Advanced Materials Research Vol. 1036

Abstract: Failure mode and effect analysis (FMEA) is one of the well-known techniques of quality management that is used for continuous improvement in product or process design. It is widely used in manufacturing industries in different stages of the product life cycle and is now increasingly finding use in the service industry. Even through this approach is simple but there are some limitations in obtaining a good estimate of the failure ratings. Thus, a new risk assessment system based on the fuzzy set theory and fuzzy rule base theory is proposed in this study to solve these problems that have arisen from conventional FMEA. Furthermore, an analysis is presented to demonstrate the traditional FMEA. We present of a parallel between the typical and the fuzzy computation of RPNs, in order to assess and rank risks associated to failure modes that could appear in the laser cutting process. This work can also serves as a failure prevention guide those who perform the laser cutting operation.

Abstract: In this paper we present a study of issues related for determination the real profile and the theoretical one of the precessional gear wheels. In the research process of the precessional gears profile appeared the problem of finding the geometrical error between fabricated profile and the ideal one after grinding process. The cause of the errors has technological and constructive nature. Processing technology of these specific gear wheels is one that still has many unknowns, therefore will be researched the part that is related to the occurrence of deviations from the ideal profile. The manufacturing of processing device and its elements also lead to geometric deviation of the profile, which will lead to adverse effects during operation. Measurement of manufactured profile using special equipment would involve high costs of time and money, therefore will be used computational methods and the statistic-mathematical method. The computational method is to find a better methodology to transform a file obtained from 3D scan (precessional gear wheel), which can be used only as a copy, into a file with functional extension. Such a conversion is very important to make especially for objects with complicated geometry such as precessional wheel profile. Transformation will result in surfaces and geometric objects that can be manipulated and compared to each other, with the aim of find deviations between ideal 3D models and the real ones. The methodology is relative simple: the triangular surfaces which form the shell of object should be approximated by flat, cylindrical, conical, etc. surfaces interlinked and filling the empty space between them with material. Once the scanned real object is transformed into a functional virtual file, it can not only be compared with the ideal model but also modified at the discretion of the user. Also we can find the coordinates of points which form the wheel contour line, which can be analyze and interpolate to obtain a mean value of scanned profile. Following the analysis of a profile obtaining was observed a small error of inclination of the gear teeth, due to the technological process. This methodology can be used to finding geometric errors also for other objects, gears etc.

Abstract: In this paper will be treated the problem of strains and stresses within the connections and elements from the grinding technological system. These system deformations can lead to positive or negative effects. Main negative effects will be occurrence of processing errors on the part profile, but also the excessive tension from system elements. Cause of processing errors and the low safety due of the system rigidity must be sought in its joints between parts, stiffness of moving pieces, low number and reduced rigidity of parts used to assembling (bolts, cotter joints, pins). Elastic properties of the assembly are modeled by the inserted connections with specific characteristics. The elastic deformation of the work piece must be taken into account, besides the elastic behavior of the device which appears in manufacturing process. A very important aspect in the study of elastic behavior of the whole system is how the abrasive tool interacts with the work piece, namely the displacement of contact zone. Contact stresses lead to a deformation of the grinding wheel and the work piece, and as a result the work piece loses from precision of tooth profile. The rigidity of system can be characterized by two aspects, one static and one dynamic and we will describe both aspects using CAE simulations and classical mathematical models. It will be presented some results of numerical simulation of the stiffness of gear grinding system using finite element method (FEM). The elastic dynamic model was design using the forces of inertia and gravity that occurs during grinding process. Also by permanent pursuing of the technological forces variation during the grinding process will be sought the dynamic deformation of the system. The study its concentrated around the low stiffness of components inside the system, in order to find errors that may affect the precision on the horizontal, vertical and rotational direction of technological system elements. Since through this analysis it tried to find how the forces influence on the ETS stiffness, it will present numerical values of the system displacements and stress distribution. Knowing the direction, sense and numerical values of these errors can be made interpretation of the results, namely the removal of these consequences.

Abstract: The economic context and the current guidelines of research and achievement of complex profiles are focussed on choosing that process which leads to obtaining high quality pieces with minimum costs. Circular grooves are complex surfaces often encountered on pieces in machine construction. They can be processed either by cutting or by cold plastic deformation. This paper presents by comparison a series of characteristics of a circular profile obtained by two different processes: profiled turning with radial feed and cold rolling with two wedge tools. The characteristics analysed refer to the roughness of the profile obtained, the microstructure and micro-hardness of the superficial layer generated. In the experiments two types of materials with different compositions and properties were used: cementing steel AISI 1015 and improving steel AISI 5140, usually used for the construction of pieces with circular grooves. Processing by rolling was performed with two types of wedges: with a long area of deformation and low slope angle and with a short area of deformation and high slope angle. The results of the study allow establishing the conditions to apply each one of the two processes analysed, highlighting their advantages and disadvantages, as it results from the comparison of the characteristics of the profile obtained.

