Reference Materials

(Materials provided courtesy of Crystal Instruments)

Vibration Control

What's Required to Bring Vibration Testing In House? (5 MB)
Cover Story for March 2016 Sound and Vibration Magazine

A History of Vibration Test Controllers (Product Note #004, published in Sound & Vibration Magazine, 0.4 MB)
This article discusses the four generations of digital vibration control systems developed by US companies in the past 4 decades.

Understanding Random Vibration Testing Signals (Product Note #027, 6 pages, 2.43 MB)
Random vibration testing signals are explained and discussed for the testing professional.

Using Fatigue Damage Spectrum with Vibration Control (Product Note #028, 3 pages, 2.10 MB)
Fatigue Damage Spectrum (FDS) allows users to compare the potential damage caused by different Random profiles, swept Sine profiles or a combination of both.

Visualizing Mode Shapes with a Stroboscope and Cola Output (Product Note #029, 3 pages, 1.44 MB)
Product application note discussing the use of a stroboscope to visualize mode shapes with Crystal Instruments' Spider systems.

Random Control Feature: Non-linear Control (Product Note #030, 3 pages, 756 KB)
Crystal Instruments’ Random Control implements an advanced algorithm which compensates for the effect of non-linearity in the control loop, regardless of whether it is caused by the type of shaker system or the resonance of the device under test.

Sine - Resonance Search Track & Dwell Tracking (RSTD) (Product Note #31, 5 pages, 878 KB)
This product note demonstrates the use of Crystal Instruments’ Spider-80X along with EDM (Engineering Data Management) software to determine the resonant frequency of a test object with a very high Q and dwell on the resonant frequency along with tracking the changes in the resonant frequency using the phase value.

Random Control Feature: Multi-Resolution Control (Product Note #32, 6 pages, 945 KB)
The Multi-Resolution function perfectly fulfills the requirements of many Random profiles having details in the low frequency range and up to 2 kHz. Adequate loop time, spectrum refresh rate, and storage are maintained without using high resolution (large block size) that is not needed in the high frequency.

Multiple Shaker Control in EDM Software (Product Note #34, 7 pages, 1043 KB)
Multi-shaker control (MSC) is a unique feature offered by Crystal Instruments EDM Software versions 7.0 and above. The EDM MSC function enables users to view and monitor multiple shaker tests from one PC station. Users can observe testing status, view individual signals from different shaker systems, and send commands to each controller from one centralized application.

Center of Operation and Monitoring of 12 or More Shaker Systems with API (Product Note #039, 2 pages, 600 KB)
With these advanced features and robust qualities, Crystal Instruments has been successful in deploying 12 Spider controllers to control 12 shaker systems independently, which are being monitored through one PC from the API.

High Resolution Random Control at Low Frequencies (Multi-resolution) (Product Note #041, 3 pages, 588 KB)
The trade-off between control performance at low frequencies and the whole system response is always difficult, but Crystal Instruments has the solution: Multi-Resolution Random Control.

Automotive Multi-Sine (Product Note #042, 2 pages, 739 KB)
Multi-Sine is a new type of Sine test which facilitates multiple sine tones sweeping simultaneously at once. In automotive testing, engine mounted components such as fuel lines, turbos, headers, sensors, heatshield… are all subjected to high vibration levels during their operational life cycle.

Importance of Spectrum History Sine Signals in a Sine Test (Product Note #044, 3 pages, 366 KB)
Crystal Instruments uses Spectrum history signals, a special type of signals plot to conveniently plot a user defined signal property vs. time or cycles on the X-axis. To ensure the best readability and analysis, the plot is enhanced to accommodate the entire test duration even when the test durations run into several days, weeks or months. With the PC memory as the limitation, test durations of several months or even years can be plotted and viewed simultaneously, thus eliminating any necessity to section the data plot.

MIMO Vibration Control vs. Single Shaker Vibration Control (Product Note #046, 3 pages, 561 KB)
With the development of multiple shaker table systems, the availability of Multiple-Input Multiple-Output (MIMO) controllers and Multiple-Input Multiple-Output (MIMO) vibration control started emerging a couple of decades ago.

