Fatigue Strength of HFMI Treated Structures Under High R-ratio and Variable Amplitude Loading

Fatigue assessment of high‐frequency mechanical impact (HFMI)‐treated welded joints subjected to high mean stresses and spectrum loading

“…Based on recent data for high stress ratios R > 0.52, a minimum FAT class reduction of four (4) is proposed for 0.52 < R ≤ 0.7. 27 This R-ratio interval is chosen because the small number of data points with these stress ratios makes it difficult to justify a more refined division: only 28 data points representing different joint types with 0.52 < R ≤ 0.7 and only two data points with R > 0.7 were found in literature.…”

High cycle fatigue behaviour of impact treated welds under variable amplitude loading conditions

“…Several experimental and analytical studies have been conducted with the goal of generating S-N design curves (in terms of both the nominal and structural stress) to include the beneficial effect of HFMI treatment in structural design codes [5,7,[10][11][12]. The literature in this field includes experimental and analytical results for a wide variety of welded details and loading conditions in the mid-to high cycle domain (less than 10 7 cycles).…”

“…m = 5 was proposed based on the collected constant amplitude (CA) test results, mostly with a stress ratio (S min / S max = R) of 0.1, and the need for more variable amplitude (VA) test results for updating the design curves was highlighted. In another study [11], the existing high stress ratio (R = 0.5 to 0.7) CA test results and the limited available VA results on steel specimens were evaluated with respect to proposed IIW guidelines [15]. The S-N slopes for the different joint types varied between 4.4 and 9.6.…”

“…It is now well known that for a similar stress range, impact treatments are less effective under CA loading at higher R ratios [2,3,11]. For VA loading, however, the extent of the improvement depends on the stress history at the weld toe and seems to vary from one application to another.…”

The effect of compressive fatigue loads on fatigue strength of non-load carrying specimens subjected to ultrasonic impact treatment

“…Based on a large number of research, IIW (International Institute of Welding) recommendations on techniques for improving the fatigue strength of welded components and structures [1,2] are currently being developed. An extensive but not exhaustive list of publications [3][4][5][6][7][8][9][10] represents state-of-art in the field of fatigue strength improvement of steel structures by high-frequency mechanical impact.…”