A majority of plastic items are produced by injection moulding process. Experiments are conducted to find out the residual stresses developed in mould due to cooling and voids created in the mould cavity due to improper filling of plastic (polymer), therefore producing a weak and objectionable component. There are numerous methods to find voids in the end product, one of them is measuring void rates using optical microscope. Another way of identifying the residual stress is by simulating specimen part in analysis software and studying flow pattern of heat from runner point to end part of component. Also, when the mould is set for cooling procedures, the simulation of cooling from its highest temperature to room temperature could be simulated in a computer to study the cooling pattern. The volume in part where cooling happens fastest relative to other surrounding parts may result in stresses, called residual stress. This phenomenon also leads to redundant results such as warpage, sink marks and weld lines which are extremely costly problems to fix once the mould is in production environment. / Plastic parts that require tight tolerance may warp out of tolerance even if made by the most experienced mould makers. New companies may not have the expertise to start making moulds correctly for even the simplest parts. A lot of capital is invested in moulds and in cost of making parts, and much of the money spent on making moulds goes into reworking them. In order to avoid the huge cost spent on reworks, the mould can be made right the first time. / This objective could be achieved, by the use of Finite Element Analysis (FEA), and advantage of software simulation to study the thermal flow patterns, from this shrinkage due to rapid cooling of plastic injected parts can be predicted. Use of ANSYS to model, mesh and analyse simple plastic components is the aim of this project. / Thesis (MEngineering)--University of South Australia, 2005.

This research focuses on improvements and application of 1D finite elements for nonlinear dynamic analysis of reinforced concrete frames under extreme loadings. The concept of force interpolation is adopted for the element formulation and a solution scheme developed based on a total secant stiffness approach that provides good convergence characteristics. The geometrical nonlinearities including 2nd order P-Delta effects as well as catenary action are considered in the element formulation. It is shown that geometrical nonlinearities may have a significant effect on member (structure) response within extreme loading scenarios. In the analysis of structures subjected to extreme loadings, accurately modelling of the post peak response is vital and, in this respect, the objectivity of the solution with softening must be maintained. The softening of concrete under compression is taken into account, and the objectivity preserved, by adopting a nonlocal damage model for the compressive concrete. The capability of nonlocal flexibility-based formulation for capturing the post-peak response of reinforced concrete beam-columns is demonstrated by numerical examples. The 1D frame element model is extended for the modelling of 3D framed structures using a simplified torque-twist model that is developed to take account of interaction between normal and tangential forces at the section level. This simplified model can capture the variation of element torsional stiffness due to presence of axial force, bending moment and shear and is efficient and is shown to provide a reasonable degree of accuracy for the analysis of 3D reinforced concrete frames. The formulations and solution algorithms developed are tested for static and dynamic analysis of reinforced concrete framed structures with examples on impact analysis of beams, dynamic analysis of frames and progressive collapse assessment of frames taken from the literature. The verification shows that the formulation is very efficient and is capable of modelling of large scale framed structures, under extreme loads, quickly and with accuracy.

A study of vibrations and sound radiation in upright and grand pianos has been made to determine whether the piano may be improved by altering the materials of the component parts which are traditionally fabricated in timber. Modal analysis and sound level measurements of an upright piano has shown that the radiation from the case is at least 20 dB lower than the radiation from the soundboard, and therefore the case is not a significant determinant of piano tone. A method was developed for separating piano sound and vibrations into broadband and tonal components and used to compare the performance of upright and grand pianos. Using this method it was found that the broadband vibration level was twice as high in the uprights as in the grands. A finite element model of an upright piano was developed and used to demonstrate that replacing the keybed with a higher impedance material than conventionally used would reduce the key vibration level, and hence bring the uprights closer in performance to grand pianos, and improve the 'feel' of the instrument for the player. The keybed of one of a pair of identical pianos was replaced with high density fibreboard, and subsequent objective measurements showed that the broadband component of key vibrations was reduced by 3.2 dB while the radiated sound was unchanged. A controlled subjective comparison between the modified and unmodified pianos undertaken by experienced players showed that a statistically significant number preferred the modified piano, and that the upright piano had been improved. / Acoustics Research Centre, Department of Mechanical Engineering, Foundation for Research Science and Technology, Fletcher Wood Panels.

