Design against Fatigue of Super Duplex Stainless Steel Structures Fabricated by Wire Arc Additive Manufacturing Process

Additive manufacturing (AM) is increasingly used to make complex components for a wide spectrum of applications in engineering, medicine and dentistry. Wire arc additive manufacturing (WAAM), as one of AM processes, utilises electric arc and metal wire to fabricate fully dense and heavy metal parts at relatively low costs and high-energy efficiencies. WAAM was successfully applied in the production of several welding-based metal structures. Recently, there was a growing interest in WAAM processing of super duplex stainless steels (SDSS) due to their high strength and excellent corrosion resistance, which make them the prime choice for load-bearing structures in marine applications. Although a number of studies investigated the microstructural and mechanical properties of WAAM-processed SDSS components, little is known regarding their fatigue performance, which is critical in engineering design. This study reports on the outcomes of fatigue tests and fracture surface fractography of WAAM-processed SDSS. The results obtained indicate a significant anisotropy of fatigue properties and fatigue crack initiations resulting from internal defects rather than surface flaws. Based on these experimental results, we suggest an effective design methodology to improve the fatigue life of the WAAM-fabricated SDSS components. We also indicate that post-manufacturing surface treatments should not be underlined for the enhanced fatigue resistance of WAAM-processed SDSS structures.

Download Full-text

Geometry and Distortion Prediction of Multiple Layers for Wire Arc Additive Manufacturing with Artificial Neural Networks

Applied Sciences ◽

10.3390/app11104694 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4694

Author(s):

Christian Wacker ◽

Markus Köhler ◽

Martin David ◽

Franziska Aschersleben ◽

Felix Gabriel ◽

...

Keyword(s):

Additive Manufacturing ◽

Welding Process ◽

High Energy ◽

Welding Distortion ◽

Direct Energy Deposition ◽

Direct Energy ◽

Industrial Use ◽

Artificial Neural ◽

Artificial Neural Network Ann ◽

Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process with high deposition rates, but deformation and distortion can occur due to the high energy input and resulting strains. Despite great efforts, the prediction of distortion and resulting geometry in additive manufacturing processes using WAAM remains challenging. In this work, an artificial neural network (ANN) is established to predict welding distortion and geometric accuracy for multilayer WAAM structures. For demonstration purposes, the ANN creation process is presented on a smaller scale for multilayer beads on plate welds on a thin substrate sheet. Multiple concepts for the creation of ANNs and the handling of outliers are developed, implemented, and compared. Good results have been achieved by applying an enhanced ANN using deformation and geometry from the previously deposited layer. With further adaptions to this method, a prediction of additive welded structures, geometries, and shapes in defined segments is conceivable, which would enable a multitude of applications for ANNs in the WAAM-Process, especially for applications closer to industrial use cases. It would be feasible to use them as preparatory measures for multi-segmented structures as well as an application during the welding process to continuously adapt parameters for a higher resulting component quality.

Download Full-text

Fatigue Behaviour of Friction Stir Welded Steel Joints

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.1488 ◽

2014 ◽

Vol 891-892 ◽

pp. 1488-1493 ◽

Cited By ~ 11

Author(s):

José Azevedo ◽

Virgínia Infante ◽

Luisa Quintino ◽

Jorge dos Santos

Keyword(s):

Base Material ◽

Welding Process ◽

Steel Structures ◽

Fatigue Behaviour ◽

Fatigue Tests ◽

Fatigue Properties ◽

Welded Steel ◽

Shipbuilding Industry ◽

Friction Stir ◽

Steel Joints

The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.

Download Full-text

Additive manufacturing of Inconel625-HSLA Steel functionally graded material by wire arc additive manufacturing

Metallurgical Research & Technology ◽

10.1051/metal/2021063 ◽

2021 ◽

Vol 118 (5) ◽

pp. 502

Author(s):

Jiarong Zhang ◽

Xinjie Di ◽

Chengning Li ◽

Xipeng Zhao ◽

Lingzhi Ba ◽

...

