IIP f2w
- Work to maximum load N mm/mm^3
CA
lbh- Total work N mm/mm^3
CA
lbhwhere P = load at the limit of proportionality, the point in load-deflection curve at
which the graph deviates from the straight line.
l, b and h = the length width and height of the test specimen respectively
P = maximum load
h = deflection at the limit of proportionality
C = area constant
A = area of load-deflection curve up to limit of proportionality
A = area up to maximum load
A = area up to the final reading when total work is required
E! v X The specimen may be 50 × 50 × 1000 mm or 20 × 20 × 400 mm. The
distance between points of application of the load and the supports (Fig. 4.11) is 150 mm for
50 × 50 mm and 60 mm for 20 × 20 mm cross-sections. The load is applied at a constant rate of
3 mm per minute and 1.5 mm per minute in the two cases, respectively.
p
2R
II 2
2v2 Deflection of neutral axis is measured at the mid span. The distance L between these two
points (also called as gauge length) is kept 400 mm and 160 mm for the two specimens
respectively. The deflection is measured at suitable load intervals such that 8-10 readings are
available up to limit of proportionality and continued up to maximum load. The failure of the
specimen is recorded according to its appearance and development as indicated in Fig. 4.10. A
graph is plotted with load as ordinate and deflection as abscissa and the limit of proportionality,
that is, the point at which the curve deviates from straight line is evaluated. The various
characteristics are determined by the following formulae:
S. No. Characteristic Unit Formula- Fibre stress at limit of proportionality N/mm^22
3 Pa
bh- Equivalent fibre stress at N/mm^22
3 Pa
bhmaximum load