چكيده به لاتين
Bridges are vital part of the road and railway, one of the most typical damage in steel bride is fatigue crack which causes catastrophic failure and fatigue. Therefore life evaluation of steel bridges are completely necessary. Acoustic emission technique is able to evaluate the crack growth in steel part and deploying on bridge components to monitor the in-service steel bridge. The acoustic emission data can be used in maintenance planning of bridge structure.
In this study, in order to assessment of crack growth and structure behavior, In line with planning of experiments and empirical research, samples of structural steel (St52) were used as compact tension specimen in axial tensile fatigue test in order to study acoustic emission signal characteristic during crack growth. Experiments were done in same load ratio but in three different amplitude and two thickness. By using axial fatigue machine's extensometer Crack mouth opening was measured and crack length was determined. Simultaneous, acoustic emission test was used as non-destructive method and parameter's such accumulative energy, accumulative count, amplitude and hit were studied on different load amplitude and thickness. After primary analyzing, it was found there is a correlation between acoustic emission parameter's and linear fracture elastic mechanic. In order to determination of constant's value least mean square regression analysis were done and then crack length was predicted by using acoustic emission data.
The technology introduced in this thesis can be used to health monitoring of steel structure and condition evaluation of structure's which is subjected to the fatigue load. Unlike initial cost of equipment and setup, utilization of this method have numerous advantageous that could shortly lead to return of investment.
Keywords: crack growth, fatigue load, steel bridge, non-destructive test, acoustic emission.
