Stainless Steel Bars Research Articles

Effects of stainless steel reinforcement and fibers on the flexural behaviour of high-strength concrete beams subjected to static and blast loading

This research has investigated the effects of stainless steel (SS) reinforcement on the flexural behaviour of high-strength reinforced concrete beams subjected to static and blast loading. As part of the tests, beams built with high-strength concrete (HSC) and Grade 520 MPa stainless steel bars were tested under blast loads using a shock-tube. Companion beams were also tested under quasi-static conditions. The effects of steel fibers on shear and flexural response were also investigated. In the beams with stirrups, the use of SS bars improved blast behaviour by increasing blast capacity and reducing displacements when compared to identical beams designed with ordinary steel. The use of fibers further improved blast performance by reducing displacements and increasing damage tolerance. In beams without stirrups, the use of fibers was unable to completely substitute for transverse steel and prevent failure, however the shear capacity was increased. As part of the numerical study, the behaviour of the test beams was simulated using 2D finite element (FE) modelling. The FE results show reliable predictions of the beams under static and blast conditions.

Assessment of the tensile behavior of twisted steel connectors for masonry retrofitting

The paper presents an experimental investigation on the tensile behavior of twisted stainless-steel bars considering different parameters that could affect their performance, namely the bar diameter (8, 10, 12 mm), the embedment depth, the position within the wall (installed into brick or in a T-mortar joint), the strength of the masonry and the type of loading (monotonic or cyclic load). Experimental results showed very good performance with reliable results associated to low coefficient of variation of the loads and very limited damage of the base material. The load–displacement curves showed a good ductility, an excellent superposition between monotonic and cyclic tests and an extended plateau at ultimate load. Among the different investigated parameters, the position within the wall was the most influential one, with higher loads associated to mid-brick location of the bar. Finally, based on the experimental results a user-friendly equation is proposed to predict the ultimate tensile load.

Flexural behavior and serviceability performance of SSC beams reinforced with hybrid GFRP-stainless steel bars

Using fiber-reinforced polymer (FRP) bars instead of steel bars to reinforce concrete structures has become an important method to solve the corrosion problems. FRP bars reinforced concrete (FRP-RC) beams suffer sudden failure owing to the brittleness of FRP bars. Therefore, it is suggested to add steel reinforcements in FRP-RC beams to improve the ductility. This study analyzes the flexural performance of seawater and sea sand concrete (SSC) beams reinforced with hybrid GFRP and stainless steel (SS) bars, in which GFRP bars are used as tension bars while SS bars are used as compression bars. The flexural performances of GFRP bars reinforced SSC beams and SS bars reinforced SSC beams were also studied for comparison. Based on the test results, the cracking moment, load-carrying capacity, deflection, and ductility of the SSC beams are discussed and compared with the guidance in current design codes. Results show that ACI 440.1R-15 and CSA S806-12 reasonably predict the cracking moment and bearing capacity, but both underestimate the deflection at the service load. Furthermore, the moment capacity calculation equation is proposed with good accuracy. The ratio between the reinforcement ratios of GFRP bars and SS bars is suggested to meet the ductility requirement.

Effect of inertia friction welding speed on microstructure and mechanical properties of 2205/316L stainless steel joints

In this paper, inertia friction welding (IFW) is used to enable a high-quality and efficient joint between 2205 duplex stainless steel and 316 L stainless steel. Specifically, stainless steel bars (2205/316 L) with a diameter of 35 mm and length of 120 mm are used. In addition, the effect of IFW speed on the microstructure and properties of welded joints is assessed using scanning electron microscopy, electron backscattered diffraction, energy dispersive X-ray spectroscopy, microhardness test, and tensile tests. The results indicate that dynamic recrystallization of the microstructure of joints occurs during IFW welding, which causes grain refinement. The diffusion of Ni from the 316 L base metal to the 2205 base metal, as well as the diffusion of Cr from the 2205 base metal to the 316 L base metal, results in a strong metallurgical bond between the two materials. In addition, the microhardness of the welding area exceeds that of the base metal (the closer to the weld zone, the greater the microhardness value). The tensile strength of the joints initially increases with increasing IFW speed, but then it starts decreasing beyond a certain point. The optimal welding parameters for achieving high-quality joints between 2205 duplex stainless steel and 316 L stainless steel are as follows: axial pressure = 5 MPa, rotational inertia = 4.17 kg·m2, and IFW speed = 2700 r/min.

