Fatigue Crack Repair Mechanism and Effect by Pneumatic Impact Treatment
To explore the repair mechanism and effect of pneumatic impact treatment on fatigue cracks of the steel bridge deck,the plastic deformation of the target material during the pneumatic impact treatment was studied based on kinetic theory,and the behaviors of crack surface closure under such plastic deformation were analyzed.Then,the local stress field in the closure part was investigated,and the stress response and its deformation under the applied load were discussed by numerical method.Fatigue tests were carried out to verify the repair effect of pneumatic impact treatment at last.The results show that the mathematical model proposed here is able to predict the impact depth.Large plastic deformation is observed on the material surface during the pneumatic impact treatment process,and the impact depth and transverse deformation are similar.When the relative transverse deformation of the crack fracture surface becomes larger than the crack width,the contact closure and compressional deformation can be found,which will introduce the contact stress at the closure part.This contact stress can resist the tension effect of the crack surface under applied load,reduce the stress intensity factor at the crack tip,and restrain the propagation of fatigue cracks,which is also proved by the tests.
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