bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recommendations for the measurement of R-curves using centre-cracked panels
Authors: Wheeler C , Eastabrook J N , Rooke D P , Schwalbe K-H , Setz W , De Koning A U 
Published: July 2007

Experimental techniques for obtaining the R-curve, a measure of fracture toughness used for selection and quality assurance of thin-section materials, are discussed in the light of experience at RAE, DFVLR, and NLR. Detailed recommendations are made for R-curve measurement using centre-cracked panels. To improve standardization, the procedure is more closely defined than in the proposed recommended practice for R-curve determination of the American Society for Testing Materials (ASTM), but machining costs are reduced by relaxing tolerances on specimen dimensions. The crack length is measured by either a potential-difference of a compliance method, and the specimen is loaded to give uniformly increasing load-point displacement of crack-opening displacement. Constant rate of increase of load is not recommended. Optical measurement of crack length is not recommended. The R-curve is calculated by a method which avoids giving undue weight to measurements made at zero or small crack extensions.
Determination of fracture toughness of ductile materials using a reinforced double cantilever beam specimen
Authors: Woo C W , Kuruppu M D 
Published: July 2007

A method of determining the fracture toughness of ductile material in the form of a reinforced double cantilever beam (RDCB) specimen is presented. The analysis makes use of the Dugdale strip yield model incorporated in the beam-on-elastic foundation model to represent the fractures of a DC3 specimen. Two different foundation models are considered. The first model assumes that one half of the RDCB acts as the elastic foundation for the other half and the second model assumes that the groove acts as the elastic foundation. The results of the groove foundation model are found to be closer to the experimental values based on the crack growth resistance curves than those of the beam foundation model. The results are further verified using a J control integral determination based on a two dimensional elastic-plastic finite element analysis. The material used is 2024-T3, which is moderately ductile, and the proposed method yields fracture toughness values with a reasonable degree of accuracy.
Pressurized non-circular member—effect of mean-line form
Authors: Holland M 
Published: July 2007

Using an energy analysis, it is shown that for each aspect ratio and for a particular family of curves representing the mean-line form, there will be one particular form which ensures that the maximum bending moment acting on the member takes a minimum value. The traditional elliptic mean-line form currently used for some heat exchanger tubes, sluice-value bodies, and some aircraft monocoque stiffening frames, could be improved by using the optimum form which has heat transfer and fluid-flow characteristics similar to those associated with the elliptic profile (sometimes an essential feature of the design). It is shown that when the aspect ratio is equal to two and the elliptic shape is replaced by an optimum form determined by the method described above, the uniform applied pressure can be increased by fifteen and one-half per cent before the maximum stress in the two members becomes equal.
Thermal ratchetting of axially loaded tubes operating in the creep range
Authors: Hyde T H , Webster J J , Fessler H 
Published: July 2007

Finite element predictions of ratchetting and creep behaviour are compared with experimental data for axially loaded tubes subjected to axisymmetric cyclic temperature variations. Eleven tubes made of a lead alloy model material which creeps at ambient temperature were tested. Strain gauges were used to measure the ratchet and creep strains. In the finite element calculations it was assumed that no plasticity-creep interactions occur. Reasonably good predictions of ratchet strains were obtained, particularly in the range of most practical interest. Some of the discrepancies between ratchet and creep results can be accounted for by considering the results from a small number of uniaxial plasticity-creep interaction tests.
Experimental theramal ratchetting data for a component with a stres concentration
Authors: Hyde T H , Webster J J 
Published: July 2007

The result from eleven tests of lead alloy model shouldered tubes, subjected to constant axial mechanical loads and cyclic, axisymmetric thermal shocks are described. Dwell periods between 0.5 h and 24 h allowed creep to occur between the thermal shocks. Electrical resistance strain gauges were used to measure ratchet and creep strains. At low mean axial stresses (< 0.94σy), it was found that the ratchet strains increased with load and dwell period. It was also found that the ratchet strains in the fillet region were significantly larger than those in the shank and are induced at lower mechanical loads than those in the shank. For higher stresses, the ratchet strains were found to be relatively insensitive to both load and dwell period. Also, the ratchet strains in the fillet and shank were found to be of the same magnitude.
Predicting the thermal ratchetting and creep behaviour of a component with a stress concentration
Authors: Hyde T H , Webster J J 
Published: July 2007

Finite element and ‘upper bound’ predictions of ratchetting and creep are compared with experimental data from two axially loaded shouldered tubes subjected to axisymmetric cyclic temperature variations. The shouldered tubes were machined from chill-cast bars of a lead alloy material. Electrical resistance strain gauges were used to measure the ratchet and creep strain. The results show that ratchet strains can accumulate significantly faster in stress concentration regions when compared with plain tube regions. Acceptable predictions were obtained for the ratchet strains. The discrepancies between the predicted and measured dwell period strains were due to neglecting the material plasticity-creep interactions. Some simple methods for estimating the strains are suggested.
Stress concentrations due to axial tension and bending of loaded axisymmetric projections
Authors: Hyde T H , Marsden B J 
Published: July 2007

