Fatigue Life And Reliability Research Of Crane Lattice Boom

Lattice boom cranes are widely used in various fields of national economy as lifting equipment. How to predict life and reliability of the boom effectively is a difficult area of research and focus. Fatigue Life research of lattice boom cranes in domestic is in relatively backward reflected in:the lack of fatigue life S-N curves under specialized crane typical conditions, low accuracy of the use of linear cumulative damage theory of fatigue life calculation. Because of other non-linear cumulative damage theories of complex formulas, engineering applicability is not populaer. The main research works are as follows:(1) Based using the curve similarity theory of hyperbolic sine function and fracture mechanics crack growth curve, a new simplified non-linear cumulative fatigue damage theory is built with the constant amplitude strain-life formula Basquin-Manson-Coffin (BMC). The concept of cumulative damage scale factor is described. Normalized constraint relations between the unit of crack growth rate and fatigue life is established. For the case of stress distribution on booms are in a fuzzy band, a improved non-linear cumulative damage model based on fuzzy damage and probability model is proposed. Comparison of the various factors that affect the fatigue life of lattice boom is expressed and a basic trend of the sensitivity of each parameter is described.(2) Actual stress spectrum is difficult to get under various working donditions for cranes. To obtain real crane stress spectra inexpensively and conveniently, a new stress spectra acquisition method based on the’measured&simulated&compared&statistics’integrated strategy is proposed based on virtual prototype technology.Through the establishment of global and local hazardous areas crane refinement coupled finite element model of virtual prototype, stress spectra can be abtained by dynamic simulation. It is a new way to get the stress spectra of cranes.(3) Seven system single-factors and evaluation indicators which will affect the reliability of the lattice boom crane are analyzed. Overall reliability of the boom system evaluation system framework is buit based on the multi Analytic Hierarchy Process conbined with dynamic weight built method. Through the process of assessing fatigue reliability analysis, security decisions are proposed. For the convenience of engineering applications, a self study evaluation model is buit based on Elman neural network which can calculate automaticly after a train of large number of expert training data. (4) Specially designed tooling is built for fatigue tests for lattice boom key nodes based on the hot spot method. A new S-N curve is obtained by fitting experimental under crane’s typical operating conditions which will fit for lattice boom crane fatigue life assessment. Three main factors which will have impact on fatigue life are compared in the test and the impact trend curve is derived. Material parameters of probability BMC formula are obtained by data fitting method.The fatigue test can provide design data for crane’s fatigue design.(5) A crane booms fatigue life assessment system is developed which can do crane load records, life expectancy calculations, security decisions and other functions. Through a case study, life calculation and safe reliability of crane lattice boom is described to verify the theoretical algorithm proposed by this project.