Longitudinal Stress Distribution Research Articles

Residual stress distributions of trapezoidal corrugated web I-members: Experimental and numerical study

This study utilized the hole-drilling method to determine the residual stress distribution in the sections of trapezoidal corrugated web I-members (TCWM). Then, using ABAQUS software, welding simulations and a parameter study of the longitudinal residual stress distribution for TCWM sections are conducted. Finally, a distribution model of the longitudinal residual stress for TCWM sections are proposed. The research findings indicate that the existing residual stress distribution models for flat web I-sections are unsuitable for predicting the residual stress distribution in TCWM sections. Moreover, the longitudinal residual stress distribution in the flanges of TCWMs varies with the position of trapezoidal corrugated webs (TCW). Specifically, the maximum residual tensile stress in the flanges with the parallel web fold surpasses that of the inclined web fold by approximately 10 %. With an increase in corrugation angle, the range of residual tensile stress in the flanges increases. Unlike the flat web of I-sections, there is almost no longitudinal residual stress in the middle area of the TCWs. The proposed models of residual stress distribution for TCWM sections consider the influence of corrugation and cross-sectional dimensions and align well with both experimental and numerical results.

Axial performance of square steel tube and sandwiched concrete jacketed circular CFST columns

Although extensive experimental and numerical studies have been conducted on the axial performance of steel tube and sandwiched concrete jacketed CFST columns, contableurations with outer square tubes and inner circular CFST components are rarely found. This paper investigates the axial performance of square steel tube and sandwiched concrete jacketed circular CFST columns, examining the effects of outer steel ratio and sandwiched concrete strength on failure patterns, relative load-strain curves, and load-bearing capacity. The analysis of ultimate compressive capacity confirmed the effective confinement provided by the outer square steel tube. Based on the experimental results, a finite element model was established to further study the working mechanism of retrofitted columns. The load on components, distribution of longitudinal stress and transverse constraint stress on concrete revealed that the inner concrete experiences dual confinement effects from both inner and outer steel tubes, with the constraint of the outer square steel tube becoming significant only during the load dropping phase. Furthermore, a simple equation was proposed for predicting the axial compressive load-bearing capacity of retrofitted columns using superposition methods and design codes. Comparison results demonstrated good agreement between experimental and calculated values.

Microscale and mesoscale modeling for compressive failure in unidirectional carbon fiber reinforced polymer composites with random distribution of fiber misalignments

AbstractCompressive strength and failure mode of carbon fiber reinforced polymer (CFRP) composites are affected by the severity of fiber misalignment. In this paper, numerical models based on computational micromechanics are proposed to investigate the correlation between fiber misalignment and compression failure. A single‐fiber micromodel including fiber, matrix, and interface phases is first developed to capture the influence of misalignment severity on the material failure mode. The failure longitudinal stress distribution in the fiber predicted by the micromodel indicates that the failure mode depending on the initial misalignment can be identified as uniform compression failure, compression‐bending combination collapse, and fiber buckle. A mesoscale 2D model with multiple fibers is then constructed to investigate the kink band formation. This model takes into account the distribution of fiber misalignments to capture the key geometric features of fiber misalignment that influent the compression failure in realistic composite materials at the structural scale. The results show that fiber misalignment angle amplitude, misalignment dispersion (characterized by the standard deviation), and misalignment wavelength are the key parameters of fiber misalignment, which have significant effects on compression strength and kink band geometry.Highlights Single‐fiber model to capture the effect of misalignment severity on failure mode. Multi‐fiber model with randomly distributed fiber misalignments. Failure mode depending on the severity of initial misalignment was identified. Key parameters of misalignment on compression strength and kink band geometry.

Exploring the Influence of Vibration Impact and Electric Spark on Aluminum Alloy Stress Fields

Vibration Impact Compound Electric Spark (VIES) is a technology that combines the advantages of vibration impact and electric spark surface enhancement. Due to its simple process, cost-effectiveness, and superior efficiency, it has attracted considerable attention in industrial applications. Through finite element simulation analysis, this study designed orthogonal experiments to explore the impact of VIES on the stress field distribution of aluminum alloy plates. The results indicate that factors such as impact frequency, impact height, and electric current have a certain influence on the distribution of longitudinal residual pressure stress in aluminum alloy plates. The experiments indicate that increasing the impact height within a certain range leads to an increase in residual stress at the impact site, but the depth of the compression stress layer decreases. Meanwhile, increasing the impact frequency increases the residual stress at the impact site, while the depth of the compression stress layer remains constant. In summary, both impact height and frequency have an impact on the stress in aluminum alloy plates. Additionally, orthogonal experimental results suggest that electric current has no significant effect on the stress field.

