No description available.

No description available.

This thesis is concerned with the determination of cutting parameters (cutting speed, feed rate and depth of cut) in turning operations within an industrial environment. The parameters are required for the purposes of tool selection, working with a variety of batches of different materials. Previous work of this nature, little of which has been transferred into industry, has concentrated primarily on deriving optimum cutting conditions, based on a variety of deterministic and non- deterministic approaches, with a general reliance on experimentally-derived input variables. However, this work is only suited to tool selection for a single material. Under industrial conditions tools will frequently need to be selected for more than one material, in tool/material combinations not recommended by tool makers. Consequently, the objective of the research described in this thesis was to employ existing cutting data technology and to use it as the basis for a cutting data system, suitable for multi-batch tool selection. Two companies collaborated in this work, by making available suitable personnel and the provision of shop floor facilities on their premises. The initial work concentrated on the development of an algorithmic model, based on established theory. This was then tested industrially, using the concept of shop floor approved data as a substitute for optimum cutting data. The model was found to work reasonably, but required further development to make it suitable for multi- batch tool selection. This development took three main forms: a) a reduction of input data, particularly in the number of experimentally-derived variables, b) the removal of the tool/material-specific constraints traditionally used in cutting data optimisation, c) a method of data correction based on adjustment of the mean and standard deviation of the data. Further industrial testing was carried out using the resulting system. It was demonstrated that it was possible for a relaxed system with reduced input variables and appropriate data correction to function within an industrial environment.

No description available.

This work proposes a method for estimating the development cost of a software system with modular structure taking into account the target level of reliability for that system. The required reliability of each individual module is set in order to meet the overall required reliability of the system. Consequently the individual cost estimates for each module and the overall cost of the software system are linked to the overall required reliability. Cost estimation is carried out during the early design phase, that is, well in advance of any detailed development. Where a satisfactory compromise between cost and reliability is feasible, this will enable a project manager to plan the allocation of resources to the implementation and testing phases so that the estimated total system cost does not exceed the project budget and the estimated system reliability matches the required target. The line of argument developed here is that the operational reliability of a software module can be linked to the effort spent during the testing phase. That is, a higher level of desired reliability will require more testing effort and will therefore cost more. A method is developed which enable us to estimate the cost of development based on an estimate of the number of faults to be found and fixed, in order to achieve the required reliability, using data obtained from the requirements specification and historical data. Using Markov analysis a method is proposed for allocating an appropriate reliability requirement to each module of a modular software system. A formula to calculate an estimate of the overall system reliability is established. Using this formula, a procedure to allocate the reliability requirement for each module is derived using a minimization process, which takes into account the stipulated overall required level of reliability. This procedure allow us to construct some scenarios for cost and the overall required reliability. The foremost application of the outcome of this work is to establish a basis for a trade-off model between cost and reliability during the design phase of the development of a modular software system. The proposed model is easy to understand and suitable for use by a project manager.

