Advanced Materials Research Vol. 498

Abstract: Behavior of austenitic stainless steels is not well known and these materials are still considered as difficult to machining materials. Moreover, the continuous increment of cutting speeds and other cutting parameters derived from last technological advances in tool material makes it more difficult to understand the behavior of these materials in high performance machining. A mechanistic model is presented in this paper for cutting force prediction of austenitic stainless steels turned at very high cutting speeds (up to 750 m/min). The developed model allows the estimation of cutting forces in turning when the cutting action occurs on the side cutting edge and nose radius edge for general turning tools. A tool-part geometrical model is proposed and the cutting force coefficients have been calculated by means of characterization tests.

Abstract: ECAE process is a novel technology which allows us to obtain materials of sub-micrometric and/or nanometric grain size as a result of accumulating very high levels of plastic deformation in the presence of high hydrostatic pressure. This avoids the material being fractured and permits very high values of plastic deformation to be obtained (ε>>1). Therefore, these nanostructured materials can be used as starting materials for other manufacturing processes such as: extrusion, rolling and forging among others; with the advantage of providing nanostructure and hence improving the mechanical properties. In this present study, forging by finite element of materials that have been previously predeformed by ECAE is analysed. MSC.Marc^TM software will be employed with the aim of analysing the possibility of manufacturing mechanical components (spur gears) from materials nanostructured by ECAE.

Abstract: TRIP steels, or Transformed Induced Plasticity steels, have excellent mechanical properties if compared with conventional steels. The highlighted characteristic of these steels is that they modify the microstructure with the deformation process as part of the austenite transforms to martensite, with the consequent change of the material properties. One of the main problems of TRIP steels is strong elastic recovery, or springback, after forming. In this work, the springback phenomenon is evaluated by bending tests and the influence of the variables involved in it is determined. Experimental bending forces do not agree with theoretical predictions that are proposed in the literature. In spite of the bending radius having been considered an influence factor in the process, this work demonstrates that the aforementioned factor has a minor influence, at least for TRIP 800. The factor found to affect material recovery the most was the bending angle.

Abstract: Generally, metal structural elements of aircraft are placed in zones of critical load; in most cases, these elements are manufactured by machining processes. The fatigue life of these components is an important dynamic property that may be strongly affected by the surface condition produced during machining. In this paper a preliminary study of the influence of cutting parameters on fatigue strength of parts machined in aeronautical aluminum alloy UNS A92024-T351 has been carried out. Special attention has been provided to the relationship with surface finish evaluated through the roughness average.

Abstract: In the aeronautical and aerospace industries there is a great demand of materials with high resistance and low weight such as the aluminium alloys for the production of different elements that conforms the airships and aerospace vehicles. In this work, an experimental study was carried out in order to analyse the influence of the cutting parameters (feed rate, cutting speed and type of tool) on the forces generated during dry turning tests of UNS A92024-T3 aluminium bars. The main influents factors on the forces were the feed rate and the interaction between type of tool and the spindle speed.

Abstract: The scope of this work is to study a forging process at room temperature and at macroscopic level. The mechanism of deformation is influenced by the friction and the reduction ratio, but the influence of the geometry of the billet (aspect ratio) needs also to be taken into account. The objective will be to compare the results obtained during a simulation with the code based on Finite Element Method (DEFORM 2D/3D), with those obtained by analytical methods in order to validate the numerical model. Taking into account that deformation is not uniform and the free surface suffers a phenomenon known as barrel-shaped, that is not covered by analytical methods, the data obtained will compared with those obtained with the FEM code ABAQUS. The aim of this comparison between analytical and numerical methods using two commercial codes instead one, is a proposed way to validate a Finite Element simulation when experimental data are not available or do not exist yet.

Abstract: The application of laser beam welding to aluminium alloys has some complications, mainly due to their high reflectivity, high thermal conductivity and low viscosity. In order to increase the laser absorption of aluminium alloys, some surface treatments has been applied in the literature, such as the application of dark coatings or sandblasting. However, these conventional superficial treatments have some drawbacks, such as the low weld penetration, the possibility to undergo magnesium evaporation and the impossibility to control and/or change the superficial properties of the treated samples. In the present contribution, laser texturization treatments have been performed with a fibber laser for the first time on aluminium alloys to increase their absorption and weld penetration. The texturised samples leaded to deeper bead welds than the reference sandblasted samples.

Abstract: The present work shows the first results of the study methodology of the process parameters applied to drilling of composites reinforced with carbon fiber (CFRP) used in the aeronautical industry. The analysis uses both cutting forces and temperatures achieved in the cutting process, although it has focused on the application of IR thermography to the study of the hole. The study of the defects that can be found on the workpiece, associated with these processes (delamination), is approached by using both optical microscopy and SEM.

Abstract: The current requirements for an efficient dimensional inspection of manufactured parts have lead to development of different in process and on-machine measurement (OMM) techniques. Touch trigger probes (TTP) are the most common technologies utilized, inspired on contact probes used on coordinate measuring machines (CMMs). The on-machine accuracy of TTPs depends upon precision of the tool-machine control as well as upon the procedure for TTP presetting. Taking this into account, a different OMM technique is considered in this work, which consists on a laser micrometer (LM) that is commonly used for in-process measurement of continuous products. The behaviour of TTP and LM is analysed and discussed in terms of repeatability and reproducibility. Results obtained by both techniques are compared each other by measuring a cylindrical workpiece and by checking the results with those obtained on a CMM.