Steel Suspension Research Articles

Estimation of the Anti-sliding Safety Factor Between the Main Cable and Middle Saddle of Three-Pylon Steel Suspension Bridges

Estimation of the Anti-sliding Safety Factor Between the Main Cable and Middle Saddle of Three-Pylon Steel Suspension Bridges

Effect of austenitisation and tempering treatments on the mechanical properties of advanced high strength spring steel SAE 9254

In response to increasingly stringent global regulations within the automotive industry, there is a growing demand for lightweight yet high-strength steel suspension coil springs. This study undertakes a comprehensive examination of the critical factors influencing the mechanical properties of SAE 9254, a well-established spring material, in its quenched and tempered (QT) state. The primary objective is to optimise its strength and ductility, especially in high-performance applications with an emphasis on lightweight design. The investigation encompasses a detailed exploration of the effects of varying austenitisation temperature (AT) and austenitisation time (At) on the microstructure and mechanical properties of the steel. Of particular interest is the study of tempering temperatures ranging between 300°C and 350°C to elucidate the mechanisms responsible for enhancing the steel's strength. Notably, the findings highlight dislocation density as the primary factor driving the strengthening of martensitic spring steel. Furthermore, the pivotal role of austenite grain size before quenching becomes evident, influencing toughness, ductility, martensite block size, and the percentage of retained austenite (γR). This study provides valuable insights into optimising the mechanical properties of SAE 9254 spring steel for high-performance applications, achieving ultimate tensile strengths (UTS) exceeding 2100 MPa and a reduction in area (RoA) exceeding 30%. Notably, the properties attained for this grade are comparable to those achieved with microalloying additions. Consequently, this research underscores the significance of controlling austenite grain size and dislocation density as critical factors for tailoring the properties of martensitic steels, positioning them as competitive materials, particularly in the pursuit of lightweight design.

Road vehicle shock detection algorithm using the Hilbert envelope

Detecting and characterising shocks is challenging because they do not occur in isolation but are instead superimposed onto underlying vehicle vibrations which themselves are a result of the interaction with uneven road surfaces. Consequently, shocks are buried within vehicle vibration response measurements (usually acceleration). This paper presents the development and validation of an automated algorithm to detect shocks from vertical acceleration signals measured from road vehicles. To avoid inherent difficulties with experimentation, this initial paper is confined to numerical simulation whereby the response of two typical quarter-car truck models (one with air ride and the other with steel suspension) when travelling on artificially-generated random road elevation profiles laced with Hanning-shaped surface aberrations of known amplitude, lengths and location along the elevation profile. The shock detection algorithm was developed as a dual mode classifier to accommodate the two natural frequencies of each 2DoF quarter car models. Detection was implemented by first passing the vibration response signal through a band-pass filter around the two resonant modes in turn then calculating the filtered signals’ instantaneous frequency (envelope) by means of the Hilbert transform. Shock detection was based on the local peak-to-mean ratio (LPTMR) of the instantaneous magnitude where ‘local’ was defined by the duration of the filtered signal's impulse response function. Sensitivity analysis and validation were undertaken on artificially-generated roads of varying roughness onto which aberrations of known shape were superimposed. The effectiveness and limitations (detection threshold) of the algorithm were evaluated by creating a range of aberrations with a broad range of lengths (effective frequencies) and diminishing amplitudes. Results show that shocks of ‘significant’ magnitudes are always detected with no detection of false positives. As the road roughness increases relative to the aberration amplitudes, the resulting shocks become increasingly drowned-out by the vibration response due to the underlying road roughness, especially for the quarter-car model with steel suspension. The main conclusion is that the signal analysis approach taken is ultimately effective and needs to be further validated using experimental response data.

