Material Properties Of Stainless Steel Research Articles

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.

Stainless steel reinforcement: New material in the latest draft of second‐generation Eurocode 2

AbstractThe durability of reinforced concrete structures exposed to aggressive environments is affected by corrosion of carbon steel reinforcement. For this reason, it is of great practical interest to look for alternative solutions guaranteeing durability through the incorporation of corrosion‐resistant materials, such as stainless steel rebars. This type of steel is specially recommended for structures with a long lifespan, located in aggressive environments, with chlorides or de‐icing salts, and for structures where repair, inspection and rehabilitation is complicated. This solution presents a challenge from the point of view of the materials themselves, the mechanical design and their durability. This article presents the material properties of stainless steel and their influence on concrete structures. Furthermore, it is explained how these properties have been taken into account in the latest draft of the second‐generation Eurocode 2.

Shear resistance and design of stainless steel plate girders in fire

In this paper, the shear resistance and design of stainless steel plate girders at elevated temperatures are investigated. A broad range of parameters influencing the structural response of stainless steel plate girders in fire are taken into account, considering (i) austenitic and duplex stainless steel grades, (ii) rigid and non-rigid end posts, (iii) different aspect ratios for the unstiffened portions of the plate girders, (iv) various web slendernesses and (v) different elevated temperature levels. The influence of these parameters on the behaviour of stainless steel plate girders at elevated temperatures is considered. Currently, there is an absence of specific design rules on the fire design of stainless steel plate girders in the European structural steel fire design standard EN 1993-1-2. Considering this, an accuracy assessment of the room temperature stainless steel plate girder design recommendations of the European structural stainless steel design standard EN 1993-1-4 applied with the elevated temperature material properties of stainless steel is performed. The results indicate that this approach leads to unsafe and scattered ultimate strength estimations for stainless steel plate girders in fire. New fire design recommendations for stainless steel plate girders that are in accordance with the existing design provisions of EN 1993-1-2 and EN 1993-1-4 are proposed. The accuracy and safety of the proposed new design recommendations are comprehensively verified against the results from nonlinear finite element modelling.

Microstructure, mechanical properties and IASCC susceptibility of stainless steel baffle bolts after 30 years of operation in a PWR

Neutron irradiation in the core of a nuclear power plant can change the material properties of stainless steel significantly. In this paper cold worked AISI 316 baffle bolts retrieved from Doel 1 PWR were investigated with the aim to assess the structural degradation due to neutron irradiation by analyzing microstructure, mechanical behavior and stress corrosion susceptibility. The baffle bolts had received neutron doses ranging from 6 to 59 dpa covering a major part of a nuclear power plant's lifetime. First, microstructural investigations were carried out to reveal the defect and dislocation density and the amount of void swelling. Then mechanical properties were determined using tensile tests and fracture toughness tests. The irradiation assisted stress corrosion cracking (IASCC) susceptibility was investigated by slow strain rate testing and crack growth rate testing. Results were compared with literature values and found to be in good agreement. Main conclusions were that void swelling was small even for the highest dpa values and that the fracture toughness values saturated above 15 dpa. The material was susceptible to IASCC as shown by SSRT and crack growth rate measurements exhibiting intergranular fracture morphology.

Interaction behavior between outer pipe and liner within offshore lined pipeline under axial compression

When transmitting highly corrosive offshore hydrocarbons, one economical approach is lining internally a thin corrosion resistance alloy (CRA) layer within an ordinary carbon steel pipe. Most commonly the liner is mechanically bonded to the outer pipe by mechanical expansion. The lined pipe is expected to make optimize usage of the two types of materials, providing significant corrosion and structural resistance. This study investigates full history interaction behaviors between the outer pipe and liner and the structural behaviors of the lined pipe under axial compression, through finite element analysis (FEA). Comprehensive finite element (FE) models are developed, where the manufacturing process, the non-linear material properties of stainless steel and the interactions between the constituent components are considered. The numerically determined failure modes, load-deformation histories and ultimate strengths are compared with those from tests. The interaction stress and axial loading histories of the specimen under axial compressions are studied, where the internal content pressure and external hydrostatic pressures are considered simultaneously. Confinement factor is suggested to ensure the structural reliability of the liner in engineering practice. Parametric studies are conducted to study the effects of the outer pipe strength, liner strength, outer pipe thickness and liner thickness on the structural behaviors of the axially loaded lined pipes.

