Abstract: The objective of this study is to evaluate the threshold
stress of the clay with sand subgrade soil. Threshold stress can be
defined as the stress level above which cyclic loading leads to
excessive deformation and eventual failure. The thickness
determination of highways formations using the threshold stress
approach is a more realistic assessment of the soil behaviour because
it is subjected to repeated loadings from moving vehicles. Threshold
stress can be evaluated by plastic strain criterion, which is based on
the accumulated plastic strain behaviour during cyclic loadings [1].
Several conditions of the all-round pressure the subgrade soil namely,
zero confinement, low all-round pressure and high all-round pressure
are investigated. The threshold stresses of various soil conditions are
determined. Threshold stress of the soil are 60%, 31% and 38.6% for
unconfined partially saturated sample, low effective stress saturated
sample, high effective stress saturated sample respectively.
Abstract: A self-compacting concrete (SCC) is the one that can
be placed in the form and can go through obstructions by its own
weight and without the need of vibration. Since its first development
in Japan in 1988, SCC has gained wider acceptance in Japan, Europe
and USA due to its inherent distinct advantages. Although there are
visible signs of its gradual acceptance in the North Africa through its
limited use in construction, Libya has yet to explore the feasibility
and applicability of SCC in new construction. The contributing
factors to this reluctance appear to be lack of any supportive
evidence of its suitability with local aggregates and the harsh
environmental conditions. The primary aim of this study is to explore
the feasibility of using SCC made with local aggregates of Eastern
Province of Libya by examining its basic properties characteristics.
This research consists of: (i) Development of a suitable mix for SCC
such as the effect of water to cement ratio, limestone and silica fume
that would satisfy the requirements of the plastic state; (ii) Casting of
concrete samples and testing them for compressive strength and unit
weight. Local aggregates, cement, admixtures and industrial waste
materials were used in this research.
The significance of this research lies in its attempt to provide
some performance data of SCC made in the Eastern Province of
Libya so as to draw attention to the possible use of SCC.
Abstract: In the present study, a numerical analysis is carried
out to investigate unsteady MHD (magneto-hydrodynamic) flow and
heat transfer of a non-Newtonian second grade viscoelastic fluid
over an oscillatory stretching sheet. The flow is induced due to an
infinite elastic sheet which is stretched oscillatory (back and forth) in
its own plane. Effect of viscous dissipation and joule heating are
taken into account. The non-linear differential equations governing
the problem are transformed into system of non-dimensional
differential equations using similarity transformations. A newly
developed meshfree numerical technique Element free Galerkin
method (EFGM) is employed to solve the coupled non linear
differential equations. The results illustrating the effect of various
parameters like viscoelastic parameter, Hartman number, relative
frequency amplitude of the oscillatory sheet to the stretching rate and
Eckert number on velocity and temperature field are reported in
terms of graphs and tables. The present model finds its application in
polymer extrusion, drawing of plastic films and wires, glass, fiber
and paper production etc.
Abstract: CONWIP (constant work-in-process) as a pull
production system have been widely studied by researchers to date.
The CONWIP pull production system is an alternative to pure push
and pure pull production systems. It lowers and controls inventory
levels which make the throughput better, reduces production lead
time, delivery reliability and utilization of work. In this article a
CONWIP pull production system was simulated. It was simulated
push and pull planning system. To compare these systems via a
production planning system (PPS) game were adjusted parameters of
each production planning system. The main target was to reduce the
total WIP and achieve throughput and delivery reliability to
minimum values. Data was recorded and evaluated. A future state
was made for real production of plastic components and the setup of
the two indicators with CONWIP pull production system which can
greatly help the company to be more competitive on the market.
Abstract: A way of achieving nanodimentional structural elements in high carbon steel by special kind of heat treatment and cold plastic deformation is being explored. This leads to increasing interlamellar spacing of ferrite-carbide mixture. Decreasing the interlamellar spacing with cooling temperature increasing is determined. Experiments confirm such interlamellar spacing with which high carbon steel demonstrates the highest treatment and hardening capability. Total deformation degree effect on interlamellar spacing value in a ferrite-carbide mixture is obtained. Mechanical experiments results show that high carbon steel after heat treatment and repetitive cold plastic deformation possesses high tensile strength and yield strength keeping good percentage elongation.
