Abstract: A thin layer on the component surface can be found
with high tensile residual stresses, due to turning operations, which
can dangerously affect the fatigue performance of the component. In
this paper an analytical approach is presented to reconstruct the
residual stress field from a limited incomplete set of measurements.
Airy stress function is used as the primary unknown to directly solve
the equilibrium equations and satisfying the boundary conditions. In
this new method there exists the flexibility to impose the physical
conditions that govern the behavior of residual stress to achieve a
meaningful complete stress field. The analysis is also coupled to a
least squares approximation and a regularization method to provide
stability of the inverse problem. The power of this new method is
then demonstrated by analyzing some experimental measurements
and achieving a good agreement between the model prediction and
the results obtained from residual stress measurement.
Abstract: Fatigue life prediction and evaluation are the key
technologies to assure the safety and reliability of automotive rubber
components. The objective of this study is to develop the fatigue
analysis process for vulcanized rubber components, which is
applicable to predict fatigue life at initial product design step. Fatigue
life prediction methodology of vulcanized natural rubber was
proposed by incorporating the finite element analysis and fatigue
damage parameter of maximum strain appearing at the critical location
determined from fatigue test. In order to develop an appropriate
fatigue damage parameter of the rubber material, a series of
displacement controlled fatigue test was conducted using threedimensional
dumbbell specimen with different levels of mean
displacement. It was shown that the maximum strain was a proper
damage parameter, taking the mean displacement effects into account.
Nonlinear finite element analyses of three-dimensional dumbbell
specimens were performed based on a hyper-elastic material model
determined from the uni-axial tension, equi-biaxial tension and planar
test. Fatigue analysis procedure employed in this study could be used
approximately for the fatigue design.
Abstract: The paper deals with the effect of ion nitriding and
carbonitriding on fatigue strength of steel parts under the fretting
conditions. Instrumented fatigue tests were carried out on surface
treated flat bars from EA1N and EA4T steels with different strength.
The chosen surfacing decrease importantly an unfavorable fretting
effect. Nitridation suppressed the unfavorable effect of fretting
almost entirely, while the influence of carbonitridation was less
striking. The results were compared with those ones obtained on bars
without surfacing. The causes of favorable influence of surfacing are
discussed.
Abstract: In elevating performance in competetive sports, an
athlete must continously train in achieving maximum
performance,but needs to pay attention to recovery therapy, that is to
recover from fatigue as well as injury.The correct recovery therapy
will assist in process of recovery and helps in the training in
achieving better performace. Binahong (Anredera cordifolia) was
proven empirically by the locals in assisting speedy recovery from an
injury.Clinical research with lab animals receiving blunt trauma
injury, microscopically shown signs of: 1) redness, 2) heatiness, 3)
swelling and, 4) lack of activity. There is also microscopic indication
of: 1) infiltration of inflame cells (migration of cells to the trauma
area), 2) Cells necrosis, 3) Congestion (as a result of dead red blood
cells), 4) uedema. On administration of Binahong for 3 days, there is
a significant drop of 5% in cell inflammation, 2% increase of
fibroblast (cell membrance) count.Conclutin: Binahong do assist in
reducing cell inflammation and increase counts of cells fibroblast.
Suggestion: In helping athlete's to recover from force injury, we need
study about Binahong's roots to inflammation cell and healing of
injuried cell.
Abstract: A method is presented for using thermo-mechanical fatigue analysis as a tool in the design of automotive heat exchangers. Use of infra-red thermography to measure the real thermal history in the heat exchanger reduces the time necessary for calculating design parameters and improves prediction accuracy. Thermal shocks are the primary cause of heat exchanger damage. Thermo-mechanical simulation is based on the mean behavior of the aluminum tubes used in the heat exchanger. An energetic fatigue criterion is used to detect critical zones.