Analytical behavior of carbon steel-concrete-stainless steel double-skin tube (DST) used in submarine pipeline structure

One type of submarine composite pipeline structure, with carbon steel-concrete-stainless steel (CCS) double-skin tube (DST), was introduced in this paper. This composite pipeline was expected to make optimal use of the three types of the materials, and provide significant structural and internal corrosion resistance. This study investigated the compressive and flexural behavior of the composite pipeline under internal content pressure and external hydrostatic pressure through finite element analysis (FEA). Finite element models were developed, where non-linear material properties of stainless steel and composite actions between constituent parts were considered. The models were verified through the comparisons between the numerically and experimentally determined results, in terms of load-deformation histories, failure modes and ultimate strength. Structural behaviors of the composite pipeline under pressures were compared with those without content and hydrostatic pressure. Parametric studies were carried out to investigate the effects of the outer carbon steel strength, inner stainless steel strength, concrete strength and hollow ratio on the compressive and flexural behaviors of the composite pipelines subjected to pressures.

Mechanical Response and Failure Evolution of 304L Stainless Steel under the Combined Action of Mechanical Loading and Laser Heating

Deformation and fracture properties of structural materials are greatly influenced by the factors like applied load, state of stress, and temperature. A precise prediction of the material properties of stainless steel at elevated temperature is necessary for determining the load-carrying capacity of structures under severe conditions. The present work reports the deformation and failure characteristics of 304L stainless steel subjected to combined laser heating and mechanical loading. The effect of main parameters on stress-strain, fracture characteristics, failure time, and temperature profile of specimens have been explored. Specimens were subjected to prescribed loading states, and then irradiated by a continuous wave fiber (1.08 µm) laser. The stress-strain curves indicated that the specimens experienced slight strain hardening in a specific temperature range prior to fracture. The specimen’s ultimate failure time is found to be reduced by increasing either laser power density or preload level. Fracture on a microscopic scale was predominantly ductile, comprising dimples as well as micro-void nucleation, growth, and coalescence. With the increase of laser power density, dimples rupture is the primary fracture mode, while with the increase of preload value, relatively more in-depth and severe deformation effects were observed. The description and characterization of 304L stainless steel failure under the simultaneous action of laser heating and tensile stress have been explored in detail.

Effect of laser scan strategy on material properties of stainless steel 630 by selective laser melting

Effect of laser scan strategy on material properties of stainless steel 630 by selective laser melting

Wire and arc additive manufactured steel: Tensile and wear properties

The present study systematically investigated the mechanical properties of wire-based (wire and arc additive manufacturing, known as WAAM) deposition of steel metals, both stainless steel 304 and mild steel ER70S. Graded material properties of stainless steel 304 were observed for wear and hardness in the direction of deposition and in Z height, due to variations in local thermal histories of the metal. Wear rates decreased significantly (p=5.6×10−12 by one-way ANOVA) along the length of the deposited material, from K=2.62x10−5mm3/Nm (+/− 2.32x10−6mm3/Nm), to K=0.63mm3x10−5mm3/Nm (+/−3.08x10-6mm3/Nm), whereas microhardness values increased significantly (p∼0 by one-way ANOVA) along the same path from μ=202.3 HV and σ=5.82 HV to 210.9 HV and σ=5.91 HV. The yield and ultimate strength, however, were not found to be statistically significantly different (p=0.55) along the direction of deposition for SS304. During wear testing, a grain refinement was observed directly beneath the wear scar in these materials in a focused ion beam channel observed under scanning electron microscopy. Additionally, no significant difference in yield strength was observed in printed mild steel (ER70S) between vertical and horizontal specimens. The observed graded mechanical properties in stainless steel 304 allow the opportunity for varying the processing conditions to design parts with locally optimized or functionally graded mechanical properties.

