Stainless Steel Bolts Research Articles

Experimental behaviour of hybrid carbon steel – stainless steel bolted connections subjected to electrochemical corrosion

To minimise cost in practical applications whilst still obtaining a satisfactory performance, stainless steel is often employed in aggressive marine environments to ensure the durability of the structure, whilst parts of the structure less susceptible to corrosion employ conventional carbon steel. When the two materials are in direct contact in the connection region, galvanic corrosion can occur over time thus leading to an increased level of corrosion of the less noble carbon steel parts and an associated degradation in the structural performance. A comprehensive experimental study on the shear behaviour of hybrid carbon steel – stainless steel bolted connections subjected to electrochemical corrosion is presented in this paper. A total of 30 bolted connection specimens were designed and assembled from hot-rolled carbon steel and stainless steel plates. Two bolt grades, the high strength bolts 10.9 and the precipitation hardening stainless steel bolts 10.9 were used to connect the plates. Employing the electrochemical corrosion method, the specimens were subjected to various levels of corrosion by adjusting the duration over which the specimens were sunk in the corrosive medium, which resulted in both different corrosion morphology as well as different levels of mass loss of the carbon steel plates due to corrosion. The corroded connection specimens were thereafter tested to failure under shear exhibiting 4 different failure modes. The load versus deformation curves were recorded and are reported herein, whilst the observed failure modes were also documented. It was revealed that increased level of corrosions led to decreased levels of bolt pretention forces and ultimate resistances of the connections, albeit the severity of the degradation strongly depended on the adopted joint configuration and resulting failure mode.

THE IMPACT OF WATER-BASED ZINC-FLAKE COATING ON BOLT CORROSION PERFORMANCE

In this study, the coatability of bolts with water-based zinc flake coating for the conditions in which electrostatic coating is not convenient was examined. In the sandblasting stage, two different types of sand were used to determine the impact of the sand type. When the results were compared, no significant difference was observed between the use of the two sand types. However, stainless-steel bolt usage was found to be more appropriate in terms of the filter maintenance of the sandblasting machine. At zinc-flake coating stage, the qualities of the bolts coated twice and coated thrice were compared to determine the impact of the coating number. According to tests of the dry adhesion, no coating error was detected on the both bolt surfaces. The corrosion resistance test showed that, the bolts with 24 g m-2 and 36 g m-2 coating weight had high corrosion resistance.

Constitutive model of austenitic high-strength A4L-80 bolts at elevated temperatures

In recent years, the use of austenitic bolts in building structures increased rapidly. It is important to conduct the fire-resistant design of austenitic bolts because their mechanical properties may deteriorate faster than normal high-strength steel bolts in a fire. Therefore, the mechanical properties of the austenitic bolts at elevated temperatures should be clarified to provide a basis for structural fire design. In this paper, an experimental study was conducted to investigate the mechanical properties of A4L-80 stainless steel bolts at elevated temperatures ranging from 20 to 900 °C. Stress-strain curves and mechanical property index were obtained by the tensile tests. The test results were compared with other types of austenitic bolts and base materials at elevated temperatures, and a constitutive model of A4L-80 stainless steel bolts was proposed. It was seen that the proposed reduction factors can effectively predict the mechanical property of A4L-80 at elevated temperatures; the constitutive model was consistent with stress-strain curves obtained from tests.

Study on the analytical model of bending deformation for spliced glass beams with stainless steel bolts

To deal with the problems of high cost in super long glass manufacturing, which restricts their applications and development in glass structures, spliced glass beams (SGB) with stainless steel bolts connections was developed. The bending deformation of the SGB with stainless steel bolts have not been elucidated because it is difficult to achieve full beam equal stiffness in the splicing part. In view of this, the conjugate beam method was utilized to calculate the bending deformation of the SGB with stainless steel bolts. The bending deformation of the SGB with stainless steel bolts was investigated by the bending performance test, while the location of abrupt stiffness change and the actual correction coefficient were determined. It is verified by finite element analysis, on the basis of which the influence law of the height-to-span ratio and the height-to-thickness ratio of glass and stainless steel plate on the ultimate load and maximum deflection of SGB with stainless steel bolts were studied. The results confirmed that SGB composed of as few stainless steel bolts as possible can fully utilize the bending capacity of glass. This study provides a simplified calculation method for the engineering design of SGB, and opens up an idea for the design of glass structures.

