Abstract: This work presents an improved single fiber pull-out
test for fiber/matrix interface characterization. This test has been
used to study the Inter-Facial Shear Strength ‘IFSS’ of hemp fibers
reinforced polypropylene (PP). For this aim, the fiber diameter
has been carefully measured using a tomography inspired method.
The fiber section contour can then be approximated by a circle
or a polygon. The results show that the IFSS is overestimated if
the circular approximation is used. The Influence of the molding
temperature on the IFSS has also been studied. We find that a molding
temperature of 183◦C leads to better interfacial properties. Above or
below this temperature the interface strength is reduced.
Abstract: This paper investigates the parametric stability of an
axially moving web subjected to non-uniform in-plane edge
excitations on two opposite, simply-supported edges. The web is
modeled as a viscoelastic plate whose constitutive relation obeys the
Kelvin-Voigt model, and the in-plane edge excitations are expressed
as the sum of a static tension and a periodical perturbation. Due to the
in-plane edge excitations, the moving plate may bring about
parametric instability under certain situations. First, the in-plane
stresses of the plate due to the non-uniform edge excitations are
determined by solving the in-plane forced vibration problem. Then,
the dependence on the spatial coordinates in the equation of transverse
motion is eliminated by the generalized Galerkin method, which
results in a set of discretized system equations in time. Finally, the
method of multiple scales is utilized to solve the set of system
equations analytically if the periodical perturbation of the in-plane
edge excitations is much smaller as compared with the static tension of
the plate, from which the stability boundaries of the moving plate are
obtained. Numerical results reveal that only combination resonances
of the summed-type appear under the in-plane edge excitations
considered in this work.
Abstract: Numerical investigations were conducted to study the
influence of flexural reinforcement ratio on the diagonal cracking
strength and ultimate shear strength of reinforced concrete (RC)
beams without stirrups. Three-dimensional nonlinear finite element
analyses (FEAs) of the beams with flexural reinforcement ratios
ranging from 0.58% to 2.20% subjected to a mid-span concentrated
load were carried out. It is observed that the load-deflection and loadstrain
curves obtained from the numerical analyses agree with those
obtained from the experiments. It is concluded that flexural
reinforcement ratio has a significant effect on the shear strength and
deflection capacity of RC beams without stirrups. The predictions of
diagonal cracking strength and ultimate shear strength of beams
obtained by using the equations defined by a number of codes and
researchers are compared with each other and with the experimental
values.
Abstract: In present global scenario, aluminum alloys are
coining the attention of many innovators as competing structural
materials for automotive and space applications. Comparing to other
challenging alloys, especially, 7xxx series aluminum alloys have
been studied seriously because of benefits such as moderate strength;
better deforming characteristics and affordable cost. It is expected
that substitution of aluminum alloys for steels will result in great
improvements in energy economy, durability and recyclability.
However, it is necessary to improve the strength and the formability
levels at low temperatures in aluminum alloys for still better
applications. Aluminum–Zinc–Magnesium with or without other
wetting agent denoted as 7XXX series alloys are medium strength
heat treatable alloys. In addition to Zn, Mg as major alloying
additions, Cu, Mn and Si are the other solute elements which
contribute for the improvement in mechanical properties by suitable
heat treatment process. Subjecting to suitable treatments like age
hardening or cold deformation assisted heat treatments; known as low
temperature thermomechanical treatments (LTMT) the challenging
properties might be incorporated. T6 is the age hardening or
precipitation hardening process with artificial aging cycle whereas T8
comprises of LTMT treatment aged artificially with X% cold
deformation. When the cold deformation is provided after solution
treatment, there is increase in hardness related properties such as
wear resistance, yield and ultimate strength, toughness with the
expense of ductility. During precipitation hardening both hardness
and strength of the samples are increasing. The hardness value may
further improve when room temperature deformation is positively
supported with age hardening known as thermomechanical treatment.
