Research On Reliability Of Vehicle Chassis Welded Components Of CRH2

In recent years high speed train developed very fast in China, its testing and acualoperating speed improved continuously. However, researchs on reliability of high speedtrain was poor. The vehicle chassis welded structure of high speed train is a keycomponent of carrying. Cracks and other defects were detected after the train runningfor a period of time. Instead, repair welding of crack would reduce the serviceperformance of the structure.The welding residual stress and dynamic stress distribution of the vehicle chassiswas analysed by numerical simulation. Four carrying dangerous areas of vehicle chassiswere determined by FEM. The fracture toughness of A7N01P-T5aluminum alloy wasfirst tested and further analysis on its thichness effect was carried out. The analyticalformula of the relationship between the fracture toughness and material thickness ofA7N01P-T5aluminum alloy was derived afterwards, providing firmly support for thereliability of high speed train vehicle chassis.In this thesis, the security on CHR2vehicle chassis welded structure was assessedwith SINTAP/FINET(Structural Integrity Assessment Procedure/Fitness for serviceNetwork) by FEM, and the residual fatigue life of dangerous areas were assessed byfracture mechanics theory Finally, the security and reliability of vehicle chassis werepredicted,and the defects tolerance was presented by principle of fitness for service.SINTAP/FITNET was applied to safety assessment of the carrying dangerous areas.Under the assumption of a semi-elliptical surface crack in each dangerous area, itrevealed that its crach depth a rather than the initial crack size a/c which affected theassessment result. Assumed a/c=0.2, the assessment results of dangerous area1,2and3was obtained. The critical crack size was about5mm~5.5mm. The critical unilateralpenetrating crack of dangerous4was40mm. The components with above cracktolerance met the principle of “fitness for service”.The residual fatigue life of dangerous area was assessed by fracture mechanicstheory. In the condition that initial crack size a0=0.5mm, a/c=0.2, the residual fatiguelife of both dangerous area1and dangerous area2was higher than the Condition FatigueStrength at2x10~6cycles. However, it was lower in dangerous area3. so more attentionmust be paid on this poison. The residual fatigue life of dangerous area4with single-edge crack was on two order of magnitude lower than the other areas, itdemonstrated that single-edge crack was more dangerous than surface crack. The resulton assessment of residual fatigue life provided theoretical basis for fatigue reliabilityprediction and structural optimization design and manufacture on vehicle chassis.