On the failure and replacement of weathered rock climbing bolts

In several major outdoor rock climbing areas in the United States, it has become standard practice to remove plated steel bolts used as fixed anchors and replace them with stainless steel equivalents. To examine the need and efficacy of this practice, test results are reported for the failure strengths of plated steel bolts collected from a variety of climbing areas in Colorado, Wyoming, and California that had been exposed to full environmental conditions for periods varying between 16 and 40 years. The bolts were extracted from their original positions and tested in two fixtures designed specifically for this research corresponding to simple shear and bolt/nut thread strength that both closely simulated possible types of loading that could exist in typical usage. Strength distribution curves are provided for a number of bolts, varying in size and type. In addition, a special study was completed using a simplified numerical model of a failed bolt that resulted in a fatality to analyze the stresses and better understand the possible failure mechanism. The results of the experimental testing and the benefits of the replacement strategy are contrasted with well-documented cases of the loosening of the newer stainless steel bolts. This replacement practice needs more investigation and most likely significant revision.

New design approaches for tension, shear and interaction resistance of carbon steel bolts

More economical and statistically verified design approaches for carbon steel bolts are presented based on an extensive literature review and own systematical experimental investigations into the tension, shear and interaction resistance of carbon steel bolts conducted at the Institute for Metal and Lightweight Structures of the University of Duisburg-Essen, Germany. Herein, reliability analyses according to EN 1990, Annex D were carried out and confirmed that an increase of the reduction factor to k2 = 1.0 for the tension resistance Ft,Rd is in principle possible. Regarding the shear resistance of carbon steel bolts, simplified but more economical shear coefficients a independent of the position of the shear plane are proposed. Finally, newly design equations for the interaction resistance of carbon steel bolts are proposed, which are in line with the new interaction formulations developed by Stranghöner/Abraham and implemented in prEN 1993–1-4 and abZ/abG Z-30.3-6 for stainless steel bolts. The new interaction concept provides a more economical design compared to EN 1993–1-8/prEN 1993–1-8 and serves to harmonise the European design rules between carbon and stainless steel.

Loss of preload of unprotected bolted joints considering environmental effects: A comparative study

An experimental program, with the aim to investigate and understand the preload loss behaviour of single-bolted double-lap joints subjected to environmental effects, was conducted in this paper. Four bolt types including plain bolts, galvanised bolts, stainless steel bolts and glass fibre reinforced polymer (GFRP) bolts were investigated and three environmental scenarios (i.e. indoor, outdoor and seawater immersion) were covered to represent varying degrees of environmental severities. Steel bushes attached with strain gauges were used to obtain strain variations continuously for such bolted joints with various bolt types under different environments. Severer environments clearly introduced earlier and higher preload loss. The bolted joints with galvanised bolts and stainless steel bolts showed larger preload loss compared to those using plain bolts in seawater immersion scenario; and the preload of joints with GFRP bolts dropped to nearly zero after a certain time of exposure under seawater immersion scenario. Modelling work was then developed to describe the preload loss over time, where the effects from environmental scenario (outdoor and seawater immersion scenarios) and bolt type (plain, galvanised and stainless steel bolts) were considered and also the initial rapid preload loss can be considered.

Improved Design Rules for Stainless and Carbon Steel Bolts Loaded in Tension and Shear

AbstractThe design of non‐preloaded bolted connections as bearing type connections (category A), tension connections (category D) or bearing type connections subjected to tension and shear loading (categories A + D) is given in EN 1993‐1‐8 for carbon steel bolts. However, the design of these kinds of bolted connections made of stainless steel is given in EN 1993‐1‐4 mainly basing on those regulations developed for carbon steel bolts neglecting the specific material properties of stainless steel bolts. To overcome this lack of knowledge, experimental and numerical investigations as well as reliability analyses were systematically carried out for austenitic and duplex stainless steel bolts on their tension, single‐shear and their interaction resistance. Finally, more economical and harmonised design rules for stainless steel bolts could be developed and implemented in the revision of EN 1993‐1‐4 and the German technical approval abZ/abG Z‐30.3‐6:2022. Subsequently, the regulations covered in EN 1993‐1‐8 for carbon steel bolts were checked, considering already existing experimental results in literature and new test results carried out by the authors regarding the applicability of the newly developed rules for stainless steel bolts. As a result, it was found that the rules for carbon steel bolts can be improved, being in line with the newly developed rules for stainless steel bolts and meeting the Eurocode safety requirements.

