Three-point bend geometry

Figure 17.19. Diagram for a three-point bending geometry to determine the yield force.

FIGURE 10.12 Diagrammatic representation of the three-point bend geometry. (Adapted from Dynamic Mechanical Analyser 2980 Operator s Manual, TA Instruments, New Castle, DE, 1996.)... 

In order to investigate the deformation mechanisms operating under impact, double edge-notched specimens were subjected to impact loading in three-point bend geometry (8-10). The plastic zones formed around cracks grown subcritically in this way were sampled at different points by ultramicro-toming sections for examination by TEM. 

Figure 4.6 Shearing force V and bending moment M F/2 diagrams for three-point bend geometry.

The fracture stress of CVD diamond has been evaluated using the three-point bend geometry [15]. The details of these measurements and its relative merits have been discussed elsewhere [4,35]. 

The concept of in vacuo fracture as a means of sample preparation for adhesion studies has been developed in the author s laboratory in a gradual manner over many years. Initial studies made use of an impact fracture stage designed to provide an Izod (three-point bend) geometry for use with metallic samples that yielded intergranular fracture at cryogenic temperatures. This was modified for composites research. And small samples that are 30 mm in length and some 2 mm square (with fibers oriented in the 2 mm direction) could be accommodated in the... 

Fig. 9 Specimen geometries for fracture measurements a compact-tension, b three-point bending...

Specimen geometry for the three-point bending (TPB) test is shown in Fig. 9b. 

Figure 19.4 Schematic diagrams showing common fracture test geometries. Single edge-notched (a) three-point-bend, (b) tensile and (c) compact tensiem tests, each using specimens with razor-sharpened notches, are employed for fracture mechanics measurements of fracture toughness and fracture energy. The Izod (d) arxl Chatpy (e) tests are widely practised in industry to evaluate toughness, but use bluntly notched (or un tched) specimens and do not give fracture mechanics data...

Figure 4.5 Three-point loading geometry. Making a cut in beam allows the bending moments and shearing forces to be determined.

The maximum deflection Y occurs at x=L, i.e., Y =FVI2> El nd this equation could be used to determine E from the beam deflection. If one inspects Fig. 4.5, the three-point geometry can be viewed as two attached cantilever beams. Replacing Fhy FI2 and L by Ul in the cantilever beam deflection formula, the maximum deflection in three-point bending can be determined, i.e., Tp=FZ,V48 /. The resistance of a beam to bending depends on El (Eq. (4.9)), which is termed the flexural rigidity. 

Instead of calculating member stiffnesses from the coupon moduli and the section geometry, they may be determined from three-point bending tests on simply supported beams. Tests of this type on pultruded GRP sections have been reported elsewhere (references 6-8). 

The geometry of the standard Charpy impact test is based on a three-point bending of a rectangular beam with freely supported ends and the loading in the midway between the supports (Fig. 6.2). The striker to exert impact force can be a free-swing pendulum, falling weight, or servohydraulic driven tup. 

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