Showing papers in "Journal of Strain Analysis for Engineering Design in 1989"
TL;DR: In this paper, the authors calculate des taux de restitution de l'energie des modes I and II dans le cadre d'une analyse d'un poutre elastique conventionnnelle including les effets des grands deplacements.
Abstract: Calcul des taux de restitution de l'energie des modes I et II dans le cadre d'une analyse d'une poutre elastique conventionnnelle incluant les effets des grands deplacements
187 citations
TL;DR: In this paper, the fatigue behavior of high performance continuous fibre reinforced composite materials based on organic matrices has been reviewed and methods of performing fatigue tests are discussed. But the effects of stress concentrators and environmental exposure are considered and the use of alternative forms of composite such as woven materials discussed.
Abstract: The fatigue behaviour of high performance continuous fibre reinforced composite materials based on organic matrices has been reviewed. Methods of performing fatigue tests are discussed. Fatigue damage development processes are reviewed for typical unidirectional and laminated materials and fatigue performance compared for different materials. The effects of stress concentrators and environmental exposure are considered and the use of alternative forms of composite such as woven materials discussed. A comparison with the fatigue of metals is made.
118 citations
TL;DR: In this paper, a review of the mechanisms of damage and its development in composite materials subjected to mechanical loads is presented, and two basically different but complementary approaches, namely, micromechanics modelling and continuum damage modelling, are described.
Abstract: This paper presents first a review of the mechanisms of damage and its development in composite materials subjected to mechanical loads. The materials considered are thermosetting polymers reinforced with short or long fibres of glass or carbon. Laminates with woven fabric are also considered. A discussion regarding how the essential features of the damage mechanisms may be incorporated in a modelling approach is then given. Two basically different but complementary approaches, namely, micromechanics modelling and continuum damage modelling, are described. The present author's own approach using the internal variables concept is discussed at some length, and the predictions of elastic property degradation given by it are illustrated by experimental data.This paper is an updated and expanded version of a previous paper written by the author (32).
83 citations
TL;DR: Several analytical models for predicting the thermoelastic properties of two-and three-dimensional fabric composites are reviewed in this paper, and the applicability and limitation of the modelling techniques are examined.
Abstract: 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.
68 citations
TL;DR: In this article, the authors identify the broad rules governing fiber composite behaviour and propose a method to determine important design parameters such as static strength and life-time of composite laminate.
Abstract: 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,...
52 citations
TL;DR: In this article, a fracture mechanics approach is used to measure the residual stresses in a welded plate and determine the state of the stresses that existed in the uncracked plate.
Abstract: A simple method for measuring residual stresses in a plate is described. In this method residual stresses are evaluated using a fracture mechanics approach, that is, the strains or displacements measured at a point on the edge of a plate as a crack is introduced and extended from the edge are used to deduce the state of stresses that existed in the uncracked plate. Through finite element analyses and experiments this method is shown to be valid and effective for measuring the two-dimensional residual stress distribution of a welded plate.
35 citations
Abstract: 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.
29 citations
TL;DR: In this article, a method for determining stress intensity factors for plane cracks intersecting a free edge and where the bulk stress field is such that the crack faces are pressed together along at least part of their length is described.
Abstract: A powerful method is described for determining stress intensity factors for plane cracks intersecting a free edge and where the bulk stress field is such that the crack faces are pressed together along at least part of their length. This configuration occurs widely in problems where the crack is propelled by a contact stress field, but the simpler example given here for illustration purposes involves a cracked column undergoing compression and shear.
24 citations
TL;DR: In this article, it was shown that the normal stress in the adhesive by Goland and Reissner are correct and that the finite element results converged to those of GOLDE and this article.
Abstract: Goland and Reissner (1)t presented in 1944 the classic paper ‘The Stresses in Cemented Joints’. Other authors have extended their formulation to different configurations and/or constitutive relationships for the adherends (see (2) for a summary of adhesive research in this area) or have attempted to make less restrictive assumptions about the adhesive, as in (3). Nevertheless, the results of Goland and Reissner, especially for the case of flexible adhesive, remain the benchmark against which other theories are compared. References (4x6) reported that the expressions given by Goland and Reissner for the normal stress in the adhesive are in error and gave corrections to those formulae. This short note will show that the equations for normal stress in the adhesive by Goland and Reissner are correct. It is presented in the hopes that it will keep others from being misled by references (4H6), as was almost the case with this author. A short derivation of the equations in question are presented. Carpenter (7) has presented a special finite element which exactly models Goland and Reissner’s assumption of adhesive behavior. An example is presented which shows that the finite element results converge to those of Goland and Reissner’s original equations and not those of (4)-(6), thus verifying the correctness of Goland and Reissner’s formulation.
14 citations
TL;DR: In this article, 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.
Abstract: 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.
13 citations
TL;DR: In this paper, an environmental stress corrosion limit was derived from the results of a fracture mechanics study of an E-glass fiber composite fabricated from an isophthalic polyester resin.
Abstract: 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 t...
TL;DR: In this paper, the authors studied the periphery deflection in an annular plate clamped along its inner edge and loaded at its outer boundary by a transverse concentrated force via a series solution.
Abstract: The periphery deflection in an annular plate clamped along its inner edge and loaded at its outer boundary by a transverse concentrated force are studied via a series solution. The corrected expressions for the series coefficients are presented. The series convergence is accelerated via a simple technique. Approximate methods are proposed to account for the compliant clamp and shear strain effects on the plate deflections, and they are validated against simplified theoretical models.
