An Experimental Study on the Fatigue of Structural Steels with Various Welding Details

2008 ◽  
Vol 385-387 ◽  
pp. 593-596
Author(s):  
Byeong Choon Goo
Keyword(s):  
Experimental Data ◽  
Fatigue Strength ◽  
Structural Steel ◽  
Fatigue Tests ◽  
Structural Steels ◽  
Parent Material ◽  
Key Characteristics ◽  
Load Carrying ◽  
Weld Toe ◽  
Ground Load

A structural steel should satisfy various properties under varied conditions. Fatigue strength is one of them. When structural steels are used in the form of welded joints, fatigue strength is one of the key characteristics that should be considered. In this study, comprehensive fatigue tests of a structural steel with yielding strength of about 350 MPa and tensile strength of about 520 MPa were carried out. First, a lot of specimens: parent material plates, butt welded specimens with reinforcement removed, as-welded plates, plates with weld toe ground, load-carrying cruciform, non load-carrying cruciform, plates with transverse fillet welded rib, etc were prepared and tested. S-N curves for the above specimens were compared and analyzed. Secondly, some life-size rectangular beams were fabricated by welding and tested. It is found that annealing is detrimental to fatigue strength rather than beneficial. The experimental data and results may be used usefully by engineers.

scholarly journals Influence Of Large Non-Metallic Inclusions On Bending Fatigue Strength Hardened And Tempered Steels

2015 ◽  
Vol 15 (3) ◽  
pp. 33-40
Author(s):  
T. Lipiński ◽  
A. Wach ◽  
E. Detyna
Keyword(s):  
Fatigue Strength ◽  
Structural Steel ◽  
Treatment Options ◽  
Fatigue Tests ◽  
Relative Volume ◽  
Heat Processing ◽  
Industrial Plant ◽  
Boron Steel ◽  
Metallic Inclusions ◽  
Steel Sections

Abstract The article discusses the effect of large oxide impurities (a diameter larger than 10 μm in size) on the fatigue resistance of structural steel of high purity during rotary bending. The study was performed on 7 heats produced in an industrial plant. The heats were produced in 140 ton electric furnaces. All heats were desulfurized. The experimental material consisted of semi-finished products of high-grade, carbon structural steel with: manganese, chromium, nickel, molybdenum and boron. Steel sections with a diameter of 18 mm were hardened from austenitizing by 30 minutes in temperature 880°C and tempered at a temperature of 200, 300, 400, 500 and 600°C for 120 minutes and air-cooled. The experimental variants were compared in view of the heat treatment options. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were statistical processed and presented in graphic form. This paper discusses the results of the relative volume of large impurities, the fatigue strength for various heat processing options.

Effect of Weld Geometry on the Fatigue Behaviour of Umbilical Super Duplex Stainless Steel Tubes

2017 ◽  
Author(s):  
Hauwa Raji ◽  
Jamie Fletcher Woods
Keyword(s):  
Stainless Steel ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Super Duplex Stainless Steel ◽  
Steel Tubes ◽  
Weld Geometry ◽  
Weld Profile ◽  
Weld Toe ◽  
Toe Angle

The fatigue behavior of welded components is complicated by many factors intrinsic to the nature of welded joints. The mechanical properties of the material, the welding process and position, the type and geometry of the weld and the residual stress distribution across the weld are a few factors affecting fatigue behavior. Published studies [1, 2] have shown that weld geometry is significantly important in determining the fatigue strength of the weld. For a given weld geometry, the fatigue strength is determined by the severity of the stress concentration at the weld toe or at weld defects and by the soundness of the weld metal. The effect of external weld geometry profile on the fatigue behavior of welded small bore super duplex umbilical steel tubes is investigated. Root cause analysis consisting of fractography, metallography and weld profile measurement is carried out on pairs of fatigue failure samples which were tested at the same stress range but failed at significantly different number of cycles. The samples are selected from Technip Umbilicals Ltd (TU) fatigue database. Following the failure analysis, weld geometric profile measurements are performed on fatigue test samples that were prepared for testing. The weld profile was measured in terms of the external weld cap height, weld width and external linear misalignment. Axial fatigue tests are carried out on these samples which are pre-strained before test to simulate the plastic bending cycles typically experienced during the manufacturing and installation processes prior to operational service. The fatigue tests results are interrogated together with the measured geometric data to identify trends and anomalies. Key weld geometric fatigue performance criteria are subsequently identified. For the welded super duplex stainless steel (SDSS) tubes studied, the height of the weld and the weld toe angle provided the best correlation with fatigue life — shorter lives were obtained from specimens with the highest weld aspect ratio (weld height to width) and lowest weld toe angle.

scholarly journals Usage of Ti-surface-modified filler material to increase the joint strength of High-Strength Low Alloyed (HSLA) steels under different load types

2020 ◽  
Vol 2 (12) ◽  
Author(s):  
Kai Treutler ◽  
Volker Wesling
Keyword(s):  
Dynamic Load ◽  
Base Material ◽  
High Strength ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Structural Steels ◽  
Titanium Coating ◽  
Fine Grained ◽  
Weld Toe ◽  
Load Types

