Pedicle bone screws are one of the most critical materials used in spinal orthopaedic operations. Screw loosening and pull-out (PO) are basic complications encountered during or after surgery. Pull-out Strength (POS) of the bone is one of the significant parameters to understand the mechanical behaviour of a screw fixed to poor quality or osteoporotic bone. This study investigates how the POS of a pedicle screw is affected by the factors of the screw diameter and the polyurethane (PU) foam density by experimental analysis. In the experiments, two different diameter (5.5 and 6.5 mm) of conical pedicle screws and five different density (0.08, 0.16, 0.24, 0.32 and 0.48 g·cm−3) PU foams were used. According to the force-displacement curves obtained from experimental results, the POS increased with the increases in screw diameter and PU foam density.
Alumix 431 metal powders have been used in this study since they are widely used in the industrial applications. First, Alumix 431 powders were compacted at 400 MPa pressure under room temperature (RT). Then, pressed specimens were sintered separately at 600 and 620 8C for 1h N 2 . Densities were measured for the different temperatures in order to examine the effects of the sintering on density. Improvement of green density was observed to have enhanced approximately 86 and 90% according to theoretical density (2, 786 g/cm 3 ) as a result of the sintering condition at 600 and 620 8C, respectively. After sintering a group of specimen was shot peened with the intensities in 12 and 16A. To investigate mechanical properties of as sintered (unpeened) and shot peened samples, tensile and fatigue tests were performed. It was determined that shot peening improved the fatigue strength about 10 and 15% in 12 and 16A intensities, respectively. In addition, fractured specimens after tensile tests were used for MicroHardness measurements, and for metallographic analysis by, optical microscopy (OM) and scanning electron microscopy (SEM) tests further specimens were examined.
Acoustic emission (AE) is a nondestructive testing (NDT) technique used for detecting damages, cracks, and leaks in different structures such as metals, composites, wood, fiberglass, ceramics, plastics, etc. In recent years, AE has gained popularity within the field of biomedical applications. The structure of bone is similar to composite materials, therefore, it is advantageous to use NDT technique. Thus, it can be used for monitoring the fracture behavior, crack initiation/propagation, and fatigue detection in bones. The goal of this study was to determine the usefulness of AE techniques in fracture detection phase of bones and to develop an NDT methodology for the monitoring of crack initiation and propagation in bones. This study describes AE activity during fracture of bone tissue under tensile loads. The experiments were carried out in vitro techniques using intact and fracture-simulated bovine tibias. The specimens were loaded to failure in tension using a mechanical testing machine. During the mechanical tests, AE signals were measured and recorded by using AE system processor equipped with two wideband piezoelectric sensors fixed to the surfaces of both ends of the test specimens. By superposing the load–time curve and the cumulative AE event–time curve, AE activities of crack initiation and propagation were identified. In all experiments, the cumulative AE number for each period of time rose up exponentially with the incremental tensile load. Load for AE initiation demonstrated a convincing linear interaction with AE event generation.
The significant challenge in today's automotive industry is to defeat the increasing demands for higher performance, longer life, and lower weight of components in order to satisfy fuel economy requirements at a realistic cost using safety requirements. The aim of this study is to design and analyze the chassis of an electrically operated golf cart for use in Çukurova University campus. Chassis is a frame just like skeleton on which various machine parts like engine, tires, axle assemblies, brakes, steering etc. are joined. It gives strength and stability to the vehicle under different conditions. The main function of the chassis is not only to support the components and payload mounted upon it including engine, body, passengers and luggage, but also to maintain the desired relationship between the suspension and steering mechanism mounting points. In this study; 3D models of chassis were designed using SolidWorks by considering different types of profiles. Structural analyses were conducted on the golf cart chassis with various materials and profiles via ANSYS software using Finite Elements Analysis (FEA) method. The aim of the design was to achieve sufficient strength and minimum deflection values with optimum weight, cost and ease of manufacturing.
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