It is intended to perform heat treatment and evaluate hardness, tensile
strength, wear resistance and distribution pattern of reinforcement in
the matrix. 2 to 2.5 and 3 to 3.5 times increase in hardness is reported
in age hardening and LTMT treatments respectively as compared to
as-cast composite. There was better distribution of reinforcements in
the matrix, nearly two fold increase in strength levels and up to 5
times increase in wear resistance are also observed in the present
study.
Abstract: Numerical studies have been carried out using a
validated two-dimensional standard k-omega turbulence model for
the design optimization of a thrust vector control system using shock
induced self-impinging supersonic secondary double jet. Parametric
analytical studies have been carried out at different secondary
injection locations to identifying the highest unsymmetrical
distribution of the main gas flow due to shock waves, which produces
a desirable side force more lucratively for vectoring. The results from
the parametric studies of the case on hand reveal that the shock
induced self-impinging supersonic secondary double jet is more
efficient in certain locations at the divergent region of a CD nozzle
than a case with supersonic single jet with same mass flow rate. We
observed that the best axial location of the self-impinging supersonic
secondary double jet nozzle with a given jet interaction angle, built-in
to a CD nozzle having area ratio 1.797, is 0.991 times the primary
nozzle throat diameter from the throat location. We also observed
that the flexible steering is possible after invoking ON/OFF facility to
the secondary nozzles for meeting the onboard mission requirements.
Through our case studies we concluded that the supersonic self-impinging
secondary double jet at predesigned jet interaction angle
and location can provide more flexible steering options facilitating
with 8.81% higher thrust vectoring efficiency than the conventional
supersonic single secondary jet without compromising the payload
capability of any supersonic aerospace vehicle.
Abstract: Studying stress and strain trends in the femur and
recognizing femur failure mechanism is very important for
preventing hip fracture in the elderly. The aim of this study was to
identify high stress and strain regions in the femur during normal
walking and falling to find the mechanical behavior and failure
mechanism of the femur. We developed a finite element model of the
femur from the subject’s quantitative computed tomography (QCT)
image and used it to identify potentially high stress and strain regions
during the single-leg stance and the sideways fall. It was found that
fracture may initiate from the superior region of femoral neck and
propagate to the inferior region during a high impact force such as
sideways fall. The results of this study showed that the femur bone is
more sensitive to strain than stress which indicates the effect of
strain, in addition to effect of stress, should be considered for failure
analysis.
Abstract: It is a major challenge to build a bridge superstructure
that has long-term durability and low maintenance requirements. A
solution to this challenge may be to use new materials or to
implement new structural systems. Fiber Reinforced Polymer (FRP)
composites have continued to play an important role in solving some
of persistent problems in infrastructure applications because of its
high specific strength, light weight, and durability. In this study, the
concept of the hybrid FRP-concrete structural systems is applied to a
bridge superstructure. The hybrid FRP-concrete bridge superstructure
is intended to have durable, structurally sound, and cost effective
hybrid system that will take full advantage of the inherent properties
of both FRP materials and concrete. In this study, two hybrid FRP-concrete
bridge systems were investigated. The first system consists
of trapezoidal cell units forming a bridge superstructure. The second
one is formed by arch cells. The two systems rely on using cellular
components to form the core of the bridge superstructure, and an
outer shell to warp around those cells to form the integral unit of the
bridge. Both systems were investigated analytically by using finite
element (FE) analysis. From the rigorous FE studies, it was
concluded that first system is more efficient than the second.
Abstract: The goal of the paper is to highlight the effect of the
building design and epicentral distance on the storey lateral
displacements, for several reinforced concrete buildings (6, 9 and 12
stories). These structures are subjected to seismic accelerations from
the Boumerdes earthquake (Algeria, May 21st, Mw = 6.8). Using the
response spectrum method (modal spectral approach), the analysis is
performed in both longitudinal and transverse directions. The
building design is expressed through the fundamental period and
epicentral distance is used to represent the earthquake effect variation
on storey lateral displacements and interstory drift for the considered
buildings.
Abstract: The Chair of Thermal Engineering at Poznan
University of Technology has been conducted research works on the
possibilities of using carbon nanostructures in energy and mechanics
applications for a couple of years. Those studies have provided results in a form of co-operation with foreign research centres, numerous publications and patent
applications.
