Constitutive model for aluminum alloys exposed to fire conditions
article
An existing constitutive model for creep, developed by Dorn and Harmathy, is modified in order
to be used for fire-exposed aluminum alloys. Two alloys, 5083-O/H111 and 6060-T66, are
selected for the development of this constitutive model because of their different behavior at
elevated temperature and their frequent application in structures for which fire design is relevant.
The material parameters in the model are calibrated with the experimental results of creep
tests, carried out with constant load and temperature in time. The model is validated with so
so called transient state tests, with a constant load in time (stresses ranging from 20 to 150 N/m2)
and with an increasing temperature (with heating rates ranging from 1.6o C/min to 11 o C/min
and critical temperatures ranging from 170 o to 380 o C. These tests are considered as representative
for fire-exposed, insulated aluminum members. The existing constitutive model of
Dorn and Harmathy provides good agreement with the transient state tests carried out for the
5xxx series alloy, but appeared to be not suited for the 6xxx series alloy. This is attributed to the
early development of tertiary creep in case of 6xxx series alloys. The existing model was
modified to incorporate this first stage of tertiary creep, to arrive at a good agreement between
the tests and the modified model for 6xxx series alloys
to be used for fire-exposed aluminum alloys. Two alloys, 5083-O/H111 and 6060-T66, are
selected for the development of this constitutive model because of their different behavior at
elevated temperature and their frequent application in structures for which fire design is relevant.
The material parameters in the model are calibrated with the experimental results of creep
tests, carried out with constant load and temperature in time. The model is validated with so
so called transient state tests, with a constant load in time (stresses ranging from 20 to 150 N/m2)
and with an increasing temperature (with heating rates ranging from 1.6o C/min to 11 o C/min
and critical temperatures ranging from 170 o to 380 o C. These tests are considered as representative
for fire-exposed, insulated aluminum members. The existing constitutive model of
Dorn and Harmathy provides good agreement with the transient state tests carried out for the
5xxx series alloy, but appeared to be not suited for the 6xxx series alloy. This is attributed to the
early development of tertiary creep in case of 6xxx series alloys. The existing model was
modified to incorporate this first stage of tertiary creep, to arrive at a good agreement between
the tests and the modified model for 6xxx series alloys
TNO Identifier
331454
Source
International Journal of Metallurgical and Materials. Transactions A, 39A(April), pp. 778-789.
Pages
778-789
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