Stress analysis and strength evaluation of bonded shrink fitted joints subjected to torsional loads

This paper deals with the stress analysis and strength evaluation of bonded shrink fitted joints subjected to torsion. The stress distributions in the adhesive layer of bonded shrink fitted joints are analyzed by the axisymmetric theory of elasticity when an external torsion is applied to the upper end of the shaft. The effects of the outer diameter and the stiffness of rings on the interface stress distributions are clarified by numerical calculations. Using the interface stress distributions, the joint strength is predicted. In addition, the joint strength was measured experimentally. It is seen that rupture of the adhesive layer is initiated from the upper edge of the interface when torsion is applied to the upper end of the shaft. The numerical results are in fairly good agreement with the experimental results. It was found that the joint strength of bonded shrink fitted joints is greater than that of shrink fitted joints.     

A novel mathematical procedure to evaluate the effects of surface topography on the interfacial state of stress. Part I: Verification of the method for flat surfaces

A mathematical procedure is developed to utilize the complementary energy method, by minimization, in order to obtain an approximate analytical solution to the 3D stress distributions in bonded interfaces of dissimilar materials. The stress solutions obtained predict the stress jumps at the interfaces, which cannot be captured by current FEA methods. As a novel method, the penalty function is used to enforce the displacement boundary conditions at the interfaces. Furthermore, the mathematical procedure developed enables the integration of different interfacial topographies into the solution procedure. In order to incorporate the effects of surface topography, the interface is expressed as a general surface in Cartesian coordinates, i.e. F (x, y, z) = 0. In this paper, the flat interface problem, i.e. y = 0 surface is considered for verification of the method by comparison with the FEA method. A comparison of the results reveals our new mathematical procedure to be a promising and efficient method for optimizing interface topographies.     

Development and Background of Shells Theories-A Review Study

Thin shells are one of the structural elements that have versatile contributions in different engineering sectors,specifically in architectural,civil,mechanical,aeronautical,and marine engineering industries.Liquid-retaining structures,wide-span roofs,water tanks,arch dooms,and shells used in building nuclear power plants are recognized application examples of shell structures in architectural and civil engineering.This variety in using shells in different engineering sectors is due to the productivity of load-carrying behavior,excellent reservation in strength and structural integrity,shell structures are preferable in comparison to structural systems having the same span and dimensions;high stiffness,and covering a large areas.Besides the above distinguishing mechanical pros,it is widely accepted that structures and building containing shells are usually preferred by architectures and designers for aesthetic purposes.The analysis of shells has gone through many stages until the arrival of modern theories.In this study the different theories of shells were discussed,the background and development of shell theories were illustrated in this investigation.     

Studying elastic deformation behaviour of cast irons by acoustic emission

Abstract

The deformation of metallic materials includes both an elastic and a plastic deformation. In the case of cast irons, the elastic region becomes less pronounced as the graphite changes from spheroidal to flake shaped, as observed in nodular and grey cast iron, respectively. The present study aims to correlate the shape of the graphite phase with the deformation behaviour, where the plastic deformation and other strain accommodating events are quantified by measurements of the acoustic emission events occurring in the interior of the material at loading. It also aims to explain how the appearance of cast iron stress–strain curves depends on the graphite morphology where, for instance, spheroidal graphite cast irons exhibit a seemingly linear elastic behaviour in contrast to flake graphite cast irons. The present study includes a series of pearlitic cast iron material grades with differences in nodularity and carbon equivalent, respectively. It is shown that as the roundness of the graphite phase increases, the ability to absorb energy increases. The measured acoustic emission indicates that plastic deformation occurs in the seemingly linear elastic region regardless of the cast iron grade, i.e. no cast iron grade exhibits perfect linear elasticity. The plastic deformation rate in the elastic region increases as the roundness of the graphite decreases and as the carbon equivalent increases. It is shown that the plastic deformation governs the resulting modulus of elasticity in all kind of cast irons, i.e. the modulus of elasticity decreases as the yielding of the material increases. The present study improves the understanding of the deformation behaviour in the elastic region of different cast irons. The survey shows that acoustic emission testing is a useful method when studying the deformation behaviour of cast irons.     

Modelling the effect of graphite morphology on the modulus of elasticity in cast irons

Abstract

Nine grades of pearlitic cast iron containing different graphite morphologies (from flake, compacted and spheroidal) have been studied. The parameters investigated include the graphite aspect ratio, nodularity, graphite size and modulus of elasticity. These parameters have been correlated and compared with different existing bound and model equations. It has been found that the modulus of elasticity of the graphite phase increases as the aspect ratio and nodularity of the graphite increases, i.e.flake graphite gives a lower modulus of elasticity than spheroidal graphite. The experimental values of the modulus of elasticity show good agreement to bound and model equations, although flake graphite cast irons show higher deviation from the modelled values. An equation for the correlation between the graphite modulus of elasticity and the nodularity is presented. Introducing this linear correlation into an existing model for the determination of the effective modulus of elasticity gives a continuous function, including all grades of cast irons, with a very good agreement with experimental values. The modulus of elasticity of cast irons can be accurately predicted from both bound and especially model equations, using the aspect ratio and nodularity of the contained graphite particles. The fit is improved by using a modulus of elasticity of the graphite phase that is based on the graphite morphology, considering that the modulus of elasticity of the graphite is different in the basal and prismatic planes.     

