Abstract: A Friction stir welding tool is a critical component to
the success of the process. The tool typically consists of a rotating
round shoulder and a threaded cylindrical pin that heats the work
piece, mostly by friction, and moves the softened alloy around it to
form the joint. In this research work, an attempt has been made to
investigate the relationship between FSW variables mainly tool
profile, rotating speed, welding speed and the mechanical properties
(tensile strength, yield strength, percentage elongation, and micro
hardness) of friction stir welded aluminum alloy 5083 joints. From
the experimental details, it can be assessed that the joint produced by
using Triflute profile tool has contribute superior mechanical and
structural properties as compared to Tapered unthreaded & Threaded
tool for 1000rpm.
Abstract: This paper describes the development of new class of
epoxy based rice husk filled jute reinforced composites. Rice husk
flour is added in 0%, 1%, 3%, 5% by weight. Epoxy resin and
triethylenetetramine (T.E.T.A) is used as matrix and hardener
respectively. It investigates the mechanical properties of the
composites and a comparison is done for monolithic jute composite
and the filled ones. The specimens are prepared according to the
ASTM standards and experimentation is carried out using INSTRON
8801. The result shows that with the increase of filler percentage the
tensile properties increases but compressive and flexural properties
decreases.
Abstract: Inspired by the Formula-1 competition, IMechE
(Institute of Mechanical Engineers) and Formula SAE (Society of
Mechanical Engineers) organize annual competitions for University
and College students worldwide to compete with a single-seat racecar
they have designed and built. Design of the chassis or the frame is a
key component of the competition because the weight and stiffness
properties are directly related with the performance of the car and the
safety of the driver. In addition, a reduced weight of the chassis has
direct influence on the design of other components in the car. Among
others, it improves the power to weight ratio and the aerodynamic
performance. As the power output of the engine or the battery
installed in the car is limited to 80 kW, increasing the power to
weight ratio demands reduction of the weight of the chassis, which
represents the major part of the weight of the car. In order to reduce
the weight of the car, ION Racing team from University of
Stavanger, Norway, opted for a monocoque design. To ensure
fulfilment of the competition requirements of the chassis, the
monocoque design should provide sufficient torsional stiffness and
absorb the impact energy in case of possible collision. The study reported in this article is based on the requirements for
Formula Student competition. As part of this study, diverse
mechanical tests were conducted to determine the mechanical
properties and performances of the monocoque design. Upon a
comprehensive theoretical study of the mechanical properties of
sandwich composite materials and the requirements of monocoque
design in the competition rules, diverse tests were conducted
including 3-point bending test, perimeter shear test and test for
absorbed energy. The test panels were homemade and prepared with
equivalent size of the side impact zone of the monocoque, i.e. 275
mm x 500 mm, so that the obtained results from the tests can be
representative. Different layups of the test panels with identical core
material and the same number of layers of carbon fibre were tested
and compared. Influence of the core material thickness was also
studied. Furthermore, analytical calculations and numerical analysis
were conducted to check compliance to the stated rules for Structural
Equivalency with steel grade SAE/AISI 1010. The test results were
also compared with calculated results with respect to bending and
torsional stiffness, energy absorption, buckling, etc. The obtained results demonstrate that the material composition
and strength of the composite material selected for the monocoque
design has equivalent structural properties as a welded frame and thus
comply with the competition requirements. The developed analytical
calculation algorithms and relations will be useful for future
monocoque designs with different lay-ups and compositions.
Abstract: Geopolymer composites reinforced with flax fabrics
and nanoclay are fabricated and studied for physical and mechanical
properties using X-Ray Diffraction (XRD), Fourier Transform
Infrared Spectroscopy (FTIR), and Scanning Electron Microscope
(SEM). Nanoclay platelets at a weight of 1.0%, 2.0%, and 3.0% were
added to geopolymer pastes. Nanoclay at 2.0 wt.% was found to
improve density and decrease porosity while improving flexural
strength and post-peak toughness. A microstructural analysis
indicated that nanoclay behaves as filler and as an activator
supporting geopolymeric reaction while producing a higher content
geopolymer gel improving the microstructure of binders. The process
enhances adhesion between the geopolymer matrix and flax fibres.
Abstract: In this work, our goal is to optimize the nitriding treatment at a low-temperature of the steel 32CrMoV13 using gas mixtures of ammonia, nitrogen and hydrogen to improve the mechanical properties of the surface (good wear resistance, friction and corrosion), and of the diffusion layer of the nitrogen (good resistance to fatigue and good tenacity with heart). By limiting our work to the pure iron and to the alloys iron-chromium and iron-chromium-carbon, we have studied the various parameters which manage the nitriding: flow rate and composition of the gaseous phase, the interaction chromium-nitrogen and chromium-carbon by the help of experiments of nitriding realized in the laboratory by thermogravimetry. The acquired knowledge has been applied by the mastery of the growth of the γ' combination layer on the α diffusion layer in the case of the industrial steel 32CrMoV13.
