Hello
i was trying to design an ultrasonic horn sonotrode : 
 the calculation are made for halfwave lengh , and  the longitudial mode for natural frequency is at 20khz,the modal analysys was made for a free free condition ( no fixture)
i have now to make the harmonic analysis and add a harmonic displacement to  the sonotrode imposed by the transducer.
how to imput this displacement and where , if i add fixture to yhe part , all natural frequencies changes .
thanks for your Help