Detection Of Tjb[Le Point Of Crack Mit.Tat1on Using Multi-Stage Random Sampling (Mrs] And Spatial Point Pattern (Spp)

ABSTRACT

Porosity is a majw defect in cast aluminum alloys affecting in particuIm, the fatigue

strength. l%e pom sewe cr9 points of saess concenmrion mdpolnts of crud initiation

for evenfwI f~ilwe. In this work Fractal undysis was used to numericdy

chmucferke the pores in mi-directiondly solidfleddl 4.5 WI % Cu alloy microgrqhs,

nrnlsverse section at a distance of I4mm porn the mefaUchitl mold inteflme. l%e

Spatial Point PaTtern (SPP) and the Multi-stage randbm samplng (MR$l methd were

used 10 determine the distribvtion ofthe md the point of crack initiation leading

to mimd failure. i%e h4RS method reveah that aJI the pores cmidered we oj

irregular shupes, ii,e shrinkcrge pores, with sphericity B < 0.3. ne "worst" of the

shapes is ?he pore in the upper Iefl region with B 5.3078~-010a nd D = 1.8949. The

SPP method con- the result of th MRS method becaws crack inilialion will

commence in a region with ~Justeredpo res.

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