Abstract: The secondary alloy A226 is used for many
automotive casting produced by mould casting and high pressure die
casting. This alloy has excellent castability, good mechanical
properties and cost-effectiveness. Production of primary aluminium
alloys belong to heavy source fouling of life environs. The European
Union calls for the emission reduction and reduction in energy
consumption therefore increase production of recycled (secondary)
aluminium cast alloys. The contribution is deal with influence of
recycling on the quality of the casting made from A226 in automotive
industry. The properties of the casting made from secondary
aluminium alloys were compared with the required properties of
primary aluminium alloys. The effect of recycling on microstructure
was observed using combination different analytical techniques (light
microscopy upon black-white etching, scanning electron microscopy
- SEM upon deep etching and energy dispersive X-ray analysis -
EDX). These techniques were used for the identification of the
various structure parameters, which was used to compare secondary
alloy microstructure with primary alloy microstructure.
Abstract: The present study was carried out to investigate the
effect of alloying elements and thermo-mechanical treatment (TMT)
i.e. hot rolling and forging with different reduction ratios on the
hardness (HV) and impact toughness (J) of heat-treated low alloy
steels. An understanding of the combined effect of TMT and alloying
elements and by measuring hardness, impact toughness, resulting
from different heat treatment following TMT of the low alloy steels,
it is possible to determine which conditions yielded optimum
mechanical properties and high strength to weight ratio.
Experimental Correlations between hot work reduction ratio,
hardness and impact toughness for thermo-mechanically heat treated
low alloy steels are analyzed quantitatively, and both regression and
mathematical hardness and impact toughness models are developed.
Abstract: A chromium-loaded ash originating from incineration of tannery sludge under anoxic conditions was mixed with low grade soda-lime glass powder coming from commercial glass bottles. The relative weight proportions of ash over glass powder tested were 30/70, 40/60 and 50/50. The solid mixtures, formed in green state compacts, were sintered at the temperature range of 800o C up to 1200o C. The resulting products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDXS) and micro-indentation. The above methods were employed to characterize the various phases, microstructure and hardness of the produced materials. Thermal treatment at 800o C and 1000o C produced opaque ceramic products composed of a variety of chromium-containing and chromium-free crystalline phases. Thermal treatment at 1200o C gave rise to composite products, where only chromium-containing crystalline phases were detected. Hardness results suggest that specific products are serious candidates for structural applications.
Abstract: In this research the effect of moisture at three levels
(47, 57, and 67 w.b.%) on the physical properties of the Pofaki pea
variety including, dimensions, geometric mean diameter, volume,
sphericity index and the surface area was determined. The influence
of different moisture levels (47, 57 and 67 w.b.%), in two loading
orientation (longitudinal and transverse) and three loading speed (4,6
and 8 mm min-1) on the mechanical properties of pea such as
maximum deformation, rupture force, rupture energy, toughness and
the power to break the pea was investigated. It was observed in the
physical properties that moisture changes were affective at 1% on,
dimensions, geometric mean diameter, volume, sphericity index and
the surface area. It was observed in the mechanical properties that
moisture changes were effective at 1% on, maximum deformation,
rupture force, rupture energy, toughness and the power to break.
Loading speed was effective on maximum deformation, rupture
force, rupture energy at 1% and it was effective on toughness at 5%.
Loading orientation was effective on maximum deformation, rupture
force, rupture energy, toughness at 1% and it was effective on power
at 5%. The mutual effect of speed and orientation were effective on
rupture energy at 1% and were effective on toughness at 5%
probability. The mutual effect of moisture and speed were effective
on rupture force and rupture energy at 1% and were effective on
toughness 5% probability. The mutual effect of orientation and
moisture on rupture energy and toughness were effective at 1%.
Abstract: The material selection in the design of the sandwich
structures is very crucial aspect because of the positive or negative
influences of the base materials to the mechanical properties of the
entire panel. In the literature, it was presented that the selection of the
skin and core materials plays very important role on the behavior of
the sandwich. Beside this, the use of the correct adhesive can make
the whole structure to show better mechanical results and behavior.
