a b s t r a c tTheoretical analysis of the propagation of stress waves in cellular solids with non-uniform density, and consequently strength, is carried out to deepen the understanding of their dynamic compaction due to impact loading. Materials with continuously varying density in the direction of loading are considered when analysing the response to two types of loading conditions: an impact of a stationary cellular block by a rigid mass and an impact of a cellular block on a rigid wall. It is assumed that the local stress-strain characteristics of the graded materials exhibit strain hardening. The plastic strain field in the deformed graded cellular solid is sought here as a function of the impact velocity and material properties when using the Hugoniot material representation. It is shown that the initial density variation with respect to the boundaries of a finite thickness block has a significant effect on the history of the stresses and strains during the compaction process.FE models using ABAQUS are constructed and numerical simulations are carried out to verify the predictions of the theoretical analysis. Attention is paid to the energy absorption capacity of the materials depending on their initial density distribution when comparing their dynamic responses with the response of equivalent mass cellular block with uniform density. Significant advantages in using density graded cellular solids in finite thickness layers are not identified for the analysed loading rate.
This paper presents a study on the structural behaviour of stainless steel profiles under fire conditions. An experimental campaign of three‐point bending tests on rectangular hollow section beams of the grade 1.4301 (also known as 304) were conducted, considering both steady‐state and transient state conditions. Prior to those tests, the mechanical characterization of the stainless steel was investigated. The constitutive laws obtained by tensile tests at high temperatures are compared with those recommended in Eurocode 3, whose respective material models were recently proposed for modifications, still requiring complete validation. In addition, numerical modelling of the bending tests has been performed afterwards achieving close approximation to the observed experimental results. Finally, analytical methods to predict the load‐deflection behaviour are also presented. Good agreement between the considered methodologies was attained validating their application on the prediction of the fire behaviour of stainless steel beams.
The existing tire models are basically of three kinds: essentially empirical ("magic formulas"), or mixed empirical/analytical, or extremely complex theoretical models almost useless in practical situations. The model here proposed does not require any empirical data, and presents a simple theoretical approach very suitable to use in project and analysis of real suspension systems. This paper presents a physical and mathematical model for the mechanical behavior of pneumatic car tires, in the particular case of vertical loading. It is a theoretical model, in the sense that it does not require any empirical data. It is based on the perfectly flexible and quasi-inextensible membrane theory, and its formulation does not rely on any tire material property-it is exclusively geometric. The calculated results from this model are compared with measured data from four quite different types of tires: two used in small passenger cars, one high performance tire used in sport vehicles, and other heavy duty tire used in SUV's. In all cases, the differences between measured and calculated data were lower than 5% in the normal range of pressure and loading.
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