Fatigue resistance of austenitic stainless steel bolts under tension

AbstractThe design of bolts made of carbon steel and stainless steel under fatigue loading is carried out according to EN 1993‐1‐9. However, the current regulations of the fatigue resistance of stainless steel bolts are based on investigations carried out for bolts made of carbon steel although the material properties of stainless steel are clearly different in terms of nonlinearity and strain hardening. Herewith, the question arises whether the design rules for carbon steel bolts are applicable to stainless steel bolts as the actual fatigue behaviour is almost unknown.In order to close this gap of knowledge, experimental investigations into the fatigue behaviour of partially threaded bolts according to EN ISO 4014 made of austenitic stainless steel were carried out under tension with constant amplitude loading with either a constant stress ratio R or with a constant mean stress σm. The tests were statistically evaluated and S‐N curves could be determined.The fatigue tests showed that a fatigue resistance of FAT class 50 according to EN 1993‐1‐9 can be achieved. Herewith, so far, it can be shown that a design according to FAT class 50 might be on the safe side for partially threaded bolts made of austenitic stainless steel.

Investigating the failure behaviour of aluminium alloy gusset joints under impact loading: An experimental and numerical study

The AAG joint, also known as the Temcor joint, is a well-established method for constructing long-span spatial grid structures using aluminium alloys. This joint system has been widely used and tested is considered a mature technology in the field. This paper investigates the tensile properties of 15 stainless-steel bolt connections for aluminium alloy plates at room temperature. Through testing, the load–displacement curve was obtained and two failure modes of the connection were identified. Test results show that the increase in the number of bolts and the thickness of aluminium alloy plate increases the ultimate bearing capacity of the connection. The thickness of the aluminium alloy plate was found to have a significant impact on the slippage effect of the bolts and the warping deformation of the contact surface. Based on the test results of the connection, three specimens of AAG joints were designed to study their dynamic behaviour under different impact loads. Our findings detail the dynamic response behaviour of joints subjected to varying impact times, including stress, acceleration, and displacement, as well as the resultant joint failure phenomenon. The test results show that AAG joints have good impact resistance. The refined FE model of the AAG joint was established using ANSYS/LS-DYNA, and its effectiveness was verified by comparing the stress, displacement, and acceleration between the numerical model and the experimental model. By comparing and analysing the final deformation of AAG joints obtained through test and numerical simulation, three distinct failure modes of AAG joints under impact load were identified. Finally, based on the stress nephogram and impact force time-history curve obtained by numerical simulation, the stiffness degradation law of AAG joints is discussed. This paper also discuss the energy dissipation mechanism of AAG joints during impact load, based on the strain energy time-history curve of each component.

Push-out behavior of GFRP bolts shear connectors in FRP-concrete hybrid beam

GFRP bolt has emerged as a promising shear connector in FRP-concrete hybrid beams due to flexible arrangement and ease of installation. Shear connectors are critical to maintaining the composite action and are key to the design of hybrid beams. 30 push-out tests were conducted to investigate failure mode, ultimate strength, and shear load-slip (P-S) relationship of GFRP bolts. Test parameters included bolt types, layout of bolts, longitudinal row spacing of bolts (Sl), bolt diameter (d), and bolt embedment depth (he). Results revealed that specimens with GFRP bolts exhibited bolt shank shear failure, pry-out failure of bolts, and splitting failure of concrete. In contrast, specimens with stainless-steel bolts suffered bearing failure of bolt holes in the FRP flange. Typical P-S curves of GFRP bolt specimens consisted of micro-slipping and significant-slipping phases, showing non-linear response, while P-S curves of stainless-steel bolts exhibited a linear response till failure. The effect of layout of bolts was found negligible if the longitudinal row spacing and horizontal spacing was not less than 6d and 4d, respectively. Specimens with a larger d and he demonstrated greater shear capacity. Based on the test results, prediction equations associated with failure modes were introduced to predict the capacity of GFRP bolt, which yielded results in accordance with experiments. Additionally, a refined description of P-S relationship was proposed by curving fitting, and the results correlated well with the experiments.

Experimental testing of stainless steel bolt assemblies at elevated temperatures

This paper presents the results from a programme of elevated temperature tests focussing on the tensile behaviour of austenitic stainless steel bolts of grade A2–80 and A4–70. The tensile tests were carried out on bolt assemblies in the temperature range of 20 °C and 900 °C under a steady-state approach. Following the tests, a suite of tensile strength reduction factors were derived and these were compared with the existing bolt reduction factors proposed in the literature along with the codified values for equivalent stainless steel plate materials. The comparisons reveal that the manufacturing process of the stainless steel bolt, particularly the nature of thread rolling, can significantly affect their fire performance. For example, the present study reported a reduction factor of 0.098 for A4–70 at 800 °C as opposed to 0.176 (80% higher) and 0.34 (250% higher) for a bolt formed through a different manufacturing process and equivalent stainless steel plate materials, respectively. It was also concluded that while both the tensile strength and the ductility of stainless steel bolts gradually decrease with increasing temperature, stainless steel bolts retain a higher portion of their room temperature tensile strength compared with equivalent high strength carbon steel bolts beyond high temperatures of 450 °C for A2–80 bolts and 400 °C for A4–70 bolts.