Abstract: The previous study of new metal gasket that contact
width and contact stress an important design parameter for optimizing
metal gasket performance. The optimum design based on an elastic
and plastic contact stress was founded. However, the influence of
flange surface roughness had not been investigated thoroughly. The
flange has many kinds of surface roughness. In this study, we
conducted a gasket model include a flange surface roughness effect. A
finite element method was employed to develop simulation solution. A
uniform quadratic mesh used for meshing the gasket material and a
gradually quadrilateral mesh used for meshing the flange. The gasket
model was simulated by using two simulation stages which is forming
and tightening simulation. A simulation result shows that a smoother
of surface roughness has higher slope for force per unit length. This
mean a squeezed against between flange and gasket will be strong. The
slope of force per unit length for gasket 400-MPa mode was higher
than the gasket 0-MPa mode.
Abstract: Injection molding is a very complicated process to
monitor and control. With its high complexity and many process
parameters, the optimization of these systems is a very challenging
problem. To meet the requirements and costs demanded by the
market, there has been an intense development and research with the
aim to maintain the process under control. This paper outlines the
latest advances in necessary algorithms for plastic injection process
and monitoring, and also a flexible data acquisition system that
allows rapid implementation of complex algorithms to assess their
correct performance and can be integrated in the quality control
process. This is the main topic of this paper. Finally, to demonstrate
the performance achieved by this combination, a real case of use is
presented.
Abstract: This study reports the implementation of Good
Manufacturing Practice (GMP) in a polycarbonate film processing
plant. The implementation of GMP took place with the creation of a
multidisciplinary team. It was carried out in four steps: conduct gap
assessment, create gap closure plan, close gaps, and follow up the
GMP implementation. The basis for the gap assessment is the
guideline for GMP for plastic materials and articles intended for Food
Contact Material (FCM), which was edited by Plastic Europe. The
effective results of the GMP implementation in this study showed
100% completion of gap assessment. The key success factors for
implementing GMP in production process are the commitment,
intention and support of top management.
Abstract: Superplastic deformation and high temperature load
relaxation behavior of coarse-grained iron aluminides with the
composition of Fe-28 at.% Al have been investigated. A series of load
relaxation and tensile tests were conducted at temperatures ranging
from 600 to 850oC. The flow curves obtained from load relaxation
tests were found to have a sigmoidal shape and to exhibit stress vs.
strain rate data in a very wide strain rate range from 10-7/s to 10-2/s.
Tensile tests have been conducted at various initial strain rates ranging
from 3×10-5/s to 1×10-2/s. Maximum elongation of ~500 % was
obtained at the initial strain rate of 3×10-5/s and the maximum strain
rate sensitivity was found to be 0.68 at 850oC in binary Fe-28Al alloy.
Microstructure observation through the optical microscopy (OM) and
the electron back-scattered diffraction (EBSD) technique has been
carried out on the deformed specimens and it has revealed the
evidences for grain boundary migration and grain refinement to occur
during superplastic deformation, suggesting the dynamic
recrystallization mechanism. The addition of Cr by the amount of 5
at.% appeared to deteriorate the superplasticity of the binary iron
aluminide. By applying the internal variable theory of structural
superplasticity, the addition of Cr has been revealed to lower the
contribution of the frictional resistance to dislocation glide during high
temperature deformation of the Fe3Al alloy.
Abstract: With respect to the dissipation of energy through
plastic deformation of joints of prefabricated wall units, the paper
points out the principal importance of efficient reinforcement of the
prefabricated system at its joints. The method, quality and amount of
reinforcement are essential for reaching the necessary degree of joint
ductility. The paper presents partial results of experimental research
of vertical joints of prefabricated units exposed to monotonously
rising loading and repetitive shear force and formulates a conclusion
that the limit state of the structure as a whole is preceded by the
disintegration of joints, or that the structure tends to pass from
linearly elastic behaviour to non-linearly elastic to plastic behaviour
by exceeding the proportional elastic limit in joints.Experimental
verification on a model of a 7-storey prefabricated structure revealed
weak points in its load-bearing systems, mainly at places of critical
points around openings situated in close proximity to vertical joints
of mutually perpendicularly oriented walls.
