Abstract: The stiffness of the workpiece is very important to reduce the errors in manufacturing process. The high stiffness of the workpiece can be achieved by optimal positioning of fixture elements in the fixture. The minimization of the sum of the nodal deflection normal to the surface is used as objective function in previous research. The deflection in other direction has been neglected. The 3-2-1 fixturing principle is not valid for metal sheets due to its flexible nature. We propose a new fixture layout optimization method N-3-2-1 for metal sheets that uses the strain energy of the finite elements. This method combines the genetic algorithm and finite element analysis. The objective function in this method is to minimize the sum of all the element strain energy. By using the concept of element strain energy, the deformations in all the directions have been considered. Strain energy and stiffness are inversely proportional to each other. So, lower the value of strain energy, higher will be the stiffness. Two different kinds of case studies are presented. The case studies are solved for both objective functions; element strain energy and nodal deflection. The result are compared to verify the propose method.
Abstract: There is a growing interest in the use of ultrasonic speckle tracking for biomedical image formation of tissue deformation. Speckle tracking is angle independent and has an ability to differentiate soft tissue into benign and malignant regions. In this paper a simulation model for dynamic ultrasound scatterer is presented. The model composes Field-II ultrasonic scatterers and FEM (ANSYS-11) nodes as a regional tissue deformation. A performance evaluation is presented on axial displacement and strain fields estimation of a uniformly elastic model, using speckle tracking based 1D cross-correlation of optimally segmented pre and post-deformation frames. Optimum correlation window length is investigated in terms of highest signal-to-noise ratio (SNR) for a selected region of interest of a smoothed displacement field. Finally, gradient based strain field of both smoothed and non-smoothed displacement fields are compared. Simulation results from the model are shown to compare favorably with FEM results.
Abstract: The curvature space-time by the presence of material, this deformation must present a pattern of deformation, not random. Space is uniform, elastic and any modification that occurs in one part, causes a change in another.
This deformation exists, must be a constant value and is independent of the observer, and relates the amount of matter, the force caused by the curvature of space and surface space. This unit of space is defined in this study as PIL and represents a constant area of space, deformable in the direction and sense of the center of mass of the body. The PIL is curved and connected to the center of mass of the Earth, to get to that point, through all matter, thus forming part of any place between particles at atomic and subatomic levels. At these levels the space between each particle is flat, unlike the macro where the space curves.
Abstract: Axial compression tests are performed on circular tubes made of Aluminum EN AW 6060 (AlMgSi0.5 alloy) in T66 state. All the received tubes have the uniform outer diameter of 40mm and thickness of 1.5mm. Two different lengths 100mm and 200mm are used in the analysis. After performing compression tests on the uniform tube, important crashworthy parameters like peak force, average force, crush efficiency and energy absorption are measured. The present paper has given importance to increase the percentage of crush efficiency without decreasing the value energy absorption of a tube, so a circumferential notch was introduced on the top section of the tube. The effects of position and cut-out lengths of a circumferential notch on the crush efficiency are well explained with relative deformation modes and force-displacement curves. The numerical simulations were carried on the software tool ANSYS/LS-DYNA. It is seen that the numerical results are reasonably good in agreement with the experimental results.
Abstract: It can be determined in preference between
representative mechanical and mathematical model of elasticcreeping
deformation of transversally isotropic array with doubly
periodic system of tilted slots, and offer of the finite elements
calculation scheme, and inspection of the states of two diagonal
arbitrary profile cavities of deep inception, and in setting up the tense
and dislocation fields distribution nature in computing processes.
Abstract: In this paper a study on the vibration of thin
cylindrical shells with ring supports and made of functionally
graded materials (FGMs) composed of stainless steel and
nickel is presented. Material properties vary along the
thickness direction of the shell according to volume fraction
power law. The cylindrical shells have ring supports which are
arbitrarily placed along the shell and impose zero lateral
deflections. The study is carried out based on third order shear
deformation shell theory (T.S.D.T). The analysis is carried out
using Hamilton-s principle. The governing equations of motion of
FGM cylindrical shells are derived based on shear deformation
theory. Results are presented on the frequency characteristics,
influence of ring support position and the influence of boundary
conditions. The present analysis is validated by comparing results
with those available in the literature.
Abstract: Superelastic Shape Memory Alloy (SMA) is accepted
when it used as connection in steel structures. The seismic behaviour
of steel frames with SMA is being assessed in this study. Three eightstorey
steel frames with different SMA systems are suggested, the
first one of which is braced with diagonal bracing system, the second
one is braced with nee bracing system while the last one is which the
SMA is used as connection at the plastic hinge regions of beams.
Nonlinear time history analyses of steel frames with SMA subjected
to two different ground motion records have been performed using
Seismostruct software. To evaluate the efficiency of suggested
systems, the dynamic responses of the frames were compared. From
the comparison results, it can be concluded that using SMA element
is an effective way to improve the dynamic response of structures
subjected to earthquake excitations. Implementing the SMA braces
can lead to a reduction in residual roof displacement. The shape
memory alloy is effective in reducing the maximum displacement at
the frame top and it provides a large elastic deformation range. SMA
connections are very effective in dissipating energy and reducing the
total input energy of the whole frame under severe seismic ground
motion. Using of the SMA connection system is more effective in
controlling the reaction forces at the base frame than other bracing
systems. Using SMA as bracing is more effective in reducing the
displacements. The efficiency of SMA is dependant on the input
wave motions and the construction system as well.
