Abstract
To establish an online nondestructive stress testing method for arch bridge suspender based on the principle of magnetic coupling, the magnetic mechanical property of Q345qD steel is explored taking an arch bridge model structure with Q345qD steel suspender as the research object. Under the action of magnetic field excited by a coil, the test of the coupling relationship between stress and excitation flux is carried out. The theoretical model of stress‐magnetic flux is simplified to better meet the requirements of engineering applications. The excitation device, magnetic flux measurement device, stress‐magnetic flux data analysis program, and so on are developed, and the magnetic coupling stress detection system is integrated. The test model structure of a steel arch bridge with suspenders of Q345qD alloy steel is designed and made; under the different load conditions, the stresses of the suspenders are tested and studied. The relationships between induced magnetic flux and technical magnetized voltage, test load of model structure, and different stress conditions of the suspenders are analyzed; with the induction magnetic flux as the parameter, the stress‐magnetic flux coupling model is established. The test results based on the stress‐magnetic flux coupling model are compared with those of the traditional stress‐strain test in a linear elastic range; it shows that the two testing methods are in good agreement with each other, and the maximum error is less than 5%. Meanwhile, with the increase in the load on the suspender, the tension stress increases and the induced magnetic flux decreases, showing a good linear relationship. The conclusions drawn from the research can provide important reference for health monitoring of suspenders of arch bridges.
Highlights
To establish an online nondestructive stress testing method for arch bridge suspender based on the principle of magnetic coupling, the magnetic mechanical property of Q345qD steel is explored taking an arch bridge model structure with Q345qD steel suspender as the research object
Operation, and maintenance, suspender is affected by the changes in load, material properties, and environment. e actual stress state during the service period is inconsistent with the design, even reaching or exceeding the design limitation, resulting in major engineering safety incidents in the application of steel bridge structures. e traditional testing techniques and methods are mainly based on the stressstrain constitutive model
Stress detection theory based on the magnetic coupling effect is a new type of magnetic nondestructive testing method developed in recent years [1,2,3,4,5,6,7,8,9,10,11,12]. e basic principle is based on the magnetic coupling theory of ferromagnetic materials [13,14,15]
Summary
When testing the stress of the structural member made of bridge structural steel, the parameters of formula (1) involve the microscopic mechanism of ferromagnetic materials, which is difficult to determine in practical engineering applications For this reason, the test of stress-induced magnetic flux coupling relationship for the Q345qD bridge structural steel specimen is done, and a practical model of stress detection based on magnetic coupling theory is obtained. When σ ≤ 300 MPa, the stress-induced magnetic flux model of Q345qD bridge structural steel can be simplified by the curve in Figure 2 and fitting formula (2), which can better meet the needs of stress testing
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