Abstract: In this paper, some common gearboxes vibration analysis methods and condition monitoring systems are explained. In addition, an experimental gearbox vibration analysis is discussed through a critical case history for a mixer gearbox related to Iran oil industry. The case history also consists of gear manufacturing (machining) recommendations, lubrication condition of gearbox and machinery maintenance activities that caused reduction in noise and vibration of the gearbox. Besides some of the recent patents and innovations in gearboxes, lubrication and vibration monitoring systems explained. Finally micro pitting and surface fatigue in pinion and bevel of mentioned horizontal to vertical gearbox discussed in details.
Abstract: Fatigue behaviors of Lead Zirconate Titanate (PZT)
ceramics under different amplitude of bipolar electrical loads have
been investigated. Fatigue behavior is represented by the change of
hysteresis loops and remnant polarization. Three levels of electrical
load amplitudes (1.00, 1.25 and 1.50 kV /mm) were applied in this
experimental. It was found that the remnant polarization decreased
significantly with the number of loading cycles. The degree of fatigue
degradation depends on the amplitude of electric field. The higher
amplitude exhibits the greater fatigue degradation.
Abstract: This paper focuses on developing an integrated
reliable and sophisticated model for ultra large wind turbines And to
study the performance and analysis of vector control on large wind
turbines. With the advance of power electronics technology, direct
driven multi-pole radial flux PMSG (Permanent Magnet Synchronous
Generator) has proven to be a good choice for wind turbines
manufacturers. To study the wind energy conversion systems, it is
important to develop a wind turbine simulator that is able to produce
realistic and validated conditions that occur in real ultra MW wind
turbines. Three different packages are used to simulate this model,
namely, Turbsim, FAST and Simulink. Turbsim is a Full field wind
simulator developed by National Renewable Energy Laboratory
(NREL). The wind turbine mechanical parts are modeled by FAST
(Fatigue, Aerodynamics, Structures and Turbulence) code which is
also developed by NREL. Simulink is used to model the PMSG, full
scale back to back IGBT converters, and the grid.
Abstract: Improvement in CAE methods has an important role for shortening of the vehicle product development time. It is provided that validation of the design and improvements in terms of durability can be done without hardware prototype production. In recent years, several different methods have been developed in order to investigate fatigue damage of the vehicle. The intended goal among these methods is prediction of fatigue damage in a short time with reduced costs. This study developed a new fatigue damage prediction method in the automotive sector using power spectrum densities of accelerations. This study also confirmed that the weak region in vehicle can be easily detected with the method developed in this study which results were compared with conventional method.
Abstract: In this work, bending fatigue life of notched
specimens with various notch geometries and dimensions is
investigated by experiment and Manson-Caffin theoretical method. In
this theoretical method, fatigue life of notched specimens is
calculated using the fatigue life obtained from the experiments for
plain specimens (without notch). Three notch geometries including
∪-shape, ∨-shape and C -shape notches are considered in this
investigation. The experiments are conducted on a rotary bending
Moore machine. The specimens are made of a low carbon steel alloy,
which has wide application in industry. The stress- life curves are
captured for all notched specimen by experiment. The results indicate
that Manson-Caffin analytical method cannot adequately predict
the fatigue life of notched specimen. However, it seems that the
difference between the experiments and Manson-Caffin predictions
can be compensated by a proportional factor.
Abstract: High precision in motion is required to manipulate the
micro objects in precision industries for micro assembly, cell
manipulation etc. Precision manipulation is achieved based on the
appropriate mechanism design of micro devices such as
microgrippers. Design of a compliant based mechanism is the better
option to achieve a highly precised and controlled motion. This
research article highlights the method of designing a compliant based
three fingered microgripper suitable for holding asymmetric objects.
Topological optimization technique, a systematic method is
implemented in this research work to arrive a topologically optimized
design of the mechanism needed to perform the required micro
motion of the gripper. Optimization technique has a drawback of
generating senseless regions such as node to node connectivity and
staircase effect at the boundaries. Hence, it is required to have post
processing of the design to make it manufacturable. To reduce the
effect of post processing stage and to preserve the edges of the image,
a cubic spline interpolation technique is introduced in the MATLAB
program. Structural performance of the topologically developed
mechanism design is tested using finite element method (FEM)
software. Further the microgripper structure is examined to find its
fatigue life and vibration characteristics.