Axial compression of seawater sea sand concrete columns reinforced with hybrid FRP–stainless steel bars

Using fibre-reinforced polymer (FRP) bars instead of steel bars to reinforce concrete columns in harsh environments has become important for solving corrosion problems. The brittleness of FRP bars significantly reduces the column ductility. It has been proposed that columns can be reinforced with hybrid FRP and steel bars to improve ductility, but related research is very limited. In this research, the axial compression behaviour of seawater sea sand concrete (SSC) columns reinforced with hybrid FRP bars and stainless steel (SS) bars was studied. In total, 84 SSC columns were designed, including 15 SS reinforced SSC (SS-SSC) columns, 15 glass-FRP (GFRP) reinforced SSC (GFRP-SSC) columns, 45 hybrid FRP–SS reinforced SSC (FRP–SS-SSC) columns and nine plain SSC columns. The failure modes, load–axial displacement curves, bearing capacity and ductility were analysed, considering the effects of the reinforcement types, reinforcement ratios and concrete strength. The results show that ductility could be significantly improved by hybrid reinforcements; the ductility indexes of the FRP–SS-SSC columns were close to those of the SS-SSC columns. The proposed equation could accurately predict the bearing capacity of SSC columns. Furthermore, a theoretical stress–strain relationship for the studied axial compression SSC columns is proposed.

Microstructure Evolution and Mechanical Properties of Lean Duplex Stainless Steel Bars Prepared by a Short Process

Microstructure Evolution and Mechanical Properties of Lean Duplex Stainless Steel Bars Prepared by a Short Process

Improve the manufacturing efficiency of steel bars by using hot-wire pulse arc additive manufacturing

With the advantages of high material utilization and freedom of structural form, wire and arc additive manufacturing (WAAM) is a feasible solution to achieve fully automated construction of buildings. However, the current manufacturing efficiency of steel bars manufacture using WAAM is not sufficient for construction industry applications. This paper uses hot-wire pulse arc additive manufacturing (HWPAAM) to improve the manufacturing efficiency of 316L stainless steel (316L SS) bars. The efficient manufacturing principle of HWPAAM 316L SS bars was analyzed in this article. The effect of different manufacturing efficiency on heat input, macrostructure, microstructure, and mechanical properties of 316L SS bars was studied. The results show that the manufacturing efficiency of the 316L SS bar manufactured by HWPAAM can reach 31 mm/min. The connection rate of hot-wire power supply can be improved to 96.7 % and the heat input of the arc can be reduced by 65 % at 31 mm/min manufacturing efficiency. With the decrease of arc heat input, the grain size decreases. The improvement of manufacturing efficiency has little effect on the macrostructure of the 316L SS bar. Under uniaxial tension, the mechanical properties of the 316L SS bar standard specimen with different manufacturing efficiencies are basically the same. By using this manufacturing process, the manufacturing efficiency of the 316L SS bar is greatly improved while the performance is not significantly reduced.

Bonding mechanism and fracture behavior of inertia friction welded joint of 2219 aluminum alloy to 304 stainless steel

The 2219 aluminum (Al) alloy bars were welded to 304 stainless steel bars by inertia friction welding. The intermetallic compounds (IMCs) at the friction interface were characterized and analyzed and the bonding mechanism of the welded joint was studied in detail. Characterization of the microstructure at the friction interface revealed that there were two types of IMCs layers, the nanoscale Fe4Al13 layer and the microscale Cu-rich layer. In particular, the Cu-rich layer is bonded to the base material by Al2Cu and two Fe–Al–Cu ternary IMCs. Meanwhile, it was verified both theoretically and experimentally that the Fe4Al13 layer had less misfit with the base material with higher bonding strength at the interface. The formation of the Cu-rich layer increases the lattice mismatch, particularly at the interface of the ternary IMCs layer which becomes a weak area where the crack initiates and propagates easily.

