本論文利用在時間域上非直接的邊界元素法(BEM)解二維彈性動力問題。本方法經由Lame's Displacement potential求得Navier's Equation之特解，這些特解稱為基底(bases)。而邊界值問題的數值解則是基底之線性組合。利用semi-collocation method，隨時間的推進，將可推得線性組合的係數，而得其近似解。利用此方法解crack問題與Lamb's problem，並以C++程式語言來實作這些問題。在這些問題中，剪切力(shearing)的表現比張開力(opening)不穩定許多，並隨著取不同的常數p=△t/△x，也會影響到結果的穩定度，將取 p=0.4、0.5、0.8、1.0和1.2來討論，而crack problem 的結果亦會與解析解來作對比。

An indirect time-domain boundry element method(BEM) is used to solve two-dimensional elastodynamic problems in this thesis. The stress and displacement fundamental solutions are derived by means of solving Lame's displacement
potentials. The approximated solution is formulated as a linear combination of a set of bases.A semi-collocation method is used to derive the coefficient of the linear combination with time stepping and then deduces the approximated solution. The method is implemented to solve crack problem and Lamb's problem with C++ programming language. In these problems, the opening solution is stabler than the shearing solution. Taking different constants p=△t/△x also affects the stability of the problem and the problems take p=0.4、0.5、0.8、1.0 and 1.2 for comparison. The results of the crack problem compare with the exact solutions.

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