two pieces being joined and the temperature is

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Unformatted text preview: her the bond-energy curve (the point where the energy C is a minimum) or the bond-force curve (the point where 3-D is zero). 2-D (planar) structure, the total forcestructure, with all angles = 109.5° with all angles = 120° Bragg’s law (a) defining equation of (b) The X-ray FIGURE 2.6–4 A schematic illustration of covalent bond.angles in two compounds: (a) the bond angle in a tetrahe2d sin diffraction, n dral structure such as diamond is 109.5 ; (b) when the C is bonded to only three other atoms (one of which involves a double bond), the resulting structure is planar with a bond angle of two materials in which a brazing A process of joining 120 . low-temperature filler metal is sandwiched between the ....................................................................................................................................... two pieces being joined and the temperature is raised EXAMPLE 2.6–4 sufficiently to melt the filler metal but H2 O high enough to Sketch the three-dimensional arrangement of covalent bonds in the not molecule. melt the materials being joined. Solution The geometry of the HTerm used to envisioned by materials atom atare center of an brittle 2 O molecule can be describe placing the O that the unable imaginary cube and noting that its four pairs of electrons, two bonding and two nonbonding electron to absorb energy by “bending” but instead fracture pairs, must be spatially separated as much as possible. This separation, shown in Figure 2.6–5, is obtained(break into pieces) along directions pointing to an alternating set of four corners by placing the electron pairs when subjected to external loads. For of the imaginary cube. The H atoms are positioned at two of the cube corners associated with the example, the glass in a car window is brittle, while the metal or plastic bumper is not. More precisely, brittle materials exhibit a low failure strain. Textbook Table of Contents | Burgers circuit A| circuit drawn around a dislocation | e-Text Main Menu through defect-free material that would normally close if there were no dislocation inside of the circuit. Burgers vector b The vector that joins...
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