Dynamic Stress Response in a Novel Prestressed Subgrade under Heavy-Haul Train Loading: A Numerical Analysis

To explore the dynamic transient characteristics induced by passing heavy-haul trains in newly-developed prestressed subgrade, two three-dimensional finite element models were constructed in the time domain using ABAQUS software. These models are categorized as train-track-prestressed subgrade and train-track-unreinforced subgrade. The numerical models also incorporated the vertical track irregularity commonly found in heavy-haul railways. The investigation aims to discern the dynamic stress response differences in both types of subgrades under three distinct train axle loads. Model validation occurred through comparisons with field tests gathered from various heavy-haul railways in China, as well as analogous numerical simulation cases. The findings indicate that track irregularity results in an asymmetric distribution of dynamic stress on the subgrade surface beneath both left and right rails, aligned transversely with the subgrade centerline. Additionally, this asymmetry is notably pronounced. The peak dynamic stress on the subgrade surface beneath the rails for both subgrades increases with escalating train axle loads. However, the prestressed reinforcement structure (PRS) effectively modulates this phenomenon, with the controlling advantage intensifying as train axle load increases. The average dynamic stress level in the prestressed subgrade is marginally lower than in the unreinforced subgrade within the roadbed layer beneath rails. Furthermore, train axle loads amplify the variation level of dynamic stress in the subgrade. However, the variable coefficient of dynamic stress in the prestressed subgrade is less than in the unreinforced subgrade, suggesting that PRS contributes positively to maintaining subgrade dynamic stability. In terms of the longitudinal distribution of peak dynamic stress, both subgrades exhibit normal distribution at varying depths within the roadbed layer. Lastly, the additional dynamic stress in prestressed steel bars also rises with increasing train axle loads. Nonetheless, it remains substantially lower than the static target pre-tensile stress. Moreover, the dynamic responses of prestressed steel bars in different rows attenuate as depth increases away from the subgrade surface. In summary, the study establishes that PRS significantly enhances the dynamic stability of railway subgrade.

Computationally efficient simulation methodology for railway repair welding: Cyclic plasticity, phase transformations and multi-phase homogenization

The in-situ railway repair welding process consists of multiple weld passes, which makes it significantly different from other rail welding processes. In this study, finite element simulations of repair welding are performed to predict the resulting microstructure and residual stresses. To accurately simulate the material behavior, the modeling includes phase transformation kinetics, cyclic hardening plasticity, transformation induced plasticity, and multi-phase homogenization. More specifically, four different homogenization methods are investigated: isostrain, isostress, self-consistent and linear mixture rule. The performance of the material modeling is demonstrated by simulating multiple weld passes using a classical three-bar welding experiment. Based on the results, the self-consistent method and linear mixture rule are used in a 3D full-scale railhead repair weld simulation, in which the former generates a more realistic mechanical response. The immense computational cost associated with 3D full-scale, full-detail multi-pass welding simulations is addressed by exploring different model reduction schemes. From this study, a 2D generalized plane strain model, extended with out-of-plane axial and bending stiffness, is found to replicate the full-scale model at a mere fraction of the computational cost. Finally, the longitudinal residual stress distribution obtained from the reduced model is shown to correlate well with experimental measurements.

