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Effect of Material Properties on Design
Published in Mahmoud M. Farag, Materials and Process Selection for Engineering Design, 2020
Laminated or sandwich composites usually consist of a thin facing material and a low-density core. Sandwich materials combine high section modulus with low density; for example, an aluminum-faced, honeycomb sandwich structure beam is about one-fifth the weight of a solid aluminum beam of equivalent rigidity. The facing material in a sandwich structure carries the major applied load and therefore determines the stiffness, stability, and strength of the composite. Examples of possible facing materials are aluminum, stainless steel, magnesium, titanium, plastics, and fiber-reinforced materials. The core forms the bulk of a sandwich structure. Therefore, it is usually of lightweight but must also be strong enough to withstand normal shear and compressive loads. The core can be in the form of foam or cells. Foam cores are usually made from plastics, especially polystyrene, urethane, cellulose acetate, phenolic, epoxy, and silicone. Foamed inorganic materials like glass, ceramics, and concrete can also be used. Cellular cores can have corrugated or honeycomb metallic structures. Other core materials are glass-reinforced plastics (GRPs), ceramics, or paper. Plastic-cored sandwiches faced with steel or aluminum have been shown to be weight-saving, cost-effective substitutes for automotive sheet steel. Thermal and sonic insulation characteristics of these sandwiches provide secondary benefits, along with possibilities of using lower-capacity forming presses. However, sandwich materials suffer from lower in-plane strength, lower dent resistance, limited joining capability, and more difficulties in recycling.
Machining of Metals
Published in Sherif D. El Wakil, Processes and Design for Manufacturing, 2019
Each of these groups includes the following types of tools: Turning tools. Turning tools can be either finishing or rough turning tools. Rough turning tools have small nose radii and are employed when deep cuts are made. Finishing tools have larger nose radii and are used when shallower cuts are made in order to obtain the final required dimensions with good surface finish. Rough turning tools can be a right-hand or left-hand tool, depending upon the direction of feed. They can have straight, bent, or offset shanks. Figure 11.5 illustrates the different kinds of turning tools.Facing tools. Facing tools are employed in facing operations for machining flat-side or end surfaces. As can be seen in Figure 11.6, there are tools for machining both left- and right-side surfaces. These side surfaces are generated through the use of cross-feed, contrary to turning operations, where longitudinal feed is used.Cutoff tools. Cutoff tools, which are sometimes called parting tools, serve to separate the workpiece into parts and/or machine external annular grooves, as shown in Figure 11.7.Thread-cutting tools. Thread-cutting tools have triangular, square, or trapezoidal cutting edges, depending upon the cross section of the desired thread. Also, the plane angles of these tools must always be identical to those of the thread forms. Thread-cutting tools have straight shanks for external thread cutting and bent shanks for internal thread cutting. Figure 11.8 illustrates the different shapes of thread-cutting tools.Form tools. As shown in Figure 11.9, form tools have edges specially manufactured to take a form that is opposite to the desired shape of the machined workpiece.
Design and production of sustainable lightweight concrete precast sandwich panels for non-load bearing partition walls
Published in Cogent Engineering, 2021
Fayez Moutassem, Kadhim Alamara
Precast Concrete Sandwich Panel (PCSP) is a structural system consisting of a low-density core and high strength facing materials that act integrally as one unit to resist applied loads. These structures are strong, yet light in nature. The facing materials may be composed of concrete, steel, aluminum, carbon fiber material, calcium silicate, magnesia, or fiber cement, etc. (Benayoune et al., 2006; Jeom et al., 1999; Lee & Pessiki, 2006; Liew & Sohel, 2009; Rice et al., 2006). The core often consists of lightweight concrete, fiber reinforced composite, or foam (Jeom et al., 1999; Liew & Sohel, 2009; Scudamore & Cantwell, 2002; Stoll et al., 2004). These materials can be combined to form composite sandwich panels that can have many advantages. Wall sandwich panels may be used for cladding and bearing, non-bearing, or shear walls. A neoteric, growing interest has been observed in the use of precast sandwich panels for non-load bearing partition walls because of their high quality, lightweight, rapid installation, insulation and aesthetic properties. For the lightweight concrete core, the main aim is to select a sustainable material with low weight, excellent thermal insulation properties and high technical performances in term of hydrophobicity and low water absorption. Unlike conventional cement composites that are characterized by porosity and hydrophilicity, hydrophobic composites offer enhanced durability properties (Neto et al., 2016; Weisheit et al., 2016).