American Iron And Steel Institute Research Articles

Comparative study of surface roughness between electropolishing process and traditional sanding for low carbon steel

Steel is a versatile material utilized across various sectors, encompassing both industrial and decorative applications. AISI (American Iron and Steel Institute) 1005 steel, recognized for its low carbon content (approximately 0.05% carbon), is commonly referred to as mild steel and finds extensive use in society. This study aims to investigate the influence of electropolishing parameters, specifically current density, and time, on the surface roughness of steel. The methodology involved the preparation of samples for electropolishing tests, systematic variation of the parameters, and subsequent analysis of the resulting surface finish through roughness measurements. Samples subjected to higher current densities for shorter durations exhibited substantial reductions in roughness, while longer durations resulted in minimal or negligible changes in roughness regardless of the current density employed. This comparative analysis between electropolishing and tradi-tional sanding techniques provides valuable insights into optimizing surface finishing processes for low carbon steel applications.

Impact of Electric-Arc Welding on The Mechanical Properties of AISI 1055 Medium Carbon Steel with Varied Gauge Diameters

Purpose: This paper investigated through experimentation, the impact of electric-arc welding processes on the mechanical properties of AISI 1055 steel medium carbon steel material with varied gauge diameters.
 Design/Methodology/Approach: The study used experimental and analytical methods to investigate the impact of electric arc welding on the mechanical properties of AISI 1055 Medium Carbon Steel. The test samples were prepared based on the standards of the American Iron and Steel Institute (AISI), with varied gauge diameters. Standard tensile tests were performed on the samples before welding and after welding, using a computer-interfaced Universal Tensile Testing Machine. Data obtained from the study was analyzed using graphs, tables and charts. Finally, the sets of results for both welded and unwelded specimens were compared to determine the impact that welding has on welded medium carbon steel components and structures.
 Findings: The data recorded by the computer-interfaced tensile test machine was used to plot and display, the stress-stain graphs for the various sets of samples. The results showed that the welding processes adversely affected the Ultimate Tensile Strength (UTS), Yield Strength, Elastic Modulus and Impact Strength of the samples studied; since all the samples studied had their initial values dropped after undergoing welding and testing. However, the strain of the samples increased after welding.
 Research Limitation/Implication: Although there are other methods and techniques of welding metals, this study adopted electric arc welding to weld the samples used for the study due to resource constraints.
 Practical Implication: The findings of this study also bring to the fore, the need for industry regulators to promulgate standards to regulate the welding of medium carbon steel and by extension, other industrial materials to preserve the natural properties of the materials.
 Originality/Value: This study introduced an important perspective to the testing of engineering materials by varying the gauge diameters (a key determinant of the dimensional specifications of the specimen), to obtain a comprehensive insight into the impact of electric-arc welding on the mechanical properties of the material.

Discretized and experimental investigation of thermo-hydraulic behavior in a compact heat exchanger manufactured via SLM process

The demand for a better understanding of the fluid thermal and hydrodynamic behavior along the heat exchanger makes it necessary to develop a discretized analysis. The temperature and pressure distributions from the local analysis allow the obtaining of mechanical and thermal stress fields, making the method advantageous in comparison to the conventional global analysis. This work developed a local thermo-hydraulic model for a compact heat exchanger manufactured via Selective Laser Melting (SLM) process. The cross-flow heat exchanger core, produced with American Iron and Steel Institute (AISI) 316L, has 100 mm height, 100 mm width, 100 mm length, and a 2 mm channel diameter. The local steady-state models were compared with experimental data. The experiments were performed with water on both sides, using different temperatures for the hot side, and Reynolds numbers ranging from 1748 to 12247. The local analytical models have a good agreement, with 14% average errors for the thermal and hydrodynamic models. Besides, the impacts of channel diameter and surface roughness in the pressure drop were studied.

