MDS File Format |
 
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MDS File Format |
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The MDS file contains the modal response of the structure, including the natural frequency, mode shape, mode slope and mode curvature, for each natural bending mode. The data is presented at the ends of the segments which are used by Shear7 to discretise the structure. Typically the segments used in the Shear7 simulation are of uniform length, so these locations will rarely correspond to the nodes of the Flexcom finite element model.
The MDS file is sub-divided into 3 distinct three blocks.
•Block 1 – this block consists of just one line with 2 numbers, the number of modes (Nm) presented in the MDS file, and the number of Shear7 nodes (Nn) used to describe the mode shape. The number of Shear7 nodes is always one greater than the number of Shear7 segments (Ns).
•Block 2 – this block consists of Nm lines, where Nm is the number of modes defined in Block 1. Each line has 2 numbers, the first is the mode number and the second is the corresponding natural frequency, omega (in radians/second).
•Block 3 – the rest of the file presents the mode shape, slope and curvature as a function of Shear7 node number, repeated for each modal frequency. So the block consists of Nn (number of Shear7 nodes) times Nm (number of modes) lines. Block 3 normally has 5 columns. Optionally a 6th column may be included, if the Shear7 segments are not of uniform length.
•Column 1 – Mode number
•Column 2 – Shear7 node number
•Column 3 – Mode shape. This is the normalised displacement computed by Modes, with the maximum amplitude of Column 3 being 1.0 for a given modal frequency
•Column 4 – Mode slope, corresponding to normalised mode shape
•Column 5 – Mode curvature, corresponding to normalised mode shape
•Column 6 (optional) – Shear7 node positions, defined as a fraction of length along the structure (i.e. ranging from 0.0 to 1.0). This data is only necessary if the Shear7 segments are not of uniform length, and in this case presented for the first modal frequency only (as it is frequency independent)
A sample MDS file is shown below. Block 3 is truncated for illustrative purposes. Note that the MDS file contains no blank lines.
