Triaxiality factor

Fig. 6.25 Trend of relative ductility (ductility indexed to the uniaxial monotonic traction value) vs. the triaxiality factor TF (experimental data from [34], theoretical data from [36])...

It has been shown in Sect. 6.6.1 how a multiaxial stress state can modify the ductility of a material. To this purpose the triaxiality factor (TF) was introduced with Eq. (6.41) as the ratio of the hydrostatic stress to the von Mises equivalent stress. It is quite logical to think that the TF should have an effect on fatigue... 

Zamrik, S.Y., Mirdamadi, M., Davis, D.C. A proposed model for biaxial fatigue analysis using the triaxiality factor concept Adv. Multiaxial fatigue ASTM STP 1191, 85-106 (1993)... 

Bubbles are formed instantaneously. This conclusion made in [33] is based on estimates taken from earlier works [37]. As seen from the above cited works by S. E. Sosin et al., this is not always true viscoelastic liquids under triaxial stretching stress are not destroyed instantly. The existence of an induction period may produce a considerable effect on foam growth kinetics upon free foaming, when pressure is lowered instantaneously from P > Pcr to P < Pcr in a melt with dissolved gas. However, it would appear that microfaults in polymer melts, which are caused by factors... 

It is actually the creep strength of a grouted soil (either in unconfined compression or triaxial compression, depending on the specific application) that should be used for design purposes, not the unconfined compressive strength. In the absence of specific creep data, the value of one-fourth to one-half of the unconfined strength may be used for applications. A suitable safety factor must be applied to these suggested values. 

Since many grouts and grouted soils are subject to creep phenomena, the tests must be long-term. Because strength increase due to confinement within a soil mass is an important factor, triaxial tests are indicated. 

Indeed, the size of the metal ion has been found to be a factor in binding. The a-e-a site on a six membered ring complexes only cations having ionic radii > 80 pm. The triaxial site, found on cu-inositol, prefers cat-ions that have ionic radii 60 pm, but <100 pm. 

Similarly, the group of logarithmic curves of cohesion vs. time of the rock are obtained shown in Figure 3, by a series of triaxial compressive creep tests at seven temperatures from 20°C to 300°C. In the same way as mentioned above we can also obtain the main curve (Figure 4) at the reference temperature at 20°C as well as the corresponding shift factor parameters (Table 2). 

C With rock salt temperature test, using thermal damage factor analysis method, can easily get high triaxial compressive strength of rock salt with temperature-dependent thermal effect equation, and the shear strength parameters of rock salt thermal damage formula, which are for salt cavern gas storage injection and production operations evaluation and analysis of the security and stability of reference. 

The empirical technique involves steps to correct laboratory-determined strength values on relahvely disturbed samples to an equivalent undisturbed strength. These strengths in turn are then corrected by an empirical correction factor to an in-situ strength (Table 6.10). A survey of the various methodologies is presented in Figure 6.26, which incorporates the various elements that are required to use the methods as well as comments on the applicability of each. A review of the various procedures indicates that most methods use information from consolidafion and triaxial strength tests. 

Degradation cfSoil Modulus Model pile tests suggest that an expression similar to that developed by Idriss et al. (1978) from cyclic triaxial tests on clay may be applied to describe the degradation phenomena of soil modulus due to cycling. Therefore, for the cyclic displacement model of degradation, the modulus degradation factor Dg may be approximated by the expression... 

For short-term or undrained loading analysis (( ) = 0) the factor N is zero and the factor N c is selected from Figure 10.43 for the anticipated relative embedment depth D/B and soil cohesion (a distance B above the anchor) in the soft rupture zone. The soil cohesion can be measured in place with a field vane or cone penetrometer or determined from laboratory tests on core samples such as the unconfined compression or triaxial CU test. If soil strength data are not available, the strength profile can be estimated using d CTot = 0.30, where the vertical effective stress (o J is estimated using a buoyant unit weight of 4 kN/m. ... 

Two of today s approaches to fracture study are summarized here. The first is based on the use of the stress intensity factor K. The second is based on the J integral. The latter approach is suitable for situations of ductile fracture with strong deformations (ductile materials, low stress triaxiality, and so on). 

The load equivalency factors were derived from terminal serviceability factor (pj values equal to 2.0, 2.5 or 3.0 and pavement structural number (SN) values equal to 2, 3, 4, 5 or 6. The lower p value represents a pavement with serious structural distress where maintenance is unavoidable. The upper value of 3.0 represents a pavement with structural distresses needing maintenance, if high level of service is to be provided. The SN values represent different pavement structures. A sample of the equivalency factors derived from flexible pavements, for pt = 2.5 and SN = 5, for the three types of axles (single, tandem and triaxial), is given in Table 12.3. All equivalency factors for flexible pavements can be found in tabular form in the AASHTO pavement design guide (AASHTO 1993). 

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