Research – M. S. Allen


FOCUS: Dr. Allen is the principal investigator on over $1.2M of funded research.  Our research group is focused on experimentally probing and analytically predicting the dynamic motion of structures, especially:

  • Nonlinear dynamics of geometrically nonlinear structures, extensions to substructuring for these structures and test and model updating methods
  • Nonlinear normal modes and their utility in design and response prediction for nonlinear dynamic systems
  • Methods to experimentally characterize and predict damping and nonlinearity in structures due to friction at bolted/riveted/press-fit interfaces
  • Test strategies and data analysis procedures to characterize linear, nonlinear and time-varying dynamic systems
  • Experimental/analytical substructuring methods and applications to noise and response prediction during product development

Some current projects are described below.

CURRENT PROJECTS:
“Substructuring with Nonlinear Subcomponent Models Based on Nonlinear Normal Modes with Application to Hypersonic Vehicle Design,” PI, Young Investigator Program, Air Force Office Of Scientific Research, Program Manager: David Stargel, 2011-2014, $364,180
Read the news release at http://www.engr.wisc.edu/news/archive/2010/Nov23.html.

Schematic Hypersonic Panel
“Modeling and Identification of Damping due to Bolted Interfaces,” PI, Sandia National Laboratories, Program Manager: Matthew R.W. Brake, 2016-2018, $108k
The presentation below provides an overview to our work in this area.
Joint Modeling Thumbnail
“Experimental/Analytical Substructuring under Uncertainty,”co-PI, Sandia National Laboratories, 2007-2015*, $239,604* (*total of ongoing grants through 2012).
The natural frequencies of a system depend on the dynamic properties of all of its parts.  For example, this means that one cannot say whether the crankshaft of an engine will fail due to resonant vibration without knowing the dynamic properties of the transmission, axles, tires, etc…  This is a challenge since each of these parts may be built by a different supplier.  This work is developing new methods of predicting the dynamics of assemblies such as these.  One can avoid having to create a simulation model for a certain subcomponent (which may be difficult to model) by performing a dynamic test and coupling the test model to the model for the rest of the system.  Experimental models contain different types of uncertainties than analytical models, and these issues must be considered to obtain meaningful predictions.

Experimental Modal SubstructuringCMS Substructuring Thumbnail
SELECTED PAST PROJECTS:
“Method for Experimental Identification of Nonlinear Dynamic Systems of Unknown Form and Order with Application to Human Gait,” PI, National Science Foundation, Program Manager: Eduardo Misawa, 2010-2014, $279,982

Images from CSLDV work

Allen & Sracic recently showed that newly developed system identification methods can be used to increase the spatial resolution of laser vibrometer measurements by at least two orders of magnitude.  The new method produces high-resolution measurements of the deflection shape of the structure, in the time that traditional methods require for a single point.  Further advances have allowed this method to be used to find the vibration modes of a wind turbine blade as it vibrated due to ambient wind.  This information can be used to modify the design of a turbine to avoid failure, or to monitor the health of the turbine in the field.  Click on the picture below for more information.

Thumbnail for OMA-CSLDV Poster

For a video showing how continuous-scan laser vibrometry (CSLDV) works, follow this link to see a video of a CSLDV test on a downhill ski: (Low Resolution 18 MB), (High Resolution 68 MB)

Follow this link to see Dr. Allen’s Feb. 2010 presentation at the RRC Seminar, which summarizes some of his research.

Other Past Projects

Test-Analysys Model Correlation (TAM)
TAM Sensitivity Thumbnail
Atomic Force Microscope CalibrationAFM Calibration Thumbnail

The Atomic Force Microscope is a versatile new tool that allows one to image, manipulate and probe structures ranging in size from hundreds of microns (the size of common cells) down to individual atoms in a lattice.  The AFM has already contributed to revolutionary advancements in surface science, biology, chemistry, electronics and medicine.  The AFM must be calibrated to determine the force that one is exerting on a sample.  This project evaluates the effect of assumptions that are made when calibrating AFM probes, some of which may reduce the accuracy of, or even invalidate, the calibration.  Click here to see a presentation describing some of our work in this area.

Uncertainty Modeling in Micro Electro Mechanical Systems (MEMS) DevicesPDFs of RF Switch after OUU

Image above shows Histograms of the contact velocity of a high-speed switch after optimization, considering the uncertainty in the manufacturing process.  If uncertainty is not considered, one obtains worse performance than if no optimization had been performed at all.  (click on the image above to see a presentation summarizing this work)

Some of Dr. Allen’s Research Prior to Joining UW-Madison:

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