Steel Micro Research Articles

Analysis of GTAW and FCAW Welding in Impact Testing in Steel Micro Structures

Welded joints, which encompass the criteria of welding base metal connections in the material, welding speed, material quality, and material toughness, are an integral aspect of tank construction. Steel material joints frequently fail during the Gas Tungsten Arc Welding (GTAW) and Flux Cored Arc Welding (FCAW) welding procedures because air droplets become trapped in the steel material during the welding process. Finding the primary reasons for welding failures is the goal of this study. Impact and microstructure testing are used in the welding research method on SS400 steel. The FCAW welding process uses E71T-1C (Kobe) Electrodes Steel Familiarc AWS A5.2 E71T-1C) at varying currents of 80 A (Root), 100 A (Filler), and 120 A (Capping), against SS400 steel plate material with a thickness of 10 mm x 200 mm x 200 mm in V Buut seams Joints. The GTAW ER 70 SG (Familiarc Filler/Rods TG-S51T) Electrode classification allows for 90 A (Root), 110 A (Filler), and 120 A (Capping). Plate 1 has a value of 36.3 kJ/inch in the heat input calculation findings at the three section sites, while Plate 2 has the highest value of 61 kJ/inch. In the meantime, FCAW plate 2 has an impact strength value of 142.1 J, and plate 1 has an average hit in the test results at each of the three places of the specimen, according to the impact test findings. Three welding parameter points were used to record the findings of the metallographic testing's microstructure observations. plates 1 and 2 on the capping, filler, and root. being aware of the areas in the welded junction between plates 1 and 2 that are impacted by heat in the microstructure. Because of the material's strong heat input, which makes the steel brittle and promotes the formation of pearlite rather than ferrite, plate 2 has the highest value in the impact test

Investigating the effect of steel micro‐ and macro‐fibers on the bond behavior of steel rebar embedded in ultra‐high performance concrete

AbstractIn recent years, the use of ultra‐high performance concrete (UHPC) has been widely considered in special structures and retrofitting of existing structures. Since most of the relations proposed by the regulations are based on the behavior of concrete with normal strength concrete, it is necessary to conduct more experimental studies to predict the behavior of UHPC. One of these notable behaviors is the bond and cohesion between rebar and UHPC, which plays a critical role in the design and seismic behavior of structures. In the present study, a series of experimental tests of uniaxial compressive strength, splitting (Brazilian) tensile strength, elastic modulus, and pull‐out of ribbed steel bars from ultra‐high performance fiber‐reinforced concrete (UHPFRC) were performed. The tests were done considering the four‐volume fractions of hooked‐end steel macro‐fibers, straight steel micro‐fibers, a hybrid combination of these two fibers, three different diameters of ribbed steel bars, and several embedded lengths. Moreover, direct tensile and compressive stress–strain curves, Young's modulus, bonding properties of rebar with UHPFRC, and fracture mechanisms were considered. The results indicated that applying micro‐fibers may enhance the bond stress between rebar and UHPC better than macro‐fibers. Also applying hybrid fibers resulted in the concurrent enhancement of bond stress and the optimum point slip of UHPC in the stress–slip diagram. This finding maybe attributed to the satisfactory performance of micro‐fibers in reducing the growth speed of micro‐level cracks and the suitable effect of macro‐fibers in decreasing the progression speed of macro‐level cracks. Furthermore, it was revealed that the increase in rebar diameter and embedding length leads to the reduction of maximum bond stress in UHPFRC.

Mechanical properties, flexural behaviour, and ductility characteristics of fibre-reinforced geopolymer mortar

