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Diagnostic Testing

Diagnostic Testing

Response Dynamics has made diagnostic testing our core focus for over 30 years. We do this detective work well because we have particular expertise in structural dynamics and how it relates to vibration and acoustic noise issues on a myriad of levels.  We enjoy this work because it stays interesting and draws on multiple disciplines in engineering and science.

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Dynamic Analysis Laser Test Bench Response to Cooling System Disturbance


Failure Analysis of Refractory Cone Related to Structural Vibration


Cast Aluminum Fan Blade Failure Analysis Involved FEA and Strain Gage Testing of Instrumented Fan Blade

We most often characterize a problem first and work from known conditions, and stay in “the known” as we proceed by making sense of what we observe as we move forward. We test and analyze the change in dynamics we are trying to create in real-time, on site, and often make changes to our experimental test plan on the fly as we discover how a system is actually behaving. In doing so we often get meaningful results from which we can make sound engineering decisions in a short time frame. We don't just make measurements and spit out data. We help identify the problem and propose solutions.


Modal Analysis Used to Understand Engine Mount Failure


Semiconductor Measurement Disturbance Related to Stage Move


Surgical Robot Dynamic Analysis for Improved Motion Control

We know instrumentation, digital signal processing, and spectral analysis, and use our specialized skill set, and vast array of instrumentation that we have collected for over 3 decades, to design tests and solve tricky problems. Examples include: nanometer disturbances in interferometers, thermal and acoustic issues in military control hardware, magnetic/acoustic/vibration issues in scanning electron microscopes, turbine isolation issues in hundred megawatt power plants, optics vibration and servo control issues in sub-micron genomics microscopes and diagnostic testing of mountain top telescopes, to name a few.


Key concepts common in diagnostic testing:

  • Multi-variable testing is usually necessary to really get a handle on an issue involving multiple disciplines of physics.

  • Measurement of multiple variables requires an understanding of the physics of the coupling between them as well as the physics and limitations of the instrumentation.

  • Additionally, problems in different frequency ranges necessitate unique approaches involving instrument selection, mounting dynamics, cabling, and coupling with other structures and media.

Long Term Continuous Tracking of Multiple System Variables

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Vibration Testing of a Steam Turbine in Cogeneration System

We use our testing expertise, as well as various methods of analytic, computer simulation, Finite Element Analysis (FEA) , and numerical analysis (often for non-linear systems), to make sense of the system problems so that we will have confidence that our understanding is indeed correct (or sufficiently correct). We always strive to prove a hypothesis using more than one testing and analysis method. We also make an effort to know what we don't know by considering measurement error, instrumentation noise, resolution limitations, and non-linear behaviors.


We very often get our hands dirty and build proof-of-concept “fixes” on site, or back in our shop, to quickly test a “design-fix” concept. We do this prototype testing carefully, with 30 years of structural dynamics experience, always working hard to test and keep an accurate understanding of the current system dynamics and the boundary conditions as we make changes. However, as so often happens to our clients, when quick and dirty fixes are attempted by other engineers with little structural dynamics experience, confusion, delay, and uncertainty regarding the design of the experiment often result. A faulty test often leads to the wrong conclusion and drives the wrong action. Valuable development time is often wasted, and the issue soon becomes an emergency. We avoid these pit falls and can help get the team back on track.  See our discussion on Product Emergency.


Thermal Drift of Base Structure Superimposed on a Stick/Slip Misalignment Due to Stage Moves

We have the experience to quickly analyze past test methodologies and explain for the team what has been done well, and what needs improving, tweaking, or additional attention to a particular dynamic parameter. This is important for getting an engineering team all on the same page by making sure everyone understands the problem, what has been done, and how to move forward. These unique abilities have brought us long lasting working relationships with the majority of our clients. 


Acoustic Resonance Coupled To Mechanical Vibration And Image Disturbance On Semiconductor Inspection Tool


Automotive Mount Failure Testing


30 Years of On-Site Testing and Trouble Shooting of Semiconductor Process and Inspection Tools

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