A study of vibrations and sound radiation in upright and grand pianos has been made to determine whether the piano may be improved by altering the materials of the component parts which are traditionally fabricated in timber. Modal analysis and sound level measurements of an upright piano has shown that the radiation from the case is at least 20 dB lower than the radiation from the soundboard, and therefore the case is not a significant determinant of piano tone. A method was developed for separating piano sound and vibrations into broadband and tonal components and used to compare the performance of upright and grand pianos. Using this method it was found that the broadband vibration level was twice as high in the uprights as in the grands. A finite element model of an upright piano was developed and used to demonstrate that replacing the keybed with a higher impedance material than conventionally used would reduce the key vibration level, and hence bring the uprights closer in performance to grand pianos, and improve the 'feel' of the instrument for the player. The keybed of one of a pair of identical pianos was replaced with high density fibreboard, and subsequent objective measurements showed that the broadband component of key vibrations was reduced by 3.2 dB while the radiated sound was unchanged. A controlled subjective comparison between the modified and unmodified pianos undertaken by experienced players showed that a statistically significant number preferred the modified piano, and that the upright piano had been improved. / Acoustics Research Centre, Department of Mechanical Engineering, Foundation for Research Science and Technology, Fletcher Wood Panels.

A study of vibrations and sound radiation in upright and grand pianos has been made to determine whether the piano may be improved by altering the materials of the component parts which are traditionally fabricated in timber. Modal analysis and sound level measurements of an upright piano has shown that the radiation from the case is at least 20 dB lower than the radiation from the soundboard, and therefore the case is not a significant determinant of piano tone. A method was developed for separating piano sound and vibrations into broadband and tonal components and used to compare the performance of upright and grand pianos. Using this method it was found that the broadband vibration level was twice as high in the uprights as in the grands. A finite element model of an upright piano was developed and used to demonstrate that replacing the keybed with a higher impedance material than conventionally used would reduce the key vibration level, and hence bring the uprights closer in performance to grand pianos, and improve the 'feel' of the instrument for the player. The keybed of one of a pair of identical pianos was replaced with high density fibreboard, and subsequent objective measurements showed that the broadband component of key vibrations was reduced by 3.2 dB while the radiated sound was unchanged. A controlled subjective comparison between the modified and unmodified pianos undertaken by experienced players showed that a statistically significant number preferred the modified piano, and that the upright piano had been improved. / Acoustics Research Centre, Department of Mechanical Engineering, Foundation for Research Science and Technology, Fletcher Wood Panels.

The thesis presents a Finite Element Analysis (FEA) based wear modelling algorithm devised in the course of the reported research activity. FEA is used as a tool to calculate nodal pressures at the contact region for small sliding steps. These pressures are then inputted to a customised wear calculating routine. The routine uses averaged wear coefficients (wear rates) obtained from custom designed experiments. The FEA contact geometry is modified after each sliding step to account for the contact height decay, thus determining the volume loss due to wear over usage time, thus predicting the worn geometry. Consequently, the designer gains invaluable insight into the extent of wear-caused component deformation along with the number of usage cycles lapsed prior to such deformation.

A study of vibrations and sound radiation in upright and grand pianos has been made to determine whether the piano may be improved by altering the materials of the component parts which are traditionally fabricated in timber. Modal analysis and sound level measurements of an upright piano has shown that the radiation from the case is at least 20 dB lower than the radiation from the soundboard, and therefore the case is not a significant determinant of piano tone. A method was developed for separating piano sound and vibrations into broadband and tonal components and used to compare the performance of upright and grand pianos. Using this method it was found that the broadband vibration level was twice as high in the uprights as in the grands. A finite element model of an upright piano was developed and used to demonstrate that replacing the keybed with a higher impedance material than conventionally used would reduce the key vibration level, and hence bring the uprights closer in performance to grand pianos, and improve the 'feel' of the instrument for the player. The keybed of one of a pair of identical pianos was replaced with high density fibreboard, and subsequent objective measurements showed that the broadband component of key vibrations was reduced by 3.2 dB while the radiated sound was unchanged. A controlled subjective comparison between the modified and unmodified pianos undertaken by experienced players showed that a statistically significant number preferred the modified piano, and that the upright piano had been improved. / Acoustics Research Centre, Department of Mechanical Engineering, Foundation for Research Science and Technology, Fletcher Wood Panels.

