DRD Supplementary Materials to ANSYS Dynamics Course

 

Supplementary Material to Harmonic Analysis Chapter and Workshop

DRD has expanded the harmonic analysis of a fixed-fixed beam workshop to cover a variety of important concepts. The beam is shown in the figure below with two harmonic forces.

 
In DRD's expanded version of this workshop we cover several important concepts.  

• We cover the general procedure for performing harmonic analysis using the full method.  

• We apply the two complex beam loads in phase, 90 degrees out of phase, and 180 degrees out of phase and investigate how any why the load phase angles excite certain modes and don't excite others. In other words, we learn how to define and interpret the effect of complex (real and imaginary) loads on harmonic response models.  

•  We apply modal, alpha, and beta damping to the model, and we calculate manually the alpha and beta coefficients to achieve the desired levels of damping.  

• We cover the procedure for finding the model physical location, forcing frequency, and phase angle, which produce the maximum model displacement.

The graphic below shows the harmonic response of the beam with the forces acting in phase near the first natural frequency of  the beam.

These graphs show frequency response plots at a variety of load phase angles and damping models.

 

 

 

 

 

Supplementary Material to the Response Spectrum Material in the ANSYS Spectrum Analysis Module

 
We show how to idealize the table workshop from the ANSYS standard course materials as a single degree of freedom system, and then we show how to perform a hand calculation to check the ANSYS response spectrum model maximum displacement. The graphic below illustrates how the table is idealized as a single degree of freedom system.

 

Supplementary Material to the Random Vibration PSD Spectrum Material in the ANSYS Spectrum Analysis Module
As with response spectrum, we show how to idealize the table workshop from the ANSYS standard course materials as a single degree of freedom system, and then we show how to perform a hand calculation to check the ANSYS PSD spectrum model 1s displacement. 1s refers to the standard deviation of displacement.  

DRD has created a workshop in which the students subject the electronic chassis shown in the figure below to the PSD spectrum shown on the right.

In the random vibration workshop we also show how to calculate the response PSD at the model base in order to reproduce the input PSD. This is a standard model results check, which DRD recommends. The graph on the lower left is the input PSD displayed in the ANSYS preprocessor. The graph on the lower right is the input PSD displayed in the ANSYS time-history postprocessor, and it was created by calculating output PSD at the chassis base.

We also cover how to calculate output PSD  at arbitrary locations on the model and then superimpose the output PSD in the input PSD curve as shown in this graphic on the right.
We wrap up the spectrum portion of the course by introducing batch input files for performing response spectrum and random vibration analysis. These batch input files facilitate performing efficient spectrum solutions, documenting spectrum solutions, and effective management of large spectrum solution files.

 

 

Supplementary Material to Mode Superposition Harmonic Response Portion of Dynamics Course

In this workshop we apply a base acceleration over a range of frequencies to the electronic chassis on the right.

We use the mode superposition technique in combination with a large mass at the base to apply the base acceleration.  The chassis is shown on the right.

 

The graph on the right shows the chassis frequency response due to harmonic base acceleration.
This workshop also provides practice on finding the model location, forcing frequency and phase angle at which the maximum model stress occurs. Finally we expand the mode superposition solution to allow postprocessing of the model maximum stresses.  

We conclude this workshop with a hand calculation to check the ANSYS model results.

 

 

Supplementary Material to Mode Superposition Transient Dynamic Portion of the Dynamics Course

In this workshop we apply a shock due to an isosceles triangle acceleration versus time loading to the electronic chassis.  

We use the mode superposition technique to perform an efficient solution.

The chassis is shown on the right.

 

The isosceles triangle acceleration versus time loading is shown on the left.
We use the time-history postprocessor to review the results. The base motion versus time is shown on the right.

 

 
 

We also expand the time-history solution at a subset of the total available time history solution sets to enable time history animation of the model results as shown in this graphic below.

 
 

We check the transient dynamic solution using the dynamic load factor approach. The dynamic load factor curve for an isosceles triangle load curve is shown on the right.  

Finally, we show how to adjust the dynamic load factor to account for a half sine loading instead of an isosceles triangle load versus time curve.