bluuebunny/crossref_metadata_2025 huggingface dataset:
Attenuation of brassinosteroid signaling enhancesFLCexpression and delays flowering
Authors: Domagalska Malgorzata A. , Schomburg Fritz M. , Amasino Richard M. , Vierstra Richard D. , Nagy Ferenc , Davis Seth J.
Published: July 2007

A main developmental switch in the life cycle of a flowering plant is the transition from vegetative to reproductive growth. In Arabidopsis thaliana, distinct genetic pathways regulate the timing of this transition. We report here that brassinosteroid (BR) signaling establishes an unexpected and previously unidentified genetic pathway in the floral-regulating network. We isolated two alleles of brassinosteroid-insensitive 1 (bri1) as enhancers of the late-flowering autonomous-pathway mutant luminidependens(ld). bri1 was found to predominantly function as a flowering-time enhancer. Further analyses of double mutants between bri1 and known flowering-time mutants revealed that bri1also enhances the phenotype of the autonomous mutant fca and of the dominant FRI line. Moreover, all of these double mutants exhibited elevated expression of the potent floral repressor FLOWERING LOCUS C(FLC). This molecular response could be efficiently suppressed by vernalization, leading to accelerated flowering. Additionally, specific reduction of the expression of FLC via RNA interference accelerated flowering in bri1 ld double mutants. Importantly, combining the BR-deficient mutant cpd with ld also resulted in delayed flowering and led to elevated FLC expression. Finally, we found increased histone H3 acetylation at FLC chromatin in bri1 ldmutants, as compared with ld single mutants. In conclusion, we propose that BR signaling acts to repress FLC expression,particularly in genetic situations, with, for example, dominant FRIalleles or autonomous-pathway mutants, in which FLC is activated.
Bi-compartmental communication contributes to the opposite proliferative behavior of Notch1-deficient hair follicle and epidermal keratinocytes
Authors: Lee Jonghyeob , Basak Jacob M. , Demehri Shadmehr , Kopan Raphael
Published: July 2007

Notch1-deficient epidermal keratinocytes become progressively hyperplastic and eventually produce tumors. By contrast, Notch1-deficient hair matrix keratinocytes have lower mitotic rates, resulting in smaller follicles with fewer cells. In addition, the ratio of melanocytes to keratinocytes is greatly reduced in hair follicles. Investigation into the underlying mechanism for these phenotypes revealed significant changes in the Kit, Tgfβ and insulin-like growth factor (IGF) signaling pathways, which have not been previously shown to be downstream of Notch signaling. The level of Kitl (Scf) mRNA produced by Notch1-deficient follicular keratinocytes was reduced when compared with wild type, resulting in a decline in melanocyte population. Tgfβ ligands were elevated in Notch1-deficient keratinocytes, which correlated with elevated expression of several targets,including the diffusible IGF antagonist Igfbp3 in the dermal papilla. Diffusible stromal targets remained elevated in the absence of epithelial Tgfβ receptors, consistent with paracrine Tgfβ signaling. Overexpression of Igf1 in the keratinocyte reversed the phenotype, as expected if Notch1 loss altered the IGF/insulin-like growth factor binding protein(IGFBP) balance. Conversely, epidermal keratinocytes contained less stromal Igfbp4 and might thus be primed to experience an increase in IGF signaling as animals age. These results suggest that Notch1 participates in a bi-compartmental signaling network that controls homeostasis, follicular proliferation rates and melanocyte population within the skin.
Two distinct sources for a population of maturing axial progenitors
Authors: Cambray Noemí , Wilson Valerie
Published: July 2007

In mammals, the primitive streak region and its descendant, the tail bud,are the source of nascent mesoderm and spinal cord throughout axial elongation. A localised population of long-term axial progenitors has been identified in a region of the tail bud, the chordoneural hinge, but the localisation of such progenitors at earlier stages is so far untested. By studying gene expression, we have shown that a specific topological arrangement of domains persists from the streak to the tail bud, and includes an area (the node-streak border) in which ectoderm that expresses primitive streak markers overlies the prospective notochord. This arrangement persists in the chordoneural hinge. Homotopic grafts show that, as in other vertebrates, cells in the streak and node predominantly produce mesoderm,whereas those in the node-streak border and lateral to the streak additionally produce neurectoderm. Node-streak border descendants populate not only neurectoderm, somites and notochord throughout the axis, but also the chordoneural hinge. Ectoderm lateral to the embryonic day (E)8.5 streak is later recruited to the midline, where it produces somites and chordoneural hinge cells, the position of which overlaps that of border-derived cells. Therefore, the E8.5 axial progenitors that will make the tail comprise cells from two distinct sources: the border and lateral ectoderm. Furthermore,heterotopic grafts of cells from outside the border to this region also populate the chordoneural hinge. Expression of several streak- and tail bud-specific genes declines well before elongation ends, even though this late population can be successfully transplanted into earlier embryos. Therefore,at least some aspects of progenitor status are conferred by the environment and are not an intrinsic property of the cells.
Effect of preferred orientation on x-ray stress measurement in NS.5 aluminium alloy
Authors: Rutledge A L , Taylor R M
Published: July 2007

