Constitutive Model for Aluminum Alloys Exposed to Fire Conditions

Abstract

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 socalled transient state tests, with a constant load in time (stresses ranging from 20 to 150 N/mm 2 ) and with an increasing temperature (with heating rates ranging from 1.6°C/min to 11°C/min and critical temperatures ranging from 170°C to 380°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.

Aluminum Behavior during Fire Heating: Focus on Deformation

“…Additionally, aluminum alloys subjected to heat fluxes representative of a fire have been studied by Kandare et al [8] and Malijaars et al [9], who also performed Gleeble experiments using Al-5083-/H111 and Al-6060-T66 for different heating rates and loads. These materials were selected since they are frequently used in structures and display different behavior at elevated temperatures.…”

Larson–Miller Failure Modeling of Aluminum in Fire

“…In order for Eq. [7] to be applicable, the temperature-time profile was divided into linear segments so that the rate of temperature increase from temperature T i to T i+1 (i.e., one filled square to the next ( Figure 2)) is constant. Substituting Eqs.…”

“…Several models have been developed to predict the failure time or failure temperature of compression-loaded aluminum structures exposed to fire. [1][2][3][4][5][6][7][8] Suzuki et al [1] developed a stiffness-based softening model to calculate the critical failure temperature of aluminum exposed to fire. The model is inaccurate for low compression load conditions that involve long failure times, because time-dependent creep softening of the aluminum is ignored.…”

Failure Response of Simultaneously Pre-Stressed and Laser Irradiated Aluminum Alloys

“…There has been considerable work on understanding how structural metals deform under transient tensile conditions [7][8][9]. However, the research about the laser damage effect of aluminum and other structural materials under preloaded conditions is infrequent.…”