Abstract: Within Rapid Prototyping technologies are used many
types of materials. Many of them are recyclable but there are still as
plastic like, so practically they do not degrade in the landfill.
Polylactic acid (PLA) is one of the special plastic materials, which
are biodegradable and available for 3D printing within Fused
Deposition Modeling (FDM) technology. The question is, if the
mechanical properties of produced models are comparable to similar
technical plastic materials which are usual for prototype production.
Presented paper shows the experiments results for tensile strength
measurements for specimens prepared with different 3D printer
settings and model orientation. Paper contains also the comparison of
tensile strength values with values measured on specimens produced
by conventional technologies as injection moulding.
Abstract: This research paper portrays a comparative analysis of
thermomechanical behaviour of Shielded Metal Arc Welding
(SMAW) and Gas Tungsten Arc Welding (GTAW) of low carbon
steel of AISI 1020 grade butt joints. The thermal history has been
obtained by experimental work. We have focused on temperature
dependent cooling rate as depicted by Adam’s two-dimensional
model. The effect of moving point heat source of SMAW and GTAW
on mechanical properties has been judged by optical and scanning
electron micrographs of different regions in weld joints. The
microhardness study has been carried to visualize the joint strength
due to formation of different phases.
Abstract: Heat treatable aluminum alloys such as 7075 and
7055, because of high strength and low density, are used widely in
aircraft industry. For best mechanical properties, T6 heat treatment
has recommended for this regards, but this temper treatment is
sensitive to corrosion induced and Stress Corrosion Cracking (SCC)
damage. For improving this property, the over-aging treatment (T7)
applies to this alloy, but it decreases the mechanical properties up to
30 percent. Hence, to increase the mechanical properties, without any
remarkable decrease in SCC resistant, Retrogression and Re-Aging
(RRA) heat treatment is used. This treatment performs in a relatively
short time. In this paper, the RRA heat treatment was applied to 7055
aluminum alloy and then effect of RRA time on the mechanical
properties of 7055 has been investigated. The results show that the
40-minute time is suitable time for retrogression of 7055 aluminum
alloy and ultimate strength increases up to 625MPa.
Abstract: The use of magnesium alloys is limited due to their
susceptibility to corrosion although they have many attractive
physical and mechanical properties. To increase mechanical and
corrosion properties of these alloys, many deposition method and
coating types are used. Electroless Ni–B coatings have received
considerable interest recently due to its unique properties such as
cost-effectiveness, thickness uniformity, good wear resistance,
lubricity, good ductility and corrosion resistance, excellent
solderability and electrical properties and antibacterial property. In
this study, electroless Ni-B coating could been deposited on AZ91
magnesium alloy. The obtained coating exhibited a harder and
rougher structure than the substrate.
Abstract: The objective of this study was to synthesize and
characterize the poly(alkenoic acid)s with different molecular
structures, use these polymers to formulate a dental cement
restorative, and study the effect of molecular structures on reaction
kinetics, viscosity, and mechanical strengths of the formed polymers
and cement restoratives. In this study, poly(alkenoic acid)s with
different molecular structures were synthesized. The purified
polymers were formulated with commercial Fuji II LC glass fillers to
form the experimental cement restoratives. The reaction kinetics was
studied via 1HNMR spectroscopy. The formed restoratives were
evaluated using compressive strength, diametral tensile strength,
flexural strength, hardness and wear-resistance tests. Specimens were
conditioned in distilled water at 37oC for 24 h prior to testing. Fuji II
LC restorative was used as control. The results show that the higher
the arm number and initiator concentration, the faster the reaction
was. It was also found that the higher the arm number and branching
that the polymer had, the lower the viscosity of the polymer in water
and the lower the mechanical strengths of the formed restorative. The
experimental restoratives were 31-53% in compressive strength, 37-
55% in compressive modulus, 80-126% in diametral tensile strength,
76-94% in flexural strength, 4-21% in fracture toughness and 53-96%
in hardness higher than Fuji II LC. For wear test, the experimental
restoratives were only 5.4-13% of abrasive and 6.4-12% of attritional
wear depths of Fuji II LC in each wear cycle. The aging study also
showed that all the experimental restoratives increased their strength
continuously during 30 days, unlike Fuji II LC. It is concluded that
polymer molecular structures have significant and positive impact on
mechanical properties of dental cement restoratives.
