The effect of scale factor on mechanical properties of lead alloys

Abstract

The effect of scale factor on mechanical and physical properties of metals and alloys is of both scientific and practical interest. Its study permits determination of the role in formation of physical properties of such factors as surface quality, character and distribution of internal and surface defects, types of processing, grain size, etc. As is well known, scale factor manifests itself to a greater degree, the stronger the material in question. Possibly because of this, data on the effect of scale factor on the properties of lead alloys with their relatively low mechanical strength are absent from the literature. However, such an omission is not justifiable, since lead, which is widely used in industry, is a scarce and expensive material, and proper determination of optimum dimensions for lead products is of major importance. The present study will clarify in greater detail the role of grain size and general level of mechanical properties on the relative effect of scale factor. The practical value of the study lies in the following. The alloys studied are used in manufacture of protective cable shields. The shield thickness can vary over wide limits, depending on the properties of the alloy, construction of the cable, and conditions of transportation and use. Therefore, by increasing the strength and other desirable properties of the alloy, significant reductions can be made in shield thickness, producing considerable economic savings. However, this cannot be done without a knowledge of the dependence of the alloy's mechanical properties on dimensions of the final product or specimen. Commencing from conditions of cable shield transportation and use, the effect of scale factor on alloy properties was studied for tensile loading, creep, and cyclical bending. The data gathered permit evaluating the validity of calculations for change in cable shield thickness for replacement of one alloy by another.