Shear Extrusion Research Articles

Effect of microstructure evolution on the corrosion behavior of extrusion-shearing Mg-3Zn-XCa-0.6Zr alloys

In order to promote the application of new biomedical materials Mg-Zn-Ca-Zr alloy, the Mg-3Zn-xCa-0.6Zr (x = 0.6, 1.2, 1.8 wt%) alloys were fabricated by an extrusion shearing (ES) process. The effect of secondary phase precipitation, grain size and texture on the corrosion resistance of Mg-3Zn-xCa-0.6Zr (wt%) in Hank's solution were studied using electrochemical, immersion and electron back-scattering diffraction (EBSD) tests, and the corrosion mechanism of ES alloys was discussed. With increasing the addition of Ca element, the grain size of alloys first decreased and then increased, and the constitution of second phase was transformed from MgZn and Ca2Mg6Zn3 phases to Mg2Ca and Ca2Mg6Zn3 phases, the texture changed from a bimodal texture intensity with stronger basal texture to a DRX texture intensity with a weaker texture. Mg-3Zn-0.6Ca-0.6Zr alloy showed the lowest corrosion rate of ∼0.3140 ± 0.0642 mm/y. The excellent corrosion resistance of Mg-3Zn-0.6Ca-0.6Zr alloy could be attributed to the High-potential dispersion distribution of MgZn and Ca2Mg6Zn3 phases and the strong basal texture. As well as more dense corrosion product films formed after alloying, effectively hindering local corrosion. In contrast, corrosion product films formed by the fine grain structure of Mg-3Zn-1.2Ca-0.6Zr alloy were not sufficient to resist the galvanic coupling corrosion between the Mg2Ca phase and the Ca2Mg6Zn3 phase, which caused the decreasing of its corrosion resistance.

Achieving strength-ductility balance in AZ31-WE43 Mg alloys by symmetric extrusion-shear process at various temperatures

The development of composites that simultaneously improve strength and plasticity is a challenging task, especially in Mg alloys. The focus of this study is to create a novel multiscale gradient structure (GS) in Mg laminates to exhibit optimal strength-plasticity synergies through a temperature-controlled extrusion shear (TCES) and extrusion composite process with preset grain sizes. Initially, the gradient structure is formed by a short extrusion process, leading to an increase in the average grain size of the elongated coarse grains from the middle layer of the equiaxed fine grain zone to the elongated coarse grain surface layer. The resulting gradient structure improves the material synergy. The microstructure evolution mechanism of the alloy during symmetric plastic deformation was analyzed. The initial grains underwent DDRX, CDRX, and shear deformation-induced dynamic recrystallization (SDDRX) during the RZ extrusion stage, the grains were significantly refined, and the basal texture intensity was significantly weakened during the SD extrusion stage. The effect of extrusion temperature (400 °C, 450 °C, 500 °C) on the alloys in the forming zone after ES extrusion was further investigated. Tensile tests on Mg laminates prepared by the extrusion method showed that the ultimate tensile strength (UTS) of the samples prepared at 450 °C was 265 MPa and the elongation (EL) was 23.8 %. The significant improvement in the yield tensile strength (YTS) of the composite Mg alloys post-ES processing is primarily attributed to the fine-grained (FG) interior, while the increase in elongation is due to the coarse-grained (CG) exterior. This study presents a novel approach to enhancing the mechanical properties of Mg alloys, offering a promising direction for the development of advanced materials with superior strength and ductility.

Ultrasonic vibration-assisted tube extrusion shear expansion (UVaTESE): A novel process to manipulate the texture of AZ31 magnesium alloy

AZ31 magnesium (Mg) alloy prepared via the extrusion process forms an immensely strong {0001} basal texture, therefore there is a necessity to improve the existing extrusion process to achieve a weakening of the {0001} basal texture of the AZ31 Mg alloy. In this study, a novel process called UVaTESE is proposed. The Mg alloy texture and slip system activation at four ultrasonic vibration (UV) frequencies have been simulated via ABAQUS-VUMAT and VPSC, individually. The simulation results indicate that UV is capable of diffusing the {0001} basal texture of the Mg alloy along the extrusion direction (ED) and transverse direction (TD) and significantly improves the activation of pyramidal slip <c+a>. The simulations are verified experimentally, and the {0001} basal texture of AZ31 Mg alloy has the identical tendency to disperse along ED and TD. Prismatic slip <a> and pyramidal slip <c+a> jointly lead to diffusion of the grain basal texture along the TD, while grains with basal texture diffused along the ED are controlled by both basal slip <a> and pyramidal slip <c+a>. UV has a positive effect on the grain refinement as well as on the homogeneity of AZ31 Mg alloy. The proportion of dynamic recrystallization (DRX) of AZ31 Mg alloy is proportional to the frequency of UV, and it is noteworthy that the mechanism of DRX behavior is not affected by UV. This novel process provides a fundamentally innovative approach to the preparation of Mg alloys and magnesium-aluminum (Mg-Al) composite tubes via extrusion.

