Ball rebound test

Falling-ball rebound test, 244 Ferrocene-containing polybenzimidazole, 315... 

This test, also known as the ball rebound test, is very useful in evaluating the resilience of foams. The test consists of dropping a steel ball onto a foam specimen and noting the height of rebound. The apparatus, as shown in Figure 14-9, consists... 

As ball tests are impossible on thin sheet, rebound tests were made, using the Shore apparatus, on sheets of the thin series, possessing respectively 50 %, 100 %, and 300 % cold work. 

The Rebound Test, a test easily adapted to measurements over wide temperature ranges whereby a ball is bounced on the sample surface and the height of the rebound is taken as a measure of hardness. (Shore s name is sometimes associated with this measure of hardness.)... 

Falling plunger and ball machines are generally not popular in Europe, but one design is specified in ASTM D2632. ASTM 1054 describes the Goodyear-Healey rebound tester. Figure 9.6 shows the principles of some of the tests. 

This property of rebound resilience is very rarely specified, but it is a useful, fast, simple test that can be carried out quantitatively to assign the foam type to conventional or high-resilicncc types. The test is described in ASTM D. 574 95, Test H and consists of dropping a 16 mm diameter steel ball of weight 16.3 g onto the specimen, which preferably is in the form of the end product, or onto the foam at a minimum thickness of 50 mm. Plied-up samples are permitted without the use of cement. 

The so-called Shore hardnesses are measured differently for metals and plastics. With hard materials (metals), a scleroscope is used to measure the rebound of a small steel ball. This Shore hardness is thus measured by a dynamic method, which yields the rebound hardness (the impact elasticity of the rubber industry). Soft plastics, on the other hand, are tested with a Shore durometer. This measures the resistance to the penetration of the point of a cone through the contraction of a calibrated spring. The durometer thus works according to a static method, and yields the true Shore hardness as understood by the rubber industry. Like the Rockwell hardness, the Shore hardness is given in scale divisions. 

For hardness determination, different methods are possible scratching the surface, penetration of an indenter with static or dynamic loads, or rebound as a result of elastic material behavior. The methods with a penetrating indenter are the most important ones. The applied methods are distinguished, e.g., by the shape of the indenter. Brinell hardness is determined by a ball-shaped indenter, while Vickers hardness applies a pyramid-shaped one. After the indenting test with a certain load, the surface area of the indentation is measured which delivers a value for material hardness. Determination of Rockwell hardness uses the depth of the indentation instead of the surface area (Bargel and Schulze 1988). Independent of the method, the so-called surface hardness... 

A procedure for the determination of the hardness of a surface by dropping a ball from a fixed height above the surface and noting the height of rebound. This technique was first proposed by A. F. Shore, an American, in 1906. Although primarily for the testing of the hardness of metals, it has also been applied to a limited extent in the testing of ceramics. 

Figure 7. Master curve, in log-log coordinates, regrouping all tfie adhesive rebound critical heights (balls and projectiles), which allows one to determine, firom its slope P, the index n characterizing the viscoelastic behavior of the natural rubber sample tested.

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