This paper describes an investigation into the effect of preferred orientation on X-ray stress measurements in NS.5 aluminium-alloy sheet. When the sin2 ψ technique (1)∗ of X-ray stress measurement is applied to practical engineering problems it is necessary that the correct values of the elastic constants of the material be used to calculate the X-ray stress values. In this investigation, the X-ray values of Young's modulus E and Poisson's ratio v were found to vary significantly with the direction of stress measurement relative to the rolling direction of the sheet.
Transverse-sensitivity errors in biaxial-stress fields
Authors: Saxena V C , Machin K E
Published: July 2007

Expressions for the errors in principal stresses and stress ratio due to transverse sensitivity of the strain gauges have been determined in terms of the stress ratio. The results are also represented in the form of curves.
Large deflection of plates with unsupported edges
Authors: Rushton K R
Published: July 2007

A method of including the unsupported edge condition in the large deflection of rectangular plates is proposed. Solutions are obtained which use a finite-difference technique based on the dynamic-relaxation method. Comparisons are made with certain theoretical small-deflection solutions. Two particular problems are considered in detail, the lateral loading of plates supported at the corners and the post-buckling of a plate with one unsupported edge.
Relationships for tensile creep under transient stresses
Authors: Tilly G P
Published: July 2007

The tensile creep occurring during and immediately after loading has been studied for an 11 per cent chromium steel and a nickel-base alloy at elevated temperatures. It was found that the strains incurred during loading are dependent upon loading rate and can be estimated from consideration of the equations for static creep by using the assumption of strain hardening. The strain incurred during slow loading causes the processes of creep to be at a more advanced stage when the static phase commences so that the resulting strain rates are also dependent upon the rate of loading. Rapid loading tends to produce almost wholly elastic strains so that the subsequent static phase involves a more fundamental shape of creep curve.

The approach was extended to consider minimum creep rate and fracture, and it was shown that they could be related to applied stress by use of the creep equation. The shapes of the stress-strain hysteresis loops were also derived from the creep equation and estimates based on static-creep data were shown to correlate with experimental data from repeated-tension cycling with a triangular wave shape.
Increases in fatigue life caused by the introduction of rest periods
Authors: Miller K J , Hatter D J
Published: July 2007

Fatigue data are usually derived from uninterrupted laboratory tests although the data may be required for conditions in which components are infrequently cycled. This paper discusses tests that involve rest periods to simulate infrequent cycling. The introduction of rest periods always causes an increase in endurance which approaches a maximum of approximately 100 per cent at a critical value of rest. The total rest period appears to be a more important parameter than either the number of rest periods or the position in the lifetime at which rests may be taken.
The reflected-shadow method for the study of the constrained zones in cracked birefringent media
Authors: Theocaris P S
Published: July 2007

An optical method has been developed for the study of the constrained zones embedded at the crack tips in birefringent materials. Deviation of the partially reflected light beam from the back surface of a thin transparent plate made of a birefringent material, which contained a crack, formed a caustic which defined the constrained zone around the crack tip. The shape of the constrained zone, limited by the caustic, depended on the thickness variation of the plate, as well as on the double refraction of the impinging light beam. It is shown that for an elastically strained birefringent material with a birefringent constant ξ the caustic has the shape of a curve depending on ξ, which for ξ ↑ 0 degenerates to a circle. This curve, when projected on a screen, forms a generalized epicycloid created by the tips of the resultant vector, which represents the reflected and optically deviated light rays. The characteristic properties of the epicycloids are discussed and their connection with the stress intensity factor KI, which is related to the opening mode of fracture, is established. Experimental examples with transversely cracked plates made of birefringent materials are given.
Comparison of various formulae and experimental stress-concentration factors for symmetrical u-notched plates
Authors: Baratta F I
Published: July 2007

Formulae of Baratta and Neal, Neuber, and Heywood are compared with available data on experimental stress-concentration factors in the literature for symmetrical U-notched plates.

From comparisons of such formulae, guidance is provided to the researcher and designer with regard to accuracy and tendency to under- or over-estimate.
Experimental and theoretical bending deflections of laminated plates
Authors: Webber J P H
Published: July 2007

Rectangular plates made from laminated orthotropic layers are analysed by the finite-element displacement method for small bending deflections. The results of experiments on plastic plates reinforced with carbon fibres are compared with the finite-element analysis which neglects coupling between bending and stretching. It is shown that the theory is adequate for plates in which the coupling effect is not present, but underestimates the deflections for plates which contain the coupling terms.
Stress and flexibility factors for multi-mitred pipe bends subjected to internal pressure combined with external loadings
Authors: Bond M P , Kitching R
Published: July 2007

