Impact test apparatus

Fig 5—2. Parts of Picatinny Arsenal Impact Test Apparatus... 

The literature reports several types of impact testing apparatus also known as fall hammer apparatus , for the determination of impact sensitivity of explosives. 

Many applications of ceramic composites will expose the material to impact damage. Here again, the amount of work which has been done in this arena is limited, and needs to be increased. Impact tests can be performed using drop towers or Charpy impact testing apparatus. Such measurements have been done at room temperature30 and the apparatus can be adapted for use at elevated temperatures. 

Thanks are due to CEAST, Turin, for assistance with the instrumentation of the impact test apparatuses. The PA6.6 G30 material in the form of extruded rods was kindly supplied by Radici NovaCips, Villa d Ogna, Italy and the POM G15 and POM G30 samples in the I orm of extruded rods were kindly supplied by Rhodia, Ceriano Laghetto, Italy. 

Figure 3. Picatinny Arsenal impact test apparatus.

For the impact sensitivity determination, several types of impact testing apparatus, known also as Fallhammer Apparatus, are used US Bureau of Explosive Impact paratus (BoE), US Bureau of Mines Impact Apparatus (BoM), Picatirmy Impact. >paratus (PA), German Bundesanstdt fur Materialpriifung. paratus (BAM), and others (Baum et al., 1959, 1975 Impact Sensitivity Test, 1962 Kamlet and Adolph, 1979 Koenen et al., 1961 Kohler and Meyer, 1993 McIntyre, 1980 Safety and Performance Tests, 1972 Sensibilite auchoc, 1987 Wollert-Johansen, 1978). 

Multiphase polymers are commonly toughened plastics which contain a soft, elastomeric or rubbery component in a hard glassy matrix or in a thermoplastic matrix. An example of the typical brittle fracture morphology of an unmodified thermoplastic is shown by SEM of nylon (Fig. 5.45A). Addition of an elastomeric phase modifies the brittle fracture behavior of the matrix, as shown in a fracture surface of a modified nylon (Fig. 5.45B). The modification depends on the composition and deformation mechanism of the material [204, 215], but normally it increases the fracture toughness and strength from that of the unmodified matrix resin. Impact strength, as measured for instance by an Izod impact testing apparatus, is affected by the dispersed phase... 

Figure 2 is an over-all view of the tensile impact testing apparatus. The recording controller, dewar flask, and distributor head assembly were used in making all four types of tests. Figure 3 is a section through the tensile impact specimen cooling chamber. 

Figure 5-6. Bureau of Mines impact test apparatus.

Figpre 8.12 (a) Specimen used for Charpy and Izod impact tests, b) A schematic drawing of an impact testing apparatus. The hammer is released from fixed height h and strikes the specimen the energy expended in fracture is reflected in the difference between h and the swing height h. Specimen placements for both the Charpy and the Izod tests are also shown. 

Examples of equipment for mechanical shock or impact testing are the BAM Fallhammer, the Rotter test, the thirty kilogram Fallhammer test, and the Bureau of Mines Impact Apparatus [45]. The latter is shown in Figure 2.31. 

Two types of results are obtained from mechanical sensitivity tests (1) no reaction, or (2) decomposition with or without an explosion. The magnitude of friction and the impact sensitivity reported is the smallest load at which a positive result has been noted. The objective of mechanical sensitivity testing is to establish whether or not the substance is sensitive under normal handling conditions. However, this objective may not be reached. The test results may not truly reflect process conditions because most testing is carried out at ambient temperature and pressure. Since results are dependent on the type of test apparatus used, the interpretation of the results for use in practical applications requires much experience in this field of testing. 

B) Drop Weight Impact Test used at LASL is a modified version of machine developed by E.H. Eyster R.F. Davis at the Explosives Research Laboratory, Bruceton, Pa and described in OSRD 5744(1945). The apparatus is known as "ERL Machine . 

A.J. Clear, "Standard Laboratory Procedures for Determining Sensitivity, Brisance and Stability of Explosives", PATR 3278 (Dec 1965) [Superseding PATR FRL-TR-25 (l )6l] Impact Test with Picatinny Arsenal Apparatus (pp 2-4 and Figs 1, 2, 3 4, pp 32-35) Impact Test with US Bureau of Mines Apparatus (pp 4-7 and Figs 5, 6 7, pp... 

In what follows we will describe some impact machines and impact tests, ie the apparatus and methods for measuring impact sensitivity. We will then present and discuss impact sensitivity data for common explosives obtained with these machines by different laboratories. Then we will briefly consider how impact sensitivity tests have contributed to the development of the theory of initiation of explosives. Finally, we will examine impact testing from a theoretical point of view... 

Impact Machines and Impact Tests. One frequently hears the remark that there are as many types of impact machines as there are explosives test laboratories. This is somewhat misleading. In reality, all laboratories use essentially similar equipment but test procedures, and test data analyses differ. Basically an impact machine is an apparatus that drops a steel weight from a pre-determined height onto a plunger or striker resting on top of the test sample which is placed on a steel anvil... 

Falling Weight (Impact) Test. Ten tests with 0.05 to 0.1 Og samples, using an apparatus having an anvil 1.27cm(0.5") in diameter, should show that the explosive is less sensitive than Picric Acid (PA)... 

Note A.J.Clear gives in PATR 3278 (1965) detailed descriptions of Impact Test with Picacinny Arsenal Apparatus (pp 2-4 with Fig 4 on p 35) and "Impact Test with US Bureau of Mines Apparatus (pp 4-7 with Fig 7 on p 38). He also describes on p 7 "Modified Impact Tests for Liquid Explosives", made with US Bureau Mines and PicArsn Apparatuses... 

Nj. The following tests are described Impact Test with PicArsn Apparatus (pp 2 to 4 with Figs 1, 2, 3 4 on pp 32 to 35) Impact Test with USBurMines App (4 to 7 with Figs 5, 6 7 on pp 36 to 38) Modified Impact Tests for Liquid Explosive Made with BurMinesApp and with PicArsnApp (7) Explosion Temperature Test (7 to 8 with... 

A comparison of the impact sensitivity data of explosives reported by various teams from different laboratories suggests that the results obtained generally vary and it is due to (i) differences in the ways in which the experiments are conducted and (ii) use of different type of impact sensitivity apparatuses. However, when all influencing factors are considered, it appears that there is a similarity between the results obtained by different testing apparatuses. 

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