Introduction

Experimental Modal Analysis (EMA) has developed into a major technology for the study of structural dynamics in the past several decades. Through Experimental Modal Analysis, complex structure phenomena in structural dynamics can be represented using decoupled modes consisting of natural frequency, damping, and mode shapes. The collection of these modal parameters is referred to as Modal Model. Experimental Modal Analysis is commonly referred to as Modal Analysis.

Structural vibration has been a significant focus for the dynamic testing and analysis group. Whether the object is a turbine blade rotating at high speed, or a bridge sustaining traffic and strong winds, Modal Analysis can be applied to provide insightful solutions.

Comprehensive Modal Analysis includes both data acquisition and the subsequent parameter identifications. From its inception till now, Modal Analysis has been widely applied in mechanical and structural engineering for designing, optimizing, and validating purposes. It has been widely accepted for broad applications in automotive, civil engineering, aerospace, power generation, musical instruments, (etc.), industries.

Jeff Zhao, Ph.D.August 28, 2017Structural Dynamics Testing

Automotive Multi-Sine Test

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. High cycle fatigue testing of engine mounted components is often done with a standard Swept Sine test. By performing a Swept Sine test, all resonances within the frequency ranges are excited and measured. Since the greatest fatigue damage happens at the excitation frequency and is also potentially high near these resonances, it is important to measure the vibration level at these frequencies. The standard Swept Sine only sweeps one frequency at a time with a single tracking filter. To test for fatigue, multiple sweeps need to be carried out for the entire frequency range at multiple times during a multiple sweeping rate.

Crystal InstrumentsAugust 18, 2017Environmental Testing

Remember when a Chief Scientist of CERN resigned from un-synchronized clocks?

In 2011, many of us read a startling news report of an experiment conducted by CERN claiming that neutrinos appeared to be traveling faster than the speed of light.

The collaboration of the experiment, called OPERA (Oscillation Project with Emulsion-tracking Apparatus), made headlines with its claim that a beam of neutrinos made the 730-kilometre journey from CERN, Europe's particle-physics lab near Geneva in Switzerland, to the Gran Sasso National Laboratory near L'Aquila, Italy, faster than the speed of light by about 60 nanoseconds. The result defied Albert Einstein’s special theory of relativity, which states this cannot happen.

James Zhuge, Ph.D. - Chief Executive OfficerAugust 10, 2017Structural Dynamics Testing

The European Automotive Testing Expo 2017

Developers of driverless and driver assisted instrumentation have many situations requiring perfect hardware performance. One such situation that has become evident to both Crystal Instruments (CI) and Sentek Dynamics is the increased requirement for vibration and shock testing of sensing elements used in autonomous vehicles, including: lidar, video cameras, radio cameras, and GPS computers. CI and Sentek witnessed this trend first hand while working closely with autonomous vehicle designers to provide the very best in vibration testing equipment of autonomous driving instrumentation.

Darren Fraser - Vice President of SalesJuly 31, 2017Non-applications

High-Resolution Random Control at Low Frequencies (Multi-Resolution)

Random control is a fundamental vibration testing for various industries and manufacturers of products. The FFT based control algorithm transforms time signals to the frequency domain where analysis, calculation, comparison…average, (etc.) are done. The performance of Random control is determined by how well the FFT describes the system characteristics. Proper spectrum resolution must be chosen in order to avoid missing any desirable observations and to meet the requirement of the control performance.

Tim Hsiao - Senior Product ManagerJuly 28, 2017Environmental Testing

Modal Shaker Testing Using Periodic Random Excitation

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.

Although sinusoidal types of excitation signals are occasionally used for modal shaker testing, these tests are typically performed using broadband random type excitation signals. Among these common excitation types, Pure Random is widely used. The Hanning window is generally applied to alleviate leakage caused by the non-periodic signal.

Another popular excitation type is the Burst Random excitation signal. It gained so much popularity because no window function is required. The requirement is to have the burst length selected so that the response decays enough at the end of each time block data. With this constraint, there will not be any leakage in the measurement and a windowing function is not required.

Two somewhat arbitrary types of excitation signals are Pseudo Random and Periodic Random. The characteristics of these two signal types will be discussed in detail here. The results of using these excitation types will be compared to the more popular Pure Random and Burst Random types. It will be shown that the cost of additional testing time is well worth the superior estimation of MIMO FRF signals.

