could you pls tell a little more on techniques to absorb vibrations?
It is not an easy question to answer as each engine is different and solutions are different. Some examples might be the type and design of seals used in the bearing box area (seals can be good dampeners), perhaps the number of struts used or even their orientation relative to engine centerline could be another solution. But the finite element analysis program gives good indications as to which technique or techniques might be most advantageous to use if a problem is apparent. One other thing, you can raise the vibrational frequency of a frame without reducing weight by use of a stiffener ring on the OD of the frame so the frame is not resonant with most vibrational modes in the operating range of the engine. A separate item that affects vibrations is the distance separating the engine mounts that attach to the pylon. The further they are apart, the vibrations become larger should an unbalance condition exist in the rotor system of the engine. All these things must be considered in the frame structure design and analysis.