In the present work, the static three-point bending tests were
performed on the sandwiches having an aluminum alloy foam core,
the skins made of three different types of fabrics and two different
commercial adhesives (flexible polyurethane and toughened epoxy
based) at different values of support span distances by aiming the
analyses of their flexural performance in terms of absorbed energy,
peak force values and collapse mechanisms. The main results of the
flexural loading are: force-displacement curves obtained after the
bending tests, peak force and absorbed energy values, collapse
mechanisms and adhesion quality. The experimental results presented
that the sandwiches with epoxy based toughened adhesive and the
skins made of S-Glass Woven fabrics indicated the best adhesion
quality and mechanical properties. The sandwiches with toughened
adhesive exhibited higher peak force and energy absorption values
compared to the sandwiches with flexible adhesive. The use of these
sandwich structures can lead to a weight reduction of the transport
vehicles, providing an adequate structural strength under operating
conditions.
Abstract: There are several possibilities of reducing the required
amount of cement in concrete production. Natural zeolite is one of
the raw materials which can partly substitute Portland cement. The
effort to reduce the amount of Portland cement used in concrete
production is brings both economical as well as ecological benefits.
The paper presents the properties of concrete containing natural
zeolite as an active admixture in the concrete which partly substitutes
Portland cement. The properties discussed here bring information
about the basic mechanical properties and frost resistance of concrete
containing zeolite. The properties of concretes with the admixture of
zeolite are compared with a reference concrete with no content of
zeolite. The properties of the individual concretes are observed for
360 days.
Abstract: Problems insulation of building structures is often
closely connected with the problem of moisture remediation. In the
case of historic buildings or if only part of the redevelopment of
envelope of structures, it is not possible to apply the classical external
thermal insulation composite systems. This application is mostly
effective thermal insulation plasters with high porosity and controlled
capillary properties which assures improvement of thermal properties
construction, its diffusion openness towards the external environment
and suitable treatment capillary properties of preventing the
penetration of liquid moisture and salts thereof toward the outer
surface of the structure.
With respect to the current trend of reducing the energy
consumption of building structures and reduce the production of CO2
is necessary to develop capillary-active materials characterized by
their low density, low thermal conductivity while maintaining good
mechanical properties. The aim of researchers at the Faculty of Civil
Engineering, Brno University of Technology is the development and
study of hygrothermal behaviour of optimal materials for thermal
insulation and rehabilitation of building structures with the possible
use of alternative, less energy demanding binders in comparison with
conventional, frequently used binder, which represents cement.
The paper describes the evaluation of research activities aimed at
the development of thermal insulation and repair materials using
lightweight aggregate and alternative binders such as metakaolin and
finely ground fly ash.
Abstract: The dissimilar joint between aluminum/titanium
alloys (Al 6082 and Ti G2) were successfully achieved by CO2 laser
welding with a single pass and without filler material using the
overlap joint design. Laser welding parameters ranges combinations
were experimentally determined using Taguchi approach with the
objective of producing welded joint with acceptable welding profile
and high quality of mechanical properties. In this study a joining of
dissimilar Al 6082 / Ti G2 was resulted in three distinct regions
fusion area in the weldment. These regions are studied in terms of its
microstructural characteristics and microhardness which are directly
affecting the welding quality.
The weld metal was mainly composed of martensite alpha prime.
In two different metals in the two different sides of joint HAZ, grain
growth was detected. The microhardness of the joint distribution also
has shown microhardness increasing in the HAZ of two base metals
and a varying microhardness in fusion zone.
Abstract: Today, the pollution due to non-degradable material
such as plastics, has led to studies about the development of
environmental-friendly material. Because of biodegradability
obtained from natural sources, polylactid acid (PLA) and ijuk fiber
are interesting to modify into a composite. This material is also
expected to reduce the impact of environmental pollution. Surface
modification of ijuk fiber through alkalinization with 0.25 M NaOH
solution for 30 minutes was aimed to enhance its compatibility to
PLA, in order to improve properties of the composite such as the
mechanical properties. Alkalinization of the ijuk fibers annihilates
some surface components such as lignin, wax and hemicelloluse, so
the pore on the surface clearly appeared, decreasing of the density
and diameter of the ijuk fibers. The change of the ijuk fiber properties
leads to increase the mechanical properties of PLA composites
reinforced the ijuk fibers through strengthening of the mechanical
interlocking with the PLA matrix. An addition to enhance the
distribution of the fibers in the PLA matrix, the stirring during DCM
solvent evaporation from the mixture of the ijuk fibers and the
dissolved-PLA can reduce amount of the trapped-voids and fibers
pull-out phenomena, which can decrease the mechanical properties of
the composite.