Abstract: An important problem in obtaining mini drawn parts with high precision is represented by the blank geometry. Utilization of a blank with optimal shape and dimensions leads to the following benefits: improves the accuracy of the drawn parts and determine the costs reduction due to reduced material consumption and cost, lower number of technologic operations, shorter manufacturing times etc. An adequate blank prevents the following effects on drawn part: avoids the part fracture, conducts to a uniform distribution of the material thickness in drawn part and reduces the blank holder force required by the drawing process. The present paper analyses the results of investigations made by simulation and experiment concerning the establishment of the optimal blank diameter in the case of mini cylindrical drawn parts made from aluminium sheets. The optimal blank diameter was determined by applying the Fuzzy Logic and Taguchi methods.

Abstract: The mini deep drawing is a cold forming process applied in order to realize small parts having dimensions smaller than 20 mm. In the case of such process the small thickness of sheet and the small dimensions of parts are the most important factors that influence the process parameters and can affect the accuracy and quality of the produced mini - parts. A proper clearance between the working tools components is also a very important factor that can permit to obtain mini drawn parts in accordance with their theoretical profile. The present paper analyses the results of investigations made by experiment and simulation concerning the influence of tool clearances values on the accuracy of dimensions in the case of mini scale cylindrical drawn cups made from thin sheets. The deviations from the cups theoretical profile (wall inclination, variation of part diameter) that can occur during deep drawing of such sheets were especially analyzed in the paper.

Abstract: The design and manufacturing of complex shaped 3D features have a wide range of applications in todays manufacturing industries. With machining of hard materials continues to attract much interest in this field, EDM remains an indispensable process to carry out this purpose despite its limitations compared to conventional machining processes in terms of material removal rate and surface quality. Many process improvement techniques have been reported by researchers to overcome these limitations and out of them, incorporation of tool electrode kinematics is observed to have a significant effect. In the present investigation, an attempt has been made to study the effectiveness of two different tool motions in the generation of non-circular cavities. Tool electrode is moved on planetary and diagonal paths during this study. Effects of various electrical and non-electrical parameters on EDM responses have been studied. Current, pulse ON time and voltage are considered as the electrical parameters while tool kinematics parameters like tool path offset and scanning speed have been selected as the non-electrical parameters. Experiments have been carried out the study the effect of tool movement on planetary and diagonal path on different response characteristics viz. Material removal rateand Wear Ratio. It has been observed that planetary motion is a better strategy than diagonal motion for the generation of non-circular cavities in terms of achievement of the response characteristics. The results observed are critically discussed.

Abstract: The heat conditions of laser gas nitriding (LGN) of titanium alloy Ti6Al4V by high power diode laser (HPDL) were investigated experimentally by non-contact pyrometric measurements and infrared camera analysis. Additionally direct observations of the weld pool shape were conducted by means of high speed digital camera. In the numerical study of the laser surface processing of titanium plate 3D model of heat flow was examined. Results of temperature values, distribution and temperature isotherms obtained from the 3D model were next applied in the two-dimensional stationary model of liquid metal flow in the weld pool. Experimental and numerical study showed that the temperatures of the weld pool during laser gas nitriding of the titanium alloy are significantly higher compared to these determined during laser melting in argon atmosphere at the same heat input. Additionally severe turbulences of liquid metal in the weld poll (Marangoni convection) were found during both experimental and numerical analysis.

Abstract: In this work it was performed a fluid mechanical study of cooling systems for metal cutting. In these machine tools are developed temperatures processing this should be minimized so as not to damage of the tool durability. Therefore should correlate pressures, temperatures and fluid flows used. Also the physical characteristics of fluids used are important for better cooling of the tool in the work area. All these factors lead to a better surface of machined area.

Abstract: In this study, a high power direct diode laser (HPDDL), with a rectangular laser beam spot, was used for conduction mode welding of Inconel 625 sheets (0.8 mm thick). The influence of laser butt welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The minimum heat input required to achieve full penetration butt welded joints was found to be 60 J/mm. The joints exhibited comparable yield and about 15 % lower ultimate tensile strength when compared with that of the base metal.