Strength hardening coefficient

With such method Borodii [48] calculated the values reported in Table 9.2 for several metals and alloys. In a more recent study Borodii and Shukaev [49] proposed an approximate relation for the non-proportional cyclic hardening coefficient. This relation is based on monotonic strength properties of the material and is expressed as... 

Although Equation 18.14 qualitatively took this dynamic equilibrium into account, Shoji and coworkers [106-108] reformulated the crack tip strain rate relationship to take into account these complex strain rate factors in front of an advancing crack fip and to include the expected contributions due to work-hardening coefficient, yield strength, degree of plastic consfrainf, and dynamic applied loads ... 

A hard, mst-resistant shaft of at least 0.25 micrometer finish is usually required. Common shaft surfaces are hardened tool steel, chrome plate, high strength bronze, and carbide and ceramic overlays. Test results over a broad speed range from 0.05 to 47 m/s (10 to 9200 fpm) iadicate that a coefficient of friction of 0.16—0.20 and a wear factor of 14 X 10 m /N(70x 10 ° in. min/ft-lb-h) are typical for dry operation of weU appHed grades of carbon—graphite (29). 

A plot of log o against log s should thus yield a straight line whose slope is n and which makes an intercept equal to log fej on the log o axis (at s = 1). Thus the constant kj represents the true stress at unit true strain and is termed the strength coefficient. The exponent n is known as the strain hardening exponent. 

The above equation is then represented by a straight line in a log-log plot, and the linear slope yields the strain hardening exponent while its ordinate gives the strength coefficient. The strain hardening exponent may exhibit values from n = 0 for perfectly plastic solids (e.g., waxes) to n = I for elastic solids (e.g., diamond). For most metals the strain hardening exponent usually ranges between 0.10 and 0.50. 

For practical calculations, the permeability of concrete is considered as equal to that of hardened paste. In that assumption, the existence of microcracks and aggregate grains in concrete compensate each other for water flow. For higher concrete strength and low wic ratio the coefficient and permeability itself decrease considerably. A further decrease may be expected for high and very high performance concretes with low values of wIc ratio and with extensive use of microfillers. 

Thermospan alloy is a trademark of Carpenter Technology Corp. It is a precipitation-hardenable superalloy having an excellent combination of tensile properties and stress-rupture strength in the recrystallized condition with the use of common solution and age-hardening treatments. The alloy also exhibits a low coefficient of expansion over a broad temperature range. 

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