Abstract: Micro-alloyed steel components are used in
automotive industry for the necessity to make the manufacturing
process cycles shorter when compared to conventional steel by
eliminating heat treatment cycles, so an important saving of costs and
energy can be reached by reducing the number of operations. Microalloying
elements like vanadium, niobium or titanium have been
added to medium carbon steels to achieve grain refinement with or
without precipitation strengthening along with uniform
microstructure throughout the matrix. Present study reports the
applicability of medium carbon vanadium micro-alloyed steel in hot
forging. Forgeability has been determined with respect to different
cooling rates, after forging in a hydraulic press at 50% diameter
reduction in temperature range of 900-11000C. Final microstructures,
hardness, tensile strength, and impact strength have been evaluated.
The friction coefficients of different lubricating conditions, viz.,
graphite in hydraulic oil, graphite in furnace oil, DF 150 (Graphite,
Water-Based) die lubricant and dry or without any lubrication were
obtained from the ring compression test for the above micro-alloyed
steel. Results of ring compression tests indicate that graphite in
hydraulic oil lubricant is preferred for free forging and dry lubricant
is preferred for die forging operation. Exceptionally good forgeability
and high resistance to fracture, especially for faster cooling rate has
been observed for fine equiaxed ferrite-pearlite grains, some amount
of bainite and fine precipitates of vanadium carbides and
carbonitrides. The results indicated that the cooling rate has a
remarkable effect on the microstructure and mechanical properties at
room temperature.
Abstract: In this research (using induction furnace process)
nodular iron with three different percentages of copper (residual,
0.5% and 1,2%) was obtained. Chemical analysis was performed by
mass spectrometry and microstructures were characterized by Optical
Microscopy (ASTM E3) and Scanning Electron Microscopy (SEM).
The study of mechanical behavior was carried out in a mechanical
test machine (ASTM E8) and a Pin on disk tribometer (ASTM G99)
was used to assess wear resistance. It is observed that the dissolution
of copper in crystal lattice increases the pearlite structure improving
the wear and hardness behavior, but producing a contrary effect on
the energy absorption.
Abstract: Sustainability and eco-friendly requirement of
engineering materials are sort for in recent times, thus giving rise to
the development of bio-composites. However, the natural fibres to
matrix interface interactions remain a key issue in getting the desired
mechanical properties from such composites. Treatment of natural
fibres is essential in improving matrix to filler adhesion, hence
improving its mechanical properties. In this study, investigations
were carried out to determine the effect of sodium hydroxide
treatment on the tensile, flexural, impact and hardness properties of
crushed and uncrushed Luffa cylindrica fibre reinforced recycled low
density polyethylene composites. The LC (Luffa cylindrica) fibres
were treated with 0%, 2%, 4%, 6%, 8% and 10% wt. sodium
hydroxide (NaOH) concentrations for a period of 24 hours under
room temperature conditions. A formulation ratio of 80/20 g (matrix
to reinforcement) was maintained for all developed samples. Analysis
of the results showed that the uncrushed luffa fibre samples gave
better mechanical properties compared with the crushed luffa fibre
samples. The uncrushed luffa fibre composites had a maximum
tensile and flexural strength of 7.65 MPa and 17.08 Mpa respectively
corresponding to a young modulus and flexural modulus of 21.08
MPa and 232.22 MPa for the 8% and 4% wt. NaOH concentration
respectively. Results obtained in the research showed that NaOH
treatment with the 8% NaOH concentration improved the mechanical
properties of the LC fibre reinforced composites when compared with
other NaOH treatment concentration values.
