# Root Cause Analysis

From risk detection to problem solving, the diagnosis and root cause identification is a necessary step. SnRD Post-Processing proposes two modules:
1. Modal Contribution

The E-Line method is a time domain analysis approach, using Modal Transient Analysis, also known as the Modal Superposition Method. This enables a transition to the frequency domain.

(1)

Where:
• U(t) is the time domain displacement
• N is the number of modes extracted
• mi is the Modal displacement for a mode i
• ѱi is the Participation factor for mode i

With all the above responses available in the standard outputs from OptiStruct Analysis, the Relative Modal Contribution [%] values can be calculated. These will describe the participation of a mode or modes on a peak of the time domain response.

2. Modal Sensitivity

The modal sensitivity allows the analyst to live perform what-if studies by altering the time domain response of an E-Point or complete E-Line. This is achieved by decomposition of the Modal Superposition response, applying a factor (between 0 and 1) on selected modes, damping, canceling or isolating them.