Studying the modal properties of the structure under test is important to optimize the design of the test structure and to improve the NVH characteristics. Finite Element Analysis is widely used to obtain the mechanical properties of different objects. However, it is not only difficult to replicate the exact environmental constraints and boundary conditions but also challenging to obtain the damping ratios of the different modes. Experimental modal analysis not only helps in solving these issues but can also help in validating the results of the finite element model.Read More
Roving excitation or response? Uni-ax or Tri-ax? SIMO or MIMO?
A modal impact hammer test is broadly classified between two types: roving hammer and roving response. Each method has its own pros and cons.
Implementing the aforementioned methods to perform measurements in one direction (usually out-of-plane) using a single uni-axial accelerometer yields a row of FRF when roving hammer, or a column of FRF when roving sensor. In the case of a FRF column, it is necessary to switch the response and excitation of the DOF of each FRF signal to yield a row of FRF. Curve fitting the row of measured FRFs produces the modal parameters of the test structure.
However, some tests may use more than one accelerometer or measure data in more than one direction. Even though the basics are still the same, care must be taken while performing the experiment to ensure that there is either a complete row or a complete column of the frequency response function. If the resulting FRF signals does not contain this, then the natural frequencies, mode shapes and damping of the structure cannot be obtained.Read More
This month, as part of a routine ISO 9001 audit process, we made a slight revision to Crystal Instruments’ “scope of business" statement. It now states:
The design, production, sales and servicing of hardware and software for machine vibration monitoring, dynamic measurement and environmental testing.Read More
Measurements can be broadly classified into two categories: Static Measurements and Dynamic Measurements.
Dynamic measurements vary greatly over a short period of time (e.g., Vibration (Acceleration), Audio (Sound pressure), etc.). In these types of signals, we are mainly interested in the high frequency components so measurements down to DC are typically not necessary. For these measurements, we would use the AC input mode (or IEPE) which comes with a 0.375 Hz High Pass Filter. In most cases, the user sets another high pass filter to eliminate the low frequency components that are not needed. Crystal Instruments Spider-80X and Spider-80Xi systems are best suited for these types of applications.Read More
Crystal Instruments and Sentek Dynamics attended the 89th Shock and Vibration Symposium in Dallas, Texas. The symposium, which is organized by Shock and Vibration Exchange (SAVE), is regarded as the leading forum for the structural dynamics and vibration community to present and discuss new developments and on-going research. The technical paper presentations and tutorials offered at the symposium revolve around applications such as shock-ship testing, earthquake engineering, structural dynamics, and shock and vibration instrumentation techniques; attracting attendees from all over North America.Read More
As a heavily transportation reliant and automobile driving society, we have become dependent and quite trusting of the automotive industry for the seatbelt’s lifesaving properties. But, does one ever wonder how those seatbelt devices are certified for our utmost safety? Certainly, it is possible to monitor the speed and displacement as a safety check regarding how timely the seatbelt engages. There are few products on the market to ease the complexity of this testing and Crystal Instruments now offers one of such systems. The Spider-80SG integrates seamlessly with the IES 2098 Seatbelt Sensor. It is an accumulator and the accuracy of its readings depends on the voltage precision of the supply. The Spider-80SG provides this power and allows the counter to reset as needed.Read More
The Advanced Engineering Show was held in Birmingham, UK. The exhibition was located at the National Exhibition Center (NEC) in close proximity to the international airport. Various meeting points and discussion topics were dedicated to the aerospace industry, automotive industry, and more. The exhibition included many conferences highlighting the dynamic changes currently occurring within the fields of advanced engineering and manufacturing.Read More
EDM Modal 7.2 introduces a new type of modal testing called Multiple Input Multiple Output (MIMO) Stepped Sine. This technique has been implemented to allow users to control and monitor multiple channels according to an implemented control strategy.
The new release version of EDM 7.2 also has a new modal parameter estimation method called Poly-X which is Poly-reference Least Square Complex Frequency Domain (p-LSCF). This is a frequency domain-based curve-fitting method that is used to extract the modal parameters of the structure under test more efficiently.Read More
During the final week of September, Crystal Instruments hosted a National Sales Meeting for our North American distributors. We had 21 attendees consisting of partners from: Sage Technologies, The Wonderful Company, Midwest Measurement Products, APM, TMS, Instrumentation Resources Inc., MBA, Mimex, and Dalimar.Read More
Crystal Instruments and Sentek Dynamics attended the Automotive Testing Expo in Novi, Michigan. This event is regarded as the world’s largest vehicle, component, validation technology, and services exhibition. The show featured more than 400 exhibitors and over 9,000 attendees. It was an exciting dynamic to be a part of with many valuable interactions.Read More