Effects of cracks on chloride‐induced corrosion initiation and propagation of carbon and stainless steel rebar

AbstractCurrent durability design models for reinforced concrete structures in chloride‐contaminated environments do not consider the effects of cracks, which in practice are almost inevitable. Literature reports controversial results on corrosion propagation time of carbon steel (CS) in cracked concrete, while fewer information can be found on stainless steel (SS) rebar, which can be employed as additional protection strategy. In this experimental study, corrosion initiation and propagation of CS and SS rebar in uncracked and cracked concrete are presented. Prismatic specimens, reinforced with CS and 304L SS bars were subjected to a loading procedure to induce longitudinal micro‐cracks and exposed to a 3.5% NaCl solution for more than 2 years. Corrosion was monitored with electrochemical techniques and at the end of exposure corrosive attacks were observed. Results demonstrate the fundamental contribution of micro‐cracks in accelerating corrosion phenomena for CS, while SS is still in passive conditions also in cracked concrete.

Comparative experiment of steel bar corrosion at concrete construction joints

Introduction: Construction joint is common and even inevitable in most of the reinforcement concrete structures. This study was to assess the effect of construction joints on chloride-induced corrosion of reinforcing steel in concrete.Methods: Test parameters included two environmental conditions (salt solution immersion condition and cyclic wet-dry condition), two forms of construction joint (direct wet joint and roughened wet joint) and four types of steel bar (mild steel bar, ferritic stainless-steel bar, austenitic-ferritic stainless-steel bar and epoxy-coated steel bar). The corrosion test of 90 specimens was carried out by electrochemical accelerated corrosion method. The weight loss of each steel bar and steel bar section in specimens was measured. An influence coefficient (k_j) of construction joint on local weigh loss of steel bars was defined.Results: Except for epoxy-coated steel bars, the most severe corrosion of experimental steel bars in concrete specimens all occurred at the joints, while the corrosion in non-joint sections of steel bars was relatively uniform and less. The weight loss rate of specimens has the range of 1.18% to 15.73% with an average value of 6.22%. The average k_j of mild steel bars, S11203 stainless steel bars, and S23043 stainless steel bars are 1.38, 1.92, and 1.97, respectively. The average k_j of specimens in immersion condition and cyclic wet-dry condition are 1.44 and 2.07. The corrosion of epoxy-coated steel bars mainly occurred at the damage locations of epoxy coating, not mainly at the joints.Conclusion: Chloride-induced corrosion of steel bars at construction joints was always more severe than at non-joints, especially in cyclic wet-dry environments, even for stainless-steel bar, but epoxy-coated steel bars were excluded.

Comparative study on the bond performance of near-surface mounted fiber-reinforced polymer bars

This paper presents the experimental and analytical results of a large study on the bond performance of near-surface mounted (NSM) fiber-reinforced polymer (FRP) bars. The investigated parameters included the bar material (basalt-FRP (BFRP), glass-FRP (GFRP), carbon-FRP (CFRP), and stainless steel (SS) bars), the bar surface configuration (deformed and sand-coated bars), the filling adhesive (NSM-Gel, Sikadur-30, and Sika Grout-214), and the bonded length of the bar (6, 12, and 24 times its diameter). Sixty-six C-shape concrete specimens were tested under direct pullout loading configuration. The bond strength, the free-end and loaded-end slip, the strains in the NSM bar, and the modes of failure of the tested specimens are reported and discussed. The NSM-Gel adhesive outperformed other adhesives in developing the bond strength of the tested specimens regardless of their bar material. Both the deformed and sand-coated NSM-BFRP and GFRP bars showed almost similar bond strengths while the NSM-CFRP bars showed the highest strengths. The images obtained from the scanning electron microscope confirmed the obtained results in terms of the modes of failure and the bond failure mechanism. Analytically, the BPE model was calibrated using the experimental results to describe the bond stress-slip relationships of the FRP bars.