This study aims to explore the potential of ambient-cured geopolymer as a substitute for ordinary Portland cement (OPC)-based mortar. However, due to their brittle nature, geopolymer materials require reinforcement to enhance ductility. To address this, an experimental program was conducted to investigate the effects of adding polypropylene (PP) and micro steel (MS) fibers to fiber-reinforced geopolymer mortar (FRGM) at volume fractions of 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisting of fly ash (FA), and ground granular blast furnace slag (GGBS), along with a novel pozzolan called eco-processed pozzolan (EPP) was investigated. The present study assessed the hardened properties of the FRGM, including compressive strength, splitting tensile strength, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and the compressive strength of the material when exposed to elevated temperatures. The aim of this study was also to investigate the load–deflection response in terms of deflection, load, flexural strength, and toughening mechanisms; and also, the bonding between the fibers and the mortar matrix was examined using field emission scanning electron microscopy (FESEM). The results indicated that including 0.5% PP fibers and up to 1.5% MS fibers marginally improved compressive strength and MoE. The corresponding increments in splitting tensile strengths were 5% and 134%, respectively. The addition of fibers improved the fracture parameters of the FRGM. The inclusion of both MS and PP fibers significantly enhanced post-cracking flexural and toughness energy. At deflection L/150, MS fiber mixes exhibited 4–5 times higher toughness energy than PP fiber mixes, and also its evidently observed in the FESEM micrographs. The incorporation of 1.5% fiber volume to non-fibrous mix resulted in an improvement of 43.2 N.m. and 10.1 N.m. in toughness (T150) for MS and PP mixes, respectively. At an elevated temperature of 600 °C, the FRGM specimens gained a massive reduction in compressive strength, with the maximum result being at 87% for 1.5PP and 71% for 0.5MS. Overall, the MS fiber-reinforced geopolymer mixes exhibited superior performance as compared to PP fibers.

Influence of ECM process parameters on SS316 material

Electro-Chemical Machining (ECM) seems to be a hopeful technique in the production area of automobile manufacturing and other productions. In recent years, the demand for stainless steel (SS) micro products and components has evolved significantly in fields such as biotechnology, electronics, optics, medicine and so on. This stainless-steel material is ideal for hygienic environments because it is easily sterilized and corrosion resistant. The process parameters of ECM for stainless steel material are investigated experimentally in this study. The SS-316 alloy was chosen to influence the electrochemical machining process with different electrodes and to investigate process parameters using SEM analysis. The tool material has been changed to investigate the improved quality of ECM process parameters.

Studying the compressive, tensile and flexural properties of binary and ternary fiber-reinforced UHPC using experimental, numerical and multi-target digital image correlation methods

Compressive, tensile, and flexural properties of ultra-high-performance concrete (UHPFRC) specimens were studied in this research. Binary and ternary combinations of micro steel (MS), round crimped (RC), crimped (C), hooked-end (H), and polypropylene (PP) fibers were used in overall ratios of 2 % by volume of concrete. For this purpose, 100×200 mm cylindrical specimens, dog-bone specimens (length: 330 mm, width: 80 mm, thickness: 40 mm), and prismatic beams with a dimension of 100×100×500 mm (clear span: 450 mm) were cast and tested under compressive, tensile, and four-point bending tests (4PBT). A digital image correlation (DIC)-based method namely, multi-target digital image correlation (MT-DIC) was used to record the displacement and deflection values in tension and flexure tests. Furthermore, experimental findings were used in numerical simulations and additional analyses were carried out as complementary studies to provide a better understanding of the governing parameters; length, width, depth, and overall size of the beams. Results revealed that a hybrid combination of micro and macro steel fibers performs better than other specimens in all the investigated parameters and the MT-DIC method proved to be a very useful tool in capturing the displacement and deflection values. Furthermore, the inverse analysis approach for the numerical simulation of beams and nonlinear regression-based models captured the direct tension and flexural results with coefficient of determination (R2) values above 0.90.

Utilization of Steel Micro-fiber and Carbon Nanotubes in Self-compacting Lightweight Concrete

In this research, the engineering characteristics of self-compacting lightweight concrete (SCLWC) containing carbon nanotubes and steel micro-fiber were evaluated. The variables included the amount of carbon nanotubes (0, 0.02, 0.04, and 0.06% by weight of cement) and steel micro-fiber (0, 0.5, and 1% by volume). Lightweight expanded clay aggregate was used as lightweight aggregates. The experimental tests were self-compacting tests, compressive, splitting tensile, and flexural strengths, ultrasonic pulse velocity, electrical resistivity, water penetration depth, and scanning electron microscope. Adding 0.02 to 0.06 percent of carbon nanotubes to SCLWC reinforced with steel micro-fiber increases the compressive strength by about 33 to 64 percent. The use of 0.06% carbon nanotubes and 1% steel micro-fiber increased the splitting tensile strength by 36%. The use of carbon nanotubes and steel micro-fiber has the effect of influencing the filling of empty spaces and reducing concrete porosity. This can be attributed to the growing process of cement paste hydration and the filling of pores and capillary pores with the products of cement reactions, resulting in concrete compaction. Adding 0.02% carbon nanotubes to SCLWC samples containing 0.5% and 1% steel micro fibers increased the 28-day compressive strength by 36%, 34% and 33% respectively.

