Finite element simulation on mechanical and structural properties of cold-formed dimpled steel

The dimpling process is a novel cold-roll forming process that can enhance the steel material and structural performance by plastically deforming the material surface prior to the section forming operation [1]. Owing to the complex and interrelated nonlinear changes in contact, geometry and material properties that occur in the process and section forming, there have been no existing methods to simulate the process and resultant dimpled products and validate through physical measurements. This paper describes a numerical modelling approach and results into the mechanical properties and structural behaviour of cold-formed dimpled steel. A series of mechanical tests including tensile, plate bending and column compression tests on cold-formed plain and dimpled steel material were conducted for evaluation of numerical results. A finite element approach to practically simulate the dimpling process and experimental tests was presented. True stress–strain data obtained from tests were incorporated into nonlinear simulations of dimpled steel sheets and sections. The simulation of the dimpling process revealed that during the process, various levels of plastic strain are developed throughout the thickness of the steel sheet; this could correlate to the increase in the strength of the dimpled steel as observed in experimental tests and simulations. The simulation of the mechanical tests of dimpled specimens predicted similar results to the experiments, in terms of mechanical properties and structural behaviour. Since the finite element approach was able to successfully represent mechanical properties and structural behaviour of dimpled steel, it can be a powerful method in analysis and design of dimpled steel material and completed sections.