Structural behaviour of Cold‐Formed Steel back‐to‐back welded sections subjected to longitudinal shear

AbstractThe current study focuses on understanding the behaviour of flare v‐groove welds on back‐to‐back connected Cold‐Formed Steel welded sections (G300) subjected to longitudinal shear. A novel welding technique called Cold Metal Transfer (CMT) welding was used for fabrication with copper‐coated steel welding wire as a filler metal (ER70S‐6). This mode of welding has the advantage of controlled material deposition compared to the spray or globular mode of welding. Lap shear tests were carried out on unlipped channels including thickness of the weld, and length of the weld. The weld geometry was observed under an optical microscope after polishing and chemical etching of the weld cross‐section, as American Iron and Steel Institute (AISI) design standard provides no specification on thickness of flare v‐groove welds for CMT welding process. In general, the lap shear specimens failed in plate tearing failure mode and brittle fracture of weld at the weld contours. Additionally, the appropriateness of AISI's shear design strength equations for flare v‐groove welds was verified and preliminary design guidelines are provided addressing the lacunae in AISI design standard.

A modified model of Lundberg-Palmgren rolling contact fatigue formula considering the effects of surface treatments

The Lundberg-Palmgren (L-P) fatigue life formula, as a statistical fatigue theory, has been widely used in the industry. However, its direct applicability is limited to the components treated by surface strengthening technologies. Rolling contact fatigue tests and surface integrity measurements of American Iron and Steel Institute (AISI) 9310 rollers with several surface treatments were performed to address this issue. Based on these results, a modified L-P fatigue model was proposed, enabling the consideration of surface modification including surface roughness, residual stress, and hardening introduced by different surface treatments. Compared with the original L-P fatigue formula, its results are more accurate for surface strengthened specimens. Furthermore, this method can assess the contact fatigue life of gears treated by surface strengthening techniques.

Strong dependency of the tribological behavior of CuZr-based bulk metallic glasses on relative humidity in ambient air

Thanks to their outstanding mechanical properties, Bulk Metallic Glasses (BMGs) are new alternatives to traditional crystalline metals for mechanical and micromechanical applications including power transmission. However, the tribological properties of BMGs are still poorly understood, mostly because their amorphous nature induces counter intuitive responses to friction and wear. In the present study, four different BMGs (Cu47Zr46Al7, Zr46Cu45Al7Nb2, Zr60Cu28Al12, and Zr61Cu25Al12Ti2) underwent ball-on-disc friction tests against 100Cr6 steel balls (American Iron and Steel Institute (AISI) 52100) at different relative humidities (RHs) ranging from 20% to 80%. Controlling humidity enabled to observe a high repeatability of the friction and wear responses of the BMG. Interestingly, the friction coefficient decreased by a factor of 2 when the humidity was increased, and the wear rate of BMGs was particularly low thanks to a 3rd-body tribolayer that forms on the BMG surface, composed of oxidized wear particles originating from the ball. The morphology of this tribolayer is highly correlated to humidity. The study also identifies how the tribolayer is built up from the initial contact until the steady state is achieved.

Effect of web perforations on end-two-flange web crippling behaviour of roll-formed aluminium alloy unlipped channels through experimental test, numerical simulation and deep learning

Aluminium alloy has recently become popular in New Zealand’s construction sector as a sustainable building material. However, in roll-formed aluminium alloy (RFA) channel beams, particularly those having web holes, cripples at points of concentrated or localised loading. In this paper, end-two-flange (ETF) web crippling behaviour of RFA unlipped channels having web holes was investigated using experimental tests, numerical simulations and a deep learning model referred as deep belief network (DBN). A total of 1080 data points was generated to train the DBN, using a finite element (FE) model that was validated using 30 new experimental results reported in this paper. Compared to the test data, the DBN predictions were conservative by around 6%. Using the DBN predictions, a comprehensive parametric study was undertaken which used the validated FE model in order to explore the effects of hole size, hole location, section thickness, and bearing plate on the web crippling strength of RFA channels having web holes. Web crippling strengths obtained from the DBN, tests and finite element analysis (FEA) were utilised to evaluate the performance of current design specifications from the American Iron and Steel Institute (AISI), Australian/New Zealand Standards (AS/NZS 1664; AS/NZS 4600:2018) and Eurocode (CEN 2006, 2007). It is shown that the current design rules are not reliable to predict the web crippling strength of RFA unlipped channels with web holes. As a consequence of the parametric analysis, new web crippling strength and web crippling strength reduction factor formulae for perforated RFA unlipped channels were proposed. A reliability analysis was then conducted, which confirmed that the proposed equations are capable of predicting the ETF web crippling strength of perforated RFA unlipped channels.

