Abstract: This work presents a methodology to improve the final thickness distribution of
thermoformed parts. The conventional plug is replaced by a new version containing concentric
layers with independent displacements. The results show that thickness gradients can be
significantly reduced, with a simultaneous increase of the minimum values. Varying the relative
displacement of the inner layers can bring about significant differences in the final thickness
distribution, thus enabling the production of parts with prescribed thickness profiles that maximise
their mechanical performance.
Abstract: Depth sensing indentation equipment allows the mechanical properties of thin films to be
easily determined, particularly the hardness and Young’s modulus. In order to minimize the
influence of the substrate on the measured properties, the indentation depth must be limited to a
small fraction of the film’s thickness. However, for very thin films, the determination of the
contribution of the substrate and the film to the measured mechanical properties becomes a hard
task, because both deform plastically. The numerical simulation of ultramicrohardness tests can be a
helpful tool towards better understanding of the influence of the parameters involved in the
mechanical characterization of thin films. For this purpose, a three-dimensional numerical
simulation home code, HAFILM, was used to simulate ultramicrohardness tests on coated
substrates. Materials with different Young’s modulus film/substrate ratios were tested. Analyses of
strain and stress distributions for several indentation depth values were performed, in order to
clarify the composite behaviour.
Abstract: Microporosity is the major processing defect in pressure die cast AZ91 magnesium alloy.
There is a big difference in the arrangement of pores in different regions of the castings. The present
work explains the pore arrangement in pore bands and other regions. Quantification and
characterization of pores in pore bands is expected to be useful to understand the process-propertymicrostructure
correlation. A computational microstructural (image) analyzing technique has been
developed by a programming language to quantify and analyze the micropores in pore bands. The
pore band regions and the rest were separated and quantified. In addition, image analyzing
technique was used to measure the clustering tendency of porosity in pore bands and it was
compared with other regions.
Abstract: A model based on steric hindrance mechanisms  is used to determine the pore sizes of two
ultrafiltration (UF) membranes. The lysozyme rejection coefficients of those membranes are
predicted through the same model after modification of the pore size and solute radius by taking
into account the development of electric double layers. Two asymmetric cellulose acetate
membranes M1 and M2 were prepared and characterized. Membrane M1 has an hydraulic
permeability of 2.1x10-6 m/s/bar, a molecular weight cut-off (MWCO) of 30,000 Da and an average
pore radius of 2.6 nm. Membrane M2 has an hydraulic permeability of 5.9x10-6 m/s/bar, a
molecular weight cut-off (MWCO) of 60,000 Da and an average pore radius of 5.3 nm. Aqueous
solutions of lysozyme containing a NaCl concentration of 0.1M were ultrafiltrated through
membranes M1 and M2. The predicted lysozyme rejections considering the development of electric
double layers on the protein and membrane pore surfaces, are in good agreement with the
Abstract: A new algorithm to determine Voronoi partitions of space using periodic boundary
conditions has been implemented in GAMGI free software package. This algorithm was used to
study the topological and geometric properties of Voronoi polyhedra obtained for Poisson and
Laguerre seeding distributions. The Random Sequential Adsorption (RSA) method was used to
generate a Laguerre seeding distribution with a volume fraction of spheres φ ≈ 0.36. The resulting
normalised cell volume distributions were compared with the gamma and lognormal density
functions using χ2 goodness of fit testing, and in both cases the gamma function provides a better
description. The Lewis and Aboav empirical relations approximately apply to both partitions, with
least square correlation factors R2 equal to 0.98 for the Lewis law and 0.95 for the Aboav law.
Abstract: In new car production, an innovative method to produce strong and light panels consists
in applying Tailor Welded Blanks (TWBs) in the body-in-white base structure. Since the fusion
welding processes can induce significant changes in the material properties of the base materials, an
important question is whether the weld bead has a significant influence on the overall behaviour of
the welded blanks. In this work, some preliminary conclusions on this subject were achieved based
on results of the numerical simulation of simple mechanical tests: tensile, shear and simple bending.
The numerical simulations were performed with a fully implicit finite element program (DD3IMP).
