Showing papers in "Journal of Strain Analysis for Engineering Design in 1970"
TL;DR: In this paper, Tresca's yield criterion and the associated flow rule have been used to develop a solution for the plastic bulging of circular diaphragms by lateral fluid pressure.
Abstract: Tresca's yield criterion and the associated flow rule have been used to develop a solution for the plastic bulging of circular diaphragms by lateral fluid pressure. The strain distribution in the neighbourhood of the pole is derived in explicit form and a new formula is given for the polar strain at instability. The theory is found to be in good agreement with experimental results for the bulge test. A numerical method of solving the problem for Mises materials is also proposed.
64 citations
TL;DR: In this article, simple struts have been impacted between travelling and stationary masses and the collapse was found to consist of two distinct phases: the pre-failure phase, being primarily an elastic region, has been analysed by stability criteria and the post-failures phase by consideration of the plastic collapse of the strut.
Abstract: Part 1: Simple struts have been impacted between travelling and stationary masses and the collapse found to consist of two distinct phases The pre-failure phase, being primarily an elastic region, has been analysed by stability criteria and the post-failure phase by consideration of the plastic collapse of the strut Associated with the pre-failure phase is a large transient deceleration which is found, among other parameters, to be a function of the strut shapePart 2: A series of sheet-metal structures have been impacted and, like struts, the collapse found to consist of pre- and post-failure phases of separate identities The pre-failure phase is again associated with the shape of the structure and may give rise to a large transient deceleration This analysis has led to the consideration of more complex elements, such as might be found in an automobile frontal structure, and finally to a complete automobile analogue Conclusions are drawn about the structural parameters required to bring abou
53 citations
TL;DR: In this article, a series of combined stress tests in torsion-tension space is carried out on thin-walled tubes of 1100-F commercially pure aluminium and the results are analyzed in terms of a proposed, rationally based, yield criterion constructed according to statistical reasoning.
Abstract: A series of combined stress tests in torsion-tension space is carried out on thin-walled tubes of 1100-F commercially pure aluminium. One initial and four subsequent yield loci are established to a maximum prestrain level of 14 per cent tensile plastic strain.The results are analysed in terms of a proposed, rationally based, yield criterion constructed according to statistical reasoning.It is shown that during prestrain a significant degree of geometrical distortion is undergone by the yield loci, accompanied by a strong Bauschinger effect and a flattening of part of the locus opposite to the loading point.It is found that the yield locus does not rotate during prestrain and, contrary to the case for torsion prestrain, exhibits evidence of a sharply rounded corner developing at the loading point.The proposed criterion is shown to fit the experimental results extremely well and the mechanism of distortion is explained in terms of a statistical model for work-hardening materials.
53 citations
TL;DR: In this article, the stiffness matrix is obtained on the basis of stress assumption, rather than the more usual displacement assumption, and an erroneous addition of the shear-deflection terms to the bending terms can be made if an apparently straightforward approach is utilized.
Abstract: Shear-deflection terms arise naturally in a finite beam element in bending if the stiffness matrix is obtained on the basis of stress assumption, rather than the more usual displacement assumption.If the displacement assumption is used, an erroneous addition of the shear-deflection terms to the bending terms can be made if an apparently straightforward approach is utilized.
47 citations
TL;DR: In this article, a rubber elasticity representation was used to analyze polymethylmethacrylate at the molding temperature of 160°C and showed that large strain solutions may be obtaine...
Abstract: Stress-strain data for polymethylmethacrylate at the moulding temperature of 160°C are analysed by a rubber elasticity representation. It is shown that large strain solutions may be obtaine...
31 citations
TL;DR: In this article, the authors present a linear model of cumulative damage, where failure is defined as the termination of the steady-state period, that is at the point of crack growth instability.
Abstract: An hypothesis of cumulative damage is presented that may be expressed mathematically as Σn÷Nf = constant where n is the number of cycles performed at a constant strain range and strain rate and Nf is the number of cycles to failure at the same strain range and strain rate.An initial experimental investigation at room temperature shows that, under constant strain-rate conditions, the load-sequence effect is removed, but the value of the constant is dependent on the definition of failure. If failure is defined as complete rupture the summation term is less than unity whatever the sequence of loading. Should failure be defined as the termination of the steady-state period, that is at the point of crack growth instability, then the summation term is greater than unity. This latter definition therefore leads to a linear law of cumulative damage that gives a doubly cautious prediction of life that is of obvious advantage to engineers.
