高速振動分析系統(tǒng) VIC-3D High-Speed FFT 

 非接觸式全場ODS工作變形與應變測量系統(tǒng) Non-Contact Full-Field ODS and Strain Measurement System 

 

 

技術概述 Technology Overview

VIC-3D HS FFT 系統(tǒng)是由CSI公司全新增加到 VIC-3D 產(chǎn)品線的測量解決方案, 它能夠以全場3D的方式查看、測量和分析在穩(wěn)態(tài)或瞬態(tài)事件中的全場工作變形 (ODS) 信息。該系統(tǒng)的納米級精度易于實現(xiàn)對工作變形 ODS基于頻域的查看和分析。系統(tǒng)為測得的任何頻率下的3D位移、應變、速度和加速度都提供了數(shù)以千計的數(shù)據(jù)點。其結果不僅是可視的, 而且用戶可以導出數(shù)據(jù)進行有限元分析和驗證。

The VIC-3D HS FFT System by Correlated Solutions, Inc. is a new addition to the Vic-3D product line of measurement solutions which enables full-field 3D viewing, measurement, and analysis of full-field operational deflection shapes (ODS’s) which occur from transient events.  ODS’s in the frequency domain can easily be viewed and analyzed with levels of accuracy in the nanometer range.  Three-dimensional displacements, strains, velocities, and accelerations are all computed for thousands of data points for any given frequency.  The result is not only visual, but users can export the data for FEA analysis and validation.

 

 

應用案例 Application Example

下面是系統(tǒng)的一個測量結果示例。 橡膠帶懸掛的一塊8″ x 10″薄鋁板從背面用一個小錘子敲擊。 沖擊產(chǎn)生了以下振型:
An example of the system’s results are seen below.  An thin 8″ x 10″ aluminum plate suspended with rubber bands was tapped from behind with a small hammer.  The impact produced the following shapes:

All ODS SS

To see another test, you can check out the brake rotor example on our Applications Page.

 

與傳統(tǒng)測量技術對比 Vs. traditional measurement techniques

  • 非接觸測量 – 由于 VIC-3D HS FFT 系統(tǒng)提供的是試件在動態(tài)或瞬態(tài)載荷下的非接觸全場振動分析, 該方法避免了傳統(tǒng)傳感器存在的問題, 比如在實驗過程中傳感器的脫粘或損壞 (特別是瞬態(tài)和沖擊加載)、傳感器的質量對試件的影響、 以及噪聲和電纜管理問題。
  • 全場數(shù)據(jù) – *不需要預先分析選擇測量點了！所有點的信息都可以很容易的通過后處理來發(fā)現(xiàn)和顯示識別。這意味著，不再需要為了確保結果的可靠性，而進行大量的預測試工作。
  • 3D數(shù)據(jù)結果 –  由于 VIC-3D HS FFT 系統(tǒng)始終測量所有X/Y/Z軸的數(shù)據(jù), 無需使用大量的單軸加速度計或昂貴的雙軸、三軸加速度計。
  • 綜合應變與位移數(shù)據(jù) – 系統(tǒng)自動生成全場應變、變形和振型信息，并伴隨所有的頻率和振幅數(shù)據(jù)。
  • 不需窗函數(shù) – 加窗處理被ODS專家描述為該領域的“必要之惡”。通過HSVA系統(tǒng)無需加窗函數(shù)，ODS分析人員不用考慮頻譜能量泄漏的發(fā)生。?(注：數(shù)據(jù)采集時由于使用矩形窗對信號的時間歷程進行截斷，從而造成了頻譜能量的旁瓣泄漏。使用其他的窗函數(shù)就可以改善頻譜能量的泄漏，如隨機信號使用漢寧、漢明窗，衰減信號使用指數(shù)窗等。)
  • Non-contact measurements– Since the VIC-3D HS FFT System provides non-contact full-field vibration analysis of components under dynamic or transient load, it circumvents the problems associated with the conventional sensors such as debonding or becoming damaged during the event (especially transient and shock loading), sensors adding mass to the test component, noise, and cable management.
  • Full-field data– Point selection can be overlooked completely!  Unknown nodes are easily discovered and displayed during post-processing.  This means that no pretesting is necessary to ensure reliable results.
  • 3D Results– Since the VIC-3D HS FFT system always measures in all three axes, orienting multiple single axis accelerometers or using pricey bi-axial or tri-axial accelerometers are no longer required.
  • Integrated strain and displacement data– Full-field strain, deformation, and shape variables are automatically produced along with frequency and amplitude data.
  • No Windows– The windowing processing has been described as a “necessary evil” by ODS experts in the field.  With the HSVA system, no windows are used, giving the ODS analyst confidence that leakage has not occurred.

