1. 2 Materials in design 3 procedure-one with steps that can be taught quickly, that is robust in the decisions it reaches, that allows of computer implementation, and with the ability to interface with the other established tools of engineering design. The question has to be addressed at a number of levels, corresponding to the stage the design has reached. At the beginning the design is fluid and the options are wide; all materials must be considered. As the design becomes more focused and takes shape, the selection criteria sharpen and the short-list of materials that can satisfy them narrows. Then more accurate data are required (though for a lesser number of materials)and a different way of analyzing the hoice must be used In the final stages of design, precise data are needed, but for still fewer materials-perhaps only one. The procedure must recognize the initial richness of choice, and at the same time provide the precision and detail on which final design calcula ations can The choice of material cannot be made independently of the choice of process by which the material is to be formed, joined, finished, and otherwise treated. Cost enters, both in the choice of material and in the way the material is processed. So, too, does the influence material usage on the environment in which we live. And it must be recognized that good engineering design alone is not enough to sell products. In almost everything from home appliances through automobiles to aircraft, the form, texture, feel, color, decoration of the product-the satisfaction it gives the person who owns or uses it-are important. This aspect, known confusingly as"industrial design", is one that, if neglected, can lose the manufacturer his market. Good designs work; excellent designs also give pleasure Design problems, almost always, are open-ended. They do not have a unique or"correct"solution, though some solutions will clearly be better than others They differ from the analytical problems used in teaching mechanics structures, or thermodynamics, which generally do have single, correct answers. So the first tool a designer needs is an open mind: the willingness onsider all possibilities. But a net cast widely draws in many fish. A procedure is necessary for selecting the excellent from the merely good. This book deals with the materials aspects of the design process. It develops a methodology that, properly applied, gives guidance through the forest of complex choices the designer faces. The ideas of material and process attributes are introduced. They are mapped on material and process selection charts that show the lay of the land, so to speak, and simplify the initial survey for potential candidate-materials. Real life always involves conflicting objectives-minimizing mass while at the same time minimizing cost is an example-requiring the use of trade-off methods. The interaction between material and shape can be built into the method. Taken together, these suggest schemes for expanding the boundaries of material performance by creating hybrids -combinations of two or more materials, shapes and configurat with unique property profiles. None of this can be implemented without data for material properties and process attributes: ways to find them are described The role of aesthetics in engineering design is discussed. The forces drivingprocedure — one with steps that can be taught quickly, that is robust in the decisions it reaches, that allows of computer implementation, and with the ability to interface with the other established tools of engineering design. The question has to be addressed at a number of levels, corresponding to the stage the design has reached. At the beginning the design is fluid and the options are wide; all materials must be considered. As the design becomes more focused and takes shape, the selection criteria sharpen and the short-list of materials that can satisfy them narrows. Then more accurate data are required (though for a lesser number of materials) and a different way of analyzing the choice must be used. In the final stages of design, precise data are needed, but for still fewer materials — perhaps only one. The procedure must recognize the initial richness of choice, and at the same time provide the precision and detail on which final design calculations can be based. The choice of material cannot be made independently of the choice of process by which the material is to be formed, joined, finished, and otherwise treated. Cost enters, both in the choice of material and in the way the material is processed. So, too, does the influence material usage on the environment in which we live. And it must be recognized that good engineering design alone is not enough to sell products. In almost everything from home appliances through automobiles to aircraft, the form, texture, feel, color, decoration of the product — the satisfaction it gives the person who owns or uses it — are important. This aspect, known confusingly as ‘‘industrial design’’, is one that, if neglected, can lose the manufacturer his market. Good designs work; excellent designs also give pleasure. Design problems, almost always, are open-ended. They do not have a unique or ‘‘correct’’ solution, though some solutions will clearly be better than others. They differ from the analytical problems used in teaching mechanics, or structures, or thermodynamics, which generally do have single, correct answers. So the first tool a designer needs is an open mind: the willingness to consider all possibilities. But a net cast widely draws in many fish. A procedure is necessary for selecting the excellent from the merely good. This book deals with the materials aspects of the design process. It develops a methodology that, properly applied, gives guidance through the forest of complex choices the designer faces. The ideas of material and process attributes are introduced. They are mapped on material and process selection charts that show the lay of the land, so to speak, and simplify the initial survey for potential candidate-materials. Real life always involves conflicting objectives — minimizing mass while at the same time minimizing cost is an example — requiring the use of trade-off methods. The interaction between material and shape can be built into the method. Taken together, these suggest schemes for expanding the boundaries of material performance by creating hybrids — combinations of two or more materials, shapes and configurations with unique property profiles. None of this can be implemented without data for material properties and process attributes: ways to find them are described. The role of aesthetics in engineering design is discussed. The forces driving 1.2 Materials in design 3