Advanced Materials Research Vol. 445

Abstract: An empirical solution for the thermal shock stresses in cylindrical shell presented when cylinder is subjected to heating or re-heating case and down-shock cooling by forced air case. Linear equations are developed to describe the severity of thermal shock loading. When thermal gradient and time period are in consideration, it is shown the equations displays good approximation for major characteristics of the thermal shock stress profiles.

Abstract: This paper discusses the uses of non-precious metals in catalytic converters to bring down the cost without sacrificing the performance capability. Copper powder and nickel catalyst were chosen as the alternative catalysts to reduce the use of precious group metals (PGMs) platinum, palladium, and rhodium. Simulation by COMSOL has shown that Nickel and copper were very effective in reducing NOx during rich condition of air-fuel mixture while oxidizing CO and HC during lean condition. Simulations using FLUENT and COMSOL have shown the actual characteristics of the catalytic converter performance. The flow throughout catalytic converter and the backpressure have successfully determined. Furthermore, catalyst conversion efficiency also has been shown clearly. On the other hands, the experimental results have excellently validated the simulation results in terms of the nature and trends of the catalytic converter performance as well as its efficiency. Catalyst distribution and application of the non-zoning monolith substrates have further contributes to cut down the production cost. It was found that the low cost catalytic converter was able to meet the EURO 2 emission regulation control and has optimum backpressure at full throttle.

Abstract: Feature recognition is a powerful tool for integrating CAD and CAM. Hint based algorithm is one of the most useful tools for recognizing features that is usually used with other algorithms forming hybrid systems. In the present study, hint based algorithm has been chosen as the main tool for recognizing machining features by defined recognition rules. Beside the need for low computation, the specific characteristic of the proposed recognition system is its multi-tool access direction (multi-TAD) property where the designed algorithm recognizes and lists each machining feature with its special access direction. It detects all the features available in each TAD and sorts the TADs in descending order of their number of features. The developed recognition system is capable of recognizing different types of isolated and nested intersecting feature types. The developed software accepts neutral file formats (i.e. STEP and IGES) beside the B-Rep CAD model as its input CAD file. The developed system has been tested with different CAD parts.

Abstract: The spring back is a major source of diametrical error occurring in turning of workpieces. In order to analyze diametrical error, an elastic deflection model of workpiece should be available. Many assumptions are usually taken into consideration when analyzing the elastic deformation of workpiece. Many studies have been done to find the analytical model of work-piece spring back and its suitable cutting force model. When compared with experimental data, developed models in these works are associated with considerable errors. In this paper, through using experimental results, an efficient elastic deformation model of workpiece has been obtained which can be compared with analytical model. Many experiments were performed, and some different functions were produced which predict the trend of experimental results. Finally, an appropriate model with the lowest error was suggested. The same process has been performed in ultrasonic vibrations assisted turning. The obtained functions will be suitable to compensate for the diametrical error occurring by machining forces. Finally this model has been used to obtain the amount of elastic spring back of tool and spindle.

Abstract: Leak detection is one of the most important problems in the oil and gas pipelines. Where it can lead to financial losses, severe human and environmental impacts. Acoustic emission test is a new technique for leak detection. Leakage in high pressure pipes creates stress waves resulting from localized loss of energy. Stress waves are transmitted through the pipe wall which will be recorded by using acoustic sensor or accelerometer installed on the pipe wall. Knowledge of how the pipe wall vibrates by acoustic emission resulting from leakage is a key parameter for leak detection and location. In this paper, modeling of pipe vibration caused by acoustic emission generated by escaping of fluid has been done. Donnells non linear theory for cylindrical shell is used to deriving of motion equation and simply supported boundary condition is considered. By using Galerkin method, the motion equation has been solved and a system of non linear equations with 6 degrees of freedom is obtained. To solve these equations, ODE tool of MATLAB software and Rung-Kuta numerical method is used and pipe wall radial displacement is obtained. For verification of this theory, acoustic emission test with continues leak source has been done. Vibration of wall pipe was recorded by using acoustic emission sensors. For better analysis, Fast Fourier Transform (FFT) was taken from theoretical and experimental results. By comparing the results, it is found that the range of frequencies which carried the most amount of energy is same which expresses the affectivity of the model.

Abstract: Superalloy is an alloy that has been developed to be used in processes with high thermal and mechanical stresses and also preserving high surface stabilities. Because of the increase in temperature and wearing of tool tip (even in low cutting speeds), machining of these materials has not developed considerably. Increase in demand for machining of these materials equally increases the need for investigating their manufacturing methods. For this reason, optimal machining of superalloys is very important and is under great investigations. The most important parameter for manufacturing companies is surface roughness. In the present paper, surface roughness of Udimet500 superalloy which is a nickel-based superalloy is investigated. Based on regression analysis, the most influential parameters to surface roughness are obtained and a relation for the roughness with respect to depth of cut, cutting speed, feed rate and lubricant type (CO₂, Z1 or dry) is derived.

