Notch Beam Test

In additional results [97] for the fracture toughness, Kic, determined from a single edge-notched beam test, values of 3.6 MPa m (for a 100 pm SiC particulate preform) up to 6.2MPam (13 pm SiC) were reported. This trend is the opposite of that reported by Pickard et al. [91]. Values of the elastic modulus reported in this later work ranged from 261 to 328 GPa. 

Gic is the critical strain energy release rate and y bt is the fracture surface energy of crack initiation, often referred to as the notched-beam-test fracture-surface energy in refractory literature. Also note that the stress intensity factor (Eq. 8.58) was given in Eq. (8.49) as ... 

Shear 45 tension test, 10° off-axis test, rail shear test, V-notched beam test, plane-twist test, and torsion of thin-walled sample... 

A recent use of equation (5.73) to determine K,c values as a function of grain size for alumina compares results to notched beam tests. The broken arms of the beams were used for the indentation-strength in bending test (ISB). Thus a good comparative study was possible. Figure 5.16 shows the close correspondence between the ISB results and the earlier results of Rice et using a double cantilever beam method. 

Figure 7.10 Specimens for toughness measurement and ioading conditions. CT, NBT and DT for compact tension, notch beam test and doubie torsion respectiveiy.

For the notch beam test (NBT or SENB), stress concentration is... 

To convert Pa to psi, multiply by 1.45 x lO ". For a single-edged notched beam (SENB) test. Corresponding to a 4 pt. bend. 

We test the impact resistance of polymer plaques using the configuration shown in Fig. 8.8. We subject circular injection molded plaques to the shock of a falling weight with a hemispherical impacter. This test is also known as the Dart Drop Test . Samples can fail in a brittle or a ductile manner. Brittle samples often shatter. Ductile samples can split or a small disk may be punched out of their center. This test provides results that are analogous to those obtained from un-notched impact beam testing. 

There are two main techniques used to measure the fracture toughness of ceramics fracture stress and hardness indentation. The former measures the load to fracture of a pre-cracked specimen using a single edge notched beam (SENB) or a chevron notched beam (CNB) sample. The main drawback of this technique is ensuring that the crack tip is atomically sharp. The second method uses the crack formed at the corners of the indentation produced during a Vickers indentation hardness test. This technique is rapid and relatively inexpensive. However, the toughness values measured are those of the surface, unlike the values obtained by fracture of the pre-cracked beams which are a measure of the bulk material properties. 

Hardness was estimated by Vickers indentation on sintered gradient samples, thermal expansion coefficient measurements and elastic behaviour was tested on the different dispersions. Preliminary mechanical testing (single edge notched beam, 3PB-SENB) and oxidation tests were performed on sintered FGM s. 

Single-edge notched beam (SENB) test... 

Finally, a criterion was discovered. It was the notched beam ductility test, which seemed to pinpoint the abnormal behavior and to discriminate between acceptable and unacceptable materials of this type. 

Figure 4-2. Typical results from notched-beam ductility test.

ISO 23146, Fine ceramics (advanced, advanced technical ceramics) - Test methods for toughness of monolithic ceramics - Single-edge V-notched beam (SEVNB) method, (2008). 

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