The stress analysis of a multi-mitred pipe bend when subjected to an internal pressure and a simultaneous in-plane or out-of-plane bending load has been developed. Stress patterns and flexibility factors calculated by this analysis are compared with experimental results from a large-diameter, thin-walled, three-weld, 90° multi-mitred bend which was subjected to in-plane bending tests at various internal pressures.
A photothermoelastic investigation of transient thermal stresses in wing ribs
Authors: Matsumoto E , Sumi S , Sekiya T
Published: July 2007

The photothermoelastic method of refrigeration has been used to study the problem of a long beam under transient temperature distribution and good correlation with the theoretical values has been obtained. The new technique for three-dimensional photothermoelasticity, which uses a composite model made of photoelastically sensitive and insensitive materials, is suggested for the analysis of idealized wing-rib structures.
Determination of energy release rates and stress-intensity factors by the finite-element method
Authors: Dixon J R , Strannigan J S
Published: July 2007

It is shown that the finite-element method of analysis, used in conjunction with a generalized form of the compliance equations of fracture mechanics, can provide a general means of determining energy release rates and stress-intensity factors for complex crack configuration and loadings. The method is applied to several crack configurations in flat plates and in round bars.
Energy for crack growth in model rubber components
Authors: Lindley P B
Published: July 2007

The determination of tearing energy, i.e. the energy available for crack growth, is an essential prerequisite for the estimation of the fatigue life of rubber components. Three methods of determining tearing energy are considered: from changes in total energy, from crack surface displacements, and by comparison with known values for the same crack growth rates. It is shown by applying experimental and numerical techniques to plane-stress testpieces, not necessarily of uniform stress or thickness, that the methods are satisfactory.
Calculation of contact stresses at contacts between conical bodies
Authors: McCallion H , Hallam C B
Published: July 2007

A method for calculating the elastic-stress distribution in two axi-symmetrical conical bodies caused by frictionless contact between them is described. Finite-difference methods were used to solve the governing differential equations. Equilibrium and compatibility over the contacting surfaces was achieved by using the finite-difference solutions to derive a matrix of influence coefficients. By means of an iterative technique, using this matrix, the portion of each surface in the contact zone and the stresses on it were found. With equilibrium and compatibility achieved, the stresses throughout the body of each component were calculated. A selection of results for one case is given.
A simple continuum model of a layered composite material
Authors: King J L
Published: July 2007

A multi-layered composite material may, for some purposes, be regarded as a continuum. A material consisting of alternate layers of two materials and loaded in one direction only is looked at from this standpoint; one material, of high elastic moduli, is assumed to take the tensile loads and the other, of low moduli, accommodates the shear strains. It is shown that the governing equation can be reduced to the Laplace equation. Two examples, where simple analytical solutions are obtainable, are examined; one is the stress distribution round a crack, the other is the stress distribution in a tensile specimen.
An automatic high-speed scanner for moiré fringe techniques
Authors: Hitchings D J , Luxmoore A R
Published: July 2007

A high-speed scanning system has been developed to locate the centres of moiré fringes along any single line. The system comprises a rotating-mirror scanner for conversion of an optical signal to electrical; this conversion is followed by peak detection, storage, and print-out electronics. Up to 20 fringes can be scanned in 1 ms. The results are printed in terms of fringe separations along the scanning line.
Mixed-displacement finite-element analysis with particular application using plane-stress triangles
Authors: McNeice G M , Hunnisett S F
Published: July 2007

Finite elements which have different displacement functions for each boundary are termed ‘mixed-displacement’ elements. The mixed-displacement approach to finite elements is applied to plane-stress problems in which mixed-strain triangles are formed from the linear-strain triangle. It is shown that by using these triangles in conjunction with existing linear- and constant-strain triangles, higher strain-energy content is produced with fewer active degrees of freedom than are otherwise necessary. A basic triangular grid is first assumed and any number of additional midside nodes can be inserted in regions of high strain gradients. Reference to three-dimensional isoparametric elements is given.
The application of photo-orthotropic elasticity
Authors: Prabhakaran R , Dally J W
Published: July 2007

A brief review of the recent developments in photo-orthotropic elasticity which covers methods of producing transparent, birefringent orthotropic model materials from glass fibres and plastics is presented. A classical form of the stress-optic law applicable in uniaxial-stress fields is given in which the orthotropic characteristics of the model material are treated by considering the material fringe value fu to be dependent upon fibre orientation.

Limitations of the orthotropic model materials are identified and the effects of material non-linearities, fibre debonding and fibre distribution are described. The methods established were used to obtain a solution of the stresses in an orthotropic half-plane loaded with a concentrated force. The experimental results obtained were compared with theoretical results due to Green, and while the agreement was good, errors were considerably larger than those encountered in photo-isotropic elasticity.

