Prediction of buckling force in hourglass-shaped specimens

International Journal of Mechanical and Materials Engineering

Ørjan Fyllingen¹  Vojtech Heinik²  Ragnar Gjengedal³ 

[1] Civil Engineering, Western Norway University of Applied Sciences, 5063, Bergen, Norway;Department of Machine Parts and Mechanisms, Technical University of Ostrava VSB, 70800, Ostrava, Czech Republic;Mechanical Engineering, Western Norway University of Applied Sciences, 5063, Bergen, Norway;

关键词: Compression testing;    Hourglass specimen design;    Finite element modeling;    Critical buckling force;    Hot rolled steel;    Low-cycle fatigue;   

DOI  :  10.1186/s40712-021-00132-8

来源: Springer

【 摘 要 】

It is important to avoid buckling during low-cycle fatigue testing. The buckling load is dependent on the specimen shape, material properties, and the testing machine. In the present investigation of hourglass-shaped specimens the importance of the diameter to radius of curvature is examined. Diameters of 5 and 7 mm are examined with a ratio of radius of curvature to diameter of 4, 6, and 8. The machine used is an Instron 8800 with elongated rods for a climate chamber. This leads to a reduced stiffness of the machine during compression testing. A finite element model (in Abaqus) is developed to identify the critical buckling force. For hourglass-shaped specimens, buckling means onset of sideways movement, without a drop in the applied load which is typical for conventional Euler buckling. The onset of sideways movement is identified experimentally by analysis of the data from extensometer and the load cell. This model is verified by experiments and fits within 0.6 to − 11% depending on the specimen diameter and diameter to radius of curvature ratio. The smallest deviations are obtained for the 7-mm-diameter specimen with deviation varying from 0.6 to − 3.3% between the model and the experiments. The current investigation is done with a commercially available hot rolled structural steel bar of Ø16 mm.

【 授权许可】

CC BY