remains open, though with modification interfacial Coulomb friction may be accommodated.
A numerical-experimental analysis of the contact stress problem
Authors: Shukla A , Nigam H
Published: July 2007

A general method is presented to evaluate the contact stresses and the contact area from the full field photoelastic data. The procedure utilizes the least squares technique in conjection with the Newton-Raphson method to solve the stress field equations for a Hertz type contact stress problem with or without friction.
Finite element stress analysis of an equal diameter branch pipe intersection subjected to out-of-plane and twisting moments
Authors: Kirkwood M G , Carmichael G D T , Moffat D G
Published: July 2007

The authors have used the BERSAFE finite element computer program to model an equal diameter branch pipe intersection of mean diameter/thickness ratio 24.5. Previous results for internal pressure and the two in-plane bending moments are augmented by the present results for the two out-of-plane and the two twisting moment load categories. The predicted stresses are compared with results from tests on a 254 mm (10 inch) diameter welded branch junction, and also with the values from the current UK power piping code BS 806.
Enhancing finite element boundary stress predictions for plane and axisymmetric situations
Authors: Richards T H , Daniels M J
Published: July 2007

The formulation and implementation of a procedure for enhancing finite element stress predictions is described. The efficiency of the process is demonstrated by application to test cases.
The behaviour of a horizontal vessel on loose saddles — a buckling assessment of the support region
Authors: Kendrick S , Tooth A S
Published: July 2007

By using two computer-based buckling programs, NASTRAN and BOSOR4, the buckling behaviour of the support region of six horizontal storage vessels is assessed. The vessels are supported on twin saddles shown in Fig. 1(a) and of diameter/thickness ratios from 312 to 1154, and lengih radius ratios from 4 to 6.5. They were chosen to provide a range of typical vessels in present use. The specific gravity of the liquid contents required to cause buckling in the support region was obtained by using the computer programs and also by using an equivalent cylinder length with the existing formulations given in the British Pressure Vessel Code, BS 5500 for axisymmetric loading. Comparison of these approaches is used to validate a procedure for finding an allowable buckling stress, hitherto not available for this component.
Moire interferometry for out-of-plane displacement measurement
Authors: Asundi A , Cheung M T
Published: July 2007

A high sensitivity technique for out-of-plane displacement is demonstrated. A 600 lines mm phase grating is used in conjunction with a specularly reflecting (in some cases mirrored) object, to obtain contours of out-of-plane displacement. Initial patterns due to low quality optics are eliminated by a double exposure technique employing carrier (or mismatch) fringes. Beams with cracks are used to experimentally demonstrate this technique.
Analysis of a split ring inserted into a circular housing
Authors: Dragoni E , Strozzi A
Published: July 2007

The internal forces and contact zones of a split ring inserted into a circular housing are examined analytically, numerically, and experimentally. The mechanical components which can be likened to such a configuration are illustrated. The results obtained show that only one third of the ring periphery is in contact with the housing and that the effects of the shear strain on the contact pressure profile are appreciable.
Viscoelastic response of floating ice plates under distributed or concentrated loads
Authors: Hui D
Published: July 2007

This paper deals with the elastic and viscoelastic deflections and stresses of non-homogeneous rectangular or infinite floating ice plates subjected to central distributed lateral loads, where the loading region is of rectangular shape, or concentrated loads. The analysis takes into account the variation of Young's modulus of ice in the thickness direction. The Rayleigh—Ritz procedure is used to obtain the elastic solution for the deflections and bending moments, while the viscoelastic solution is obtained from the elastic response using the correspondence principle. Closed form Bessel-type elastic and viscoelastic solutions are obtained for infinite floating ice plates. Comparisons are made between the time-dependent response of infinite and finite square floating ice plates.
A quadratic formulation for two-dimensional elastoplastic analysis using the boundary integral equation method
Authors: Lee K H , Fenner R T
Published: July 2007

An isoparametric quadratic formulation of the boundary integral equation (BIE) method for two-dimensional elasto-plastic analysis is presented. The initial strain approach is adopted but, unlike in finite element analysis, it is capable of accurately treating perfectly-plastic and weakly strain-hardening materials. Two methods of evaluating internal stress and strain rates, namely, via the elementwise numerical differentiation of the displacement rates, and the pointwise use of integral identities, are included in the solution algorithm, and their relative efficiency is discussed. The use of correction factors is suggested in some cases to ensure that the von Mises flow rules are implemented in a consistent manner. Results to test problems are given and compared with exact or existing approximate solutions.
Dynamic photoelastic investigation of wave propagation and energy transfer across contacts
Authors: Shukla A , Rossmanith H P
Published: July 2007