Abstract: Composite material based on Fe3Si micro-particles
and Mn-Zn nano-ferrite was prepared using powder metallurgy
technology. The sol-gel followed by autocombustion process was
used for synthesis of Mn0.8Zn0.2Fe2O4 ferrite. 3 wt.% of mechanically
milled ferrite was mixed with Fe3Si powder alloy. Mixed micro-nano
powder system was homogenized by the Resonant Acoustic Mixing
using ResodynLabRAM Mixer. This non-invasive homogenization
technique was used to preserve spherical morphology of Fe3Si
powder particles. Uniaxial cold pressing in the closed die at pressure
600 MPa was applied to obtain a compact sample. Microwave
sintering of green compact was realized at 800°C, 20 minutes, in air.
Density of the powders and composite was measured by
Hepycnometry. Impulse excitation method was used to measure
elastic properties of sintered composite. Mechanical properties were
evaluated by measurement of transverse rupture strength (TRS) and
Vickers hardness (HV). Resistivity was measured by 4 point probe
method. Ferrite phase distribution in volume of the composite was
documented by metallographic analysis.
It has been found that nano-ferrite particle distributed among
micro- particles of Fe3Si powder alloy led to high relative density
(~93%) and suitable mechanical properties (TRS >100 MPa, HV
~1GPa, E-modulus ~140 GPa) of the composite. High electric
resistivity (R~6.7 ohm.cm) of prepared composite indicate their
potential application as soft magnetic material at medium and high
frequencies.
Abstract: In rapid industrial development, the demand for
high-strength and lightweight materials have been increased. Thus,
various CFRP (Carbon Fiber Reinforced Plastics) with composite
materials are being used. The design variables of CFRP are its
lamination direction, order and thickness. Thus, the hardness and
strength of CFRP depends much on their design variables. In this
paper, the lamination direction of CFRP was used to produce a
symmetrical ply [0°/0°, -15°/+15°, -30°/+30°, -45°/+45°, -60°/+60°,
-75°/+75° and 90°/90°] and an asymmetrical ply [0°/15°, 0°/30°,
0°/45°, 0°/60° 0°/75° and 0°/90°]. The bending flexure stress of the
CFRP specimen was evaluated through a bending test. Its thermal
property was measured using an infrared camera. The symmetrical
specimen and the asymmetrical specimen were analyzed. The results
showed that the asymmetrical specimen increased the bending loads
according to the increase in the orientation angle; and from 0°, the
symmetrical specimen showed a tendency opposite the asymmetrical
tendency because the tensile force of fiber differs at the vertical
direction of its load. Also, the infrared camera showed that the thermal
property had a trend similar to that of the mechanical properties.
Abstract: Geometric and mechanical properties all influence the
resistance of RC structures and may, in certain combination of
property values, increase the risk of a brittle failure of the whole
system.
This paper presents a statistical and probabilistic investigation on
the resistance of RC beams designed according to Eurocodes 2 and 8,
and subjected to multiple failure modes, under both the natural
variation of material properties and the uncertainty associated with
cross-section and transverse reinforcement geometry. A full
probabilistic model based on JCSS Probabilistic Model Code is
derived. Different beams are studied through material nonlinear
analysis via Monte Carlo simulations. The resistance model is
consistent with Eurocode 2. Both a multivariate statistical evaluation
and the data clustering analysis of outcomes are then performed.
Results show that the ultimate load behaviour of RC beams
subjected to flexural and shear failure modes seems to be mainly
influenced by the combination of the mechanical properties of both
longitudinal reinforcement and stirrups, and the tensile strength of
concrete, of which the latter appears to affect the overall response of
the system in a nonlinear way. The model uncertainty of the
resistance model used in the analysis plays undoubtedly an important
role in interpreting results.
Abstract: Waste silicon carbide (waste SiC) filled high-density
polyethylene (HDPE) with and without surface modifiers were
studied. Two types of surface modifiers namely; high-density
polyethylene-grafted-maleic anhydride (HDPE-g-MA) and 3-aminopropyltriethoxysilane have been used in this study. The
composites were produced using a two roll mill, extruder and shaped
in a hydraulic compression molding machine. The mechanical
properties of polymer composites such as flexural strength and
modulus, impact strength, tensile strength, stiffness and hardness
were investigated over a range of compositions. It was found that,
flexural strength and modulus, tensile modulus and hardness
increased, whereas impact strength and tensile strength decreased
with the increasing in filler contents, compared to the neat HDPE. At
similar filler content, the effect of both surface modifiers increased
flexural modulus, impact strength, tensile strength and stiffness but
reduced the flexural strength. Morphological investigation using
SEM revealed that the improvement in mechanical properties was
due to enhancement of the interfacial adhesion between waste SiC
and HDPE.
