Effect of Vertical End-Milling Operations up on some Mechanical Properties of Free Machining Brass Plates.(Dept.M)

Abstract

Test sp ecimens made of as-received free machining brass plates having dimensions of (10x180x100) x 10-3m were vertical end milled from one or from two sides in some cases. Milling conditions varied from (0.1 to 1.2) x 10-3m depth of cut, and feed speed ranging between (0.4 to 1.58) x10-3 m/s for spindle speeds of (2.67 to 13.30) rev./s. Flat tensile test sp ecimens were made out of the same milled plates having 10x10-3m thickness and 50x10-3m gauge length. It was found, for cases of one side milling, that the increase of depth of cut from 0.1x10-3 m to 1.2x10-3m led to increases in the values of the maximum true tensilestrength from (600 to 650) MPa. On the other hand, the corresponding values. for double sides milling cases,varied from (620 to 670) MPa. The corresponding fracture strains ranged from 0.16 to 0.20 for cases ofmilling from one side to 0.125 to 0.175 for double sides milling cases. In all cases, slight decreases in the material true ultimate tensile stresses with noticeable increases in the fracture strains were noted upon the increase in spindle sp eeds. No change in the material strain-hardening exponents were noted through all the conducted tests. Material fatigue strength was taken to be equal to 0.3 of the true ultimate strength.