I. Mangerig/R. Kroyer/M. Koller · Experimental and numerical analyses of the effectiveness of high-frequency peening processes
Fig. 15. Load state t1 " 1.0, maximum main stresses X1 and maximum main distortions J1: a) technique 1 and b) technique 2
Fig. 16. Load state t1 Y " 1.05, maximum main stresses X1 and accumulated plastic distortions J pl: a) technique 1 and b) technique 2
Fig. 17. Load state t2 Y " 2.05, maximum main stresses X1 and accumulated plastic distortions J pl: a) technique 1 and b) technique 2
grade S355 steel, but which, in analogy to the Hertzian pressure and the associated hydrostatic stress state, need not necessarily be included in a failure assessment. The characteristic distortions not only demonstrate plastic deformation, they also reveal a significant margin to the elongation at break of the steel considered. The FE analyses conducted confirm that it is possible to accomplish the objective of surface hardening through plastic distortion, as pursued by both treatment techniques. The calculated stresses and deformations result in an expected distribution of compressive and tensile stress for the initial load in each case, designated as time/load step 1.00 in the representations. The illustrations show that an internal equilibrium of stresses and forces is generated which is adequate for the deformation state. The results of the other load steps, identified here as time/load steps 2.00 to
3.00, depend on the technique. For a subsequent fatigue analysis, the cumulative stresses in individual steps represent the critical stress and distortion states. By means of additional simulation calculations, and considering results described previously, it was possible to demonstrate the ability to absorb the relatively high stress amplitudes in experiments described previously. This makes it possible to derive findings concerning the key characteristics of the techniques examined from fatigue tests conducted at relatively high stresses and a small number of load cycles, as in the case under consideration. What has yet to be clarified is why large-scale experiments involving treatment of weld seam transitions in some cases revealed a significant, incomprehensible scattering of load cycle counts. It is conjectured that plastic distortion could lead to a degradation of the intended positive effects of treat-
Steel Construction 10 (2017), No. 1
63