Corrosion studies of various salt solutions on metals and alloys

Corrosion studies of various salt solutions on metals and alloys

Fatigue Life Modelling of Steel Suspension Coil Springs Based on Wavelet Vibration Features Using Neuro-Fuzzy Methods

This study proposed wavelet-based approaches to characterise random vibration road excitations for durability prediction of coil springs. Conventional strain-life approaches require long computational time, while the accuracy of the vibration fatigue methods is unsatisfactory. It is therefore a necessity to establish an accurate fatigue life prediction model based on vibrational features. Wavelet-based methods were applied to determine the low-frequency energy and multifractality of road excitations. Strain-life models were applied for fatigue life evaluation from strain histories. ANFIS modelling was subsequently adopted to associate the vibration features with the fatigue life of coil springs. Results showed that the proposed wavelet-based methods were effective to determine the signal energy and multifractality of vibration signals. The established vibration-based models showed good fatigue life conservativity with a data survivability of more than 90%. The highest Pearson coefficient of 0.955 associated with the lowest RMSE of 0.660 was obtained by the Morrow-based model. It is suggested that the low-frequency energy and multifractality of the vibration signals can be used as fatigue-related features in life predictions of coil springs under random loading. Finally, the proposed model is an acceptable fatigue life prediction method based on vibration features, and it can reduce the dependency on strain data measurement.

Numerical simulation of tasks of vertical viscoelastic oscillation of suspension systems of frame, engine, cabin and seat

The analysis of the structures of the springing systems of modern vehicles showed that polymer composites are used in vehicles for which the decrease in curb weight is a critical indicator. The use of springs (suspensions) from polymer composites makes it possible to reduce the weight of the elastic element and increase durability while improving the smoothness of movement, reducing noise, and increasing traffic safety. When replacing the steel suspension with a polymer composite suspension, the mass of unsprung parts of the car decreases, and the economic performance of wheeled vehicles improves. The article discusses the problem of vertical viscoelastic oscillations of the suspension systems of the skeleton, engine, cabin, and seat. When considering the suspension's rheological properties, the Boltzmann-Volterra integral model is used. The Koltunov-Rzhanitsyn nucleus is used as a nucleus, which has weakly singular features of the Abel type. The system of integro-differential equations describing the studied process is solved by a method based on the use of quadrature formulas. The effect of the parameters of the hereditary-deformable properties of the suspension on the vibration shape is shown.

Dynamic responses of 500-kV transmission line towers under impact force of rockfall in a mountainous area

Since most of the UHV/EHV transmission lines pass through mountainous areas, the impact of rocks caused by landslides or collapses may cause partial deformation of the iron tower, or even collapse, seriously threatening the safety operation of transmission lines. To analyze the dynamic response characteristics and influencing factors of the rolling rock impacting the transmission line tower, a simulation model for the 500-kV steel suspension tower impacted by the falling rock was established by finite element analysis software LS-DYNA in this study, and dynamic response characteristics of the rolling rock impacting the steel tower were analyzed under different conditions. Results show that the stress on the tower foundation is closely related to the mass, volume, and initial velocity of the rolling stone. Under the same rolling stone speed, the stress on the tower foundation increases as the mass of the rolling stone increases. The maximum increase in peak stress generated between the two can reach 110%; when rolling stones of the same size collide with different initial velocities, the location and magnitude of the peak stress of the tower foundation are different. When the initial speed of the rolling stones is more remarkable than 15 m/s, the tower foundation of the hit area increased significantly, causing the tower base to be directly destroyed.

Application of machine learning algorithms for the optimization of the fabrication process of steel springs to improve their fatigue performance

Machine Learning algorithms are aimed at building generalizable models to provide accurate predictions or to find patterns from noisy data. These characteristics are potentially beneficial for the fabrication of steel products. In this research, 529 rotating bending fatigue tests (R = -1 and σa = 400 MPa) were carried out on steel suspension spring bars fabricated using different combinations of manufacturing parameters. A reliable regression model (R2 = 0.877 on the test dataset) based on the Gradient Boosting algorithm was obtained. The interpretation of the model was carried out through the Permutation Importance algorithm, revealing the relevance of the temperature in the tempering treatment applied after quenching on the fatigue lifespan. This pattern was quantitatively described by means of the Partial Dependence Plot of this feature. Besides, a specific study was carried out to obtain a reliable interpretation of the results derived from the Machine Learning analysis. In this sense, it has been observed that specimens subjected to high temperature tempering display a lower surface hardness that provokes a higher surface roughness after shot peening; this, in turn, facilitates the initiation of surface cracks during the fatigue tests reducing the fatigue lifespan. This study provides a reliable framework to optimize the suspension spring manufacturing conditions to increase their fatigue lifespan as well as an example, generalizable to other manufacturing processes, of the potential benefits of Machine Learning.

