Brittle index

Such a description of the brittleness of a material has proved inadequate, since it did not relate to the magnitude of loading. Therefore Samsonov introduced the additional brittleness index of a material yp, which gives the rate of numerical increase of plastic deformation with increased force. 

An alternative method to quantify the brittleness of a seal rock uses the unconfined compressive strength derived from sonic logs. This method uses the brittleness index, BRl= UCSIUCSf c, where t/CS c is the unconfined compressive strength of a normally consolidated rock. UCS can be measured directly or is estimated from logs based on empirical correlations using the equation... 

The brittleness index [53] is a normalization of the energy released during a period of rapid crack growth with respect to the energy stored in the joint just at the onset of crack growth. It provides a quantitative measure of the behavior described here. 

Brittleness—Although not widely used, the brittleness index (BI) has been used to quantify the brittleness of a ceramic where BI = HIKi. ... 

The incorporation of a ceramic dispersion phase in a glass matrix leads to an increase in the effective hardness in comparison with that of the unreinforced matrix. On the other hand, metallic inclusions will usually have the opposite effect. The simultaneous modification of hardness (H) and fracture toughness (K c) in composite materials results in variations in the brittleness of the material, which can be quantified by the brittleness index (B), with B = HIKic [138],... 

Single crystals Peculiarity Elastic modulus (GPa) Test method Brittleness Index... 

However, more recently a new brittleness rationalized index, denoted and expressed in Jim , has been introduced by Quinn and Quinn from the National Institute of Standards and Technology (NIST) as the ratio of the deformation energy per unit volume to the fracture energy per unit surface area. This brittleness index is more accurate than the previous one because it includes three intrinsic properties of the material rather than only two. Therefore, brittleness can be described in terms of the micro Vickers hardness (HV), Young s modulus (E), and the fracture toughness of the ceramic materials (X, ), as described in the following rationalized Quinn s equation ... 

Other measures for brittleness have been proposed by Wu Keru and Zhou Jianhua (1987), such as the brittleness index BI determined as shown in Figure 10.33. It is defined as the ratio of elastic strain energy to irreversible strain energy, corresponding to the peak point of the a-e curve obtained in a compression test for ideal elastic and brittle material BI = 0 for ideal elastic and ductile materials BI = 8. 

Figure 10.33 Complete cr-s curve and brittleness index for a concrete specimen, after Wu Keru and Zhou Jianhua (1987).

Table 5.3. Brittleness Index of Cement Clinker Phases...

Brittleness. The propensity of a material to chip or fracture during manufacture or handling is known as its brittleness. Although brittleness is not frequently quantified, a brittleness index, BI, has been defined by Lawn and Marshall, as follows ... 

When contacted, a glass may deform (over some threshold load) irreversibly, that is, plastically and/or with fracture. It is of utmost importance to understand, control and tailor glass response. In this perspective, brittleness index introduced by Lawn and Marschall (1979) as the ratio of hardness and toughness is of great importance ... 

The brittleness index unit is so that is to be considered as a length... 

We introduced in Chapter 8 the brittleness index as the hardness-toughness ratio to characterize the competition between the plastic and brittle deformations of glass. Here again, a similar approach can be used instructively in order to balance the elastic and plastic deformations. Hence, we introduce hardness-elastic modulus ratios in order to quantify the competition between elastic and plastic responses. An instrumented indentation machine allows for extraction of hardness H and elastic modulus E-, different ratios have been considered, the simplest one being H/E. The higher the ratio, the higher the resistance to plastic deformation and hence the higher the elastic compliance of the film. 

Modulus of Elasticity, Strength, Fracture Energy, Brittleness Index (the ratio of elastic to plastic energy measured from the area under the - curve of a loaded specimen at peak load or some other selected point on the defending branch of it). 

By increase of the degree of silicate polymerization of HCP, i.e. to change the c-s-f (constituent, structure and interface) on atom-molecular level, we obtained PSC (polymerized silicate cement) of very high compressive strength of 344 MPa with a brittleness index of 0.63 (as brittle as a cement mortar of about mark 200)(4). 

Criterion based on shale mineralogy Sondergeld et al. (2010) investigated Barnett shale and noted that most brittle section of Barnett shales have abundant quartz, the least brittle have abundant clays,. Studies from Jarvie et al. (2007), Rickman et al. (2008, 2009), and Sondergeld et al. (2010) result in definitirm of a brittleness index in terms of volume fractions ... 

Brittleness index = Quartz/ (Quartz + Carbonates + Qays). 

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