Enhanced mechanical behavior and texture development of Al/Al2O3 composites produced by spark plasma sintering (SPS) and vacuum hot pressing (VHP) followed by simple shear extrusion (SSE)

Green compacts of Al-3vol% Al2O3 composites were produced by powder metallurgy (PM) and subsequently processed by spark plasma sintering (SPS) and vacuum hot pressing (VHP). The manufactured samples were then processed by the simple shear extrusion (SSE) process. Three SSE dies with the distortion angles (α) of 8°, 10° and 22.5° were used in this study. The SPS-ed/SSE-ed specimens for α = 10° were successfully deformed up to sixteen passes, while the VHP-ed/SSE-ed samples failed after six passes. In addition, the SPS-ed sample for α = 22.5° only underwent one pass of SSE. The SPS-ed/SSE-ed composites resulted in the highest shear punch test (SPT) load, modified porosity amount and the best reinforcement redistribution, as compared to the vacuum sintering and stir-casting manufacturing methods, which was confirmed by microstructure evaluation and porosity measurements. The crystallographic texture of the SPS-ed/SSE-ed composites for α = 10° was investigated in the sixteenth pass using the X-ray method. The results of texture development showed the very low intensity of shear and cube texture with {100} <011> and {001} <100> components, subsequently.

Investigation of a newly developed shear built-in valve type MR damper with high damping: Theories and experiments

Magnetorheological (MR) dampers are widely used as semi-active energy-dissipation devices in structural vibration control. Traditional MR dampers, particularly their working mode, often struggle to achieve a high damping force output and sometimes fail to meet the needs of practical engineering. Therefore, it is necessary to study MR dampers that can provide a high damping force. This study proposes an MR damper that combines a built-in shear valve with various working modes of shear extrusion. The damper generates a higher damping force by applying a current to the coils at different positions and altering its working mode. First, the ANSYS Maxwell software simulates the internal magnetic circuit of the damper to assess whether the magnetic field intensity distribution and circuit direction meet the design requirements. Analysis revealed that the internal magnetic circuit distribution was reasonable and satisfied the operating requirements of the damper. Furthermore, the mechanical models of the two working modes were derived based on the Bingham and double-viscous models. Finally, the accuracies of the mechanical models were verified experimentally. The experimental results showed that the simulation values closely matched the experimental values under all the working conditions. Therefore, the proposed mechanical models are reasonable, and can provide significant reference values for practical engineering applications.

Mechanochemical Recycling of Flexible Polyurethane Foam Scraps for Quantitative Replacement of Polyol Using Wedge-Block-Reinforced Extruder.

Recycling flexible polyurethane foam (F-PUF) scraps is difficult due to the material's high cross-linking structure. In this work, a wedge-block-reinforced extruder with a considerable enhanced shear extrusion and stretching area between the rotating screw and the stationary wedge blocks was utilized to recycle F-PUF scraps into powder containing surface-active hydroxyl groups. The powder was then utilized for the quantitative replacement of polyol in the foaming process. Characterizations showed that the continuous shear extrusion and stretching during the extrusion process reduced the volume mean diameter (VMD) of the F-PUF powder obtained by extruding it three times at room temperature to reach 54 μm. The -OH number (OHN) of the powder prepared by extruding it three times reached 19.51 mgKOH/g due to the mechanochemical effect of the powdering method. The F-PUF containing recycled powder used to quantitively replace 10 wt.% polyol was similar in microstructure and chemical structure to the original F-PUF, with a compression set of 2%, indentation load deflection of 21.3 lbf, resilience of 43.4%, air permeability of 815.7 L/m2·s, tensile strength of 73.0 Kpa, and tear strength of 2.3 N/cm, indicating that the recycling method has potential for industrial applications.