29 citations
TL;DR: In this paper, stress-concentration factors for relatively deep, constant radii, U-shaped, edge notches in a semi-infinite sheet with uniaxial tension applied parallel to the sheet edge are analyzed.
Abstract: : Stress-concentration factors are analytically determined for relatively deep, constant radii, U-shaped, edge notches in a semi-infinite sheet with uniaxial tension applied parallel to the sheet edge. Because a strong geometric similarity exists between a U-notch and a semi-elliptical notch of the same tip radius, a comparison of such analytical data is effected. Also compared are stress-concentration factors for U-notches in a semi-infinite sheet to other comparable analytical and experimental data available in the literature. Finite width correction factors are applied to the results of the semiinfinite sheet analysis to provide practical design data. Comparisons of such data are made to experimental results provided by a number of investigators. (Author)
29 citations
TL;DR: In this paper, the application of a new thick shell element with reference to vibration problems is described, derived from the general isoparametric solid and therefore allows shear deformations.
Abstract: The application of a new thick shell element is described with reference to vibration problems. The element is derived from the general isoparametric solid and therefore allows shear deform...
29 citations
TL;DR: In this paper, the authors solved the stress analysis of a connecting rod under a tensile load by using a linear elastic finite-element computer program, where a connecting-rod eye was idealized as a plane-stress problem and special elements were introduced to connect the pin and rod together.
Abstract: The stress analysis of a connecting rod under a tensile load represents a non-linear problem, since the distribution of the forces, acting between the eye of the rod and the pin, changes as the loading proceeds. This is due to the tendency of the eye to deform, thus wrapping itself around the pin as the clearance between the parts is reduced. In consequence, the stress pattern in the eye also changes.Such a problem has been solved with a linear elastic finite-element computer programme. A connecting-rod eye was idealized as a plane-stress problem and special elements were introduced to connect the pin and rod together. These elements were assigned stiffnesses which were changed in a prescribed manner after each iteration until compatibility of forces and displacements, with due allowance for initial clearances, was obtained at each connecting point.Although eight iterations were required to achieve the correct displacements, it was found that the circumferential stresses did not change appreciably...
26 citations
TL;DR: In this article, a systematic examination of the mechanical and physical properties of 166 plain and alloyed cast irons and a limited number of engine components was carried out, and it was shown that this situation is best met with an a...
Abstract: Pearlitic flake-graphite grey cast irons have long been widely used for the manufacture of diesel-engine combustion-chamber components. Nonetheless, very few pertinent high-temperature data are to be found in published work. The investigation described attempts to enlarge current knowledge on the high-temperature behaviour of grey cast irons in view of requirements highlighted by high thermal ratings. A general consideration of the problem showed that the often quoted Eichelberg material-quality factor is largely irrelevant and an alternative assessment formula is proposed. This is broadly confirmed by a systematic examination of the mechanical and physical properties of 166 plain and alloyed cast irons and a limited number of engine components.Different engine components impose different demands upon the material properties but for economic reasons a single cast-iron melt capable of meeting most of the requirements of all components is needed. It is shown that this situation is best met with an a...
24 citations
TL;DR: In this article, the effect of strain rate on the cyclic behavior of two materials is presented, and it is concluded that it is better to predict fatigue behaviour from an incremental-step high-strain fatigue test on a s...
Abstract: The effect of strain rate on the cyclic behaviour of two materials is presented. For the material that cyclically hardens (En 32B) a decrease in strain rate decreases the maximum cyclic hardening of the material, whilst for a material that cyclically softens (En 25) a decrease in the rate of deformation increases the maximum cyclic softening. It is concluded that the effect of strain rate on the cyclic stress-strain curve should be more closely studied than the effect of frequency since the frequency may be constant whilst the straining rate may vary considerably in plastically deformed zones. For those zones that suffer low strain rates the inclusion of time-dependent deformation processes can maximize the degree of softening or minimize the degree of hardening, thereby creating a greater localization of the plastic strain which should increase strain-concentration factors. Finally it is argued that it is better to predict fatigue behaviour from an incremental-step high-strain fatigue test on a s...
