The role of bonding in the tensile creep behavior of paper was analyzed. This was accomplished by producing handsheets at a range of different bonding levels through manipulation of relative bonded area and specific bond strength. This was done by varying the level of wet pressing (to change relative bonded area) and using debonding and bonding agents (to change specific bond strength). Once manufactured, sheets underwent an extensive battery of physical testing and creep testing. Creep testing was conducted under constant humidity and cyclic humidity (accelerated creep) conditions. Microscopic analysis techniques were also employed to visually study bonded area loss from creep strain. Two mathematical models (one empirical and one rheological) were created to isolate, account for, and incorporate bonding into predicting tensile creep behavior in paper. Overall, the results from this thesis show that the role of bonding in tensile creep behavior (and accelerated creep behavior) is no different than its role in stress-strain behavior, which is a new finding. This means the bonding influence on tensile creep behavior is related to sheet efficiency and how effectively stress is distributed within the structure, bonded area loss is a strain-induced phenomenon and bonding is not the cause of accelerated creep behavior.

There are four types of oyster aquaculture such as oyster plug rod, horizontal hanging scaffold, pontoon-style longline, and floating raft system. This study is to investigate the mooring tension of an oyster floating raft system under environmental loadings. According to the hydrodynamic experimental test, the horizontal fluid velocity has a retarded phenomenon when encountering the front part of structure, and then gradually reduces to a stable situation after the second floating rod. The phenomenon is identified as shielding effect for the raft system and has been used as a shielding coefficient to modify the fluid velocity in the computation program. The dynamic analysis of floating raft system under random wave interaction is investigated numerically and experimentally. The lumped mass method is applied to divide the structure into many nodes and elements. A modified Morison equation dealing with moving structure components is used to calculate the environmental forces on the elements. Further, the forces on elements are divided equally into neighboring nodes to form the equation of motion based on Newton¡¦s second law. Finally, the 4th-order Runge-Kutta (RK4) method is used as a time marching scheme to predict the displacement and velocity of nodes for the next time step. The results of time series and spectrum analysis of mooring tension show good agreement between numerical predictions and experimental data. This paper has further expanded to predict the field oyster raft system in an open sea, and offers some useful information to the oyster farmers in terms of improving the structure safety.

In view of the foreign mariculture is gradually diversified, and even has a trend that the fish cage aquaculture combines with algae culture at the same facility. A submersible single-point-mooring (SPM) cage system was modified and installed in-situ to investigate the feasibility of the cage system. A numercial model was established to simulate the cage dynamic motion as well as the mooring line tension. A detailed cage construction process was described in this study. Tension meter was used to keep track of mooring line tension, while the ADCP( Acoustic Doppler Current Profiler) was utilized to record the sea state during the test period. Those data were used to validate the numerical model. The field experiements were carried out at a location north to Xiaoliuqiu island. Since the testing period was in winter, the wave height was relativly calm and found to be between 0.5 and 1.2 m, wave period 4~7 seconds, and wave current about 0.2~0.6 m/s. The numerical results indicate that the maximum mooring line tension has good agreement with the meauresments of the tension meter. These comparisons verify that this numerical model is sufficient to simulate this kind of alage cage systems.

The aim of this thesis is to investigate Ti/APC-2 nanocomposite laminates mechanical properties after low velocity impact. The finite element analysis with software ANSYS/LS-DYNA is used to analyze the size of damage and plastic zone and internal energy of laminates during low velocity impact. Finally, the numerical results and experimental data are in good agreement. The work can be divided into two parts: the first is to fabricate the hybrid composite laminates and place the samples on the floor, subjected to the free drop of a rigid steel ball of 1m and 2m high. Then, the samples after impact were due to static tensile and fatigue tests to obtain mechanical properties. Using the optical microscopy the impact defects of laminate surface were measured. The second, ANSYS/LS-DYNA was used to simulate a laminate impacted by a steel ball. The energy change of steel ball impact and internal energy of laminates during impact were also discussed. From the experimental data, the mechanical properties, such as ultimate strength and stiffness, of virgin samples are better than those of impacted samples due to free drop. In addition, no matter the laminates were added nanoparticles SiO2 or not, the strength of laminates reduces after impact, however, the fatigue resistance of impacted samples does not lose much. Compare with the data of penetration depth and plastic zone due to free drop. The errors of numerical results are 5.4%~12.4% for the penetration depth and the errors 5.21%~8.98% for plastic zone respectively. That is acceptable. The numerical method ology provides a reference to realize the energy change in laminates after impact. Also, from the experimental measurement it is obvious to see damage area after impact and the mechanical properties do not reduce significantly due to low velocity impact generally in Ti/APC-2 composite laminates.

