Lateral excitation stand.

MB Dynamics has announced the global market introduction of its Lateral Excitation Stand.

The MB Dynamics Lateral Excitation Stand can be used to help reduce measurement errors which can arise during experimental modal surveys. It does so, by offering versatile modal exciter suspension and support, as well as by applying force to a test structure in one of two unique ways: either horizontally, into the side of a test structure; or, obliquely, beneath a test structure. The stand further allows exact modal exciter positioning, in either horizontal or vertical direction, while still accommodating a maximum suspended load of up to 60 kg.

Designed by 40-year global industry experts in experimental modal analysis, the stand offers seamless compatibility with MB Dynamics’ own industry best-selling MODAL 50A and MODAL 110 exciter systems, of which more than 1,300 remain successfully installed in the field. The main structural parts of the Lateral Excitation Stand are constructed of a lightweight, durable, and rugged aluminum, while its rubber-footed adjustable steel legs offer added stability.

The Lateral Excitation Stand may also be used in combination with tensioned piano wire or compression stingers to help reduce measurement errors arising from unmeasured transverse forces. This, given that tension-only stingers can be used to apply axial forces without the typical sideloads which can otherwise contaminate measured data. When a piano wire stinger is properly suspended via four supplied turnbuckles, it connects to a test item’s force sensor via the modal exciter’s through-hole and corresponding base, along with any required inertial masses. The piano wire stinger then wraps around a pulley. Any required static preload force is applied via a small hand winch, with a series of quarter-turn handles used to secure the lateral arm and pulley. A low gear-ratio hand crank facilitates easy vertical adjustments of the suspended stinger over a range of 305 mm to 1415 mm. Upon application of sufficient static preload forces, as to exceed dynamic force, the piano wire stinger is secured by tightening the Dumore Chuck within the exciter’s moving element. As the Lateral Excitation Stand allows the modal exciter to be set atop its lateral arm and rotated more precisely about its trunnion base, the MODAL 50A or MODAL 110 exciter system can therefore provide excitation at virtually any angle, with up to a 300 mm horizontal adjustment rate, and with exciter motion properly isolated from the test stand.

Typical applications for the MB Dynamics Lateral Excitation Stand include virtually any experimental modal survey application incorporating the company’s own MODAL 50A and MODAL 110 exciter systems. These include, though may not be limited to, aircraft and automotive testing, civil engineering, power generation, and test & measurement applications. 

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1300 exciters!

MB Dynamics have announced the 1300th successful field installation of its Modal 50A exciter. With this milestone, the Modal 50A has now become MB Dynamics’ best-selling modal exciter worldwide.

The Modal 50A exciter was 100% designed and developed at the company’s USA based global corporate headquarters and R&D center, by an in-house engineering team that is comprised of multiple 40-year global experts in modal testing. Several team members were also formerly professors at the famed University of Cincinnati Structural Dynamics Research Laboratory.

Key R&D goals for the MB Dynamics Modal 50A exciter centered around addressing the most common problems associated with the use of traditional shakers in modal testing. At the time of initial Modal 50A design, most industry modal exciters lacked portability; had complex setup and installation requirements; and exhibited certain operational accuracy deficiencies. The Modal 50A exciter therefore needed the necessary reliability and performance for support of a diverse array of modal and structural testing requirements, ranging from smaller test articles up thru mid- to full-size automobiles. MB Dynamics aimed to accomplish this versatility, while still ensuring a modal exciter which could reliably deliver 50 pounds of dynamic force.

The 1” pk-pk continuous stroke (optional 30 mm pk-pk) of the Modal 50A exciter, with 1.1” between stops, offers reliable and sufficient excitation for both flexible structures and low-frequency “suspended shaker” tests. Its lightweight (less than 0.33 lbs.) armature provides a reliable excitation source for the modal testing of small articles with minimized mass loading. A unique armature design allows for important and dramatic reductions in force drop-off at test article resonances. In addition, the Modal 50A’s broad usable frequency range, from DC to 5000 Hz, allows it to accommodate virtually any modal survey type, including multi-shaker random, single-point random, multi-point sine dwell, and burst random.

The relatively compact (11.5” x 7.5” x 9.25”) and lightweight (55 pounds inclusive of trunnion base) footprint of the Modal 50A facilitates its ease of installation within space constrained environments. The exciter, its easy-mount inertial masses, and related accessories may be easily setup and operated by a single person, including in remote locations. The trunnion base of the Modal 50A incorporates two unique hand-knobs and three screw feet, allowing for exciter adjustments to be performed at virtually any excitation angle. A quick connect/disconnect feature for additional masses is also used to provide large inertial restraint during low-frequency modal testing, while a series of quick disconnect turnbuckles allow for both adjustable suspension and ease of 6DoF positioning. Low armature axial suspension stiffness (<15 lbs./in) further ensures that Modal 50A exciter dynamics may be decoupled from the test specimen. The exciter can also drive cable lengths ranging from 30 to 100 (optional) feet.