Comparative study on fracture characteristics of carbon and stainless steel bolt material

Bolt fracture often limits the ultimate strength and deformation capacity of bolted connections and leads to overall joint failure. Therefore, the prediction of structural collapse under extreme loads necessitates the incorporation of a reliable fracture model that reflects the observed structural response of bolts. This paper reports a comprehensive experimental and numerical study into the structural behaviour, ductility and fracture characteristics of Grade A4–80 austenitic stainless steel bolts and carbon steel 8.8 bolts in tension, which are commonly used as fasteners in bolted connections. Tensile tests were performed on smooth material coupons machined from both bolt grades to obtain the material response. Thereafter, tensile tests were performed on notched specimens from both grades, allowing the fracture characteristics to be studied over a range of stress triaxialities and the development of an equation relating the plastic strain at fracture to the stress triaxiality. 2D axisymmetric and 3D advanced finite element models were calibrated against the experimental results and damage propagation parameters. The developed numerical models are shown to perfectly replicate the observed experimental behaviour of the tested bolt materials under predominantly tensile loading, including fracture. Both experimental and numerical results confirm the superior ductility of A4–80 bolts over their 8.8 counterparts.

Specified pretension values and installation parameters for 2205 and 17–4 PH condition H1150 stainless steel fastener assemblies

In many areas of the United States, corrosion is a common cause of steel bridge deterioration. This has caused some state agencies to use stainless steel for bridges in very corrosive environments. However, most steel bridges in the United States contain numerous slip-critical bolted connections, and stainless steel bolts have not historically been used in slip-critical connections. Therefore, there is limited or no guidance on the specified pretension to which stainless steel bolts can be installed. There is also limited or no guidance on the installation parameters, such as the nut rotation for the turn-of-nut method or initial torque and nut rotation for the combined method of installation. In this project, torqued tension tests were conducted on 128 ASTM A1082 UNS S32205 (2205) and 128 ASTM A1082 UNS S17400 Type 630 Condition H1150 (17–4-H1150) stainless steel fastener assemblies. All bolts tests were 7/8 in. in diameter and ranged from 2 to 5.5 in. in length. Multiple types of lubricants were used in the testing to evaluate their effectiveness. Test results were used to improve upon an existing method to determine the specified pretension and installation parameters of each fastener assembly type, depending on strength, ductility, and lubricant criteria. Analysis determined that 2205 fastener assemblies can be installed to a specified pretension of 80% of their ultimate strength while 17–4-H1150 fastener assemblies can be installed at their yield strength. Nut rotation values from snug for the turn-of-nut installation method and initial torque range and nut rotation values for the combined installation method are also provided in the paper.

A Study on the Fatigue Performance and Corrosion Resistance of 304/45 Bimetallic Composite Bolts.

This paper utilized a hot-rolling process to produce composite rods and subsequently manufactured 304/45 composite bolts through the process of drawing and thread rolling. The study focused on examining the microstructure, fatigue performance, and corrosion resistance of these composite bolts. Additionally, the impacts of quenching and tempering on the fatigue performance of the composite bolts were explored and compared to the performance of 304 stainless steel (SS) bolts and Grade 6.8 35K carbon steel (CS) bolts. The results indicate that the SS cladding of the cold-worked 304/45 composite (304/45-CW) bolts was primarily strengthened by the cold deformation mechanism, which resulted in high microhardness, averaging 474 HV. At a maximum surface bending stress of 300 MPa, the fatigue cycles of the 304/45-CW reached 342,600 cycles at a 63.2% failure probability, which was significantly higher than that of commercial 35K CS bolts. The S-N fatigue curves showed that the fatigue strength of the 304/45-CW bolts was approximately 240 MPa, but the fatigue strength of the quenched and tempered 304/45 composite (304/45-QT) bolts decreased significantly to 85 MPa, due to the loss of the cold deformation strengthening effect. The corrosion resistance of the SS cladding of the 304/45-CW bolts was impressive and remained largely unaffected by carbon element diffusion.

