Yield Strength Of Steel Research Articles

Performance of eccentrically loaded ultra-high-strength concrete-filled Q770 steel tubular columns with varying slenderness ratios: Experimental and numerical investigations

This study conducts experimental and numerical investigations into the response of ultra-high-strength (UHS) concrete-filled ultra-high-strength steel tubular (UHSCFST) columns under eccentric loading, varying the slenderness ratio, to develop effective design guidelines for engineering applications. A series of eccentric compression tests were conducted on twelve UHSCFST columns with varying slenderness ratios to identify failure mechanisms and load-bearing characteristics. In the experimental program, critical influencing factors, including load eccentricity ratio, slenderness ratio, and UHS steel strength, were considered. Finite element models of eccentrically loaded UHSCFST columns were developed using ABAQUS and validated through a comparison of tested and simulated results to analyze load-sharing ratios and stress distribution for each column component. The findings indicated that UHSCFST column failure modes were characterized by compression-controlled and flexure-dominated damage under the combined effects of slenderness ratio and load eccentricity ratio. UHS concrete played a dominant role in bearing the eccentric load, and a judicious selection of UHS steel yield strength can improve column capacity and resistance. Additionally, these validated models were employed to conduct parametric studies that evaluated the effects of design and load parameters on the eccentric load capacity of UHSCFST columns. Design equations were developed based on tested and simulated results to predict the ultimate load capacity of UHSCFST column with varying slenderness ratios under eccentric loading conditions.

Flexural behaviour of optimised steel tubular beams partially filled with concrete

A partially concrete-filled steel tubular beam (PCFST) is proposed in this study to optimise the design and construction of the concrete-filled steel tubular beams (CFST). Concrete filling prevents the local buckling of the slender tubes. However, it is not needed in the beam’s tension zone. Therefore, in PCFST, concrete is filled in the compression zone while the tension zone is kept empty. In this paper, the flexural behaviour of the PCFST beam is studied experimentally and numerically. The ultimate moment resistance and flexural stiffness of PCFST are the same as CFST beams, while the weight reduction in PCFST is up to 60%. A finite element (FE) model is developed using ABAQUS software to investigate the effect of geometric and material properties of the PCFST beam on flexural behaviour. The FE model is validated by the present test results and the literature reports on CFST beams. Next, a parametric study is conducted to study the effect of concrete wall thickness in the web region, length-to-depth ratio, steel yield strength, concrete compressive strength, and beam shear span-to-depth ratio. The results show that the concrete filling is useful for slender steel tubular cross-sections rather than compact ones. A higher grade of concrete increases the beam ductility, while high-strength steel reduces the ductility. The results also show that the PCFST beam is more suitable for beam lengths where flexure is predominant than shear. Further, a flexural capacity equation is proposed for PCFST beams, and it agrees well with the test and numerical results. The reliability of the proposed equation is checked as per the recommendation in EN:1994–2004 and AISC 360–2016 code provisions.

Dual nanoprecipitation and nanoscale chemical heterogeneity in a secondary hardening steel for ultrahigh strength and large uniform elongation

Nanoprecipitates and nanoscale retained austenite (RA) with suitable stability play crucial roles in determining the yield strength (YS) and ductility of ultrahigh strength steels (UHSSs). However, owing to the kinetics incompatibility between nanoprecipitation and austenite reversion, it is highly challenging to simultaneously introduce high-density nanoprecipitates and optimized RA in UHSSs. In this work, through the combination of austenite reversion treatment (ART) and subsequent flash austenitizing (FA), nanoscale chemical heterogeneity was successfully introduced into a low-cost UHSS prior to the aging process. This chemical heterogeneity involved the enrichment of Mn and Ni in the austenite phase. The resulting UHSS exhibited dual-nanoprecipitation of Ni(Al,Mn) and (Mo,Cr)2C and nanoscale austenite stabilized via Mn and Ni enrichment. The hard martensitic matrix strengthened by high-density dual-nanoprecipitates constrains the plastic deformation of soft RA with a relatively low fraction of ∼15 %, and the presence of relatively stable nanoscale RA with adequate Mn and Ni enrichment leads to a marginal loss in YS but keeps a persistent transformation-induced plasticity (TRIP) effect. As a result, the newly-developed UHSS exhibits an ultrahigh YS of ∼ 1.7 GPa, an ultimate tensile strength (UTS) of ∼1.8 GPa, a large uniform elongation (UE) of ∼8.5 %, and a total elongation (TE) of ∼13 %. The strategy of presetting chemical heterogeneity to introduce proper metastable phases before aging can be extended to other UHSSs and precipitation-hardened alloys.