The finite element method has been used to investigate the behaviour of axisymmetric loaded projections (e.g., bolts) subjected to axial tension and bending. The results show that existing data for stepped shafts, which have the axial tension and bending loads applied remote from the region of the step, cannot be applied to loaded projections with the same geometry. For h/d (head thickness to shank diameter ratio) values greater than 0.66 and 0.41 for axial tension and bending, respectively, the stress concentration factors are independent of h/d, load position, and D/d (head diameter to shank diameter ratio) for D/d in the range 1.5 ≤ D/d ≤ 2.0. Smaller h/d values result in large increases in the stress concentration factors due to dishing of the head.
Stresses in a bottoming stud assembly with chamfers at the ends of the threads
Authors: Fessler H , Jobson P K 
Published: July 2007

Three-dimensional, frozen-stress, photoelastic models of 1 in. BSW studs and tapped blocks have been loaded axially and in torsion. Detailed distributions of axial, principal, and shear stresses show that, as expected, the greatest stresses occur near the front end of engagement, but there are secondary peaks near the back end due to the stresses set up by ‘locking’ the stud at the bottom of the hole. Chamfering the first two turns of the thread of the block eliminates the stress concentration at the front of the block itself but does not reduce the stud stresses significantly. Similarly, the stresses at the back of engagement are reduced if the stud thread is chamfered.
Three-dimensional, elastic stress distribution in end-milled, keyed connections
Authors: Fessler H , Eissa M 
Published: July 2007

Three- and two-dimensional, photoelastic, frozen-stress models of Standard metric and inch keyed connections have been loaded in torsion. Results from models with three different key lengths are presented here and related to the axial distribution of torque transmission. Empirical equations for the elastic stress concentrations in the prismatic part of key and keyway at the positions of contact between key and shaft have been derived for any likely width, thickness, and length of key, keyway fillet size, and applied torque. A simple method of eliminating stress concentrations in the keyway end is described.
Determination of stable crack growth resistance of ductile material using an rdcb specimen
Authors: Woo C W , Kuruppu M D 
Published: July 2007

A method to determine the plane stress fracture resistance curve for the stable crack growth of ductile material is presented. A reinforced double cantilever beam (RDCB) specimen of thin grooved section is used to determine the COD and JR of aluminium 2024-T3 material which exhibits substantial stable crack growth. The method makes use of the BEF and Dugdale models to determine the load-deflection behaviour of the specimen. The derivation is based on the experimentally determined load and crack extension values. The crack growth resistance for specimens of different thicknesses are deduced using the proposed method and are compared with those of the compliance method as well as the finite element method.
Elastic-plastic-creep behaviour of a compact-tension specimen
Authors: Hyde T H , Low K C , Webster J J 
Published: July 2007

Elastic, elastic-plastic, elastic-creep, and elastic-plastic-creep finite element calculations have been performed for a compact-tension specimen under plane-stress conditions. The von-Mises effective stress criterion and the Prandtl-Reuss flow rule were assumed for both the plastic and creep deformations. A 4-line stress-strain relationship with a UTS value 1.48 times greater than the yield stress was used. A strain hardening, Norton-Bailey creep law was assumed. A fairly course mesh of 8 noded, isoparametric elements was found to be adequate for determining reference stress, crack tip opening displacement, J-contour integral, and C∗-contour integral values. The UTS zone, rather than the yield zone, was found to have a significant effect on the C∗-contour integrals and CTOD rates. An approximate method of determining C∗ values was found to give reasonable results, particularly for low load cases, i.e., when the UTS zones are small. Hence, provided care is taken not to perform tests at very high loads, accurate C∗ values can be determined from experimentally determined pin displacement rates.
Deformation and stability studies of thin-walled domes under uniform external pressure
Authors: Ross C T F , Mackney M D A 
Published: July 2007

Fifty hemiellipsoidal domes were cast in solid urethane plastic, with profiles which varied from oblate to prolate shapes. The domes were subjected to external hydraulic pressure in a test tank and tested to failure. All the domes appeared to fail through elastic instability, the oblate shapes failing axisymmetrically, and the prolate shapes failing asymmetrically in a lobar manner. The theoretical analysis was carried out via the finite element method, and stiffness matrices were developed for an axisymmetric element of constant meridional curvature. The element was capable of being applied to axisymmetric deformation or axisymmetric and asymmetric instability, and it was generated numerically.
Mode I and II fracture of adhesive joints
Authors: Anandarajah A , Vardy A E 
Published: July 2007

