Fatigue data

The use of fatigue data and crack length measurements to predict the remaining service life of a stmcture under cyclic loading is possibly the most common application of fracture mechanics for performance prediction. In complex stmctures the growth of cracks is routinely monitored at intervals, and from data about crack growth rates and the applied loadings at that point in the stmcture, a decision is made about whether the stmcmre can continue to operate safely until the next scheduled inspection. 

Fig. 4. Fatigue data for high temperature alloys (a) As vs cycles to failure for various alloys tested under strain control. (°) = testing at RT in air ...

Fig. 28.5. Fatigue data for a typical structural steel in dry air. Note that, if the fatigue stress range is less than 440 MPa (the fatigue limit] the component should last indefinitely. The data relate to a fatigue stress cycle with a zero mean stress, which is what we have in the case of our tail drum.

Fig. 28.6. Fatigue data for welded joints in clean air. The class given to a weld depends critically on the weld detail and the loading direction. Classes B and C must be free from cracks and must be ground flush with the surface to remove stress concentrations. These conditions ore rarely met in practice, and most welds used in general construction hove comparatively poor fatigue properties.

Figure 6-4 Typical Tension-Tension Fatigue Data (After Pinckney [6-3])...

Scott, P. M., Design and inspection related applications of corrosion fatigue data , Mimoire et Etudes Scienlifique Revue de Milallurgie, pp. 651-660 (Nov. 1983)... 

Fatigue data are normally presented as a plot of the stress (S) versus the number of cycles (N) that cause failure at that stress the data plotted defined as an S-N curve (Fig. 2-43). The use of an S-N curve is used to establish a fatigue endurance limit strength. The curve asymptotically approaches a parallel to the abscissa, thus indicating the endurance limit as the value that will produce failure. Below this limit the material is less susceptible to fatigue failure. 

Since fatigue cracks often start at a random surface imperfection, considerable scatter occurs in fatigue data, increasing with the increasing lifetime wherever crack initiation occupies most of the fatigue life of a specimen. When a line of the best fit is drawn from the available data points on an S-N curve, this represents the mean life expected at any given stress level or the stress that would cause, say, 50% of the product failures in a given number of cycles. 

All of the uniaxial fatigue data reported to date have been generated using a fatigue testing machine built by MRC that is based on the principal of a wobble plate. The machine has positions for 30 specimens and is capable of operation at controlled... 

Fatigue data analysis, 13 494-495 Fatigue failures, 13 481, 486-487 Fatigue loads, 13 481 Fatigue performance, sample size and surface finish in, 13.486 487 Fatigue properties... 

Kaufman, J.G. Properties of Aluminum Alloys Tensile, Creep, and Fatigue Data at High and Low Temperatures, ASM International, Materials Park, OH, 1999. Kaufman, J.G. Introduction to Aluminum Alloys and Tempers, ASM International, Materials Park, OH. 2000. 

Compared with other structural materials there is a relative dearth of fatigue data for ceramics, and it is therefore not surprising that little is known of the fatigue behaviour of glass-ceramic matrix composites. It appears... 

Fatigue data of corrosion resistant steels and other relevant high strength materials are easy available for non-corrosive ambiance (air, oil). For the large variety of liquids applied in production processes the data have to be evaluated from special fatigue tests with corrosion cells. This paper answers the question if such uniaxial test results can be applied for the real component design in order to meet three-axial corrosion fatigue reality well. 

The corrosion fatigue data from uniaxial tests can be transmitted to the notched pulsating pressure loaded components quantitatively or with additional safety. The uniaxial pulsating stress yields to be the stricter criterion. 

The fatigue performance of these materials in a pavement cannot be inferred directly from these values of Kx and K2, for the actual fatigue behavior will depend upon such variables as thickness and stiffness and size of tire footprints. In addition, it is well known that laboratory fatigue data does not represent accurately the actual fatigue strength of pavements. A given material in a pavement can take 10-100 times as much strain under seal traffic loads as it can when loaded under laboratory conditions to the same number of load cycles. 

The influence of frequency on the S-N curve is shown for HIPS in Fig. 18. The general form of the S-N curve appears to change little with change of frequency. The fatigue data indicate that for PS, on reducing frequency by two decades, the average lifetime to failure is reduced by about a decade while for HIPS, with the same reduction in frequency of two decades, average lifetime is reduced about a decade and a half... 

Table 12 Dynamic Fatigue Data for Cordieritc Ceramic Diesel Filters in the Axial Direction...

The SN-curve is a line in the Oamp-N-plane (N is a measure of number of cycles to failure, S is a general symbol referring to stress, strain, load, displacement etc. In this case, S denotes aamp). When constant-amplitude fatigue data are available for the material, an SN-curve can be found using regression analysis of the test data. Usually, it is appropriate to... 

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