This paper deals with the dynamic contact of an explosively excited disc with another disc or a half-plane. Dynamic photoelastic recordings show the development of the time-dependent contact area and the formation of the highly complex diffraction pattern.
Measurement of residual deformations in butt-welded plates by use of the white light speckle technique
Authors: Jonsson M , Benckert L
Published: July 2007

A method to measure residual deformations in welded plates is presented. An optical technique, called white light speckle, is used to record the released residual deformations. The method is destructive. Two experiments have been performed. The results are compared with corresponding calculated values. A short description of the calculations is given.
Stress concentration factors due to axial loading of axisymmetric external projections on hollow tubes
Authors: Evans R A , Hardy S J , Hyde T H
Published: July 2007

The finite element method has here been used to determine stress concentration factors due to axial loading applied to axisymmetric, external projections on hollow tubes. A range of tube and projection dimensions have been covered by the investigation. There is good agreement between the present results and previously published data. The results are presented in a manner which allows stress concentration factors to be quickly determined, for any shape within the range covered by the investigation.
Application of holographic interferometry to cylinder deformation
Authors: Evans W T , Russell R M , White A
Published: July 2007

Detailed surface displacement measurements have been made on the surface of a thermally deformed cylinder using a real-time holographic interferometry technique to measure the cartesian components of surface displacement at any surface point in the field of view. No assumptions were made as to the type and direction of displacements being measured and the resulting equations were analysed using a computer analysis package (I)† developed at the Polytechnic of Wales. For comparative purposes, elastic finite-element programs working on experimental temperature distributions were used in a theoretical model of the experiments.
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.
Alternating plasticity at the surfaces of a bree cylinder subjected to in-phase and out-of-phase loading
Authors: Ng H W , Moreton D N
Published: July 2007

A previous paper by the authors (1) obtained expressions for the ratchetting rates of a Bree cylinder subjected to a cyclic internal pressure load together with a cyclic through-wall thermal gradient. The two cases of these loads varying in-phase and out-of-phase were considered. The work reported here considers the same loading situation, but obtains the plastic strain loop width in the alternating plasticity and ratchetting regimes. The result of this analysis is found to be in agreement with numerical studies.
Free and constrained inflation of elastic membranes in relation to thermoforming — axisymmetric problems
Authors: Charrier J-M , Shrivastava S , Wu R
Published: July 2007

Thermoforming of a heated polymeric membrane by pressure inflation against a relatively cold mould surface presents a class of large deformation stress analysis problems in which account must be taken of the progressively changing boundary conditions caused by the sheet coming into contact with the mould surface. As a first step towards solving the general problem, the paper presents a finite element formulation for stress analysis under axisymmetric conditions. Analysis results are presented for free and constrained inflation of a flat circular membrane, the latter with respect to inflation against (a) a circular cylindrical surface, (b) a 60 degree conical surface, and (c) a horizontal plate. As reasonable physical approximations, the material is considered to be purely elastic while the contact conditions are idealized to be either friction-less or non-slipping. Analysis results are compared with those obtained by experiments on rubber membranes.
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.
The numerical solution of some singular contact problems using a Hilbert transform
Authors: Hall R W
Published: July 2007

This paper presents a numerical solution method for frictionless, two dimensional contact problems involving punches with slope discontinuities or sharp corners. The solution method presented employs a finite Hilbert transform to remove computational difficulties associated with the logarithmic pressures encountered within such contacts. A complementary (smooth) problem may then be solved using a rapidly convergent Chebyshev expansion which requires relatively few terms to achieve accurate results. The algebraic (square root) pressure singularities encountered at the ends of certain contacts are also easily resolved, being implicit in the series solution used. The solutions to several problems on the half plane are compared with those obtained directly, and a comparison with analytic solutions is made. In the knowledge that the method gives efficient and accurate half plane solutions, it is then extended to problems involving layers of finite depth. In particular, symmetric wedge indentation on both unbonded and bonded layers is investigated, and results for contact width in relation to applied load are given.
A contribution to wave spring design
Authors: Dragoni E
Published: July 2007

