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Article Topic |
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File Size |
Date it appeared in E/T |
| Sometimes the mode shapes appear to be rotated from what is expected. Are the modes wrong? |
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158 KB |
Jan/Feb 2008, Vol. 32, No. 1 |
| Bolted joints are common in structures. Can the frequency change significantly due to joints? |
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100 KB |
Nov/Dec 2007, Vol, 31, No. 6 |
| The stability diagram has poles that are not indicated by the MMIF or CMIF; are they really modes? |
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206 KB |
Sep/Oct 2007, Vol. 31, No. 5 |
| How do you interpret the stability diagram? And how do data points affect the fit? |
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171 KB |
Jul/Aug 2007, Vol. 31, No. 4 |
| How do you select the reference location for a modal test? What needs to be considered? |
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621 KB |
May/Jun 2007, Vol. 31, No. 3 |
| What is the difference between all the mode indicator functions? What do they all do? |
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248 KB |
Mar/Apr 2007, Vol. 31, No. 2 |
| What is MRIT??? I hear people talk about it for impact testing. |
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240 KB |
Jan/Feb 2007, Vol. 31, No. 1 |
| Someone told me that operating modal analysis produces better results, and that damping is much more realistic |
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180 KB |
Nov/Dec 2006, Vol. 30, No. 6 |
| What is a good MAC value so that I know my model is right? |
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256 KB |
Sep/Oct 2006, Vol. 30, No. 5 |
| Is there any problem running a modal test to 2 KHz but only analyzing up to 500 Hz? |
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212 KB |
Jul/Aug 2006, Vol. 30, No. 4 |
| What effect can the test set up and the rigid body modes have on the higher flexible modes of interest? |
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187 KB |
May/Jun 2006, Vol. 30, No. 3 |
| Can modal parameters be extracted for heavily damped modes when you can’t see them in the measured FRFs? |
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235 KB |
Mar/Apr 2006, Vol. 30, No. 2 |
| Should the measurement bandwidth match the frequency range of interest for impact testing? |
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272 KB |
Jan/Feb 2006, Vol. 30, No. 1 |
| I ran a shaker test with a simple beam, but some of the modes don’t look right – What’s wrong? |
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216 KB |
Nov/Dec 2005, Vol. 29, No. 6 |
| Sometimes my impact force is very smooth just as expected, but often it looks like it is oscillating – Why is that? |
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164 KB |
Sep/Oct 2005, Vol. 29, No. 5 |
| Why does my stability diagram of a component on a system show modes that the SUM and MIF don’t show? |
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293 KB |
Jul/Aug 2005, Vol. 29, No. 4 |
| When I perform impact testing, the input spectrum looks distorted – do you think my FFT analyzer has a problem? |
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190 KB |
May/Jun 2005, Vol. 29, No. 3 |
| I know that certain shaker excitations have different characteristics – but, which is the best to use? |
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372 KB |
Mar/Apr 2005, Vol. 29, No. 2 |
| Once I have set up a good measurement, is there any reason to watch the time and frequency results for every FRF? |
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223 KB |
Jan/Feb 2005, Vol. 29, No. 1 |
| Do mode shapes of a plate have any particular predetermined order? |
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276 KB |
Nov/Dec 2004, Vol. 28, No. 6 |
| I find overload and underload of the digitizer and range settings difficult to understand. |
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210 KB |
Sep/Oct 2004, Vol. 28, No. 5 |
| Is there any way to scale mode shapes without a drive point measurement? |
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177 KB |
Jul/Aug 2004, Vol. 28, No. 4 |
| Do I need to have an accelerometer mounted in the X, Y, and Z directions to do a modal test? |
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311 KB |
May/Jun 2004, Vol. 28, No. 3 |
| Number of points needed for a Modal test and the necessity of defining the entire shape. |
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284 KB |
Mar/Apr 2004, Vol. 28, No. 2 |
| What's the difference between local and global curve fitting? |
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469 KB |
Jan/Feb 2004, Vol. 28, No. 1 |
| Why do some measurements have antiresonances and others do not? |
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348 KB |
Nov/Dec 2003, Vol. 27, No. 6 |
| I ran a Modal test on a portion of a structure of concern and many modes look the same! What did I do wrong? |
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357 KB |
Sep/Oct 2003, Vol. 27, No. 5 |
| Must you have multiple references in order to find pseudo repeated roots? |
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221 KB |
Jul/Aug 2003, Vol. 27, No. 4 |
| Is it really necessary to reject a double impact? |
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440 KB |
May/Jun 2003, Vol. 27, No. 3 |
| Why are calibration and mode shape scaling important, and does it make a difference? |