AbstractWelding-related loss of strength, especially in the case of fatigue, significantly reduces the range of applications for high-strength fine-grained structural steels. In order to counteract this situation, the aim of the work is to increase the strength of welded joints made of high-strength fine-grained structural steels by using coated welding consumables. This is described using the example of a titanium coating for quasi-static and abrupt dynamic load and fatigue. The thermomechanical rolled fine-grained structural steel S700MC is used as the base material, using a welding filler of the same type. MAG welding was used to produce the fillet welds on a T-joint. In addition to tensile tests at four different load speeds up to 2 m/s, the results of fatigue tests are presented. In addition, the microstructure of the weld seams is examined by metallographic methods and the scanning electron microscope. A comparison with two joints from an unmodified variant and another steel grade with comparable properties (S690QL) serves to classify the results. It is shown that the use of modified filler metals has a significant influence on the overall strength of the welded joint due to the rounding of the weld toe. Thus, the fatigue strength can be increased by around 50%. In addition, the strength under sudden dynamic load can be increased by 10%.

scholarly journals Use of the experimental modal analysis for analytical lifetime estimation of a bogie frame

2018 ◽  
Vol 178 ◽  
pp. 06018
Author(s):  
Ion Manea ◽  
Ioan Sebesan ◽  
Mihai Matache ◽  
Gabriel Prenta ◽  
Catalin Firicel
Keyword(s):  
Experimental Data ◽  
Fatigue Strength ◽  
Modal Analysis ◽  
Analytical Model ◽  
Structural Model ◽  
Fatigue Tests ◽  
Experimental Modal Analysis ◽  
Finite Elements Analysis ◽  
Interaction Forces ◽  
Bogie Frame

The fatigue strength validation by tests of the railway bogie frames requires existence of an expensive laboratory and a long time for testing of about 6 to 10 months. Considering these aspects, the European norms admit that fatigue tests can be replaced by finite elements analysis (FEA), with the condition that analytical model to be correctly realized and validated by tests. Experimental modal analysis (EMA) provides a powerful tool for validation of the FEA model by experimental data. The article presents an application for assessment of the fatigue strength of a three-axle locomotive bogie frame. Using Ansys, was carried out the structural analysis of the bogie frame, resulting the modal model characterized by the modal parameters: Eigen frequencies and Eigen shapes. The analytical model was validated by an EMA application carried out on the bogie frame and correlation analysis of the EMA and FEA models. Using a special measuring wheel set, were determined the wheelrail interaction forces for various locomotive running conditions. The analytical structural model, validated through experimental data, and the data files containing the wheel-rail interaction forces, constitutes the input data for the nCode program that evaluates the bogie frame lifetime using appropriate stress curves and a recognized accumulation of damage hypothesis, e.g. the Palmgren-Miner.

Effect of Vibration during Welding on the Fatigue Strength of Structural Steel Weldments

2007 ◽  
Vol 124-126 ◽  
pp. 1329-1332 ◽  
Author(s):  
Chin Hyung Lee ◽  
Gab Chul Jang ◽  
Hyun Chan Park ◽  
Kyong Ho Chang
Keyword(s):  
Fatigue Strength ◽  
Structural Steel ◽  
Arc Welding ◽  
Mechanical Vibration ◽  
Base Material ◽  
Fatigue Tests ◽  
Steel Bridge ◽  
Flux Cored Arc Welding ◽  
Service Load ◽  
Improve Reliability

During repair welding of steel bridge under service load, vibration occurs due to the dynamic loads like wind and vehicles, etc. However, the effect of vibration during welding on the fatigue strength of weldments is not yet clearly understood. In this paper, the effect of vibration during welding on the fatigue strength of structural steel weldments was investigated in order to improve reliability in the repair welded joints of steel bridge. The base material used in this investigation was SM 490A steel of weldable grade. Flux Cored Arc Welding (FCAW) process was used to fabricate the single ‘V’ butt joints. Welding was performed on the steel under the mechanical vibration of given frequency. The applied frequency was resonant frequency. Also, weldments under no vibration during welding were prepared. Fatigue tests were conducted using a servo hydraulic controlled 50tonf capacity UTM with a frequency of 5Hz under constant amplitude loading. Effect of vibration during welding on the fatigue strength of weldments was analyzed in detail.

FATIGUE STRENGTH ASSESSMENT OF THE FILLET WELDED CRUCIFORM JOINTS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4225-4230
Author(s):  
DAE-JIN KIM ◽  
CHANG-SUNG SEOK ◽  
JAE-MEAN KOO
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Hot Spot ◽  
Fatigue Tests ◽  
Structural Stress ◽  
Hot Spot Stress ◽  
Cruciform Joints ◽  
Strength Assessment ◽  
Load Carrying ◽  
Cruciform Joint