使用VIC-3D HS FFT系統(tǒng)，不需要粘合劑、導線、信號分析儀、功率放大器或載荷傳感器即可獲得詳細的ODS結果。 測量微小、復雜的結構或非常大尺度的結構的ODS數(shù)據(jù)比更換一副鏡片更快更容易。

With the VIC-3D HS FFT system, there are no adhesives, wires, signal analyzers, power amplifiers, or load cells necessary for detailed ODS results.  Obtaining data for a tiny, complex structure or a very large one is faster and easier than changing a pair of lenses.

新的Vic-3D HS FFT窗函數(shù)選項 New Vic-3D HS FFT Windowing Options

最近CSI公司的軟件團隊開發(fā)并實施了一種對VIC-3D HS FFT系統(tǒng)獲得的FFT數(shù)據(jù)進行后處理的新方法。該方法可以將Hann和Hamming窗口函數(shù)應用于FFT數(shù)據(jù)，以獲得更清晰的工作變形ODS信息。這些窗函數(shù)功能對于需要更好的頻率分辨率但中等旁瓣沒有問題的噪聲測量很有用。

Recently, our software team has developed and implemented a new way to post-process FFT data obtained with the VIC-3D HS FFT System.  The Hann and Hamming window functions can now be applied to the FFT data to produce clearer operational deflection shapes. These window functions are useful for noise measurements where better frequency resolution is wanted but moderate side lobes do not present a problem.

All ODS SS

Hann窗函數(shù)具有良好的頻率分辨率并減少了頻譜泄漏。如果您不知道信號的性質，但要應用平滑窗口，請從Hann窗口開始。通常，這種折衷會導致頻率分辨率的輕微降低，但它會大大減少混疊。
The Hann window function has good frequency resolution and reduced spectral leakage.  If you do not know the nature of the signal but you want to apply a smoothing window, start with the Hann window.  Generally, it produces greatly reduced aliasing, though the trade-off is a slight decrease in frequency resolution.
 
Hamming窗函數(shù)在消除最近的旁瓣方面做得更好，但在消除其他旁瓣方面做得較差。雖然Hann窗的兩端都觸零，從而消除了所有不連續(xù)性，但Hamming窗還沒有達到零，因此信號中仍然有輕微的不連續(xù)性，其高度約為Hann窗的五分之一。
The Hamming window function does a better job of cancelling the nearest side lobe but a poorer job of canceling any others.  While the Hann window touches zero at both ends eliminating all discontinuity, the Hamming window doesn’t quite reach zero and thus still has a slight discontinuity in the signal, giving it a height of about one-fifth that of the Hann window.
 
下面是這些不同的窗口如何影響FFT數(shù)據(jù)的直觀視圖：
Below is a good visual representation of how these different windows can affect the FFT data: 

 

All ODS SS

 

使用窗函數(shù)的ODS測量 Operational Deflection Shapes Analyzed with Window Function

VIC-3D HS FFT系統(tǒng)實現(xiàn)了對瞬態(tài)事件產(chǎn)生的工作變形（ODS）的全場3D觀察、測量和分析。頻域中的ODS可以很容易地被觀察和分析，其精確度在納米范圍內。可以為任何特定頻率下的3D位移、應變、速度和加速度提供數(shù)千個數(shù)據(jù)點的信息。結果不僅是直觀可視的，而且可以導出數(shù)據(jù)為有限元分析和驗證。

The VIC-3D HS FFT system by Correlated Solutions enables full-field 3D viewing, measurement, and analysis of full-field operational deflection shapes (ODS) which occur from transient events. ODS in the frequency domain can easily be viewed and analyzed with levels of accuracy in the nanometer range. Three-dimensional displacements, strains, velocities, and accelerations are all computed for thousands of data points for any given frequency. The results are not only visual, but can be exported as data for FEA analysis and validation. 

 

 

