Innovative Stainless Steel Applications in transport ... - Euro Inox

t Sample Strength 304SP 1.4301 16-7Mn 1.4003
(mm) (N/mm 2 ) 2B 2H 2B 2H 2B 2H 2B
Rm 448 491 337 346 268
RSW Rm 163 161 157 158 185 144
WB Rm 178 213 252 275 219 243
ADB Rm 287 305 263 257 346 292
The adhesive bonding was performed using a commercially available adhesive. DP490
is a two-component epoxy adhesive, produced by 3M, whose properties and
applications are described in detail in the 3M publication “Solutions for Aerospace”
(3M 2008).
As can be seen in Table 29, the lap joint results are mainly given as tensile strength
calculated from base-material dimensions (thickness × width) only. Yield strengths
were only measured from the laser-welded lap joint specimens. The use of base-material
cross-section is, in practice, the only way to achieve even a rough comparison between
all the the various joining methods that are feasible for thin-sheet joining in lap
configuration. The resistance spot weld results suffer most from this type of
comparison: there is only one spot of typically 6 mm and 8 mm in diameter in 1.5 mm
and 3.0 mm sheet thickness, respectively. Hence, the load-carrying area is considerably
smaller than with other methods. On the other hand, this is also a feature of RSW, and
the specimen width was usually selected to represent a typical distance between two
spots.
In all cases, regardless of thickness, laser welding clearly shows the highest tensilestrength
values and resistance spot welding the lowest. Comparing the LBW lap joint
results to butt joint results in Table 29, it can be clearly seen that they are lower, the
difference being considerable. This fact emphasises the role of joint configuration in
defining the strength of the structure. Direct comparisons should therefore only be made
between similar configurations. Taking this approach, it is interesting to note the effect
of adhesive compared to RSW. Weldbonding (a combination of adhesive bonding and
resistance spot welding) increases joint strength considerably, compared to RSW
without adhesive. However, the strength of weldbonded joints is always lower than that
of a corresponding adhesively-bonded joint – the metallic spot weld actually decreases
the joint strength of an adhesive joint, in this type of test.
Another interesting feature is that with fusion processes (i.e. laser and resistance
welding) base-material strength level has only a marginal effect on joint strength. This
is because in a lap joint the solidified weld pool alone carries the load and, since the
strengthening effect of cold forming obviously disappears during melting and resolidification,
the weld strength remains more or less the same regardless of pre-
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