engleski

Damage Initiation and Evolution in Nodular Cast Iron for Wind Turbine Components

During the service life wind turbine components are subjected to complex cyclic loading and fatigue fracture. Herein, the nodular cast iron grade EN-GJS-400-18-LT, in which graphite spheroids or nodules in a ferritic matrix provide large ductility and fatigue strength, is widely used [1]. There are only limited experimental data available on fatigue crack growth behaviour of this cast iron and still the effect of the graphite morphology as well as microstructure phase on fracture toughness and fatigue properties of this material is not well documented. This paper presents an experimental and numerical study of the cyclic deformation and damage accumulation in the nodular cast iron grade EN-GJS-400-18-LT. The experimental procedure includes strain controlled tests on the cylindrical specimens as well as crack initiation and propagation tests on the compact tension and single edged notched specimens [2]. Different loading regimes are applied, and monitoring of the crack length during the tests is performed by an optical system ARAMIS 4M and infrared thermography. Within the framework of numerical investigations a cyclic plasticity model in combination with the ABAQUS/Standard [3] damage initiation and evolution criteria is applied to study the low-cycle fatigue damage near the notch and the crack tip using the direct cyclic approach to obtain the stabilized cyclic response of the structure directly. Herein, the damage initiation and evolution criteria are based on the stabilized accumulated inelastic hysteresis strain energy per cycle. Finally, the computational procedure accuracy is verified by comparing the computed results with the real experimental data. It is shown that the numerical results agree well with the experimental results.

experiment; digital image correlation (DIC); nodular cast iron; thermography; finite element method; thermoplasticity

nije evidentirano