Advanced Materials Research Vol. 498

Abstract: Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.

Abstract: This paper firstly introduces the principle and characteristic of traditional extrusion tapping of internal thread, elaborates the material flow law during tapping process. Then puts forward a novel process of vibration-assisted extrusion tapping of internal thread, explains the effect mechanism of vibration during extrusion tapping of internal thread. Finally, with the finite element method (FEM), the simplified model of extrusion tapping are built, and the simulation of thread forming process of traditional extrusion tapping of internal thread are conducted, furthermore, the characteristic and influencing law of different vibration parameters (include vibration frequency, amplitude and direction) of vibration-assisted extrusion tapping of internal thread are studied, and some practical results are obtained. The simulation results show that applying vibration to extrusion tapping of internal thread can reduce tapping torque and improve thread forming quality, the reasonable selection of vibration parameters are very crucial to this novel process.

Abstract: The work here exposed, is framed in the line of development of slight materials with good properties, used to reduction of weight in different components for the aviation and automotion where very high temperatures are the main factor. In these fields, several components must withstand high temperatures maintaining a high resistance. The superalloys of type Gamma TiAl is a attractive alternative to other titanium and nickel-based alloys, due to high relationship resistance/weigh and the resistance to the corrosion. This work presents the results from turning tests on three types of Gamma TiAl alloys. Coating tools of integral hard metal are used, with different advances and cut speeds.

Abstract: In this paper, we have developed a physical model to predict the forces of the ball burnishing. The models have been constructed on the basis of the plasticity theory. During the model development we have Fig.d out the dimensionless number B that characterizes the problem of plastic deformation in the ball-burnishing. The experiments performed in steel and aluminum allows to validate the model and to emphasize the correct prediction of behavior patterns that the model describes.

Abstract: An acrylic epoxidized soybean oil (AESO) has been used in this study. The synthesis of the acrylic resin has been made from acrylic acid which breaks the epoxy groups of the ESO (epoxidized soybean oil). This material can be obtained thermosetting polymers suitable for use as a matrix in "green composites. The aim of this work is to develop some AESO-styrene mixtures in order to evaluate the influence of the AESO-styrene ratio in the curing process and also it is desired to obtain the resins characteristics.

Abstract: Time to market is a critical measurement for todays foundry market. Combining 3D digitizing and sand blocks milling is possible to reduce this time. Avoiding the use of a wood pattern, this technique is useful for art pieces or unique parts, when only one component is necessary. The key of the proposed methodology is to achieve enough tool life with conventional tool qualities, avoiding the risk of sand destruction or damage. A special study of tool wear is presented in this work, studying different tool materials and different sand types. Two examples of unique parts are also presented in this work following the proposed methodology in order to reduce time and cost for the rapid reproduction of very short batches.

Abstract: Current trends in machining processes are focused in three goals: to increase the productivity and the reliability and to minimize costs. In this context, the development of signal monitoring systems is of vital importance for surface roughness inspection. One of the research lines associated to this context is oriented to predict surface roughness using indirect signal analysis, such as cutting forces or vibrations in the machining process. This paper analyzes the results obtained when comparing different nature signals combined with cutting parameters. The final goal is to quantify the deviations obtained with different monitoring signals for establishing the best ones to use as roughness evaluators. The best predictions were obtained when force and cutting conditions were combined together. The absolute error values remains always below 1.28 and 1.11 µm when using the median and root mean square (RMS) as descriptors, respectively.

Abstract: Magnesium is the lightest metal used in industry, above all for aerospace and automotive applications where weight reduction allows an improvement in the fuel efficiency and reducing CO² emission. In this work, an experimental study was carried out in order to determine with which machining process, turning or milling, are obtained cylindrical bars of magnesium alloy UNS M11917 by intermittent dry cut with improved roundness and cylindricity finish.

Abstract: Heat-resistant alloys like Inconel 718 are used in critical components such as aircraft engine turbine discs. Due to the extreme thermo-mechanical solicitations that must suffer during their lifetime, reliability is essential, even more if its failure could lead to loss of human lives. Surface integrity is a critical issue in this kind of components and especially residual stresses are a key aspect. Currently, the development and optimization of the machining process with regards to the residual stresses is done through expensive experimental trial and error methods. This article shows the research work made on the simulation of a machining model in three dimensions with the Deform^TM commercial program. The results obtained show the influence of contact parameters (friction coefficient, heat transfer coefficient) not only on the cutting forces and temperatures, but also in the generation of residual stresses.

Abstract: An accurate prediction of the dynamic stability of a cutting system involves the implementation of tool geometry and cutting conditions on any model used for such purpose. This study presents a dynamic cutting force model based on the collocation method by Chebyshev polynomials taking advantage from its ability to consider tool geometry and cutting parameters. In the paper, a simple 1DOF model is used to forecast chatter vibrations due to the workpiece and tool, which are distinguished in separate sections. The proposed model is verified positively against experimental dynamic tests.