Abstract: The current study focuses on the seismic design of
offshore pipelines against active faults. After an extensive literature
review of the provisions of the seismic norms worldwide and of the
available analytical methods, the study simulates numerically
(through finite-element modeling and strain-based criteria) the
distress of offshore pipelines subjected to PGDs induced by active
normal and reverse seismic faults at the seabed. Factors, such as the
geometrical properties of the fault, the mechanical properties of the
ruptured soil formations, and the pipeline characteristics, are
examined. After some interesting conclusions regarding the seismic
vulnerability of offshore pipelines, potential cost-effective mitigation
measures are proposed taking into account constructability issues.
Abstract: The present study deals with the characterization of
CrSiN coatings obtained by PVD magnetron sputtering systems.
CrSiN films were deposited with different Si contents, in order to
check the effect of at.% variation on the different properties of the
Cr–N system. Coatings were characterized by scanning electron
microscopy (SEM) for thickness measurements, X-ray diffraction.
Surface morphology and the roughness characteristics were explored
using AFM, Mechanicals properties, elastic and plastic deformation
resistance of thin films were investigated using nanoindentation test. We observed that the Si addition improved the hardness and the
Young’s modulus of the Cr–N system. Indeed, the hardness value is
18,56 GPa for CrSiN coatings. Besides, the Young’s modulus value
is 224,22 GPa for CrSiN coatings for Si content of 1.2 at.%.
Abstract: The development of composite materials and the
related design and manufacturing technologies is one of the most
important advances in the history of materials. Composites are
multifunctional materials having unprecedented mechanical and
physical properties that can be tailored to meet the requirements of a
particular application. Some composites also exhibit great resistance
to high-temperature corrosion, oxidation, and wear. Polymers are
widely used indoors and outdoors, therefore they are exposed to a
chemical environment which may include atmospheric oxygen, acidic
fumes, acidic rain, moisture heat and thermal shock, ultra-violet light,
high energy radiation, etc. Different polymers are affected differently
by these factors even though the amorphous polymers are more
sensitive. Ageing is also important and it is defined as the process of
deterioration of engineering materials resulting from the combined
effects of atmospheric radiation, heat, oxygen, water, microorganisms
and other atmospheric factors.
Abstract: Natural admixtures provide concrete with enhanced
properties but their processing end up making them very expensive
resulting in increase to cost of concrete. In this study the effect
of Gum from Acacia Karroo (GAK) as set-retarding admixture
in cement pastes was studied. The possibility of using GAK as
water reducing admixture both in cement mortar concrete was
also investigated. Cement pastes with different dosages of GAK
were prepared to measure the setting time using different dosages.
Compressive strength of cement mortars with 0.7, 0.8 and 0.9%
weight of cement and w/c ratio of 0.5 were compared to those with
water cement (w/c) ratio of 0.44 but same dosage of GAK. Concrete
samples were prepared using higher dosages of GAK (1, 2 and 3%
wt of cement) and a water bidder (w/b) of 0.61 were compared to
those with the same GAK dosage but with reduced w/b ratio. There
was increase in compressive strength of 9.3% at 28 days for cement
mortar samples with 0.9% dosage of GAK and reduced w/c ratio.
Abstract: Natural fibers are used in polymer composites to
improve mechanical properties to replace inorganic reinforcing
agents produced by non-renewable resources. The present study
investigates the tensile and flexural behaviors of palm fibers-high
density polyethylene (HDPE) composite as a function of volume
fraction. The surface of the fibers was treated by mercerization
treatments to improve the wetting behavior of the apolar HDPE. The
treatment characterization was obtained by scanning electron
microscopy, X-Ray diffraction and infrared spectroscopy. Results
evidences that a good adhesion interfacial between fibers-matrix
caused an increase strength and modulus flexural as well as tensile
strength in the modified fibers/HDPE composites when compared to
the pure HDPE and untreated fibers reinforced composites.
Abstract: Effect of alloying on the microstructure and mechanical properties of heat-resisting duplex stainless steel (DSS) for Mg production was investigated in this study. 25Cr-8Ni based DSS’s were cast into rectangular ingots of which the dimension was 350×350×100 mm3 . Nitrogen and Yttrium were added in the range within 0.3 in weight percent. Phase equilibrium was calculated using the FactSage®, thermodynamic software. Hot exposure, high temperature tensile and compression tests were conducted on the ingots at 1230oC, which is operation temperature employed for Mg production by Silico-thermic reduction. The steel with N and Y showed much higher strength than 310S alloy in both tensile and compression tests. By thermal exposition at 1230oC for 200 hrs, hardness of DSS containing N and Y was found to increase. Hot workability of the heat-resisting DSS was evaluated by employing hot rolling at 1230 oC. Hot shortness was observed in the ingot with N and found to disappear after addition of Y.