Direct methanol fuel cell (DMFC) were characterized with low operation temperature, high energy density, rapid activation, easy to obtain, easy to carry, safety, stability and low pollution. Therefore, DMFCs were thought as the next generation of power suppliers to replace lithium battery in the future. In order to meet the miniaturization demand of portable electronic devices, this research tried to fabricate a £gDMFC, simplify component, and lower cost by using MEMS technique. This research used TMAH etching, PEACE, and KOH etching, CNT growth technique to fabricate the hill-like diffusion layer (HDL) electrode which combined the channel structure and through-hole silicon (THS) electrode. Another emphasis of this research was to improve the bubble cover problem for £gDMFCs. The bubble cover problem resulted from the CO2 bubble generated in methanol oxidation reaction difficultly removed and resulted in adverse effect for reaction. This research tried to use the surfactants which used in electroforming to improve the bubble cover problem by improvement surface tension of fuel. Experiments show that using the HDL electrode in anode and the THS electrode in cathode would get the maximum power density (0.186 mW/cm2). The powder density of the design £gDMFC is 10 and 2.5 times larger than the one with pure carbon paper electrodes and the HDL electrodes. Surfactant MA was suitable as a wetting of methanol. Bubble size could reduce 1/2 to 1/3 and bubble cover area could reduce 20% by adding MA. Add MA in the fuel cell could help the bubbles remove to avoid the bubble cover problem. Though MA addition would have the adverse effect for methanol reaction, could get the stabile voltage and extend the discharge time.

Abstract This research is to develop a new compound cage system that not only has the benefit of the traditional cage system but also has a series of oyster containers hanged on the circumference of the floating collar to add economic value to the cage aquaculture industry. The purpose of this study is to investigate the cage net deformation rate and the maximum mooring tension at the anchor under three types of Liuchiu sea states. The results of numerical simulation could be used as valuable guide for fish farmers and aquacultural cage designers. The developed numerical method is based on a lumped-mass approach to build a system of motion equations, and then utilizes the fourth order Runge-Kutta method to solve the motion equations. The numerical results reveal that under regular wave conditions, the cage net deformation rate for the compound cage system is slightly less than that of the traditional cage system, but the maximum mooring tension has reversed effect, i.e., the compound cage system has higher mooring tension than that of traditional one. As for the cases of irregular waves, the numerical results indicate that the cage net deformed so seriously that the fish can¡¦t survived at the sea condition of typhoon 50-year return period. To overcome this net shrinkage problem, an improved scheme is necessary to be implemented before a real compound cage system is installed in the open sea.

When an aluminum alloy plate after rolling, non-uniform residual stress distributions existed inside the plate and defects, such as edge wave, middle wave, of the plate will be induced. Usually, a levelling process will be adopted to modify the plate flatness. By numerically simulating the tension levelling process, the purpose of this thesis is to understand the final dimensions and the residual stress distribution of the aluminum plate subjected to the tension levelling process. This study used the finite element method as the basic theory of the numerical simulation. A 3-D model of a cold-rolled plate with a side wave, subjected to tension levelling process was constructed. Then, the effects of the variations of the tensile ratio and residual stress distribution after rolled on the residual stress distribution after levelling and the improvement of flatness were studied. The simulation results showed that in the wave region, the tension levelling process could eliminate more than 90% of the residual stress, in the flat region was up to 80%.Also, after leveling, the residual stress distribution in the flat region was more uniform than the wave region. After-rolled residual stresses at the wave region affected the final peak position of the wave and the stress eliminated ratio of the wave region, but showed no significant effect on the final plate width and the residual strains. After-rolled residual stresses at the flat region affected the stress elimination ratio of the flat region only. The tensile ratio would affect the plate flatness, the plate width, stress elimination ratio, and the maximum residual stress. The higher of the tensile ratio, the more flatness of the plate would be obtained, but the higher residual strain would be induced and caused the lesser range of available plate.

