PENGARUH VARIASI PENAMBAHAN NIKEL ( Ni ) TERHADAP KEKUATAN LELAH ( FATIGUE STRENGTH ) BESI COR KELABU DENGAN MENGGUNAKAN UJI FATIGUE PADA TEMPERATUR KAMAR

Abstract

Fatigue failure is extremely dangerous because it occurred without initial guidance. In part or machine components are often found because repetitive or fluctuating stress. The presence of graphite in gray cast iron causes this material does not have a linear elastic region. Graphite also causing present of an experienced plastic section although cast iron is loaded by a low force. This is caused at the ends of the graphite occurs enormous stress as a result of stress concentration. Every time there tension crack will propagate so sectional finally cannot able to rest accept the work force and will be broken. Damage due to fatigue may occur because crack propagation/ defect slowly/ gradually. This study object to improve the mechanical properties of gray cast iron, especially the fatigue strength. This research was conducted consisted of three materials i.e. Base Materials, Mixture 1, Mixture 2. Each material was examined to determine the chemical was composition of existing elements, Rockwell hardness test method, which is converted into Brinell, tensile testing, while the fatigue testing using fatigue rotating bending testing machine, and testing to determine the micro structure micrographic. The results showed that an increase in the mechanical properties of gray cast iron after the addition of 0.17% nickel and 0.22% of hardness value, tensile strength. Baesd on experiment results of micro structure there are no the difference significanly among that three material. For the fatigue strength increased by 24% from 135 MPa to 169 MPa. Addition of 0.17% nickel element will enhance the mechanical properties of gray cast iron because nickel has a high hardening properties without cracking occurred and this contributed to the fatigue strength.