Four-point bend specimen

D. Munz, R. T. Bubsey, and J. L. Shannon, Jr., Fracture Toughness Determination of A1203 using Four-Point-Bend Specimens with Straight-Through and Chevron Notches, Journal of the American Ceramic Society, 63[5—6], 300-305 (1980). 

Microcracks are also known to occur in the elevated temperature creep of alumina with little or no preexisting glass phase. For example, the development of microcracks during creep fracture of two hot-pressed aluminas, which were free of grain boundary glass films, was studied by Wilkinson et al.52 who employed tensile and four-point bend specimens. They found that the concentrations and morphology of the cavities and microcracks were strongly... 

C848- 76. Young s mouutus was also determined at room temperature by strain gaging a four-point bend specimen. Thermal expansion was measured as a function of temperature with a differential transformer. Thermal conductivity and specific heat were determined as a function of temperature via the laser flash method. ... 

Hofinger, L, Oechsner, M., Bahr, H.A., Swain, M.V., 1998. Modified four-point bending specimen for determining the interfacial fracture energy for thin, brittle layers. Int. J. Fract. 92, 213-220. 

Tests using a constant stress (constant load) normally by direct tension have been described in ISO 6252. This test takes the specimen to failure, or a minimum time without failure, and frequently has a flaw (drilled hole or notch) to act as a stress concentrator to target the area of failure. This type of testing, as well as the constant strain techniques, requires careful control of specimen preparation and test conditions to achieve consistent results (246,247). Use of a slow strain rate with a four-point bend specimen configuration and constant load has been suggested as a method for ranking materials for environmental stress-crack resistance (248). 

The test program was conducted on four-point bend specimens with a root radius of 0.25 mm under a rising step load-displacement controlled test method with the amplitude of the ripple load maintained constant and superimposed at each step load level. The hydrogen charging potential applied during ripple load testing was -1.2 V versus SCE in a 3.5 % salt water environment. 

The step-modified slow strain-rate or Rising Step-Load (RSL ) test produces an increasing stress intensity that is different at each step-load but remains constant with crack extension for a Chaipy-sized SE(B) four-point bend specimen while each load level is maintained constant for a period of time. The rising step-load test was developed as an accelerated low-cost test for measuring the resistance of steels and weldments to IHE or EHE [45,46 ]. The load is constantly increased under displacement control, but incrementally in steps with each step being sustained for a period of time so that the onset of subcritical crack extension can be detected, which is the threshold for the onset of IHE or EHE. The RSL test differs from the SSRTT, which measures the differences in ductility parameters over the... 

J. Joch, J. Zemankova and J. Kazda, Analysis of a Chevron Notch Four Point Bend Specimen by the Three Dimensional Finite Element Method, Comm. Am. Ceram. Soc., C154 C155, March... 

Figure 3. Tensile stress strain curves to failure for PSZT four point bend specimens at 23, 75, 86, 100 and 120°C assuming linear elasticity.

Figure 5. True tensile stress strain curves to failure of two different strain gauged PSZT four point bend specimens at (a) 23, (b) 75, (c) 86, (d) 100 and (e) 120°C.

Fig. 9. The four-point bend specimen for interfacial toughness measurement, and equivalent edge loading.

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