Explainable machine learning-aided efficient prediction model and software tool for bond strength of concrete with corroded reinforcement

The bond strength between concrete and reinforcement is crucial for the composite action and serviceability of reinforced concrete (RC) structures. However, it is vulnerable to deterioration from the corrosion of reinforcement bars, especially in marine structures. Thus, a precise and reliable model for the bond strength in corrosive environments is necessary to evaluate the serviceability and structural performance of corroded RC members. This study employs explainable machine learning (ML) techniques to assess the bond strength between concrete and corroded bars. Eight ML models are developed to establish the best predictive model for bond behavior, considering seven input parameters: corrosion level (CL), steel yield strength, compressive strength of concrete, concrete cover-to-bar diameter ratio, bar diameter-to-bonded length ratio, reinforcement type, and test type. The super learner (SL) model, integrating three ML models, outperforms other models and analytical methods with a large R2 value (98% on the test set) and minimal statistical errors. The SHapley Additive exPlanation (SHAP) technique identifies CL as the most influential parameter on bond strength, while the reinforcement and test types have the least effect. Finally, a user-friendly graphical user interface (GUI) tool is established to facilitate the practical implementation of the developed model and support accurate bond strength prediction in concrete with steel reinforcement under corrosive environments.

Study on impact toughness of TMCP and quenched and tempered high strength steels

In this study, the effect of steel rolling technique, temperature, yield strength and welding heat input on the impact toughness of high-strength steels is studied. The impact toughness of five kinds of high strength steels with yield strength of 550 MPa, 690 MPa and 890 MPa are experimentally studied. The standard Charpy V-notch test is carried out and the absorbed energy AKV of the test specimens is obtained. The test results show that the impact toughness of QT550 high-strength steel is not sensitive to temperature and it also has good impact performance at low temperature. For other high strength steels, with increase of steel strength, the impact toughness is severely degraded with decreasing temperature. For the effect of rolling technique on impact toughness, the QT type high-strength steel generally follows the law that the impact toughness deteriorates with the increase of the yield strength. QT process can produce better impact resistance than TMCP process for 690 grade steel. The effect of temperature on the impact toughness of WM is intensified at high heat input. The impact toughness of the base material (BM), heat-affected zone (HAZ) and weld metal (WM) deteriorates with the rise of the yield strength. QT550 and QT690 show different impact characteristics for HAZ and WM. The former HAZ has better impact performance under high heat input while WM is better under low heat input; both HAZ and WM of QT690 show higher impact toughness under low heat input.

UPAYA PERBAIKAN SIFAT MEKANIK BAJA PLAT JOIN G 3131 SPHC MELALUI SIMULASI PROSES INTERCRITICAL ANNEALING DI INDUSTRI KONSTRUKSI BAJA

Improvement of the mechanical properties of G3131 SPHC equivalent to JIS G 3101 SS330 plate joint steel through intercritical annealing simulations has been carried out. The JIS G 3131 grade SPHC steel was gradually heated by intercritical annealing at temperatures of 750–850 oC for holding times of 1–15 minutes. After intercritical annealing treatment, the tensile strength and yield strength of steel increased compared to non-treatment samples. The average tensile strength obtained was 573 MPa with an increase of 76.85% compared to the tensile strength before the intercritical annealing process. Meanwhile, the yield strength of steel increased by 60% to 421 MPa. Increasing the annealing temperature and holding time will promote the formation of the martensite phase, as well as enlarge the austenite and ferrite grains. Optimal heating variable obtained at a temperature of 750 ℃ with a holding time of 15 minutes. Using these variables produced a tensile strength of 625 MPa and a yield strength of 434 MPa with an elongation of 23% which is standardly included in JIS G 3101 SS400.At the optimal value, the grain growth kinetic of K and n values were 0.280466778 and 0.6905, respectively, with an activation energy (Q) of 12.4268517 J/mol.

Research on the Residual Bearing Capacity of Square Hollow Concrete-filled Steel Tube After Fire

In order to study the change of the residual bearing capacity of square hollow concrete-filled steel tube after fire, the finite element analysis software ABAQUS was used to establish the finite element model of square hollow concrete-filled steel tube under the ISO-834 standard fire heating condition, and the temperature distribution and deformation of the model were simulated and analyzed. Based on that, the influence of parameters such as the strength grade of concrete, the strength grade of steel, the calculated length of member and the hollow ratio of section on the residual bearing capacity of member after fire is simulated and analyzed. The results show that the temperature distribution of the component is mainly affected by the section size, concrete strength grade and steel yield strength, but is less affected by the calculated length. The temperature of the inner concrete and the inner steel tube decreases with the increase of the thickness of the member. The strength of steel and the size of section have more influence on the stress characteristics of the member after fire, but the strength grade of concrete and the length of the member have less influence. Among them, the increase of steel strength, concrete strength will enhance the fire-resistant limits of components. When the hollow ratio of the section increases, the fire resistance limit of the component increases first and then decreases. The increase of the calculated length will reduce the fire resistance limit of the member. The residual bearing capacity of the component decreases with the increase of fire time.