The compliance method is used to determine strain energy release rates in mode I and II fracture of adhesive bonded joints. A strong dependence of the strain energy release rates upon the adhesive thickness is found. Standard compact tension and compact shear specimens are used. It is found that the former are well suited to the investigation of mode I fracture, but that the latter are less well suited to mode II investigations. Attention is focussed on bond failures caused by cracks propagating between an adhesive and an adherend. Experimental and theoretical arguments are combined to determine the critical strain energy release rates at which such failures occur. The critical values are shown to be strongly dependent upon the method of surface preparation as well as upon the physical properties of the materials used.
Multiaxial strength tests for brittle materials
Authors: Fessler H , Fricker D C 
Published: July 2007

Matchstick and coin shaped specimens are used to determine the material strength consistency and mean fracture strength under five different stress rations, using Weibull statistics. Many practical loading modes of these simple shapes are assessed. For the best, the necessary experimental work and results of the analyses are presented and illustrated for as-fired reaction-bonded silicon nitride (RBSN) tested at room-temperature.
Stresses in axially loaded cylinders with imperfections and cracks
Authors: Godoy L A , Croll J G A , Kemp K O 
Published: July 2007

The combined effects of imperfections in the form of the meridians and meridional cracks in axially loaded cylindrical shells are studied by means of a finite element programme capable of handling well defined, discrete cracks. Two basic mechanisms are shown to occur in shells in such a state: first, a redistribution of vertical load away from the cracked zone, and second, a redistribution from hoop membrane to meridional bending action. The mechanics of behaviour of shells with imperfections in the geometry and cracks are systematically studied by examining the effects of shell, imperfection, and crack characteristics, so that the dominant parameters controlling the linear elastic response of the shell can be isolated. Numerical experiments show that those parameters that influence the behaviour in an uncracked imperfect shell also influence the stresses accompanying cracking.
Experiments on perforated plates subjected to shear
Authors: Narayanan R , Chow F Y 
Published: July 2007

Experiments on the buckling and ultimate capacity of thin-walled steel web plates containing circular and square cut-outs are reported. Some 64 tests were carried out on plates containing either one or two holes. The parameters varied included the size of the hole and the eccentricity of the location of the hole. For an increase in the eccentricity of the hole, the shear buckling coefficient increased when the opening was located in the compression diagonal and decreased when it was in the tension diagonal; it was found to be insensitive to the location of the hole, for small openings. Approximate formulae are suggested in the paper for computing the shear buckling coefficients for plates with central and eccentric holes, and are suitable for use by designers. A method of predicting accurately, the ultimate capacity of the web is presented.
Stress analysis of some nut-bolt connections with modifications to the nut thread form
Authors: Kenny B , Patterson E A 
Published: July 2007

Six photoelastic frozen stress models of ISO nut-bolt connections loaded in pure tension were studied. Four of these models had modifications to the threads at the load bearing end of the nut. These modifications included tapered truncation of the thread crests and taper of the whole thread form for a portion of the nut length. The maximum stress in the bolt always occurred within one pitch of the load bearing face of the nut. Truncating threads increased the maximum bolt stresses. Tapering the whole thread form reduced the maximum stress and produced a more uniform load distribution in the bolt. The conditions at the load bearing face of the nut were found to influence the load distribution in the bolt threads more than the stress concentrations in the bolt.
Ratchetting tests of a stepped beam under steady tension and cycling bending
Authors: Fessler H , Hyde T H 
Published: July 2007

Seven identical stepped beams, made of a lead alloy, were loaded by steady tension and cyclic bending. Three bending moments superimposing equal hogging and sagging were used in the tests. Six different tensions were also used. After test of 15 cycles, most beams were re-loaded with a greater mean tension and the same cyclic bending moment. Strains were measured in the (circular arc) fillets at the step and in the shank. Ratchetting strains per cycle decreased during each test; steady values were estimated and related to the load magnitudes. The common use of the 0.2 per cent proof stress as the yield stress for an equivalent elastic-perfectly-plastic materials has been shown to be extremely conservative.
An experimental investigation of slow stable crack growth using hy130 steel
Authors: Etemad M R , Turner C E 
Published: July 2007

Fracture toughness in terms of J and COD at or beyond initiation to ductile tearing were investigated using mainly three point bend pieces of HY130 steel in a variety of proportions. J values are adjusted for crack growth to obtain the resistance curve ( R-curve). The R-curve was observed to become shallower with increasing width and thickness of test piece, and for longitudinal (TL) rather than short transverse (TS) crack propagation, but steeper with scaling to smaller absolute sizes, and decreasing thickness and width. For full thickness plates, the R-curve for tension was much steeper than bending. Discussion is given on the size requirements for a geometry independent R-curve, according to the present test data.
Microcomputer design analysis of plate post-buckling behaviour
Authors: Rhodes J 
Published: July 2007

