Steel specific properties

The properties of wood are generally inferior to those of metals. But the properties per unit weight are a different matter. Table 26.4 shows that the specific properties of wood are better than mild steel, and as good as many aluminium alloys (that is why, for years, aircraft were made of wood). And, of course, it is much cheaper. 

Plastics can also be combined with other materials such as aluminum, steel, and wood to provide specific properties. Examples include PVC/wood window frames and plastic/ aluminum-foil packaging material. All combinations require that certain aspects of compatibility such as processing temperature and linear coefficient of thermal expansion or contraction exist. 

Table 4.5 compares PE fibres with those of glass and steel. Engineering properties are intermediate between the two but if we take into account the very low density, the specific properties of PE fibres are by far the most attractive. 

An alternative method of enhancing the properties of steel is to alloy it with another metal, M this combines both interstitial and substitutional alloy structures, with C occupying holes in the Fe lattice, and M occupying lattice sites. Stainless steel is an example of an alloy steel and is discussed further in Box 5.2. For high-wear resistance (e.g. in rail and tram tracks), Mn is alloyed with steel. Other alloy steels contain Ti, V, Co or W, and each solute metal confers specific properties on the finished product. Specific steels are described in Sections 21.2 and 22.2. 

Alloying metals such as vanadium, chromium, titanium, manganese, and nickel are also added to give the steel the properties needed for a specific application. 

Austenitic stainless steels are generally considered non-magnetic, although the magnetic permeabiUty can increase due to cold drawing of the steel. This property can be useful for specific applications [6,7] it should also be taken into consideration when conventional magnetic covermeters are used, since they fail to detect the rebars. 

Polymer matrix composites (PMCs), or fiber-reinforced plastics (FRPs). provide a wide range of properties and behavior. Materials with discontinuous fibers are slightly stiffer than conventional unreinforced plastics, whereas the fully aligned continuous fiber systems can record exceptionally high specific properties (property divided by density), exeeeding those of competing materials such as steel and aluminum. There are a virtually infinite number of materials, and material formats that can be combined to form a composite material, as shown in Table 1. 

Nowadays, in place of asbestos, fibrous reinforcements are used that include glass fiber, steel fiber, aramid fiber, potassium titanate fiber, etc. Since these fibrous reinforcements have their own specific properties, in practice, a mixture of them is used. Potassium titanate fiber is a hard inorganic fiber. It can improve the strength, the heat resistance and the wear resistance of the fiietion material. In addition, it can enhance the friction coefficient of the friction material through its abrasive property. 

Figure 9.7 Specific properties (strength and modulus + specific gravity) of RPs, wood, aluminum, and steel...

As previously mentioned, most of ceramic membrane elements are produced under cylindrical shapes, that is, tube, multichannel, and monolith elements. Membrane modules are composed of one or more of these filtration elements, inserted in stainless steel housing (Figure 9.15). Plastic housings are also used, but stainless steel is often preferred to fully exploit specific properties of inorganic membranes, in particular, their ability to work in tough chemical and... 

An alloy is a combination of two metals. The combinations are the most useful metals to engineers because they have specific properties. For example, you have probably noticed that iron rusts. But if you add nickel to the iron (at least 10 percent), it becomes stainless steel, which does not rust. Iron is... 

The main reason for the recent popularity of nanotechnology is that the reduction of the dimensions of a material to nanosize leads to new specific properties [82]. Carbon nanofibers have very high tensile strength and Yormg s modulus (can reach values of about 12,000 MPa and 600 GPa respectively) which are approximately 10 times that of steel. Besides mechanical strength, CNFs are attractive in electrical applications as well due to their high electrical conductivity. These CNF properties provide a huge number of opportunities for future applications in all spheres of life [95]. 

The superior specific energy absorption of composites makes them attractive for crashworthiness (Vaidya, 2011). CFRP crush cones and similar structures can absorb 250 kJ/kg with a thermoplastic resin compared to 120 kJ/kg with a thermoset resin like epoxy, or versus 20 kJ/kg for steel. Crush properties can also be optimized by mixing carbon with other fibres as mentioned in Herrman et al. (2002). 

Different types of stents are common examples of body implants. A stent is a woven, knitted or braided cylindrical mesh structure made of stainless steel, nitrol or chrome-cobalt alloy that is inserted in a diseased or contracted artery or vein to restore a free blood flow by keeping the vessel open. The stent can be coated with substances to obtain specific properties or for continuous release (a drug-eluting stent) to inhibit cellular growth that may lead to repeated occlusion. 

Here an electroplated material is applied to a base body such as steel. The part can then be used directly, or it can also be further processed to achieve specific properties. Such electroplated replications can also be manufactured from plastic parts that are metallically coated. 

---