Derivation of stainless steel material factors for European and U.S. design standards

Modern structural design standards are based on the Limit State Design (LSD) philosophy, also known as Load and Resistance Factor Design (LRFD), which involves the use of resistance functions with accompanying safety factors that are based on a statistical evaluation of relevant experimental data, carried out within the framework of a probabilistic reliability theory. This paper presents the derivation of material factors for the yield strength and ultimate tensile strength of austenitic, duplex and ferritic stainless steels, and their associated coefficients of variation (COV) for use in evaluating the safety factors for the European design code EN 1993-1-4 and the American design codes Specification for Structural Stainless Steel Buildings (ANSI/AISC 370–21) and Specification for the Design of Cold-Formed Stainless Steel Structural Members (ASCE/SEI 8–22). Separate material factors and associated COV values are required for the U.S. and European design codes due to the different minimum specified strength values that are given in the respective product standards. The material factors were derived by analysing a large amount of material data provided by different stainless steel producers, which encompassed a wide range of stainless steels and material thicknesses.

In-situ micro-asperity investigation of real contact area formation during sliding with the effects of roughness and normal load considered

Real contact area is a challenging phenomenon in tribology, where despite established theoretical models, detailed experimental studies are still lacking. This work is focused on the evolution of the real contact area of multi-asperity steel contacts during sliding, by using sub-micron characterisation of entire multi-asperity contact area and simultaneous measurement of the friction force. Steel-sapphire contact was monitored by using an in-situ optical system in real time during 5 mm of unidirectional sliding in surface roughness range Ra = 0.1–1.0 µm and normal loads up to the nominal contact pressure equal to steel yield strength (Y). The results showed that the initial real contact area caused by static loading increased during sliding. At low nominal contact pressure of 0.3Y, the increase in real contact area was the largest: for Ra = 0.1 µm it went from 9.5% of the nominal area under static conditions to 15.0% after sliding, a 56% relative increase, and for Ra = 1.0 µm it went from 5.0% to 11.5% after sliding, a 106% increase. The increase in real contact area was smaller at higher nominal contact pressures of 0.6Y and 1.0Y. At 1.0Y for Ra = 0.1 µm the real contact area went from 18.0% to 21.8% after sliding and for Ra = 1.0 µm it went from 9.4% to 12.9% after sliding. The coefficient of friction increased with roughness at the lowest nominal contact pressure 0.3Y (for Ra = 0.1 µm it was 0.24 and for Ra = 1.0 µm it was 0.29) but became independent of roughness at higher contact pressures (on average 0.18).

Static behavior of multi-planar CFST chord-CHS brace TT joints

The static performance of the multi-planar concrete-filled steel tubular (CFST) chord-circular hollow section (CHS) brace TT (CFST-TT) joint is investigated using theoretical and finite element analysis (FEA). The joint ultimate bearing capacity is the minimum strength of each member to ensure that the joint will not fail under any loads. Accordingly, the strength calculation formulas for joints are proposed based on the failure mechanism. FEA models verified by experiments were established to obtain the joint bearing capacity and failure modes, and further analysis was done to find the effects of geometrical parameters, material strength, and the axial compression ratio. The results show that the joint bearing capacity increased with the increase of brace-to-chord diameter ratio (β) and steel yield strength of the chord (fy) but decreased with the increase of the chord diameter-to-thickness ratio (γ). However, the concrete compressive strength (fcu), the brace-to-chord thickness ratio (τ), the angle between two braces (Ф), and the axial compression ratio (n) almost have no effect on the joint bearing capacity. The proposed ultimate bearing capacity formula is validated using FEA. The optimized formula is proposed to simplify the theoretical calculation formula and make the results more consistent with the FEA results.