TL;DR: In this paper, 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, and the results are complementary to previously published data.
Abstract: 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.
TL;DR: In this paper, the authors extended fracture mechanics concepts for describing creep crack growth in terms of ductility exhaustion in a process zone at the crack tip to include damage accumulation in the ligament ahead of a crack.
Abstract: Fracture mechanics concepts for describing creep crack growth in terms of ductility exhaustion in a process zone at the crack tip are reviewed and extended to include damage accumulation in the ligament ahead of a crack. Applications are considered which show that net section damage has most influence for short cracks and plane stress conditions where significant damage can develop in the uncracked ligament. It is shown that, under plane strain loading, insufficient ligament damage occurs during the crack growth phase for it to have an appreciable effect on failure times. A method is also presented for accounting for the influence of an incubation period prior to the onset of cracking and for making residual life estimates.
TL;DR: In this article, photoelastic tests of cross-sections of two keyed shafts with 13 different shapes of keys showed that rounded edges of keys give lower stress concentrations in the shaft than chamfered edges.
Abstract: Two-dimensional, photoelastic tests of cross-sections of two keyed shafts with 13 different shapes of keys showed that rounded edges of keys give lower stress concentrations in the shaft than chamfered edges. Stress concentrations are reduced by making both rounding radii and chamfers larger than the key way fillet radius.Making the key a sliding fit in the keyway allows significant relative movement and produces lower stress concentrations than the usual interference fits.Boussinesq's theoretical solution for stresses near a concentrated edge load has been successfully used for direct calibration of small photoelastic models.
TL;DR: In this article, 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.
Abstract: 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.
TL;DR: In this article, a simple method for estimation of the influence of transverse shear terms on the performance of a pipe bend under in-plane bending is presented, together with numerical results from the analysis.
Abstract: 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.
TL;DR: In this article, the photoelastic coating technique was used to study plastic strains at the orthogonal intersections of plates, formed by welding two side plates, without weld preparation, to a main plate.
Abstract: The photoelastic coating technique was used to study plastic strains at the orthogonal intersections of plates, formed by welding two side plates, without weld preparation, to a main plate. Models were cut from this weldment, perpendicularly to the planes of the plates. These models were loaded by tension and pure bending applied to the side plates. Although yielding starts at the weld toes, it remains constrained there due to the greater strength of the heat-affected zone. Plastic collapse occurs in the ‘parent’ plate. This phenomenon is due to the heat affected zone, not due to the notch formed by the weld.
TL;DR: In this paper, the 1 per cent strain accumulation boundary in stainless steel type 316 strip subjected to constant axial tension and a cyclic change of curvature was determined for temperatures between 300 and 500°C.
Abstract: This paper details tests undertaken to determine the 1 per cent strain accumulation boundary in stainless steel type 316 strip subjected to constant axial tension and a cyclic change of curvature. Boundaries are obtained for temperatures between 300 and 500°C. These are compared with two design rules, both of which are shown to be conservative. Additionally, the temperature at which the transition from the characteristic room temperature behaviour of continued ratchetting to the ‘shakedown’ observed at elevated temperatures is investigated. Results obtained indicate that this transition temperature is influenced by the magnitude of the applied stresses.
TL;DR: In this article, the effects of end boundary conditions on wide plates in tension were investigated and the results showed minimal effects for long gauge lengths, i.e., h > W. These results 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.
Abstract: 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.
TL;DR: In this paper, the effect of resin matrix properties on burst strength of fiber-wound pressure vessels can be as large as 20-35 percent in the case of solid motor cases.
Abstract: 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.
TL;DR: In this article, an investigation of the elastic-plastic strain distribution around slits has been made using the photoelastic coating technique, and the results agree with Inglis' theoretical elastic solution at low load levels and with Hutchinson's theoretical plastic solution at high load levels.
Abstract: 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.
TL;DR: In this article, experiments have been conducted on steel column base plates subjected to eccentric loads and the strain distributions in the base plates at various stages of loading have been determined, and the thickness of the base plate and the eccentricity of load have been treated as parameters.
Abstract: Experiments have been conducted on steel column base plates subjected to eccentric loads and the strain distributions in the base plates at various stages of loading have been determined. The thickness of the base plate and the eccentricity of load have been treated as parameters. Test results for the maximum bending strains, which always occurred at the column–base plate junction on the side of the load, compare reasonably well with those from a finite element analysis. However, the present results for the bending strains in the cantilever portions of the base plates which failed by yielding are greater than those obtained from classical theory, which is, therefore, seen to be conservative for these cases. Longitudinal and lateral strain distributions, strain contour plans, maximum bending strain variation with load, and interaction diagrams are presented and the results discussed. From these results it is evident that flexible base plates, especially when loaded at higher eccentricities, behave ...
TL;DR: In this article, a force transducer based on measurement of mean strain in a body has been developed, which can be made stiff and compact and is therefore suitable for measurement of impact forces as well as static forces.
Abstract: 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.
TL;DR: In this article, two experimental techniques have been used to measure residual stresses in circular rods and tubes of perspex, i.e., polymethyl methacrylate (PMMA) and layer removal.
Abstract: 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.
TL;DR: 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 and the technique described allows direct quantitative judgement of strain fields obtained ‘before’ and ‘after’ treatment.
Abstract: 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.