Crack propagation rate

Total interpenetration of chains (X approaches Rg) is not necessary to achieve complete strength when M > M and x < 7). However, a word of caution while complete strength may be obtained in terms of critical fracture measures such as G c and A lc, the durability, measured in sub-critical fracture terms, such as the fatigue crack propagation rate da/AN, may be very far from its fully healed state at r. We have shown that while the weld toughness A lc increases linearly with interdiffusion depth X as K f. X, the fatigue crack propagation behavior of partially healed welds behaves as [1]... 

The stress corrosion resistance of maraging steel has been evaluated both by the use of smooth specimens loaded to some fraction of the yield strength and taking the time to failure as an indication of resistance, and by the fracture mechanics approach which involves the use of specimens with a pre-existing crack. Using the latter approach it is possible to obtain crack propagation rates at known stress intensity factors (K) and to determine critical stress intensity factors (A iscc) below which a crack will not propagate (see Section 8.9). 

Table 3.30 Crack propagation rates for a number of high strength steels ...

The fatigue behavior of a material is normally measured in a flexural but also in a tensile mode. Specimens may be deliberately cracked or notched prior to testing, to localize fatigue damage and permit measuring the crack-propagation rate. In constant-deflection amplitude testing a specimen is... 

One of the most striking characteristics of LME is a very high crack propagation rate compared with the rate in air or vacuum. The rate may vary from one system to another, but they all fall in the range of a few centimeters to several meters per second [13,14],... 

Exposure to seawater results in decrease in critical stress intensity factor and the susceptibility to SCC68 0.2% Fe improves the resistance to SCC presence of >5 wt percent of A1 increases the velocity of cracking Sn in the alloy decreases SCC resistance chloride bromide and iodide induce or accelerate SCC69 Occurs by trangranular cleavage of a-phase in which a-phase controls the crack propagation rate Intergranular corrosion due to formation of titanium methoxide... 

Figure 6.51 Corrosion fatigue crack propagation rate (da/dN) as a function of the cyclic crack tip stress intensity range (AK) (Phull)5...

At intermediate stress intensity levels (stage 2) the crack propagation rate shows a plateau velocity Vpiateau that is virtually independent of the mechanical stress, but depends on the alloy/environment interface and the the rate-limiting environmental processes such as mass transport of the aggressive species to the crack tip. The plateau in a quenched and tempered low-alloy steel of 1700 MPa yield strength in deaerated water at 100°C... 

In a FCP diagram, the crack propagation rate da/dN is illustrated as a function of the amplitude of the stress intensity factor AK ... 

Fig. 7 Plot of da/dN vs. crack propagation rate for W 33 CT specimens from cast PMMA at different constant AK levels...

Figure 12 right illustrates the effect of IPA. The experiments were first performed in air, as a reference, up to a crack length ratio of about 0.45 then the alcohol was added by the sponge without interruption of the experiment. Under the influence of the medium, the crack propagation rates changed instantly. The highest increase of about two decades accompanied... 

Fig. 15 Dependence of crack propagation rate da/df on DK for two PE-HD materials of different molecular weight in a 5% dispergator dispersion [82]...

Fig. 21 Influence of type of stabilizer on crack propagation rate in PE-HD in water at T = 80 °C static fracture mechanics...

Figure 26 shows FCP curves for PS with a higher molecular weight tested perpendicular to the injection direction with and without oil. In oil, an additional embrittlement can be observed by the steep increase in the FCP curve, which makes it almost impossible to measure the dynamics of crack propagation over a broad range of crack propagation rates. Still, testing perpendicular... 

---