Compression tests along the rolling and normal direction of AZ31B plate materials under 10 s strain rate were performed at room temperature to understand the effect of grain size on the formation of deformation twins. When compressed along the rolling direction, tension twins were formed in bands. Within the twin bands, nearly all grains contained tension twins, irrespective of grain size. And outside the bands, no twin was found. Under this deformation condition, grain size has no effect on the formation of tension twins. The reason for this is due to the fact that the formation of a tension twin can trigger the formation of tension twin in the neighboring grain, irrespective of the neighboring grain size. When compressed along the normal direction, no twin band was formed, and compression twins were formed evenly in the specimens. Under this deformation condition, it was found that the larger the grain size, the higher the fraction of grains which contained compression twins. This result indicates that compression twins are easier to be formed in the large grains.

Excess lubricant can be found as reservoirs on the sides of the rolling tracks when the oil flows through the Hertzian contact and the side leakage. Uniform lubricant layers adhered to both rolling surfaces can flow into the supply region by the action of surface tension. Uniform lubricant layers are separated by air so that they move with the surfaces the surface tension of the liquid-air interface and the velocity of the roller. Hence, it can be considered as the fixed flow rate conditions. Under the lubricant starvation and the fixed flow rate conditions, the meniscus in the film inlet is formed due to the action of the surface tension of the oil-air interface, where the fluid pressure in the oil layer is smaller than the ambient pressure. An empirical formula to predict the thickness of the oil layer is derived based on the theoretical analysis and the experimental results of Cann et al. [10]. Results show that this thickness increases the amount of oil in the track and the surface tension of the liquid-air interface, but it decreases with the surface velocity and the oil viscosity. Moreover, the starved, fully flooded, over-flooded regimes are established based on the theoretical analysis. Under the lubricant starvation and the fixed flow rate conditions, the central film thickness in the pressure region increases with increasing the supply flow rate, so that the location of the meniscus moves to upstream. When the supply flow rate is more than 98% flow rate of fully flooded condition, the central film thickness achieves a saturated value. Hence, when the supply flow rate is between 98% and 100% flow rate of fully flooded condition, it is called the fully flooded regime. When the supply flow rate is more than the flow rate of fully flooded condition, the central film thickness remains constant, and the excess oil accumulates in the inlet region, so that the film thickness in the inlet region increases with time. When the supply flow rate is larger than the flow rate of fully flooded condition, it is called the over-flooded region.

The dissertation focuses on the analysis, through combined analytical and numerical techniques, of the partial differential equations arising from a new approach to modeling brittle fracture, based on extension of continuum mechanics to the nanoscale. The main part of this work deals with the analysis of several fracture models. Integral transform methods are used to reduce the problem to a Cauchy singular, linear integro-differential equation. It is shown that ascribing constant surface tension to the fracture surfaces and using the appropriate crack surface boundary condition, given by the jump momentum balance, leads to a sharp crack opening profile at the crack tip, in contrast to the classical theory of brittle fracture. However, such a model still predicts singular crack tip stress. For this reason a modified model is studied, where the surface excess property is responsive to the curvature of the fracture surfaces. It is shown that curvature-dependent surface tension, together with boundary conditions in the form of the jump momentum balance, leads to bounded stresses and a cusp-like opening profile at the crack tip. Further, an alternative approach, based on asymptotic analysis, which is suitable to apply in cases when the model includes a mutual body force correction term, is considered. The nonlinear nonlocal problem, resulting from the proposed model, is simplified which allows us to approximate the crack opening profile and derive asymptotic forms for the cleavage stress in a neighborhood of the crack tip. Finally, two possible fracture criteria, in the context of the new theory, are discussed. The first one is an energy based fracture criterion. Classically the energy release rate arises due to singular fields, whereas in the case of the modeling approach adopted here, a notion analogous to the energy release rate arises through a different mechanism, associated to the rate of working of the surface excess properties at the crack tip. Due to the fact that the proposed modeling approach allows us to fully resolve the stress in a neighborhood of the crack tip, without the customary singularity, a second fracture criterion, based on crack tip stress, is possible.