American Iron And Steel Institute Research Articles

An experimental study on web-bearing resistance of cold-formed steel sigma-shaped sections with web holes under interior-two-flange loading case

Cold-formed steel (CFS) sigma-shaped sections used as flooring joists and bearers are commonly fabricated with web holes to accommodate building services. These sections featuring web stiffeners and curved lips exhibit lower web-bearing resistance than traditional lipped channel sections. However, the web-bearing resistance of CFS sigma-shaped sections with web holes has not been thoroughly investigated. To address this gap, a detailed experimental investigation was conducted, testing 29 CFS sigma-shaped sections with web holes under an interior-two-flange (ITF) loading case. For comparison, specimens without web holes were also tested. Variables such as hole diameter ratio, hole location, bearing length, and flange condition were examined. A finite element (FE) model was developed and validated against the test results. The results indicated that the web-bearing resistance for specimens with web holes was reduced by 24.0% on average. To assess the accuracy of existing design specifications, the test results were compared against the design strengths predicted by the American Iron and Steel Institute (AISI) (2016), Australian and New Zealand Standards (AS/NZS) (2018), European Standard (EC3) (2006), and Uzzaman et al. (2012). The comparison revealed that the design strength predicted by Uzzaman et al. (2012) agreed well with the test results.

Dynamic data-driven multiscale modeling for predicting the degradation of a 316L stainless steel nuclear cladding material

We have developed a long short-term memory stacked ensemble (LSTM-SE) surrogate modeling approach that can provide rapid predictions of microstructural evolution and the resultant mechanical properties of American Iron and Steel Institute (AISI) 316L series stainless steel (SS316L) fuel cladding under conditions of varying temperature and radiation dose rate. To acquire training data, we developed and implemented a kinetic Monte Carlo (KMC) model to simulate precipitation kinetics of M23C6, γ’, and G phases within SS316L cladding. Experimentally reported precipitation kinetics of SS316L in literature were linked to the kinetic parameters of the simulated precipitation in our KMC model. The model was then used to simulate microstructure evolution under synthetically generated treatments of varying temperature and radiation dose rate for periods of up to 3000 h. Changes in volume fraction, number density, and particle size of precipitates were recorded, and particle area fractions were correlated using statistical methods to develop the surrogate model. Simultaneously, the mechanical properties of the simulated microstructures were evaluated using microstructure-based finite element method (FEM) analysis to determine the elastic modulus, yield stress, ultimate tensile strength, and elongation to failure of the aged microstructures. Using this approach, our surrogate model can predict precipitation behavior within 0.25 % volume fraction and mechanical properties within 6 % relative error from the values predicted by the KMC and FEM models using 50 training simulations as input. The trained recurrent neural network-based model can return estimations of precipitation kinetics and mechanical properties ∼1000 times faster than the physics-based codes. This work demonstrates, as a proof of concept, that microstructural evolution under variable conditions can be predicted using a statistics-based model informed by a practicably obtainable dataset. The potential applications of this type of modeling framework are discussed.

Validation of AISI Design of Cold-Formed Steel Beams Using Non-Linear Finite Element Analysis

In the local building industry of Pakistan, pre-engineered steel building manufacturers mainly employ their own self-developed software and Excel sheets. These systems are based on empirical formulas mentioned in the AISI manual. Under this scenario, a need was found to validate AISI flow charts using commercial software like CUFSM 5.04 and ABAQUS R2019x. This study presents a validation of the CUFSM software and the American Iron and Steel Institute (AISI) Direct Strength Method (DSM) results of channel section flexural members using the non-linear finite element method employing ABAQUS. In this study, eight standard cold-formed channel-section (C-section) steel members were modeled and analyzed using ABAQUS to simulate realistic behavior under four-point loading conditions. The non-linear finite element models incorporated material and geometric non-linearities to capture the actual response of the steel elements. The results obtained from ABAQUS were compared with those predicted by the CUFSM and DSM, focusing on critical parameters such as nominal strength, buckling modes, and deformation patterns. During this study, it was observed that out of the selected sections, the AISI charts predict conservative and even unsafe flexural capacities in some of the cases concerning other methods, with a maximum difference of 14.03%. The differences obtained using DSM and ABAQUS when compared with the results of the AISI charts varies on both the plus and minus sides. This study will not only affect the industry in terms of innovative designs for efficient structures but also the community in regards to low-budget construction.