Distortional buckling of cold-formed steel rack section under uniform and non-uniform bending—Numerical analysis and DSM

Due to the wide variety of cross-sections and their good mass/strength ratio, cold-formed steel (CFS) components are gaining prominence among steel structures, although this material is more susceptible to local, distortional, and global buckling. The design procedure based on the direct strength method (DSM) presented in some codes such as the Brazilian (NBR), the American Iron and Steel Institute (AISI), and the Australia/New Zealand (AS/NZS), has been well accepted for estimating simply and safely the ultimate strength of beams subject to distortional buckling for many situations. However, more recent studies show that DSM design can lead to unsafe ultimate strength for beams with a high slenderness factor of distortional buckling. This study analyzes the behavior from 768 models developed using the finite element analyses (FEA) with the ABAQUS software. Beams were analyzed with 2 support conditions (SCA and SCB), under uniform major axis bending alone. The selection of the specimens in which the distortional buckling mode is predominant (modal participation analysis) was performed through a linear stability analysis using the GBTUL software. The finite element models used in nonlinear elastoplastic analyses included geometrical initial imperfections and material nonlinearity. A parametric study was developed to investigate the influence of the slenderness factor of distortional buckling (λd) on CFS rack beams’ ultimate strength. The FEA results were compared with DSM results to verify the accuracy of this method to predict distortional ultimate strength. It is shown that, for CFS rack beams subject to uniform and non-uniform bending and distortional buckling with λd > 1.0–1.5, the DSM overestimates the ultimate strength. Modifications were proposed in the DSM to improve the accuracy in predicting the ultimate strength of the analyzed conditions.

Metals release from stainless steel knives in simulated food contact

ABSTRACT The release of chromium, nickel, and manganese from knives stainless steel produced in Italy and People’s Republic of China was investigated with the aim to check their quality and compliance with Italian Ministerial Decree 21.03.73, which is the most detailed text for the hygiene regulation of packaging, containers, and tools intended for food contact. Temperature effect on metal release is investigated in 18 sets of knives. Tests are performed by simulating discontinuous contact using a 3% glacial acetic acid solution in distilled water at 50°C and 100°C. Chromium, nickel, and manganese quantification is performed by total reflection X-Ray fluorescence. Chemical composition highlights low sulphur content, and most of them belong to the American Iron and Steel Institute (AISI) 420 type A stainless steel group. Tests performed at 100°C revealed higher concentration of released metals. Only three knives tested at 100°C exceed the limit of 100 µg L−1.

Analysis of Technological Heredity in the Production of Rolling Bearing Rings Made of AISI 52100 Steel Based on Waviness Measurements.

The production of rolling bearings is a complicated process that requires the use of many operations. The manufactured elements of rolling bearings should be of high quality while minimizing production costs. Despite many research studies related to the analysis of technological processes, there is still a lack of research and tools allowing us to satisfactorily assess the relationships between individual operations of the rolling bearing ring process of production and the quality. To perform such an assessment, one can use the concept of technological heredity phenomenon analysis. As the surface waviness of the bearing race is of key importance, the present paper aims at evaluating how the individual technological operations of the rolling bearing ring production process affect the formation of their surface waviness. The surface waviness of the bearing race was measured in both directions (two sections), i.e., along the circumference using the Talyrond 365 measurement system and across the circumference of the race using Talysurf PGI. The production of 6308-2z rolling bearings made of AISI (American Iron and Steel Institute) 52100 bearing steel was analyzed. The occurrence of the phenomenon of technological heredity in the production of rolling bearings was observed. The research results indicate that the turning operation reduces the surface waviness of the bearing rings obtained after forging, while the heat treatment causes a slight increase in surface waviness. On the other hand, grinding operation significantly reduces the waviness, with this reduction being greater for the outer ring. Furthermore, the research has shown that the waviness of the surface is an inheritance factor caused by individual operations of the rolling bearing rings manufacturing process.

