Vibration analysis laboratory

The remote vibration laboratory consists of a client PC, a server PC, a Hewlett Packard HP 35670A four channel dynamic signal analyzer, an electrodynamic shaker and its amplifier, two accelerometers, an impedance head, and a experiment object -the boring bar-. The remote vibration laboratory is illustrated in Fig. 1. In the remote sound and vibration laboratory a Hewlett Packard HP 35670A four channel dynamic signal analyzer carries out the data acquisition and the subsequent signal analysis as well as producing the excitation signal.

The experiment is designed to reflect on a common vibration problem in the manufacturing industry, i.e. vibration in internal turning. The object under investigation is a boring bar used for internal turning in a lathe. Vibration problem associated with this type of process is considered to be an important and critical factor concerning the performance, the tool life, the surface finishing, etc. that finally ends up on the productivity and production costs negatively.

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Figure 1: Left photo; remote vibration analysis lab and right photo; electrodynamic shaker and its amplifier, two accelerometers, an impedance head, and the experiment object the boring bar-

In Fig. 2 a close-up of the boring bar with the impedance head, connected with the shaker via the stinger rod, and the two accelerometers is shown.

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Figure 2: The boring bar with accelerometers and impedance head, and also stinger rod and shaker.

To carry out calibrated measurements both sensitivity and frequency range for the sensors are required. In Fig. 3 The specification for each transducer used for the measurements on
the boring bar are given as well as the channel no. on the HP 35670A respective sensor is connected to

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Figure 3: Technical data for sensors and analyzer channel they are connected to.

The BTH laboratory is a client/server application and when the client is loaded in the users computer, the user will see the front panel of the signal analyzer in the web-browser, see figure 4

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Figure 4: Client software based on photo of the real equipment

Demonstration video of the remote vibration laboratory

You can try out the vibration laboratory by logging in as a guest.

Short introduction to internal turning

The laboratory experiments are based on a boring bar that is used for internal turning to machine the inner surface of a pipe-shaped work pieces. Internal turning is a typical example from the industry that generally is affected by vibration problems. In figure 1 a) a photo of an internal turning process is shown and in figure 1 b) a schematic description of internal turning is illustrated.

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Figure 1: a) Internal turning and b) description of internal turning.

In internal turning operations the boring bar is subjected to a stochastic excitation by the material deformation process during the machining of a workpiece. Boring bars are used for internal turning inside pipe-shaped workpieces and are usually slender. The slenderness of the boring bar results in a structure with low dynamic stiffness with respect to the excitation forces produced by the material deformation process during turning. This frequently results in substantial boring bar vibration during machining. Vibrations during internal turning operations degrade the surface quality on the work piece (see Fig. 2), reduce the tool life and frequently annoying acoustic noise.

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Figure 2: Work piece surface after internal turning.

If you have any questions about this page or the laboratory, contact the administrator.