Comparative study on the characteristics of magnetic memory signals for welding and non-welding steels with different materials under tension-compression fatigue

Article type: Research Article

Authors: Yang, Yiyi^a | Su, Sanqing^a; | Wang, Wei^a | Ma, Xiaoping^a | Hu, Jingyu^a

Affiliations: [a] School of Civil Engineering, Xi’an University of Architecture & Technology Shaanxi, Xi’an, China

Correspondence: [*] Corresponding author: Sanqing Su, School of Civil Engineering, Xi’an University of Architecture & Technology Shaanxi, Xi’an 710055, China. E-mail: [email protected]

Abstract: Metal magnetic memory (MMM) testing method has been proved to be a valid approach to monitor early damage and predict fatigue life, but there is no systematic description and comparison about the characteristics of MMM signals for welding and non-welding specimens with different materials under tension-compression fatigue. Thus, the fatigue tests for Q345B and Q345qC welding and non-welding specimens were carried out and the MMM testing was done synchronously. Then, based on the normal components of MMM signals, Hp(y), and its variations, ΔHp(y), the slope of ΔHp(y) fitting curves, KC, and the average of ΔHp(y) signals on the whole testing line, ΔHp(y)ave, were extracted as the characteristic parameters for Q345B and Q345qC non-welding specimens, respectively. Additionally, the gradient of “peak–vale” on Hp(y) signals curves, k, and the average of Hp(y) signals in the scope of welding zone, Hp(y)ave, were extracted as the characteristic parameters for Q345B and Q345qC welding specimens, respectively. Some conclusions can be drawn by comparison: the variation laws of Hp(y) signals with cyclic loads are related to the material. The characteristic parameters for welding and non-welding specimens with the same material have a certain similarity. Then, the failure of non-welding steel can be warned early by KC or ΔHp(y)ave when the fatigue life has 20% left, but the damage degree of welding specimen should begin to be valued highly once the k or Hp(y)ave is decreasing. Finally, the fatigue life of welding and non-welding specimens with different materials can be evaluated effectively by using corresponding magnetic characteristic parameters.

Keywords: Metal magnetic memory (MMM) testing, fatigue life, magnetic characteristic parameter, Q345B and Q345qC steel, weldments

DOI: 10.3233/JAE-190064

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 62, no. 3, pp. 619-643, 2020