Authors of this paper have studied the influence of multi-walled
carbon nanostructures on changes in static friction arising when steel
surfaces were moved. Tests were made using the original test stand
consisting of automatically controlled inclined plane driven by
precise stepper motors. Computer program created in the LabView
environment was responsible for monitoring of the stand operation,
accuracy of measurements and archiving the obtained results. Such a
solution enabled to obtain high accuracy and repeatability of all
conducted experiments.
Tests and analysis of the obtained results allowed us to determine
how additional layers of carbon nanostructures influenced on changes
of static friction coefficients. At the same time, we analyzed the
potential possibilities of applying nanostructures under consideration
in mechanics.
Abstract: 3-roller conical bending process is widely used in the
industries for manufacturing of conical sections and shells. It
involves static as well dynamic bending stages. Analytical models for
prediction of bending force during static as well as dynamic bending
stage are available in the literature. In this paper bending forces
required for static bending stage and dynamic bending stages have
been compared using the analytical models. It is concluded that force
required for dynamic bending is very less as compared to the bending
force required during the static bending stage.
Abstract: It is an established fact that polymers have several
physical limitations such as low stiffness and low resistance to
impact on loading. Hence, polymers do not usually have requisite
mechanical strength for application in various fields. The
reinforcement by high strength fibers provides the polymer
substantially enhanced mechanical properties and makes them more
suitable for a large number of diverse applications. This research
evaluates the effects of particulate Cow bone and Groundnut shell
additions on the mechanical properties and microstructure of cow
bone and groundnut shell reinforced epoxy composite in order to
assess the possibility of using it as a material for engineering
applications. Cow bone and groundnut shell particles reinforced with
epoxy (CBRPC and GSRPC) was prepared by varying the cow bone
and groundnut shell particles from 0-25 wt% with 5 wt% intervals. A
Hybrid of the Cow bone and Groundnut shell (HGSCB) reinforce
with epoxy was also prepared. The mechanical properties of the
developed composites were investigated. Optical microscopy was
used to examine the microstructure of the composites. The results
revealed that mechanical properties did not increase uniformly with
additions in filler but exhibited maximum properties at specific
percentages of filler additions. From the Microscopic evaluation, it
was discovered that homogeneity decreases with increase in % filler,
this could be due to poor interfacial bonding.
Abstract: The main purpose of this study is static analysis of
two three-degree of freedom parallel mechanisms: 3-RCC and 3-
RRS. Geometry of these mechanisms is expressed and static
equilibrium equations are derived for the whole chains. For these
mechanisms due to the equal number of equations and unknowns, the
solution is as same as 3-RCC mechanism. A mathematical software is
used to solve the equations. In order to prove the results obtained
from solving the equations of mechanisms, the CAD model of these
robots has been simulated and their static is analysed in ADAMS
software. Due to symmetrical geometry of the mechanisms, the force
and external torque acting on the end-effecter have been considered
asymmetric to prove the generality of the solution method. Finally,
the results of both softwares, for both mechanisms are extracted and
compared as graphs. The good achieved comparison between the
results indicates the accuracy of the analysis.
Abstract: Construction and reconstruction of settlements and
individual municipalities, environmental management and the
creation, deployment of the forces of production and building
transport and technical equipment requires a large expenditure of
material and human resources. That is why the economic aspects of
the majority decision in these planes built in the foreground and are
often decisive. Thereby but more serious is that the economic aspects
of the settlement, the creation and function remain in their whole,
unprocessed, and cannot speak of a set of individual techniques and
methods traditional indicators and experiments with new approaches.
This is true both at the level of the national economy, and in their
own urban designs. Still a few remain identified specific economic
shaping patterns of settlement and the less it is possible to speak of
their control. Also practical assessing economics of specific solutions
are often used non-apt indicators in addition to economics usually
identifies with the lowest acquisition cost or high-intensity land use
with little regard for functional efficiency and little studied much
higher operating and maintenance costs".
