Abstract
AbstractAluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms. A major concern in the design of land-based and marine aluminum structures is fire safety, at least in part due to mechanical property reduction at temperatures significantly lower than that for steel. A substantial concern also exists regarding the integrity and stability of an aluminum structure following a fire; however, little research has been reported on this topic. This paper provides a broad overview of the mechanical behavior of aluminum alloys both during and following fire. The two aluminum alloys discussed in this work, 5083-H116 and 6061-T651, were selected due to their prevalence as lightweight structural alloys and their differing strengthening mechanisms (5083 – strain hardened, 6061 – precipitation hardened). The high temperature quasi-static mechanical and creep behavior are discussed. A creep model is presented to predict the secondary and tertiary creep strains followed by creep rupture. The residual mechanical behavior following fire (with and without applied stress) is elucidated in terms of the governing kinetically-dependent microstructural mechanisms. A review is provided on modeling techniques for residual mechanical behavior following fire including empirical relations, physically-based constitutive models, and finite element implementations. The principal objective is to provide a comprehensive description of select aluminum alloys, 5083-H116 and 6061-T651, to aid design and analysis of aluminum structures during and after fire.
Highlights
Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms
Stress-strain relations The residual stress-strain behavior of 5083-H116 and 6061T651 after heating at 20°C/min are shown in Figure 18. 5083 (Figure 18a) exhibits significant strain hardening in the as-received state which increases considerably with increasing prior exposure temperature
Summary Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms
Summary
Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as lightweight structures, light rail, bridge decks, marine crafts, and off-shore platforms. A major concern in the design of land-based and marine aluminum structures is fire safety. This concern is exacerbated for aluminum alloys due to property degradation which occurs at temperatures as low as 150°C with a 50% yield strength reduction at ~275°C (Langhelle and Amdahl 2001). Limited research has been conducted on the residual mechanical behavior of aluminum following fire This is a pertinent issue that requires consideration to effectively evaluate structural stability following a fire and assess replacement of fire damaged structural elements. Analysis and design of aluminum structures requires a well-developed understanding of both the elevated temperature and residual mechanical behavior of the aluminum alloys of interest. The work presented in this paper focuses on two specific alloys: 5083-H116 and 6061-T651, which are commonly used structural alloys for lightweight applications
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