Browsing by Author "Cookson, R. A."

Now showing 1 - 6 of 6
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    An advanced finite element system for static and dynamic analysis-with application to the design of radial impellers
    (Cranfield University, 1987-07) Al-Azzawi, Mohammad Mousa; Cookson, R. A.; El-Zafrany, A.
    An advanced finite-element package, tailored to the static and dynamic analysis of radial impellers has been produced. Two families of new elements, one for thin and thick plates and the other for thin and thick shells, have been derived and proved to perform very well within a wide range of structural thicknesses. Static and dynamic economical solvers, two- and three-dimensional mesh generation and plotting, sectorial symmetric analysis, steady state response, transient response, and other programs are part of the large number of facilities available in the package. The finite-element package has been validated by solving a large number of simple case studies and comparing the package results with those obtained from analytical solutions. Two different radial impeller, experimental validation tests have been carried out, the first being the dynamic analysis of a radial impeller using the time averaged holographic technique, and the second the measurement of the steady-state stresses by means of a strain-gauge/slip ring assembly for a rotating impeller. The experimental results have been shown to be in good agreement with those obtained from the package.
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    Design of an interactive finite element computer package for the analysis of the ride of a generalised off-road vehicle
    (1987-02) Kamar, Elsayed Abdrabboh; Cookson, R. A.; El-Zafrany, A.
    A versatile computer package, to evaluate ground vehicle ride comfort has been designed. Wheeled, tracked, and semitracked vehicles have been modelled. The emphasis has been placed upon the tracked vehicle suspension systems with the neatly ”standard" torsion bar arrangement operating with either telescopic or rotary-vane dampers. Substantial investigation of the four-bar linkage, associated with the rotary-vane damper, has been carried out and is presented here.The package includes linear ,nonlinear ,[2-V) ,and I3-Vj vehicle models. A new technique employing the finite element method (FEM) fat suspension system modelling has been developed. Several methods of numerical integration are available in the package .A new evident scheme based on a hypetosculatory Hermitian weighted residual of the second order for the solution of the system of differential equations which simulate the vehicle has been derived. Whenever necessary the error developed during the integration process was limited. The graphic display facility of digital computers has been used extensively in the present code. As an example, the damped eigen-value problem has been solved graphically. The graphical solution is simple, direct, and tellable compared to the analytical solution. The terrain configuration might be of either harmonic or atbitrary shape function. Two tolerence critetia have been employed fat tide comfort evaluation ,namely, the absorbed power critetion and the international standard organization ISO 2631 critetion.The two critetia are fully integrated into the package and operate automatically. All individual subroutines have been tested successfully for the purpose intended. Complete sectors have been validated by running various case studies. The results obtained from the package agree reasonably well with the analytical or experimental results. The package allows updating in response to new vehicle and vehicle-terrain technology and can be run on both time-skating or batch processing computer machines. The main package structute is independent of computer type.
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    Finite element analysis of centrifugal impellers
    (Cranfield University, 1981-10) Sham Sunder, K.; Cookson, R. A.
    A three-dimensional method of stress analysis using finite element techniques is presented for determining the stress distribution in centrifugal impellers. It can treat all of the three types of loading possible in an inpeller, viz centrifugal, thermal and fluid. The method has no known limitations with regards to the geometric factors such as asymnetry of disk, blade curvature, presence of a cover disk or shroud, single or double sided impeller etc. A comparison of results with available experimental photoelastic results is presented with good agreement. The problem of the inter-blade bending effect, on the stress characteristics of an impeller, with relevance to the number of blades is studied in some depth. An insight into the effect of blade curvature on the stress characteristics of an impeller is also achieved. As an extension of the above work, a method is proposed for the analysis of the dynamic, behaviour of impe1lers, achieving a reasonable degree of success, particularly considering the limited period of time that was available for such an exercise.
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    Static and dynamic finite element analysis of pneumatic tyres including anisotropic and nonlinear effects
    (Cranfield University, 1987-04) Gaheen, Mohammed El-Nabawey A.; Cookson, R. A.; El-Zafrany, A.