Abstract: Single-pole switching scheme is widely used in the
Extra High Voltage system. However, the substantial negativesequence
current injected to the turbine-generators imposes the
electromagnetic (E/M) torque of double system- frequency
components during the dead time (between single-pole clearing and
line reclosing). This would induce supersynchronous resonance
(SPSR) torque amplifications on low pressure turbine generator
blades and even lead to fatigue damage. This paper proposes the
design of a mechanical filter (MF) with natural frequency close to
double-system frequency. From the simulation results, it is found that
such a filter not only successfully damps the resonant effect, but also
has the characteristics of feasibility and compact.
Abstract: In this paper fatigue crack growth behavior of
aeronautical aluminum alloy 2024 T351 was studied. Effects of
various loading and geometrical parameters are studied such as stress
ratio, amplitude loading, etc. The fatigue crack growth with constant
amplitude is studied using the AFGROW code when NASGRO
model is used. The effect of the stress ratio is highlighted, where one
notices a shift of the curves of crack growth. The comparative study
between two orientations L-T and T-L on fatigue behavior are
presented and shows the variation on the fatigue life. L-T orientation
presents a good fatigue crack growth resistance. Effects of crack
closure are shown in Paris domain and that no crack closure
phenomenons are present at high stress intensity factor.
Abstract: One approach to assess neural networks underlying the cognitive processes is to study Electroencephalography (EEG). It is relevant to detect various mental states and characterize the physiological changes that help to discriminate two situations. That is why an EEG (amplitude, synchrony) classification procedure is described, validated. The two situations are "eyes closed" and "eyes opened" in order to study the "alpha blocking response" phenomenon in the occipital area. The good classification rate between the two situations is 92.1 % (SD = 3.5%) The spatial distribution of a part of amplitude features that helps to discriminate the two situations are located in the occipital regions that permit to validate the localization method. Moreover amplitude features in frontal areas, "short distant" synchrony in frontal areas and "long distant" synchrony between frontal and occipital area also help to discriminate between the two situations. This procedure will be used for mental fatigue detection.
Abstract: End milling process is one of the common metal
cutting operations used for machining parts in manufacturing
industry. It is usually performed at the final stage in manufacturing a
product and surface roughness of the produced job plays an
important role. In general, the surface roughness affects wear
resistance, ductility, tensile, fatigue strength, etc., for machined parts
and cannot be neglected in design. In the present work an
experimental investigation of end milling of aluminium alloy with
carbide tool is carried out and the effect of different cutting
parameters on the response are studied with three-dimensional
surface plots. An artificial neural network (ANN) is used to establish
the relationship between the surface roughness and the input cutting
parameters (i.e., spindle speed, feed, and depth of cut). The Matlab
ANN toolbox works on feed forward back propagation algorithm is
used for modeling purpose. 3-12-1 network structure having
minimum average prediction error found as best network architecture
for predicting surface roughness value. The network predicts surface
roughness for unseen data and found that the result/prediction is
better. For desired surface finish of the component to be produced
there are many different combination of cutting parameters are
available. The optimum cutting parameter for obtaining desired
surface finish, to maximize tool life is predicted. The methodology is
demonstrated, number of problems are solved and algorithm is coded
in Matlab®.