Abstract: Among most used materials in implantology and the manufacture of surgical instruments, one finds the austenitic stainless steel AISI 316L, considered for its well adapted mechanical characteristics, its biocompatibility and in particular its resistance to uniform corrosion. The implants are often subjected to cyclic mechanical loads during normal activity of the human body, but they can also be attacked chemically by the physiological medium, under certain conditions. Between several mechanical and chemical parameters that can influence the corrosion-fatigue behavior of such material, the load frequency parameter is highlighted in this work. The aim is to determinate the effect of load frequency changes on the crack growth rate in corrosion-fatigue and to compare this effect in pure fatigue. To make experimental evidences, notched austenitic steel specimens have been submitted to cyclic bending tests inside a chlorine solution simulating the physiological medium (NaCl 0.9%). The bending stress value was taken equal to 200 MPa with a stress ratio R of 0, at different stress frequency values, respectively of 0.5, 1 and 2 Hz. When immersed in the chemical medium, the mechanical behavior of the steel sheets appears to be worst as the frequency decreases, as long as the crack size remains less than the critical one. In pure fatigue, the mechanical behavior changes with the increase of frequency and becomes detrimental. This corroborates different author works for such material.

Abstract: Nowadays plastic materials recycling aims most of the time to use the recycled material to manufacture products of less requirements than the original products, so the material is depreciated. It would be important to recycle plastic materials to use them for the same applications they were initially used. To make this possible it would be necessary to characterize the recycled material properties, design products taking into account that they are going to be produced with recycled material and to be able to recuperate the product at the end of its lifetime. An example of this designing philosophy is going to be presented in this work, applied to large trash containers produced with HDPE (RIGIDEX5740UA), where the product can be easily recovered at the end of its lifetime and also the amount of polymer material wasted during thermoplastic injection moulding is very high. Recycling mills convert parts into small pieces that are used as feed material for injection again, by mixing it in different percentages with raw material. This mixture of both raw and recycled material modifies material properties according to the percentage of recycled material introduced. Some of the properties affected by this modification are those related to mechanical behaviour. This paper analyzes the mechanical behaviour of material with different percentages of recycled material. Test parts have been injected with different percentage of recycled material and have been tested by a tensile machine. Results like; Stress at yield, Stress at break and Young Modulus have been calculated and analysed. The product of this work has been designed using only one plastic material, which is very helpful from the point of view of manufacturing and recycling. In these kinds of parts a very tight safety factor is used, thats why to know exactly material properties is very important during its design.

Abstract: Different techniques have been developed in the area of bearing wear monitoring. This paper proposes a different experimental study on bearing wear monitoring by using an airborne technique. The data captured in the airborne technique will be analyzed by using I-kaz^TM Multi Level (⁷Z) coefficient and then will be correlated with the conventional specific wear rates, K. The wear tests were carried out by using a pin-on-disc configuration at a sliding speed of 7.85 m/s. A set of sliding distance ranging from 20 160 km at a fixed load of 200 N was utilized and the K value was measured at every interval of 20 km for the speed. SAE40 type lubricant was used in the test to simulate the actual operation of the connecting rod bearing. The audio range frequency below 20 kHz in the airborne technique was obtained through a microphone 40SC type which was placed 10 mm from the pin-disc contact. The analysis result showed that the wear rate, K increased from 1.82 to 6.70x10^-8 mm³/Nm as the sliding distance increased, indicating that a mild-abrasion wear regime had occurred. The curve fitting of K as a function of I-kaz^TM Multi Level coefficient showed a similarity to an established of Taylor Tool Life curve. Thus, it was possible to correlate the Taylor curve and worn bearing, mainly in monitoring and identifying the bearing condition with respect to the sliding distance. The trend of I-kaz^TM Multi Level coefficient was found to be consistent with the increase of sliding distance which indicates that the I-kaz^TM Multi Level value can positively be used as wear response indicator for bearing.

Abstract: Resource allocation, product batching and production scheduling are three different problems in manufacturing systems of different structures such as flexible flow shop manufacturing systems. These problems are usually dealt with independently for a certain objective function related to production efficiency and effectiveness. Handling all of them in an integrated manner is a challenge facing many manufacturing systems in practice and that challenge increases for highly complicated and stochastic systems. Random arrival of products, machine setup time requirements, unexpected machine breakdowns, and multiple conflicting objective functions are some of the common complications in such systems. This research attempts to study the integrated problem under the mentioned complications with various objective functions. The decisions parameters are the batch size, the number of machines at each workstation, and the dispatching policy. Discrete event simulation is used as an optimization tools. The system is modeled using the ARENA software and different scenarios are tested for optimum parameter selection under different conditions.