High internal phase emulsions gel ink for direct-ink-writing 3D printing of liquid metal

3D printing of liquid metal remains a big challenge due to its low viscosity and large surface tension. In this study, we use Carbopol hydrogel and liquid gallium-indium alloy to prepare a liquid metal high internal phase emulsion gel ink, which can be used for direct-ink-writing 3D printing. The high volume fraction (up to 82.5%) of the liquid metal dispersed phase gives the ink excellent elastic properties, while the Carbopol hydrogel, as the continuous phase, provides lubrication for the liquid metal droplets, ensuring smooth flow of the ink during shear extrusion. These enable high-resolution and shape-stable 3D printing of three-dimensional structures. Moreover, the liquid metal droplets exhibit an electrocapillary phenomenon in the Carbopol hydrogel, which allows for demulsification by an electric field and enables electrical connectivity between droplets. We have also achieved the printing of ink on flexible, non-planar structures, and demonstrated the potential for alternating printing with various materials.

Nano-cutting mechanism of ion implantation-modified SiC: reducing subsurface damage expansion and abrasive wear

This study utilized ion implantation to modify the material properties of silicon carbide (SiC) to mitigate subsurface damage during SiC machining. The paper analyzed the mechanism of hydrogen ion implantation on the machining performance of SiC at the atomic scale. A molecular dynamics model of nanoscale cutting of an ion-implanted SiC workpiece using a non-rigid regular tetrakaidecahedral diamond abrasive grain was established. The study investigated the effects of ion implantation on crystal structure phase transformation, dislocation nucleation, and defect structure evolution. Results showed ion implantation modification decreased the extension depth of amorphous structures in the subsurface layer, thereby enhancing the surface and subsurface integrity of the SiC workpiece. Additionally, dislocation extension length and volume within the lattice structure were lower in the ion-implanted workpiece compared to non-implanted ones. Phase transformation, compressive pressure, and cutting stress of the lattice in the shear region per unit volume were lower in the ion-implanted workpiece than the non-implanted one. Taking the diamond abrasive grain as the research subject, the mechanism of grain wear under ion implantation was explored. Grain expansion, compression, and atomic volumetric strain wear rate were higher in the non-implanted workpiece versus implanted ones. Under shear extrusion of the SiC workpiece, dangling bonds of atoms in the diamond grain were unstable, resulting in graphitization of the diamond structure at elevated temperatures. This study established a solid theoretical and practical foundation for realizing non-destructive machining at the atomic scale, encompassing both theoretical principles and practical applications.

Disturbance range characterization and reinforcement design method of concealed bedding slope

The concealed bedding slopes exhibit sudden and extensive failure characteristics, harboring significant safety hazards. It is crucial to employ rapid and accurate methods to determine excavation disturbance ranges and reinforcement forces to prevent such slope disasters. This paper first analyzes the failure characteristics of slope excavation to reveal the mechanism of slope failure. Secondly, a novel method was proposed to calculate excavation disturbance ranges and solve for active reinforcement forces. Thirdly, the rationality of the method was validated through numerical simulation experiments. Finally, the method was applied to engineering. The results are as follows:(1) Excavation induces plastic shear failure of structural planes first, and the strength of the structural plane will be reduced, resulting in extrusion shear deformation of the rock mass at the foot of the slope under greater unidirectional load along the structural plane, forming a shear sliding surface. (2) From both strength and deformation perspectives, a method for calculating disturbance ranges in excavated slopes is proposed. This method determines key indicators for analyzing two disturbance range factors: ultimate height and disturbance thickness. The disturbance range is divided into shear plastic zones and traction sliding zones. (3) An active reinforcement design method is proposed considering the timing, scope, and force of reinforcement. The disturbance thickness is used to determine the reinforcement range, while the ultimate height is used to determine the timing of reinforcement. Active reinforcement forces are calculated based on the equilibrium of forces and deformation amounts. (4) A comparison with the Finite Element Method (FEM) shows that during excavation, the disturbance ranges and reinforcement forces calculated using this method are slightly larger than those obtained from the FEM. The calculations are fast, and as the excavation height approaches the limit slope height, the disturbance thickness and horizontal deformations closely match the FEM results, ensuring safety. It can provide monitoring, early warning and reinforcement guidance for bedding slope construction.

The deformation behavior of aluminum alloy in a novel severe plastic deformation process known as combined SSE-FE process

In this study, a novel method for severe plastic deformation (SPD) was introduced, entitled as Combined SSE-FE (CSSE-FE). The process was investigated experimentally and numerically on AA1050 alloy. After this process, due to the unique design of the die channel, the sample significantly fills the die outlet channel. Also, the CSSE-FE process can produce large strains without repeating the cycle. Therefore, this parameter was increased by around 53.16 % in comparison to simple shear extrusion (SSE) process after the first pass. Also, microhardness was increased by about 87.93 % in comparison to annealed sample.

