Hot Forming of 7075 Aluminium Alloy Tubes to Produce Complex and Strong Components 2012-01-0539
Lightweight tubular products offering enhanced stiffness and
strength have always been of major concern for transportation and
recreational applications. Hence, industries have turned to
complex-shaped tubes to increase product performance and reduce
energy costs. High-performance aluminum alloys, like 7075 for
instance, have good mechanical properties such as high strength,
but low formability at ambient temperature.
Fortunately, hot tensile tests on 7075 samples have yielded an
increase in formability with temperature. Therefore, testing has
recently been launched at the Aluminum Technology Center to develop
a new product application. More precisely, a 1,000-ton hydraulic
press was equipped with +600°C heating plates and fitted with a
bicycle handlebar mold. The plates provide 10 separate heating
zones that can be adjusted independently. A thermo-mechanical model
was also developed using LS-DYNA to determine tube temperatures
around the heating zones. Hot tensile test results were also
utilized to model tube behavior using an elastic viscoplastic
temperature-dependent material constitutive law to predict tube
wall stresses and strains.
The finite element model can predict tube temperatures and gas
pressures relative to time. Hot-forming process parameters were
rapidly adjusted to successfully produce perfect handlebars.
Conclusions not only include successful application where high
formability is required, but also lead to a significant decrease in
forming loads and lower tooling and mechanical energy costs.