Tensile strength selected metals

The squeezing apparatus described here is the one in use at the British Geological Survey (BGS) and utilizes a hydraulic pump (Wykeham Farrance Engineering Ltd., Slough) which has a maximum output stress of 70 MPa and hydraulic hoses and fittings (Fig. 10.9). The main body of the cell and other metal parts in contact with the test sample or pore water are manufactured from Type 316 stainless steel, selected for its resistance to corrosion and its high tensile strength. 

Materials selection process can be depicted in terms of Figure 1.40. Materials selection involves many factors that have to be optimized for a particular application. The foremost consideration is the cost of the material and its applicability in the environmental conditions so that integrity can be maintained during the lifetime of the equipment. When the material of construction is metallic in nature, the chemical composition and the mechanical properties of the metal are significant. Some of the important mechanical properties are hardness, creep, fatigue, stiffness, compression, shear, impact, tensile strength and wear. 

Materials Compatibility Einally, any lubricant is required to be compatible with non-metallic components used in the engine, such as plastics, resins and elastomers. In particular, polymeric materials used in seals and plastics need to retain their integrity when in contact with the lubricant. ACEA and most OEMs have material compatibility tests to ensure that the lubricant will not cause undue degradation in key physical parameters of the polymer. These parameters include tensile strength, hardness, volume and crack formation. Any such loss of polymer integrity could be manifest as oil seal leaks or in more extreme cases as a blown gasket. Current engine test examples for American, European and selected OEM specifications are shown in Table 9.5. 

Shear knives are manufactured from a variety of tool steels. The tensile strength and thickness of the metal being sheared determines the type of tool steel selected. Grade Selection is a function of balancing the variables of wear resistance, toughness, thermal properties, and cost. 

Fig. 8.10. Bar graph showing writer s selection of best values for the room temperature yield and tensile strengths of the rare earth metals.

Compared to metals and many other engineering materials, plastics have lower tensile strength, lower elastic modulus, and a higher coefficient of thermal expansion. These differences strongly influence the way joints are designed and adhesives are selected. In the paragraphs that follow the significance of these differences will be briefly analyzed. 

FIGURE 13.3 Tensile strength of Pd-Ag alloys versus silver content. (Reprinted with permission from ASM International, ASM Handbook, Metals Handbook Volume 2, Properties and Selection Nonferrous Alloys and Special-Purpose Materials, Materials Park, OH, 2000. www.asminternational.org. All rights reserved.)... 

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