Abstract: Drillstring in oil drilling is simplified as a half-infinite bar. Taking account of
Peierls-Nabarro(P-N) force and viscous effect of solid, dynamic response is simulated under
harmonic driving at the end of the bar. With the physical properties specified, periodic,
quasi-periodic and chaotic motions would appear as a function of the amplitude of external driving.
We find that all the particles of the bar have the same qualitative characters, while vibrating
amplitude decreases along the bar. It appears that particles of the bar reach chaotic motion through
quasi-periodic motion. Investigation of this half-infinite bar will provide references for design of
drillstring to keep motion away from chaotic region.
Abstract: In the present paper, temperature effect on yield stress of electrorheological fluids is
experimentally investigated. A rotational shear-mode type electroviscometer is designed and
manufactured for the identification of Bingham characteristics of ER fluids. Optimization of ER
fluids is undertaken with carrier liquid, particle and additive treatment and then four different ER
fluids are prepared for the test. The field-dependent yield stress, current density and response time
of optimized ER fluids are compared at various temperature conditions.
Abstract: In this study, the dynamic fatigue characteristics of chemical starch-based ER fluid are
experimentally investigated. A flow mode type apparatus is manufactured to activate the flow motion
of the ER fluid. After evaluating the field-dependent Bingham property, three important dynamic
fatigue characteristics; yield stress, current density and response time of the ER fluid are investigated
as a function of the operating cycle. The dynamic operation for the flow motions is undertaken up to
one million cycles and electric voltage is applied to the electrodes. In addition, the change of the
particles of the ER fluid is microscopically observed to advocate the variation of the yield stress.
Abstract: The interest of the fatigue life for rubber components was increasing according to the
extension of warranty period of the automotive components. In this study, the fatigue lifetime
prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite
element analysis and fatigue damage parameter determined from fatigue tests. Finite element
analysis of 3D dumbbell specimen and rubber component was performed based on a hyper-elastic
material model determined from the mechanical tests. The Green-Lagrange strain at the critical
location determined from the finite element analysis was used for evaluating the fatigue damage
parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens and
rubber component with different levels of maximum strain and various load. Fatigue life curves
can be effectively represented by a following single function using the maximum Green-Lagrange
strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at
the critical location. Predicted fatigue lives of the rubber component for automobile vehicle agreed
fairly with the experimental fatigue lives.
Abstract: External bonding fiber reinforced polymers (FRP) to the tension faces of reinforced
concrete (RC) beam as an effective approach of rehabilitation and strengthening of reinforced
structures have attracted significant interests of researchers in the past decade. Since the
load-carrying capacity of RC beams strengthened with the FRP is dominated by interfacial
delaminated failure, the anchorage strength in FRP to concrete bonded joints under shear and the
debonding stress transferring behavior at the end parts of flexural concrete members bonded with
FRP have been deeply studied. Recently, methods of fracture mechanics have been introduced into
analyzing the above issues. Compared with the traditional methods, the analytical models of
existing fracture mechanics are reviewed and analyzed. Based on them the debonding bearing
capacity of FRP-strengthened RC beams is calculated and the corresponding finite element models
are created. These models of fracture mechanics are then evaluated with the finite element results
and the experimental data from author’s and the literature. Some conclusions with engineering
significance are drawn.
Abstract: Nanostructured spherical lithium manganese oxide (Li-Mn-O) with about 30nm in
diameter was synthesized for the first time by explosive method. The water-solubility explosive was
prepared using a simple facility at room temperature. The growth of lithium manganese oxides via
detonation reaction was investigated with respect to the presence of an energetic precursor, such as
the metallic nitrate and the degree of confinement of the explosive charge. The detonation products
were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission
electron microscopy were used to characterize the products. Lithium manganese oxides with
spherical morphology and more uniform secondary particles, with smaller primary particles of
diameters from 10 to 50 nm and a variety of morphologies were found. Lithium manganese oxides
with a fine spherical morphology different from that of the normal is formed after detonation wave
treatment due to the very high quenching rate. It might also provide a cheap large-scale synthesis
method. Explosive detonation is strongly nonequilibrium processes, generating a short duration of
high pressure and high temperature. Free metal atoms are first released with the decomposition of
explosives, and then theses metal and oxygen atoms are rearranged, coagulated and finally
crystallized into lithium manganese oxides during the expansion of detonation process. For
detonation of the water-solubility explosive, the detonation pressure, the detonation temperature and
the adiabatic gamma were close to 3 GPa, 2300 K and 3. The inherent short duration, high heating
rate (1010 – 1011 K/s) and high cooling rate (108 – 109 K/s) prevent the lithium manganese oxides
crystallites from growing into larger sizes and induce considerable lattice distortion.