Finally the methods were applied to the solution of boundary stress on an elliptical hole in a finite-width tension strip.
Theory of thin elastic shells applied to pipe bends subjected to bending and internal pressure
Authors: Blomfield J A , Turner C E
Published: July 2007

A consistent set of equations for the in-plane and out-of-plane bending of pipe bends is derived from the equations of shell theory with a correction for the coupling effect of internal pressure. The resulting governing equations are solved numerically and compared with other experimental and theoretical solutions.
Computation of post-yield behaviour in notch-bend and tension testpieces
Authors: Turner C E , Cheung J S T
Published: July 2007

First results of an analysis of notch-bend pieces in plane strain by two-dimensional elastic-plastic finite-element computations are given. Comparisons are given of load-displacement records for three notch depths and a general non-dimensional presentation proposed. Relations between the values of surface and cracktip crack opening displacement are shown and comparison is made with a few results in plane stress, by Dugdale model and in tension. The trend of local stress and strain patterns is shown and stress triaxiality is evaluated approximately.

It is concluded that nearly quantitative agreement can be reached for the general behaviour of notched pieces by the use of fairly simple two-dimensional models but many of the results could be improved by the use of better element meshes. For the study of local crack-tip deformations more detailed models or more powerful means of characterizing the crack tip are required.
The recording and interpretation of engineering measurements
Authors: Hickson V M
Published: July 2007

A report on the conference held at the Institute of Marine Engineers in the City of London on 5–7th April 1972.
Diffractographic moiré technique illustrated by determination of beam deflections
Authors: Pryor T R , Hageniers O L , North W P T
Published: July 2007

A new ‘diffractographic’ technique for measuring displacements has been developed which uses changes in the diffraction pattern of a single slit aperture formed between a fixed edge and an edge of the member itself. Described herein is an extension of the method whereby two diffraction patterns representing states of beam deflection produce moiré-type fringes of proportional spacing. Both ‘live-fringe’ and double-exposure diffractograms are shown to form these fringes and the resulting patterns directly depict deflection to within ± 0.0001 in all along the beam, over a displacement range of at least 0.1 in.
The influence of scatter on some simple variable-stress creep predictions
Authors: Lomax A B
Published: July 2007

The difficulties involved in predicting creep characteristics for three simple variable-stress situations are demonstrated. The inclusion of scatter data is shown to be essential for the correlation between theoretical and experimental results in all cases. It is concluded that it is not appropriate to resort to analytical methods that are more complex than those based on the mechanical equation of state.
Mismatches applied to Ligtenberg's reflective moiré method
Authors: Ranganayakamma B , Chiang E P
Published: July 2007

A method is developed whereby the accuracy of Ligtenberg's reflective moiré method for plates can be improved. The method uses the linear and rotational mismatches to increase the fringe densities along directions parallel and perpendicular to the grating lines. As a result greater precision can be obtained in the plotting of curves of partial slopes which are used for determination of curvatures and twists of the flexed plate.
Precision casting of epoxy-resin photoelastic models
Authors: Fessler H , Perla M
Published: July 2007

Photoelastic models may be made by four different methods:

by machining from fully cured blocks;

by machining of oversize simplified castings;

by cementing of machined parts;

by accurate casting to the same shape as the prototype.

A method of casting models to the same proportional accuracy as the prototype and its limitation are described. In this technique a pattern is coated with silicone rubber which is supported by an epoxy-resin casing. Curing shrinkage and differential thermal expansion of the epoxy casing, rubber coating, and Araldite casting are factors which essentially influence the resulting accuracy of the cast models.
Rubber model for adhesive lap joints
Authors: Adams R D , Chambers S H , Del Strother P H A , Peppiatt N A
Published: July 2007

Models of adhesive joints have been constructed in which hard rubber has been used as the adherends and relatively soft foam rubber as the adhesive. The models were scaled to represent various types of lap joint. Very good agreement was obtained when the experimental results were compared with available theory, showing that the model accurately represented the shear-stress distribution in the adhesive.

Two joints are shown in which the adhesive thickness was profiled (one optimally, the other linearly) to reduce or eliminate the shear-stress concentration at the ends.
Contact between a curved viscoelastic beam and a rigid plane
Authors: Granstam I
Published: July 2007

The following problem has been analysed by the theory of small deflections of bending. A circularly curved beam of Maxwell material is pressed against a rigid horizontal plane by two constant and concentrated forces P, each acting on one end of the beam.

Before loading there is contact only at the mid-point of the beam. As load is applied the Maxwellian beam behaves like a Hookean beam. If the load P is below a critical value Pc, there is contact only at the mid-point, but if the load exceeds this value, linear contact is formed along a certain length 2λ° of the beam.

At the time t the beam will rise from the support over a distance of 2λ° ( t) if the load P exceeds Pc, while if P is less than Pc there will be a similar deflection only after a critical time tc. The contact pressure is two concentrated forces, acting on each contact point.