Jeff Zhao, Ph.D.July 25, 2017Crystal InstrumentsStructural Dynamics Testing

Vibration Institute’s Annual Training Conference 2017 - Rochester, NY

The Vibration Institute’s Annual Training Conference is often referred to as offering ‘second to none’ education in vibration analytics and is considered the place to be for vibration and condition monitoring experts. As such, it has also become an excellent networking opportunity for industry elites, manufacturers, and incoming young professionals. With today’s ever accelerating changes in technology, beyond networking, it is also crucial to stay up to date on vibration analysis techniques with the most capable and usable equipment.

Center of Operation and Monitoring of 12 or More Shaker Systems with API

Manufacturing plants often require controlled vibrations on various parts of the plant to run for several hours, days, or even weeks at a time. In some cases, continuous operation is required.

At these facilities, the affordable down time is limited to a few hours in a week. The continuous controlling and monitoring of independently running systems is another significant challenge.

Mounting Strain Gage on UUT

Applying strain gages for measurement may sound daring, but it’s a lot simpler than it sounds. In this article, we will focus on key points of strain gage placement technique. It is important that the strain gage performs well and gives an accurate reading. This means the attachment point must be performed correctly to receive good results. As a result, the strain gage setup process requires a precise and correct following of directions. Crystal Instruments’ Spider-80SG is capable of calibrating and resetting measurement values prior to taking measurement. This is a standard step for all strain measurements to eliminate any offset before measurement starts.

Crystal InstrumentsJuly 21, 2017Crystal InstrumentsStructural Dynamics Testing

Post Process Data Acquired and GPS-stamped by the CoCo-80X

There are often instances where it may be beneficial to add location information to your acquired data. With the CoCo-80X, these GPS signals can be acquired simultaneously with other measurements -- there is no need to carry a separate GPS device. The CoCo-80X’s large LCD and touch-screen interface makes it easy to use the analyzer and acquire data. All measurements are combined into a single test file, so there’s no need to manage files.

You have ten fingers, but that doesn’t mean the input range has to be 10 volts!

I’ve always wondered why some instruments in the market set their hardware input range to 10 V. Perhaps the hardware designer for these instruments possessed ten fingers and chose 10 V out of convenience. I can imagine their bosses eagerly approving the use of 10 V as well, because they too have ten fingers!

EDM Modal Operates on Spider System with Hundreds of Channels

EDM Modal is a complete Modal Testing and Modal Analysis suite for Experimental Modal Analysis (EMA). It works on the verified Spider hardware systems, ranging from several channels up to hundreds of channels. EDM Modal is developed based upon the sophisticated technologies of modern modal analysis theory and technique. With its intuitive controls and powerful features, EDM Modal is the ultimate tool for modal analysis applications.

Jeff Zhao, Ph.D.June 29, 2017Structural Dynamics Testing

Synchronous Data Acquisition Across A Large Structure or Space

Synchronizing Spider-20Es to a High Channel Count System
Dynamic data acquisition and machine monitoring in factories and plants often require data to be acquired synchronously at various parts of the plant or a factory. Some big machines, especially in the aerospace industry also require data to be acquired at different areas synchronously.

Breakout Box Terminal Guide for Strain Gage Measurement on Spider-80SG

A. Introduction
Strain gages setup on our Spider-80SG is one of the most common questions we received. The Spider-80SG is designed to be used with strain gages; wonderfully, software interface is still within the same easy-to-use and intuitive platform of our EDM software. The connection to Spider-80SG breakout box is the final piece of the puzzle and it is a lot simpler than it looks.

Crystal InstrumentsJune 23, 2017Structural Dynamics Testing

SAE Noise-Con 2017, Sponsored & Attended by Crystal Instruments

What does an automotive engineer, electric engineer, and an airline acoustics engineer have in common? They all had the amazing idea to attend the Crystal-Instruments-sponsored 2017 SAE Noise and Vibration Conference and Exhibition in Grand Rapids, Michigan in June 2017.

Brady Hiob - Sales EngineerJune 22, 2017Non-applications

Crystal Instruments Blog

Introduction