TL;DR: In this article, the mechanics of thermal self-straining in fiber-reinforced materials are explained and stress distributions obtained from finite-element calculations are compared with results from photothermoelastic analysis of models.
Abstract: The mechanics of thermal self-straining in fibre-reinforced materials are explained. Stress distributions obtained from finite-element calculations are compared with results from photothermoelastic analysis of models.
TL;DR: In this paper, the authors described the application of the point-matching technique to the solution of plane elastic problems and showed that it is possible to produce a single computer program capable of analysing a wide range of such problems.
Abstract: In a previous paper the author described the application of the point-matching technique to the solution of plane elastic problems. It was shown that it is possible to produce a single computer programme capable of analysing a wide range of such problems. The technique is extended in this paper to the case of an axisymmetrically loaded elastic body of revolution. The details of the technique are necessarily more complicated in the present instance but it has proved possible to develop a general computer programme for this type of problem.The application of the method is illustrated for a number of problems for which approximate or experimental results are available. Good agreement between these results and the point-matched stress distribution is obtained in every case.
TL;DR: In this article, the stress distribution in a plane discontinuous-fibre composite material having elastic fibres and an elastic-plastic matrix material is obtained for both non-interacting and interacting discontinuities and different degrees of work-hardening.
Abstract: The stress distribution in a plane discontinuous-fibre composite material having elastic fibres and an elastic-plastic matrix material is obtained for both non-interacting and interacting discontinuities and different degrees of work-hardening. The theoretical predictions, obtained by the finite-element method, are compared with the strain distribution in a model of steel and lead-alloy by the surface-coating photoelastic technique. Composite failure is simulated in the finite-element model and predictions compared with the observations of composite failure made by other workers.
TL;DR: In this paper, commercial photoresists have been examined to assess their suitability for use with the moire method of surface-strain measurement, and some etching and plating procedures are also described.
Abstract: Some commercial photoresists have been examined to assess their suitability for use with the moire method of surface-strain measurement. As most of these materials do not produce a pattern of high contrast directly, some etching and plating procedures are also described. Combined with correct illumination, these processes will produce grids of sufficient contrast for most applications.
TL;DR: In this paper, photoelastic tests have been made on two-dimensional models of steam-turbine flanges for various combinations of the flange parameters depth, width, and bolt position.
Abstract: Photoelastic tests have been made on two-dimensional models of steam-turbine flanges for various combinations of the flange parameters depth, width, and bolt position. Design curves have been produced which show the relation between these flange parameters and the ratio of bolt force to pressure force necessary to produce a compressive stress at the inner edge of the flange equal to the internal pressure, this being the criterion adopted to ensure steam-tightness.Comparisons have been made between the experimentally determined stress distributions and distributions calculated by various methods. Of computer-aided methods, the English Electric Kidsgrove structural-analysis programme gave the best correspondence to the experimental results with a relatively simple idealization of the problem. When the depth of a flange exceeds the width and the bolt load acts within the inner half, the stress distribution is reliably predicted if the flange is assumed to behave as an eccentrically loaded column.
TL;DR: In this paper, the suitability of the birefringent-coating technique for application to fiber-composite materials is examined by considering the three-point flexure of a narrow rectangular beam of span/depth ratio 6 in some detail.
Abstract: Techniques such as birefringent coatings, moire, brittle lacquers, strain gauge, and holography can all be used on composites since they enable surface strains to be measured. However, a correct and accurate interpretation of results obtained by these methods is essential. The significance of this is demonstrated by observing the effect of the differences between the directions of principal stresses and strains.In addition the suitability of the birefringent-coating technique for application to fibre-composite materials is examined by considering the three-point flexure of a narrow rectangular beam of span/depth ratio 6 in some detail. Within the framework of the assumptions that stresses will be distributed in accordance with elementary bending theory and that the appropriate stress-strain relations for orthotropic materials are applicable, isochromatic and isoclinic patterns are predicted and compared with experimental results. A more precise solution is also obtained by employing the finite-ele...