Expressions for the deflections w(O, t) and w( L, t) of the centre and the ends of the beam are also derived and are compared with corresponding expressions for a Hookean beam. The paper shows that essential differences can exist between contact problems with similar viscoelastic or elastic bodies.
Combined tension-torsion creep of polyethylene with abrupt changes of stress
Authors: Ewing P D , Turner S , Williams J G
Published: July 2007

It is shown that the strain response of low-density polyethylene to a variety of complex loading conditions may be described by a standard plasticity equation. The apparatus was modified slightly, from its original form, though the experimental procedures were essentially unchanged from those described in an earlier paper. The results show that the equivalent stress and strain equations can be used with some confidence in design calculations and the tensile data which are widely available for polyethylene can be applied to general problems involving combined stress.
Strains and stress-concentration factors in plates under out-of-phase biaxial cyclic loads
Authors: Saxena V C , Machin K E
Published: July 2007

An elastic theoretical analysis for the strains in an infinite plate and the stress-concentration factors for small elliptical holes in an infinite plate, under sinusoidally varying alternating out-of-phase biaxial loads, is presented. The experiments were performed to substantiate a theoretical analysis for circular and elliptical holes by means of a specially designed and built ‘biaxial cyclic stress machine’. For biaxial alternating stresses, the stress-concentration factor is defined as the ratio of the amplitude of the maximum alternating stress around the geometrical discontinuity to the larger of the amplitudes of the two principal alternating stresses which would occur at the same point if the geometrical discontinuity were not present. Both values are considered over a stress cycle. The results of the theoretical analysis are presented in the form of curves which show the effect of phase differences between stresses and strains upon stress ratio and cyclic stress-concentration factors. The test results of the experiments are also summarized in the form of the curves. Since the experiments were performed on a finite plate compared to an infinite plate considered for theoretical analysis, the experimental curves do not coincide with the theoretical curves. But in general the experimental curves follow the same trends as the theoretical curves. Fatigue implications of out-of-phase biaxial cyclic loads are discussed.
A simple model of uniaxial creep recovery and stress relaxation based on residual-stress redistribution
Authors: Addleman R L , Webster G A
Published: July 2007

A useful and simple model describing primary creep, creep recovery, and stress relaxation is put forward. The model is based on the concept that creep recovery and stress relaxation occur as a result of the redistribution of internal stresses within materials. These internal stresses result from the inhomogeneity of crystalline materials on a microscopic scale, the stresses being attributed to the constraints between neighbouring grains, to the coherency strains associated with solute atoms and second-phase particles, and to dislocation interactions.

It is shown that the model satisfactorily describes the creep-recovery and stress-relaxation properties of commercially pure copper. It also predicts a number of other experimental observations. These are (1) that creep strain recovered will be proportional to the originally applied stress and less, in most circumstances, than the initial elastic loading strain, (2) that creep recovery in single crystals of pure metals will be negligible, and (3) that creep recovery in highly alloyed materials will be greater than in relatively pure metals.

The analysis is limited to loading within the elastic range, but this is not an essential feature of the model and the effects of plastic strain on loading are discussed.
Limit loads of variable-thickness circular plates accounting for transverse shear
Authors: Haydl H M , Sherbourne A N
Published: July 2007

Limit loads of variable-thickness circular plates are given for the von Mises yield condition. The plates are loaded with a uniform transverse pressure and are hinge supported at the edge. The effect of transverse shear on the yield condition and the collapse load is examined. It is shown that the inclusion of transverse shear in the analysis leads to restrictions on the edge thickness of the plates.
Calculation of stress-concentration factors for grooved shafts in bending using the point-matching technique
Authors: Matthews G J , Hooke C J
Published: July 2007

A general numerical technique is presented for the solution of the problem of elastic bending of axisymmetric bodies. Results obtained by this method are compared with existing results for grooved and shouldered shafts in pure bending and good agreement is obtained in each case. Additional results are presented for the stress-concentration effect of flat-bottomed circumferential grooves in cylindrical shafts for which no experimental or analytical results are available.
A biaxial-tension creep-rupture testing machine
Authors: Hayhurst D R
Published: July 2007

The machine is used for the creep-rupture testing of metallic plate specimens at temperatures up to 210°C. A deadweight lever arrangement exerts independent steady tensile loads of up to 8 tons to cruciform plate specimens 9 in wide and 0.25 in thick; the central uniformly stressed region of the specimen is thinned to a thickness of 0.190 in.
Interpretation of tensile and compressive creep behaviour of two nickel alloys
Authors: Tilly G P , Harrison G F
Published: July 2007

The tensile and compressive creep behaviour of Nimonic 90 and Nimonic 108 have been studied at 700–900°C and the strain-time curves were found to have similar shapes. At the higher temperatures, both alloys exhibited tertiary creep under compression at strains less than 2 per cent. In Nimonic 108 each stage of the curves coincided for tension and compression, and tertiary deformation was exhibited only at 900°C. For Nimonic 90 tertiary deformation in compression occurred above 700°C and was delayed relative to tension at each temperature. In all cases the primary and secondary stages of deformation coincided.