Influence of material properties of stainless steel on the ignition probability of flammable gas mixtures due to mechanical impacts

Grazing impact experiments of various types of stainless steels were performed in explosive atmospheres of hydrogen, acetylene, ethylene or propane with air. Depending on the gas mixture, kinetic energy of the impact, and applied stainless steel, the dominant ignition sources are either separated particles or hot friction surfaces. An influence of chromium content on the ignition probability was not found, although an increase in chromium content results in a reduction of the oxidizability of separated particles. Additionally, the influence of the material properties thermal conductivity, specific heat, density and hardness on the ignition probability of the hydrogen–air mixture was investigated. With increasing thermal conductivity a decreasing rate of ignitions was observed. In contrast, an influence of the physical properties specific heat, density and hardness on the ignitability was not found.

Elevated temperature material properties of stainless steel reinforcing bar

Corrosion of carbon steel reinforcing bar can lead to deterioration of concrete structures, especially in regions where road salt is heavily used or in areas close to sea water. Although stainless steel reinforcing bar costs more than carbon steel, its selective use for high risk elements is cost-effective when the whole life costs of the structure are taken into account. Considerations for specifying stainless steel reinforcing bars and a review of applications are presented herein. Attention is then given to the elevated temperature properties of stainless steel reinforcing bars, which are needed for structural fire design, but have been unexplored to date. A programme of isothermal and anisothermal tensile tests on four types of stainless steel reinforcing bar is described: 1.4307 (304L), 1.4311 (304LN), 1.4162 (LDX 2101®) and 1.4362 (2304). Bars of diameter 12mm and 16mm were studied, plain round and ribbed. Reduction factors were calculated for the key strength, stiffness and ductility properties and compared to equivalent factors for stainless steel plate and strip, as well as those for carbon steel reinforcement. The test results demonstrate that the reduction factors for 0.2% proof strength, strength at 2% strain and ultimate strength derived for stainless steel plate and strip can also be applied to stainless steel reinforcing bar. Revised reduction factors for ultimate strain and fracture strain at elevated temperatures have been proposed. The ability of two-stage Ramberg-Osgood expressions to capture accurately the stress-strain response of stainless steel reinforcement at both room temperature and elevated temperatures is also demonstrated.

Bearing factors of cold-formed stainless steel double shear bolted connections at elevated temperatures

A numerical investigation on double shear bolted connections of cold-formed stainless steel at elevated temperatures is described in this paper. A finite element model is developed in this study. The model was verified against stainless steel double shear bolted connection tests. It is shown that the finite element model is able to predict the test strengths and failure modes of the connections. Therefore, an extensive parametric study of 225 stainless steel double shear bolted connections at 5 different temperature levels was performed. Based on both the test and numerical results, bearing factors are proposed for the bearing strengths of stainless steel double shear bolted connections at elevated temperatures. Two sets of bearing factors are proposed based on the true plastic strains in the bolt hole and the bolt hole deformation. The connection bearing strengths obtained from the tests and finite element analysis were compared with the nominal strengths calculated using the current American, Australian/New Zealand and European specifications for stainless steel structures as well as the modified design rules in this study. In calculating the nominal strengths of the connections, the material properties of stainless steel obtained at elevated temperatures were used. It is shown that the modified design rules provided more accurate predictions compared to the current design predications for bearing strengths of stainless steel double shear bolted connections at elevated temperatures. The reliability of the current and modified design rules was evaluated using reliability analysis.

