Numerical study of mechanical behaviour of tubular structures under dynamic compression
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abstract
Finite element analysis (FEA) is a tool used to predict responses, reproduce experiments, and improve the performance of devices. Modern production techniques, such as 3D printing, enable researchers to investigate structures with complicated shapes and made of mixed materials, thereby increasing the application of simulation and FEA. In this thesis, finite element package ABAQUS is used to numerically investigate the behavior of components subjected to axial static and dynamic loadings.
The effect of cladding a ductile material during ring compression test and energy absorption (EA) of circular tubes is evaluated. The addition of layers of a ductile material to the cross section of a ring increases its compressibility. The EA of circular tubes is improved when the layers of a soft material are located in the model.
Rings with various geometric ratios and shape factors are subjected to axial static loading. The calibration curves for different friction coefficients are plotted. The behavior of the rings and their calibration curves are predictable when the geometric ratio and shape factor of the models are the same. For the rings with the same shape factor but different geometric ratios, the calibration curves can be located lower or higher in the diagram regardless of their size.
The application of hydrostatic pressure to the inner and outer walls of a ring increases its compressibility by changing the tangential and radial stress distributions. Cladding the outer wall of a ring with a soft material changes the stress distribution and increases
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compressibility. The state of radial stress is easier to change from tensile to compressive in comparison with tangential stress.
The force–displacement diagrams of corrugated tubes with different number of grooves and groove sizes are divided into three parts. The optimum model that shows the best performance has the same area under the curve of each part. The grooves as triggers can control the location and value of the peak force in the diagram. The size and shape of these triggers should be optimized. The model with regular fluctuations and without any peak force can be considered the optimum model.
The addition of layers of a ductile material to the base model improves the crashworthiness of structures. The volume fraction of clad material and its location should be optimized. For the circular tubes as energy absorbers, the addition of some layers at a 45° angle increases EA and crush force efficiency.