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250 KB |
Mar/Apr 2003, Vol. 27, No. 2 |
| Is it better to collect averaged FRF data for a Modal test, or collect time data and process it afterwards? |
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591 KB |
Jan/Feb 2003, Vol. 27, No. 1 |
| What are some of the major mistakes people make in Modal tests so I don't make the same ones. |
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189 KB |
Nov/Dec 2002, Vol. 26, No. 6 |
| Is there any real advantage to MIMO testing? Why not just use SISO and then move the shaker? |
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254 KB |
Sep/Oct 2002, Vol. 26, No. 5 |
| Can you explain the basic steps to acquire data for Modal testing? |
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257 KB |
Jul/Aug 2002, Vol. 26, No. 4 |
| What's the difference between a complex mode and a real normal mode? |
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236 KB |
May/Jun 2002, Vol. 26, No. 3 |
| Which window is most appropriate for the various types of Modal tests performed? |
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282 KB |
Mar/Apr 2002, Vol. 26, No. 2 |
| Can the test setup have an effect on the measured Modal data? Do the setup boundary conditions and accelerometers have an effect? |
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258 KB |
Jan/Feb 2002, Vol. 26, No. 1 |
| Should I use all collected measurements when estimating modal parameters? Let's discuss this. |
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223 KB |
Nov/Dec 2001, Vol. 25, No.6 |
| What are some of the most important things to consider when impact testing? Let's discuss this.
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296 KB |
Sep/Oct 2001, Vol. 25, No.5 |
| Is there any benefit to using multiple references? I thought that only one reference was necessary. Let's discuss this. |
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495 KB |
Jul/Aug 2001, Vol. 25, No.4 |
| When impact testing, can the use of the exponential window cause any problems? Let's discuss this. |
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647 KB |
May/Jun 2001, Vol. 25, No.3 |
| Does it make any sense to use the actual operating load as excitation force for modal test if the force is a random signal? |
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489 KB |
Mar/Apr 2001, Vol. 25, No.2 |
| I hear about SVD all the time. Could you explain it simply to me? |
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456 KB |
Jan/Feb 2001, Vol. 25, No.1 |
| Why is mass loading and data consistency important for modal parameter estimation? |
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338 KB |
Nov/Dec 2000, Vol. 24, No.6 |
| Someone told me SDM will never work because you don't have all the mode shapes of the system. |
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220 KB |
Sep/Oct 2000, Vol. 24, No. 5 |
| How many points are enough when running a modal test? |
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463 KB |
Jul/Aug 2000, Vol. 24, No.4 |
| I ran one test with an X-excitation and can see some of the modes, and another test with a Y-excitation and see some different modes. Could I use an oblique angle instead?
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458 KB |
May/Jun 2000, Vol. 24, No. 3 |
| I showed some mode shapes to someone and they asked if the design was OK.
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537 KB |
Mar/Apr 2000, Vol. 24, No. 2 |
| I'm still overwhelmed by all this modal stuff - give me the big picture!
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682 KB |
Jan/Feb 2000, Vol. 24, No. 1 |
| I heard someone say "Pete doesn't do windows" What's the scoop?
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243 KB |
Nov/Dec 1999, Vol. 23, No. 6 |
| Are you sure you can get mode shapes from one row or column of H?
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203 KB |
Sep/Oct 1999, Vol. 23, No. 5 |
| What's the difference between operating deflection shapes and mode shapes?
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483 KB |
Jul/Aug 1999, Vol. 23, No. 4 |
| I still don't understand curvefitting. How do I get mode shapes from FRFs?
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443 KB |
May/Jun 1999, Vol. 23, No. 3 |
| Curvefitting is so confusing to me! What do all the different techniques mean?
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421 KB |
Mar/Apr 1999, Vol. 23, No. 2 |
| Which shaker excitation is best? Is there any difference?
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491 KB |
Jan/Feb 1999, Vol. 23, No. 1 |
| Should I always use a hard tip for impact testing so the input spectrum is flat over all frequencies?
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522 KB |
Nov/Dec 1998, Vol. 22, No. 6 |
| Is there any difference between a roving hammer and roving accelerometer test?
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445 KB |
Sep/Oct 1998, Vol. 22, No. 5 |
| Is there any difference between a modal test with a shaker excitation or impact excitation? |
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484 KB |
Jul/Aug 1998, Vol. 22, No. 4 |
| Could you explain the difference between the time domain, frequency domain and modal space? |
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487 KB |
May/Jun 1998, Vol. 22, No. 3 |
| Could you explain modal analysis for me?
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640 KB |
Mar/Apr 1998, Vol. 22, No. 2 |