Explicit formulae are presented for the examination of plate post-buckling behaviour. Plates with simply supported loaded ends and having simply supported, fixed, or some intermediate, elastic restraint on edge rotation are considered, and it is assumed that the unloaded edges are free to wave in their own plane. The coefficients used in the equations were derived on the basis of curve fitting to a large number of computer solutions and are applicable to any buckle half wavelength or rotational restraint condition normally found in engineering structures. These equations are sufficiently simple to provide extremely rapid predictions of plate behaviour on any small microcomputer. Comparisons are made with some existing published results and the effects of imperfections, degree of edge rotational restraint, and buckle half wavelength are illustrated. The behaviour predicted for plates in the far post-buckling range is examined and shown in comparison with the design formula of von Karman. It is suggested that, for accurate plate design, strength and stiffness should be considered separately, and that the effects of rotational edge restraint should be taken into account in both buckling and post-buckling analysis.
The optimisation of the design of nuts with partly tapered threads
Authors: Patterson E A , Kenny B 
Published: July 2007

The angle of taper and the number of tapered threads in a nut necessary to give the lowest maximum stress concentration in the bolt were determined for an ISO nut—bolt connection subject to axial loading. Thirty-eight frozen stress models were analysed and it was found that a two degree taper for 5.5 threads from the loaded face of the nut reduced the maximum normalised tensile stress in the bolt by 41 per cent from 5.17 to 3.07. It was observed that if the angle of taper was too large the stress concentration produced at the junction of the parallel and tapered threads could negate the beneficial effects of the taper geometry.
A computerised design aid for drive shafts with some fatigue considerations
Authors: Walton D , Prayoonrat S 
Published: July 2007

A method of designing power transmission drive shafts is described based on two interactive computer programs. The first program can model shafts of any configuration and under any system of loads and supports. The program is based on the finite element method. Reducing the size of the stiffness matrix by storing only the parameters in the matrix bandwidth and by overlaying the stiffness matrices, the problem of using finite element analysis on small memory microcomputers can be solved. A menu allows the designer to specify machine elements, such as spur or bevel gears or pulleys, to be positioned at any point along the shaft. The user can give information of the power transmitted, speed, and details of the physical dimensions of the machine elements which then enables the program to determine the force vectors and apply these to the shaft nodes. The second program determines the design factors of safety on the basis of both static and cyclic loads. For cyclic loads the factors of safety are based on infinite-life design, using Soderberg and Goodman criteria. The program contains extensive built-in data on endurance strengths, factors influencing the endurance limit, and stress concentration factors.
Use of the reference stress concept to assess the effect of crack growth increment size on the accuracy of creep crack grow predictions
Authors: Hyde T H , Low K C 
Published: July 2007

An approximate method, based on the reference stress concept, for carrying out ‘moving-crack’ calculations, under creep conditions, is presented. Creep crack growth is assumed to be related to the C∗ parameter. The predictions obtained correlate well with detailed, ‘moving-crack’, finite element calculations. Preliminary calculations, to assess the adequacy of finite element meshes and the effect of variations in material properties on the accuracy of predictions, can be carried out quickly and relatively cheaply. The usefulness of the technique is illustrated by using it to show the effect of the magnitude of the crack growth increment assumed and of the value of critical crack tip opening displacement (the initiation parameter assumed) used.
Nomographic design procedures for fibre-reinforced metallic rocket motor cases
Authors: Groves A , Margetson J , Stanley P 
Published: July 2007

Nomographic design procedures are developed for a metallic cylinder (e.g., a rocket motor case) circumferentially reinforced with a pre-strained elastic fibre overwind. Techniques for calculating the pressure for first yield in the metallic case and the optimum winding conditions are presented, together with a technique for determining the maximum fibre stress. Design examples are presented with each nomogram in turn and the graphical results are compared with exact numerical values.
Loads, Stresses, and deflections in Bicycle Frames
Authors: Soden P D , Millar M A , Adeyefa B A , Wong Y S 
Published: July 2007

A bicycle frame has been analysed as a three-dimensional framework and stresses and deflections predicted using a finite element computer program. Theoretical results for simple loading case were compared with strain gauge measurements in laboratory tests. More complex loading cases representing common cycle racing situations were analysed. The largest stresses in the frame were bending stresses. Stresses in the region of 300—400 MN/m2 were predicted in the down tube and right chain stay during starting and stresses of about 250 MN/m2 at the front of the top tube and down tube during severe braking.