Avancerad sökning

Visar resultat 1 - 5 av 128 avhandlingar som matchar ovanstående sökkriterier.

1. 1. A study on contact fatigue mechanisms

   Författare :Bo Alfredsson; KTH; []
   Nyckelord :contact fatigue mechanism; spall; spalling; surface crakc; sub-surface crack; elesto-plastic indentation; contact compliance measurement; TECHNOLOGY; TEKNIKVETENSKAP;

   Sammanfattning : Surfaces subjected to rolling and sliding contacts maysuffer from contact fatigue. This thesisdeals with solidmechanic aspects of contact fatigue including the descriptionand verificationof explaining mechanisms. The new mechanism forsurface initiated contact fatigue is basedon tensile surfacestresses from local asperity contacts. LÄS MER

3. 2. Continuous Welded Railway Rails: Residual Stress Analyses, Fatigue Assessments and Experiments

   Författare :Anders Skyttebol; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; microstructure; laser cladding; plasticity; rolling contact; computational welding mechanics; materials testing; flash butt welding; fatigue; railway rails; fatigue crack propagation; finite element method;

   Sammanfattning : Railway rails are today often continuously welded. This type of joint generally requires less maintenance than is needed for the bolted joints. It has also reduced wheel damage and made the ride more comfortable. However, these joints are subject to damage. LÄS MER

4. 3. On the asperity point load mechanism for rolling contact fatigue

   Författare :Johan Dahlberg; Bo Alfredsson; Sören Sjöström; KTH; []
   Nyckelord :Rolling contact fatigue; Spalling; Asperity contact; Point load; Micro-cracks; Traction; Applied slip; TECHNOLOGY; TEKNIKVETENSKAP;

   Sammanfattning : Rolling contact fatigue is a damage process that may arise in mechanical applications with repeated rolling contacts. Some examples are: gears; cams; bearings; rail/wheel contacts. The resulting damage is often visible with the naked eye as millimeter sized surface craters. LÄS MER

5. 4. Thermal impact on rolling contact fatigue of railway wheels

   Författare :Sara Caprioli; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Railway wheels; Thermomechanical finite element analysis; Frictional rolling contact; Thermal fracture; Tread braking; Rolling contact fatigue;

   Sammanfattning : Rolling contact fatigue (RCF) is a very common and costly damage mechanism for rails and wheels. This thesis investigates the influence of combined thermal and mechanical loading on RCF of railway wheels on the basis of numerical predictions. LÄS MER

7. 5. Rolling Contact Fatigue of Railway Rails with Emphasis on Crack Initiation

   Författare :Jonas Ringsberg; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; variable amplitude; crack closure; rolling contact fatigue; crack propagation; railway rails; damage accumulation; critical plane approach; crack initiation; plasticity; multiaxial fatigue;

   Sammanfattning : Increased traffic density and the heavier axle loads of modern trains have led to severe problems with rolling contact fatigue (RCF) which cause initiation of surface cracks in railheads. In this thesis, a specific type of surface crack, the head check, is studied numerically with emphasis on fatigue crack initiation. LÄS MER