DEVELOPMENT OF A FATIGUE MONITORING SYSTEM FOR A HYDRAULIC EXCAVATOR

Abstract eng:
One of the largest barge mounted hydraulic excavators in the world experienced substantial fatigue cracking during normal operation. Fatigue cracking in a similar, smaller, excavator went undetected long enough for cracks to grow to a critical length resulting in boom fracture. Because of previous cracking problems in the larger excavator, and because of expected difficult future dredging projects, the owner of the excavators sought advice to mitigate the risks associated with the fatigue problem. To better understand the stresses in the boom of the excavator, a visual examination was performed, strain gages were installed at critical locations and strains were measured during static tests and normal dredge operations. The results were used to develop a structural maintenance program, which included a permanent computer monitoring system. The computer system continuously monitored the boom strains and calculated the accumulated fatigue damage at each gage location using an approximation of the reservoir method. The system allowed engineers to determine when to schedule critical inspections. The computer system also had an alarm to warn the operator when high stresses occurred during the dredge operation. This paper presents the results of the static and dynamic testing, and the strain monitoring system.

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