3D printing of a photo-curable hydrogel to engineer mechanically robust porous structure for ion capture or sustained potassium ferrate(VI) release for water treatment

Contaminated water and scarcity of clean water are becoming progressively serious environmental concerns. Removal of hazardous pollutants from wastewater is vital and urgently needed attention for the protection of pure water resources. To tackle the aforementioned challenges, macroporous structures have great potential to be used in the treatment of heavy metal ions to improve the adsorption efficiency and sustainability of wastewater treatment methodologies. In this context, additive manufacturing technologies have gained considerable attention because of their ability to construct intricate macroporous shapes with multifunctionalities using diverse materials. Here, we used a photocrosslinking graft copolymerization of polyvinyl alcohol/acrylic acid-based ink using UV irradiation in the presence of Norrish type II photosensitizer through a hot-melt extrusion-type 3D printer to improve the printing quality of crosslinked ink. The photocured inks offered strong shear-thinning behavior that allowed layer-by-layer deposition to generate well-defined 3D structures, while having sufficiently high viscoelasticity to retain the shape after printing process. With an adequate viscosity at the higher extrusion shearing forces, the 3D printed structures could create multifaceted self-supporting scaffolds with an internal lattice structure that possesses high level of porosity. The hierarchically porous structure of 3D objects showed a recoverable structure yet robust matrix, offering more specific surface area, capable of effectively removing heavy metal ions from water with fast-responsiveness and a high capacity. The ferrate(VI)-contained 3D capsule-like object was also detected to be efficient regarding chemical oxygen demand reduction and decolorization of real wastewater. Such 3D-printed hierarchical macroporous objects can offer great prospects in the treatment of water and wastewater purification applications.

Unveiling the microstructure evolution and deformation mechanisms of micro-alloying Mg-1.5Zn-0.5Zr-0.5Sr alloy via extrusion-shearing

Obtaining high strength without sacrificing ductility in Mg alloys is of great importance. However, the hexagonal close-packed crystal structure critically limits the deformation of Mg alloys. In this work, novel Mg-1.5Zn-0.5Zr-0.5Sr (wt.%) alloys were fabricated through homogenization, direct extrusion (DE), and extrusion-shearing (ES) processes. The effects of three different processes on microstructures, texture, and mechanical properties were thoroughly investigated. The results show that the average grain size of the alloy was greatly refined after hot extrusion. The alloy after the DE process exhibited a typical bimodal microstructure with dynamic recrystallized (DRXed) grains showing a strong <101‾0 > fiber texture parallel to extrusion direction (ED), while the small-sized unDRXed grains showed relatively weak basal texture. In addition, the strength was significantly improved, with the value of yield strength (YS) reaching ∼229 MPa and ultimate tensile strength (UTS) reaching ∼262 MPa. This is mainly attributed to grain boundary strengthening and dislocation strengthening. Compared to the DE-processed alloy, the basal texture intensity was significantly decreased and non-basal slip was activated after the ES process, which indicates that the shearing deformation during ES could improve the ductility, with the fracture elongation (FE) increased from ∼13.9 % to ∼21.4 %. This work aims to unveil the deformation mechanisms in Mg-1.5Zn-0.5Zr-0.5Sr alloy and provides an efficient way for preparing micro-alloying Mg alloys with low cost and significant improvement of comprehensive properties.

Unprecedented electrical performance of friction-extruded copper-graphene composites

Copper-graphene composites show remarkable electrical performance surpassing traditional copper conductors albeit at a micron scale; there are several challenges in demonstrating similar performance at the bulk scale. In this study, we used shear assisted processing and extrusion (ShAPE) to synthesize macro-scale copper-graphene composites with a simultaneously lower temperature coefficient of resistance (TCR) and improved electrical conductivity over copper-only samples. We showed that the addition of 18 ppm of graphene decreased the TCR of C11000 alloy by nearly 11 %. A suite of characterization tools involving scanning and transmission electron microscopy along with atom probe tomography were used to characterize the grain size, crystallographic orientation, structure, and composition of copper grains and graphene additives in the feedstock and processed samples. We posit that the shear extrusion process may have transformed some of the feedstock graphene additives into higher defect-density agglomerates while retaining the structure of others as mono-to-tri-layer flakes with lower defect density. The combination of these additives with heterogeneous structures may have been responsible for the simultaneous decrease in TCR and enhanced electrical conductivity of the copper-graphene ShAPE composites.