Development of ideal solution and validation of stiffness and strength by finite element method for truss-wall corrugated cellular solids

The objective of this study is to find the density, stiffness, and strength of truss-wall unit cell models. The diamond-corrugation, triangular-corrugation, and Navtruss-corrugation models are used for the unit cell. The ideal solutions derived for these are based on solidwall unit cell models and are developed using the Gibson-Ashby theory. To verify the ideal solutions of the models, the density, strength, and stiffness are simulated using ABAQUS software and compared with the ideal solutions on a log-log scale. The material properties of stainless steel 304 are applied. The diameter is 0.5 mm; the opening width is 0.5 mm; and the corrugation angle is 45°. Consequently, the relative Young’s modulus and relative yield strength of the truss-wall unit models are good matches for the ideal expectations. It may be possible to apply a truss-wall model to diverse fields such as transportation or biomedical applications as one of the open-cell cellular solids.

Preliminary Research of Truss-Wall Corrugated Cellular Solids

The objective of this study is to find the density, stiffness, and strength of truss-wall unit cell models. The diamond-corrugation, triangular-corrugation, and Navtruss-corrugation models are used for the unit cell. The ideal solutions derived for these are based on truss-wall unit cell models and are developed using the GibsonAshby theory. To verify the ideal solutions of the models, the density, strength, and stiffness are simulated using ABAQUS software and compared with the ideal solutions on a log-log scale. The material properties of stainless steel 304 are applied. The diameter is 0.5 mm; the opening width is 0.5 mm; and the corrugation angle is 45°. Consequently, the relative Youngs modulus and relative yield strength of the truss-wall unit models are good matches for the ideal expectations. It may be possible to apply a truss-wall model to diverse fields such as transportation or biomedical applications as one of the open-cell cellular solids.

Effects of Geometry and Material Properties on the Residual Stress of Glass-to-metal Seals in Solar Receiver Tubes

The solar receiver tube is a key component to convert the solar energy into thermal energy in parabolic trough solar power system. The residual stresses which are generated during the cooling process of glass-to-metal sealing significantly influence the reliability of receiver tube. In order to lower the seal failure probability, the effects of geometry and material properties of glass- to-metal seals on the residual stress are analyzed using finite element method in this paper. The effects of the material properties of stainless steel 304, stainless steel 430, Kovar on the sealing residual stress can be presented. Although each of these different sealing material combinations can have enough sealing strength, the glass-to-metal seals with larger tensile stresses can cause the failure of the receiver tube. Moreover, effects of geometry of the metal tube and the glass tube on the residual stress are also analyzed. The stress distributions in the glass side analyzed by the finite element method (FEM) were in agreement with the ones calculated by analytic solution (AS) approach. The X-ray measurement results also proved the validation of the FEM. The dangerous tensile stresses mainly occur at the glass-metal interface. The results of this study have important implications on the optimization of seal configuration in the solar receiver tubes.

Behavior of cold-formed stainless steel single shear bolted connections at elevated temperatures

The current design rules on bolted connections of cold-formed stainless steel structures are allowed for room (ambient) temperature condition only. Research on structural behavior of single shear bolted connections at elevated temperatures is limited. In this study, 100 single shear bolted connection specimens and 22 coupon specimens involving three different grades of stainless steel were conducted by using steady state test method in the temperature ranged from 200 to 950°C. The three different grades of stainless steel are austenitic stainless steel EN 1.4301 (AISI 304) and EN 1.4571 (AISI 316Ti having small amount of titanium) as well as lean duplex stainless steel EN 1.4162 (AISI S32101). Furthermore, different bolts arrangement was also considered in the investigation. Two main failure modes were observed in the single shear bolted connection tests, namely the net section tension and bearing failures. The test results were compared with the predicted strengths calculated from the American Specification, Australian/New Zealand Standard and European Codes for cold-formed stainless steel structures. In calculating the nominal strengths of the connections, the reduced material properties of stainless steel obtained at elevated temperatures were used. It is shown that the strengths of the single shear bolted connections predicted by the specifications are generally conservative at elevated temperatures. A similar tendency of reduction was found when compared the reduction factor of material properties with that of the deterioration of the bolted connection test strengths with the corresponding type of cold-formed stainless steel at elevated temperatures. The austenitic stainless steel type EN 1.4571 (AISI 316Ti) generally performed better than the other two stainless steel types at elevated temperatures.