Cold-Formed Steel Equal Angles with Complex Edge Stiffeners under Axial-Compression Laboratory Testing, Numerical Simulation, and Design

This paper investigates the axial-compression capacity of cold-formed steel (CFS) equal angle sections with complex edge stiffeners. Both experimental and numerical analyses were carried out. In total, 10 tests were carried out and the results are presented in this paper. Preceding to compression tests, the material properties were determined and initial geometric imperfections of all the test specimens were measured. From the results of compression tests, the specimens were all susceptible to flexural buckling. A numerical model was created using the finite-element (FE) software ABAQUS version 6.11. The results of finite-element analysis (FEA) substantiated with the experimental results. The FE models were found to accurately predict the experimental behavior. Thus, the validated FE models were used for a parametric study to analyze the effect of slenderness ratio and the orientation of edge stiffeners on the axial capacity. The axial strengths obtained from parametric study were compared with the design strengths calculated by the direct strength method (DSM) from the American Iron and Steel Institute (AISI) specification. Upon comparison, it was found that the axial strengths calculated based on the current DSM are overconservative by 58% on an average.

Effect of the web hole size on the axial capacity of back-to-back aluminium alloy channel section columns

Aluminium alloy back-to-back channels are becoming popular in building structures. These back-to-back channels often include web hole for installation of services. No previous research, however, is available in the literature for compressive behaviour of such aluminium alloy back-to-back channels with web hole. This paper presents an experimental and numerical investigation on the behaviour of screw fastened back-to-back built-up aluminium alloy intermediate and slender columns with centred web hole under axial compression. Sixteen tests were conducted in total, the results of all are reported in this paper. A non-linear finite element (FE) model was then developed, and the results were compared against the experiment results showing a reasonable match in terms of both the axial strength and failure modes. Based on 600 FE models, a comprehensive parametric study was conducted to investigate the effects of hole size, screw spacing, section thickness, column length and modified slenderness on the structural behaviour of back-to-back built-up aluminium alloy channel columns. Furthermore, the performance of current design guidelines by Australian/New Zealand Standard (AS/NZS) and the American Iron and Steel Institute (AISI) standard was assessed by comparing the axial strengths obtained from the experiments and FEA. It is shown that the AISI & AS/NZS (4600:2018) could predict the axial strength with high degree of precision; being conservative by only 10% on average to the test results. Parametric study results were used to propose the axial strength reduction factor equations for aluminium alloy back-to-back channels, and thereafter a reliability analysis was performed. The results of reliability analysis showed that the proposed equations were able to predict the reduced axial strength of aluminium alloy back-to-back channels with centred web hole.

Modifications to the Direct Strength Method of cold-formed steel design for members unsymmetric about the axis of bending

The Direct Strength Method (DSM) has been an available option for the design of cold-formed steel members in the American Iron and Steel Institute (AISI) specification since 2004. The strength of flexural members unsymmetric about the bending axis presents some challenges related to post-buckling stress redistribution, which are not fully addressed in DSM today. This paper introduces generalized modifications to the DSM strength curves to improve strength prediction for these cases. Simple adjustments for stress redistribution due to both yielding and buckling are introduced and validated against a variety of section types from various published test and simulation results. An alternate solution is also developed utilizing a novel form of the strength equation which incorporates inelastic reserve strength. Both methods provide improvement to strength predictions suitable for consideration in design specifications.

A novel machine learning method to investigate the web crippling behaviour of perforated roll-formed aluminium alloy unlipped channels under interior-two flange loading

This study presents a novel machine-learning model using the eXtreme Gradient Boosting (XGBoost) tool, for assessing the web crippling behaviour of perforated roll-formed aluminium alloy (RFA) unlipped channels (both fastened and unfastened) under interior-two-flange loading. A total of 1080 data points were generated for training the XGBoost model, utilizing an elastoplastic finite element (FE) model that was validated against 30 experimental results from the literature. A comparison against the numerical failure loads was conducted, and it was found that the prediction accuracy of XGBoost model was 94%. When compared with Ramdom Forest and Linear Regression methods, it was found that the proposed XGBoost model performed better than both the before mentioned methods. The web crippling strengths obtained from the XGBoost model, tests, and finite element analysis (FEA) were utilized to evaluate the performance of current design rules from the American Iron and Steel Institute (AISI), Australian/New Zealand Standards (AS/NZS 1664.1; AS/NZS 4600:2018) and Eurocode (CEN 2007). It is shown that the current design rules are not reliable to predict the web crippling strength of perforated RFA unlipped channels. As a consequence of the parametric analysis, new web crippling strength and web crippling strength reduction factor formulae for perforated RFA unlipped channels were proposed. A reliability analysis was then conducted, which confirmed that the proposed equations are capable of accurately predicting the ITF web crippling strengths of perforated RFA unlipped channels.