Multiple Shaker Table Systems (Product Note #047, 3 pages, 461 KB)
The Multiple Shaker Table System ranges from Multiple Exciter Single Axis (MESA) to Multiple Exciter Multiple Axis (MEMA) with 2 to 6 shakers involved (e.g., three axis translational shaker table, four-poster, 6 DOF Multi Axis Shaker Table (MAST), etc.)

Streamlined & Efficient Process of Viewing Signals Acquired in Vibration Tests (Product Note #048, 3 pages, 1.62 MB)
The repetitive manual addition and removal of signals to the display becomes a tedious task. (The purpose of this task is for viewing purposes or for comparisons of the same signals saved in different files.) The Review and Compare mode in EDM streamlines the process, rescuing us from the sheer boredom and inefficiency.

Vibration Tests for Seismic Qualification (Product Note #050, 3 pages, 838 KB)
Earthquakes are one of the most destructive forces of nature with the potential to cause devastating life and property losses. In addition to buildings and structures, equipment damaged by earthquakes may directly or indirectly generate hazards for people or the environment. For the safety of employees and the public, equipment designed to perform safety measures (e.g. shut down a reactor) or to function under certain levels of earthquakes for specified periods of time should pass a seismic qualification or a verification of earthquake resistance.

Multiple Channel Control Strategies for MIMO Vibration Control (Product Note #062, 3 pages, 535 KB)
Multiple-Input Multiple Output (MIMO) Testing has gained a huge momentum in the past decade with the development of multiple shaker table systems, the availability of MIMO vibration control systems, and the readiness of standards (e.g., MIL-STD 810G Method 527, IEST DTE 022 Working Group Recommendation).

Multi-Resolution Application in MIMO Sine Control (Product Note #064, 2 pages, 325 KB)
The tests discussed here were carried out on the Sentek Dynamics three-axis shaker system. Multiple MIMO sine tests were carried out to illustrate the effect of the multi-resolution method on the MIMO sine pretest.

Earthquake Testing on a Three-Axis Shaker System (Product Note #070, 3 pages, 623 KB)
Earthquake testing is a crucial process that is used to determine the seismic performance of a structure. The utilization of a physical testing method helps users better understand the complexity involved in earthquake forces. A shaker table is typically used to execute a physical method of testing.

Multi-Resolution Spectrum Analysis and Sine-on-Random Testing (Product Note #072, 3 pages, 833 KB)
In this article, we will discuss the benefits of using Multi-Resolution, a feature available in Vibration Control Systems, to offer a better frequency resolution in the lower frequencies of the Sine-on-Random vibration spectrum. The same benefits are also applied to the general Random test, and Random-on-Random mixed mode test.

Dual Excitation Shaker Push-push Testing (Product Note #073, 2 pages, 398 KB)
Here we examine the details of dual excitation shaker system testing. In this case, two shakers are placed horizontally, side by side. Driving bars are connected between the shaker armature and slip table for each shaker.

MIMO Control Null Test on Three-Axis Shaker Systems (Product Note #074, 3 pages, 530 KB)
The Control Null feature provided in Crystal Instruments’ Multiple-Input Multiple-Output Random vibration control software allows users to perform single axis or dual axis vibration control tests on a three-axis shaker setup with a simple setup in the software.

Swept Sine Test Measurement Strategy (Product Note #075, 2 pages, 392 KB)
A Swept Sine test is a type of vibration test where the controller excites one specific frequency via sinusoidal voltage drive. As opposed to a Random test, where a broadband of frequencies is excited together like white noise, the Swept Sine test produces a response with energy in the primary frequency and its harmonics (i.e., frequencies that are multiples of the primary frequency).

Output Ground Isolator (Product Note #076, 1 pages, 309 KB)
The output ground isolator is the most user-friendly solution for controlling multiple shakers while simultaneously improving accuracy of control and ensuring safe operation.

