當一個可攜式電子裝置需要透過落摔試驗來檢測時，設計者為了避免產品在碰撞過程中造成破壞或失效，通常會事先採用有限元素分析來預測可能發生破壞的位置。本文的研究目的為透過材料試驗與模擬結果的比對，對可攜式電子產品提出一個較為準確的破壞預測方式。首先，我們選用PMMA與PC兩種熱塑性塑膠材料，進行在不同應變率下的拉伸試驗與彎曲試驗。並將得到的材料強度代入兩種分別基於Cowper-Symonds 模型與simplified Johnson-Cook 模型的本構方程式中，藉此得到材料在不同應變率下的動態抗拉及彎曲強度。接著我們用一種簡單的落錘試驗找出剛好會造成材料試片破壞時的落錘高度，並使用有限元素分析軟體HyperMesh與LS-DYNA以相同的邊界條件進行模擬以得到此臨界應力。藉由比較此臨界應力與抗拉強度可得知，若在破壞準則中不考慮應變率的變化，所得到的預測結果會相當保守，經過simplified Johnson-Cook模型修正後的動態抗拉強度可以對PMMA試片的破壞情形有更準確的預測。最後，我們透過應變規與高速攝影機來驗證有限元素分析軟體在模擬落摔試驗時的準確性，並藉由模擬結果對可攜式電子裝置提出一個有效的改良設計。

This study presents a procedure of failure prediction that can be used on the portable electronic device during the drop tests. The mechanical properties of PMMA and PC were tested by the tensile tests and flexural tests with various strain rates. Then two constitutive equations, the Cowper-Symonds model and the simplified Johnson-Cook model, were used to describe the tensile strength or flexural strength during the dynamic situation. The verification of the material models was made by comparing the experimental and simulated results of a free-falling dart test on PMMA. The results showed that the failure prediction without considering the strain-rate effect would be highly conservative. The simplified Johnson-Cook model on the tensile properties gives a much better failure criterion in the verification of the PMMA. The finite element software HyperMesh and LS-DYNA were used to analyze a barcode scanner, and the simulation results were verified by using the strain gauge and high-speed photography. Malfunction of a scan engine in the barcode scanner after the drop test was studied and a modification that may solve the problem was presented in the thesis. This method can be used in the industry so that the engineers can predict the failure of their design with better accuracy by using the simulation and material testing during the design stage.

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