Fatigue bond-slip properties of steel reinforcing bars embedded in UHPFRC: Extraction and development of an accumulated damage law

The occurrence of cyclic loads in RC structures is known to deteriorate the bond between the reinforcing bars and concrete by reducing both the bond strength and stiffness, eventually leading to debonding through large increases in slip. There is much research to quantify this bond deterioration for normal strength concrete but little research has considered UHPFRC, which is the subject of this paper. This research develops a testing approach and analysis procedure to quantify the deterioration in bond as a result of high-cycle fatigue. The procedure has been developed through 18 tests of steel reinforcing bars embedded in UHPFRC with steel micro fibres. A test rig has been developed to directly measure the bond-slip under monotonic and cyclic loads. Procedures are then developed for quantifying the bond stiffness and the incremental set, that is, the increase in slip per cycle, by using the known interaction between the monotonic and cyclic bond-slip already identified by other researchers. It is shown how these procedures can be used to quantify the bond degradation under combinations of fatigue loads and how simply measuring the crack width in a structure can give a very good indication of both the residual fatigue life and bond strength.

Bond between very-high and ultra-high performance fibre reinforced concrete and profiled deck sheeting

The behaviour of steel concrete composite slabs at all load levels is controlled by the shear transfer between the profiled steel deck and concrete slab. To apply new concrete technologies, such as high-strength and fibre-reinforced concretes, to steel concrete composite slabs, it is therefore essential to quantify the interfacial bond-slip properties. In this paper, a testing approach based on single-lap shear tests, commonly applied to quantify interfacial shear properties for external reinforcement, is applied to measure the bond between profiled sheets and concrete. The testing regime consists of 6 trial tests used as the basis for developing the test methodology and 48 tests to quantify the impact of concrete strength (very-high and ultra-high-strength), high volumes of steel micro fibres, and coarse aggregate, on the bond between concrete and dovetailed and trapezoidal profile decks. The results show that the concrete strength and the presence of coarse aggregate have limited impact on the bond properties, however the presence of fibres significantly improves bond strength and toughness for dovetailed profiled decks but has limited influence on trapezoidal decks.

Mechanical properties of high ductility hybrid fibres reinforced magnesium phosphate cement-based composites

Polyvinyl alcohol (PVA) fibres were mixed with polypropylene (PP) fibres or micro-steel (MS) fibres, and then were added into MPC to improve its mechanical properties in this study. The influences of fibre hybrid schemes on the workability and mechanical properties of MPC-based composites were investigated experimentally. The crack characteristics of specimens with various fibre hybrid schemes were classified. Moreover, the microstructure of hybrid fibres reinforced MPC-based composites was further assessed using scanning electron microscopy (SEM). The experimental results show that the PVA fibres can well bridge the micro-cracks and improve the ductility index as well as the toughness index of MPC-based composites, and the MS fibres can effectively enhance the compressive and flexural strengths of MPC-based composites. PP fibres have no significant effect on the strength and deformability of the MPC-based composites in the hybrid system. The PVA and MS fibres can effectively work together to improve both the ductility and strength of MPC-based composites. Based on the current study, by adding 1.6% PVA and 0.6% MS fibres into the MPC, the compressive strength and flexural strength increases by 12.7% and 25.7%, respectively, as compared to MPC with 1.6% PVA fibres. Besides, the toughness index of the specimens increases by 26.9% and the bending performance is significantly improved.