Pitting Corrosion of 316 Stainless Steel Alloy in Chloride/Thiosulfate Solutions

In this study, the effect of the presence of thiosulfate ion on pitting corrosion of AISI (American iron and steel institute) 316 stainless steel alloy was investigated in four different concentrations of NaCl solutions (1, 0.1, 0.01, 0.001 M NaCl solutions). The experiments were conducted at 50 °C based on the potentiodynamic method. During the experiment, the effect of seven different thiosulfate/chloride concentration ratios were tested (zero, 0.01, 0.03, 0.075, 0.1, 0.2, and 0.3 S2O3-2/Cl-1 ratios). Pitting potential was recorded for each test. Results show that 316 stainless steel alloy has a passivity region in all tests performed. However, this passivity region was strongly affected by both the chloride concentration and the thiosulfate/chloride concentration ratio. The addition of little amount of thiosulfate to chloride solutions was found to decrease the pitting resistance of the 316 stainless steel alloy. The addition of S2O3-2 to chloride solutions resulted in a lower pitting potential value at 0.03 thiosulfate/chloride concentration ratio compared to the other ratios.

Local and distortional buckling behaviour of aluminium alloy back-to-back channels with web holes under axial compression

Aluminium alloy back-to-back channels are becoming popular in building structures. These back-to-back channels often include web holes for installation of services. No previous research, however, is available in the literature for compressive behaviour of aluminium alloy back-to-back channels with web holes. This paper presents an experimental and numerical investigation on the behaviour of screw fastened back-to-back built-up aluminium alloy stub and short columns with web holes under axial compression. Fourteen tests were conducted in total, the results of all are reported in this paper. Prior to compression tests, tensile tests were conducted to determine the material properties of test specimens and initial geometric imperfections were also measured using a laser scanner. A non-linear finite element (FE) model was then developed, and the results were compared against the experiment results showing a good match in terms of both the axial strength and failure modes. Based on 720 FE models, a comprehensive parametric study was conducted to investigate the effects of hole size, screw spacing, section thickness, column length and modified slenderness on structural behaviour of back-to-back built-up aluminium alloy channel columns. Furthermore, the performance of current design guidelines by Australian/New Zealand Standards (AS/NZS) and the American Iron and Steel Institute (AISI) standards was assessed by comparing the axial strengths obtained from the experiments and FEA. It is shown that the AISI & AS/NZS (4600:2018) are conservative by 10% on average, when compared against the test results. Parametric study results were used to propose the axial strength reduction factor equations for aluminium alloy back-to-back channels, and thereafter a reliability analysis was performed. The results of reliability analysis showed that the proposed equations could closely predict the reduced axial strength of aluminium alloy back-to-back channels with web holes.

Experimental Investigation on Application of Linear Regression to Predict Strength of American Iron and Steel Institute (AISI) 316L Plate with Pitting Damage

This study aims to predict the strength of AISI 316L steel for offshore structures due to damage to the pitting using multiple linear regression and analysis of variance. The potentiostat accelerated method was applied to cause artificial pitting damage in a 3.5% NaCl solution of pH 2 at 60 °C. The pitting damage occurred under conditions perpendicular to gravity direction, such as on a wall structure. Each pitting was measured with various parameters. Among them, the pitting intensity and mean depth were found to be significant in the 95% confidence level. It means that pitting intensity and mean depth are the greatest influencer on strength value. A multiple linear regression model was proposed for strength prediction using significant pitting parameters, and evaluated by the coefficient of determination (R2 value). As a result, the model showed a high fitness for the data (R2 = 0.8873) and considerable prediction performance.