Dynamic Behavior of a Suspended Steel Space Frame-Glass Composite Floor

This study investigates the dynamic performance of a large-span suspended steel space frame-glass composite floor (SSSF-GCF). Both the ambient vibration and the human-induced vibration of the floor were experimentally measured to identify vertical dynamic characteristics and evaluate vibration serviceability of the floor. Although vertical dynamic characteristics of the floor based on the global simplified finite element (FE) model of the structure agree well with those identified via experimental modal analysis, the global simplified FE model significantly underestimates vertical vibration amplitudes of the floor due to the coupled effect between two layers. Accordingly, an equivalent local FE model of the floor system was proposed and updated via adjusting the vertical stiffness of the interstory hanging pillars. It is shown that the equivalent local FE model can well predict both the dynamic characteristics and human-induced vibration response of the floor. Finally, the effect of the damping ratio on the acceleration response of the floor was numerically demonstrated with the verified local FE model.

A multi-resolution deep feature framework for dynamic displacement measurement of bridges using vision-based tracking system

Structural displacement is an imperative indicator for safety evaluation and maintenance. To address the limitations of conventional displacement sensors, advanced non-contact vision-based trackers offer a promising alternative. Based on the reconstructed Efficient Convolution Operator (ECO), a more powerful multi-resolution deep feature framework is proposed to efficiently encode the informative representation. The fusion of the shallow convolutional and the deep convolutional features is discriminative while preserving spatial and structural information. Furthermore, the discrete feature map is transferred to the continuous spatial domain by introducing an interpolation operator to achieve accurate sub-pixel registration. A careful comparison of the results on the steel suspension bridge demonstrates the high accuracy of the multi-resolution deep feature tracker (MDFT) for displacement measurement. The performances in the time and frequency domain show decent agreement with the results acquired by the laser displacement sensor (LDS), which confirm the low-cost, target-free, high resolution, and non-contact measurement capacities.

Experimental Investigation of the High-Temperature Performance of High-Strength Steel Suspension Bridge Wire

Abstract Quantification of the mechanical properties of suspension bridge main cables during fire hazards is a vital part of holistic safety assessment of infrastructure. While some researchers hav...

A Study on Live Load Deflection Criteria of Long-Span Steel Bridges

Under-clearance of bridges is one of the major considerations when planning and designing bridges. Especially for sea-crossing bridges, under-clearance is more important for safe passage of ships. Long span cable bridges with steel orthotropic deck usually show relatively large deflections and excessive deflections may be not only disadvantageous to the clearance plan, but also a problem in bridge serviceability. The clearance of sea-crossing bridge is designed with air draft from the waterline to top of mast, ship’s trim, psychological free space, sea level, height of wave and bridge deflection by live loads. At design stage, bridge engineers need a live load deflection limit to ensure adequate clearance. The limitation of live load deflection is also considered for ensuring the serviceability of vibration of bridges. For vibrational serviceability, the live load deflection limit is expressed as a ratio to the span or the formula by natural frequency. On the other hand, some standards specify vibration serviceability limit by peak or root-mean-square (RMS) acceleration. The purpose of this study is to propose new deflection limit criteria for long span steel cable bridges based on analysis and long-term measurement data. Structural analysis was performed on two steel suspension and three steel cable-stayed bridges with more than 200 m of main span under design live load model of DL24 and new live load model KL510 in limit state design code. Also, the deflection limit criterion was evaluated by probabilistic method using the deflection data measured for 1 year. The results of this study are expected to be useful data for bridge engineers designing long span steel cable bridges.

Empirical Modeling and Optimization of Laser Bending Process Parameters using the Central Composite Design Method for HDD Slider PSA/RSA Adjustment

This paper details the development and optimization of a laser adjustment process for the pitch static attitude and roll static attitude (PSA/RSA) to achieve the maximum bending angle without the burning of materials. The effects of process parameters (or factors) including the laser power, pulse repetition rate, and scanning time were investigated based on the central composite design method. Experiments were performed on a stainless steel (SST-300 series) suspension using a solid-state laser system and a charge-coupled device camera with image processing technology. Regression models of positive and negative PSA/RSA (or response) values were developed through a total of 20 experimental runs. The results showed that the PSA/RSA bending angle increases with increasing laser power and pulse repetition rate, while the bending angle decreases with increasing scanning time. The optimization determined that a higher laser power and lower scanning time had a more significant effect on the bending angle. However, the laser power cannot be increased above the melting point of the material, as this will lead to the formation of spongy debris on the stainless steel. The models were shown to accurately describe the relationship between the factors and responses. In addition, the laser bending mechanism for the PSA/RSA adjustment of a hard disk drive slider was investigated.