It appears that the more rapid development of tertiary creep in tension is due to the development of cracks and their influence on recovery processes. It is suggested that the structural recovery is mainly through development of zones adjacent to grain boundaries that are denuded of γ′ precipitate.
Effect of poisson's ratio strains in adherends on stresses of an idealized lap joint
Authors: Adams R D , Peppiatt N A
Published: July 2007

Poisson's ratio strains in the adherends of a simple adhesive lap joint induce transverse stresses both in the adhesive and in the adherends.

Two simultaneous second-order partial-differential equations were set up to describe the normal stresses along and across an adherend and were solved both by an approximate analytical method and a finite-difference technique: the two solutions agreed closely. The adhesive shear stresses can then be obtained by differentiating these solutions. The transverse shear stress has a maximum value for metals of about one-third of the maximum longitudinal shear stress, and this occurs at the corners of the lap, thus making the corners the most highly stressed parts of the adhesive.

Bonding adherends of dissimilar stiffness was shown to produce greater stress concentrations in the adhesive than when similar adherends are used.
Stresses in a pressurized ribbed cylindrical shell with a reinforced hole
Authors: Durelli A J , Parks V J , Lee Han-Chow
Published: July 2007

The stresses in a ribbed cylindrical shell with a reinforced circular hole, when the shell is subjected to internal pressure, were obtained by several experimental methods: brittle coating, electrical strain gauges, and photoelasticity. The results obtained were compared with those corresponding to a non-reinforced hole in a ribbed and unribbed shell and also to a reinforced hole in an unribbed shell.
Free vibration of initially stressed solids, with particular reference to centrifugal-force effects in rotating machinery
Authors: Bossak M A J , Zienkiewicz O C
Published: July 2007

Initial stresses due to centrifugal forces or other causes change the stiffness characteristics of a solid in a manner which can be simply formulated.

The effect is incorporated in a programme using isoparametric solid elements and it is shown that excellent results can be obtained for a diverse range of problems. Indeed the use of ‘reduced integration’ technique allows the extreme problems of thin plates and shells to be treated by the same element.

The proposed formulation is particularly useful for turbine and compressor blades where the geometry changes from thick solid section to thin plate or slab.
Approximate calculations for the radial expansion of thin tubes used in pressure transducers
Authors: Dean J S
Published: July 2007

A simple set of equations is derived to determine the position and amplitude of the maxima on the radial-deflection curve for thin tubes under uniform pressure, a problem of interest to instrument designers.
Creep of thermoplastics under uniaxial, shear, and hydrostatic stress conditions
Authors: Benham P P , Mallon P J
Published: July 2007

Creep data obtained from p.v.c., p.m.m.a., and p.p. sheet in uniaxial tension and compression, shear, and hydrostatic compression were used to test analytical correlating procedures. It was shown that shear and uniaxial creep could be closely related through the concept of shear stress and shear strain on octahedral planes. Volume strain in uniaxial creep was expressed in terms of the co-ordinate strains and used to predict volume strain in hydrostatic compression. These correlating procedures were only effective if due allowance was made for the different creep responses in simple tension and compression for each of these materials. It was also shown that the relations between viscoelastic compliances and strain ratio, which are stress- and time-dependent, have the same form as the relations between the linear elastic constants.
Shrinkage stresses in three-dimensional two-phase systems
Authors: Theocaris P S , Paipetis S A
Published: July 2007

Stress fields, due to polymerization shrinkage of a matrix cast around a three-dimensional array of closely packed inclusions, were studied photoelastically. The composite model consisted of a group of spherical inclusions, made of unplasticized hot-setting epoxy resin and forming a body-centred cubic arrangement, around which a plasticized matrix was cast, so that control over the ratio of matrix modulus to inclusion modulus was possible.

A theoretical approximation to the problem of stress distribution around a single inclusion was also attempted and subsequently found to be in fair agreement with experimental results.

With closely packed inclusions the stress distribution was studied for different degrees of packing and matrix plastification. From these studies further conclusions can be drawn, confirming the validity of the qualitative results stated for a single inclusion.
Strain distribution and elastic-constant measurement using holographic and speckle-pattern interferometry
Authors: Jones R
Published: July 2007

In this paper the problem of interpreting holographic and speckle-pattern interference fringes is discussed. A general theory is described and it is shown how plane strain may be measured by use of holographic interferometry. Certain limitations inherent in holographic interferometry are elucidated and it is demonstrated how these are eliminated if speckle-pattern interferometry is used. In the final section of the paper a technique is described in which holographic or speckle-pattern interferometry is used to determine accurate values of Poisson's ratio and Young's modulus.
Applications of holography and speckle photography to the measurement of displacement and strain
Authors: Archbold E , Ennos A E
Published: July 2007