Moment capacity of perforated cold-formed aluminium channels–Tests, analysis, and design

This paper investigates the moment capacity of perforated cold-formed aluminium alloy (CFAA) channel sections through a combination of experimental and numerical studies. In total, 12 new experimental tests were conducted on CFAA with different cross-section sizes, web hole spacing, and numbers of web holes, under pure bending, followed by a numerical study comprising 601 validated finite element (FE) models. In the numerical study, the effects of various parameters were examined, namely web hole size, the number of web holes, section thickness, web depth, and the grade of aluminium alloy. The moment capacities obtained from both the experimental tests and finite element analysis (FEA) were utilized to evaluate the design guidance provided in the Aluminium Design Manual (ADM), Eurocode (EC), Australian and New Zealand Standard (AS/NZ), and the American Iron and Steel Institute (AISI) standards. Along with the Direct Strength Method (DSM), the Continuous Strength Method (CSM) was also evaluated. The results from both the experimental tests and their FEA indicate that DSM and EC9 are slightly unconservative, by 1% and 9%, respectively. In contrast, ADM is found to be conservative by 10%, whereas CSM is found to be unconservative by 50%.

Comparative Study of an Industrial Building Made of Cold formed steel versus Hot Rolled Steel Elements

Industrial buildings based on Cold Formed Steel (CFS) members have gained an extent of construction all over the world. It becomes an alternative process of construction to the Hot Rolled Steel (HRS) elements, allowing it to respond to the requirements in a short time. The aim of this work is to present a technical and economic comparative study of an industrial building case, made of CFS versus HRS elements, and designed according to the European and American codes. Relying on numerical modeling, the design according to Eurocode 3 demonstrates that the industrial building made of CFS is more economical compared to the HRS members building by 43% in terms of weight and 28% in terms of cost. In addition, based on the Average Capacity Design (ACD) ratio of the elements of a CFS, the design according to Eurocode 3 part 1-3 is less conservative than the same building designed according to American Iron and Steel Institute (AISI) code. Moreover, the American code privileges the safety aspect of the designed CFS building with the ASD method over the LRFD and LSD methods. Otherwise, a CFS building designed according to Eurocode 3 part 1-3 with truss columns and beams reveals a weight saving of 25% and 14%, respectively, compared to a building with a full web of beams and columns, and a building with a full web of columns and steel trusses.

Seismic Design Procedure for Low-Rise Cold-Formed Steel–Special Bolted Moment Frames

In 2007, the American Iron and Steel Institute (AISI) established a standard for cold-formed steel–special bolted moment frames (CFS-SBMFs). This structural system is designed to resist seismic forces. The CFS-SBMF system employs double-channel beams and square hollow structural section (HSS) columns that are bolted together to create a sturdy and robust structural frame. However, the CFS-SBMF system is only suitable for constructing one-storey buildings, and ASCE 7 prohibits its use in buildings with a height of over one storey. This study was conducted to expand the use of CFS-SBMFs to the construction of multi-storey low-rise buildings. Firstly, a new moment connection detail is proposed, and a design procedure is proposed to ensure that bolted connections, instead of beams or columns, have the ductility to withstand seismic forces. Secondly, the proposed design procedure for bolted connections was verified through full-scale cyclic testing. Finally, a comprehensive evaluation was undertaken to evaluate the proposed structural system’s performance under seismic excitation. The evaluation included nonlinear dynamic analysis and incremental dynamic analysis (IDA) according to FEMA P695, which provided a detailed understanding of the seismic design factors (SDFs) in multi-storey low-rise CFS-SBMF buildings.

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.