Abstract: The orthogonal processes to shape the triangle steel plate into a equilateral vertical steel are examined by an incremental elasto-plastic finite-element method based on an updated Lagrangian formulation. The highly non-linear problems due to the geometric changes, the inelastic constitutive behavior and the boundary conditions varied with deformation are taken into account in an incremental manner. On the contact boundary, a modified Coulomb friction mode is specially considered. A weighting factor r-minimum is employed to limit the step size of loading increment to linear relation. In particular, selective reduced integration was adopted to formulate the stiffness matrix. The simulated geometries of verticality could clearly demonstrate the vertical processes until unloading. A series of experiments and simulations were performed to validate the formulation in the theory, leading to the development of the computer codes. The whole deformation history and the distribution of stress, strain and thickness during the forming process were obtained by carefully considering the moving boundary condition in the finite-element method. Therefore, this modeling can be used for judging whether a equilateral vertical steel can be shaped successfully. The present work may be expected to improve the understanding of the formation of the equilateral vertical steel.
Abstract: Contact stress is an important problem in industry.
This is a problem that in the first attention may be don-t appears, but
disregard of these stresses cause a lot of damages in machines. These
stresses occur at locations such as gear teeth, bearings, cams and
between a locomotive wheel and the railroad rail. These stresses
cause failure by excessive elastic deformation, yielding and fracture.
In this paper we intend show the effective parameters in contact
stress and ponder effect of curvature. In this paper we study contact
stresses on the surface of gear teeth and compare these stresses for
four popular profiles of gear teeth (involute, cycloid, epicycloids, and
hypocycloid). We study this problem with mathematical and finite
element methods and compare these two methods on different profile
surfaces.
Abstract: In the present work, study of the vibration of thin cylindrical shells made of a functionally gradient material (FGM) composed of stainless steel and nickel is presented. Material properties are graded in the thickness direction of the shell according to volume fraction power law distribution. The objective is to study the natural frequencies, the influence of constituent volume fractions and the effects of boundary conditions on the natural frequencies of the FG cylindrical shell. The study is carried out using third order shear deformation shell theory. The governing equations of motion of FG cylindrical shells are derived based on shear deformation theory. Results are presented on the frequency characteristics, influence of constituent volume fractions and the effects of free-free boundary conditions.
Abstract: To enhance installation security, a LNG storage in Rudong of Jiangsu province was adopted as a practical work, and it was analyzed by nonlinear finite element method to research overall and local stability performance, as well as the stress and deformation under the action of wind load and self-weight. Results indicate that deformation is tiny when steel mesh maintains as an overall ring, and stress caused by vertical bending moment and tension of bottom tie wire are also in the safe range. However, axial forces of lap reinforcement in adjacent steel mesh exceed the ultimate bearing capacity of tie wire. Hence, tie wires are ruptured; single mesh loses lateral connection and turns into monolithic status as the destruction of overall structure. Further more, monolithic steel mesh is led to collapse by the damage of bottom connection. So, in order to prevent connection failure and enhance installation security, the overlapping parts of steel mesh should be taken more reliable measures.
Abstract: This paper aims to present the design, fabrication and test of a novel piezoelectric actuated, check-valves embedded micropump having the advantages of miniature size, light weight and low power consumption. This device is designed to pump gases and liquids with the capability of performing the self-priming and bubble-tolerant work mode by maximizing the stroke volume of the membrane as well as the compression ratio via minimization of the dead volume of the micropump chamber and channel. By experiment apparatus setup, we can get the real-time values of the flow rate of micropump, the displacement of the piezoelectric actuator and the deformation of the check valve, simultaneously. The micropump with check valve 0.4 mm in thickness obtained higher output performance under the sinusoidal waveform of 120 Vpp. The micropump achieved the maximum pumping rates of 42.2 ml/min and back pressure of 14.0 kPa at the corresponding frequency of 28 and 20 Hz. The presented micropump is able to pump gases with a pumping rate of 196 ml/min at operating frequencies of 280 Hz under the sinusoidal waveform of 120 Vpp.
Abstract: The migration of a deformable drop in simple shear
flow at finite Reynolds numbers is investigated numerically by
solving the full Navier-Stokes equations using a finite
difference/front tracking method. The objectives of this study are to
examine the effectiveness of the present approach to predict the
migration of a drop in a shear flow and to investigate the behavior of
the drop migration with different drop sizes and non-unity viscosity
ratios. It is shown that the drop deformation depends strongly on the
capillary number, so that; the proper non-dimensional number for the
interfacial tension is the capillary number. The rate of migration
increased with increasing the drop radius. In other words, the
required time for drop migration to the centreline decreases. As the
viscosity ratio increases, the drop rotates more slowly and the
lubrication force becomes stronger. The increased lubrication force
makes it easier for the drop to migrate to the centre of the channel.
