September 12, 2012 - LMS Engineering Services investigates an alternative methodology to obtain higher accuracy transfer function data of composite panels: through contactless excitation. Excitation without any mechanical contact does not influence the structural dynamics of the panel by mass or stiffness loading. This method results in more accurate data that can be used for correlation of a CAE model or to perform modal analysis.

Weight is an important design factor for the automotive industry. The use of more lightweight materials increases the need to understand the noise these new materials generate. Apart from the excitation mechanism, the dynamic characteristics of components are relevant for noise generation. The modal behavior of panels is traditionally obtained by structural FRF measurements with accelerometers and a hammer or shaker. However, conventional dynamic testing of composite materials influences the structural dynamics by mass or stiffness loading. To obtain higher accuracy transfer function data of composite panels in isolated conditions, LMS engineers used a high frequency source to excite a panel without any mechanical contact.

Soft springs dynamically decouple the panel from a supporting structure. The source excites the panel at a specific location. The high noise level of the source easily makes the panel vibrate. A laser vibrometer scans a set of discrete points on the panel to obtain the vibration response of the structure. The result is an FRF set which can be used for correlation of a CAE model or to perform modal analysis.

LMS Qsources – advanced excitation hardware

Covering a wide range of advanced excitation hardware, LMS Qsources seamlessly matches hardware with LMS software. This unique combination highly exceeds current market standards with regard to productivity and data accuracy, and, hence, customer’s expectations.

LMS shakers introduce dynamic excitation and are highly efficient for modal analysis and structural analysis. They benefit from their exceptionally small design without compromising on accuracy, functionality and reliability. The portfolio ranges from miniature shakers so compact that they can be mounted where conventional shakers have no access, to integral shakers that significantly improve the efficiency of testing by eliminating all of the support and alignment work associated with conventional shaker testing, to an inertia shaker designed for the very low frequency range.

LMS volume sources are sophisticated acoustic excitation devices that have been developed to acquire acoustic FRFs at low, mid and high frequencies without disturbing the acoustic sound field with its presence. The integrated volume acceleration sensors give a real-time feedback of the emitted source strength and can directly be used as a reference for FRF measurements without any post-processing.

LMS Qsources excitation hardware is used worldwide by OEM and suppliers, aeronautics, chemical industries and on large structures such as ships and windmills to improve the acoustic performance on complete system level.

You’ll find more information on the LMS Website on

• Transfer Path Analysis
• Qsources portfolio
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About LMS International

LMS, the leading partner in test and mechatronic simulation in the automotive, aerospace and other advanced manufacturing industries, helps customers get better products to market faster. With a unique combination of mechatronic simulation software, testing systems and engineering services, LMS tunes into mission critical engineering attributes, ranging from system dynamics, structural integrity and sound quality to durability, safety and power consumption. With multi-domain and mechatronic simulation solutions, LMS addresses complex engineering challenges associated with intelligent system design and model-based systems engineering. More than 1150 LMS professionals serve over 5000 manufacturing companies worldwide.

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Peter Vandeborne

Vice-President of Marketing & Communication, LMS Corporate

Email: Email Contact