Effect of Nanostructuring on Operational Properties of 316LVM Steel

In this study, high-pressure torsion (HPT) was used to process austenitic 316LVM stainless steel at 20 °C and 400 °C. The effects of HPT on the microstructure, mechanical, and functional properties of the steel were investigated. By applying both HPT modes on the 316LVM steel, a nanocrystalline state with an average size of the structural elements of ~46–50 nm was achieved. The density of the dislocations and twins present in the austenite phase varied depending on the specific HPT conditions. Despite achieving a similar structural state after HPT, the deformation temperatures used has different effects on the mechanical and functional properties of the steel. After HPT at 20 °C, the yield strength of the 316L steel increased by more than nine times up to 1890 MPa, and the fatigue limit by more than two times up to 550 MPa, when compared to its coarse-grained counter-parts. After HPT at 20 °C, the 316LVM steel exhibited better ductility, higher low-cycle fatigue resistance, greater resistance to corrosion, and improved in vitro biocompatibility compared to processing at 400 °C. The reasons for the deterioration of the properties after HPT at 400 °C are discussed in the article.

Flexural performance of rectangular CFST composite T-beams: Experimental, numerical, and theoretical investigation

Steel-concrete composite beams find extensive application in bridge construction, offering adaptability to complex terrains and structural advantages. Nevertheless, a persistent challenge lies in local instability, especially in steel beams with large aspect ratios. This study proposes stirrup-confined concrete-filled steel tube (CFST) composite beams as a solution to enhance structural performance by mitigating local instability. The research comprises comparative tests, numerical simulations, and theoretical examinations of rectangular CFST composite beams. Results demonstrate a significant improvement, with a 40% increase in flexural stiffness and a 10% increase in ultimate bearing capacity compared to traditional composite beams. Stirrup confinement effectively limits cross-section slip between the steel tube and infilled concrete, resulting in slip measurements of 0.72 mm at the end of loading. Examination of aspect ratios reveals substantial enhancements, showing a 65.6% increase in flexural stiffness and a 54.7% increase in ultimate bearing capacity as aspect ratios increase. Concrete strength grade exhibits minor effects, with slight improvements as the grade increases. Steel yield strength significantly influences ultimate bearing capacity, with a maximum 24.4% increase in higher-strength steel. Moreover, the steel content ratio enhances both flexural stiffness (up to 40.2%) and ultimate bearing capacity (up to 34.6%) with an increased steel ratio. Increased concrete slab thickness leads to improvements of up to 18.3% in flexural stiffness and up to 10.1% in ultimate bearing capacity. Formulas for predicting the flexural stiffness and bearing capacity of rectangular CFST composite T-beams are developed, offering practical guidance for optimizing their performance in structural engineering applications.

Experimental investigation on the cold-forming effect of high strength cold-formed steel sections

Many researches were carried out on the cold-forming effect of cold-formed steel sections while research on that of high strength cold-formed steel sections was quite few. Thus, an experimental investigation on the material property and residual stress of high strength cold-formed steel sections was carried out and the effect of residual stress on the overall stability bearing capacity was studied. It was found that: (1) the increase of yield strength of high strength cold-formed steel was similar to that of Q235 and Q345 cold-formed steel; (2) the residual stress at corner parts was much higher than that at flat parts and the bending residual stress of high strength cold-formed steel was much lower than that of Q235 and Q345 cold-formed steel; (3) residual stress would lead to a decline of the overall stability bearing capacity of axially loaded high strength cold-formed C-shaped steel sections and the effect became lower with the increase of strength grade.

Behavior and design of concrete filled stainless steel tubular columns under concentric and eccentric compressive loading

Concrete Filled Stainless Steel Tubular (CFSST) column is a novel type of composite columns that features excellent structural performance, corrosion resistance as well as aesthetic appearance. Owing to the differential mechanical properties between stainless steel and carbon steel, extending the current design codes of conventional CFST columns to CFSST columns may cause unreliable predictions. To this end, this paper summarizes the current state-of-art of CFSST columns and compiles the database of CFSST columns subjected to concentric compressive loading and eccentric compressive loading. Based on the analysis of current studies, the applicability of current international design codes is comprehensively evaluated, and the numerical simulation is also performed through three-dimensional Finite Element (FE) modeling and two-dimensional Fiber Section (FS) modeling technique, where the concrete confinement effect is properly incorporated. Parametric study is then conducted using the validated FS model to investigate the influence of concrete compressive strength, steel yield strength and section slenderness ratio on load-carrying capacity. Finally, a new approach is proposed to construct the axial force-bending moment interaction diagram of CFSST columns, which is simple to use and generates enhanced prediction accuracy as compared with the current design method.

Design of Can Crusher

Abstract: Present study has focused on the design of a domestic aluminum can crusher this will be used to shred empty beverage cans and recycle them back into the industry. It promote sustainability in the beverage production sector. The Young's modulus, density, yield strength, and Poisson's ratio of steel and aluminum, among other parameters, were taken into consideration during the design computation of the crusher. Catia was used to model each individual component as well as the entire machine assembly.

