Railway wheels are usually attached to axles by press-fitting; therefore, the mechanical processes taking place during operation can result in failure, with fatal consequences for axle seats. This manuscript describes effect of laser hardening on residual stress state, microstructural parameters (lattice defects—dislocations, crystallites, microstrains, etc.), and properties laser-hardened EA1N steel railway under fatigue life conditions. Differences were found between ground, single-track,...

Abstract The paper contains results of an investigation effect shot peening on initiation and growth physically short fatigue cracks in aircraft V-95 Al-alloy, which is a similar type as 7075 alloy. first part deals with adaptation verification direct current potential drop (DCPD) method for detection measurement crack flat specimens specific shape dimensions. possibilities the terms sensitivity resolution well limits are discussed. material properties quite large dimensions side necking low...

In connection with increasing needs of different branches industry for steels excellent mechanical properties, like high strength combined ductility on one hand and low or at least moderate costs the other hand, an experimental alloy 42SiCr steel has been developed. If a conventional heat treatment is applied to this material, very can be reached, however unacceptable ductility. Well balanced i.e. about 2000 MPa more than 10 – 15%, achieved by application advanced methods Q-P (quenching...

Two segments of transition oil pipeline DN500 and DN700, operating since 1980, were subjected to full-scale pressure testing. In 2000, corrosion defects found on both pipelines - the two outside wall pipeline, one defect inside DN700 pipeline. Both pipes sleeve reinforced increase safety reliability lines. The used Cold Lock steel with a composite filling. On other hand, Clock Spring sleeve. 2020, after decades operation repairs, dug out, removed from for testing determine residual strength...

An investigation of nitriding effect on fatigue behavior small-size specimens a 30CrMoV9 (ČSN 15330) steel heat treated to high strength was carried out, and damage mechanisms were evaluated. Circular cross-section either smooth or notched, with the diameter approximately 2 mm in gauge section used. Axial tests out at constant load amplitude, loading repeated type—load asymmetry R = 0. The program as separate part complex evaluation resistance gears against failure. process resulted...

The paper contains results of a study aimed at an experimental evaluation fatigue resistance and initiation mechanisms heat treated laser hardened 42CrMo4 steel. Experiments were performed using quite small specimens 8 x mm cross section, under three point bend loading. Two different parameters hardening used, one them resulted in considerable longitudinal residual stresses – surface speed beam 4 mm/s. Results tests basic reference material, just treated, characteristic by surprisingly high...

Abstract The aim of this work was experimental study the dents effect on structural integrity a high-pressure gas pipeline with nominal diameter 300 mm after long-terme operation. Stress-strain behaviour two evaluated by strain gauge chains oriented in hoop direction. Dent profiles were measured digital slide caliper circumferential and longitudinal direction points distant 10 from each other. Residual deformations detected internal pressure loading water to operating level. Negative...

Pipeline transport uses millions of kilometers pipes worldwide to liquid or gas over long distances the point consumption. High demands are placed, especially on hazardous substances under high pressure (gas, oil, etc.). Mostly seamless steel various diameters used, but their production is expensive. The use laser-welded could significantly reduce cost building new pipelines. However, sufficient mechanical properties need be ensured for welded meet stringent requirements. Therefore, 10 mm...

Fatigue crack growth (FCG) rates in an EA4T railway axle steel heat treated by two different methods near threshold and stable regions of were evaluated. Quite significant differences observed, when the obtained results compared with those published literature. Participation laboratory Exova (GE Aviation) FCG measurement qualification round robin programme very good practically excluded errors experimental methodology used. Strength evaluated series material was equivalent. Nevertheless,...

Laser surface hardening is an advanced method of treatment structural steels with a great potential for wide industrial applications. The technology quite new and so, investigations have to be performed in order gain comprehensive knowledge about effects on microstructure, hardness, properties treated materials, but also mechanical particularly fatigue properties. Concerning resistance material this technology, results recently published the literature indicate that can either reduced or...

During recent internal inspection of an operated high pressure pipeline the diameter DN700, distinct, quite large indications cracks were found in one pipe sections. A part section was taken from ground for a comprehensive experimental programme containing analyses defect type, dimensions and character also fatigue test at variable with maximum value corresponding to real operation. The analysed defects mostly occurred during manufacture followed by stress corrosion cracking mechanism some...

Inclusions significantly affect fatigue properties of quenched and tempered parts. Data about inclusions importance in crack initiation process were acquired within the framework a systematical test programme carried out to verify CrNiMo(V) steels 800 1000 MPa strength. A valuable set failures from high lifetime area was acquired.Microfractographical analysis these enabled evaluate critically influence inclusions, their dimensions, character morphology on propagation cracks Comparison size...

The paper contains results of a study aimed at exploring possibilities use direct current potential drop (DCPD) method for evaluation depth and profile cracks occurred under or near press fitted hubs in full-scale axle during severe rotating bending loading. DCPD was applied on section an after fatigue by specific way potentials were measured several circumferential areas the section, when passed longitudinally. Results are analysed discussed. It indicated that unlike previous crack...

Different experimental methods are being used in laboratories for automatic measurement of fatigue crack growth rates and threshold values. Such data belong to mechanical properties essential an assessment residual life components structures containing cracks length more than several millimetres. However, if the material contains small crack-like defects like inclusions or pores, knowledge about local resistance against physically short becomes very important. Damage mechanisms even...

The paper deals with an investigation of surface laser hardening characteristics on contact and bending fatigue resistance a 42CrMo4 steel, being often used for manufacture gear wheels. aim the experimental programme was to simulate complex service loading fairly large gears by two separate investigations, namely performed special, so called analogon machine high cycle resonance machines using three-point-bend (3PB) specimens. It shown that after optimising methodology parameters technology,...