Abstract Grinding introduces unavoidable residual stresses of significant but unknown magnitudes. The effect of residual stresses in surface integrity is related to the nature of the residual stresses which relies purely on the process parameters and the workmaterial properties. It is a well-known fact that the fatigue strength of a ground component is increased by introducing compressive stresses. On the other hand, fatigue cracks may originate at regions of maximum tensile stress and usually at the surface of the material. Moreover, stress corrosion cracking is another consequence of critical surface tensile stress. Added to that, the residual stresses may result in dimension alteration and surface distortion, particularly for thin products such as plates. The beneficial effects of compressive residual stresses have been widely recognized in industry. The wise application of such a principle would bring about improved economical use of parts subjected to fatigue loading and aggressive environmental conditions. Therefore a better understanding of residual stress mechanisms is necessary to increase the dimensional accuracy and improve the surface integrity of ground elements, particularly for parts with high precision and manufactured by automated production lines. Consequently, the development of reliable models for predicting residual stresses is of great value in reducing the amount of measurements and experimental tests of residual stresses. Unfortunately, little effort has been devoted so far to develop appropriate models to take into account grinding conditions, workmaterial properties and boundary conditions. This thesis aims to investigate the residual stress mechanisms induced by grinding in terms of grinding parameters. In order to obtain a full understanding, both the roles of individual factors causing residual stresses (i.e. mechanical, thermal and phase transformation) and their couplings were carefully studied with the aid of the finite element method. The studies include: (1) residual stresses due to thermal grinding conditions, (2) residual stresses due to iso-thermal mechanical grinding conditions, (3) coupling of thermo-mechanical conditions, (4) coupling of thermo-phase transformation, and (5) the full coupling of all the factors. It is found that under sole thermal grinding conditions, the heat flux associated with up-grinding may lead to a higher grinding temperature compared with that of down-grinding. A constant flux introduces the least temperature rise if the total grinding energy is the same. Higher convection heat transfer not only decreases the grinding temperature but also makes the temperature rise occur mainly within a thin surface layer. A similar effect can be achieved by applying higher table speeds. When the grinding temperature is less than the austensing temperature, surface residual stresses are tensile. The heat generated within the grinding zone causes a very non-uniform temperature field in the workpiece. The part of the workmaterial subjected to a higher temperature rise expands more significantly and causes compressive stresses because of the restraint from its surrounding material that expands less. When the surface heat flux moves forward, the material outside the grinding zone contracts under cooling. Since the workmaterial has been plastically deformed during thermal loading, the contraction is restrained and thus a tensile stress field is generated locally. If a workpiece material experiences a critical temperature variation in grinding, phase transformation takes place and a martensite layer appears in the immediate layer underneath the ground surface. It was found that the growth of martensite develops a hardened zone with a higher yield stress that expands with the movement of the heat flux. A tensile surface residual stress is then developed. When the volume growth of material takes place during phase change, compressive residual stresses may also be generated. Under iso-thermal grinding conditions, it was found that plane stress is mainly compressive regardless of the distribution of surface traction and the direction of the tangential grinding force. With up-grinding, the residual stress in the grinding direction is always tensile. However, down-grinding may yield compressive surface residual stresses if the magnitude of the ratio of horizontal to vertical grinding forces is sufficiently large. Moreover, it is noted that discrete surface traction, which is more reasonable in terms of simulating the individual cutting of abrasive grits, would bring about more complex residual stress distribution that is very sensitive to the combined effect of individual cutting grits. If thermal and mechanical grinding conditions are coupled, a state free from residual stresses may be achieved if grinding heat is low and either the convection heat transfer or the table speed is high. However, it is found that the full coupling of the mechanical deformation, the thermal deformation and deformation by phase change results in tensile residual stresses. The effects of cooling and mechanical traction in this case however are minor. In summary, the research of this thesis explored the following: (a) grinding temperature development in terms of a wide range of grinding parameters together with the effect of temperature-dependent material properties, (b) the origin and onset of irreversible deformation due to mechanical loading, thermal loading and phase change under critical grinding conditions, (c) the effects of individual residual stress mechanisms and their partial and full couplings, and (d) the selection of grinding conditions to achieve beneficial residual stresses. Finally, based on the new findings in this research, a more comprehensive methodology is suggested for further study.

Thesis (Ph. D.)--Ohio University, March, 1989. / Title from PDF t.p.

Akademisk avhandling--Chalmers tekniska högskola. / Extra t.p., with thesis statement, inserted. Bibliography: p. 125-132.