Abstract: In this paper, we present a quantum statistical
mechanical formulation from our recently analytical expressions for
partial-wave transition matrix of a three-particle system. We report
the quantum reactive cross sections for three-body scattering
processes 1+(2,3)→1+(2,3) as well as recombination
1+(2,3)→1+(3,1) between one atom and a weakly-bound dimer. The
analytical expressions of three-particle transition matrices and their
corresponding cross-sections were obtained from the threedimensional
Faddeev equations subjected to the rank-two non-local
separable potentials of the generalized Yamaguchi form. The
equilibrium quantum statistical mechanical properties such partition
function and equation of state as well as non-equilibrium quantum
statistical properties such as transport cross-sections and their
corresponding transport collision integrals were formulated
analytically. This leads to obtain the transport properties, such as
viscosity and diffusion coefficient of a moderate dense gas.
Abstract: The moisture content of densified biomass is a
limiting parameter influencing the quality of this solid biofuel. It
influences its calorific value, density, mechanical strength and
dimensional stability as well as affecting its production process. This
paper deals with experimental research into the effect of moisture
content of the densified material on the final quality of biofuel in the
form of logs (briquettes or pellets). Experiments based on the singleaxis
densification of the spruce sawdust were carried out with a
hydraulic piston press (piston and die), where the densified logs were
produced at room temperature. The effect of moisture content on the
qualitative properties of the logs, including density, change of
moisture, expansion and physical changes, and compressive and
impact resistance were studied. The results show the moisture ranges
required for producing good-quality logs. The experiments were
evaluated and the moisture content of the tested material was
optimized to achieve the optimum value for the best quality of the
solid biofuel. The dense logs also have high-energy content per unit
volume. The research results could be used to develop and optimize
industrial technologies and machinery for biomass densification to
achieve high quality solid biofuel.
Abstract: Polymeric micro-cantilevers (Cs) are rapidly
becoming popular for MEMS applications such as chemo- and biosensing
as well as purely electromechanical applications such as
microrelays. Polymer materials present suitable physical and
chemical properties combined with low-cost mass production. Hence,
micro-cantilevers made of polymers indicate much more
biocompatibility and adaptability of rapid prototyping along with
mechanical properties. This research studies the effects of three
process and one size factors on the filling behaviour in micro cavity,
and the role of each in the replication of micro parts using different
polymer materials i.e. polypropylene (PP) SABIC 56M10 and
acrylonitrile butadiene styrene (ABS) Magnum 8434 . In particular,
the following factors are considered: barrel temperature, mould
temperature, injection speed and the thickness of micro features. The
study revealed that the barrel temperature and the injection speed are
the key factors affecting the flow length of micro features replicated
in PP and ABS. For both materials, an increase of feature sizes
improves the melt flow. However, the melt fill of micro features does
not increase linearly with the increase of their thickness.
Abstract: Concrete is strong in compression however weak in
tension. The tensile strength as well as ductile property of concrete
could be improved by addition of short dispersed fibers. Polyethylene
terephthalate (PET) fiber obtained from hand cutting or mechanical
slitting of plastic sheets generally used as discrete reinforcement in
substitution of steel fiber. PET fiber obtained from the former process
is in the form of straight slit sheet pattern that impart weaker
mechanical bonding behavior in the concrete matrix. To improve the
limitation of straight slit sheet fiber the present study considered two
additional geometry of fiber namely (a) flattened end slit sheet and
(b) deformed slit sheet. The mix for plain concrete was design for a
compressive strength of 25 MPa at 28 days curing time with a watercement
ratio of 0.5. Cylindrical and beam specimens with 0.5% fibers
volume fraction and without fibers were cast to investigate the
influence of geometry on the mechanical properties of concrete. The
performance parameters mainly studied include flexural strength,
splitting tensile strength, compressive strength and ultrasonic pulse
velocity (UPV). Test results show that geometry of fiber has a
marginal effect on the workability of concrete. However, it plays a
significant role in achieving a good compressive and tensile strength
of concrete. Further, significant improvement in term of flexural and
energy dissipation capacity were observed from other fibers as
compared to the straight slit sheet pattern. Also, the inclusion of PET
fiber improved the ability in absorbing energy in the post-cracking
state of the specimen as well as no significant porous structures.