Stress In Steel Structures Research Articles

Using Iterative Correction to Improve the Accuracy of the Blind-Hole Welding Residual Stress Test.

An iterative correction method for the stress release coefficient, leveraging numerical simulation, has been innovatively developed to address the significant error issues associated with the blind-hole method in high-stress residual stress testing of steel structures. This method effectively reduces measurement error in high residual stress regions through a discriminant iteration process. The finite element analysis technology was employed to accurately simulate the blind-hole method's test process, and additionally, Python was utilized for customizing the secondary development of ABAQUS software, thereby automating and optimizing the method. When compared with simulation and experimental data from the welding process, the efficiency, accuracy, and reliability of the correction method have been verified. The proposed method eliminates the need for tedious calibration experiments inherent in traditional methods, significantly enhancing the test's automation level and convergence speed, and ensuring measurement accuracy, which provides an innovative solution for the accurate evaluation of residual stress in steel structures.

Research on the Method of Absolute Stress Measurement for Steel Structures via Laser Ultrasonic

Accurate measurement of the stress in steel structures is crucial for structural health monitoring. To achieve this goal, a novel technique, the laser ultrasonic technique, was used in absolute stress measurement in this study. The feasibility of this technique has been verified through theoretical analysis and finite element (FE) analysis. A stress measurement experiment in steel specimens was conducted and the relationship between ultrasonic relative wave velocity and stress was explored. The results revealed that there is a similar linear correlation between the ultrasonic relative wave velocity and absolute stress. The stress can be obtained based on ultrasonic relative wave velocity. According to the stress measurement results, it was found that the absolute error between the measured stress and theoretical stress was largest when the stress level was low, and that the measured error of stress gradually decreased with increases in the applied stress. The relative error between the measured stress and the theoretical stress was within 10% when the stress was higher than 100 MPa. This further verifies the reliability of the laser ultrasonic technique under high-stress conditions. Additionally, the impact of temperature and surface roughness on stress measurement was analyzed. The stress error in stress measurement increased similarly linearly with the increase in temperature and increased non-linearly with the increase in roughness. The corresponding compensation methods were proposed to effectively improve the accuracy of measurement.

Study of magnetoelastic demagnetization of locally magnetized steel

To improve the accuracy of determining mechanical stresses in steel by the method of magnetoelastic demagnetization (magnetoelastic memory), the magnetoelastic sensitivity of the material to elastic stresses is additionally measured by applying or removing an additional load of a known value. We present the results of studying the magnetoelastic demagnetization of locally magnetized steel by varying stresses of the uniaxial tension or compression against a background of the base load. The magnetoelastic sensitivity of the steel in a loaded state to variable stresses has been assessed. It is shown that the determination of the magnetoelastic sensitivity of the steel to variable loads makes it possible to improve the accuracy of estimating base stresses in the steel structure using magnetoelastic methods. It is revealed that a decrease in the strength of the magnetic scattering field of the local residual magnetization (LRM) of the steel after variable loading (or unloading) exponentially depends on the magnitude of the base stresses. The possibility of controlling the uniaxial mechanical stresses in steel structures in the magnetoelastic memory mode which is based on the dependence of the strength of magnetic scattering field of the local residual magnetization of the steel on the uniaxial stresses is shown. A method for monitoring uniaxial stresses in the elements of steel structures by the method of magnetoelastic memory is proposed using the measured magnetoelastic sensitivity of the material. The results obtained can be used in the development of a method for monitoring the stress-strain state of steel structures during operation under the simultaneous effect of static and dynamic loads.

Test on post-fire residual mechanical properties of high strength Q690 steel considering tensile stress in fire

