International Journal of Mechanical Engineering and Applications 2017; 5(5): 275-281 http://www.sciencepublishinggroup.com/j/ijmea doi: 10.11648/j.ijmea.20170505.16 ISSN: 2330-023X (Print); ISSN: 2330-0248 (Online) Computation of Micro-Strains in Cold Formed Steels- FEA Approach Assad Anis Department of Automotive & Marine Engineering, NED University of Engineering & Technology, Karachi, Pakistan Email address: soi_assad@hotmail.com To cite this article: Assad Anis. Computation of Micro-Strains in Cold Formed Steels- FEA Approach. International Journal of Mechanical Engineering and Applications. Vol. 5, No. 5, 2017, pp. 275-281. doi: 10.11648/j.ijmea.20170505.16 Received: December 24, 2016; Accepted: January 6, 2017; Published: October 30, 2017 Abstract: This paper describes the computations of micro-strains at inner corner of cold formed rectangular hollow sections (CFRHS) made up of structural steels using finite element analysis. In order to obtain the micro-strains, distortion test is simulated by modeling two-dimensional structural steel tubes in ANSYS software. Two dimensional linear static analyses are performed by defining elastic properties of steel. These simulations were performed for tubes with outer radius to thickness (r o /t) ratios of 3. In real distortion tests, the direction of force at outer corner of the tube may vary in terms of angle. Therefore, this fact is taken into account while performing simulations. One more aspect is taken into consideration which is related to strain gauge placement during distortion testing. This problem is analyzed by modeling three-dimensional structural tubes and performing linear static analyses to investigate the variations in strains at inner bent section of the tube with different strain gauge locations. Keywords: CFRHS, Finite Element Analysis (FEA), R o /T Ratio, Distortion Testing 1. Introduction A high-strength cold-formed rectangular hollow section structural beam (CFRHS) subjected to cyclic bending loading was found to fail due to fatigue [1]. These members are often used in marine and off-shore applications. Distortions tests (fig. 1) are performed to obtain the fatigue strength of cold formed high strength structural tubes. It is essential to compute the micro-strains at inner corner of the tubes if a strain based fatigue approach is used. The main factors which affect the fatigue strength of cold formed members are residual stresses, stress concentration factors, corners geometry and surface roughness. Many researchers have adopted different techniques to investigate these factors. Sami and Bjork [2] investigated the fatigue crack paths in cold formed corners using FEA approach. The author of this paper has also investigated residual stresses and stress concentration factors in CFRHS [3, 4, 5]. Marquis and Bjork investigated fatigue crack paths in corners of cold formed high strength steels [6]. Mohamed Dabaon [7] investigated built up cold formed sections battened column. Strains were measured in this work to observe failure mode and deformed shapes. Nanocrystalline Ni and Ni-Fe alloys produced by electrode position were characterized by Jason D. Giallonardo [8] using high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The microstrains in the sample were determined from XRD pattern analysis based on line broadening. X L Xu [9] studied microstrain in rapidly solidified structures of hypercooled Co 80 pd 20 alloys. In the undercooling range studied, the microstrain in the rapidly solidified structures increases with increasing undercooling. Quenching immediately after rapid solidification is helpful to preserving the microstrain in the microstructures. Cheng Yu and Benjamin W. Schafer investigated failure modes by performing distortion buckling test in cold formed members [10]. These distortional buckling tests also provide a direct comparison against the local buckling tests previously performed by the writers. Sammy C. W, Lau and Gregory also performed distortional buckling tests of cold formed channel sections [11]. The results of compression tests of thin-walled channel section columns formed by brake-pressing are described. A total of 68 channel section columns of different section geometries, thicknesses and steel grades were tested under uniform