Sine Sweep in High Frequency Range (Product Note #077, 12 pages, 1.65 MB)
This article analyzes the obstacles to running a sine test over a high frequency range, including the dynamic characteristics of the Unit Under Test (UUT) and fixtures, the control dynamic range of the vibration controllers, and the sensor mounting locations. Several strategies and recommendations are then discussed with results.

Acoustic Control (Product Note #079, 3 pages, 530 KB)
Running a high intensity acoustic test requires an acoustic controller and an RATF. Crystal Instruments current EDM 10.0 software release provides Acoustic Control.

Introducing SRS Predictive Notching (Product Note #081, 3 pages, 443 KB)
In Sine or Random control, notching and limiting is a common technique used to limit the response level within a certain frequency range. Previously, users were not able to limit the SRS spectrum level within a certain frequency range for any response channel. Predictive Notching provides a limiting function for any input channel.

Linear and Angular Displacement Protection for Multiple-Exciter Single-Axis testing (Product Note #083, 6 pages, 825 KB)
The proposed Displacement Protection feature adds extra protections to testing equipment (including the shaker, armature, head-expander, slip-table and UUT).

Shutdown Protection System with Tracking Filters (Product Note #084, 11 pages, 1.87 MB)
Assessing the endurance of a device through shaker-induced vibration is a widely used technique that poses potential damage to the Device Under Test. The implementation a secondary shutdown protection system is crucial to mitigate the risk of substantial damage.

Intelligent Drive Clipping – A Better Sigma Clipping (Product Note #087, 13 pages, 2.05 MB)
Intelligent Clipping modifies the drive signal to minimize the loss in dynamic range of the profile.

Fatigue Damage Spectrum (Product Note #089, 7 pages, 812 KB)
FDS offers a valuable tool for design engineers. By analyzing the frequency content of a test, it pinpoints the frequencies most susceptible to damage.

Modal Testing and Analysis

Basics of Structural Vibration Testing and Analysis (Product Note #006, 14 pages, 2.69 MB) 
This application note provides an introduction to the basic concepts of structural vibration. It presents the fundamentals and definitions in terms of the basic concepts. It also discusses practical applications and provides real world examples.

Basics of Modal Testing and Analysis (Product Note #007, 12 pages, 4.15 MB) 
This paper discusses the concept of modal analysis, its applications where modal analysis is useful, data acquisition and visualization techniques.

Modal Testing On Hockey Sticks (Product Note #009, 3 pages, 1.1 MB)
Discusses how one popular hockey stick manufacture used the CoCo signal analyzer to characterize the modal behavior of their hockey sticks.

Modal Analysis on Strut Parts (Product Note #010, 6 pages, 490 KB)
Modal analysis is used to analyze the dynamic characteristics of structures and mechanical parts.

Modal Data Acquisition Using the CoCo-80X/90 (Product Note #015, 8 pages, 953.85 KB)
Explains how the CoCo-80X interfaces to the modal analysis software in EDM Modal (Engineering Data Management software) and how the modal data is captured.

Modal Testing Preparation Considerations (Product Note #033, 3 pages, 881 KB)
In this technical note, the emphasis is to discuss the necessary technical details regarding the preparation of a successful modal test to acquire a set of FRF signals.

Experimental Modal Analysis Overview (Product Note #043, 4 pages, 470 KB)
Experimental Modal Analysis (EMA) has developed into a major technology for the study of structural dynamics in the past several decades.

Modal Shaker Testing Using Periodic Random Excitation (Product Note #040, 4 pages, 744 KB)
Modal shaker testing is widely used for experimental modal analysis and to acquire frequency response functions. Either single or multiple modal shakers can be used. The type of excitation used may influence the quality of the testing result and frequency response functions.

Applications of Experimental Modal Analysis (Product Note #045, 4 pages, 543 KB)
With modal analysis results, quite a large number of applications are performed for a variety of industries. This note will discuss popular applications that are performed by engineering in industries such as aerospace, automotive, (etc.)