Analysis on the transverse compression performance of the CORC cable

The conductor on round core (CORC) cable is considered as one of the best candidate cables for next generation fusion project due to its advantages of high current density, small cabling degradation and excellent magnetic field performance. Nevertheless, the CORC cable will be affected by huge transverse compression force during production and transportation, especially during operation in fusion project, which is the main reason that the current-carrying capacity of CORC cable will be irreversible degradation. There is little research on the transverse compression performance of CORC cables at present, and the influence rules of some cable parameters on its transverse compression performance are not yet clear. Therefore, in this paper, transverse compression tests are carried out on CORC cables of different former sizes, materials, and structures. The experimental results show that the larger the cable former size, the better its transverse compression performance. The transverse compression load limit of hollow tube former cable is larger than that of solid bar former cable. The performance of stainless steel bar former cable is similar to that of copper bar former cable. The limit value of transverse compression load of copper hollow tube former cable is larger than that of stainless steel hollow tube former cable. A 3D finite element model is also established to explain the internal reasons for the differences of current-carrying capacity decrease tendency of different CORC cables. The research results can provide theoretical basis for the selection of former of CORC cable in the future. In addition, the influence of load block structure on the CORC cable’s transverse compression load limit is also studied in this paper. The results show that the arc block can significantly increase the transverse compression load limit of CORC cable. The research results can provide a basis for the selection of the structure of support former when making cable in conduit conductor and the structure of coil former when winding CORC coil magnet.

Nickel contamination after minimally-invasive repair of pectus excavatum persists after bar removal.

BackgroundMinimally-invasive repair of pectus excavatum (MIRPE) has been shown to be associated with high release of trace metals into patient’s body. The aim of our study was to analyze the kinetics of metal contamination after MIRPE and after bar removal.MethodsWe prospectively assessed nickel and chromium changes in blood, urine, and local tissue in patients undergoing MIRPE with stainless-steel bar(s). Baseline samples were taken prior to surgery, further samples were taken at six defined time points until 30 months after bar removal. Clinical symptoms were evaluated at the time of every sample collection.Results28 patients were included (mean age 16.4 years). At four weeks after MIRPE and persisting up to bar removal, we found significantly elevated trace metal levels in blood and urine. Tissue nickel and chromium levels were significantly elevated at the time of bar removal. After bar removal, the concentration of trace metal in urine and the concentration of chromium in plasma decreased gradually. In contrast, nickel levels in blood further increased. Five patients showed irritative symptoms after MIRPE, all symptomatic patients had elevated metal levels.ConclusionsFollowing MIRPE, we found a rapid systemic increase of nickel and chromium. Our data indicate that trace metal release could cause irritative symptoms. The prolonged elevated systemic nickel levels beyond bar removal necessitate further investigations of the long-term side effects of MIRPE.

The effect of different implant impression splinting techniques and time on the dimensional accuracy: An in vitro study