Mechanical behaviour of steel-concrete joint in hybrid girder cable-stayed bridge

A steel-concrete joint section test model was constructed based on a mixed-scale ratio of the Lancang River hybrid girder cable-stayed bridge in Jinghong City, Yunnan Province. The internal forces and test loading values during normal operations were determined using finite element analysis. The performance was analysed by determining the mechanical indicators at key positions during the loading process. A finite element model of the test girder section was established to analyse the force transmission mechanism of the studied steel-concrete joint section. The test results showed that the centroid of the section moved upward during force transfer from the concrete to the steel girder. The relative slippage at the steel-concrete interface resulted in local unloading and an uneven distribution of longitudinal stresses in the crosswise direction. In addition, the cooperative bearing of the steel-concrete joint girder was transformed to a single bearing of the concrete girder, leading to a monotonic variation of stresses in the web plate. The simulation results showed that the surface plate force-sharing ratio of the composite bridge was the highest. In addition, the force-sharing ratios under the axial force and bending moment scenarios were 57.65% and 78.91%, respectively, indicating that the investigated steel-concrete joint demonstrated good stiffness transition stability. Furthermore, four force transfer types were identified in the steel-concrete joints. The research outcomes provide a fundamental basis for the rational design of joint components applied in hybrid girder cable-stayed bridges.

Experimental investigations of residual stresses in thick high‐strength steel plates

AbstractResidual stresses strongly influence the load‐bearing capacity of steel members under compressive axial loads. Current developments in steel and steel‐concrete composite structures imply the use of high‐strength steel grades up to 960 MPa. For such steel plates, only limited results of residual stress investigations are known so far. The authors have applied two established measuring methodologies like the sectioning method and X‐ray diffraction to determine the residual stress state of 40 mm thick steel plates and different widths. The results show that the distribution and amount of longitudinal residual stresses are mainly determined by the oxyfuel‐cutting procedure used to manufacture the specimens. The distribution over the thickness could be determined by X‐ray diffraction. Compared to the results of examinations on lower‐grade steel plates an assumed correlation of residual stresses and steel grades could not be observed. Consequently, residual stresses have a reduced influence on the load‐bearing capacities of structures prone to buckling as the ratio of yield strength to residual stress states declines significantly.

Stress Distribution in a Railroad Track at the Crosstie–Ballast Interface

Excessive crosstie wear and abrasion and ballast wear and fouling are fundamental problems contributing to inadequate railroad track performance. This adversely affects the attainment and long-term maintenance of desired track geometric requirements. The magnitudes and distribution of the stresses at the crosstie–ballast (CT-B) interface must be known to determine the stress distribution on and within the ballast. However, the track design recommendations to determine these pressures, which are largely based on a methodology from the 1980s, are currently valid for modern-day railroad applications for multiple reasons discussed in this study. This study analyzed CT-B interfacial pressure data measured on an active freight mainline in Mascot, Tennessee. Dynamic contact pressures at the CT-B interface were measured using hydraulic earth pressure cells for various wheel loads and train speeds. The test train was a Federal Railroad Administration (FRA) test train consisting of a diesel electric locomotive, a test car that had different wheel loads based on the deployable axle load, and an inspection car. Although the maximum train speed was limited to 64 km/h, this research found that speed variation has a minimal effect on the CT-B interfacial pressures. From the measured data, a Gaussian stress distribution equation is proposed to determine longitudinal pressure distribution transmitted to the CT-B interface for static conditions. In addition, the stress distribution along the length of a crosstie was investigated via laboratory experimentation using a half-length crosstie. As a result of the experimentation, a dimensionless trilinear approximation was developed to estimate the stress distribution along the length of the crosstie. In general, this research recommends that the longitudinal and lateral stress distributions be considered together to design a better railroad track.

Numerical Investigation of the Influence of Boulder Concentration on Longitudinal Velocity and Shear Stress Distribution in Rough Bed Stream

Numerical Investigation of the Influence of Boulder Concentration on Longitudinal Velocity and Shear Stress Distribution in Rough Bed Stream

Assessment of residual stresses in welded T-joints using contour method

Welded T-joints are commonly used in manufacturing of stiffened panels or crossbeams. However, welding of web-to-flange joint induces residual stresses and distortions resulting in significant challenges during both manufacturing and service. These issues can ultimately impact the structural performance, including fatigue and stability, and lifetime of the weldment. The purpose of current paper is determining the distribution and magnitude of manufacturing-induced longitudinal residual stresses in welded T-joints. Influence of hot rolling, thermal cutting, prestressing, welding, etc. are all included using the so-called contour method. Deformed surfaces are measured using coordinate measuring machine after wire electrical discharge machining of specimens. An inverse linear elastic finite element analysis is carried out for assessing residual stresses after data smoothing. Two-dimensional longitudinal residual stress patterns are evaluated in representative cross-sections clearly indicating high stress peaks near the welds, even exceeding yield strength of the base material. In addition, longitudinal membrane residual stresses are determined based on through-thickness stresses. In addition, a simplified residual stress model, satisfying the requirement for equilibrium of internal forces and bending moments, is developed for welded T-joints with double-sided fillet welds based on contour method results.