Abstract: The notion of power and gender domination is one of
the inseparable aspects of themes in postmodern literature. The
reason of its importance has been discussed frequently since the rise
of Michel Foucault and his insight into the circulation of power and
the transgression of forces. Language and society operate as the basic
grounds for the study, as all human beings are bound to the set of
rules and norms which shape them in the acceptable way in the
macrocosm. How different genders in different positions behave and
show reactions to the provocation of social forces and superiority of
one another is of great interest to writers and literary critics. Mamet’s
works are noticeable for their controversial but timely themes which
illustrate human conflicts with the society and greed for power. Many
critics like Christopher Bigsby and Harold Bloom have discussed
Mamet and his ideas in recent years. This paper is the study of
Oleanna, Mamet’s masterpiece about the teacher-student relationship
and the circulation of power between a man and woman. He shows
the very breakable boundaries in the domination of a gender and the
downfall of speech as the consequence of transgression and freedom.
The failure of the language the teacher uses and the abuse of his own
words by a student who seeks superiority and knowledge are the
main subjects of the discussion. Supported by the ideas of Foucault,
the language Mamet uses to present his characters becomes the
fundamental premise in this study. As a result, language becomes
both the means of achievement and downfall.
Abstract: We report herein the development and preliminary mechanical characterization of fully-dense multi-wall carbon nanotube (MWCNT)-reinforced ceramics and glasses based on a completely new methodology termed High Shear Compaction (HSC). The tubes are introduced and bound to the matrix grains by aid of polymeric binders to form flexible green bodies which are sintered and densified by spark plasma sintering to unprecedentedly high densities of 100% of the pure-matrix value. The strategy was validated across a PyrexTM glass / MWCNT composite while no identifiable factors limit application to other types of matrices. Nondestructive evaluation, based on ultrasonics, of the dynamic mechanical properties of the materials including elastic, shear and bulk modulus as well as Poisson’s ratio showed optimum property improvement at 0.5 %wt tube loading while evidence of nanoscalespecific energy dissipative characteristics acting complementary to nanotube bridging and pull-out indicate a high potential in a wide range of reinforcing and multifunctional applications.
Abstract: In the present study, response surface methodology has been used to optimize turn-assisted deep cold rolling process of AISI 4140 steel. A regression model is developed to predict surface hardness and surface roughness using response surface methodology and central composite design. In the development of predictive model, deep cold rolling force, ball diameter, initial roughness of the workpiece, and number of tool passes are considered as model variables. The rolling force and the ball diameter are the significant factors on the surface hardness and ball diameter and numbers of tool passes are found to be significant for surface roughness. The predicted surface hardness and surface roughness values and the subsequent verification experiments under the optimal operating conditions confirmed the validity of the predicted model. The absolute average error between the experimental and predicted values at the optimal combination of parameter settings for surface hardness and surface roughness is calculated as 0.16% and 1.58% respectively. Using the optimal processing parameters, the surface hardness is improved from 225 to 306 HV, which resulted in an increase in the near surface hardness by about 36% and the surface roughness is improved from 4.84µm to 0.252 µm, which resulted in decrease in the surface roughness by about 95%. The depth of compression is found to be more than 300µm from the microstructure analysis and this is in correlation with the results obtained from the microhardness measurements. Taylor hobson talysurf tester, micro vickers hardness tester, optical microscopy and X-ray diffractometer are used to characterize the modified surface layer.
Abstract: Given the limited research on Small and Mediumsized
Enterprises’ (SMEs) contribution to Corporate Social
Responsibility (CSR) and even scarcer research on Swiss SMEs, this
paper helps to fill these gaps by enabling the identification of supranational
SME parameters. Thus, the paper investigates the current
state of SME practices in Switzerland and across 15 other countries.