27—THE BENDING AND CREASING OF MULTICOMPONENT VISCOELASTIC FIBRE ASSEMBLIES. PART I: GENERAL CONSIDERATION OF THE PROBLEM

The problems involved in making a mechanical analysis of bending deformations in textile fabrics are discussed. It is suggested that progress can be made by making simplifying assumptions concerning the geometry of fabric structure and deformation and using energy considerations to calculate forces and moments. Certain simple examples are given of the usefulness of this approach. A foundation is laid for the construction of a computer model that will, it is hoped, simulate the viscoelastic bending and creasing behaviour of textile fabrics from a knowledge of the bending and torsional viscoelastic properties of the constituent fibre(s) and their relative geometrical arrangement.     

Tensile properties of multilayered biaxial weft knitted fabric reinforced composite material

Abstract

The multilayered biaxial weft knitted (MBWK) fabric made of E-glass fibres and stitched with polyester yarns, which is a kind of non-crimp fabrics, has been impregnated with epoxy via resin film infusion technique to manufacture the composite plates. The tensile properties of the MBWK fabric reinforced composite are studied with the multidirectional tensile testing. The classical lamination theory is applied to evaluate both the tensile modulus and Poisson's ratio, which shows good agreements with the experimental results. Failure analyses are also available by means of sample debris examination to identify the failure modes and the scanning electron microscope to reveal the microscopic mechanism. Predictions of the tensile properties provide a way to estimate the mechanical behaviours of the MBWK composite structures. Elongation at break is independent of the testing directions, which can be used as the failure criterion of the composite.     

A two-dimensional stress analysis of single-lap adhesive joints of dissimilar adherends subjected to tensile loads

Single-lap adhesive joints of dissimilar adherends subjected to tensile loads are analyzed as a three-body contact problem using the two-dimensional theory of elasticity. In the numerical calculations, the effects of Young's modulus ratio between different adherends, the ratio of the adherend thicknesses, the ratio of the adherend lengths, and the adhesive thickness on the contact stress distributions at the interfaces are examined. As a result, it is found that (1) the stress singularity occurs near the edges of the interfaces and it increases at the edge of the interface of an adherend with smaller Young's modulus; (2) the stress singularity increases at the edge of the interface of an adherend with thinner thickness; (3) the singular stresses increase at the edges of the two interfaces as the ratio of the upper adherend length to the lower one decreases; and (4) the singular stresses increase at the edges of the two interfaces as the adhesive thickness decreases when the adhesive is thin enough, and they also increase as the adhesive thickness increases when the adhesive is thick enough. In addition, the singular stresses obtained from the present analysis are compared with those obtained by Bogy. Fairly good agreement is seen between the present analysis and the results from Bogy. Strain measurement and finite element analysis (FEA) were carried out. The analytical results are in fairly good agreement with the measured and the FEA results.     

Elasticity Determination of Adhesive Patches With Filler Inclusion

Patches can be used for topical and transdermal drug delivery as well as for cosmetic purposes. Their mechanical properties (i.e. strength, brittleness, elasticity, etc.) are important features that can influence their therapeutic success. Most of the drug-in-adhesive (DIA) patches adhere well to the skin or other surfaces. However, their degree of elasticity cannot be accurately determined since during the compression–decompression cycle(s), the patches adhere to the moving plate (and sensor), resulting in under the x-axis forces (and “negative” areas in the stress–strain curves). We overcame this limitation using two different approaches: gluing thin non-adhesive plates to both sides of the patch or applying talc granules to both surfaces. These treatments rendered the patch surfaces non-adhesive, thereby eliminating the “negative” force (and area) and permitting testing of adhesive materials as well as determination of their degree of elasticity. The general level of calculated recoverable work was ～60–80% of the total work for the patches, i.e., they can be considered elastic entities. When the strain rate was 100 mm/s, the calculated recoverable work “jumped” to ～92% and changed in a significant manner. Inclusion of fillers (corn or potato starch) in the patch reduced the percent recoverable work and degree of elasticity. For the first compression–decompression cycle, there was an increase in the degree of elasticity of the compressed–decompressed patches; while in the third and fourth cycles, there were no statistical differences in the extents of percent recoverable work. Recoverable work vs cycle number was almost a mirror image of total work.     

31—OBSERVATIONS ON THE MECHANICAL BEHAVIOUR OF LINCOLN-WOOL FIBRES SUPERCONTRACTED IN LITHIUM BROMIDE SOLUTION

A brief summary of certain phenomena associated with the two stages of supercontraction in aqueous lithium bromide solution is given; in particular, the mechanical properties, in the cold solution, of wool fibres at the end of each stage are discussed. Results previously obtained by Feughelman and Haly are reinterpreted in terms of the simple two-phase model of crystalline microfibril embedded in a less ordered matrix. On the basis of certain assumptions, it is possible to obtain an estimate of the Stress–Strain curve of the matrix in LiBr solution. The matrix Stress–Strain curve so obtained compares well with the theoretical inverse Langevin rubber-elasticity curve up to a certain strain level.

A value for the number of random links between cross-links is obtained.