Abstract: General as well as the MSW management in Thailand is reviewed in this paper. Topics include the MSW generation, sources, composition, and trends. The review, then, moves to sustainable solutions for MSW management, sustainable alternative approaches with an emphasis on an integrated MSW management. Information of waste in Thailand is also given at the beginning of this paper for better understanding of later contents. It is clear that no one single method of MSW disposal can deal with all materials in an environmentally sustainable way. As such, a suitable approach in MSW management should be an integrated approach that could deliver both environmental and economic sustainability. With increasing environmental concerns, the integrated MSW management system has a potential to maximize the useable waste materials as well as produce energy as a by-product. In Thailand, the compositions of waste (86%) are mainly organic waste, paper, plastic, glass, and metal. As a result, the waste in Thailand is suitable for an integrated MSW management. Currently, the Thai national waste management policy starts to encourage the local administrations to gather into clusters to establish central MSW disposal facilities with suitable technologies and reducing the disposal cost based on the amount of MSW generated.
Abstract: The research investigates the effects of super plasticizer and molarity of sodium hydroxide alkaline solution on the workability, microstructure and compressive strength of self compacting geopolymer concrete (SCGC). SCGC is an improved way of concreting execution that does not require compaction and is made by complete elimination of ordinary Portland cement content. The parameters studied were superplasticizer (SP) dosage and molarity of NaOH solution. SCGC were synthesized from low calcium fly ash, activated by combinations of sodium hydroxide and sodium silicate solutions, and by incorporation of superplasticizer for self compactability. The workability properties such as filling ability, passing ability and resistance to segregation were assessed using slump flow, T-50, V-funnel, L-Box and J-ring test methods. It was found that the essential workability requirements for self compactability according to EFNARC were satisfied. Results showed that the workability and compressive strength improved with the increase in superplasticizer dosage. An increase in strength and a decrease in workability of these concrete samples were observed with the increase in molarity of NaOH solution from 8M to 14M. Improvement of interfacial transition zone (ITZ) and micro structure with the increase of SP and increase of concentration from 8M to 12M were also identified.
Abstract: Plastics occupy wide place in the applications of
automotive, electronics and house goods. Especially reinforced
plastics become popular because of their high strength besides their
advantages of low weight and easy manufacturability. In this study,
mechanical and morphological properties of polypropylene (PP) and
high density polyethylene (HDPE) matrix composites reinforced with
surface modified nano titan dioxide (TiO2) particles were
investigated. Surface modification was made by coating the nano
powders with maleic anhydride grafted styrene ethylene butylene
styrene (SEBS-g-MA) and silane, respectively. After surface
modification, PP/TiO2 and HDPE/TiO2 composites were obtained by
using twin screw extruder at titan dioxide loading of 1 wt.%, 3 wt.%
and 5 wt.%. Effects of surface modification were determined by
thermal and morphological analysis. SEBS-g-MA provided bridging
effect between TiO2 particles and polymer matrix while silane was
effective as a dispersant. Depending on that, homogenous structures
without agglomeration were obtained. Mechanical tests were
performed on the injection moldings of the composites for obtaining
the impact strength, tensile strength, stress at break, elongation and
elastic modulus. Reinforced HDPE and PP moldings gave higher
tensile strength and elastic modulus due to the rigid structure of TiO2.
Slight increment was seen in stress at break. Elongation and impact
strength decreased due to the stiffness of the nano titan dioxide.
Abstract: Nonlinear finite element method and Serendipity eight
nodes element are used for determining of ground surface settlement
due to tunneling. Linear element with elastic behavior is used for
modeling of lining. Modified Generalized plasticity model with nonassociated
flow rule is applied for analysis of a tunnel in Sao Paulo –
Brazil. The tunnel had analyzed by Lades- model with 16 parameters.
In this work modified Generalized Plasticity is used with 10
parameters, also Mohr-Coulomb model is used to analysis the tunnel.
The results show good agreement with observed results of field data
by modified Generalized Plasticity model than other models. The
obtained result by Mohr-Coulomb model shows less settlement than
other model due to excavation.
Abstract: In this study the elastic-plastic stress distribution in
weld-bonded joint, fabricated from austenitic stainless steel (AISI
304) sheet of 1.00 mm thickness and Epoxy adhesive Araldite 2011,
subjected to axial loading is investigated. This is needed to improve
design procedures and welding codes, and saving efforts in the
cumbersome experiments and analysis. Therefore, a complete 3-D
finite element modelling and analysis of spot welded, bonded and
weld-bonded joints under axial loading conditions is carried out. A
comprehensive systematic experimental program is conducted to
determine many properties and quantities, of the base metals and the
adhesive, needed for FE modelling, such like the elastic – plastic
properties, modulus of elasticity, fracture limit, the nugget and heat
affected zones (HAZ) properties, etc. Consequently, the finite
element models developed, for each case, are used to evaluate
stresses distributions across the entire joint, in both the elastic and
plastic regions. The stress distribution curves are obtained,
particularly in the elastic regions and found to be consistent and in
excellent agreement with the published data. Furthermore, the
stresses distributions are obtained in the weld-bonded joint and
display the best results with almost uniform smooth distribution
compared to spot and bonded cases. The stress concentration peaks at
the edges of the weld-bonded region, are almost eliminated resulting
in achieving the strongest joint of all processes.