Background: Splinting of impression copings is generally recommended for complex implant-supported restorations. It can also be used in the digital workflow when a control model is needed to improve the fit of the prosthesis. However, there is a lack of knowledge on how dimensional accuracy is affected by different splinting techniques and time factors. ObjectivesTo evaluate the time factor on the dimensional stability of different implant impression splinting techniques used in the conventional and digital workflow. Materials and methodsTen pairs of implant analogs were fixed to a stainless steel bar. Modified impression copings were connected to the analogs and eight splinting strategies evaluated (n=10): (1) type I impression plaster (PLA), (2) autopolymerizing acrylic resin, cut and rejoin technique (PTR), (3) light-cured acrylic resin, cut and rejoin technique (ILC), (4) light-cured acrylic resin, no cutting and rejoining (ILN), (5) VPS bite registration material (SBR), (6) bis-acryl bite registration material (LXB), (7) bis‐acryl composite resin (PTP), (8) 3D printed splint (3DP). In each group, the position of modified impression copings was scanned with a laboratory scanner at different time points: (1) unsplinted impression copings (baseline), (2) 2 h after splinting, (3) 24 h after splinting. Modified impression coping design allowed using metrology software to measure and compare distance, vertical, angle and rotational deviations between impression copings. ResultsAll types of splints showed dimensional deviations. After 2 h of splinting, the lowest distance deviation was recorded in PTR (15.4±6.15µm), vertical deviation – in ILC (19.2±27.37µm), angle deviation – in ILC (0.08±0.1°), rotation – in LXB (0.2±0.24°) groups. Comparing results 2 and 24 h after connection of impression copings, statistically significant deviations in the distance were recorded in groups PLA (-5.6±5.95 µm), PTR (5.5±7.01µm), ILN (19.2±14.26µm), PTP (23.8±12.55µm). ConclusionsThe best dimensional accuracy was observed in the ILC group, followed by PTR and 3DP groups. Clinical significanceProper selection of splinting technique and polymerization time can increase the accuracy of conventional or digital impressions. Splinting techniques with rigid materials, proper polymerization and compensating for material shrinkage seem to produce the best results.

Performance of Glass to Iron-based Shape Memory Alloy Adhesive Shear Joints with Different Geometry

Previous research has shown that glass beams with external, mechanical post-tensioning along their edges show better structural performance than glass beams without any such reinforcement. The initial and post-fracture load-bearing capacity of glass beams can be increased by reinforcing them with stainless steel or fiber-reinforced plastic (FRP) tendons that are post-tensioned and connected to the beam edges. However, post-tensioning of stainless steel or FRP bars or strips is complex and challenging because it often requires special setups, such as hydraulic jacks. Iron-based shape memory alloys (Fe-SMAs) are promising post-tensioning materials due to their efficient activation procedure and good mechanical properties. The target prestress level can be introduced by heating the Fe-SMA to a specific temperature followed by cooling down naturally to ambient temperature. As a contribution to assessing the feasibility of strengthening glass elements with adhesively bonded Fe-SMA strips, this paper focuses on the bond behavior of glass-to-Fe-SMA lap-shear joints based on numerical investigations. A finite element model is developed to evaluate the effect of adhesive thickness, Fe-SMA strip thickness and bond length on the structural behavior of glass to Fe-SMA lap-shear joints.

Seismic performance of concrete bridge piers reinforced by stainless steel bars: A quasi-static experimental study

This paper presents a set of large-scale quasi-static tests on 6 bridge piers reinforced by stainless steel bars and 4 bridge piers reinforced by conventional carbon steel bars as control specimens to investigate the seismic behaviour of stainless steel reinforced concrete bridge piers. Different reinforcement ratios and axial loads are applied on the columns. The damage progression of the columns during the test is recorded. The experimental result is analysed in terms of force–displacement relation, energy dissipation capacity and ductility to evaluate the seismic performance of bridge piers reinforced by stainless steel bars. It is found that concrete columns with stainless steel reinforcement have similar lateral strength and larger deformation capacities compared to the conventional RC column. However, the application of stainless steel may reduce the energy dissipation capacity of RC columns. Dual-wave buckling of stainless reinforcement and severer concrete cover spalling of columns reinforced by stainless bars are observed in this work.

