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This thesis is devoted to solution of the two-dimensional elastodynamic problem for a cracked bimaterial loaded by harmonic waves. The system of boundary integral equations for displacements and tractions at the interface is obtained from Somigliana identity with the allowance for the contact interaction of the opposite crack faces. Full expressions of the integral kernels derived by the consecutive differentiation of the Green's displacement tensor are given. Due to the contact that takes place between the faces of the crack under the applied external loading, the resulting process is a steady-state periodic, but not a harmonic one. Thus, components of the stress-strain state are expanded into exponential Fourier series. The collocation method with a piecewise constant approximation on each linear continuous boundary element is used for the numerical solution. The problem is solved using the iterative algorithm. The solution is refined during the iteration process until the distribution of physical values satisfies the imposed constraints. The results are obtained for the interface crack subject to normal tension-compression, normal shear, or oblique tension-compression waves with different values of the angle of the wave incidence and the wide range of the dimensionless wave number. The distributions of the normal and tangential components of the contact forces and displacement discontinuities on the surface of the crack are investigated. The stress intensity factors are computed and analyzed for various values of the wave frequency, the friction coefficient, and material properties. The maximal stress intensity factors at the trailing crack tip differ from the SIF values at the leading crack tip showing non-symmetry of solution with respect the space and time variables. It is concluded that the crack closure and friction effect change the solution both qualitatively and quantitatively, as the difference between comparable results can achieve 30-50%.

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Thesis (M.S.)--Ohio State University. / Includes bibliographical references (leaves 111-115). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 87-90). Also available on the World Wide Web.

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Specimens of quarter-hard electrolytic copper, twenty feet in length and one-quarter inch in diameter, were statically pre-stressed and subjected to impact loading. Dynamic strain vs time traces, for both loading and unloading waves, were obtained using resistance-type strain gages mounted at various positions along the specimens. Permanent strain increments resulting from each impact were determined. Prestress levels ranged from values well below the yield point of the material to values exceeding the yield point. Impact velocities and impact durations were also varied. The experimental strain wave shape and propagation velocity in bars prestressed well below the yield point were found to compare favorably with the theoretical elastic wave shape and velocity. The unloading waves propagated in bars prestressed above the yield point were found to be similar in shape to the elastic waves observed and to propagate at the elastic velocity without diminution of amplitude. For loading waves propagated in material prestressed above the yield point the incipient portion of plastic strain waves was found to propagate at the elastic velocity. The lower strain increments of the plastic strain waves were found to propagate at higher velocities and the highest strain increments were found to propagate at lower velocities than would be predicted from a strain-rate-independent theory. For the loading waves, a method was developed to approximate the dynamic loading curves (stress-strain relation followed during impact loading). Prom the dynamic loading curves, the peak stress levels of the plastic strain pulses were found to be significantly higher than the stresses at equivalent strains on the static stress-strain curve. The results tended, at least qualitatively, to support a strain-rate-dependent wave propagation theory rather than a strain-rate-independent one. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by John Hainsworth. / B.S.

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xiv, 204 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 190-195).