An analytical model for stamped ring wave springs is proposed, based on the theory for circular beams loaded normal to the plane of curvature. The model profits from the adoption of Castigliano's theorem as a tool for mathematical treatment. Closed-form expressions for both load—deflection and load—stress relationships are presented. Because of the particular shape of the spring in the undeformed configuration, the load—deflection curve is found to be appreciably bilinear in character. A similar but less pronounced behaviour is displayed also by the relationship between load and internal stresses. The analytical results are compared to earlier theoretical findings and are shown to correlate well with experimental measurements.
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.
Neutron diffraction measurements of residual stress and plastic deformation in an aluminium alloy weld
Authors: Smith D J , Leggatt R H , Webster G A , Macgillivray H J , Webster P J , Mills G
Published: July 2007

The neutron diffraction technique for measuring residual stresses non-destructively in an aluminium alloy weld has been examined. Calibration experiments have been performed to determine the influence of prior plastic strain and surface effects. Comparisons have also been made with strain gauge methods using the destructive block removal and layering technique for measuring the residual stresses. It has been shown that the neutron diffraction method gives an accurate indication of the three dimensional stress distribution present in a weld and that it can also be employed to estimate the amount of prior plastic strain encountered.
Revised values of finite width correction factors for sen testing of orthotropic materials
Authors: Sweeney J
Published: July 2007

Values for finite-width correction (Y) factors relating to the single-edge-notch (SEN) tension testing of orthotropic materials in opening mode I were presented previously. These have since been found to be in error, in some cases substantially so, and a revised set of factors is presented.
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.
An investigation of the effects of end boundary conditions on cracked plates in tension
Authors: Etemad M R
Published: July 2007

A computational study was made of the effects of end boundary conditions on wide plates in tension. Results showed minimal effects for long gauge lengths, i.e., h > W. These were also compared with theoretical predictions of gross section stress at initiation to tearing, and revealed an effect on J contour values for short gauge lengths of OCT and SENT geometries, as predicted by theory. Other analyses offered are use of estimation procedures, comparison of limit loads, and relationship with η.
A force transducer based on measurement of mean strain in a compact body
Authors: Sundin K G , Jonsson M
Published: July 2007

A force transducer based on measurement of mean strain in a body has been developed. The transducer can be made stiff and compact and is therefore suitable for measurement of impact forces as well as static forces. An experimental test of a simple first prototype was performed using both static and impact loads with different distributions over the load-carrying area of the transducer. The results of the experiments show that the requirement of insensitivity to differences in load distribution is acceptably fulfilled. Improvements are expected to be possible if the transducer is made in a more accurate way.
Stress concentration factors and elastic-plastic stress and strain predictions for axisymmetric internal projections on hollow tubes subjected to axial loading
Authors: Hardy S J , Gowhari-Anaraki A R
Published: July 2007

The finite element method has been used to obtain stress concentration factor data for hollow tubes with axisym-metric internal projections subjected to axial loading. A range of geometries has been considered in the investigation, and the results are complementary to previously published data. Preliminary results from an elastic-plastic analysis of a component with an internal projection are presented. Strain predictions with an elastic-perfectly-plastic material model are found to be between those estimated using linear and Neuber rules for low cycle fatigue life predictions.
Free and constrained inflation of elastic membranes in relation to thermoforming — non-axisymmetric problems
Authors: Charrier J M , Shrivastava S , Wu R
Published: July 2007

This paper deals with the inflation of elastic membranes of general shapes in the context of thermoforming of heated polymeric sheets against relatively cold moulding surfaces. A previous paper (1) has dealt with axisymmetric problems. As before, both theoretical and experimental investigations are reported. The theoretical part consists of a self-contained finite element formulation for large deformation, free and constrained inflation of isotropic elastic membranes. The computer program developed on the basis of presented formulation is applied to free and constrained inflation of plane elliptical membranes of aspect ratios 2 and 4. The material model adopted is that of a single constant neo-Hookean elastic material. The constrained analyses are carried out for inflation against: (a) cylindrical walls (90 degree elliptical cones), (b) 60 degree elliptical cones, and (c) horizontal plates. Separate analyses are performed by assuming the contact to be either slipless or frictionless. The theoretical results are compared with the experimental ones for free inflation and constrained inflation cases (a) and (c).
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.
Holographic measurement of the elastic–plastic boundary surrounding cold-expanded holes
Authors: Sanford R J , Link R E
Published: July 2007