In this study, fatigue tests to obtain S - N curves and FE analyses to obtain structural stress concentration factors were conducted for two types of fillet welded cruciform joints, that is, load-carrying and non load-carrying types. The obtained S - N curve of the load-carrying joint was changed to that based on hot-spot stress. As a result, the S - N curve of the load-carrying joint based on hot-spot stress almost coincided with that of the non load-carrying joint based on nominal stress. The fatigue strength of a welded joint which has a different geometry from that of the non load-carrying cruciform joint but the same bead profile as that of the non load-carrying cruciform joint could be estimated by using both the structural stress concentration factor at the weld toe position obtained from FEM and the nominal S - N curve of the non load-carrying cruciform joint from experiment.

scholarly journals Effect of Aqueous Environment on High Cycle and Very-High-Cycle Fatigue Behavior for a Structural Steel

2011 ◽  
Vol 462-463 ◽  
pp. 355-360
Author(s):  
You Shi Hong ◽  
Gui An Qian
Keyword(s):  
Fatigue Strength ◽  
Structural Steel ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Aqueous Environment ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

In this paper, rotary bending fatigue tests for a structural steel were performed in laboratory air, fresh water and 3.5% NaCl aqueous solution, respectively, thus to investigate the influence of environmental media on the fatigue propensity of the steel, especially in high cycle and very-high-cycle fatigue regimes. The results show that the fatigue strength of the steel in water is remarkably degraded compared with the case tested in air, and that the fatigue strength in 3.5% NaCl solution is even lower than that tested in water. The fracture surfaces were examined to reveal fatigue crack initiation and propagation characteristics in air and aqueous environments.

Evaluation of Fatigue Strength Improvement of Ship Structural Details by Weld Toe Grinding

2006 ◽  
Vol 324-325 ◽  
pp. 1079-1082 ◽  
Author(s):  
Myung Hyun Kim ◽  
Sung Won Kang ◽  
Jae Myung Lee ◽  
Wha Soo Kim
Keyword(s):  
Fatigue Strength ◽  
Surface Defects ◽  
Quantitative Measure ◽  
Fatigue Tests ◽  
Weld Bead ◽  
Fatigue Strength Improvement ◽  
Structural Details ◽  
Weld Toe ◽  
Loading Modes ◽  
Strength Improvement

In order to strengthen or repair the welded structural members or fatigue damaged areas, various surface treatment methods such as grinding, shot peening and/or hammer peening are commonly employed among other methods available. While the weld toe grinding method is known to give 3~4 times of fatigue strength improvement, this improvement may significantly vary according to weld bead shapes and loading modes. In this context, a series of fatigue tests is carried out for three types of test specimens that are typically found in ship structures. Weld burr grinding is carried out using an electric grinder in order to remove surface defects and improve weld bead profiles. The test results are compared with the same type of test specimen without applying the fatigue improvement technique in order to obtain a quantitative measure of the fatigue strength improvement. Moreover, structural stress method is employed to evaluate the effectiveness of the method in evaluating the fatigue strength improvement of welded structures.

Fatigue Strength Evaluation of the Load-Carrying Cruciform Fillet Welded Joints Using Hot-Spot Stress

2006 ◽  
Vol 324-325 ◽  
pp. 1281-1284 ◽  
Author(s):  
Byeong Wook Noh ◽  
Jung I. Song ◽  
Sung In Bae
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Hot Spot ◽  
Plate Thickness ◽  
Structural Stress ◽  
Leg Length ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Load Carrying ◽  
Weld Toe

In this study, fatigue strength of load-carrying cruciform fillet welded joints were evaluated using a new method proposed by Yamada, for geometric or structural stress in welded joint, that is, one-millimeter stress below the surface in the direction corresponding to the expected crack path. Validity of the method is verified by analyzing fatigue test results for load-carrying cruciform welded specimens has different size of weld toe radius, leg length and plate thickness reported in literature. Structural stress concentration factor for 1mm below the surface was calculated by finite element analysis for each specimen respectively. When compared to the basic fatigue resistance curve offered by BS7608, the one-millimeter stress method shows conservative evaluation for load-carrying cruciform fillet welded joints.

Enhancement of Welded Joints Productivity Effect of Welding Position on Fatigue Strength

2011 ◽  
Vol 110-116 ◽  
pp. 202-209
Author(s):  
Mahdi Kazemi Hatami ◽  
Amir Masoud Amini ◽  
Kamran Fallahi
Keyword(s):  
Fatigue Strength ◽  
International Institute ◽  
Welded Structures ◽  
Weld Geometry ◽  
Load Carrying ◽  
Weld Toe ◽  
Reference Curves ◽  
Fatigue Evaluation ◽  
Cruciform Joint ◽  
Welding Position

Welded structures are frequently used in today’s metal industry. Since fatigue is still one major reason of failures, investigation in this field is of interest to engineers. In this study experimental methods are employed to perform a fatigue evaluation concerning local weld geometry. The emphasis was on quantifying the weld toe radius as a feature in quantification of weld quality. Three different welding positions which have been led to different toe radii were analyzed. Each batch contained 12 specimens manufactured in cruciform joint and has been tested in non-load carrying status. Finally, the results of tests were compiled in Wöhler (S-N) curve and compared to reference curves introduced by IIW (International Institute of Welding). Results of this study show that local weld geometry has remarkable influence on strength of welded structures. It can be concluded that specimens with larger toe radii had more fatigue strength – as it was expected from the theory.

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