Fresh and hardened-state properties of hybrid fiber–reinforced high-strength self-compacting cementitious composites

The main objective of this paper was to present the experimental and statistical results on durability and engineering material properties of self-compacting cementitious composites (ScCC) containing blended fibers and class-F fly ash (FFA). Fifteen mixtures were prepared to determine the effect of blended micro steel (MS)-polyvinyl alcohol (PVA) fibers and investigated under the capillary water absorption, J-ring, flexural, tensile, compressive, and impact tests. The results indicated an enhancement in the mechanical characteristics of ScCC containing FFA by the addition of fiber, which was appreciably dependent on the use of single or blended fibers, fiber types, and fibers' contents. It was found that the single/hybrid fibers and frictional pullout performance significantly affect the post-peak flexural behavior and number of post-first-crack blows. In general, the blended PVA-MS fiber-reinforced ScCC specimens have better behavior than the reference specimen. Also, the analytical analysis and probabilistic quantification were performed to study the variability of hardened properties.

Appraisal on low cost and sustainable ECC using microfibers in hybridization at later age

The addition of supplementary cementitious materials and fiber plays an important role in the mechanical and durability performance of ECC matrix. In the present research work, the assessment of the performance of ECC matrix with the utilization of iron industry waste and microfibers has been done. Three types of microfibers, i.e., polyvinyl alcohol (PVA) fiber, polyester (PET) fiber, and microsteel (MSE) fiber, were used at various percentages in hybridization to prepare total seven mixes. First, PVA was switched by PET fiber at dosages 5%, 10%, 15%, 20%,and 25% and afterwards another 25% by MSE fiber. The performance of various matrix proportions was judged based on the flexural response, electrical resistivity, air permeability, and sorptivity characteristics to introduce sustainable and cost effective ECC matrix. Test results revealed that hybridization of fibers enhanced the flexural and durability performance of ECC and also produced a cost effective and sustainable ECC matrix.

Revealing relationships between heterogeneous microstructure and strengthening mechanism of austenitic stainless steels fabricated by directed energy deposition (DED)

The heterogeneous trans-scale structures play important roles in achieving high strength and toughness in austenitic stainless steels fabricated by directed energy deposition (DED). In this study, systematic annealing investigations were demonstrated the evolution of trans-scale heterogeneous structures such as dislocations, chemical cells, nano-oxides, grains and recrystallization behavior. Their effects on yield strength were quantified. The experimentally observed yield strength of as-received and annealed samples agrees well with the estimated yield strength using standard Taylor hardening formulae. The dislocation intensity accounted for 200 MPa and became the main strength contributor, among which GND type of dislocation accounted for more than 60% of the total dislocation. Despite the development of DED steel micro inclusions, the synergistic effect of deformation twinning and pre-existing GND-induced back stress results in high tensile plasticity. This research helps to better understand the interplay between DED processing, the microstructure of 316L stainless steel and the mechanical properties that are crucial to meeting new demands.

Analysis of Micro-Machining Process for External Thread of Micro Round Tube.

This study aims to analyze the stainless steel micro round tube external threading process for the influence of different outer threading pitches (0.25 mm, 0.4 mm) and outer diameters (Ø1.9, Ø1.94, Ø2). This study also analyzes the effects of different friction factors (0.1, 0.3, 0.5, 0.7, and 0.9) and different tube thicknesses (0.4, 0.45, 0.5, 0.55, and 0.6 mm) on the threading process. This study considers size effect to use corrected material parameters for the microtube to conduct the finite element analysis by DEFORM-3D software. The goal is to understand stainless steel (SUS304) micro round tube threading and the difference by using macro material parameter analysis. The historic forming data from the simulation and experiment of threading processing are presented, and the corresponding stress/strain distribution and thread shape are also calculated. The experiment results are compared to the simulation results to verify the reliability of this analysis method. The result shows that the torque/stress/strain obtained by the modified model is always lower than by Swift’s model. It means that the size effect can be considered to apply on the forming process and provided proper torque to form the external thread of the micro round tube, e.g., the maximum torque of the round die for M2 × 0.25 occurs over the fourth stroke. For the influence of the outer diameter of the micro round tube, the larger diameter induces the larger maximum torque on the round die for M2 × 0.4, but for the smaller pitch of M2 × 0.25, the larger maximum torque is not influenced by the diameter of the tube. When the pitch of the round die is increased, the torque, stress and strain are also increased relatively. As the friction factor and torque between the round die and tube increase, the stress and strain become lower. Changing the tube thickness will not significantly change the torque, the stress, and the strain. These results guide the simulation and experiment of optimized micro round tube threading development and design to reduce cost and increase product quality.