    This thesis introduces a versatile finite element package, which is tailored for the static and dynamic analysis of radial tyres. A new axisymmetric solid-of-revolution element which takes into consideration, large deformation, the influence of composite orthotropic material and the viscoelasticity and the nonlinearity of the material properties, has been developed for a general loaded tyre. The finite element package has been verified by comparing its results with available analytical, numerical and experimental results. A full static and dynamic investigation has been carried out for a commercial tyre 175 HR 14 and results obtained by using the package have been compared with available experimental results developed by DUNLOP or carried out at Cranfieid. The package has proved to be reliable, flexible, efficient, economic and accurate. The numerical instability problems which are prevalent in this type of analysis have been overcome by the derivation of a developed Newton-Raphson iterative scheme.
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    Static and dynamic finite element stress analysis of layered composite plates and shells
    (Cranfield University, 1989-09) Mahmood, Rashid; El-Zafrany, A.; Cookson, R. A.
    In this work an attempt has been made to develop theories for finite element static and dynamic stress analysis tailored for use with composite layered plates and shells in this way it was hoped to provide accurate values of the stresses particularly transverse shear stresses through the thickness, and to perform accurate natural frequency analysis by including non-linear effects such as centrifugal stiffening. Initial derivations were based upon first order facet shell element analysis and first order curved shell element analysis. Subsequently, derivations were produced for higher order element analysis. A programming package has been developed based upon the above derivations, and containing a banded solver as well as a frontal solver, capable of analysing structures build up from uniform or variable thickness layers and with a multiple number of layers having constant or variable dimension. Results obtained with the aid of the present package have been compared with results derived from experimental work as well as with results derived from available analytical solutions. Investigations have been carried out for existing compressor blades, made of isotropic material and layered composite material, respectively. The results obtained from the package have been compared with available experimental results produced by RR or carried out at Cranfield. It has been shown that the above mentioned derivations produce comparable results and the package has proved to be reliable and accurate.
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    Studies into the Failure Prediction of Brittle Materials
    (Cranfield University, 1987-11) Nguyen, P. D.; Cookson, R. A.
    This thesis is divided into six chapters. The first chapter provides a brief introduction concerning the behaviour of brittle materials. It also contains the justification for the undertaking of the study as well as a brief description of the method of approach adopted, and thesis layout. Chapter two provides a critical review of the current literature available at present in the failure prediction brittle materials. Both theoretical and experimental studies are discussed and the relevance to the present work is justified. Chapter three deals with the numerical analyses adopted within the thesis. Five different failure criteria were utilized in the initial analysis of the results presented. Among them, the empirical model using the Principle of Independent Action satisfactorily represents the biaxial fracture behaviour of brittle materials in both tension-tension and tension-compression quadrants. Its validity has never been tested before. Various statistical fracture models were used to analyze the failure of brittle materials under multiaxial states of stress, the experimental failure data for simple tension being a starting point for their calculation. It was shown that the Energy Density theory led to a better agreement with the experiments than any other well-known fracture criterion. The study investigates methods of evaluating the Weibull parameters which were crucial in the failure prediction of brittle materials. Monte Carlo simulation techniques are also presented as a method of evaluating the data ranking for the failure probability of brittle materials. Chapter four is devoted to the description of experimental techniques adopted in the study, using specially designed rigs. Six different tests were conducted to evaluate the performance of brittle materials in static loading and also to enable comparisons with the theoretical predictions. Attention was given to specimen casting, loading frames, alignment, measurement techniques and other relevant parameters. The use of the linear elastic fracture mechanics method to predict the behaviour of cracks in bodies, which are subjected to steady stresses, is discussed. The compliance function for the three-point notch bend specimen is presented in addition to the determination of the fracture toughness of Herculite LX plaster. The work was also supplemented by the use of scanning electron microscopy (SEM) to failure analysis of plaster material. This is an extremely important tool in the study of brittle materials since the dimensions of small defects and fracture features on individual grains are often pertinent information to the failure analysis. Chapter five details the analysis of the theoretical results as well as the experimental findings. Based upon the previously mentioned approaches, a comparison was made between theoretically predicted and experimentally observed data. The comparison indicates that discrepancies exist between the observed and predicted results, the reasons for the discrepancies have been justified in this work. Chapter six provides a brief summary of conclusions derived from the complete study, together with recommendations for future work.