Experimental Research on the Stiffness Step between the Main Hull and Superstructure of Cruise Ships

The demand for larger passenger capacity and more entertainment facilities has led to the rapid growth of the cruise tourism market. The superstructure of cruise ships is designed to be plumper, with numerous decks and complex structural forms. To control the weight and the center of gravity, the bending stiffness of the superstructure is always designed to be weaker than that of the main hull, resulting in a stiffness step. Currently, there is no satisfactory method to accurately estimate the influence of the stiffness step between the main hull and superstructure on the structural response of cruise ships. In the present research, an experimental analysis is conducted to investigate the stiffness step between the main hull and superstructure of a typical cruise ship. By comparing the longitudinal stress distribution characteristics with and without the stiffness step with the theoretical results, the influence of the stiffness step on the longitudinal strength is investigated. Furthermore, the maximum stress and the bending efficiency of the superstructure are also discussed. The present research is of reference significance for the structural safety and reliability design of cruise ships.

A layered beam-based model for analyzing the stress of rolling shear for the cross-laminated timber panels under out-of-plane bending

When used as horizontal components to carry vertical loads, such as floors and beams, the design of cross-laminated timber (CLT) panels is driven by out-of-plane bending. In this case, rolling shear is always one of the major concerns that governs the performances of ultimate limit state of CLT members. Analytical models are available for predicting the shear capacity of CLT panels, but they are computational extensive and cannot provide the longitudinal distribution of shear stress which is necessary to predict where the failure will happen. In this paper, a layered beam-based analytical model, for analyzing the stress of rolling shear for transversely loaded CLT members was developed. The model deems that the shear deformations of out-of-plane bending CLT members are carried by cross layers while the deformations of bending moment are carried by parallel layers. Based on the layered beam theory, the equation that governs the stress of rolling shear and its analytical solution were derived. It was found that the shear stress distribution in CLT longitudinal direction obeys exponential law and the maximum shear stress is located at the end of the CLT member. Formulas to predict the shear capacity for 3- and 5-layer CLT panels under out-of-plane bending were obtained. The proposed method was validated by the experimental data generated by the authors and by other researchers. Comparing to the shear analogy method and Gamma method, the proposed method requires less computational work and provides similar accuracy.

Laboratory investigation on early-age shrinkage cracking behavior of partially continuous reinforced concrete pavement

As a form of durable pavement structure commonly used in the world, continuously reinforced concrete pavement (CRCP) has prominent problems caused by irregular crack distribution in the early stage. According to the characteristics of the discontinuous distribution of CRCP longitudinal steel bar stress and active crack control method, a rigid pavement structure called partially continuous reinforced concrete pavement (PCRCP) was proposed to simultaneously optimize the crack distribution pattern and reduce the longitudinal steel ratio in this paper. Since early-age shrinkage cracking behavior is a key factor affecting its durability. This paper purposes to assess the early-age shrinkage cracking behavior of PCRCP by comparing different reinforcement methods in laboratory experiments. Research results indicated that the early-age shrinkage behavior of PCRCP is basically the same as that of CRCP. The early-age shrinkage behavior of PCRCP is significantly improved than the advanced reinforced concrete pavement (ARCP). Restricted by the boundary and longitudinal steel bars system, the concrete beam produces a top-down nonlinear temperature and humidity gradient, resulting in various degrees of shrinkage deformation at different depths inside. The active crack control method can control the early-age concrete slab to form uniform crack pattern with straight lines or fewer bending cracks, which improves early-age cracking behavior significantly. This paper is to further deepen and develop the theory of CRCP early-age cracking behavior and provide basic theory support for the subsequent experimental section studies of PCRCP.