TL;DR: The concept of equivalent smooth bend is examined in this article, where measurements of strain, transverse deflection, and change of radius have been taken on single unreinforced pipe bends subjected to in-plane bending moments.
Abstract: Measurements of strain, transverse deflection, and change of radius have been taken on single unreinforced pipe bends subjected to in-plane bending moments. Specimens having three different mitre angles for each of two sizes of pipe have been used. Observations were made with different combinations of leg lengths for each specimen.Stresses and flexibilities are compared with those calculated by the formulae given in the A.S.A. Piping Code B.31.1 and the concept of equivalent smooth bend is examined. Alternative methods of assessment are considered and improved methods are suggested.
TL;DR: In this paper, the elastic stresses due to internal pressure in 24 pressure-formed vessels have been analysed using frozen stress photoelastic models, and the peak stresses in these shapes are generally lower than in the best torispherical heads of the same head height.
Abstract: Mild-steel vessels with initially flat ends, having four different thicknesses and various knuckle shapes, have been formed without dies. Similar shapes were obtained by forming at room temperature and at a high temperature with saturated steam as the pressurizing medium.The elastic stresses due to internal pressure in 24 pressure-formed vessels have been analysed using frozen stress photoelastic models. The peak stresses in these shapes are generally lower than in the best torispherical heads of the same head height.
TL;DR: In this article, the authors dealt with thermal stresses that arise in discs with eccentric holes, such as are employed in the rotors of multi-stage gas turbines, and analyzed the stress distribution by the photothermoelastic method CR 39 sheets were used as the material and dry ice as the refrigerant.
Abstract: The paper deals with thermal stresses that arise in discs with eccentric holes, such as are employed in the rotors of multi-stage gas turbines The stress distribution was analysed by the photothermoelastic method CR 39 sheets were used as the material and dry ice as the refrigerantThe effect of several geometric parameters on stress distribution, especially the influence of adjacent holes, was investigated by testing 32 configurations of discsCurves that allow the determination of the peak stresses and optimum spacing of holes are given
TL;DR: In this article, an experimental technique has been developed to allow the rapid determination of adhesion and slip areas in steady-state rolling contact, which consists in rolling solid black-rubber toroids on a ground-glass plate under carefully controlled conditions.
Abstract: An experimental technique has been developed to allow the rapid determination of adhesion and slip areas in steady-state rolling contact.The technique consists in rolling solid black-rubber toroids on a ground-glass plate under carefully controlled conditions. It enables the division of the contact area into slip and adhesion areas to be observed and photographed whilst rolling is taking place.A loading frame was devised to enable rolling with longitudinal shearing traction, rolling with transverse creep, and rolling with spin to be investigated either separately or in combinations.The results of the experiments have been compared with existing theories, and some conclusions as to the accuracy of the theories have been made.
TL;DR: In this paper, a simple formula is derived for predicting the flexure of uniformly loaded point-supported circular plates, and the resulting series for the edge moments and shears are summed and are shown to be very similar to a simple sine wave.
Abstract: A simple formula is derived for predicting the flexure of uniformly loaded point-supported circular plates. The classical solution of Michell for a clamped plate under a single point load is extended for any number of point loads regularly spaced around a circle concentric with the plate edge. The resulting series for the edge moments and shears are summed and are shown to be very similar to a simple sine wave. Replacing the exact expressions by single sine waves enables the clamped edges to be set free by a simple superposition of solutions. The point reactions are equilibrated by a uniform load and the resulting deflection surface for a free uniformly loaded point-supported plate is obtained immediately. Deflection curves for the particular case of a plate supported at three points are given in the form of contours of equal deflection. This particular case is compared with some experimental results which were obtained by optical methods.For three supports, maximum deviation from the flat is leas...
TL;DR: The theory of the polariscope, based on Jones's metric equations, is given and the influence of imperfect quarter-wave plates is discussed in this paper, where the effect of light of incorrect wave-length on the resulting error is considered.