Experimental measurements of the elastic—plastic boundary surrounding split-sleeve cold-expanded holes in 7075-T651 aluminum were made using the technique of holographic interferometry. The levels of expansion investigated ranged from 1.5 per cent to 8.4 per cent. The experimentally determined elastic—plastic boundaries were compared with several theoretical predictions. The experimental results were also compared with the experimental results from another investigation of a similar process. Predictions of the elastic—plastic boundary based on the Hoffman—Sachs theory agreed with the experimental results for levels of cold expansion over the range 1.5—3 per cent expansion. The experimental results of this investigation predicted larger elastic—plastic boundaries than those measured in a separate investigation. Possible explanations for the differences are discussed.
The effect of resin properties on the strength of filamentary structures
Authors: Lu T J , Ji X , Gu X R
Published: July 2007

The adoption of advanced composite materials has significantly improved the performance of solid motor cases, but the failure mechanisms of this kind of filamentary structure are still far from understood, especially with respect to the influence of resin properties. Experimental investigations are reported in the present paper and the results show that the effect of resin matrix properties on burst strength of fibre-wound pressure vessels can be as large as 20—35 per cent. Hence, how to optimize resin matrix properties is a key area of concern in the rocket motor industry. Using improved netting analysis, delamination observed in the head area of the pressure vessels is concluded to be the critical factor leading to burst-strength degradation. Various pressure vessels failure mechanisms are also discussed.
Laminated pipe bends of mixed wall construction subjected to an in-plane bending moment
Authors: Kitching R , Hose D R
Published: July 2007

Some of the ways in which the analysis of laminated composite pipe bends may differ from that of isotropic pipe bends are highlighted. The possible difference between effective bending and tensile moduli is recognised and its influence investigated over a range of bend geometries. A simple method for estimation of the influence of transverse shear terms on the performance of such a pipe bend under in-plane bending is presented, together with numerical results from the analysis. The range of geometries over which these terms may be important is discussed. The analysis is presented in a form which is readily implemented on a microcomputer, and suitable expressions for evaluation of appropriate Fourier series integrals are developed.
A photoelastic investigation of the elastic–plastic strain distribution around slits in various thin plate metal materials
Authors: Yunlin Lai
Published: July 2007

An investigation of the elastic–plastic strain distribution around slits has been made using the photoelastic coating technique. Four different specimens were fabricated from thin metal plates. The specimens differ in slit type and length. The experimental results reveal a general picture of strain distribution around slits under various circumstances and show the influence of slit type, slit length, load level, loading history, etc., on strain distribution. The results agree with Inglis' theoretical elastic solution at low load levels and with Hutchinson's theoretical plastic solution at high load levels. Non-symmetrical isochromatic fringe patterns were obtained in annealed B3 thin steel plate specimens.
A comparative study of two experimental techniques for the measurement of residual stresses in circular rods and tubes of perspex
Authors: Mittal R K , Khan I A
Published: July 2007

Two experimental techniques have been used to measure residual stresses in circular rods and tubes of perspex, i.e., polymethyl methacrylate (PMMA). The first technique, based on photoelasticity, is non-destructive and easy to apply. It gives distribution of stresses over the entire cross-section. The analysis of this technique has been improved to relax some restrictions. The other technique is the layer removal technique. A serious drawback of this technique is that it fails to give the distribution of stresses over the entire cross-section and its accuracy for thin walled tubes is doubtful. A simplification of this technique is possible if the kinematic assumption introduced by Nishimura is replaced by one using the sum rule of stresses.
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.
The role of moisture diffusion and matrix plasticisation on the environmental stress corrosion of grp
Authors: Jones F R
Published: July 2007

An environmental stress corrosion limit can be postulated from the results of a fracture mechanics study of an E-glass fibre composite fabricated from an isophthalic polyester resin. Both the rates of nucleation and crack growth indicated a diffusion controlled fracture mechanics mechanism. The fracture processes in the resin have been quantified using compact tension specimens. The effect of moisture on the values of K1ci and K1ca for crack initiation and arrest for the completely dried resin has demonstrated how the crack blunting processes occur. The moisture diffusion into the resin is characterised by a two-phase microstructure, which has been confirmed by scanning acoustic microscopy. A mechanism which involves a non-uniform stress distribution between the phases, has been developed. The proposed hypothesis may also explain the mechanism of microcavitation required for the transport of acidic environments through stressed resins as reported by Caddock et al. (7).
Edge effects and delamination failures
Authors: Herakovich C T
Published: July 2007