Pre-deflecting a steel platform to support a new organ at Manchester Cathedral, UK

The cathedral in Manchester, UK, is one of the most impressive examples of a late mediaeval collegiate church in England. The cathedral has been without a permanent organ since the 1940s, and since then, there has been an aspiration to reinstate one. In 2010, the cathedral commissioned a new grander organ, almost twice the size of its predecessor and weighing approximately 15 t. It was to be positioned beneath the chancel arch, in a prominent central setting between the nave and the choir. The organ would be supported 3.5 m above ground level on a suspended steel platform concealed within the pulpitum. The challenge was to provide a platform within the constraints of not loading the mediaeval rood screen, no visible structure, no discernible deflection during the construction of the organ and with full reversibility. The steel platform was preloaded with a series of lead weights to induce the permanent deflections before the building of the organ itself was started. The lead weights were sequentially removed during the organ building to control the deflection and the load transfer to the existing Victorian cast-iron structure.

CONSTRUCTION Process Analysis of Giant and Complex Steel Structures

The main structure of Xi ’an Silk Road International Conference Centre is a giant steel braced frame structure. The façade of the structure is made up of huge suspended skirtlike suspended structure supported by cantilever roof trusses and steel suspensions, which adds up its complexity. In order to accurately control the installation precision and facilitate the installation of curtain wall glass in the later stage, the pre-chamber construction method is adopted in the roof truss installation to compensate the construction deformation of suspended structure. The static analysis is conducted by SAP2000 to propose a reasonable pre-camber value of the roof cantilever truss. The nonlinear simulation of the construction process is carried out. Through comparative analysis, the optimal sequence of the steel structure construction is obtained, which provides the theoretical basis for the construction of giant and complex steel structures.

Machine Vision-Based Monitoring Methodology for the Fatigue Cracks in U-Rib-to-Deck Weld Seams

The orthotropic steel-box girder (OSG) is widely used in the construction of a large-scale bridges. Since cumulative damages caused by the heavy vehicles and initial flaws of welding, the bridges with OSGs frequently suffer from fatigue cracks, which are commonly distributed around U-ribs. Hence, the management of fatigue cracks is mandatory in practical engineering. Although some techniques have been adopted for the detection of cracks, the workflow is often labor-intensive, time-consuming, and of low-temporal resolution. Considering the optical visibility of a crack and the limitation of the shape of an over-welding-hole around the U-rib, a machine vision-based monitoring methodology for the fatigue cracks in U-rib-to-deck weld seams is proposed in this paper. To be specific, a specific Internet of Things (IoT) based image acquisition device is first developed and introduced to obtain precisely part-view images of a fatigue crack. As followed, a novel image rectification and stitching method based on a specified coded calibration board is innovated and described for generating a measurable panoramic fatigue crack image. Furthermore, a deep learning-based crack detection-segmentation integrated algorithm is developed to detect and segment the crack areas. Afterwards, a feature extraction procedure based on image processing is explored to obtain the morphological features of a crack, involving its area, length and width. Finally, a field experiment was carried out on a real steel suspension bridge. By comparing the measurements both from manual measuring and vision-based monitoring, the results indicate that the proposed methodology is very promising to monitor the fatigue cracks in U-rib-to-deck weld seams, and the root-mean-square errors in length and width measuring could be 3.0195 mm and 0.003 mm, respectively. This work is not only of practical value to the management and maintenance of the OSG bridges in engineering, but also critical for the researches on fatigue cracks propagation.

