INDEX notch factor

Figure 2.15 shows the variation in standard Izod impact strength (1 mm notch tip radius) with temperature for the same range of materials. By far the most temperature sensitive is the low-melt-index polypropylene (PP) copolymer. It is interesting to compare the sharp fall-off in notched impact strength with this material between 23°C and 0°C with the steady values obtained for falling weight impact strength for the same temperature range (Figure 2.16). The removal of points of stress concentration is thus the most vital factor governing the impact performance at tanperatures of 90°C and below.

Peterson [12-14] introduced a notch sensitivity index q, or simply q factor, defined... 

This actually means that if a notch sensitivity factor is introduced also for the fatigue finite life that, usually indicated as Idf, it will always be < Idfnotch sensitivity factor 4 at 1,000 cycles analogous to the q index already seen in Sect. 7.2 for the fatigue limit, so that it is... 

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