Brittle Versus Ductile Materials

FIGURE 13-19 Schematic plots of stress versus strain for brittle and ductile materials. 

Chip Formation (Abrasive Process), Fig. 2 Brittle material behavior versus ductile material behavior in grinding (based on Salje and Mohlen 1987 Klocke 2009)... 

Typical stress versus strain curves for brittle and ductile materials, showing the areas under their respective curves they are measures of the toughness of the respective materials. 

Beltz G. E., Lipkin D. M. and Fischer L. L., Role of Crack Blunting in Ductile Versus Brittle Response of Crystalline Materials, Phys. Rev. Lett. 82, 4468 (1999). 

Fig. 3.14a. Stress-rapture characteristic of HDPE pipes made of Hostalen GM 5010 T2. Compared to modem materials this outdated resin had very low resistance to stress crack and oxidative degradation. Therefore, the various failure modes could be observed within manageable testing times even at 60 °C. Zl, Z2, Z3 designate the sections of the hoop stress versus time-to-failure curve, which result from different failure modes Ductile failure with excessive deformation (Zl), stress crack formation and brittle failure (Z2) and oxidative degradation (Z3). The figure has been taken from reference (Koch et al. 1988)...

The processes in the range of ductile failure and in the intermediate range will now be briefly discussed to complete the description of the materials behaviour in the long-term tensile test. The branch of ductile failure in the stress versus time-to-failure diagram (or more precisely log crversus log tp) runs considerably flatter than the branch of brittle failure. Figure 3.18 shows typical stress versus time-to-failure curves. Within the range of high stresses ... 

The brittle transition region is that range of temperatures where the important response mechanisms of the material to stress are becoming inactive. This may be the mobility of dislocations for a metal, or the ability of the molecules to slide over one another in a polymer. Curves of ductility versus temperature for several important structural materials are shown in Fig. 3.4. 

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