The fundamental relationship between the morphology of a composite laminate and the resulting free edge effects is explored and related to delamination failures. Cross-ply, angle-ply, and quasi-isotropic laminates are discussed in detail. It is shown that the local mismatch in elastic properties of adjacent layers and the global stacking sequence of a laminate both have a significant influence on the interlaminar stresses and delamination failures.
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.
Influence of lubrication type and process conditions on milling performance
Authors: Wu Cheng-Hsien , Chien Chih-Hsien
Published: July 2007

Industry and research institutions are seeking ways to reduce the use of lubricants for ecological and economical reasons. The most reasonable step should be to reduce the consumption of the cutting fluids. This report presents an investigation into various methods of applying cutting fluids with the objective of deriving optimum lubrication conditions for the milling of steel. To improve the minimum-quantity lubrication technique, the distance between the nozzle and the tool tip was also changed to study the effect on the cutting performance. A series of tests was also implemented under various cutting conditions. Three workpiece materials - P20, S45C, and NAK80 - were machined to evaluate the cutting performance. The machining performance was based on the tool flank wear, cutting force, temperature increase, and surface roughness of the workpiece. Experimental results show that the machining performance is affected by the lubrication type, the distance between nozzle and tool tip, and the workpiece material. Minimum-quantity lubrication with appropriate oil quantity and appropriate distance between the nozzle and tool tip provides the optimum process condition. The machinability of the workpiece also affects the machining behaviour.
Continuous dynamic recrystallization phenomena modelling in friction stir welding of aluminium alloys: A neural-network-based approach
Authors: Fratini L , Buffa G
Published: July 2007

The current paper focuses on the continuous dynamic recrystallization phenomena (CDRX) occurring in friction stir welding processes of AA6082 T6 aluminium alloys. In particular, in order to predict the average grain size, a properly trained neural network is linked to the finite element method (FEM) model of the process. The utilized net, which takes as inputs the local values of strain, strain rate, and temperature, was trained starting from experimental data and numerical results. The obtained results show the capability of the artificial intelligence (AI) technique in conjunction with the FE tool to predict the final microstructure in the joint section.
A quick, three-dimensional tetra mesh-based simulation of the filling stage in injection moulding
Authors: Cho W Y , Nam J K , Yun S M , Sin Hyo-Chol
Published: July 2007

A solver based on the Hele-Shaw model can perform calculations faster than a full three-dimensional (3D) solver, but it has a drawback: it requires a mid-plane mesh whose transformation is considerably time consuming. To overcome this drawback, a new solver based on the Hele-Shaw model was developed. The new solver can directly read a 3D tetra mesh made from computer-aided design (CAD) models and perform the filling analysis of injection moulding quickly with reliable accuracy. In the current study, some classification and assignment operations are performed to apply the 3D mesh to the new solver based on mid-plane mesh. In addition, a node-pairing method is proposed for fast filling analysis. For verification of this method, results of this study were compared with those of MPI, which is one of the products of Moldflow. The results from the developed solver for most cases were very similar to those of MPI, and the analysis took only 30–40 per cent of the time consumed by MPI.
New friction welding process for pipeline girth welds - parameter optimization
Authors: Faes K , Dhooge A , Jaspart O , D'Alvise L , Afschrift P , De Baets P
Published: July 2007

A promising new welding method for fully automatic welding of pipelines has been developed. The proposed welding procedure, called friction with an ‘explosive’ forge force (FRIEX), is a new variant of the well-known friction welding process. In the first part of the present paper, the working principles of the FRIEX welding process are described. Subsequently, a brief overview is given of small-scale experiments that have been conducted in order to demonstrate the practical feasibility of this welding process. The optimization of the shape of the welding ring is discussed. Finite element models have been developed which are able to predict the process behaviour under varying process parameters. Results of numerical simulations showed good agreement with experimental observations.
Characterization of machining of AISI 1045 steel over a wide range of cutting speeds. Part 1: Investigation of contact phenomena
Authors: Iqbal S A , Mativenga P T , Sheikh M A
Published: July 2007