Experimental & numerical investigation of mechanical properties in steel fiber-reinforced UHPC

This paper presents experimental and numerical investigations on mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) with four types of steel fibers; micro steel (MS), crimped (C), round crimped (RC) and hooked-end (H), in two fiber contents of 1% and 2% (by volume) and two lengths of 13 and 30 mm. Compression, direct tension, and four-point bending tests were carried out on four types of specimens (prism, cube, dog-bone and cylinder), to study tensile and flexural strength, fracture energy and modulus of elasticity. Results were compared with UHPC specimens without fibers, as well as with available equations for the modulus of elasticity. Specimens with MS fibers had the best performance for all mechanical properties. Among macro fibers, RC had better overall performance than H and C fibers. Increased fibers improved all mechanical properties of UHPFRC, except for modulus of elasticity, which saw a negligible effect (mostly less than 10%). Moreover, nonlinear finite element simulations successfully captured flexural response of UHPFRC prisms. Finally, nonlinear regression models provided reasonably well predictions of flexural load-deflection behavior of tested specimens (coefficient of correlation, R2 over 0.90).

Research on the synergistic effect of megasonic and particles in through mask electrochemical etching process

Through-mask electrochemical etching (TMEE) is one of the main methods to fabricate metal microstructures array in large scale. In deep metal microstructure etching process, lateral corrosion problem seriously affects the etching localization. In this paper, megasonic and particle combined through mask electrochemical etching (MP-TMEE) method was proposed to improve the etching localization in TMEE process. Experimental results show that the etching factor (EF) was greatly improved by MP-TMEE method compared to traditional TMEE. With the use of MP-TMEE, when the feature size of the mask was 100 μm, the average diameter and depth of the etched micro pits were 148.7 μm and 59.9 μm. The use of MP-TMEE instead of TMEE leads to an increase in EF from 1.58 to 2.50. Besides, the mechanism of the synergistic effect of megasonic and the particles in MP-TMEE process was investigated. An erosion theoretical model of passivation film was established and verified by electrochemical impedance spectroscopy (EIS) method. The measurement results of EIS show that the micro pit depth and the passivation film resistance have the opposite variation trend, and the passivation film resistance measurement results are consistent with the trend of the theoretical model. Finally, microstructure arrays involving stainless steel micro pit array and micro pillar array, copper micro pit array and micro pillar array were fabricated using MP-TMEE method.

Impact resistance of plain and rubberized concrete containing steel and polypropylene hybrid fiber

Hybridization of polypropylene–steel fiber leads to improvements of both the mechanical properties and impact resistance of concrete. This paper provides the results of an experimental impact test, which has been conducted using a low-velocity drop hammer (with an impact velocity of 2.8 m/s) on fiber-reinforced concrete (FRC) and fiber-reinforced rubberized concrete (FRRuC) prisms. Prism specimens, measuring 100 × 100 × 500 mm (depth × width × length), were prepared. The variables were different ratios of micro steel (MS) fiber (0%, 0.75, 0.825, 0.9 %, 1.0 %) and polypropylene (PP) fiber (0%, 0.1 %, 0.175, 0.25 %, 1%) with/without crumb rubber (CR) with a partial replacement of fine aggregate at a ratio of 20 % by volume. FRC with CR produced higher first and final impact energy compared with prisms without CR. By contrast, the density, as well as the compressive and tensile strengths decreased, whereas the voids and water absorption of concrete increased due to the CR replacement. The specimen, which was reinforced with 0.9 % MS + 0.1 % PP hybrid FRRuC, produced high final impact energy of approximately 887.2 J, which was 10 times higher than that of plain concrete ; the impact ductility index was 4.15, which was twice the value of plain concrete. Furthermore, the most significant improvement in mechanical properties was found for specimens with 0.9 % MS + 0.1 % PP hybrid fiber.