Topology optimisation techniques help designers to nd the best layout of structural members. When followed by shape and sizing optimisation, these techniques result in far greater savings than shape and sizing optimisation alone. During the last three decades extensive research has been carried out in the topology optimisation area. Consequently topology optimisation techniques have been considerably improved and successfully applied to a range of physical problems. These techniques are now regarded as invaluable tools in mechanical, aerostructural and structural design. In spite of great potential in geomechanical problems, however, the application of topology optimisation techniques in this eld has not been studied thoroughly. This thesis explores the state-of-the-art topology and shape optimisation methods in excavation design. The main problems of concern in this thesis are to nd the optimum shape of an underground opening and to optimise the reinforcement distribution around it. To tackle these problems, new formulations for some topology optimisation techniques are proposed in this thesis to match the requirements in excavation problems. Although linear elastic material models have limited applications in excavation design, these models are used in the rst part of this thesis to introduce the proposed optimisation technique and to verify it. Simultaneous shape and reinforcement optimisation is considered as well. Using the proposed optimisation techniques, it is shown that the computational effort needed for this mixed optimisation problem is almost the same as the effort required to solve each of shape or reinforcement optimisation problems alone. In the next part of this thesis, reinforcement optimisation of tunnels in massive rocks is addressed where the behaviour of the rock mass is in uenced by few major discontinuities. Although discontinuities exist in the majority of rock masses, due to its complexities, optimising the excavations in these types of rocks has not been considered by any other researcher before. A method for reinforcement optimisation of tunnels in such rock masses is proposed in this thesis and its capability is demonstrated by means of numerical examples. Lastly, shape optimisation of excavations in elasto-plastic soil is addressed. In this problem the excavation sequence is also taken into account. A stressbased parameter is dened to evaluate the efficiency of the soil elements assuming Mohr-Coulomb material model. Some examples are solved to illustrate and verify the application of the proposed technique. Being one of the rst theses on the topic, this work concentrates on the theoretical background and the possibility of applying topology optimisation techniques in excavation designs. It has been demonstrated that a properly tailored topology optimisation technique can be applied to nd both the optimum shape and the optimum reinforcement design of openings. Optimising the excavations in various types of grounds including elastic homogeneous rock masses, massive rocks, and elasto-plastic soil and rock media have been considered. Different objective functions, namely, mean compliance, oor heave, and tunnel convergence have been selected and successfully minimised using the proposed techniques. The results obtained in this thesis illustrate that the proposed topology optimisation techniques are very useful for improving excavation designs.

Flapping wing propulsion has the potential to revolutionise the field of Micro Aerial Vehicles (MAVs), but little is known about the effect of flapping motion on the performance of flapping wings. Prototype MAVs have achieved flight with passive flapping wings moving in a sinusoidal flapping motion, but the possible benefits of alternative flapping motions have not been studied in detail. This thesis presents the development of an Integrated Testing System (ITS), which allows the evaluation of flapping wing performance for different flapping motions. A detailed parametric study of the effect of flapping motion on wing performance is performed, and the optimal flapping motion for several passive flapping wings is determined by hardware-in-the-loop optimisation of two wing performance metrics. The developed ITS was able to automatically test a variety of passive flapping wings, and demonstrated precise control of the flapping motion and accurate and repeatable measurements of average lift force, mechanical power, and wing twist angle. The parametric study revealed that of the three flapping motions tested, the sinusoidal flapping motion generated the highest lift force, but a smoothed triangular motion was able to generate lift significantly more efficiently under load. The optimal flapping motion was successfully determined for three flapping wings, and was found to increase the loaded effciency of the wings by an average of 31% over a sinusoidal flapping motion. The determined optimal motion was almost identical for the three tested wings, and was found to strongly resemble the flapping motion of insects These findings demonstrate that significant improvements in the performance of passive flapping wings can be achieved by relatively minor variations of the flapping motion. This increased understanding will ideally lead to more efficient flapping wing MAVs with higher payloads, longer flight times, and improved performance.

Thèse 3 cycle--Sc. phys.--Paris-Sud, 1973. / Bibliogr. p. 74-75.

Th. doct.--Math.--Lyon 1, 1992. / Bibliogr. p. 181-184.

<p> </p><p>The aim of this project has been to develop a new method that can be used for optimising the sequences of operations in flexible manufacturing cells. The method combines existing methods and available software tools from three research areas, optimisation, flexibility and virtual manufacturing. This method is named SIMBOSeer and it combines genetic algorithms in discrete event simulation together with continuous robot simulation. SIMBOSeer has been implemented at an existing workcell at Volvo Powertrain, Skövde, and it has successfully shown to be able to find possible improvements of the sequences of operations. SIMBOSeer has shown to be a successful combination of different virtual manufacturing tools. It has a great ability to find an optimal solution of the sequence of operations in a flexible manufacturing cell. SIMBOSeer not only gives a fast answer on how to produce different variants it also offers the possibility to generate the robot code automatically.</p>