Holographic interferometry was used to investigate the behaviour of a plastic pipe joint when subjected to internal pressure. By a combination of ‘live’ and double-exposure techniques the variation of bending moment along an axial surface generator of the joint can be evaluated. To obtain the surface strain, an interferometric technique using speckle photography was used. An important practical factor is the method of mounting the object. For the measurement of much larger surface movements, such as occur when a cantilever is loaded, simple speckle photography, with subsequent point-by-point analysis of the recorded image, is used.
Holographic detection of cracks
Authors: Luxmoore A R
Published: July 2007

A brief report is given on the detection of fine cracks in concrete cubes and cylinders by holographic interferometry.
Experimental and theoretical fatigue-crack propagation lives of variously notched plates
Authors: Smith R A , Jerram K , Miller K J
Published: July 2007

The fatigue lives of variously notched plates have been determined theoretically and experimentally. Theoretical predictions of fatigue lives involved the determination of stress-intensity factors from finite-element analyses. By invoking a crack propagation law, fatigue-life predictions were made for four specimens.

Fatigue experiments were conducted on four notched plates subjected to end load plus bending. Comparison with theoretical results shows that the experimental lives were greater by factors of 1.30 to 1.54. These results are most satisfactory since (1) a safe prediction of fatigue life has been made for a complex profile subjected to non-simple loading conditions, and (2) a theoretical elastic analysis has sufficed for a situation involving plastic strains.
A diametral extensometer for the measurement of small strains in tension-compression testing
Authors: Oldroyd P W J
Published: July 2007

Diametral extensometers are often used in tension-compression testing. When very small strains are being recorded, indentation of the surface of the specimen by the contacts, which is an effect of the combination of axial cyclic strain and radial contact pressure, is a source of appreciable error. This error can be kept to a minimum by the use of the lightest possible contact pressure. When the specimen has to support the weight of the extensometer or, at least, to keep it in position, it is not possible to use a very low value of contact pressure. With the extensometer here described the weight of the instrument is supported independently of the specimen. Its body incorporates two transducers and therefore does not have to undergo lateral displacements. As contact with the specimen is made through two long probes it is not necessary for the body of the extensometer to rise and fall as changes of length occur in the specimen. Tests on the equipment show that it will record small strains with a high degree of precision. Because of this the testing machine functions well when operated under the strain control system.
An inexpensive voltage-stabilized power supply for strain-gauge applications
Authors: Unvala B A , Green A K
Published: July 2007

The development of a simple, inexpensive power supply for strain-gauge applications, with a long-term voltage stability of better than 1 part in 1000, is described.
Prediction of earing in cups drawn from anisotropic sheet using slip-line field theory
Authors: Sowerby R , Johnson W
Published: July 2007

Anisotropic slip-line fields have been developed in the flanges of drawn cups and used to predict the location of the ears and hollows at the onset of the drawing operation. The analysis is based on Hill's plane-strain theory of anisotropic metals. The material anisotropy is characterized by a lumped anisotropic parameter c.

Deep-drawing tests were performed on circular blanks cut from anisotropic sheet and the actual deformation mode of particles in the flange was compared with the theoretical predictions. The correlation was found to be favourable.
Reinforced openings in plastically deforming plates: A finite-difference analysis
Authors: Budney D , Svensson N L
Published: July 2007

This investigation deals with the stress and strain distribution in a large plate containing a reinforced circular hole when loaded monotonically in uniaxial tension beyond the elastic range. The hole is reinforced with a cylindrical member which is symmetrical with respect to the plate to which it is continuously joined. Consideration is given to various degrees of plastic deformation of plate and reinforcement corresponding to various uniaxial tension loads. Whole-field analyses of the reinforcement in cylindrical co-ordinates and of the plate in plane polar co-ordinates are obtained by the finite-difference method in which the governing equilibrium equations are expressed in terms of displacements and plastic strains. Deformation theory of plasticity is employed. Limitations of the ‘compact’ reinforcement assumption result from the subsequent whole-field investigation.

Results are obtained for material of a specific stress-strain curve so that strain-gauge results could be compared with the strains predicted by the finite-difference analysis. It is demonstrated that the compact reinforcement is adequate for analysis of the plate, but for a very significant range of reinforcement geometry it neglects a more serious stress concentration in the reinforcement. For the whole-field analysis, prediction of first yield is made for four critical points: tensile-stress concentration in the plate; tensile-stress concentration in the reinforcement; and shear-stress concentrations in both plate and reinforcement at their joint.
Measurement of dynamic and static strain in small specimens at elevated temperatures
Authors: Sumner G
Published: July 2007

A method of strain measurement in small specimens is described which involves measurement of strain in terms of the net displacement of reference points within the specimen ends rather than on the gauge length. The reference points are the bottoms of axial holes drilled into the specimen heads. The method has been developed for high-frequency dynamic-strain measurement using a novel electro-optical displacement transducer and for low-frequency creep-fatigue work using conventional displacement transducers.
Shear stiffness of a glass-reinforced thermoplastic
Authors: Ogorkiewicz R M , Weidmann G W
Published: July 2007

Inclusion of glass fibres in plastics has been thought to produce little improvement in their stiffness in shear compared with that in tension but results obtained with polypropylene filled with fibres show that they increase in shear stiffness to a significant extent and in some directions more than its tensile stiffness.