Design of ‘ready-to-pack’ deep frying machine

Food processing by applying high temperatures can eliminate most microbes and inactivate enzymes that can cause spoilage. Food processing tools and machines have an important role to provide better quality results and carried out more efficiently and effectively. This study aimed to obtain and analyze data also to create design documentation for a ‘readyto-pack’ deep frying machine. Data were collected by means of observation, interviews, and documentations. Data analysis was carried out by processing the collected data with mathematical calculations. The design documentation process was done using Solidworkss software. This ‘ready-to-pack’ deep frying machine had been successfully designed and was expected to facilitate the frying process and simultaneously proceed with the spinning process. This machine was designed to use a 0.373 kW motor, constructed from stainless steel and angle bars and hollows. The analysis results of the shaft planning data at a minimum diameter of 9.06 mm and the use of 25 mm-diameter shaft were declared safe with a stress analysis on the frame of 1.065 x 107 N/m2 which was still below its maximum stress. Therefore, the machine could be constructed based on this design and analysis

Tensile Properties of 22Cr-12Ni Austenitic Stainless Steel Thick Plates and Bars at Cryogenic Temperatures

The tensile properties of XM-19 austenitic stainless steels with thick plates (30 mm thickness), extra-thick plates (100 mm thickness), and rectangular bars (square of 14.3 mm) were examined at cryogenic temperatures. Influence of thermomechanical treatments on the steels was demonstrated. Even though their 0.2 % proof stresses were over 1200 MPa at 4.2 K, there were variations in strength depending on location. Namely, the 1/2t specimen (the position of the half in the thickness) of extra-thick plate showed lower 0.2% proof stress, elongation, and reduction of area at 4.2 K than the 1/4t (the position of the quarter in the thickness) and the thick plates. The effect of grain size on the 0.2% proof stress was clearly described by the Hall-Petch relationship for the materials.

Sustainability of alternative reinforcement for concrete structures: Life cycle assessment of basalt FRP bars

Due to the global climate emergency as a result of anthropogenic activities, an accelerated progress towards sustainable thinking is needed. The construction industry, as one of the contributors to the global emissions, must re-examine the construction materials, procedures and technologies which are traditionally used. To reach an informed design decision with regards to sustainability, the engineering community would benefit from independent and objective studies of the environmental impact of materials and systems. Crucially, decarbonising concrete structures should emerge as a priority, due to the wide availability and utilisation of the material. Although the fibre reinforced polymers have caused an interest of the construction industry due to their favourable mechanical properties, Life Cycle Assessment (LCA) studies of alternative reinforcing options are very limited to date.This paper presents an evaluation of the environmental impact of BFRP reinforcing bars. Using an LCA approach, the conducted study aims to examine the potential of utilising BFRP for creating more sustainable reinforced concrete structures. It includes a contribution analysis of the production of BFRP bars, as well as comparison with steel, glass FRP, galvanised steel and stainless-steel bars. Additionally, a comparison of BFRP and steel reinforced beams is offered, supported by the results of experimental flexural testing. The findings of the study demonstrate that BFRP bars can contribute to large reduction of embodied emissions of reinforced concrete elements in comparison with steel, and other reinforcing materials.

Experimental investigation on the flexural behaviour of stainless steel reinforced concrete beams

The durability of reinforced concrete (RC) structures and infrastructure has been the subject of significant attention from the engineering research community in recent years, mainly owing to the deterioration of RC elements due to corrosion of the embedded steel reinforcement. In this context, stainless steel reinforcement can provide an efficient solution to enhance the expected lifetime of concrete structures, reducing the damage due to corrosion of the reinforcement and carbonation and deterioration of the concrete. However, current international design standards for reinforced concrete structures do not include appropriate guidance for stainless steel reinforced concrete (SSRC). In order to investigate the behaviour of stainless steel RC beams, a series of six beam tests was conducted and is discussed herein. The key performance measures for RC beams such as load-deflection response, cracking behaviour and deflections at service load are assessed. The validity and applicability of existing design rules, which were developed for carbon steel RC, are also examined for stainless steel reinforced concrete members. Other recently developed design procedures, based on the Continuous Strength Method and including an accurate material model for the stainless steel bars, are also examined.