Keyword(s):

Additive Manufacturing ◽

Chemical Composition ◽

Primary Dendrite ◽

Hsla Steel ◽

High Strength ◽

Phase Evolution ◽

Functionally Graded ◽

Graded Materials ◽

Graded Material ◽

Wire Arc Additive Manufacturing

Functional graded materials (FGMs) have been widely applied in many engineering fields, and are very potential to be the substitutions of dissimilar metal welding joints due to their overall performance. In this work, the Inconel625-high-strength low-alloy (HSLA) Steel FGM was fabricated by wire arc additive manufacturing (WAAM). The chemical composition distribution, microstructure, phase evolution and mechanical properties of the FGM were examined. With the increasing of HSLA Steel, the chemical composition appeared graded distribution, and the primary dendrite spacing was largest in graded region with 20%HSLA Steel and then gradually decreased. And the main microstructure of the FGM transformed from columnar dendrites to equiaxed dendrites. Laves phase precipitated along dendrites boundary when the content of HSLA Steel was lower than 70% and Nb-rich carbides precipitated when the content of HSLA Steel exceeded to 70%. Microhardness and tensile strength gradually decreased with ascending content of HSLA Steel, and had a drastic improvement (159HV to 228HV and 355Mpa to 733Mpa) when proportion of HSLA Steel increased from 70% to 80%.

Download Full-text

The Effects of Notches on the Fatigue Strength of Steel Structures

MATEC Web of Conferences ◽

10.1051/matecconf/201927902001 ◽

2019 ◽

Vol 279 ◽

pp. 02001

Author(s):

Pavol Juhas

Keyword(s):

Fatigue Strength ◽

Steel Structures ◽

Life Time ◽

Fatigue Tests ◽

Constructional Steel ◽

Fatigue Properties ◽

Stress Range ◽

Time Data ◽

Butt Weld ◽

Applied Loading

The paper informs about the research devoted to load–carrying capacity, fatigue strength and life–time of welded steel structures. The experimental programme comprises fatigue tests of constructional steel S380 (QStE 380 TM). In the first stage 35 specimens were tested: 9 without any weld connection, 14 with transverse milled butt weld and 12 with transverse rough butt weld. The applied loading in this stage was harmonic with constant stress range. All tests ended by fatigue failure. The second part of the research comprised the tests with block simulated loading with variable stress range. The third part applied continuous recording of stresses and strains in critical sections, that gave information about the local failure development in time. Data sets have allowed to define fatigue properties of investigated steel and degradation effects of used welds including the initiation time of remarkable changes in stress-strain stage expressed through the total kinetic energy. The degradation effects of welds on fatigue strength of structural steels were confirmed, especially it was the case of rough welds - without additional milling. Additionally, the differences in the fatigue curves inclinations were indicated that can depend on the level of fatigue strength. The applied approach gives an opportunity to analyse the effects of actual loading process and improve the methodology of judgement of fatigue strength and life-time of steel elements. Reasonable fatigue properties of this steel suggest it for using also in severe technology structures.

Download Full-text

Monotonic and Fatigue Properties of Steel Material Manufactured by Wire Arc Additive Manufacturing

Applied Sciences ◽

10.3390/app10155238 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5238 ◽

Cited By ~ 2

Author(s):

Michael Wächter ◽

Marcel Leicher ◽

Moritz Hupka ◽

Chris Leistner ◽

Lukas Masendorf ◽

...

Keyword(s):

Additive Manufacturing ◽

Material Properties ◽

Elevated Temperatures ◽

Tensile Tests ◽

Fatigue Properties ◽

Practical Applications ◽

Steel Material ◽

Characteristic Values ◽

The One ◽

Wire Arc Additive Manufacturing

In this study, the monotonic and cyclic material properties of steel material of medium static strength produced additively in the wire arc additive manufacturing (WAAM) process were investigated. This investigated material is expected to be particularly applicable to the field of mechanical engineering, for which practical applications of the WAAM process are still pending and for which hardly any characteristic values can be found in the literature so far. The focus of the investigation was, on the one hand, to determine how the material characteristics are influenced by the load direction in relation to the layered structure and, on the other hand, how they are affected by different interlayer temperatures. For this purpose, monotonic tensile tests were carried out at room temperature as well as at elevated temperatures, and the cyclic material properties were determined. In addition, the hardness of the material and the residual stresses induced during production were measured and compared. In addition to the provision of characteristic properties for the investigated material, it was aimed to determine the extent to which the interlayer temperature influences the strength characteristics, since this can have a considerable influence on the production times and, thus, the economic efficiency of the process.

