Fatigue strength of blunt V-notched specimens produced by selective laser melting of Ti-6Al-4V

Additive manufacturing (AM) offers the potential to economically produce customized components with complex geometries in a shorter design-to-manufacture cycle. However, the basic understanding of the fatigue behavior of these materials must be substantially improved at all scale levels before the unique features of this rapidly developing technology can be used in critical load bearing applications. This work aims to assess the fatigue strength of Ti–6Al–4V smooth and circular notched samples produced by selective laser melting (SLM). Scanning Electron Microscopy (SEM) was used to investigate the fracture surface of the broken samples in order to identify crack initiation points and fracture mechanisms. Despite the observed fatigue strength reduction induced by circular notched specimens compared to smooth specimens, notched samples showed a very low notch sensitivity attributed both to hexagonal crystal lattice characteristics of tempered alpha prime grains and to surface defects induced by the SLM process itself.

Fatigue Assessment of Ti–6Al–4V Circular Notched Specimens Produced by Selective Laser Melting

Determination of the fatigue P-S-N curves – A critical review and improved backward statistical inference method

Tensile failure prediction of U-notched plates under moderate-scale and large-scale yielding regimes

An applied method for fatigue life assessment of engineering components using rigid-insert crack closure model

Retardation of fatigue crack growth in high strength steel S690 using a modified stop-hole technique

Drilling holes in the vicinity of the crack tip turns the crack into a notch and reduces the crack tip stress intensity factor. In this paper, a new idea is used in which instead of a single hole, two symmetric and interconnected holes are drilled at the crack tip. The main concept of double stop-hole method is to reduce the stress concentration at the edge of stop-holes in the cracked structural elements. The double stop drill hole method can be used to increase the fatigue life of the cracked components. The fatigue crack growth retardation is examined using an experimental investigation coupled with a stress analysis on the efficiency of proposed double stop-holes. The distance between the hole centers is considered as the main parameter affecting the efficiency of this method. The results show that the fatigue life extension caused by the double stop-hole method is significantly more than the conventional single stop-hole method.

Fatigue Life Extension by Crack Repair Using Double Stop-Hole Technique

Fatigue crack growth in full-scale railway axles – Influence of secondary stresses and load sequence effects

The invention relates to a test bench for wheelset shafts, having the following features: the wheelset shafts to be tested have two mounted wheel disks; the bending torque is introduced via the two wheel disks; the wheelset shafts to be tested are mounted on the retaining consoles in the expected region of the vibration nodes by means of rubber bearings; and the main natural frequencies of the retaining consoles lie above the testing frequency. By using the test bench according to the invention, the testing time and testing costs can be significantly reduced. The necessary measuring equipment can be easily mounted on the shaft. Thus, standard measuring equipment can be used.

Christian Moser

Papers

Retardation of fatigue crack growth in high strength steel S690 using a modified stop-hole technique

Fatigue Life Extension by Crack Repair Using Double Stop-Hole Technique

Fatigue crack growth in full-scale railway axles – Influence of secondary stresses and load sequence effects

Test bench for wheelset shafts