Research on the sensitivity of material parameters to cross-sectional deformation of thin-walled rectangular tube in rot
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e fluctuation of material parameters and coupling effects of them have significant effects on cross-sectional deformation of rectangular tube in rotary draw bending process. So, in this research, a global sensitivity analysis (GSA) system was established based on the combination of Morris’ GSA method and 3-D finite element method, and the reliability of the system is validated. Based on the system built, the sensitivity values of different material parameters combinations were analyzed. The results show that (i) the maximum cross-sectional deformation ratio decreases with the increase of Young’s module E and strain hardening exponent n, while the effects of strength coefficient K, initial yield stress rS, and thickness anisotropy exponent c on cross-sectional deformation are opposite to those of E and n, (ii) the groups which contain E and c simultaneously show greater sensitivity and the effect of group only including E and c on cross-sectional deformation is the most remarkable, while the most insensitive group in different combinations contains K, and (iii) mostly, the sensitivity values of coupling groups to cross-sectional deformation are larger than those of one-parameter groups.
I. INTRODUCTION
As important connecting pieces, thin-walled rectangular bent tubes have been widely applied in fields of aerospace, aviation, and automotive for its lower cutoff frequency and smaller loss signal.1 Rotary draw bending (RDB) is a versatile and cost-effective method in tube bending area in response to the diverse demands of bent tube specification, shapes, and forming tolerance. However, RDB of thin-walled tube is a complicated physical process with multifactor interactive effects and complex nonlinear contact conditions.2 Cross-sectional deformation of rectangular tube in RDB process inevitably occurs and it seriously affects the forming accuracy. Material parameters, such as Young’s module E, initial yield stress rS, strength coefficient K, strain hardening exponent n, and thickness anisotropy exponent c, have a significant impact on cross-sectional deformation. And material parameters easily fluctuate in a certain range with the change of heat treatment methods, batches, and manufacturing processes of thin-walled rectangular tubes. What’s more, there also exists coupling effects among material parameters. Therefore, it’s vital to study the sensitivity of material parameters and coupling effects of material
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.194
parameters to cross-sectional deformation for improving the forming quality of rectangular tube in RDB process. In recent years, aiming at improving the cross-sectional deformation of tubes in bending process, numerous scholars have researched the impact of material properties on cross-sectional deformation of bent tube by utilizing experimental method, theory analysis method, and numerical simulation method. Yang et al.3 researched the effect of initial yield strength rS on cross-sectional de
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