Stability Analysis of Fluid-Conveying Beams using Artificial Intelligence

This paper employs artificial intelligence in predicting the stability of pipes conveying fluid. Field data was collected for different pipe structures and usage. Adaptive Neuro-Fuzzy Inference System (ANFIS) model is implemented to predict the stability of the pipe using the fundamental natural frequency at different flow velocities as the index of stability. Results reveal that the neuro-fuzzy model compares relatively well with the conventional finite element method. It was also established that a pipe conveying fluid is most stable when the pipe is clamped at both ends but least stable when it is a cantilever

Large Deformation Behaviour of Continuum Compliant Systems

ABSTRACT Continuum topology of continuous, monolithic compliant mechanisms is designed for finite elastic deformation such that an output port moves in a desired direction when a specified force is applied through an input port. The pseudo-rigid body equivalent of compliant mechanisms (CMs) has been the conventional approach used by earlier researchers to synthesize and analyze compliant mechanisms. Attempts at direct analysis from existing literature are predicted on such assumptions as static linearity or a few times geometric nonlinear conditions. These are justifiable in several situations where compliant systems have been successful in replacing materials with several moving parts. However, the application domain of compliant mechanisms is widening to dynamic environment where the deformations are relatively large. It is therefore necessary to consider nonlinearities resulting from geometry and hyperelasticity. In this paper, methods of continuum mechanics and nonlinear finite element method were deployed to develop model that could capture the behaviour of compliant mechanisms. A hybrid system of symbolic algebra (AceGEN) and a compiled back end (AceFEM) were employed, leveraging both ease of use and computational efficiency. Numerical results using published laboratory investigated compliant mechanisms reveal the deviation that exists with linear and only geometric nonlinear assumptions

Deformation Characteristics of Composite Structures

The composites provide design flexibility because many of them can be moulded into complex shapes. The carbon fibre-reinforced epoxy composites exhibit excellent fatigue tolerance and high specific strength and stiffness which have led to numerous advanced applications ranging from the military and civil aircraft structures to the consumer products. However, the modelling of the beams undergoing the arbitrarily large displacements and rotations, but small strains, is a common problem in the application of these engineering composite systems. This paper presents a nonlinear finite element model which is able to estimate the deformations of the fibre-reinforced epoxy composite beams. The governing equations are based on the Euler-Bernoulli beam theory (EBBT) with a von Kármán type of kinematic nonlinearity. The anisotropic elasticity is employed for the material model of the composite material. Moreover, the characterization of the mechanical properties of the composite material is achieved through a tensile test, while a simple laboratory experiment is used to validate the model. The results reveal that the composite fibre orientation, the type of applied load and boundary condition, affect the deformation characteristics of the composite structures. The nonlinearity is an important factor that should be taken into consideration in the analysis of the fibre-reinforced epoxy composites

Effect of bismuth titanate on the properties of potassium sodium niobate-based ceramics

The effect of modifying the properties of KNN-based ceramics with Bi2Ti2O7(BiT) been investigated in this work. The density measurements show that additions of BiT to the samples slightly increase the density values. Scanning electron microscope images of the samples indicate that the average sizes of the grains decrease with BiT addition while the volume of pores increase. X-ray diffraction results show that for (K0.5Na0.5)NbO3based samples, a transformation from orthorhombic to pseudo-cubic phase is observed. For both K0.48Na0.48Li0.04)(Nb0.9Ta0.1)O3and K0.48Na0.48Li0.04)(Nb0.86Ta0.1Sb0.04)O3-based compositions, the phase transition is from an orthorhombic-tetragonal coexistence to a tetragonal structure dominated phase coexistence. The dielectric constant, dielectric loss and resistivity values of the samples increase slightly with BiT addition. Good hysteresis curves are obtained in (K0.5Na0.5)NbO3-based samples only at low BiT amounts. Remnant polarization values between 9 μC/cm2and 25 μC/cm2are obtained for K0.48Na0.48Li0.04)(Nb0.9Ta0.1)O3and K0.48Na0.48Li0.04)(Nb0.86Ta0.1Sb0.04)O3-based samples. With the exception of KNNLT samples where the d*33values increase from 203 ± 7 pm/V at 0 mol% to 275 ± 6 pm/V at 0.35 mol%, the d*33values of the samples gradually decrease with increasing BiT content. This work shows that to obtain good properties for KNN-based ceramics, only very small amounts of BiT are required.Deutsche Forschungsgemeinschaft SCHN 372/16:1-

Acoustic Pressure Waves in Vibrating 3-D Laminated Beam-Plate Enclosures

The effect of structural vibration on the propagation of acoustic pressure waves through a cantilevered 3-D laminated beam-plate enclosure is investigated analytically. For this problem, a set of well-posed partial differential equations governing the vibroacoustic wave interaction phenomenon are formulated and matched for the various vibrating boundary surfaces. By employing integral transforms, a closed form analytical expression is computed suitable for vibroacoustic modeling, design analysis, and general aerospace defensive applications. The closed-form expression takes the form of a kernel of polynomials for acoustic pressure waves showing the influence of linear interface pressure variation across the axes of vibrating boundary surfaces. Simulated results demonstrate how the mode shapes and the associated natural frequencies can be easily computed. It is shown in this paper that acoustic pressure waves propagation are dynamically stable through laminated enclosures with progressive decrement in interfacial pressure distribution under the influence of high excitation frequencies irrespective of whether the induced flow is subsonic, sonic , supersonic, or hypersonic. Hence, in practice, dynamic stability of hypersonic aircrafts or jet airplanes can be further enhanced by replacing their noise transmission systems with laminated enclosures