The results obtained show that for a slight mismatch of properties between the weld and the base
materials, no important influence of the weld in the TWBs behaviour is noticed. However, a
significant strength reduction can be observed for strong undermatch conditions (lower mechanical
properties in the weld) even when the weld bead is very narrow.
Abstract: In this study, the as-moulded shrinkage and pressure data are obtained experimentally
and compared with numerical simulations. The mouldings were produced in polypropylene (PP).
The effect of pressure on viscosity in the predicted pressure evolution was analyzed and also its
influence on the shrinkage. The results show that the rise of holding pressure determines the
reduction of the shrinkage. Also, it was observed that the pressure predictions are qualitatively in
good agreement with the experimental data. However noticeable quantitative discrepancies can be
observed when the effect of pressure on viscosity is not considered. If the effect of pressure on the
melt viscosity is considered the deviation between predicted and the experimental pressure
evolution is substantially reduced.
Abstract: The Direct Metal Laser Sintering (DMLS) technology uses a mixture of metal powders with different melting points to build objects layer by layer, directly from the geometric digitalised information. This process allows the manufacturing of prototype and production tools.
In this study, the M3/2 high speed steel powder blended with 20 wt.% Cu3P and 0.25 wt.% graphite was laser-sintered, using two scan speeds (100 and 200 mm/s), keeping constant both hatching (0.30mm between two consecutive lines) and laser power (180W). The powder was spread in uniform layers of about 20m over a steel plate (100x60x6mm). The laser beam scanned small areas (12x15mm) in a single direction (OX). The surface morphology of the laser-sintered material shows that all material melted, but for 200mm/s scan speed, strings are well defined. This is probably due to a lower level of energy supplied to the material. The microstructure of the sintered material was studied in the longitudinal and transverse sections, to evaluate the consolidation process and layer growth. The material showed porosity and cracks formed during the process.
Abstract: The corrosion resistance under mechanical stress can be one of the most concerning types
of localized corrosion for the application of stainless steel reinforcements in concrete. This paper
will assess the stress corrosion cracking susceptibility, by the slow strain rate test method (SSRT),
of three austenitic stainless steel alloys: one conventional Fe-Cr-Ni base alloy and two new
composition Fe-Cr-Mn base alloys adequate to the manufacturing of ribbed bars for reinforcing
concrete. The SSRT results show that only one of the austenitic Fe-Cr-Mn alloys is susceptible to
stress corrosion cracking while the other shows a performance similar to that of the AISI 304
stainless steel alloy.
Abstract: The market is changing very quickly, demanding the companies the capability of
producing better and/or more performing products. This changing market leads the companies to be
more flexible and agile. In particular, for the tool makers and the stamping companies, they are
requested to participate in the design phase of the product and process, as well as to produce
prototypes and small series in very short time and with low costs.
To answer to these demands in the stamping steps design and consequently in the tool design,
several finite elements packages are widely used, allowing the tool designers to foresee the results
of their options/decisions without the need to manufacture and test tools, with the inherent
excessive cost of money and time. Following this methodology, CAE analysis, the final phase of
tool try out, always necessary, will be certainly shorter and less expensive, once they start with a
solution quite more worked and, for sure, closer to the final solution.
In this industrial context, appeared the great motivation for the development of competences on the
rapid manufacturing of stamping tools (active elements: punch, die and blankholder), on the
numerical simulation of the process and, on the development of the modular tool concept.
In this paper the main results of the development of these areas of research, are presented. In
particular, the use of the numerical simulation, using PAM-STAMP 2G software, for the validation
of the stamping phases, the realisation of laboratorial stamping tests using tools produced by the
several techniques available on Portugal for rapid prototyping. At the same time, it was developed
the modular tool concept, i.e., a tool in which by fast and easy change of the active elements,
different parts can be formed. The active elements of the tool have been manufactured by several
rapid tooling techniques, like DMLS - Direct Metal Laser Sintering, LOM - Laminate Object
Manufacturing, HSM – High Speed Milling and also the machining of non-traditional materials
such as nylon, ureol and aluminium. Some inserts have been produced by indirect techniques such
as reinforced resins (polyurethane, epoxy and urethane) using shells produced by SLstereolithography.
Finally some conclusions are drawn.