With conventional vibration testing using a shaker with a traditional mounting platform design, the test article is directly attached to the top surface of the armature with some base excitation applied, usually monitored by controlling prescribed acceleration. The device under test (DUT) is normally subjected to an operating environment, generic spectrum or an excessive environment to determine if the equipment is suitable for the intended service. A typical configuration is shown.
图1 – 典型的振动台振动品质试验布置
In the early days of modal testing with shaker excitation, smaller shakers were used to apply low level excitation to be able to measure a frequency response function. Usually the shaker was attached with a long rod, commonly referred to as a stinger or quill, in order to impart force to the structure. (The purpose of the stinger was to try to dynamically decouple the shaker from the structure.)
Because these traditional shakers were typically used for base excitation, the armature attachment configuration was not optimal. Usually, some type of left-right thread arrangement was made or af collar was designed to enable an easier attachment to the shaker. It was a rather difficult arrangement no matter how the connection was made. In addition, thought had to be given to shaker position and actual length of the stinger needed. If a different length stinger was needed, then the shaker needed to be reoriented and realigned as different stinger lengths were used for the modal test. Overall, the set up of the shaker for a modal test was very difficult and cumbersome.
Due to all these problems, thought was given to specific design configurations that were better suited for modal testing applications. This gave rise to the through-hole armature with a chuck and collet design (like gripping a drill bit on a hand drill) that enabled very easy attachment of the shaker to the modal test article. A long stinger can be slid into the shakers through-hole armature, threaded to the force transducer attached to the test article, properly aligned, and then clamped down with the chuck and collet at the appropriate length. These components are shown as an exploded view below and a video demonstrating actual installment is posted at http://www.youtube.com/watch?v=VP_X-8TUtOU. This design also accommodates stingers of different lengths if needed. This arrangement is so simple that it is difficult to imagine having to set up the test without this important feature.