Abstract: Borate minerals have attracted considerable attention in the past years due to their structural chemistry and mechanical properties in several industries. Recently, increasing attention has been paid to the use of; synthetically produced magnesium borates as catalysts reinforcing material for plastics, the conversion of hydrocarbons, electro-conductive treating agent, anti-wear and anti-corrosion materials. Magnesium borates can be synthesized by several methods such as; hydrothermal and solid-state (thermal) processes. In this study the hydrothermal production method was applied at the modest temperature of 80C along with convenient crystal growth. Using MgCl2.6H2O, H3BO3, and NaOH as starting materials, 30, 60, 120, 240 minutes of reaction times were studied. After all, the crystal structure and the morphology of the products were examined by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). As a result the forms of Admontite and Mcallisterite minerals were synthesized.
Abstract: This paper presents the results of an experimental study on the performance of a triboelectric separator of plastic mixtures used for recycling. The separator consists of four cylindrical electrodes. The principle behind the separation technique is based on the difference in the Coulomb force acting on the plastic particles after triboelectric charging. The separation of mixtures of acrylonitrile butadiene styrene (ABS) and polystyrene (PS) using this method was studied. The effects of the triboelectric charging time and applied voltage on the separation efficiency were investigated. The experimental results confirm that it is possible to obtain a high purity and recovery rate for the initial compositions considered in this study.
Abstract: This paper deals with analysis of flexural stiffness,
indentation and their energies in three point loading of sandwich
beams with composite faces from Eglass/epoxy and cores from
Polyurethane or PVC. Energy is consumed in three stages of
indentation in laminated beam, indentation of sandwich beam and
bending of sandwich beam. Theory of elasticity is chosen to present
equations for indentation of laminated beam, then these equations
have been corrected to offer better results. An analytical model has
been used assuming an elastic-perfectly plastic compressive behavior
of the foam core. Classical theory of beam is used to describe three
point bending. Finite element (FE) analysis of static indentation
sandwich beams is performed using the FE code ABAQUS. The
foam core is modeled using the crushable foam material model and
response of the foam core is experimentally characterized in uniaxial
compression.
Three point bending and indentation have been done
experimentally in two cases of low velocity and higher velocity
(quasi-impact) of loading. Results can describe response of beam in
terms of core and faces thicknesses, core material, indentor diameter,
energy absorbed, and length of plastic area in the testing. The
experimental results are in good agreement with the analytical and
FE analyses. These results can be used as an introduction for impact
loading and energy absorbing of sandwich structures.
Abstract: Moulded parts contribute to more than 70% of
components in products. However, common defects particularly in
plastic injection moulding exist such as: warpage, shrinkage, sink
marks, and weld lines. In this paper Taguchi experimental design
methods are applied to reduce the warpage defect of thin plate
Acrylonitrile Butadiene Styrene (ABS) and are demonstrated in two
levels; namely, orthogonal arrays of Taguchi and the Analysis of
Variance (ANOVA). Eight trials have been run in which the optimal
parameters that can minimize the warpage defect in factorial
experiment are obtained. The results obtained from ANOVA
approach analysis with respect to those derived from MINITAB
illustrate the most significant factors which may cause warpage in
injection moulding process. Moreover, ANOVA approach in
comparison with other approaches like S/N ratio is more accurate and
with the interaction of factors it is possible to achieve higher and the
better outcomes.
Abstract: Researchers investigate arious strategies to develop composite beams and maximize the structural advantages. This study
attempted to conduct experiments and analysis of changes in the
neutral axis of positive moments of a Green Beam. Strain
compatibility analysis was used, and its efficiency was demonstrated
by comparing experimental and analytical values. In the comparison of
neutral axis, the difference between experimental and analytical values
was found to range from 8.8~26.2%. It was determined that strain
compatibility analysis can be useful for predicting the behaviors of
composite beams, with the ability to predict the behavior of not only
the elastic location of the composite member, but also of the plastic
location