It is an important topic for electronic packages to estimate the interfacial bonding strength between dissimilar materials. If it is not strong enough, delamination would arise easily under high temperature, vibration or collision. Its reliability will be reduced. The study on interfacial fracture behavior between epoxy resin and die based on experimental and numerical analyses is investigated, and it is useful to judge where the delamination happens . In terms of interfacial fracture mechanics, the critical strain energy release rate (G ) of crack tip is related to the phase angle (£r ) . Considering the interface of the epoxy /die existing a tiny crack, the compact mixed mode (CMM) fixture is used to decide the critical load . Finally , we adopt the finite element method to calculate that the critical strain energy release rate (G ) and the phase angle (£r ) in comparison with empirical results .

The purpose of thesis is aimed to analyze fracture and fatigue behaviors of notched composite laminates by numerical method. Types of notch are both central notch 4mm£rand double-edged crack. We employed finite element method analysis with ANSYS to perform the numerical analysis. We adopted Tsai-Wu failure criterion to approach failure of central notch laminates by a step increment method and considered the effect of failure area gradually expanded, thus we obtained the ultimate stress of a laminate. In the work of fatigue testing and evaluation, we used Miner¡¦s rule to predict the extension of fatigue damage zone, and compared it with experimental results. In the analysis of a double-edged crack laminate, it is first assumed mix mode failure. Then, we calculated the stress intensity factors of various crack length by extrapolation, and developed a function of configuration correction factor. Finally, this study can be concluded as follows. The accuracy of ultimate stress prediction with step-by-step increment analysis is satisfactorily well. The outcome failure area of a laminate is closely corresponding with the observation of experiment. In predicting the fatigue damage zone, the predicted initial damage zone is close to experimental observation, but it is inconsistent with the actual damage extension due to crack propagation. Stress intensity factors and configuration correction factors are directly in proportion to the square root of crack length. It is corresponding with fracture mechanics. However there are some errors in quasi-isotropic laminates due to the existing of ¡Ó45¢Xplies.

Acid fracturing is one of the preferred methods to stimulate wells in carbonate reservoirs. It consists of injecting an acid solution at high enough pressure to break down the formation and to propagate a two-wing crack away from the wellbore. The acid reacts with the carbonate formation and this causes the etching of the fracture surfaces. After the treatment, the created etched surfaces do not close perfectly and that leaves behind a highly conductive path for the hydrocarbons to be produced. We distinguish the issue of treatment sizing (that is the determination of the volume of acid to be injected) and the issue of creating optimum fracture dimensions given the size of the treatment. This is reasonable because the final cost of a treatment is determined mainly by the volume of acid injected and our goal should be to achieve the best performance of the treated well. The well performance depends on the created fracture dimensions and fracture conductivity and might change with time due to various reasons. This research evaluates two field cases from Saudi Aramco where acid fracturing treatment has been used to stimulate a carbonate formation. I investigated the following issues: a) how effective was the treatment to restoring the initial productivity, b) how did the productivity of the well change with time; c) what are the possible reasons for the change in performance, d) what are our options to improve acid fracture design in the future? Based on our research work both near-well liquid drop-out and fractureconductivity deterioration can impact the production in different proportion. Moreover, the fracturing model tends to overestimate the fracture conductivity in some cases as shown in SA-2. Also, the “Acid fracture Number” concept proves to be an effective way to evaluate the acid fracturing treatment. Several recommendations were made based on this research work as described in the last part of my thesis.

The key to producing gas from tight gas reservoirs is to create a long, highly conductive flow path, via the placement of a hydraulic fracture, to stimulate flow from the reservoir to the wellbore. Viscous fluid is used to transport proppant into the fracture. However, these same viscous fluids need to break to a thin fluid after the treatment is over so that the fracture fluid can be cleaned up. In shallower, lower temperature (less than 250°F) reservoirs, the choice of a fracture fluid is very critical to the success of the treatment. Current hydraulic fracturing methods in unconventional tight gas reservoirs have been developed largely through ad-hoc application of low-cost water fracs, with little optimization of the process. It seems clear that some of the standard tests and models are missing some of the physics of the fracturing process in low-permeability environments. A series of the extensive laboratory "dynamic fracture conductivity" tests have been conducted. Dynamic fracture conductivity is created when proppant slurry is pumped into a hydraulic fracture in low permeability rock. Unlike conventional fracture conductivity tests in which proppant is loaded into the fracture artificially, we pump proppant/ fracturing fluid slurries into a fracture cell, dynamically placing the proppant just as it occurs in the field. Test results indicate that increasing gel concentration decreases retained fracture conductivity for a constant gas flow rate and decreasing gas flow rate decreases retained fracture conductivity. Without breaker, the damaging effect of viscous hydraulic fracturing fluids on the conductivity of proppant packs is significant at temperature of 150°F. Static conductivity testing results in higher retained fracture conductivity when compared to dynamic conductivity testing.

The purpose of this study is to determine if there is an alternative analysis method that can provide an estimate of fracture toughness for specimens that failed to meet all of ASTM E 1820 requirements. This study will look at three alternative analysis methods and evaluate each method’s ability to accurately and easily estimate the elastic-plastic fracture toughness. The standard method of analysis is long and complicated which leads to a number of validity requirements that many tests fail to meet. The objective is to find an easier and reasonably accurate estimate of elastic-plastic fracture toughness. This study has shown that there are two useful means of directly measuring the toughness from the load versus displacement record. It has also shown that there is a method of substituting a linear regression for the power law regression which yields good estimates of fracture toughness. All three methods have been estimating JQ which is a provisional measure of elastic-plastic fracture toughness. The first direct method uses an integral of the area up to the maximum load point to acquire the JQ. The second direct method uses a conversion of the linear elastic fracture toughness which only uses the crack growth and the maximum load from the load versus displacement record. The final method substitutes a linear regression of the two J-R points on either side of the JQ line to determine the JQ point. Each alternative analysis was able to acquire J values with varying degrees of accuracy. The linear substitution was the most accurate. The first direct method using an area integral tended to over predict the true J value. The second direct method using a conversion formula had a tendency to under predict the true J value. None of these methods could substitute for the ASTM standard; however, each provided a usable estimate of elastic-plastic fracture toughness.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 219-239).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 124-137).

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Young Kwon. Includes bibliographical references (p. 23-24). Also available online.

Thesis (Ph. D.)--University of Hong Kong, 1984.

Thesis--M. Phil., University of Hong Kong, 1983.