A computational model was developed to simulate elastic and plastic behavior in Body Centered Cubic (BCC) metals and alloys. The model provided for simultaneous simulation of the micro and macro length scales and used periodicity to link the two length scales. The model was implemented in a 3dimensional framework giving rise to a finite element technique incorporating intrinsic dislocation information in the simulation of the material’s behavior. The technique was validated by simulating loading over the elastic range and the immediate region beyond yield, of thin steel strips, and comparing the results to those obtained by conventional analysis. Stress-strain curves and slip plane percentage contribution factors were generated. Specifically the stress-strain curves generated upheld Hooke’s law and demonstrated a definite yield plateau followed by material recovery after yielding.
Ultrasound technology has become an important aspect in material handling and machining. Standing and traveling ultrasonic waves have been applied in powder transportation, feeding, dosing and supply of small amounts of powder with high quantitative accuracy and precision. Piezoelectric actuators are the most commonly used to generate the ultrasonic waves in various devices. Hence, these devices have presented a unique, economic and simple means of accurate handling of powder. This paper describes the determination of the resonant frequency of a piezoelectric ring that can be applied for generation of the ultrasonic waves. The resonant frequency is important in determining the highest amplitude of the vibration of the ring.
A three-dimensional FEM computer program was developed to establish the stress distributions and SCFs in thick walled cylinders with flush and nonprotruding plain cross bores under internal pressure. The displacement formulation and eight-noded brick isoparametric elements were used. The Frontal solution technique was used due to the limited computing facilities. In the far field, the FEM stresses and displacements were in good agreement with the through thickness analytical values. The variation of SCF with d was established for various thickness ratios. For k> 1.25, the maximum hoop stress occurred away from the crotch corner when d≤0.2. For k=1.25, the maximum hoop stress occurred away from the crotch corner when d≤0.15. For k≥1.75, d was found to be a geometrical constant equal to 0.2 where the k values have a SCF of 2.734. For k
The mechanical properties of sisal fibre, loofah matt, epoxy resin and their resulting composites were determined experimentally. The influence of volume fraction of the reinforcing fibres and matt on the mechanical properties of the composites was investigated. It was found that loofah matt reduces the mechanical properties of epoxy resin and as such loofah is not a suitable reinforcing material. Sisal fibre on the other hand does improve the mechanical properties of epoxy resin; the improvement being dependent on fibre volume fraction. This makes fibre reinforced composites useful practical materials. Based on the “effective reinforcement” and the advent of multiple matrix fracture, design limitations for the composites were set.