Axial compression behaviour of circular concrete-filled double-skin steel tubular columns with bolted shear studs: Numerical investigation and design

The concrete-filled double-skin steel tubular (CFDST) columns have recently attracted significant attention for practical engineering constructions. The axial resistance behaviour of CFSDTs can be greatly enhanced by installing bolted shear studs as pin supports for the outer. This is a companion paper that expands on the authors' work [1]. The previous paper concentrated on full-scale experimental testing to ascertain the influence of bolted shear studs on the axial resistance of CFSDT columns, while this study focused on finite element (FE) analysis and a simplified design approach for such composite structural members. A three-dimensional FE model for predicting the axial behaviour of circular CFDST columns without and with shear studs was developed and validated using the test results of the specimens' typical failure mechanisms and load-displacement responses. The model was then employed to perform structural analysis by comparing the axial load-displacement curve, internal force distribution, longitudinal stress distribution over the sandwiched concrete, and confinement mechanism of a circular column with bolted shear studs with that of its counterpart without bolted shear studs. Parametric studies were carried out to examine the effects of bolt longitudinal spacing, diameter, length, and yield strength. It was found that the spacing of the bolts-to-width (bs/Do) ratio had significant effects on the axial resistance and ductile performance of columns. Also, a bolt spacing corresponding to bs/Do<0.44 was suggested to attain an acceptable ductile performance in practical application. Verification of the design model revealed that it led to satisfactory predictions of the ultimate strengths of circular CFDST columns without and with shear studs.

Residual stress and deformation in UHS quenched steel butt-welded joint

For the low-alloy ultra-high strength (UHS) quenched steels with a yield strength of 1500 MPa, the welded joints have two obvious characteristics, namely solid-state phase transformation (SSPT) in the heat-affected zone (HAZ) and softening effect in the subcritical heat-affected zone (SCHAZ). In the current study, a UHS single-pass butt-welded joint with filler wire of ER307Si was fabricated, and thermal cycles at specific points were measured by thermocouples. After welding, relevant measurements of residual stress, deformation, microstructure and hardness were carried out. In this paper, based on the experimental hardness on the cross-section of the joint, a novel softening model was proposed. Meanwhile, based on coding subroutines of ABAQUS software, an advanced computational approach considering the thermal-metallurgical-mechanical coupling behaviour including the strain hardening as well as the annealing effect in fusion zone, SSPT in HAZ, and softening in SCHAZ was developed to implement thermal, metallurgical and mechanical analyses of the UHS quenched steel butt-welded joint. Comparing numerical and experimental results of temperature field, residual stress distribution and welding deformation of the joint, the calculated results of welding residual stress, angular distortion and transverse shrinkage are in good agreement with the measured data when both SSPT and softening effect were considered in the finite element model. The computed results indicate that SSPT has a significant influence on both the magnitude and the distribution of longitudinal residual stress, but it has a small effect on transverse residual stress. Moreover, the softening effect dramatically decreases the peak value of longitudinal residual stress in the SCHAZ, while it has an insignificant influence on transverse residual stress. The simulation results suggest that SSPT has a small effect on both transverse shrinkage and angular distortion, while the softening effect has very limited influence on welding deformation.

Rapid calculation of part scale residual stress – Powder bed fusion of stainless steel, and aluminum, titanium, nickel alloys

A novel analytical model is developed to compute the part scale through-thickness longitudinal residual stress distributions and applied for laser powder bed fusion of four commonly used powder alloys. An important input for the analytical modeling calculations is the peak residual stress for a deposited layer, which is estimated using a unique functional relationship and presented as a function of important process conditions for laser powder bed fusion of different powder alloys. The analytically calculated results of longitudinal residual stress distributions through the part and baseplate thickness are tested rigorously with the corresponding numerically computed and experimentally measured results in the literature for laser powder bed fusion of small and large parts involving the deposition of several thousands of layers. It is shown further that the analytical model can serve as a fast and practical design tool to estimate the through-thickness longitudinal residual stress distribution, which is along the length of the part, for part scale laser powder bed fusion using inexpensive computational resources and with appreciable accuracy. The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations. • An analytical model for residual stresses in 3D printed parts is extensively tested. • The model is validated with experimental data and numerically computed results. • Residual stresses in large 3D printed parts of 5 alloy compositions were examined. • Powder-specific process maps of peak tensile residual stresses are presented.