EXPERIMENTAL INVESTIGATION OF EFFECT OF CRYO-TREATMENT ON MICROMILLING OF INCONEL 718

In this paper, the effect of cutting parameters during micromilling on surface finish and material removal rate is presented. Inconel 718 alloy and high-speed steel micro end mill are used as work material and cutting tool, respectively. High-speed steel end mill of 1 mm diameter is subjected to cryogenic treatment. Machining studies are performed on Inconel alloy using untreated and cryogenic treated cutters. The milling tests are conducted at three different values of feed rate, cutting speed and depth of cut. Also, tool wear, microstructure and microhardness of different treated and untreated end mill are investigated and discussed in detail. The results showed that cryogenic treatment significantly improved the tool wear. The surface finish produced on machining the work-piece is better with the cryogenic treated tools than when compared with the untreated tools. The material removal rate is better with the cryogenic treated tools than when compared with the untreated tools. Improvement in tool life was up to 53.16% for Inconel 718 material when machined with cryogenically treated micro end mill.

Establishment of Optimum Production Regimes for Extra-Furnace Processing of Low-Alloy Steels in Order to Ensure their Good Corrosion Resistance in Aqueous Media through Formation of Favorable Non-Metallic Inclusions

Optimum production regimes are established for steel extra-furnace treatment providing not only low contamination with non-metallic inclusions (NI), but also formation of NI with favorable morphology not having a deleterious effect on steel corrosion resistance. It is shown that this is achieved by controlled input of Al in steel alloying and deoxidation stages, limiting its content in steel, limiting the temperature for additionof aluminum and calcium in the final treatment stage, and also the duration of the flushing period. For steel micro- alloyed with titanium it is also possible to form another type of NI that does not adversely affect steel corrosion resistance. The oxide component of these NI with a high content of calcium and titanium acquires a rounded shape. Formation of such NI is achieved by the controlled addition of Al, Ti, and Ca in the concluding treatment stage.

Investigation of the feasibility of energy piles in Bangkok and their impacts on pile behavior

The energy pile concept, which involves using piles as heat exchanging units for ground source heat pump (GSHP) system, have recently been proposed as a promising way of using shallow geothermal energy resource for cooling buildings to improve energy efficiency and reduce the heat island phenomena in Bangkok Thailand. The power rating of heat exchange capacity of the piles is one of the most important design parameters to consider when evaluating the feasibility of the system. In this study, a full-scale thermal response test was conducted on a spun pile equipped with a single U-loop with the power rating of 60 W/m, yielding the effective thermal conductivity of 3.3 W/m°C, while that on steel micro pile yielded the value between 1.49 and 2.01 W/m°C with power rating of 10W/m. Effects of possible thermal cycles on the compression of Bangkok sand was also investigated in order to evaluate any adverse effects of using piles on pile settlement.

A Study on the Mechanical Properties of the Hybrid Fiber-Reinforced Mortar Using the Macro Steel and Micro Carbon Fibers

In the present study, an experiment was conducted to investigate the mechanical properties such as fluidity, compressive strength and flexural performance (flexural strength and toughness) of a single fiber-reinforced mortar (FRM) using only macro steel fiber (SF) or micro carbon fiber (CF) with different material properties and SF-CF hybrid FRM using a mixture of macro SF and micro CF. The specimens incorporated macro SF and micro CF in the mix proportions of 100-0%, 75-25%, 50-50%, 25-75% and 0-100% by volume at a total fiber volume fraction of 1.0%. Their mechanical properties were further compared and reviewed with the plain mortar at 28 days of age. The experimental results of fresh mortar showed that the table flow of mortar using only macro SF was slightly reduced compared to plain mortar, whereas the table flow of mortar using only micro CF and SF-CF hybrid mortar decreased significantly with increase of micro CF. It was revealed from the test of the hardened mortar that the SF-CF=75-25% (M3) specimen showed the highest compressive and flexural strength, and the SF-CF=50-50% (M6) specimen obtained the highest flexural toughness. Therefore, it was possible to confirm the synergistic reinforcement effect of that enhanced the strength and improved the flexural performance by hybrid of macro SF and micro CF. Based on the results of this experiment, the optimal mix proportion of SF-CF hybrid FRM is proposed in this paper to improve the compressive strength, flexural strength and flexural toughness.