Loading In Longitudinal Direction Research Articles

Effect of unidirectional lateral cyclic load path on hysteretic response of battened steel columns – A numerical investigation

During earthquakes, battened steel columns are subjected to both compressive load in longitudinal direction and cyclic load in lateral direction. The effects of unidirectional lateral cyclic stress on a double channel battened column (DCC) were investigated using ABAQUS software in this paper. Four different unidirectional lateral displacement controlled load paths (U1, U2, U3, and U5) were considered for this study. As per the study, the lateral load carrying capacity (LCC) and peak lateral displacement are significantly affected by the unidirectional lateral cyclic loading path. The results showed that the peak lateral displacement of the columns reduces considerably, with a minor effect on LCC when number of cycles applied for certain deformation level increases.

A New Aircraft Taxiing Model Based on Filtering White Noise Method

The conversion relationship between power spectral density (PSD) and international roughness index (IRI) was studied based on the filtering white noise method with variable sampling frequency using a quarter vehicle model. Six-degree-of-freedom dynamic equations of the whole aircraft taxiing were obtained considering the lift, upstream and downward bump, roll and pitch motion of the airframe. And then the dynamic load factors of the aircraft wheels under different pavement roughness and various airspeeds were solved by SIMULINK toolbox. The results shown that the mean dynamic load is independent of the pavement roughness, whose values are approximately equal to the load when the aircraft glided on the smooth pavement. The worse the pavement roughness, the greater the maximum dynamic load factor. There are approximately linear relationships between IRI and the maximum dynamic load. When the aircraft glides at low airspeed, the dynamic load increases as the increasing of airspeed. Then the maximum dynamic load factor decreases with the increase of running velocity. Moreover, the formulas for calculating the wheel dynamic load factor under the coupling action of pavement roughness and airspeed were proposed, which could be used to calculated the distribution of the dynamic load in longitudinal direction of the runway and determine the dynamic load values in airport pavement design.

Tailoring strength and modulus by 3D printing different continuous fibers and filled structures into composites

Three-dimensional (3D) printing is one of potential technologies for production of designable complex filled structures and mechanical strengthening along the reinforcing fibers for composites. The objective of this paper is to study the tensile mechanical behavior of diverse concentric fiber rings and fiber layers using glass fiber (GF), Kevlar fiber (KF), and carbon fiber (CF) printed into polymer composites and then to compare them. Additionally, it also aims to identify the influence of complex filled structures of Nylon on different fiber printed polymer composites. Tensile tests and scanning electron microscope (SEM) were utilized to characterize the 3D printed composites. Results revealed that CF-printed composite exhibits the greatest tensile strength of 110 MPa and modulus of 3941 MPa as compared to glass and Kevlar fiber composites. Increase of concentric fiber rings and fiber layers is attributed to increase in tensile strength and modulus. Also, the rectangular filled structure of Nylon declared the highest tensile strength and modulus than hexagonal and triangular filled structure owing to its rectangular filling that bears maximum load in longitudinal direction.

Influence of mixed isotropic fiber angles and hot press on the mechanical properties of 3D printed composites

This paper aims to study the mechanical properties of mixed isotropic carbon fiber 3D printed composites and further investigates the influence of hot press on the [0°/45°/90°]2 fiber angles composite with varying temperature, pressure and time. Tensile tests, autoclave treatment and microstructural observation were utilized to characterize the composites. Results revealed that the [0°/45°/90°]2 performed the highest tensile strength of 79 MPa and modulus of 3.51 GPa, compared to [30°/45°/60°]2 and [15°/45°/75°]2. This is due to the fibers along the tensile axis angle that bears maximum load in longitudinal direction. At 200 °C temperature, the hot pressed composites presented the highest tensile strength of 98 MPa and modulus of 3.93 GPa than non-hot pressed. Increased temperature caused better interface wettability between fibers and matrix. At 200 kPa pressure, the hot pressed composites showed the highest tensile strength of 100 MPa and modulus of 4.06 GPa than non-hot pressed. Further increased pressure resulted in lower tensile strength and modulus, as the material became stiffer pushing more matrix material to side leaving numerous fibers unbounded by the matrix. For 30 min withholding time, the hot pressed composites indicated the highest tensile strength of 106 MPa and modulus of 4.27 GPa than non-hot pressed. Increased time caused strongest interface bonding by removing the air gaps induced during printing between fibers and matrix. Results revealed that hot press significantly improved the mechanical properties of carbon fiber 3D printed composites.

A numerical modeling study on the influence of catalyst loading distribution on the performance of Polymer Electrolyte Membrane Fuel Cell

In this study, the effects of different non-uniform catalyst loading distributions that vary in both lateral and longitudinal directions on the performance of Polymer Electrolyte Membrane Fuel Cell (PEMFC) were numerically examined in detail. A two-phase, multi-component, transient and three-dimensional model was employed for simulating the performance of the cathode half-cell of the PEMFC. At the first step, the best longitudinal catalyst loading distribution was found. At the second step, several lateral distributions were superimposed to the noted longitudinal catalyst loading distribution and the performance of the PEMFC was evaluated for each distribution. Numerical results showed 3.1% enhancement for the longitudinal catalyst loading distributions; while 8% improvement was observed with a non-uniform catalyst loading distribution in both longitudinal and lateral directions. Results indicated that when lateral distribution is employed, liquid water saturation in the rib side is reduced. In the best longitudinal distribution, the ratio of platinum loading in longitudinal direction was 1.857 and the ratio of platinum catalyst from the center region of the catalyst layer to the rib side is varied in a wide range. In the case of the noted ratio more than 30, the enhancement in the PEMFC performance was insignificant. Finally, the effect of catalyst loading distribution was investigated on the polarization curves. It was found that the catalyst loading distribution is most effective at the high current densities while it has a minor effect at low current densities.

Buckling analysis of anti-symmetric cross and angle-ply laminated composite plates

This article has for objective to analyze the buckling behavior of the unidirectional laminated plates. In this purpose, we propose an analytically method, based on the theory of classical, orthotropic plate theory. The governing equations are solved using Navier solution for uniform uniaxial loading in longitudinal direction. We were interested to identify the critical buckling load for simply supported antisymmetric cross-ply and antisymmetric angle-ply laminates of rectangular shape. Some important progress has been made on these relatively complicated buckling problems, involving coupling between bending and midplane stretching during a buckling deformation. Effects of different parameters such as fiber orientation angles, aspect ratio, modular ratio and number of layers were examined. Results are presented in the form of plots showing the variation in non-dimensional buckling load.

Knots in trees: strain distribution in a naturally optimised structure

Electronic speckle pattern interferometry was applied to directly measure the distribution of longitudinal, tangential, and shear strains in small boards of Norway spruce (Picea abies (L.) Karst.) exposed to tensile load in longitudinal direction. A sample with a central intergrown knot and one with an equivalent loose knot were compared with reference samples made of clear wood with an artificial central circular or square hole, respectively. The observed measurements were compared with a finite element (FE) simulation. The FE model was based on a geometric model to quantify the local fibre orientation and a micromechanical model to estimate elastic constants of clear wood and knot tissue. Both the measurements and simulation clearly illustrate a rather homogenous strain distribution around the intergrown knot. In comparison, the natural optimisation of dispersing strain peaks is less efficient in the case of loose knots. The artificial circular and square holes in samples with parallel fibre orientation lead to high gradients in the strain field and peak values in vicinity of the disturbance.