Abstract: This paper describes a new method for prediction of the Chapman–Jouguet detonation
parameters of CaHbNcOdLieMnf explosives for mixture of some of low temperature explosion
explosives at 0 = 1000 kg/m3. Explosion temperatures of water-gel explosives and explosive
formulations are predicted using thermochemistry information. The methodology assumes that the
heat of detonation of an explosive compound of products composition
H2O–CO2–CO–Li2O–MnO2–Mn2O3 can be approximated as the difference between the heats of
formation of the detonation products and that of the explosive, divided by the formula weight of the
explosive. For the calculations in which the first set of decomposition products is assumed,
predicted temperatures of explosion of water-gel explosives with the product H2O in the gas phase
have a deviation of 153.29 K from results with the product H2O in the liquid state. Lithium and
manganese oxides have been prepared by the explosion of water-gel explosives of the metal nitrates,
M (NO3) x (M = Li, Mn) as oxidizers and glycol as fuels, at relative low temperature. We have also
used the Dulong-Petit’s values of the specific heat for liquid phase H2O. Lithium manganese oxide
powders with chrysanthemum-like morphology secondary particles, but with smaller primary
particles of diameters from 5 to 30 nm and a variety of morphologies were found. The oxides
produced by this cheap method affirmed the validity of explosion synthesis of nano-size materials
for lithium ion batteries.
Abstract: In order to simulate and study the hypervelocity impact of space debris on dual-wall structure
of spacecrafts, firstly a non-powder two-stage light gas gun was used to launch AL-sphere projectiles.
Damage modes in rear wall of dual-wall structure were obtained, and while the law of damage in rear
wall depends on projectile diameter and impact velocity were proposed. Finally, numerical
simulation method was used to study the law of damage in rear wall. By experiment and numerical
simulation of hypervelocity impact on the dual-wall structure by Al-spheres, and it is found that
AUTODYN-2D SPH is an effective method of predicting damage in rear wall from hypervelocity
impact. By numerical simulation of projectile diameter, projectile velocity and the space between
bumper and back wall effect on damage in rear wall by hypervelocity impact, and fitting curves with
simulation results, the law of damage in rear wall and dominant factors effect damage in rear wall by
hypervelocity impact were proposed.
Abstract: Many stiff clays forming part of natural slopes and earth dams exist in the fissured state.
When these cracks are subjected to gravity induced normal and shear stresses they may propagate.
The present discussion presents a numerical method to study the propagation direction of cracks
under stress fields similar to those found in the field. Not only did the results on one crack
propagation direction obtained from the numerical method and the analytical results agree well, but
numerical results have been used to investigate the mechanisms of the whole process of two
horizontal cracks initiation and propagation and coalescence in stiff soils.
Abstract: This paper describes a study on damage identification using wavelet packet analysis and
neural networks. The identification procedure could be divided into three steps. First, structure
responses are decomposed into wavelet packet components. Then, the component energies are used
to define damage feature and to train neural network models. Finally, in combination with the feature
of the damaged structure response, the trained models are employed to determine the occurrence, the
location and the qualification of the damage. The emphasis of this study is put on multi-damage case.
Relevant issues are studied in detail especially the selection of training samples for multi-damage
identification oriented neural network training. A frame model is utilized in the simulation cases to
study the sampling techniques and the multi-damage identification. Uniform design is determined to
be the most suitable sampling technique through simulation results. Identifications of multi-damage
cases of the frame including different levels of damage at various locations are investigated. The
results show that damages are successfully identified in all cases.