與單點激光測振儀對比 Vs. single point laser vibrometers

  • 3D數(shù)據(jù)結果 – 由于VIC-3D HS FFT系統(tǒng)始終測量X/Y/Z三軸的所有信息，因此測量始終得到的都是3D結果。
  • 測量過程簡單 - 即使非常大的結構也可以在單個瞬態(tài)試驗中完成測量。 攝像機不需要移動或重新定位，即可從采樣數(shù)據(jù)中獲取更多數(shù)據(jù)。
  • 更快的采集速度 - 使用VIC-3D HS FFT系統(tǒng)，振幅不會影響采集時間。 即使在振幅非常大的超大結構上，全場數(shù)據(jù)采集時間也只需要幾秒鐘。
  • 綜合應變和位移數(shù)據(jù) – 全場應變，變形和形狀變量隨頻率和振幅數(shù)據(jù)一起自動生成。
  • 3D Results– Since the VIC-3D HS FFT system always measures in all three axes, 3D results are obtained with each test.
  • Simple procedures– Very large structures can be measured in only a single transient test.  The cameras do not need to be moved or repositioned at all to acquire additional data from the specimen.
  • Faster acquisition– With the VIC-3D HS FFT system, amplitude does not affect acquisition time.  Even on very large structures with very large amplitudes, full-field data acquisition time requires only seconds.
  • Integrated strain and displacement data– Full-field strain, deformation, and shape variables are automatically produced along with frequency and amplitude data.

VIC-3D HS FFT系統(tǒng)比單點激光振動計具有更強的穩(wěn)健性和穩(wěn)定性。 全場3D數(shù)據(jù)可以非?？焖俚孬@取，并且只需很少的設置和測試時間。

Single point laser vibrometers are not as robust as the VIC-3D HS FFT system.  Full-field 3D data can be acquired very quickly and with very little setup and testing time.

 

與掃描式激光測振儀對比 Vs. scanning laser vibrometers

  • 更小的設備尺寸 – 用于VIC-3D HS FFT系統(tǒng)的攝像機可安裝在單個三腳架上，這使得該系統(tǒng)非常便于攜帶。 您的3D振動測量系統(tǒng)在實驗室間或實驗室到現(xiàn)場間的測量轉換從未如此簡單。
  • 更低的經(jīng)濟投入 – 即使是最昂貴的VIC-3D HS FFT系統(tǒng)也只是3D激光掃描振動計系統(tǒng)價格的一小部分。
  • 更快的采集速度 – 使用VIC-3D HS FFT系統(tǒng)時，振幅不會影響采集時間。 即使在振幅非常大的超大結構上，全場數(shù)據(jù)采集時間也只需要幾秒鐘。
  • 綜合應變和位移數(shù)據(jù) – 全場應變，變形和形狀變量隨頻率和振幅數(shù)據(jù)一起自動生成。
  • Smaller equipment– The cameras used for the VIC-3D HS FFT system fit on a single tripod, which makes the system quite portable.  Moving your 3D vibration measurement system from lab to lab or out to the field for testing has never been easier.
  • Smaller price– Even the most expensive VIC-3D HS FFT system will be a fraction of the price of a 3D laser scanning vibrometer system.
  • Faster acquisition– With the VIC-3D HS FFT system, amplitude does not affect acquisition time.  Even on very large structures with very large amplitudes, full-field data acquisition time requires only seconds.
  • Integrated strain and displacement data– Full-field strain, deformation, and shape variables are automatically produced along with frequency and amplitude data.

激光掃描測振儀可以提供三維振動測量數(shù)據(jù)，但體積龐大且非常昂貴。 類比同樣的測量應用，使用VIC-3D HS FFT系統(tǒng)，您可以通過更優(yōu)惠的價格獲得更緊湊的設備。

Scanning laser vibrometers provide measurements in 3D, but are quite bulky and very expensive.  When compared to acquiring measurements with DIC, you can look forward to more compact equipment at a smaller price.

 

 

系統(tǒng)特性 System Features

  • 可查看、比較，動畫、圖形的形式提取和導出數(shù)據(jù)，便于有限元比較分析
  • 3D全場測量，高頻率(支持50kHz)下納米級分辨率的工作變形分析
  • *加速度條件下的極低振幅測量
  • 低加速度條件下的極大振幅測量
  • 同時提供全場應變，變形和形變量信息
  • 簡單的測量過程，即可獲取高精度的結果
  • 用戶界面友好
  • 投入只需激光測振儀系統(tǒng)價格幾分之一
  • View, compare, animate, graph, extract, and export data for easy FEA comparison
  • Measure 3D full-field, high frequency (50kHz max) operational deflection shapes with nanometer resolution
  • Measure extremely low amplitudes with extremely high accelerations
  • Measure extremely high amplitudes with low accelerations
  • Full-field strain, deformation, and shape variables are still available
  • Easy procedures, accurate results
  • User friendly interface
  • Only a fraction of the price of a laser vibrometer system

VIC-3D HS FFT系統(tǒng)的其他具體應用包括Other practical applications for the VIC-3D HS FFT System include:

  • 爆炸試驗 Explosive Testing
  • 關門試驗 Door Slams
  • 發(fā)動機運轉Run-ups/Run-downs
  • 沖擊試驗 Shake Testing
  • 跌落試驗 Drop Testing