As a steel building may not fail in a fire scenario, the residual mechanical properties of steel after fire exposure are essential in evaluating the post-fire performance of the steel structure. However, the current experimental research regarding the post-fire mechanical properties neglects the stress in steel during the heating and cooling phases, which violates the fact that a steel structure still carries load during a fire hazard. In order to quantitatively assess the influence of stress level in steel structures on post-fire residual mechanical properties of high strength steels, a series of tensile tests was carried out on a typical high strength Q690 steel specimen exposed to elevated temperatures under three stress ratios, namely 0.30, 0.55 and 0.80. During the heating and cooling phases, constant stress was applied on the specimen to simulate the possible stress in steel structures in fire hazards. After cooling, tensile tests were carried out to attain the post-fire stress-strain curves of Q690 steel, and accordingly determine the residual yield strength, ultimate strength and elastic modulus of Q690 steel with different temperature exposures and stress levels. The test results show that the tension stress in steel during heating and cooling can improve the post-fire yield strength and ultimate strength of Q690 steel with the maximum 8% when the exposed temperature is lower than 700 °C, and the improvement increases as the stress level increases. However, the tension stress has adverse effect on the post-fire strengths of Q690 steel when the exposed temperature reaches 800 °C. If the exposed temperature is below 700 °C, it is safe to take the original strengths of Q690 steel to evaluate the post-fire performance of Q690 steel structures. However, the stress effect on the residual strengths should be considered if the exposed temperature reaches 800 °C to avoid unconservative evaluation. The tension stress in steel has no significant influence on residual elastic modulus of Q690 steel. By comparing the obtained test data with other post-fire tests on similar steels, it is found that the post-fire residual mechanical properties of steels are different even if those steels have the same nominal yield strength. The maximum 40% dispersion for residual yield strength and 50% dispersion for ultimate strength are found when the exposed temperature surpasses 600 °C due to rolling, quenching and tempering for high strength steels.

Determination of the steel axial stresses in memory mode by the exponential law of magnetoelastic demagnetization

Magnetic and magnetoelastic methods of stress control are based on changes in the magnetic parameters of steel upon deformation. However, the magnetic properties of different steel grades, and even of the same grade in different heats may differ noticeably. The inhomogeneity of the magnetic and magnetoelastic properties of steel attributed to variations in the chemical composition, as well as in the modes of rolling and heating during manufacture affects the accuracy of stress control being a common disadvantage of magnetoelastic methods used for monitoring the stress-strain state of steel structures. The goal of the study is to consider the possibility of monitoring uniaxial mechanical stresses in steel structures in the «magnetoelastic memory» mode, based on H(σ) dependence of the strength of magnetic field of scattering local remanent magnetization of steel on the uniaxial stresses. The exponential function is shown to provide a satisfactory description of the experimental dependence of the strength of the magnetic field of scattering of the permanently magnetized 17G1S and 15KhSND steels on the stresses induced in steels by tension, compression, and impact. To improve the accuracy of the control, we propose to introduce the magnetoelastic sensitivity of steel (MSS) into the accepted form of the exponential dependence H(σ). A way to MSS determination not only on laboratory samples under ideal conditions, but directly on the construction under control (which reduces the errors of the control attributed to variations in the magnetic and magnetoelastic properties of steels) is considered. To implement the proposed procedure, prototypes of the devices for static and dynamic local loading of metal structure elements have been developed and manufactured. The devices have undergone a pilot test when monitoring the stress-strain state of the load-bearing beams of an automobile overpass. Using the developed devices, a local dosed loading with a hemispherical indenter was carried out through shock or static loading of a pre-magnetized region of the structure resulted in a decrease in the intensity of the magnetic field of scattering. A procedure for monitoring uniaxial stresses in steel structure elements by the method of magnetoelastic «memory» is proposed taking into account the measured magnetoelastic sensitivity of their material.

Construction monitoring on the unloading process of steel roof for Guilin Liangjiang International Airport Terminal T2

The main building of Guilin Liangjiang International Airport Terminal T2 adopts the steel reinforced concrete frame structure, the central roof uses the spatial solid web arch support and single-shell steel structural system with the largest supporting arch span of 120 meters, and the single-shell steel structural system is connected with the spatial solid web arch through diagonal bracing. The large-span space steel structure of the roof had a large building area, and more than 300 lattice columns were used for temporary support in construction. In the unloading process of steel structure, the deformation and stress of the structure changed greatly. Simulation for all construction steps of the main steel structure, the key steel members and structural locations with large deformations were found out, and the monitoring scheme of deformation and stress of steel structure were determined. The stress monitoring of steel structural was completed by the self-developed wireless stress monitoring system. The deformation monitoring points were automatically searched by the deformation robot, and the three-dimensional coordinates of each monitoring points were measured. The measured results were compared with the initial data, and the deformation of structure was obtained. In the whole process of stress and deformation monitoring, the early warning values were set according to structural analysis and material properties, which could help engineers to make decisions on the structural safety. After the smooth construction of the project, we would find that the monitoring system meted the monitoring requirement during the construction stage, and the result was an important evaluation index for the structure. The research methods used in this paper could be seen as useful reference for construction of similar projects.

