DOI: 10.1615/ICHMT.1992.IntForumExpSysCompSimEE
ISBN Print: 978-1-56700-486-1
BOILER COMPONENT FATIGUE LIFE MONITORING USING THE DUHAMEL INTEGRAL METHOD AND RAINFLOW CYCLE COUNTING ALGORITHM
RESUMO
A method of monitoring the thermal stress at the ID of boiler headers and steam drums is described, using a single thermocouple mounted at the ID. The conduction heat transfer differential equation is solved, using the monitored ID temperature as the non-homogenous first boundary condition, and using separation of variables and the Duhamel Integral method in a retrograde form.
The total elastic stress at the inside surface of a hollow cylinder is obtained by adding the mechanical stress caused by the monitored fluid pressure to the calculated thermal stress and is transformed to the inelastic stress-strain history of the tube stub bore hole edge using Neubers Rule and the local strain approach. The patterns of closed stress-strain hysteresis loops are recognized by the Rainflow Cycle counting Algorithm. The fatigue life consumption of individual closed loops is calculated using a modified Coffin-Manson-Basquin-Goodman relationship.