Experimental investigation of axially loaded circular ultra-high performance concrete with coarse aggregate (CA-UHPC) filled steel tube slender columns

This paper presents an experimental investigation on circular ultra-high performance concrete with coarse aggregate (CA-UHPC) filled steel tube (CA-UHPCFST) slender column subjected to axial compression. A total of 42 specimens were manufactured and tested to determine the effects of CA-UHPC strength, steel tube thickness, steel strength, and length-to-diameter ratio on axial compressive behavior of circular CA-UHPCFST slender columns. The test results show that elastoplastic instability failure with local buckling in the compression region is observed for intermediate columns, while overall buckling failure is occurred for slender columns. The inclusion of steel fibers significantly alleviates the tensile cracking and compressive crushing of CA-UHPC core, which in turn improves the ultimate strength and ductility of CA-UHPCFST slender columns. The ultimate bearing capacity and ductility index decrease remarkably with an increase in length-to-diameter ratio, while increase with steel yield strength and tube thickness. The interaction between steel tube and CA-UHPC core decreases as the length-to-diameter ratio increases, which mainly exists in compression zone but is weak or even nonexistent in tension zone. Finally, the feasibility of current design guidelines concerning the concrete-filled steel tubes for calculating the stability bearing capacity of circular CA-UHPCFST slender columns is evaluated, and a simplified model is proposed to estimate the stability carrying capacity. The simplified model demonstrates good accuracy in predicting the ultimate carrying capacity of axially loaded circular CA-UHPCFST slender columns.

Calculation method for local–global interaction buckling capacity of stainless steel C-columns

In this paper, based on the completed experimental research, the C-section stainless steel column was simulated in ABAQUS, and the FEM results were compared with the test results to verify the accuracy of the FE model. On this basis, the FE model was used to carry out a parametric analysis of the local–global interaction (L-G) buckling capacity of the C-section stainless steel column, and the effects of the initial imperfection distribution mode, the mechanical properties of the material, and the improvement of the material strength in the corner region were investigated. When the initial geometric imperfection distribution mode is local buckling or L-G buckling, the change of imperfection shape has less effect on the occurrence of L-G buckling and the ultimate capacity of the member. Within a certain range, the stainless steel hardening coefficient and the increase strength of corner region on the L-G buckling capacity of stainless steel columns is small. The nominal yield strength of stainless steel has a more significant effect on the L-G buckling capacity. Finally, based on the parametric analysis results and the direct strength method, the calculation formula for the local–global interaction buckling capacity of stainless steel C-columns under axial compression is proposed, and the accuracy of the calculation results were verified by comparing with the test results.

Enhancing yield strength and ductility of Fe-Mn-C-xAl (x = 0, 3) high manganese steel by cryogenic rolling

In this study, cryogenic rolling was employed to introduce nanotwins into Fe-Mn-C-xAl (x = 0, 3) high manganese steel in order to enhance its yield strength. The yield strength of 0Al and 3Al steels were improved after cryogenic rolling, and the yield strength reached 1079 MPa and 961 MPa, respectively. Furthermore, excellent ductility was achieved after tempering without any reduction in strength, and the ductility of 0Al and 3Al steels were 23.6 % and 14.9 %, respectively. The effect of Al addition on the mechanical properties was investigated and the strengthening contribution mechanism is discussed.

Deep learning classifier for life cycle optimization of steel–concrete composite bridges

The ability to conduct life cycle analyses of complex structures is vitally important for environmental and social considerations. Incorporating the life cycle into structural design optimization results in extended computational durations, underscoring the need for an innovative solution. This paper introduces a methodology leveraging deep learning to hasten structural constraint computations in an optimization context, considering the structure’s life cycle. Using a composite bridge composed of concrete and steel as a case study, the research delves into hyperparameter fine-tuning to craft a robust model that accelerates calculations. The optimal deep learning model is then integrated with three metaheuristics: the Old Bachelor Acceptance with a Mutation Operator (OBAMO), the Cuckoo Search (CS), and the Sine Cosine Algorithms (SCA). Results indicate a potential 50-fold increase in computational speed using the deep learning model in certain scenarios. A comprehensive comparison reveals economic feasibility, environmental ramifications, and social life cycle assessments, with an augmented steel yield strength observed in optimal design solutions for both environmental and social objective functions, highlighting the benefits of meshing deep learning with civil engineering design optimization.

Quantifying the Dislocation Cell Contribution to the Yield Strength of 316L Steel

Quantifying the Dislocation Cell Contribution to the Yield Strength of 316L Steel