Advanced Materials Research Vol. 445

Abstract: This work focused to investigate the use of a powered automatic technique to insert acetabular cup implants. The use of a percussion hammer tool as a surgical instrument to insert acetabular cup implants was investigated in current work. Pull-out, lever-out and torque tests were carried out on cup implants inserted into test block specimens of polyurethane (PU) using specifically designed experimental setups as a means of comparing the current mallet and cup introducer (manual impaction) technique against the percussion hammer tool (powered impaction) technique. The experimental tests were based on calculating the maximum forces or moments of forces required to remove the cup implants from a test block specimen, which was representative of the acetabulum of the pelvic bone. It was found, the cup implants inserted using the powered impaction technique required a greater applied force, moment of force and torque in order to remove the cup from the cavity of the PU block specimen in the pull-out, lever-out and torque tests respectively. In terms of stability, the percussion hammer tool has the potential to improve the seating of cup implants within the cavity using a more precise and controlled technique, thus improving the over stability of the inserted cup implant.

Abstract: In this study, interacting crack growth in an infinite plate is analyzed with new, fast and accurate Boundary Cracklet Method (BCM) developed by Phoenix and Yavuz. An interior crack is under consideration to watch its propagation because of cyclic loading which is very common for aerospace, naval and civil engineering structures. BCM is very useful to determine the overall stress field as well as stress intensity factors for crack tips and singular wedges at crack kinks. BCM uses integral equations expressed in terms of unknown edge dislocation distributions along crack lines. These distributions derive from an accurate representation of the crack opening displacements using power series basis terms obtained through wedge eigenvalue analysis, which leads to both polynomial and non-polynomial power series. The process is to choose terms of the series and their exponents such that the tractions on the crack faces are virtually zero compared to the far field loading. Applying the method leads to a set of linear algebraic equations to solve for the unknown weighting coefficients for the power series basis terms to make no use of numerical integrations unlike in other methods. Thats why, solution takes just a few seconds on a PC. A simple crack growth emanating from a triangular hole in an infinite plate is analyzed. The fatigue crack growth is assumed to follow Paris-Erdogan Law. The results are compared to those of other numerical methods. A parametric study is performed via graphs and tables to demonstrate the ability of BCM in analysis of fatigue crack growth.

Abstract: In this work, numerical implementations of a new biaxial fabric of interlaced yarns model for ballistic impact into flexible body armor are presented. First the model is applied to a single-layer panel of polyethylene Dyneema® fibers in a matrix and impacted by various projectile geometries. We obtain the model results from a mass-spring, finite-difference model by modifying the code first developed at DSM. The results of the model are compared with experimental results and our previous biaxial model from firing 9 mm and FSP projectiles into Dyneema® panels. For both models, parametric studies are presented using 2-D and 3-D graphics. The new biaxial interlaced yarns model extends our previous biaxial and axisymmetric membrane model by addressing biaxial influences on material inflow to the impact cone. The new model is much more complete and produces velocity, strain and deformation histories for the full system up to perforation or projectile halting. It can also treat cases of mixing different fabric types, which can result in interference effects depending on the layer stacking order, and can treat multiple layers with air gaps in between, where we will show that such gaps can seriously degrade performance.

Abstract: While firms are operating in a global competitive environment, they are subjected to changes because of the increased competitiveness and developed technologies. Therefore, this transformation process forces to produce with just-in-time production and low cost products or services and leads to customer satisfaction. Until today, competitive conditions, efficiency, productivity and quality of production, forced the firms to put more emphasis on production systems. Therefore, the firms are more interested in scientific analysis, planning and controlling of their production systems. As a result, one of the newest approaches is Just in Time (JIT) production system which emerged after WWII in Japan and aims to decrease the inventory cost and maximize the quality. The philosophy of this approach is to produce the necessary amount of production, when and where needed at the required quality. But JIT production system is weak in unclear species. For this purpose, the general and necessary solution is using fuzzy logic. In this paper we discussed about the simulation of an assembly line with 3 steps; firstly using Kanban production method, secondly non-using Kanban production method, and lastly using Kanban production method with fuzzy times. And also the comparisons of these steps will also be studied in this paper.

