目前混凝土非破壞檢測技術大多採用應力波或是超音波當做試驗媒介，透過瑕疵介面之間所造成波的折反射訊號反推求瑕疵位置，但是對於混凝土早期裂紋，甚至因反覆載重疲勞所造成之材料劣化，目前尚無法檢測。主動式振動調變檢測技術 (active vibro-acoustic modulation technique)已廣泛被應用於細微裂紋之偵測，透過導入低頻與高頻兩種不同頻率，使細微裂紋產生開闔效果，造成額外的調變波，進達成檢測目的。然而，對於理論模型的完整建立及驗證仍缺乏。
為了更瞭解裂縫非線性所造成的調變行為，本文除建立完整物理模型及理論推導外，並配合實際應用於鋼及混凝土樑試體細微裂縫之偵測，結果顯示 AVMT確實具有偵測早期細微裂縫的能力且實際應用時亦具良好可行性。

Widely used nondestructive techniques for concrete material are based on the stress wave propagation theory. By analyzing the stress wave reflected or refracted by the interface formed by defects and the concrete in time or frequency domain, the location of defects may be determined. But it is not an easy task to evaluate the
concrete micro-crack at early stage or deterioration caused by repeated/fatigue loading.
The active vibro-acoustic modulation technique (AVMT) is widely applied to nondestructive evaluation of micro-cracks. By introducing the two different frequencies (LF and HF), the micro-cracks would be opened and closed and also the extra harmonics and modulation would be induced. However, it lacks of the physical modeling and theoretical verification to date. To better understand the behavior of the modulation caused by defect nonlinearity, the nonlinearity of physical model and
theoretical verification would be considered and practically apply to both the steel and concrete beam samples. It reveals the feasibility of the AVMT in detecting the tiny cracks and defects in the concrete beams.