Wedge-open loading specimen

WOL Wedge open loaded specimen (fracture mechanics)... 

FIG. 28-18 Specimens for stress-corrosion tests, (a) Bent beam, (h) C ring, (c) U Lend, (d) Tensile, (e) Tensile, (f) Tensile, (g) Notched C ring, (h) Notched tensile. ( ) Precracked, wedge open-loading type. (/) Precracked, cantilever beam. [Chem. Eng., 78, 159 (Sept. 20 1971).]... 

Fracture toughness specimens are sometimes contained in some older capsules, although the types of specimens are not always those recommended by current ASTM test methods. For example, the wedge-open loading (WOL) specimen was used in some early capsules since it is somewhat similar to the compact tensile (CT) specimen, it can be tested in a modified form to generate fracture toughness data. Converting Charpy V-notch... 

Conventional fracture mechanics testing specimens, such as the compact, cantilever beam, modified bolt-load compact previously referred to as wedge-opening load (WOL), and contoured double-cantilever beam specimens, have been adapted for testing in both aqueous environments and in a high-pressure gaseous hydrogen environment. 

The modified bolt-load compact specimen, originally referred to as the Wedge Opening Load (WOL) specimen under constant displacement (Fig. 17) is best used for quality control rather than performing research studies. In concept it C2in be used to measure the threshold stress intensity but the result are extremely sensitive to the various material environment combinations with retardation and crack blunting pla5ang a major role in the final test results, such that... 

One notable caution is in the use of precracked wedge open loaded (WOL) specimens. Nickel alloys are usually so ductile that a very thick specimen is required to obtain a plane strain stress state at the tip of the precrack. The minimum thickness required can be calculated from the following equation... 

WOL Type T specimen is wedge bolt-loaded as shown in Fig. 15.19. Type X specimen is no longer used. The development process continued till the introduction of the third type of specimen worldwide known as the Compact C(T) specimen of Fig. A.9c. Today the C(T) type specimen is the most used one in fracture mechanics applications. However, WOL Type T specimen is still used in see applications for measuring the stress intensity threshold Kj -cc (see Sect. 15.5). The h a/w) and V(a/w) functions for the calculation of the corresponding K and A for types WOL-T and C(T) specimens are listed in the following [6]. The symbols refer to Fig. A.9b and c for types WOL-T and C(T) specimens, respectively. A represents the crack mouth opening displacement (CMOD), i.e., the displacement measured at the notch opening on the specimen surface, as shown in Fig. A.9. 

A constant value of the wedge- or crack-opening displacement is used to generate the initial load for this type of specimen. As the crack extends, the stress intensity decreases until crack arrest occurs. The initial load is assumed to be slightly above Kehe- The specimen is maintained under these conditions for about 5000 h to establish the threshold. The crack extends to a point after which further extension is not measured (Kehe)- However, it is difficult to determine precisely when the "no-growth criterion is met. 

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