The migration velocity of the drop vanishes as the drop reaches the
centreline under viscosity ratio of one and non-unity viscosity ratios.
To validate the present calculations, some typical results are
compared with available experimental and theoretical data.
Abstract: Polypropylene blended with natural oil and pigment additives has been studied. Different formulations for each compound were made into polybag used for cultivation of oil palm seedlings for strength and mechanical properties studies. One group of sample was exposed under normal sunlight to initiate degradation and another group of sample was placed under shaded area for five months. All samples were tested for tensile strength to determine the degradation effects. The tensile strength of directly exposed sunlight samples and shaded area showed up to 50% and 25% degradation respectively. However, similar reduction of Young’s modulus for all samples was found for both exposures. Structural investigations were done using FTIR to detect deformation. The natural additives that were used in the studies were all natural and environmental friendly
Abstract: Spatial understanding and the understanding of
dynamic change in the spatial structure of molecules during a
reaction is essential for designing new molecules. Knowing the
physical processes in the reactions helps to speed up the designing
process. To support the designer with the correct representation of
the designed molecule as well as showing the dynamic behavior of
the whole reacting system is the goal of our application. Our system
shows the spatial deformation of the molecules at every time interval
by minimizing the energy level of the molecules. The position and
orientation of the molecules can be intuitively controlled by
manipulating objects of the real world using Augmented Reality
techniques. Our approach has the potential to speed up the design of
new molecules and help students to understand the chemical
processes better.
Abstract: According to Rostler method (ASTM D 2006), saturates content of bitumen is determined based on its reactivity to sulphuric acid. While Corbett method (ASTM D 4124) based on its polarity level. This paper presents results from the study on the effect of saturates content determined by two different fractionation methods on the rheological and aging characteristics of bitumen. The result indicated that the increment of saturates content tended to reduce all the rheological characteristics concerned. Bitumen became less elastic, less viscous, and less resistant to plastic deformation, but became more resistant to fatigue cracking. After short and long term aging process, the treatment effect coefficients of saturates decreased, saturates became thicker due to aging process. This study concludes that saturates is not really stable or reactive in aging process. Therefore, the reactivity of saturates should be considered in bitumen aging index
Abstract: Two geometrically nonlinear plate theories, based either on first- or third-order transverse shear deformation theory are used for finite element modeling and simulation of the transient response of smart structures incorporating piezoelectric layers. In particular the time histories of nonlinear vibrations and sensor voltage output of a thin beam with a piezoelectric patch bonded to the surface due to an applied step force are studied.
Abstract: Excessive ductility demand on shorter piers is a
common problem for irregular bridges subjected to strong ground
motion. Various techniques have been developed to reduce the
likelihood of collapse of bridge due to failure of shorter piers. This
paper presents the new approach to improve the seismic behavior of
such bridges using Nitinol shape memory alloys (SMAs).
Superelastic SMAs have the ability to remain elastic under very large
deformation due to martensitic transformation. This unique property
leads to enhanced performance of controlled bridge compared with
the performance of the reference bridge. To evaluate the effectiveness
of the devices, nonlinear time history analysis is performed on a RC
single column bent highway bridge using a suite of representative
ground motions. The results show that this method is very effective in
limiting the ductility demand of shorter pier.
Abstract: Use of a sliding joint is an effective method to
decrease the stress in foundation structure where there is a horizontal
deformation of subsoil (areas afflicted with underground mining) or
horizontal deformation of a foundation structure (pre-stressed
foundations, creep, shrinkage, temperature deformation). A
convenient material for a sliding joint is a bitumen asphalt belt.
Experiments for different types of bitumen belts were undertaken at
the Faculty of Civil Engineering - VSB Technical University of
Ostrava in 2008. This year an extension of the 2008 experiments is in
progress and the shear resistance of a slide joint is being tested as a
function of temperature in a temperature controlled room. In this
paper experimental results of temperature dependant shear resistance
are presented. The result of the experiments should be the sliding
joint shear resistance as a function of deformation velocity and
temperature. This relationship is used for numerical analysis of
stress/strain relation between foundation structure and subsoil. Using
a rheological slide joint could lead to a decrease of the reinforcement
amount, and contribute to higher reliability of foundation structure
and thus enable design of more durable and sustainable building
structures.
Abstract: Bumpers play an important role in preventing the
impact energy from being transferred to the automobile and
passengers. Saving the impact energy in the bumper to be released in
the environment reduces the damages of the automobile and
passengers.
The goal of this paper is to design a bumper with minimum weight
by employing the Glass Material Thermoplastic (GMT) materials.
This bumper either absorbs the impact energy with its deformation or
transfers it perpendicular to the impact direction.
To reach this aim, a mechanism is designed to convert about 80%
of the kinetic impact energy to the spring potential energy and
release it to the environment in the low impact velocity according to
American standard1. In addition, since the residual kinetic energy
will be damped with the infinitesimal elastic deformation of the
bumper elements, the passengers will not sense any impact. It should
be noted that in this paper, modeling, solving and result-s analysis
are done in CATIA, LS-DYNA and ANSYS V8.0 software
respectively.