A novel continues multi-shear extrusion process on the microstructure and mechanical property evolution of AZ31 magnesium alloys

This study presents a novel technology in the fabrication of AZ31 Mg alloy sheets using continuous shear extrusion (CSE) with multiple shear platforms at 340 °C. Compared with the conventional extrusion (CE), an asymmetric shear deformation was introduced so that the basal texture deflects towards to extrusion direction. Through finite element simulation, it was found that the differences in flow velocity and strain distributions along the thickness direction can be achieved by introducing the shear strain through CSE technology. Finer grains and more uniform microstructure were obtained in CSEed Mg samples compared to conventional extrusion. The average grain size decreased from 6.33 μm in CE samples to 3.94 μm in CSE samples, and 3.39 μm in CSE-II samples. The continuous asymmetric shear force also led to the basal plane inclining approximately 15° towards the extrusion direction, leading to a weakening of basal texture intensity. In terms of mechanical properties, the CSE Mg plates exhibited higher yield strength (YS), ultimate tensile strength (UTS), and fracture elongation (FE) along the extrusion direction. These improvements in mechanical performance can be attributed to enhanced work hardening ability, texture weakening, finer grains generation, and the dislocation strengthening induced by shear strain.

Comparative analysis of quasi-static penetration characteristics of slotted granite and intact granite

The stress release method with rock slotting in the bottom hole by ultra-high-pressure water jet is proposed as a solution to the problem of increased rock strength due to high in-situ stress. However, the failure mode of rock with annular grooves under the simultaneous action of geostatic stress and hydrostatic pressure is still unclear. The failure characteristics, penetration force, failure mode and deformation characteristics of rock under geostatic stress are studied by numerical simulation. The results showed that the presence of an annular groove changes the rock failure mode. The radial crack propagation direction dominated by extrusion shear is deflected and will be connected to the peripheral area of the groove’s bottom. It becomes the primary crack propagation dominated by tensile shear, controlled by the crack formation zone and the stress concentration zone at the peripheral area of the groove’s bottom. The annular groove can significantly reduce the peak penetration force by about 72%. There is a critical value for the influence of groove depth on the peak penetration force. The presence of an annular groove changes the load-penetration curves from ductile failure to brittle failure mode. The groove modifies the stress propagation mode, altering the rock response and crack propagation zones. In addition, the annular groove decreases the radial force that restricts the extension of rock in the surrounding area, allowing the rock to expand more easily in the surrounding area. Therefore, this stress release method and the study’s findings are instructive for improving rock-breaking efficiency and gaining a deeper understanding of the technique.

Microstructure and mechanical properties of Mg-Al-Sn-Ca alloy extruded by asymmetric severe shear extrusion with different asymmetric coefficients

Magnesium alloys with grain refinement and texture weakening are long-term targets in the field of light alloys. A new asymmetric severe shear extrusion (ASSE) process is developed in this paper, which is specially designed to refine the grain and weaken the texture of deformed magnesium alloys. The effect of asymmetry coefficient (AC) on microstructure and properties of extruded products was studied. The results show that ASSE can effectively change metal flow. AC-1.5 shows the best mechanical properties, grain refinement (∼8.6 µm) and texture weakening. The yield strength is about 175.9 MPa and elongation is about 19 %. This study provides a theoretical basis for the further development of partial symmetric extrusion.

Investigation of microstructure and mechanical properties of ZK60 magnesium alloy achieved by extrusion-shearing process

The microstructure characterization, mechanical properties and texture evolution of a ZK60 alloy achieved via the extrusion-shearing (ES) process were systematically studied with the help of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD). The results showed that the grain size was refined to ∼1.7 μm and the microstructure became more uniform. The tensile yield strength and ultimate tensile strength at room temperature of the ES-processed alloy reached 263 MPa and 321 MPa, respectively, which were 35.6% and 10.7% higher than that of the as-annealed alloy. Grain refinement, precipitate strengthening, and dislocation strengthening are the main factors for the improvement in strength. After the ES process, the elongation of ZK60 alloy increased from 16.6% to 23.7%, which is attributed to the activation of the basal slip system and texture modification. Moreover, the tension-compression yield asymmetry of the ZK60 alloy was significantly improved after extrusion, thus indicating that the extrusion-shearing process suggested in this work has great potential for the large-scale application of magnesium alloys.