Method for defining residual stresses in arched profiles

In the process of manufacturing arched steel thin-walled cold-formed profiles with trapezoidal corrugations, by rolling a flat profile into the arch through a system of rollers, in the normal section profile longitudinal technological residual normal stress are formed, unevenly distributed over the height of the section. Currently, these residual stresses are not taken into account in the design, which leads to errors in the calculations for strength and local stability of arched structures made of arched profiles. There is a number of ways for defining the residual stresses in steel structures, including arched thin-walled profiles. Still, they have a number of significant disadvantages associated with the low accuracy of the values obtained and the complexity of stress calculations. The purpose of this work is to develop a method for defining the residual longitudinally oriented normal stresses in the flanges of arched cold–formed profiles with trapezoidal corrugations, combining the simplicity of the measurement technique, calculation and high accuracy of the obtained stress values. As a result, we obtained a method of defining the residual longitudinally oriented normal stresses in cross-sections of the arched profile as in the compressed and stretched flanges for easy calculation and high enough for engineering calculations, the accuracy of measurements of parameters of the profile to calculate stresses. The proposed method can be used to define the longitudinal residual stresses in normal sections of arched profiles with subsequent consideration of these stresses in the design of structures.

Мобильный магнитометрический комплекс для контроля остаточных механических напряжений в стальных конструкциях

Мобильный магнитометрический комплекс для контроля остаточных механических напряжений в стальных конструкциях

The Law of Response of LCR Wave in the Plastic and Elastic Deformation in A36 Steel

Nowadays the method of the longitudinal critical refraction wave (LCR wave) is an effective method to nondestructively measure the on-line stress in the huge steel structures. The present study and research of the method of LCR wave are mainly focused on measuring the residual stress in the steel structures, in contrast to the few research findings related to the on-line stress measurement in steel structures (including the elastic and plastic deformation). Based on the Acoustoelastic effect, the LCR wave stress measurement system is built to measure the change of time of LCR wave propagating, stress coefficient and the energy of LCR wave in A36 steel test specimens from the elastic deformation to the plastic deformation. The conclusion is: At the free-stress condition, the flight time of LCR wave and stress coefficient show an obvious change between the elastically deformed test stage and plastically deformed stage. The change of flight time and the intensity attenuation of LCR wave show a turning point, when the specimen undergoes the process from elastic deformation to plastic deformation. And the extent of plastic deformation in the steel structure can be evaluated by the extent of intensity attenuation of LCR wave. The experimental method will be showed in this paper for measuring the extent of plastic deformation in the steel structures in service on construction scene using the LCR wave method.

Determination of uniaxial stresses in steel structures by the laser-ultrasonic method

This paper describes the experimental implementation of the laser-ultrasonic method for diagnosing mechanical compression and tensile stresses in steel structures, based on the acoustoelasticity effect. The special laser-ultrasonic transducer that provides the laser excitation and highly sensitive piezoelectric detection of head (longitudinal subsurface) ultrasonic waves is developed. It is shown on the example of R65 rail samples of various quality that, regardless of the structural phase state of the rail, there is one and the same linear relationship between the relative variation of the velocity of head ultrasonic waves and the absolute value of uniaxial compression and tensile stresses acting in the rail.

Determination of Uniaxial Stresses in Steel Structures by the Laser-Ultrasonic Method

Determination of Uniaxial Stresses in Steel Structures by the Laser-Ultrasonic Method

Non-destructive identification of residual stresses in steel under thermal loadings

We discuss computational aspects of the inverse and ill-posed problem of identifying residual stresses in steel structures under thermal loading. This corresponds to an inverse source problem in linear thermo-elasticity. The studies aim in investigating whether thermal loadings for the excitation of structures are sufficient in order to detect reliably inherent residual stresses. These stresses may result from the construction process or later thermal or mechanical treatment of the structure-like welding. By answering the raised question positively, our method provides an important basis for successful thermal straightenings. The quality of the solution of the inverse problem depends on a series of parameters, like material parameters, noise in the measurements, and the experimental setup. We numerically study the effects of these parameters and quantify the uncertainties in the results of the inverse problems by means of Sobol indices.