Combining the degree to which SMEs demonstrate an explicit (or
business case) approach or see CSR as an implicit moral activity with
the assessment of their attributes for “variety of capitalism” defines
the framework of this comparative analysis. To outline Swiss small
business CSR patterns in particular, 40 SME owner-managers were
interviewed. A secondary data analysis of studies from different
countries laid groundwork for this comparative overview of small
business CSR. The paper identifies Swiss small business CSR as
driven by norms, values, and by the aspiration to contribute to
society, thus, as an implicit part of the day-to-day business. Similar to
most Central European, Mediterranean, Nordic, and Asian countries,
explicit CSR is still very rare in Swiss SMEs. Astonishingly, also
British and American SMEs follow this pattern in spite of their strong
and distinctly liberal market economies. Though other findings show
that nationality matters this research concludes that SME culture and
an informal CSR agenda are strongly formative and superseding even
forces of market economies, nationally cultural patterns, and
language. Hence, classifications of countries by their market system,
as found in the comparative capitalism literature, do not match the
CSR practices in SMEs as they do not mirror the peculiarities of their
business. This raises questions on the universality and
generalisability of unmediated, explicit management concepts,
especially in the context of small firms.
Abstract: Boiling process is characterized by the rapid
formation of vapour bubbles at the solid–liquid interface (nucleate
boiling) with pre-existing vapour or gas pockets. Computational fluid
dynamics (CFD) is an important tool to study bubble dynamics. In
the present study, CFD simulation has been carried out to determine
the bubble detachment diameter and its terminal velocity. Volume of
fluid method is used to model the bubble and the surrounding by
solving single set of momentum equations and tracking the volume
fraction of each of the fluids throughout the domain. In the
simulation, bubble is generated by allowing water-vapour to enter a
cylinder filled with liquid water through an inlet at the bottom. After
the bubble is fully formed, the bubble detaches from the surface and
rises up during which the bubble accelerates due to the net balance
between buoyancy force and viscous drag. Finally when these forces
exactly balance each other, it attains a constant terminal velocity. The
bubble detachment diameter and the terminal velocity of the bubble
are captured by the monitor function provided in FLUENT. The
detachment diameter and the terminal velocity obtained are compared
with the established results based on the shape of the bubble. A good
agreement is obtained between the results obtained from simulation
and the equations in comparison with the established results.
Abstract: There is not much effective guideline on development of design parameters selection on spring back for advanced high strength steel sheet metal in U-channel process during cold forming process. This paper presents the development of predictive model for spring back in U-channel process on advanced high strength steel sheet employing Response Surface Methodology (RSM). The experimental was performed on dual phase steel sheet, DP590 in Uchannel forming process while design of experiment (DoE) approach was used to investigates the effects of four factors namely blank holder force (BHF), clearance (C) and punch travel (Tp) and rolling direction (R) were used as input parameters using two level values by applying Full Factorial design (24 ). From a statistical analysis of variant (ANOVA), result showed that blank holder force (BHF), clearance (C) and punch travel (Tp) displayed significant effect on spring back of flange angle (β2 ) and wall opening angle (β1 ), while rolling direction (R) factor is insignificant. The significant parameters are optimized in order to reduce the spring back behavior using Central Composite Design (CCD) in RSM and the optimum parameters were determined. A regression model for spring back was developed. The effect of individual parameters and their response was also evaluated. The results obtained from optimum model are in agreement with the experimental values.
Abstract: Steady three-dimensional and two free surface waves
generated by moving bodies are presented, the flow problem to be
simulated is rich in complexity and poses many modeling challenges
because of the existence of breaking waves around the ship hull, and
because of the interaction of the two-phase flow with the turbulent
boundary layer. The results of several simulations are reported. The
first study was performed for NACA0012 of hydrofoil with different
meshes, this section is analyzed at h/c= 1, 0345 for 2D. In the second
simulation a mathematically defined Wigley hull form is used to
investigate the application of a commercial CFD code in prediction of
the total resistance and its components from tangential and normal
forces on the hull wetted surface. The computed resistance and wave
profiles are used to estimate the coefficient of the total resistance for
Wigley hull advancing in calm water under steady conditions. The
commercial CFD software FLUENT version 12 is used for the
computations in the present study. The calculated grid is established
using the code computer GAMBIT 2.3.26. The shear stress k-ωSST
model is used for turbulence modeling and the volume of fluid
technique is employed to simulate the free-surface motion. The
second order upwind scheme is used for discretizing the convection
terms in the momentum transport equations, the Modified HRIC
scheme for VOF discretization. The results obtained compare well
with the experimental data.