Microstructural and hardness homogeneity in an Mg–Gd−Y–Ag alloy processed by simple shear extrusion

An extruded Mg–6Gd−3Y−1.5Ag (wt%) alloy was processed by 1, 2, 4 and 6 passes of simple shear extrusion (SSE) at 553 K. Microstructural studies through electron back-scattered diffraction (EBSD) taken from the central areas of the cross sections normal to the extrusion direction (ED) exhibited microstructures mostly comprised of large severely deformed grains having high fractions of low angle grain boundaries (LAGBs) at the early stages of processing. By increasing the number of SSE passes, the fraction of fine grains, with an average size of 1.1 μm, developed through the occurrence of dynamic recrystallization (DRX), increased continuously. The highest recrystallization fraction of 72% was obtained after 6 passes. The EBSD studies on the cross section, however, showed that some degree of heterogeneity was still persistent after 4 passes of SSE along the path from the central areas towards the periphery of the specimen. This inhomogeneity in the microstructure seems to be resolved by increasing the SSE passes to 6. The micro-hardness measurements on the cross section normal to ED of the SSE-processed alloys showed a reasonable level of homogeneity after 6 passes while at the early stages of processing the hardness distribution was in its most heterogeneous state. Furthermore, the overall hardness values increased gradually from the average of 91.3 Hv for the single-pass processed alloy to 110.1 Hv for the one processed by 6 passes of SSE. This improvement in the average hardness was attributed to the Hall-Petch effect related to grain refinement, Orowan hardening as a result of Mg5Gd-type submicron-particles formed via dynamic precipitation, and substructure strengthening caused by the residual LAGBs.

Simple shear extrusion versus equal channel angular pressing: A comparative study on the microstructure and mechanical properties of an Mg alloy

Two severe plastic deformation (SPD) techniques of simple shear extrusion (SSE) and equal channel angular pressing (ECAP) were employed to process an extruded Mg−6Gd−3Y−1.5Ag (wt%) alloy at 553 K for 1, 2, 4 and 6 passes. The microstructural evolutions were studied by electron back scattered diffraction (EBSD) analysis and transmission electron microscopy (TEM). The initial grain size of 7.5 μm in the extruded alloy was reduced to about 1.3 μm after 6 SPD passes. Discontinuous dynamic recrystallization was suggested to be operative in both SSE and ECAP, with also a potential contribution of continuous dynamic recrystallization at the early stages of deformation. The difference in the shear strain paths of the two SPD techniques caused different progression rate of dynamic recrystallization (DRX), so that the alloys processed by ECAP exhibited higher fractions of recrystallization and high angle grain boundaries (HAGBs). It was revealed that crystallographic texture was also significantly influenced by the difference in the strain paths of the two SPD methods, where dissimilar basal plane texture components were obtained. The compression tests, performed along extrusion direction (ED), indicated that the compressive yield stress (CYS) and ultimate compressive strength (UCS) of the alloys after both SEE and ECAP augmented continuously by increasing the number of passes. ECAP-processed alloys had lower values of CYS and UCS compared to their counterparts processed by SSE. This difference in the mechanical responses was attributed to the different configurations of basal planes with respect to the loading direction (ED) of each SPD technique.

Full-scale push-out testing of headed stud-steel block connectors in prefabricated steel-concrete composite beams

Full-scale push-out tests of 13specimens were conducted to study the shear behavior of the headed stud-steel block connectors (HSBCs) in prefabricated steel-concrete composite bridge beams, where the key parameters of steel block height, longitudinal connector spacing, presence of oblique rebars in the precast slab, and grouting material were considered. The objective was to develop large shear stiffness, high shear capacity, and sufficient deformability of the connectors in prefabricated steel-concrete composite bridge beams. The results from the push-out tests reveal: two main failure modes the compression failure in the concrete slab and the shear failure in the grouting material and concrete slab; and the HSBC has large shear stiffness, high shear capacity (≈1500kN), and sufficient deformability. Based on the analysis of the shear extrusion dimension of the grouting material and concrete slab, the shear inclination ratio was found approximately to be 1:5, which agrees well with the stipulation specified in the EC4. The height and spacing of HSBCs are the two principal parameters affecting the shear capacity and failure mode of the specimens. By comparing the measured shear capacities of the HSBCs with those calculated by the design formulas for steel blocks and headed studs as specified in the EC4, it is shown that the steel block and headed studs can work together to resist the force between the precast concrete slab and the steel beam.