Axial loading mechanism analyses and evaluation methods of CCFT short columns with gap defects

The gap defect has proved to be a common quality issue in concrete-filled tubular (CFT) structures, which offers distinct unfavourable effects on their mechanics properties. To determine out the guidelines of gap defect affecting the axial loading performance of circular CFT (CCFT) short columns, this paper develops an array of refined numerical models of the axially-compressed CCFT short columns with spherical-cap gaps (CCFT-SG) and circumferential gaps (CCFT-CG), whose accuracy is verified by existing experiments. The typical axial force versus longitudinal displacement (N-Δ) curves, the contact stress, the longitudinal stress distribution and the failure modes are respectively given focus to reveal the intrinsic axial loading mechanism of the CCFT short columns, taking the existence of the gap defect into consideration. Based on these analyses, various design methods using confinement regionalization and circumferential expansion thoughts are proposed and adopted to evaluate the load bearing capacities of the axially-compressed CCFT-SG and CCFT-CG short columns. The results declare that the appearance of the gap defects dramatically weakens or delays the contact behaviour between the infilled concrete and the hollow tube, which accelerates the local bulging of the tube, reduces the longitudinal stress of the core concrete, and therefore the axial resistance of the CCFT short column is distinctly influenced. The design approaches delivered in this paper can assess the axial resistances of the CCFT short columns with gap defects accurately according to the test validation. The research may provide a theoretical basis and a reliable way for evaluating and treating the actual CFT structures with gap defects.

A theoretical approach to the residual stress assessment based on thermal field evaluation in laser beam welding

Residual stresses are one of the major issues in welded parts, since they could be detrimental to the integrity of components and structure. Their determination is rather complex and could be an arduous task, both when it is based on experimental methods and on numerical simulations. The proposed work presents a theoretical approach to the prediction of the longitudinal residual stress distribution, based on a parameterized multi-source model for thermal field simulation in laser welding previously introduced. Reference is made to the case of “keyhole” full penetration welding mode obtained by CO2 laser beam single pass on butt-positioned AISI 304L plates. The resolution of the thermal field allows the analytical calculation of the distribution of the longitudinal residual stresses in two ways: one makes use of a simplified formulation of the distribution well-known in the literature; a second modality makes use of a procedure for residual stress generation, which is based on a combined processing of thermal profiles and the corresponding heating–cooling cycles calculated in single points as their distance from the welding axis varies, and provides a complete characterization of the distribution of longitudinal residual tensile stresses. After the introduction of thermal field modeling, both the proposed residual stress calculation procedures are detailed, applied to the analyzed case, and validated, highlighting the differences in the approaches and results.

Experimental, numerical and design investigations on the performance of axially-loaded ECFT stub columns with spherical-cap gaps

Elliptical concrete-filled steel tubular (ECFT) columns have been increasingly used in engineering practice in recent years due to their aesthetic appeal together with structural advantages. The spherical-cap gaps were generally found in the actual CFT structures based on the latest survey. However, related literatures on the ECFT stub columns with spherical-cap gaps (ECFT-SG) under axial load are rarely reported. Thus, this paper aims to reveal the effects of gaps on the performance of axially-loaded ECFT stub columns. In total, ten axially-loaded ECFT-SG specimens were tested to explore the effects of gap ratio (χsg) and steel yield strength (fy) on the failure modes, axial fore (N) – longitudinal shortening (Δ), strain responses, strength and ductility indexes, etc. Following this, a series of numerical models using a modified equivalent concrete stress-strain relationship were established to expand the parametric scope and further study the steel-concrete interaction stresses and the concrete longitudinal stress distribution. Finally, two strength prediction methods of ECFT-SG stub columns were presented. The results indicated that the initial concrete gaps would weaken the confinement effect provided by steel tube, thus decrease the initial stiffness, ultimate strength and ductility of the columns. With the χsg increasing, the overall bending and inward buckling phenomena would be observed because of the uneven damage of infill concrete. The two design methods proposed herein are expected to provide a reference to evaluate the safety of the existing CFT columns with initial gap imperfection.