Finite deformation finite element analyses of plane strain stationary and quasi-statically growing crack fields in fully incompressible elastic-ideally plastic material are reported for small-scale yielding conditions. A principal goal is to determine the differences between solutions of a rigorous finite deformation formulation and those of the usual small-displacement-gradient formulation, and thereby assess the validity of the (nearly all) extant studies of ductile crack growth that are based on a small-displacement-gradient formulation. The stationary crack case with a significantly blunted tip is studied first; excellent agreement in stress characteristics at all angles about the crack tip and up to a radius of about three times the crack tip opening displacement is shown between Rice and Johnson's [1] approximate analytical solution and our numerical solution. Outside this radius, the numerical results agree very well with Drugan and Chen's I-2] small-displacement-gradient analytical characteristics solution in the region of principal plastic deformation. Thus we identify accurate analytical representations for the stress field throughout the plastic zone of a blunted stationary crack. For the growing crack case, the macroscopic difference in crack tip opening profiles between previous small-displacement-gradient solutions and the present results is shown to be negligible, as is the difference in the stress fields in plastic regions. The stress characteristics again agree very well with analytical results of [2]. The numerical results suggest -in agreement with a recent analytical finite deformation study by Reid and Drugan [3] that it is the finite geometry changes rather than the additional spin terms in the objective constitutive equation that cause any differences between the small-displacement-gradient and the finite deformation solutions, and that such differences are nearly indistinguishable for growing cracks.

The interfacial chemistry of InP/GaAs direct bonding with either 5% HF in water or HF:ethanol (1:9) chemical pretreatments was investigated. Multiple internal transmission-Fourier transform infrared spectroscopy (MIT-FTIR) and atomic force microscopy (AFM) were used to probe the bonding interface. The bond strength was measured as a function of annealing conditions and prebonding chemical treatment. The HF-based pretreatments remove the initial native oxide, leaving an interfacial layer of either water or ethanol. The initial room-temperature bond strength is primarily determined by the strength of hydrogen bonding, which, in turn, is a function of the prebonding treatment. The removal of interfacial water and ethanol, and with the subsequent formation of the oxide layer, leads to an increased bond strength. For ethanol-based HF treatments, ethanol appears to react with the underlying interfacial oxide layer through a complex interaction with the absorbed water. After annealing, the bond strength for all prebonding preparations can reach a high value, comparable to the fracture strength of the InP. The oxide composition after thermal annealing shifts from In 2 O 3 to the eventual thermodynamic equilibrium product, InPO 4 .

We have conducted numerical finite element studies of plane strain quasistatic crack growth in elastic-plastic material for a wide range of applied loading conditions and yielding extents, especially general yielding. To facilitate precise comparisons with previous analytical results, we have employed a fully incompressible, nonhardening material model. A reduced/selected integration procedure is successfully used to enforce material incompressibility. For crack growth under bending-dominant conditions, we employ an experimentally-measured applied load versus crack length history for a compact tension specimen that experiences crack growth from small-scale yielding through general yielding conditions. A constant crack tip opening angle crack growth criterion is employed to investigate crack growth under tension-dominant loadings in the same geometry. We have also conducted a small-scale yielding crack growth simulation employing a highly refined mesh, and several additional general yielding stationary crack solutions to further explore the effects of different far-field loading combinations. Detailed comparisons of the finite element results with Drugan and Chen's [1] 'm-family' of asymptotic analytical solutions are made in an effort to assess the latter's accuracy and range of applicability, and to identify their asymptotically indeterminate parameters m and R as functions of crack growth history. Among several interesting results, we find that Drugan and Chen's near-tip characterizing parameter has a nearly constant value of m ~ 1.23 for the entire crack growth process from small-scale yielding through general yielding conditions under bending-dominant loading when specimens have traction-free sides. However, we find m to vary significantly from that value as general yielding conditions are approached in tension-dominant loading situations, and whenever specimen sides are subjected to uniform applied loading. The numerical solutions confirm that Chen and Drugan's [2] global approximate analytical solutions for general yielding crack growth are remarkably accurate to substantial distances from the crack tip under a wide variety of loading conditions. The fully incompressible material model employed also facilitates great physical insight into the global stress and deformation fields accompanying general yielding crack growth: numerous figures display the slip lines (which are characteristics for both the stress and velocity fields) throughout the plastically deforming regions.],~0-+ m) A ~ 4.385 + 1 +~"