Wireless Network Node to Monitor Stress in Steel Structures

The article presents a wireless measuring node operating in a system monitoring stress in steel structures. Stress sensor is a foil strain gauge, working in a half-bridge circuit. The presented node is based on the microcontroller Atmeg 8, and the data transmission modem used 433 MHz band. The use of 22-bit ADC allows for measurement of the stresses at 4 u-strain resolution. The article discussed the structure of the node, installation problems in the actual real projects and the results of laboratory tests. Based on the research it can be concluded that the measuring node can be used to monitor the load caused by residual snow on the steel roofs. DOI: http://dx.doi.org/10.5755/j01.eie.22.5.16343

INFLUENCE OF MAGNETIC FIELD ORIENTATION ON WELDING RESIDUAL STRESS

Since the rule of pulse magnetic treatment,which is a novel method to reduce residual stress in steel structures,has not been clear yet,the magnetic field orientation,which is a key factor influencing the variation of residual stress in the process of magnetic treatment,is studied.Firstly,samples with required stress are manufactured by bead on plate welding.Secondly, residual stress distribution is surveyed by hole-drilling method. Then different samples are processed in the magnetic field with different orientations and the residual stresses are measured again.By comparing the residual stress before and after treat- ment,it is shown that under the same conditions different mag- netic field orientations will lead to different residual stress variations.When the field is parallel to the maximal stress, residual stress is changed imperceptibly,while residual stress can be changed obviously if the applied field is perpendicular to the maximum stress.In order to explain the orientation phe- nomena,the magnetostriction under different field orientations is investigated.And the experimental results show that magne- tostriction performs dramatic differently with different magnetic field orientations,which may be the main reason to explain the relationship between field orientations and residual stress varia- tions.

Measurement of stress in steel structures with SH wave EMATS: MacLauchlan, D.T.; Burns, L.R.; Alers, G.A. Review of progress in quantitative nondestructive evaluation, Williamsburg, Virginia (United States), 22–26 Jun. 1987. Vol. 7B, pp. 1399–1404. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988.

Measurement of stress in steel structures with SH wave EMATS: MacLauchlan, D.T.; Burns, L.R.; Alers, G.A. Review of progress in quantitative nondestructive evaluation, Williamsburg, Virginia (United States), 22–26 Jun. 1987. Vol. 7B, pp. 1399–1404. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988.

Measurement of stress in steel structures with SH wave EMATS: MacLauchlan, D.T.; Burns, L.R.; Alers, G.A. Review of progress in quantitative nondestructive evaluation, Williamsburg, Virginia (United States), 22–26 Jun. 1987. vol. 7B, pp. 1399–1404. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988

Theories have been developed by several authors to calculate velocities of bulk, guided and surface waves in polycrystalline aggregates of cubic metals. These theories can be used to predict the effect of texture on ultrasonic velocity in rolled aluminium and steel sheet, provided that the effects of dislocations, second-phase particles, inclusions, etc. can be ignored. The theories predict that ultrasonic velocities will will be influenced by three orientation distribution coefficients (ODCs). The ODCs are quantitative measures of the texture in the material; in general, more than three ODC are required to completely characterize texture. Neutron diffraction pole figures can also be used to obtain the ODCs. Neutron diffraction measurements of ODC can be compared against ultrasonic values to obtain an independent check on the validity of the ultrasonic theories. In this work, the texture of thin sheets of a commercial grade aluminium alloy was measured with both ultrasonics and neutron diffraction. Several ultrasonic techniques were employed, using bulk, guided and surface waves. Both piezoelectric and electromagnetic-acoustic transducers (EMATs) were used. Quantitative measurements of texture made with different ultrasonic techniques were in good agreement. These ultrasonic measurements also agreed with neutron diffraction measurements, indicating that the dominant features of the effect of texture on wave propagation have been modelled with sufficient accuracy. The extension of the ultrasonic technique to on-line (production) monitoring of texture is considered. In particular, it appears that EMATs are the transducer of choice for on-line texture measurement of rolled sheet, since they are non-contacting.