# OS-E: 0310 Transfer Path Analysis

Demonstrate a Transfer Path Analysis (TPA) on a simplified vehicle model using OptiStruct. TPA is used to calculate and rank the noise or vibration contributions for a given Response Point, through the different structural transmission paths in a system.

## Model Files

Before you begin, copy the file(s) used in this example to
your working directory.

## Model Description

The model used is a simplified car model with an acoustic cavity. The model is already
setup for a modal frequency response run. The response point is the node which approximates
the location of the Driver Ear in the acoustic cavity. The source of excitation is a unit
load in the Global Z direction at the Engine Block. The Engine Block is connected to the
Body at 3 points using Engine Mounts modeled as
RBE2+CBUSH. To setup TPA, use the
PFPATH Bulk Data card and reference it using the
PFPATH I/O Option card.

**FE Model**- Element Types
- CHEXA

The linear material properties are:

- MAT1
- For Steel
- MAT10
- For Acoustic Cavity

## Results

The TPA utility in HyperView is used to post-process the results. Using the utility, the Calculated Response given by Equation 1 is plotted against the Solver Response for the Drive Ear Location. The Calculated Response should match up with Solver Response if all the paths have been considered and the co-ordinate system used for Attachment Forces output aligns with the co-ordinate system used for Transfer Function output.

$${P}_{t}={\Sigma}_{paths}\left[{P}_{i}\right]={\Sigma}_{paths}\left[{\left(\raisebox{1ex}{$P$}\!\left/ \!\raisebox{-1ex}{$F$}\right.\right)}_{i}\ast {F}_{i}\right]$$

Where,

- $P$
- Total pressure
- ${\left(\raisebox{1ex}{$P$}\!\left/ \!\raisebox{-1ex}{$F$}\right.\right)}_{i}$
- Transfer function, pressure at driver ear for a unit load for path $i$
- ${F}_{i}$
- Attachment force for path $i$

Now select the problem frequency, that is, peak in the response, which may be over the
target level and find the top contributors to the response at that particular frequency.