Fatigue fracture surface

Slides Fatigue fracture surfaces components failed by fatigue, e.g. gear teeth, half-... 

The fatigue fracture surface of a failed crankshaft and failed rod bolt in a diesel engine are shown in Figures 2.18 and 2.19, respectively. 

Figure 2.18 Fatigue fracture surface appearance of a failed crankshaft, showing beach marks on the lower part. The origin of the primary fracture is indicated by the arrow. (Reprinted with permission from ASM International. All rights reserved www.asminternational.org)...

Fig. 8a and b. Fatigue fracture surface of PS tested at a stress amplitude of 17.2 MPa and at 0.2 Hz a low magnification scan b higher magnification of region near fracture source... 

Figure 13 shows a typical fatigue fracture surface for a HIPS sample tested at 0.2 Hz at a low stress amplitude of 10.3 MPa. To note the effect of stress amplitude, these pictures should be compared with those of Fig. 9 obtained at a higher stress amplitude of 17.2 MPa. At the lower stress amplitude the fracture surface. Fig. 13 a, is markedly different from that of Fig. 9 a. Here fracture developed from a surface... 

Fig. 13a—c. Fatigue fracture surfaces of HIPS tested at a low stress amplitude of 10.3 MPa and at 0.2 Hz a Low magnification scan b Higher magnification near source c High magnification near transition region... 

Fig. 14a and b. Fatigue fracture surfaces of HIPS tested at 21 Hz in a tensile mode. The maximum stress was 17.2 MPa and the minimum stress was 3.4 MPa a Low magnification scan b High magnification scan... 

Fig. 22. A portion of the fatigue fracture surface beyond the last DCG band for the PS specimen of Fig. 20. Crack propagation direction from top to bottom...

Fig. 36a and b. Fatigue fracture surface of an SAN sample (30% AN-Group D) tested in tension-compression fatigue at 27.6 MPa and at 21 Hz a Low magnification scan b Higher magnification of banded region... 

Fig. 41a and b. Fatigue Fracture surFaces oF an ABS specimen tested at 17.2 MPa and at 0.2 Flz a Region near source showing DCG bands b High magnification oF region close to source... 

Fracture surface morphology varies with stress amplitude and test frequency as well as with composition and molecular weight. Even under fully reversed cycling, discontinuous crack growth bands have been observed on the fatigue fracture surface in PS, SAN and ABS but they have not been seen in HIPS. 

In ABS, where particle size is much smaller than in HIPS, the particles are less effective as craze initiators and the fatigue fracture surface shows evidence of considerable localized plastic deformation of the matrix polymer as well as of cavitation and/or loss of adhesion of the rubber particles. 

Fig. 3. Fatigue fracture surface of an ABS sample tested at 20.7 MPa and 0.2 Hz. Note DCG bands surrounding internal source of fracture...

Fig. 19a, b. SEM scans of fatigue fracture surface of dry samples, tested at 41.4 MPa and 2 Hz, of HMW, C-PMMA a Low magnification scan, b High magnification scan near the fracture origin... 

Fig. 29. Fatigue fracture surface of S-PS iono-mer sample with 4.8 mol% ion content. (From 1 0 0 M m Ref.courtesy American Chemical Society)...

Fig. 6. Fatigue fracture surface of PC showing the DCG bands (left) and the single-cycle striations...

Fig. 30. Plane strain, shear fatigue fracture surface in PC. The fracture surface is oriented approximately 4S to the load direction. Fracture occurs through coalescence of voided areas within a shear band. Repnnled courtesy of MatsumotC ...

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