中文摘要：

焊头是超声塑料焊接设备中一个很重要的部件，其设计的好坏直接关系到焊接质量。将长条形焊头通过合理开槽划分为若干相等的单元．每个单元可作为复合阶梯形变幅杆来处理，用传递矩阵法得出了焊头单元的频率方程，为长条形开槽焊头的设计提供了理论依据。实验表明，利用该方程设计的长条形焊头，其实测频率与设计频率符合很好。本设计方法物理意义明显，计算简单，非常适合工程设计。此外利用该方法可方便的求出开槽数、槽宽度以及槽长度等因素对焊头尺寸的影响，也为焊头的优化设计提供了一定的理论依据。

英文摘要：

Ultrasonic horn is an important part in vibration system of ultrasonic plastic welding equipment, and its performances have directly effect on welding quality. In this paper, the strip-like horn is separated into several equal portions, and each portion can be viewed as a compound stepped type horn, and its frequency equation is derived by the transmission matrix method. Experiments show that the measured resonant frequencies of strip-like horns consist very well with the calculated results based on the frequency equation. The physical meaning of this design theory is clear and its calculation is simple, so it is fit for engineering design. Moreover, the relations between the slot number, the slot wide or length and the dimensions of horn can be easily derived from this design method, hence, a theoretical basis for the optimization design of strip-like horn is provided to a certain extent.