Materials Science Forum Vol. 713

Abstract: Electropolishing is a surface finishing process of metals and alloys that enhances brilliant surface finishes with low surface roughness values. The most widely used electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface finish of electropolished stainless steel AISI 316L. Each electrolyte had varying sulphuric-phosphoric acid combinations with or without chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, and initial surface texture. The results revealed that adding chromic acid to the electrolyte did not significantly enhance surface finish, and electropolishing ranges were quite similar for all three electrolytes.

Abstract: Technology of Rapid Prototyping (RP) presents the technique that leads to quick manufacturing of real model using the scaling with support of three-dimensional software solution running in computer environment (CAD). First RP technique, Stereolithography, was developed by 3D Systems of Valencia, CA, USA. The company was founded in 1986, and since then, a number of different RP techniques have become available. Article deals with basic characteristics and problems in area of technology of Rapid Prototyping with focus to Fused Deposition Modeling. It brings in the project of experimental gearbox design and its manufacturing with application of Rapid Prototyping technology. The work was realized by students and employees of Faculty of Manufacturing Technologies in Presov, Slovakia. Model with four gears was realized together with its gear changing mechanism. Production of gearbox was connected with problems arising from size of individual parts and included also the realization of final gearbox assembly.

Abstract: This paper reports the characterization of laser machining (milling) process to manufacture micro-channels in order to understand the incidence of process parameters on the final features. Selection of process operational parameters is highly critical for successful laser micromachining. A set of designed experiments is carried out in a pulsed Nd:YAG laser system using AISI H13 hardened tool steel as work material. Several micro-channels have been manufactured as micro-mold cavities varying different process parameter. Results are obtained by evaluating the dimensions and the surface finish of the micro-channel. The dimensions and shape of the micro-channels produced with laser-micro-milling process exhibit variations. In general the use of low scanning speeds increases the quality of the feature in both surface finishing and dimensional.

Abstract: This paper presents a numerical analysis of the influence on the fatigue life of hybrid metal/CFRP bolted joints of some deviations in certain assembly parameters. Two types of hybrid joints typically used in aircraft are analyzed, the Ti-6Al-4V/CFRP and the Al-2024-T3/CFRP, riveted with blind bolts. The parameters analyzed are: the thickness of sealant between metal sheet and composite laminate, the angle of countersunk and the adjustment or chamfer at the countersunk-drill zone. The analysis highlights critical areas for fatigue failure and the relative influence of these parameters on the fatigue resistance of the joint.

Abstract: Recent studies have shown that Severe Plastic Deformation (SPD) processes improve the mechanical properties of the parts processed, through a reduction in the grain size. Equal Channel Angular Extrusion (ECAE) is one of the best -known SPD processes. A study was made of the force and the strain after two ECAE passages, as well as of the damage imparted to AA-6082, by means of experiments and Finite Element Simulations (FEM). The aim of this present research is to make a comparative study between experimental results and those obtained by FEM in order to verify the feasibility of these FEM simulations. In addition to this, it is intended to analyze the homogeneity obtained in the strain values after two ECAE passages made through route C.

Abstract: The laser cladding process is based on the generation of a melt-pool in a substrate where a filler material is injected, generating a high quality clad with a minimum heat affected zone. This process is industrially used to generate coatings over wear or damaged surfaces, being an alternative to traditional deposition techniques. One of the most important aspects for its industrial application is to know the clad geometry in order to calculate the deposited layer thickness. This work presents a model in which, starting from the concentration of injected material and the melt-pool geometry, clad height is finally estimated. Both input variables are obtained by two previous validated models. On one hand, the melt pool is estimated by a thermal model based on the finite difference method, and on the other hand, concentration of injected material is provided by a particle concentration CFD model. This data is used in a mass balance over melt-pool area in order to estimate the deposited clad height.

Abstract: The Abrasive Water Jet milling process is demonstrated to be an efficient technology for milling low machinability materials. Although its capability is demonstrated, the industrial application of this technology requires a depth control, for which a work focused in process modelling is needed. This research work introduces a model to predict the kerf shape in AWJ slot milling in Aluminium 7075-T651 in terms of four important process parameters: pressure, abrasive mass flow rate, stand-off distance and traverse feed rate. A hybrid evolutionary approach was employed for modelling the profile through two parameters: the maximum cutting depth and the full width at half maximum. Both the maximum depth and the width were also modelled as a function of aforementioned process parameters based on Analysis of Variance and regression techniques. Combination of two models resulted in an adequate strategy to predict the kerf shape for different machining conditions.

Abstract: The process of Wire Electrical Discharge Machining (WEDM) has experienced a dramatic growth in the last years. Together with the new requirements imposed by customer needs, globalization of the markets has brought about a new scenario in which competitiveness is the keyword. In the case of WEDM, it is only possible from a perspective that integrates developments in hardware, software and know-how, to generate the required added-value with respect to competitors. For instance, it is not enough to give an answer to the demand of a high-speed first cut: economy must be achieved together with a high accuracy and using low-cost wires. In this paper the research actions currently running aiming at the development of a new generation of WEDM machines are presented. The objective of this paper is to present an integrated research approach focused on industrial needs, covering the following aspects: Accuracy and productivity; automation and machine intelligence; eco-efficiency.

Abstract: In this paper, the evolution of plastic strain and hydrostatic pressure evolutions in incremental sheet forming (ISF) processes to postpone fracture of the metal sheet is analyzed. A finite element (FE) model of an incremental forming operation and a conventional stretch-bending operation is performed. Experimental results of stretching tests are used as reference. The local evolution of the straining and the distribution of hydrostatic pressure are studied in detail. Different step downs and friction coefficients are simulated and their results are discussed.

Abstract: In recent years laser polishing is becoming an alternative for automated surface finishing of dies and molds. This process involves melting and subsequent solidification of the material. Depending on the initial topography, the energy density necessary to reduce surface asperities can cause excessive heat damage, and thus, limit the applicability of the process. The work presented here focuses on the use of a high quality laser beam, with a spot diameter below 50 microns driven by a 2D scanner for processing of materials typically used in dies and mold manufacturing. So, the highly focused beam ensures minimal thermal damage, and the scan head allows high productivity rates. A new processing strategy based on two stages surface processing was developed to process topographies with strong directionality.