A Study on the Effect of Hollow Tubular Flange Sections on the Behavior of Cold-Formed Steel Built-Up Beams

This paper deals with a study conducted on flexural behavior of cold-formed steel built-up I-beams with hollow tubular flange sections. There were two types of test sections, namely, built-up sections that were assembled with either stiffened or unstiffened channels coupling back-to-back at the web and a hollow tubular rectangular flange at the top and bottom of the web to form built-up I-beam. The flexural behavior along with the strength and failure modes of the built-up sections was examined using the four-point loading system. Nonlinear finite element (FE) models were formulated and validated with the experimental test results. It was observed that the developed FE models had precisely predicted the behavior of built-up I-beams. Further, the verified FE models were used to conduct a detailed parametric study on cold-formed steel built-up beam sections with respect to thickness, depth, and yield stress of the material. The flexural strength of the beams was designed using the direct strength method as specified in American Iron and Steel Institute (AISI) for the design of cold-formed steel structural members and was compared with the experimental results and the failure loads predicted from FE models. Since the results were not conservative, a new customized design equation had been mooted and delineated in the study for determining the flexural strength of cold-formed steel built-up beams with hollow tubular flange sections.

Brief Survey of the Microstructural, Mechanical and Corrosion Properties of Duplex Stainless Steels SMAW Weldments.

Duplex stainless steels (DSSs) structures, especially the American Iron and Steel Institute (AISI)type 2205 and 2507 have greatly attracted the attention of many researchers, engineers, manufacturers as well as the end-users of the productsbecause of its superior engineering properties like strength, good toughness, particular resistance to corrosive environments and to stress corrosion cracking (SCC). Due to its worldwide progressive growth, demand and utilization, this novel steel (DSS) is rising very fast, especially in marine, power plants, chemical process, mining, petrochemical, oil and gas, pharmaceutical and many other related engineering applications. Generally, the joining of DSSs alloys is a big problem due to its susceptibility to sensitization caused by the precipitation of additional phases when heated above 600°C. Conversely, improper selection of welding parameters, imbalance ratio of austenite/ferrite phases can lead to corrosion susceptibility, solidification cracking and susceptibility to plastic deformation. Shielded metal arc welding (SMAW) technique with recommended consumables (E2209 and E2594 or E2595) is used in the fabrication of the multiphase steels with the aim of obtaining the optimum weldment with the desired input welding criteria, optimum mechanical properties with minimum defects from the microstructural perspective and excellent corrosion behaviours. This review is therefore geared towards accentuating the influence of arc welding processes, and SMAW in particular on the microstructure, mechanical and corrosion properties of DSSs weldment.

Local and distortional buckling behaviour of back-to-back built-up aluminium alloy channel section columns

The use of aluminium alloy channel sections is becoming popular in lightweight structures, especially for pillars of curtain wall systems and brace and chord members in roof trusses. In cases where increased axial strength is required, it is popular to use built-up sections, instead of single channel sections. Back-to-back built-up aluminium alloy channel sections as compression members can be used to achieve higher strengths and longer spanning capabilities. In such an arrangement, intermediate fasteners at discrete points along the length can prevent the individual channel sections from buckling independently. However, no investigative research is available on the axial strength of back-to-back built-up aluminium alloy channel sections. This paper presents both experimental and numerical investigations on the behaviour of screw fastened back-to-back built-up aluminium alloy stub columns under compression. In total, the results from 15 axial compression tests are reported. For all test specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was then developed and validated against the test results. Thereafter, a comprehensive parametric study was conducted using the validated FE model to investigate the effects of modified slenderness, screw number and section thickness on axial strength of back-to-back built-up aluminium alloy channel sections. In total, 232 FE models were analysed. Axial strengths obtained from the tests and FEA were used to assess the performance of current design guidelines offered by the Aluminium Design Manual (ADM), Australian/New Zealand Standards (AS/NZS), Eurocode 9 (EC9), Eurocode3 (EC3) and the American Iron and Steel Institute (AISI) standards. It is shown that the design, in accordance with these standards, is conservative within 20%, with the exception of the allowable stress design method mentioned in AS/NZS (1664.2:1997). The ADM, and AISI & AS/NZS (4600:2018) provide highly accurate predictions; being conservative to the experimental results by 6% and 10% on average, respectively.