Abstract: The isoclinic parameter can be determined from points of intersection of two systems of characteristic lines called secondary isochromatics. These lines, along which the light intensity is a minimum, can be observed in monochromatic light in an originally linear polariscope with two crossed quarter-wave plates in which the polarizer and analyser have been rotated through small angles in opposite direction.The theory of the polariscope, based on Jones's metric equations, is given and the influence of imperfect quarter-wave plates is discussed. The effect of light of incorrect wave-length on the resulting error is considered. A disc loaded by two opposite compression forces is used for demonstration of the methods.
TL;DR: A report on the Fourth International Conference on Stress Analysis held at Cambridge, England, on 6-10th April 1970 is given in this article, with a focus on stress analysis.
Abstract: A report on the Fourth International Conference on Stress Analysis held at Cambridge, England, on 6-10th April 1970.
TL;DR: In this article, the authors present a shorter version of a more detailed treatise by the author, which consists of two parts: the empirical determination of certain characteristics of a material by means of a relatively small number of standard tests, and the arithmetical application of the results obtained to arbitrary loading histories.
Abstract: The present work is a shorter version of a more detailed treatise by the author (1)∗. The method consists of two parts: the empirical determination of certain characteristics of a material by means of a relatively small number of well defined standard tests, and the arithmetical application of the results obtained to arbitrary loading histories. The following groups of parameters are thus taken into account: the variations of the mean stress; the interaction of these variations and the superposed oscillating stresses; the spectrum of the oscillating-stress amplitudes; the sequence of the oscillating-stress amplitudes.
TL;DR: In this paper, the authors described an analysis for plates that made use of non-linear large-deflection theory and compared the results of the analysis with measurements of deflections and str...
Abstract: A previous paper (1)∗described an analysis for plates that made use of non-linear large-deflection theory. The results of the analysis were compared with measurements of deflections and str...
TL;DR: In this paper, the feasibility of using the moire technique to measure crack opening displacements smaller than 0·001 in and areas of plastic flow immediately beneath the notch was investigated.
Abstract: This paper describes some initial experiments carried out on zirconium notched bend specimens, to determine the feasibility of using the moire technique to measure crack opening displacements smaller than 0·001 in and areas of plastic flow immediately beneath the notch.
TL;DR: In this paper, a servo-hydraulic testing machine has been developed to determine accurately the cyclic stress-strain behavior of materials subjected to combined high-strain fatigue and creep at temperatures up to 700°C.
Abstract: A description is given of apparatus which has been developed to determine accurately the cyclic stress-strain behaviour of materials subjected to combined high-strain fatigue and creep at temperatures up to 700°C. The servo-hydraulic testing machine has a load capacity of ±20 000 lbf in push-pull and can operate in either a strain-cycling or a load-cycling mode. The specimen has a diameter of 0.5 in and a parallel gauge length of 1.5 in terminating in conic-section ridges on which extensometers are mounted for the measurement and control of axial strain. Strain is held constant to better than ±1 × 10−5 during hold times of up to 12 h and temperature control is better than ±0.5 degC.
TL;DR: In this article, a range of sections has been tested including prismatic bars as well as an actual turbine blade, and the positions of shear-centre and centre-of-twist of some of the bars were found.
Abstract: In order to obtain accurate values of the natural frequencies of torsional vibration of long steam-turbine blades it is necessary to determine the torsional stiffnesses of the blade accurately. Various empirical formulae are at present available for the calculation of the torsion constant for sections such as those of a turbine blade; to determine which is the best, a range of sections has been tested including prismatic bars as well as an actual blade. One particular formula is suggested for use. Additionally the positions of shear-centre and centre-of-twist of some of the bars were found.
TL;DR: A creep laboratory for variable load and variable temperature testing in uniaxial tension has been established at the University of Newcastle upon Tyne as mentioned in this paper, where the philosophy behind the specification and design of the equipment is described, considerable attention having been paid to accurate control of the test environment.
Abstract: A creep laboratory for variable-load and variable-temperature testing in uniaxial tension has been established at the University of Newcastle upon Tyne. The philosophy behind the specification and design of the equipment is described, considerable attention having been paid to accurate control of the test environment. The method of processing experimental data, obtained with a data acquisition system, is outlined.