Experimental study on mechanical properties and tightening method of stainless steel high-strength bolts

The lack of product specification of stainless steel high-strength bolts has restricted the application of high-strength bolts in stainless steel structures. Existing studies have found that stainless steel bolts experience thread galling during the tightening procedure, making it impossible to apply preload. Different studies have obtained different torque coefficient values. In this paper, a series of tests were carried out on two types of grade 10.9 stainless steel high-strength bolts and two types of ordinary stainless steel bolts, and the tensile strength, shear strength, hardness and preload level were obtained. The results show that the yield strength, tensile strength and elongation after break of the new stainless steel high-strength bolts can reach 1122 MPa, 1147 MPa and 16.3% respectively, proving that the grade 10.9 stainless steel high-strength bolts meet the requirements of the conventional grade 10.9 high-strength bolts. Tightening tests on stainless steel bolts with lubricant were carried out and it was found that the friction-reducing lubrication effect was related to the curing time of the lubricant. The lubricant Molykote D-321R Spray was found to be more effective in reducing friction and preventing thread galling in stainless steel bolts. With the optimum curing time at room temperature of 12 h, the lubricant can reduce the torque coefficient to about 0.080, meeting the torque coefficient limit for high-strength bolts. In the end, the preload level, torque coefficient and torque level for construction for stainless steel high-strength bolts are recommended for engineering applications.

Retention Factors of High-Strength and Stainless-Steel Bolts during and after Furnace Fire

Retention Factors of High-Strength and Stainless-Steel Bolts during and after Furnace Fire

Enhanced progressive collapse resistance of bolted beam-to-column connections with ductile stainless steel components

With the use of ductile stainless steel bolts and hot-rolled sections/plates as critical connection components, the progressive collapse resistance of bolted beam-to-column connections may be effectively enhanced at relatively low costs. To verify the viability of this concept, a comprehensive numerical study is performed to investigate the collapse-resisting performances of flush end-plate (FEP) and web angle (WA) connections equipped with stainless steel components. Through a detailed parametric study with various connection configurations and structural layouts, it is proved that the use of stainless steel components can produce remarkable enhancement to the collapse resistance of the connections. The average increase in dynamic load capacity is 30% for FEP connections using stainless steel bolts instead of carbon steel bolts. This average ratio can be as large as 109% for WA connections with the use of stainless steel bolts and web angles. These results clearly demonstrate the great potential of using stainless steel components in steel connections for collapse-resisting purposes. Similar concepts may be naturally applied in many other scenarios where the ductility of a few critical components controls the robustness of the entire system.

Tension and interaction resistance of austenitic and duplex stainless steel bolts

The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension are essentially based on the regulations for carbon steel bolted connections. Furthermore, the load bearing behaviour under combined tension and shear (category A + D bolted connections) was adopted from EN 1993-1-8 as well. Recent research activities within the German IGF research project “Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36” (P 1386/IGF-No. 20651 N) showed that stainless steel bolting assemblies behave different. Herein, systematic experimental investigations and an extensive literature review into the shear, tension and interaction resistance of stainless steel bolts were conducted. Furthermore, reliability analyses according to EN 1990, Annex D were accomplished to prove the partial safety factor of γM2 = 1.25 for connections made of stainless steel bolting assemblies. The results regarding the shear resistance have already been presented in a former paper in this journal. In these investigations, it could be shown that an increase of the tension resistance Ft,Rd with k2 = 1.0 is in principle possible following the normative regulations of EN ISO 3506-1 regarding the minimum ultimate tensile strength as well as North American ANSI/AISC 360 and Australian Standard AS 4100. Furthermore, a new interaction approach for both unthreaded and threaded part of the bolt lying in the shear plane could be proposed which has statistically been verified for all property classes with γM* < γΜ2 = 1.25. The new regulations have already been implemented in the current revision of EN 1993-1-4. The background for the new regulations is presented in this contribution.

Fastener Product Cold Heading Process Formulation and Precision Die Design

The stamping and forming process of the flat-head cross stainless-steel bolt was formulated and finite element simulation analysis was carried out, and the forming pressure required for the forming of cold heading stainless steel fasteners was obtained. On the basis of the results of the finite element analysis, two-dimensional and three-dimensional CAD aided design tools were used the double-station cold heading dies for screw punches are carried out. According to the two-dimensional general structure diagram, the overall structure of the die base is designed and determined, the design purpose of each part of the die is analyzed, and the elements such as the size and material of each part are determined. , Completed the design of the precision mold, the mold was successfully used in the enterprise, the production was good, and it created better benefits, providing a reference experience for the development of similar molds.