LOW STRESS MACROSCOPIC PLAS-TICBEHAVIOR

OF COATED PART UNDER REPEATED

IMPACT CONTACT LOAD

Shi Shihong   Fu Geyan

(College of Mechanical Electrical Engineering，Suzhou University, Suzhou 215021)

Ouyang Basheng  Peng Rushu

(College of Mechanical Engineering, Nanhua University, Hengyang 421001)

Abstract: Low stress repeated impact experiments and tests are done on medium carbon steel specimens and stainless steel specimens who are coated with high strength Co or Ni alloy. The results show that plastic deformation happen in the coat material and a part of substrate material near the coat. The mean plastic deformation of every impact, along with the increment of impact frequency, is getting large at first and than turn small. And under accumulating, there is macroscopic plastic deformation along with the material hardening phenomenon. The value of total deformation and the size of deformation area are related to stress value of impact and materials strength. The degree of deformation hardening is attenuating from surface to inner, and this phenomenon only occurs at the surface of impact contact and the next following length, forming an “easy deformation area”. The analysis considers that repeated impact deformation is a kind of cumulative fatigue damage. When the peak stress is same, the absorbed energy of material under the repeated impact contact load is more than under the static fatigue load. And absorbability is in inverse proportion with the distance from the impact point. Repeated impact can intensify the mobility of atom, reduce critical shear stress, and make the enablement and multiplication of dislocation easy.

Key words: Repeated impact load  Low stress  Coated part  Plastic behavior

CLC No: TG113  TB302

国家自然科学基金(50271028)和湖南省自然科学基金(02JJY2072)资助项目. Received 20040626, received in revised form 20041125