The process of attaching the Modal 50A exciter to a test structure is simplified via streamlined onboard fixturing. This includes a center bore clearance hole which extends through the armature, housing, trunnion base and inertial masses, and which allows for unlimited shaker positioning along the stinger axis. A collet chuck allows for the gripping of either a “one size fits all” threadless stinger or a “piano wire” stinger, in sizes from 0.020″ to 0.12″ (0.5 to 3.0 mm). Use of the “piano wire” stinger decouples force inputs in all directions except for that of the driven axis, thereby avoiding cross-axis force measurement errors. An oscillatory force of 50 pounds keeps required preloaded tension to the stinger, thereby eliminating buckling problems, while still delivering exciter peak dynamic force. These and other combined features allow the Modal 50A exciter to provide superior forcing functions, along with the virtual elimination of common measurement errors associated with bending moments, side loads, and end-user reliance on traditional stinger compression loading functionality. 

Recommended optional accessories for the Modal 50A exciter, also available from MB Dynamics, include the MB500VI amplifier; an exciter system accessory kit; and the new lateral excitation test stand. The MB500VI amplifier, when used in combination with the Modal 50A exciter and as part of a seamless modal measurement system, can virtually eliminate mass loading effects on smaller test items. The accessory kit includes a full set of compatible hardware, such as chucks, turnbuckles, nuts, bolts, bolt-on masses, and wrenches for bolt-on masses and stingers, as well as a user manual and extra storage for both stingers and load cells.

In addition, the new MB Dynamics lateral excitation test stand provides versatile horizontal or vertical suspension and overall system support for the Modal 50A exciter during experimental modal surveys, including greater distributed input energy uniformity and improved signal-to-noise ratios.  

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Exciter system for Large-Scale Modal Testing.

MB Dynamics, Inc. (MB) has announced its Modal 1000 exciter system for large-scale modal and structural testing.

The MB Modal 1000 can excite sine forces of up to 4000N (900 lbf), with a 2-inch (50 mm) peak-to-peak stroke and 1. 5 m/s peak velocity (60 inches per second), at frequencies from DC to 2000 Hz. Both thermal shutdown protection and overtravel control are provided as standard features.

The unique armature design of the MB Modal 1000 incorporates a “weak” suspension. The suspension may be fine-positioned to the test article using DC current. This is a particularly useful feature within lower-frequency response applications, such as ground vibration testing, where a DC-coupled exciter/amplifier may be in use. The armature’s lower weight further minimizes mass loading effects on the test article while reducing force drop-off at resonance. This avoids test article contamination during parameter extractions at each natural frequency. Additionally, the use of weak suspension means that the armature applies no extra force. Exciter dynamics are therefore de-coupled from measured test article dynamics for improved measurement data integrity.

The MB Modal 1000 exciter system may be used as either a stand-alone unit or paired with an MB P-Series power amplifier. The amplifier is housed within a 750 mm high, 19-inch rack cabinet and operates from 208-240V AC single-phase power. Supporting stingers, used to apply forces to the test article without exciter interference, are also available, measuring hex rod x 400 mm long with ¼-28 threads on each end.

Beyond its unique standard features, the MB Modal 1000 exciter system is offered with several customization options. Among them, the end-user capability to operate supporting amplifiers directly from a PC, allowing for amplifier positioning closer to the exciters. Test reliability is therefore improved, as drive cable lengths are minimized, with reduced risks of diminished force outputs caused by cable voltage drops. Also available is an optional automated ON/OFF exciter cooling package. Here, the cooling package engages only when the exciter heats up, in direct response to increasing levels of requested modal excitation forces. This protects the exciter from overheating, a particularly useful feature when end-users must oversee multiple test setups. As the package only engages when necessary, energy requirements of both the exciter and cooling package are optimized. The cooling package may be further specified with an optional <60 dBA Quiet Enclosure. Other optional accessories include piezoelectric force sensors to 4448 N (1000 lbs.), in tension and compression modes, with 5 mV/lb. (1.1 mV/N) sensitivities; and a supporting accessory kit. Full engineering consulting support is also available upon request, with all services provided by recognized industry experts of more than 35 years.

Typical applications for the MB Modal 1000 exciter system include structural damage detection; larger-scale advanced structural dynamics investigations, of buildings, bridges and commercial aircraft; aerospace ground vibration testing; large-scale experimental modal analysis, incorporating MIMO, MISO, SISO and SIMO techniques; FEM correlation and validation; and smaller-scale structural testing with higher-level vibration inputs.

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