Modal Testing Excitation Consideration (Product Note #049, 4 pages, 582 KB)
There are several modal testing methods that consider different types of excitations used. Commonly known methods include Hammer Impact testing and Modal Shaker testing. Please note that Operational Modal Analysis utilizing Ambient Excitation will not be discussed here.

Operational Modal Analysis (Product Note #051, 3 pages, 738 KB)
The availability of an operational model opens the way for in-situ model-based diagnosis and damage detection. Hence, a considerable interest exists in extracting valid models directly from the operating data. This develops into the Operational Modal Analysis (OMA).

MIMO Stepped Sine Testing Technique (Product Note #055, 3 pages, 622 KB)
The EDM Modal MIMO Stepped Sine Testing option provides multiple Stepped Sine excitations to measure Frequency Response Functions (FRFs).

Understanding the Stability Diagram (Product Note #056, 3 pages, 548 KB)
The Stability Diagram is an effective way to display and identify the modes of a structure under test. Nowadays, the Stability Diagram is the standard method for the modal parameter identification stage. Read online here.

Poly-X, the Poly-reference LSCF Implementation and Experiment (Product Note #058, 4 pages, 671 KB)
A poly-reference least-square method for modal parameter identification of a system in frequency-domain is discussed and implemented. It can also be considered as a multi-reference frequency-domain implementation of the recognized time-domain based Least-Squares Complex Exponential (LSCE) estimator.

Multi-Resolution Spectrum Analysis in Modal Testing (Product Note #061, 3 pages, 482 KB)
Crystal Instrument’s EDM Modal software features multi-Resolution spectrum technology implemented into the MIMO FRF testing suite. Multiple passes of FFT yield a much finer resolution in the lower frequency region. This provides the advantage of a better estimation of the quality factor (or damping) and the amplitude of the frequency response functions at the resonant frequencies.

Comparison of Multi-Resolution Spectrum Technology and Regular FFT in Modal Analysis (Product Note #065, 4 pages, 626 KB)
Modal testing and analysis are crucial processes in the product development cycle. Sometimes the testing results are wrong by several magnitudes, especially in the low frequency bands where the frequency resolution is not sufficient. Crystal Instruments’ patented Multi-Resolution (MR) Spectrum technology helps overcome this issue with a unique solution. A modal test is carried out to examine data obtained through regular FFT technology and MR technology to quantify the modal results, such as damping, FRF amplitude, Auto-MAC chart, and mode shapes.

Introducing Testing Plan in EDM Modal (Product Note #066, 3 pages, 370 KB)
With Modal Analysis software, all DOFs on the mesh of a structure under test needs be measured. The common practice is using the Input channel setting, with one incremental value to move on to the next batch of measurement points till all DOFs are measured. With the newly released EDM 9.1 Modal software, the new Testing Plan will solve this issue by providing users the complete picture of the testing DOF layout. Also discussed in this note are the details of the Testing Plan feature.

Shaped Random & Burst Random Output Excitation in MIMO FRF Modal Analysis (Product Note #069, 3 pages, 422 KB)
Modal testing and analysis are important processes that improve the design of a product. Therefore, it is crucial to ensure testing is carried out with optimal settings. The Shaped Random and Burst Shaped Random output excitation introduced by Crystal Instruments provides unique advantages such as a better estimation of the quality factor, damping and FRF amplitude. This indicates that the obtained modal parameters are more accurate.

Ground Vibration Testing (GVT) of Aircraft Assembly (Product Note #080, 8 pages, 990 KB)
A Ground Vibration Test (GVT) involves carrying out modal analysis of an aircraft and its sub-assembly components to analyze and detect any changes in their structural properties.

Obtain Vibration Mode Using GPS Technology (Product Note #090, 35 pages, 4.16 MB)
This paper presents findings from an experimental investigation employing this novel approach to identify the frequency signatures of a building under ambient excitations.

Advanced Patented Methodologies in Ground Vibration Testing for Aerospace Applications (Product Note #093, 19 pages, 1.98 MB)
This paper presents an experimental case study showcasing the application of this patented technology on a fighter jet, demonstrating its effectiveness in aerospace, defense, commercial, and UAV platforms.