The filling of polypropylene with glass spheres instead of fibres results in smaller but still significant increases In shear stiffness, which are comparable to the relative increases in tensile stiffness.

In both cases the experimentally determined values of shear stiffness fall within the bounds derived from energy considerations and correlate closely with the results obtained from a simple model of a composite material
Interaction of a rapidly moving crack with a small hole in polymethylmethacrylate
Authors: Ishikawa K , Green A K , Pratt P L
Published: July 2007

The behaviour of a rapidly moving crack around a small hole in p.m.m.a. (polymethylmethacrylate) has been investigated, by the use of ultra-high-speed photographic techniques, to measure the changes in dynamic stressintensity factor and crack velocity. Cracks were initiated by explosively driven wedge impact, and penetrated holes of diameters of 1/16 in (1.56 mm) and 1/8 in (3.12 mm). The cracks propagating after the hole show a higher velocity than those prior to the hole, though the dynamic stress-intensity factor decreases. There is no general relation between the dynamic stress-intensity factor and the surface roughness for the higher-velocity crack.
A lower-bound limit pressure analysis for the oblique intersection of a flush cylindrical nozzle and the torus of a cylindrical vessel with a torispherical end
Authors: Dinno K S , Gill S S
Published: July 2007

A lower-bound limit analysis is presented for the calculation of the limit pressure for the oblique intersection of a flush cylindrical nozzle and the torus of a cylindrical vessel with a torispherical end. A rotationally asymmetric formulation of stress resultants is specified in assumed plastic regions in terms of an independent set of variables and the limit pressure is computed for a limited number of geometric parameters by a non-linear programming method.
Behaviour of brazed pipe flanges with separate clamping rings
Authors: Fessler H , Perry D A
Published: July 2007

Three pairs of aluminium-brass 100-mm-bore flange models with different surface finishes of the joint faces have been subjected to known bolting forces and internal pressures up to seven times the rated pressure at room temperature. Hard and soft flat gaskets were used and it was found that the joint efficiency was independent of gasket material, surface finish, and initial bolt tension.

Surface strains on the outer surfaces of the tubes and flange rings were measured with electrical-resistance strain gauges where these could be fitted. These results are also presented. The flanges did not fail; tests ended when the loose steel rings touched owing to excessive deformation, so that the gaskets were prevented from sealing.
Torsional behaviour of prismatic shell of variable cross-section through finite-difference approach
Authors: Ganesan N , Ramamurti V , Rao B V A
Published: July 2007

This paper presents a finite-difference approach for analysing prismatic shells of varible cross-section. Such shells have wide application in machine tools and mechanical handing. The construction of the design model allows for warping and distortion. The problem is formulated by use of Vlasv's variational method and solved by means of a finite-difference technique for various boundary conditions. The results are compared with those obtained by use of the cylindrical-shell theory developed by Krishanamurthy and the theoretical and experimental results obtained by Kristek. A study of the influence of various geometric parameters such as thickness of shell, length of shell, taper angle, and number of diaphragms is also made.
Centrifugal stresses in arbitrarily laminated, rectangular—anistropic circular discs
Authors: Bert C W
Published: July 2007

The problem is formulated as one in the linear theory of thin, laminated, anisotropic elastic plates. A direct force-and-moment formulation is used, simplifying approximation is introduced and a closed-form solution is obtained. This solution exhibits bending-stretching coupling if the plate is asymmetrically laminated with respect to mass or stiffness or both. Numerical results typical of certain composite materials of current interest are presented. Specific laminates considered as examples include (1) glass—epoxy/steel, (2) cross-ply graphite—epoxy, and (3) various quasi-isotropic layups of organic fibre—epoxy.
Generalization of the torsional properties of six spring steels
Authors: Swift W A C
Published: July 2007

The plotting of idealized torsional charatertics for spring steels in the form of stress-ratio diagrams shows that a single diagram closely represents the basic stress vs strain curve. It is also shown how corrections may be made to allow for the effect of the knee of the stress vs strain diagram.
Pressurized right-angled reinforced discontinuous bend—effect of reinforcing ring displacement
Authors: Holland M.
Published: July 2007

The condition of ‘perfect clamping’ is discussed and it is shown that even for a reinforcing ring having a depth equal to one half the cylinders' diameter it is still necessary to make some allowance for radial displacement at the oblique edge. Reasons are suggested for the lack of symmetry in circumferential and axial stress profiles over the range ‘intrados’ to ‘extrados’.
Holographic method giving stress levels and visualization of defects in thick cylinders
Authors: Martin D J V
Published: July 2007

The holographic determination of stress-levels in a defect-free tube and in the sound section of a tube containing defects. A comparison with stress values using thick cylinder theory is given, and the tube surface area adversely affected by the defects is visualized, Size of defects detectable are also given.