Computing Simulation of the Influence of Plate Design, Material, and Screw Positioning on Biomechanical Behavior of Ulna Bone Plates

Throughout history, fractures have been treated by immobilization, traction, and internal fixation. Construction of a stabilization system composed of bone plate and screws combination depends on factors such as type of fracture, biomechanical behavior of stabilization system, and surgical preference. In this study, the influence of plate design, material properties, and screw placement was investigated through the use of Experimental Design and Finite Element simulation. A three dimensional model of the ulna bone was reconstructed from computer tomography images and a simple oblique fracture was simulated. The fracture was stabilized in different modes, using combinations of three different design plates with the material properties of stainless steel and titanium alloy fixed with three, four, and six screws. The biomechanical behavior was compared in terms of equivalent stress and total deformation. Results showed that the fixation mode and plate design have the largest influence on the biomechanical behavior of the bone-plate assembly.

Design of cold-formed stainless steel tubular joints at elevated temperatures

This paper describes the numerical investigation of cold-formed stainless steel tubular T-joints, X-joints and X-joints with chord preload at elevated temperatures. A series of finite element analysis was performed on stainless steel tubular joints. The tubular T- and X-joints were welded from cold-formed square and rectangular hollow sections as brace and chord members. The material properties of high strength stainless steel (duplex and high strength austenitic) and normal strength stainless steel (AISI 304) at elevated temperatures were carefully incorporated in the finite element models. An extensive numerical study of 450 specimens consists of 20 T-joints, 10 X-joints and 20 X-joints with chord preload at different temperatures ranged from 22 to 870°C was conducted. The joint strengths, failure modes and load-deformation curves of stainless steel tubular joints at elevated temperatures were obtained from the finite element analysis. The numerical results were compared with the design strengths calculated from the existing design rules for stainless steel tubular joints at normal room temperature (ambient temperature) by using the material properties of stainless steel tubes at elevated temperatures. In the calculation of the joint strengths, the reduced material property of 0.2% proof stress was used due to the deterioration of material at elevated temperatures. Furthermore, design equations for cold-formed stainless steel tubular T- and X-joints at elevated temperatures are proposed by introducing a temperature factor (ξT). A reliability analysis was performed to assess the existing and proposed design equations.

Prediction of Welding Distortion in 304 Stainless Steel

Prediction of welding distortion of stainless steel welding joint in reasonable time is meaningful in welding industry. In this paper, a three dimensional thermo-elastic-plastic finite element method (FEM) is developed to precisely predict welding distortion on bead on plate welding with 304 stainless steel. Meanwhile, the corresponding experiments are carried out to validate the predicted results. Research results show the predicted results by FEM match the experimental results very well. In the condition of different welding heat input, the welding heat input play an important role on welding distortion. While, material properties of stainless steel play a larger role on welding distortion when welding heat input is same. Further, for bead on plate welding of thin plate, both large distortion theory and small distortion theory are computed. The results show that using large distortion theory is more accurate in prediction welding distortion on thin plate welding.

Numerical Investigation of the Interaction of Local and Overall Buckling of Stainless Steel I-Columns

This report describes research carried out at the University of Sydney to study the interaction of local and overall buckling in stainless steel I-columns. A finite-element model was constructed using the commercially available ABAQUS software package, taking into account the specific material properties of stainless steel: nonlinear stress-strain behavior, anisotropy, and enhanced corner properties as a result of cold working. The model was verified against the experimental data presented in the companion paper and yielded good predictions of the behavior and ultimate capacity of the test specimens. The finite-element model was subsequently used in parametric studies, which covered the practical ranges of overall and cross-sectional slenderness values. The current Australian/New Zealand, North American, and European design guidelines for stainless steel were assessed using the available experimental and numerical data. It is demonstrated that the current design standards fail to appropriately account for the local overall interaction effect in stainless steel I-columns.