Mechanical strength of highly preloaded bolts affected by the ovalization of an aircraft wheel

This work presented in this paper concerns the modeling of the tensile and bending behavior of bolts in an airplane wheel. The design of a very rigid airplane tire means that the airplane wheel must be separated into two parts. In order not to have a separation between the two parts, several bolts with high preload are used. The main objective of this work is to predict the mechanical behavior of this assembly in a preliminary design phase with geometrical and global mechanical data. To achieve this objective, a simplified semi-numerical 1D model is developed. The complex geometry of the wheels is modeled by axisymmetric elements, while beam elements define the geometries and mechanical behavior of the bolts. The model is improved in non-axisymmetric cases to include the ring effect due to the wheel ovalization. Different cases are simulated (inflation and rolling). For each load case, the most stressed fastener is examined. Then, a comparison between its static and fatigue stress results and those of the 3D finite element reference model considered is analyzed for the validation of the developed tool. The semi-numerical model is used in the preliminary design phase and permits the geometric and mechanical properties of the aircraft wheel and fasteners to be defined so as to find the best assembly configuration that prevents separation.

Experimental Investigation on Bending Behavior of Existing RC Beam Retrofitted with SMA-ECC Composites Materials

In order to realize the self-centering, high energy consumption, and high ductility of the existing building structure through strengthening and retrofit of structure, a method of reinforced concrete (RC) beam strengthened by using Shape Memory Alloy (SMA) and Engineered Cementitious Composites (ECC) was proposed. Four kinds of specimens were designed, including one beam strengthened with enlarging section area of steel reinforced concrete, one beam strengthened with enlarging section area of SMA reinforced concrete, beam strengthened with enlarging section area of SMA reinforced ECC, and beam strengthened with enlarging section area of steel reinforced ECC; these specimens were manufactured for the monotonic cycle loading tests study on its bending behavior. The influence on the bearing capacity, energy dissipation performance, and self-recovery capacity for each test specimens with different strengthening materials were investigated, especially the bending behavior of the beams strengthened by SMA reinforced ECC. The results show that, compared with the ordinary reinforced concrete beams, strengthening existing RC beam with enlarging section area of SMA reinforced ECC can improve the self-recovery capacity, ductility, and deformability of the specimens. Finally, a revised design formula for the bending capacity of RC beams, strengthened with enlarging sections of ECC, was proposed by considering the tensile capacity provided by ECC, and the calculated values are in good agreement with the experimental value, indicating that the revised formula can be well applied to the beam strengthening with enlarging section of SMA-ECC Materials.

Mechanical and FEA-Assisted Characterization of 3D Printed Continuous Glass Fiber Reinforced Nylon Cellular Structures

The main objective of this study was to investigate the mechanical behavior of 3D printed fiberglass-reinforced nylon honeycomb structures. A Continuous Fiber Fabrication (CFF) 3D printer was used since it makes it possible to lay continuous strands of fibers inside the 3D printed geometries at selected locations across the width in order to optimize the bending behavior. Nylon and nylon/fiberglass honeycomb structures were tested under a three-point bending regime. The microstructure of the filaments and the 3D printed fractured surfaces following bending tests were examined with Scanning Electron Microscopy (SEM). The modulus of the materials was also evaluated using the nanoindentation technique. The behavior of the 3D printed structures was simulated with a Finite Element Model (FEM). The experimental and simulation results demonstrated that 3D printed continuous fiberglass reinforcement is possible to selectively adjust the bending strength of the honeycombs. When glass fibers are located near the top and bottom faces of honeycombs, the bending strength is maximized.

An investigation on the effect of nanoparticle reinforcement and weld surface shape on bending behavior of rotary friction-welded high-density polyethylene

In this research, high-density polyethylene rods were joined together using rotary friction-welding. The effects of nanoparticle reinforcement and weld surface shape on the welded joint strength were investigated. To this aim, high-density polyethylene rods with a length of 50 mm and a diameter of 22 mm were machined, and three weld surface shapes, that is, flat, step, and conic shapes (on male and female counterparts), were created. The high-density polyethylene rods were rotary friction-welded with the addition of ZnO and SiO2 nanoparticles. The bending strength of rotary friction-welded rods was assessed by conduction of three-point bending tests. The results showed that both the weld surface shape and nanoparticles influence the bending strength of the welded joints. It was found that the step sample welds have higher bending strength (average bending depth and force of 6.27 mm and 2027.8 N, respectively). Furthermore, except for the case of flat samples, the addition of the reinforcement nanoparticles resulted in the improvement of the bending strength of the rotary friction-welded rods.