Abstract: Slideways in machine tools are usually scraped to form small oil reservoirs serving as hydrodynamic wedges to generate hydrodynamic pressure and separate the carriage from the slideway during the sliding movement of the carriage. The pressure distribution and load carrying capacity are among the most important parameters in these hydrodynamic bearings. In the present work, the hydrodynamic lubrication theory has been adapted for use in modeling the hydrodynamic lubrication function of scrapings in machine tool slideways. A specially designed experimental setup was employed to verify the theoretical estimation for pressure distribution in scrapings. The experiments were implemented by using capillary tubes mounted in different distances along the scrapings for obtaining the profile of the hydrodynamic pressure distribution. The ram effect could also be clearly distinguished which exhibited its role with a pressure rise at the inlet to the bearing.

Abstract: The experimental investigation of UAT shows that the movement of cutting tool edge relative to the workpiece results from the cutting speed, feed speed and tools vibration in tangential direction affects the lateral machined surface of workpiece and leaves a repeating pattern of toothed regions on it. In UAT process, because of constant feed rate of tool toward workpiece, the cutting tool never separates from workpiece, though the tool rake face may separate periodically from chip in every cycle of vibration. This results in an increase in the surface hardness of the lateral machined surface in comparison with conventional turning (CT). The results of the present study confirm the advantage of UAT as far as the lower cutting force is concerned compared with CT. The higher surface hardness of the lateral surface observed in UAT causes the maximum cutting force to increase but the average force decreases with respect to CT.

Abstract: Failure analysis investigation was conducted on 70 MW set of 1^st stage turbine nozzle guide vanes (NGVs) of heavy industrial gas turbine. The failure was investigated using the light optical microscope (LOM), X-ray diffraction analysis (XRD) and energy dispersive X-ray spectroscopy (EDS) in an environmental scanning electron microscope (ESEM). The results of the analysis indicate that the NGVs which were made of Co base superalloy FSX-414 had been operated above the recommended operating hours under different fuel types in addition to inadequate repair process in previous repair removal. The XRD analysis of the fractured areas sample shows presence ofwhich might indicate the prolonged operation at high temperature. Keywords: cobalt-base; nozzle guide vanes, gas turbine.

Abstract: The sonic tomography and infrared thermograph techniques are incorporated to monitor the orientation and the size of the defect sites in the palm tree trunks. The tests are carried out for various conditions of the palm tree trunks, which have the large defect sites caused by the insects. The sonic tomography technique relies on the measurement of the relative sound wave speed by the detectors when the palm tree trunk is excited through the external forces. This technique enables to separate and quantify the damage and the intact volumes. It is found that sonic tomography can be used to identify the damage sites within a reasonable accuracy. The images obtained from the infrared thermograph technique provide information on the presence of the defect sites with the limited capacity for the location and the size of the defect sites in the palm tree trunk.

Abstract: The purpose of this paper is to improve a new part for the natural gas sector using Quality Function Deployment (QFD) technique. QFD methodology was chosen for the product improvement process at IGDAS (Istanbul natural gas distribution company), the biggest natural gas distribution firm in Turkey. Experts from engineers were selected to determine customer expectations. Application of QFD to pipe strangling equipment is described step by step. The results show that when developing a new product or improving a product both customer expectations and product requirements are evaluated at the same time pleasing both parties for a successful result.

Abstract: This study clarifies the fatigue properties using global signal statistical approach during the crack initiation stage for metallic component. Strain loading and acoustic emission (AE) signatures are captured simultaneously in the form of signal waves recorded by strain gauge and AE transducer. An initial study was carried out in the laboratory on medium carbon AISI 1045 steel specimens at constant amplitude cyclic loading condition, which lead to the fatigue failure characteristics. This study was carried out to investigate the relationship between strain and AE signals in order to make sure that AE technique also can be used as a detecting and monitoring crack initiation in metallic specimens. To achieve the goal, three different loads were applied on three specimens to capture the differences of the signals. The specific data acquisition systems were used to collect strain and AE signatures. For the purpose of analysis, the method of root mean square (r.m.s) and the kurtosis were used. The r.m.s value was used to quantify the overall vibrational energy content whereas the kurtosis was then used because of its sensitivity to high amplitude events. Based on these statistical approaches, the correlation patterns between both signals are expected to give a meaningful baseline to predict and monitor crack initiation of a metallic specimen.