Page 390 - T. Anderson-Fracture Mechanics - Fundamentals and Applns.-CRC (2005)

1656_C008.fm Page 370 Monday, May 23, 2005 5:59 PM

370 Fracture Mechanics: Fundamentals and Applications

FIGURE 8.12 Proposed method for removing time dependence from load-displacement curves. (a) first, a
set of tests are performed over a range of displacement rates (b) next, isochronous load-displacement curves
are inferred, and (c) finally, the displacement axis of each curve is multiplied by a function γ (t), resulting in
a single curve.

Suppose that the displacements at a given load are related by a separable function of time, such
that it is possible to relate all the displacements (at that particular load) to a reference displacement:

∆ R ∆ = γ () (8.32)
t

The isochronous load-displacement curves could then be collapsed onto a single trend by
multiplying each curve by γ (t), as Figure 8.12(c) illustrates. It would also be possible to define
a reference J:

t
J R J = γ () (8.33)
t
Note the similarity between Equation (8.23) and Equation (8.33).