SDOF Analysis

SDOF analysis begins with the creation of two input windows; SDOF input blade waterfall and SDOF input single blade. The SDOF Input Blade Waterfall shows all the probes and differences overlaid together. The red and blue points represent the maximum positive and maximum negative points on each trace. The analysis range for each blade is selected from this plot. The blades may all share the same range or have individual ranges to accommodate blade mistuning. Only one range is allowed per blade, which is shared by all probes/differences.

SDOF Input Single Blade Plot

The SDOF Input Single Blade plot is used to adjust the analysis range of a single blade. The colored regions on the deflection traces indicate the analysis range. The dots overlaid on the deflection traces are the maximum and minimum points that are used to calculate the initial values for the curve fit parameters. Once the ranges have been selected and the deflection extremes are available for the initial value estimations, the curve fit can be launched. Either a single blade analysis or all blade analysis can be performed.

SDOF Output Single Blade Plot

The plot displays the selected probe or difference and an overlay of the SDOF model for the selected blade or the SDOF Model displayed in envelop mode. Differences between the SDOF model may indicate blade to blade coupling due to mistuning or a multiple mode response.

SDOF Output Blade Waterfall

The SDOF Output Blade Waterfall plot is a display of the SDOF analysis results. It can be display in an envelope mode or as a trace. The envelope mode can have several different color schemes used to convey other information such as absolute phase, delta phase, etc. The trace display can be used to show an overlay between the raw data and the calculated model. The display can also be switched between the probe/difference output and the calculated results. The calculated results are scaled deflections or stress that uses the engine order derived from the frequency calculation to appropriately scale the results.

SDOF Amplitude Bar Chart

The SDOF Amplitude bar chart displays the peak amplitudes values for each blade. The values are either the individual probe or difference results or the calculated result from the entire probe set. The Maximum, Minimum, Average, Maximum/Average Ratio and the amplitude of the selected blade are displayed below the bar chart.

SDOF RPM Bar Chart

The SDOF RPM bar chart displays the resonant rpm value for each blade. The values are either the individual probe or difference results or the calculated result from the entire probe set. The Maximum, Minimum, Average and the amplitude of the selected blade are displayed below the bar chart.

SDOF Damping Bar Chart

The SDOF Damping bar chart (Fig. A) displays the damping value for each blade. The values are either the individual probe or difference results or the calculated result from the entire probe set. The Maximum, Minimum, Average and the amplitude of the selected blade are displayed below the bar chart.

The diagram picture (Fig. B) represents the simple spring/mass/damper system that is described by SDOF.

Figure A

Figure B

Nodal Diameter Waterfall Plot

The amplitude and phase information from the individual blade models are recombined into a system response analysis that displays the nodal diameter amplitudes across the resonant response. The data is displayed in a 3D waterfall format that has the nodal diameter as the x axis, amplitude in the z axis and the revolution number or rpm in the y axis. The nodal diameter content associated with a resonant response provide valuable insight into the disk interactions and forcing function characteristics.

Nodal Diameter Tracking Plot

The Nodal Diameter Tracking plot provides a 2D graphical display of the nodal content for selected nodal diameter components. This is useful for comparing nodal diameter amplitudes as well as studying nodal diameter interactions.

Campbell Diagram Update

The Campbell diagram is used to show the deflection of a selected blade in an envelope mode. The color can be absolute phase, delta blade phase or red/yellow stress limits.