Friction conditions at the tool-chip interface are one of the most important inputs for modelling and simulation of the machining process. However, the nature of the tool-chip contact is often assumed in developing finite element models, thereby seriously affecting their reliability. In this paper, results of an investigation into the tool-chip contact interface using uncoated tungsten-based cemented carbide tools in dry high-speed turning of AISI 1045 steel are presented. The tests were conducted at cutting speeds ranging between 198 and 879m/min with a feed rate of 0.1mm/rev and a constant depth of cut of 2.5 mm. The effects of cutting speed on tool rake face contact length, contact area, friction, element mapping, and surface roughness are studied and discussed. It is shown that the quantitative methods, used here to characterize the tool-chip contact region, can provide valuable data for accurate and reliable modelling of the metal machining process over a wide range of cutting speeds.
Characterization of machining of AISI 1045 steel over a wide range of cutting speeds. Part 2: Evaluation of flow stress models and interface friction distribution schemes
Authors: Iqbal S A , Mativenga P T , Sheikh M A
Published: July 2007

To ensure that the simulation of the orthogonal metal-cutting process yields accurate results, the material and frictional behaviours during simulation have to be defined accurately. Flow stress models are used extensively in the simulations of deformation processes occurring at high strains, strain rates, and temperatures. In this work, the Johnson-Cook, Maekawa et al., Oxley, El-Magd et al., and Zerilli-Armstrong flow stress models are evaluated. AISI 1045 steel is used as the workpiece material because it is well characterized. First, the predictive capability of these flow stress models is compared with the published experimental data at high strain rates and the modelling errors are quantified. Different friction conditions along the tool rake face are also discussed. Then the friction conditions based on results of scanning electron microscopy-energy-dispersive X-ray analysis from Part 1 are implemented together with other friction models. The material flow stress models and friction conditions are assessed using an updated Lagrangian finite element code simulating continuous chip formation over a range of cutting speeds. The assessment of these models is carried out for their accuracy in predicting the cutting force and shear angle with those obtained experimentally in order to draw conclusions regarding their comparative performance.
Development of a high-performance force display for material science
Authors: Hashimoto M
Published: July 2007

It is important to know the inter-atomic bonding state in material for a new material design and analysis. Although the bonding states can be simulated based on the inter-atomic potential, it is difficult to understand them immediately in three-dimensional space. To understand the inter-atomic bonding state intuitively, it is effective to use force display systems. A high-performance force display system for material science is then developed. The force display consists of a parallel mechanism with direct-drive linear servo actuators. The mechanism is called a fixed linear type parallel mechanism. Since the actuators are fixed on the base, high-speed motion of the manipulator is possible, and the mechanism has a high load capacity and back drivability. These characteristics lead to a high-performance force feedback control. In the current paper, the design and prototyping are described. In addition, it is applied for the force display experiment of inter-atomic bonding state, and the effectiveness is demonstrated.
A driver-distraction-based lane-keeping assistance system
Authors: Pohl J , Birk W , Westervall L
Published: July 2007

Single-vehicle roadway departure (SVRD) accidents occur in many cases owing to driver distraction or drowsiness constituting a substantial share of today's road vehicle accidents and casualties. This paper describes a distraction-based lane-keeping support system, which intervenes only when the driver is positively detected as being distracted. Distraction here is understood as cognitive and visual distraction, and the focus of this system is on the latter one. In order to estimate the driver's visual distraction level, a video-based driver monitoring system is used. Lane-keeping support is provided by an additional torque applied on the steering shaft in order to regain an appropriate lane position. In this manner the system only intervenes when the vehicle has drifted out of its lane and while the driver is distracted. Test track investigations indicate large opportunities for such a system from a driver perspective, provided that sufficient reliability of the employed vision sensor for lane and face tracking can be obtained.
Proportional-derivative energy-based control for manipulator using normalized quasi-velocities
Authors: Herman P
Published: July 2007

This paper presents a proportional-derivative (PD) controller for rigid manipulators whose dynamics is expressed in terms of the normalized quasi-velocities (NQV) described by Jain and Rodriguez. It is shown that using the NQV it is possible to shape the kinetic energy reduction of the manipulator and at the same time to realize the PD control in its joint space. The energy-based strategy gives an insight into the position control and allows a different method to be used instead of the classical PD controller in order to change the behaviour of the system. The controller uses quasi-velocities arising from a decomposition of the manipulator mass matrix. Its use yields a globally asymptotically stable closed-loop system. The performance of the controller is illustrated via experiment on a two-degree-of-freedom robot arm and in simulation on a three-degree-of-freedom spatial manipulator.