Abstract: Sandwich structure composites produced by epoxy
core and aluminium skin were developed as potential building
materials. Interface bonding between core and skin was controlled by
varying kenaf content. Five different weight percentage of kenaf
loading ranging from 10 wt% to 50 wt% were employed in the core
manufacturing in order to study the mechanical properties of the
sandwich composite. Properties of skin aluminium with epoxy were
found to be affected by drying time of the adhesive. Mechanical
behavior of manufactured sandwich composites in relation with
properties of constituent materials was studied. It was found that 30
wt% of kenaf loading contributed to increase the flexural strength and
flexural modulus up to 102 MPa and 32 GPa, respectively. Analysis
were done on the flatwise and edgewise compression test. For
flatwise test, it was found that 30 wt% of fiber loading could
withstand maximum force until 250 kN, with compressive strength
results at 96.94 MPa. However, at edgewise compression test, the
sandwich composite with same fiber loading only can withstand 31
kN of the maximum load with 62 MPa of compressive strength
results.
Abstract: The present study was undertaken to investigate the
effect of aging parameters (time and temperature) on the mechanical
properties of Be-and/or Zr- treated Al-Mg-Zn (7075) alloys. Ultimate
tensile strength, 0.5% offset yield strength and % elongation
measurements were carried out on specimens prepared from cast and
heat treated 7075 alloys containing Be and/or Zr. Different aging
treatment were carried out for the as solution treated (SHT)
specimens (after quenching in warm water). The specimens were
aged at different conditions; Natural and artificial aging was carried
out at room temperature, 120C, 150C, 180C and 220C for different
periods of time. Duplex aging was performed for SHT conditions
(pre-aged at different time and temperature followed by high
temperature aging). Ultimate tensile strength, yield strength and %
elongation data results as a function of different aging parameters are
analysed. A statistical design of experiments (DOE) approach using
fractional factorial design is applied to acquire an understanding of
the effects of these variables and their interactions on the mechanical
properties of Be- and/or Zr- treated 7075 alloys. Mathematical
models are developed to relate the alloy mechanical properties with
the different aging parameters.
Abstract: The industrial process adds to engineering wood
products features absent in solid wood, with homogeneous structure
and reduced defects, improved physical and mechanical properties,
bio-deterioration, resistance and better dimensional stability,
improving quality and increasing the reliability of structures wood.
These features combined with using fast-growing trees, make them
environmentally ecological products, ensuring a strong consumer
market. The wood I-joists are manufactured by the industrial profiles
bonding flange and web, an important aspect of the production of
wooden I-beams is the adhesive joint that bonds the web to the
flange. Adhesives can effectively transfer and distribute stresses,
thereby increasing the strength and stiffness of the composite. The
objective of this study is to evaluate different resins in a shear strain
specimens with the aim of analyzing the most efficient resin and
possibility of using national products, reducing the manufacturing
cost. First was conducted a literature review, where established the
geometry and materials generally used, then established and analyzed
8 national resins and produced six specimens for each.
Abstract: The current study investigated the influence of milling
time and ball-to-powder (BPR) weight ratio on the microstructural
constituents and mechanical properties of bulk nanocrystalline Al;
Al-10%Cu; and Al-10%Cu-5%Ti alloys. Powder consolidation was
carried out using a high frequency induction heat sintering where the
processed metal powders were sintered into a dense and strong bulk
material. The powders and the bulk samples were characterized using
XRD and FEGSEM techniques. The mechanical properties were
evaluated at various temperatures of 25°C, 100°C, 200°C, 300°C and
400°C to study the thermal stability of the processed alloys. The
processed bulk nanocrystalline alloys displayed extremely high
hardness values even at elevated temperatures. The Al-10%Cu-5%Ti
alloy displayed the highest hardness values at room and elevated
temperatures which are related to the presence of Ti-containing
phases such as Al3Ti and AlCu2Ti. These phases are thermally stable
and retain the high hardness values at elevated temperatures up to
400ºC.