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.

This work examines the fundamental flow behaviour of granular materials under conditions relevant to blast furnace. Such a study may have some impact on the development of new technology to improve performance of blast furnace operation. The blast furnace operation involves rich granular dynamics phenomena which currently attract a strong interest from wide scientific and engineering community. In this work, percolation phenomenon is analyzed extensively. Percolation phenomenon is one of the most significant factors which cause particle segregation and mixing. In blast furnace when sinter and coke of different size and density are charged, percolation phenomenon occurs. In this work percolation properties like percolation velocity, residence time distribution and radial dispersion are checked for different material properties of percolating particles. It was found that percolation behaviour is related to many factors. Percolation properties of a single particle and also for batches of percolating particle were examined. The effect of external forces on percolation properties is also checked. DEM simulation method was found to be suitable for analysis of percolation flow behaviour of different types of particles. It was also found that the change of packed bed conditions has a great impact on particle percolation and segregation behaviour. In a packed bed, vibration and liquid of different properties were introduced. Particle dynamics in descending packed bed condition was checked. The effect of vibration and descending velocity was measured for percolation behaviour. Both vibration frequency and amplitude are important factors for particle flow in such a packed bed. Descending velocity of packed particles combined with vibration was found to have a pronounced impact on percolation behaviour. Liquid properties like viscosity and density affect particle dynamics significantly. Particle segregation in a pile was investigated as an extension of the percolation study. The effects of diameter ratio of binary feed, initial mixing ratio, feed rate in case of central feeding on conical pile were investigated. It was found that all of those parameters affect particle flow and segregation. Flowing layer over static pile was simulated and velocity profile and mixing ratio in different layers were observed. 3-D Screening Layer model was validated by DEM and experiment. In case of multipoint feed system, a conical pile which is similar to the deadman of a blast furnace was generated and the flowing layer characteristics over this static pile was also analysed.

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.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references (leaves 41-42). Online version available on the World Wide Web.