Two critical phenomena involving thermoplastic effects in crush and impact problems are the localization of plastic buckling patterns and shear localization. In the case of steel structures under compressive loading, it was observed experimentally that the final buckled pattern of structures exhibits a localized deformation in contrast to the periodic deformation pattern associated with the critical buckling mode. This phenomenon is referred to as localization of buckling patterns. Experiments showed that the stiffness as well as the strength of steel structures deteriorates considerably due to the localization of deformations in structural components. Furthermore, the localization of plastic buckling patterns results in a large plastic strain concentration, which may lead to an initiation of cracks. In this paper, the constitutive relation of plasticity with strain rate and temperature dependency was used to analyse the process of crushing and impacting of structures. Computer simulations of the localization of plastic buckling patterns and the initiation and development of adiabatic shear band were performed. The thermoplastic effects were investigated and discussed. From the study of this work it could be concluded that the localization of plastic buckling patterns are caused by the interaction of stress waves during impact process and the plastic deformation. The location of localized buckling is determined by the impact speed. Thermoplastic coupling has a great effect on the deterioration of the strength of a buckled column, and could result in a large plastic strain concentration. From the simulation on shear band it could be concluded that the impact speed, the geometric constraints, and the thermal softening characteristics have significant effects on shear localization. Among those, the thermal softening characteristic is the dominant factor on the formation of shear band. It is necessary to perform thermoplastic analysis in impact problem involving large plastic deformation. Thermal softening characteristics have a dual significance on high-speed impact: as a dominant factor on the initiation of shear band and thus on fracture, and as a mechanism of large strain plastic response.
Thermo-plastic effects on structural behaviour during crush and impact
Thermoplastische Einflüsse auf Struktureigenschaften bei Stoßaufprall
International Journal of Vehicle Design ; 30 , 1/2 ; 22-32
2002
11 Seiten, 6 Bilder, 1 Tabelle, 39 Quellen
Article (Journal)
English
Thermo-plastic effects on structural behavior during crush and impact
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