Impulse hammer test

Impulse hammer tests (IHT) are conducted to determine the building parameters without isolator attached and sinusoidal base excitation is used to determine the damping characteristics of the sliding bearings. The stiffness at the base provided by the linear springs is determined experimentally using a servo hydraulic closed loop universal test rig. As noted earlier a simple Bouc-Wen model is used to describe the MR damper hysteretic characteristic. Details of experiments on MR damper are discussed in Ali and Ramaswamy (2009b). 

Shock sensitive materials react exothermally when subject to a pressure impulse. The impulse may come from a hammer-like blow, such as used in the standard drop-weight test, or a compression, such as might be experienced in a deadheaded plant compressor or valve slamming shut. Normally, shock sensitivity increases with an increase in temperature. Materials that do not show an exotherm on the DSC are seldom shock sensitive. 

The impulsive force of impact corresponds more or less to that of a 1 kg drop hammer from a height of l8cm. The pressure of the friction test amounts to about 1 kg. 

Figure 8.12 shows the principal types of test. In the Charpy test a beam of the polymer is held at each end and is struck at its centre by a hammer with one or two knife edges, giving a three- or four-point impulsive bending stress, respectively. Figure 8.13 shows a diagram of a standard Charpy impact tester. In the Izod test the specimen is held at one end and struck at the other. For either test a notch is cut in the sample at the point where it is to break and the sample is placed in the tester with the notch pointing away... 

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