Unknown impact force localisation and reconstruction in experimental plate structure using time-series analysis and pattern recognition

Impact force is the load that actual structures often experience, and its localisation and time-history reconstruction are important for structural health and safety monitoring. However, classical inversion techniques for random impact-force identification are time-consuming and infeasible; therefore, they cannot be utilized for engineering applications. This study adopted multiple time-series analyses and a pattern-recognition method to identify unknown random impact forces, and this strategy is known as the pattern-recognition method combined with a similarity metric (PRMCSM). Numerical simulations of the proposed method have been conducted; however, their findings have not been experimentally verified. From an experimental perspective, this study considered suspended steel plate as the research object, impact force as the load input, and acceleration as the response output. The PRMCSM algorithm based on cosine similarity was verified, and the expected results were obtained. Moreover, various similarity metric indices are proposed to implement the feature extraction of time-domain responses, and a novel index that is not lower than cosine similarity was finally determined and was verified based on the PRMCSM strategy. In summary, the method based on pattern recognition achieves the rapid identification of random impact forces and exhibits potential for practical engineering applications.

Coupling effects between wind and train transit induced fatigue damage in suspension bridges

Long-span steel suspension bridges develop significant vibrations under the effect of external time-variable loadings because their slenderness. This causes significant stresses variations that could induce fatigue problems in critical components of the bridge. The research outcome presented in this paper includes a fatigue analysis of a long suspension bridge with 3300 meters central suspended span under wind action and train transit. Special focus is made on the counterintuitive interaction effects between train and wind loads in terms of fatigue damage accumulation in the hanger ropes. In fact the coupling of the two actions is shown to have positive effects for some hangers in terms of damage accumulation. Fatigue damage is evaluated using a linear accumulation model (Palmgren-Miner rule), analyses are carried out in time domain by a three-dimensional non-linear finite element model of the bridge. Rational explanation regarding the above-mentioned counterintuitive behavior is given on the basis of the stress time histories obtained for pertinent hangers under the effects of wind and train as acting separately or simultaneously. The interaction between wind and train traffic loads can be critical for a some hanger ropes therefore interaction phenomena within loads should be considered in the design.

Monitoring Instantaneous Dynamic Displacements of Masonry Walls in Seismic Oscillation Outdoors by Monocular Digital Photography

Understanding the development of cracks in masonry walls can provide insight into their capability for earthquake resistance. The crack development is characterized by the displacement difference of the adjacent positions on masonry walls. In seismic oscillation, the instantaneous dynamic displacements of multiple positions on masonry walls can warn of crack development and reflect the propagation of the seismic waves. For this reason, we proposed a monocular digital photography technique based on the PST-TBP (photographing scale transformation-time baseline parallax) method to monitor the instantaneous dynamic displacements of a masonry wall in seismic oscillation outdoors. The seismic oscillation was simulated by impacting a suspended steel plate with a hammer and by simulation software ANSYS (analysis system), for comparative analysis. The results show that it is feasible to use a hammer to impact a suspended steel plate to simulate the seismic oscillation as the stress concentration zones of the masonry wall model in ANSYS are consistent with the positions of destruction on the masonry wall, and that the crack development of the masonry wall in the X-direction could be characterized by a sinusoid-like curve, which is consistent with previous studies. The PST-TBP method can improve the measurement accuracy as it corrects the parallax errors caused by the change of intrinsic and extrinsic parameters of a digital camera. South of the test masonry wall, the measurement errors of the PST-TBP method were shown to be 0.83mm and 0.84mm in the X- and Z-directions, respectively, and in the west, the measurement errors in the X- and Z-directions were 0.49mm and 0.44mm, respectively. This study provides a technical basis for monitoring the crack development of the real masonry structures in seismic oscillation outdoors to assess their safety and has significant implications for improving the construction of masonry structures in earthquake-prone areas.

Response analysis with cable3D of the SCR rigid rotation model under the wave action and y direction motion in the oil production and transportation

The steel catenary riser(SCR) is an important equipment for offshore oil production. Its research is very important for the safety of oil exploitation. The SCR has a rigid rotation axis from the hanging point to the touch down point(TDP). The influence of rigid body rotation on the response of the cross flow is not negligible. This paper considers the bending vibration model, the rigid body model, and the wave forces mode. The effects of rigid body rotation on the structure acted on wave action and y direction motion is studied. The calculation shows that the response of the structure is the largest in the top area and the structure response value no longer changed greatly after a certain depth. The higher the amplitude in the top region, the faster the response goes down. After coupling top y-direction motion, the phenomenon of decreasing with response of water depth is still present, and the effect of rigid body swing on the structure is not more than that of the wave load. It is expected that the above research can be helpful for the design of steel suspension chain riser.