U-notch

Molded sheets of the epoxies were cut into double-notch four-point bend (DN-4PB) specimens in accordance with the dimensions given in Figure 1. Because more plastic deformation can be promoted in a U-notch than in a crack, U-notched specimens were used. The U-notched DN-4PB specimens were loaded at... 

Figure 2. Bending fracture force versus rubber content for U-notched specimens.

Figure 3. Stress-whitened zone at the root of the U-notch of specimens after polishing. The specimens are viewed under a stereomicroscope, (a) Specimen RF5, Section A. (b) Specimen RH15, Section A.

Figure 4. Vertical extent of stress-whtteningfrom the root of the U-notch, Section A.

Control over steel properties is maintained by means of the DVMF impact test (This test uses a specimen with a large radius notch and discriminates between steels at temperatures well below the Charpy V- or U-notch transition). In Germany 5% nickel steel is more readily available than 3-1/2%, but either may be used down to -120°C if welded with austenitic electrodes. Below -120°C, an austenitic 23-Mn 3-1/2-Cr steel may be used in addition to 9% nickel and austenitic chromium nickel steel. The 23-Mn 3-1/2 Cr is cheaper than stainless steel but more difficult to fabricate and less readily available. 

Sahlgren C, Gustafsson MV, Jin S, PoeUinger L, I endahl U. Notch signaUng mediates hypoxia-induced tumor cell migration and invasion. Proc Natl Acad Sci USA 2008 105(17) 6392 397. 

Fig. 3. Low-temperature tensile strength (ob), tensile yield strength, 0.2% offset (a-02)y tensile elongation (5), and impact strength, assuming Charpy U-notch (Ah), of Invar 36 H and welds.

Ah - Charpy U-notch impact strength Av- Charpy V-notch impact strength... 

Fig. 5. Low-temperature properties of 0.03C, 13Cr, 19Mn, N steel (A A), 0.03C, 13Cr, 19Mn, 4Ni, N steel PD), and welds ( O) made by the submerged arc process. Av is Charpy U-notch impact strength.

The Charpy U-notch test refers to the ASTM E23 [12], Standard Test Methods for Notched Bar Impact Testing of Metallic Material. The test was used to determine fracture energy. A Tinius Olsen Change-O-Matic impact testing machine was used in this test. 

U-notched dynstat impact strength on is calculated from the absorbed energy An, related to the smallest initial cross-section area of the specimen at notch base ... 

Mineral Tensile strength (MPa) Tensile elongation (%) Tensile modulus, MPa (1% secant) Flexural modulus (MPa) Gardner impact U) Notched Izod impact strength 0/m)... 

Figure 3.21. Thin section of double U-notch specimen prepared at 1200 rpm for transmission microscopy (a) cross-polarized image showing deformation bands connecting between voids and (b) same section as (a) but without polarization. U-notch is located at the bottom [51]...

Fig. 2.9. Charpy U-notch data for some mild steels (53). (Courtesy of the American Weidfaif Society.)...

Impact Strength. Typical Charpy (U-notch) impact strength is 15 J (11 ft Ibf) at room temperature. 

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