Abstract: The intention of this study to design the probability optimized sewing sack-s workstation based on ergonomics for productivity improvement and decreasing musculoskeletal disorders. The physical dimensions of two workers were using to design the new workstation. The physical dimensions are (1) sitting height, (2) mid shoulder height sitting, (3) shoulder breadth, (4) knee height, (5) popliteal height, (6) hip breadth and (7) buttock-knee length. The 5th percentile of buttock knee length sitting (51 cm), the 50th percentile of mid shoulder height sitting (62 cm) and the 95th percentile of popliteal height (43 cm) and hip breadth (45 cm) applied to design the workstation for sewing sack-s operator and the others used to adjust the components of this workstation. The risk assessment by RULA before and after using the probability optimized workstation were 7 and 7 scores and REBA scores were 11 and 5, respectively. Body discomfort-abnormal index was used to assess muscle fatigue of operators before adjustment workstation found that neck muscles, arm muscles area, muscles on the back and the lower back muscles fatigue. Therefore, the extension and flexion exercise was applied to relief musculoskeletal stresses. The workers exercised 15 minutes before the beginning and the end of work for 5 days. After that, the capability of flexion and extension muscles- workers were increasing in 3 muscles (arm, leg, and back muscles).
Abstract: The presence of a vertical fatigue crack in the web of
a plate girder subjected to pure bending influences the bending
moment capacity of the girder. The growth of the crack may lead to
premature elastic failure due to flange local yielding, flange local
buckling, or web local buckling. Approximate expressions for the
bending moment capacities corresponding to these failure modes
were formulated. Finite element analyses were then used to validate
the expressions. The expressions were employed to assess the effects
of crack length on the capacity. Neglecting brittle fracture, tension
buckling, and ductile failure modes, it was found that typical girders
are governed by the capacity associated with flange local yielding as
influenced by the crack. Concluding, a possible use of the capacity
expressions in girder design was demonstrated.
Abstract: Aiming at most of the aviation products are facing the problem of fatigue fracture in vibration environment, we makes use of the testing result of a bracket, analysis for the structure with ANSYS-Workbench, predict the life of the bracket by different ways, and compared with the testing result. With the research on analysis methods, make an organic combination of simulation analysis and testing, Not only ensure the accuracy of simulation analysis and life predict, but also make a dynamic supervision of product life process, promote the application of finite element simulation analysis in engineering practice.
Abstract: This paper reports the fatigue crack growth behaviour
of gas tungsten arc, electron beam and laser beam welded Ti-6Al-4V
titanium alloy. Centre cracked tensile specimens were prepared to
evaluate the fatigue crack growth behaviour. A 100kN servo
hydraulic controlled fatigue testing machine was used under constant
amplitude uniaxial tensile load (stress ratio of 0.1 and frequency of
10 Hz). Crack growth curves were plotted and crack growth
parameters (exponent and intercept) were evaluated. Critical and
threshold stress intensity factor ranges were also evaluated. Fatigue
crack growth behaviour of welds was correlated with mechanical
properties and microstructural characteristics of welds. Of the three
joints, the joint fabricated by laser beam welding exhibited higher
fatigue crack growth resistance due to the presence of fine lamellar
microstructure in the weld metal.
Abstract: The turbulent mixing of coolant streams of different
temperature and density can cause severe temperature fluctuations in
piping systems in nuclear reactors. In certain periodic contraction
cycles these conditions lead to thermal fatigue. The resulting aging
effect prompts investigation in how the mixing of flows over a sharp
temperature/density interface evolves. To study the fundamental
turbulent mixing phenomena in the presence of density gradients,
isokinetic (shear-free) mixing experiments are performed in a square
channel with Reynolds numbers ranging from 2-500 to 60-000.
Sucrose is used to create the density difference. A Wire Mesh Sensor
(WMS) is used to determine the concentration map of the flow in the
cross section. The mean interface width as a function of velocity,
density difference and distance from the mixing point are analyzed
based on traditional methods chosen for the purposes of
atmospheric/oceanic stratification analyses. A definition of the
mixing layer thickness more appropriate to thermal fatigue and based
on mixedness is devised. This definition shows that the thermal
fatigue risk assessed using simple mixing layer growth can be
misleading and why an approach that separates the effects of large
scale (turbulent) and small scale (molecular) mixing is necessary.