Aluminium Design and Construction John Dwight

Figure 6.6 Categories of welded joint for estimation of HAZ extent: (1) long straight joints;
(2) attachment weld.
the area of softening is relatively much greater and a more realistic
estimate may be needed. Category 2 joints often extend over a large
part of a member’s width, causing a major proportion of the crosssection
to become softened (or all of it).
The well-known method for estimating the extent of the HAZ is the
one-inch rule [18]. Though crude, it is an invaluable design tool. We
believe that a sensible strategy is to employ the one-inch rule for all
preliminary calculations, with the option of switching to a more scientific
method for the final check. In many cases it will be found that the effect
of the HAZ on the resistance of the section is small, making the use of
the one-inch rule quite acceptable. But in other cases, where preliminary
calculations show that HAZ softening reduces the resistance significantly,
worthwhile economies can be made by the use of a more refined treatment
for the final design. In Sections 6.5.4–6.5.11, we present such a treatment,
based on the work of Robertson at Cambridge during the 1980s [21],
which leant heavily on the classic heat-flow equations of Rosenthal
(Figure 6.7). We call this the ‘RD method’ [22].
Figure 6.7 Heat-flow cases analysed by Rosenthal (moving heat source).
Copyright 1999 by Taylor & Francis Group. All Rights Reserved.