Sharp notch length

In Fig. 3.3, the comparison of experimental and calculated according to the Eq. (3.10) i values for samples HDPE at different T as a function of sharp notch length a is adduced. As one can see, a good correspondence of experiment and the offered theoretical treatment was received. The value E at T= 293K, obtained by superposition method, is equal to approx. 2.0 GPa, that corresponds well to corresponding values range, obtained in Ref [16]. 

FIGURE 3.3 The experimental (1 4) and calculated according to the Eq. (3.10) (5 8) dependences of elasticity modulus E on sharp notch length a for HOPE at testing temperatures... 

Now the equation for the fracture stress Of estimation as a function of and sharp notch length a can be obtained. In Ref [4], the following definition of stress intensity factor A j as a fimction of was given ... 

FIGURE 10.14 The dependence of impact toughness on fracture dimension for HOPE samples in tests with varied sharp notch length a (1) and testing temperature T(2) [47],... 

The Eqs. (8.1), (8.3) and (8.4) have been obtained above, which allow to estimate samples fracture stress as a fimction of and sharp notch length... 

The experimental confirmation of this postulate is adduced in Fig. 13.15 for PASF film sample, prepared from polymer solution in methylene chloride (the experimental value = 1.82, the theoretical one = 1.75). As one can see, the fracture stress growth at sharp notch length a enhancement is observed. 

FIGURE13.15 The dependence of fracture stress s on sharp notch length a for PASF film sample, prepared from solution in methylene chloride [1]. 

Deformation curves in Fig. 4 clearly show that materials cannot be considered linearly elastic, and therefore Eq. 2 cannot be used directly in this form. However, by subtracting from the sharp-notched specimen curve the flexural and shear deformation contributions given by the blunt-notched specimen curve, a curve accounting for the crack length contribution to the specimen compliance can be derived from the data of Fig. 4. Eq. 2 can then be rewritten as follows ... 

A variety of methods can be used to measure the surface energy of ceramics. One technique, of limited applicability (see below), is to measure the force needed to cleave a crystal by starting with an atomically sharp notch of length c. In Chap. 11, the following relationship between the surface energy. Young s modulus, and the applied stress at fracture (r,pp is derived ... 

The dependence of these functions (2.a) and (2.b) on the relative notch length for specimens with different fillet radii at the notch base (i.e. sharp cornered and fully rounded) is shown in Fig. 3. 

The recent advent of methods to introduce very sharp notches and, hence, very short ( 50 p,p.) initial crack lengths (e.g., ref. 8) will also allow us to obtain a greater understanding of the R curve response at scales more consistent with natural flaws. 

The stable crack in PASF film samples with a sharp notch has triangle form (Fig. 5.2) and, as calculations have shown, the ratio of crack length I... 

FIGURE 7.1 The dependence of local overloading coefficient (the Eq. (7.3)) on fractal dimension of chain part between clusters for 10 pol5aners, pointed out in Table 7.1. 1 - results of impact tests of HOPE samples with sharp notch, where figures indicated notch length in mm. In insertion the dependence is shown for the same 10 polymers [9]... 

Five typical polymer samples were selected for the considered effects quantitative estimation PS and HDPE, showing superplasticity availability PVS, showing intermediate behavior (it breaks down immediately beyond yield stress) typical brittle PMMA and HDPE samples with sharp notch on length 1.5 mm, showing also brittle fracture. The necessary rated parameters for them in elastic and viscoelastic (up to yield stress) and plastic (beyond yield stress) regions are adduced in Table 10.1. 

Figure 8.12 The diagrams of load-time P-t) for samples with a sharp notch by length 0.5 mm of initial HDPE (1) and HDPE/EP nanocomposite with epoxy polymer content 2.5 mass percentage (2). Testing temperature 293 K, strain rate...

Short lengths of tubing are easily cut off with the aid of a heavy gauge metal plate, secured to a substantial base and with a deep, sharp edged V-notch cut in the top. A large retort stand fitted with two clamps will support glass tubes to be joined with a handlamp. (Fig. 4.15.)... 

A rectangular bar of polymer of thickness B = S mm and width = 20 mm has a central notch of length a = 10 mm. The bar is loaded in a three-point bending test with an 80 mm span, S, at room temperature. The bar fractures when the force applied is 300 N. Calculate (a) Kjc for the polymer and (b) the force needed to fracture in a compact tension test a specimen of dimensions IT = 50 mm, J = 10 mm, having a single-edge sharp crack of = 25 mm. 

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