Download Full-text

Study on Micro-Mechanism of Crack Initiation and Propagation Induced by Inclusion in Ultra-High Strength Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.353-358.1185 ◽

2007 ◽

Vol 353-358 ◽

pp. 1185-1190 ◽

Cited By ~ 4

Author(s):

Yan Ping Zeng ◽

Hong Mei Fan ◽

Xi Shu Wang ◽

Xi Shan Xie

Keyword(s):

Crack Initiation ◽

High Strength Steel ◽

Harmful Effect ◽

High Strength Steels ◽

High Strength ◽

Fatigue Tests ◽

Fatigue Properties ◽

Crack Initiation And Propagation ◽

Initiation And Propagation ◽

Ultra High Strength Steel

Specially designed SEM in-situ tensile and fatigue tests have been conducted to trace the entire process of crack initiation and propagation till fracture in an ultra-high strength steel MA250. TiN is a typical inclusion and its average size is in the range of 8~10μm in MA250 steel. The micro-mechanism of the effect of TiN inclusion on crack initiation and propagation at tensile and fatigue tests both have been studied in detail. Experimental results show the harmful effect of TiN on tensile and fatigue properties both. This work is helpful to establish the practical life prediction model for the characteristic inclusion parameters in ultra-high strength steel components. It also enlightens us to eliminate TiN in the further development of ultra-high strength steels.

Download Full-text

Mechanical properties of wire and arc additively manufactured high-strength steel structures

Welding in the World ◽

10.1007/s40194-021-01204-1 ◽

2021 ◽

Author(s):

Johanna Müller ◽

Jonas Hensel ◽

Klaus Dilger

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Yield Strength ◽

High Strength Steel ◽

Energy Input ◽

High Strength ◽

Accelerated Cooling ◽

Active Cooling ◽

Wire Arc Additive Manufacturing ◽

Interpass Temperature

AbstractAdditive manufacturing with steel opens up new possibilities for the construction sector. Especially direct energy deposition processes like DED-arc, also known as wire arc additive manufacturing (WAAM), is capable of manufacturing large structures with a high degree of geometric freedom, which makes the process suitable for the manufacturing of force flow-optimized steel nodes and spaceframes. By the use of high strength steel, the manufacturing times can be reduced since less material needs to be deposited. To keep the advantages of the high strength steel, the effect of thermal cycling during WAAM needs to be understood, since it influences the phase transformation, the resulting microstructure, and hence the mechanical properties of the material. In this study, the influences of energy input, interpass temperature, and cooling rate were investigated by welding thin walled samples. From each sample, microsections were analyzed, and tensile test and Charpy-V specimens were extracted and tested. The specimens with an interpass temperature of 200 °C, low energy input and applied active cooling showed a tensile strength of ~ 860–900 MPa, a yield strength of 700–780 MPa, and an elongation at fracture between 17 and 22%. The results showed the formation of martensite for specimens with high interpass temperatures which led to low yield and high tensile strengths (Rp0.2 = 520–590 MPa, Rm = 780–940 MPa) for the specimens without active cooling. At low interpass temperatures, the increase of the energy input led to a decrease of the tensile and the yield strength while the elongation at fracture as well as the Charpy impact energy increased. The formation of upper bainite due to the higher energy input can be avoided by accelerated cooling while martensite caused by high interpass temperatures need to be counteracted by heat treatment.

Download Full-text

Effects of Solution Treatment on Laser Welding of Ti–6Al–4V Alloy Plate Produced through Wire Arc Additive Manufacturing

Metals ◽

10.3390/met10101310 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1310

Author(s):

Mingfang Xu ◽

Yuhua Chen ◽

Timing Zhang ◽

Huaibo Deng ◽

Di Ji

Keyword(s):

Tensile Strength ◽

Additive Manufacturing ◽

Laser Beam Welding ◽

Solution Treatment ◽

High Strength ◽

Travel Speed ◽

Alloy Plate ◽

Weave Structure ◽

The Difference ◽

Wire Arc Additive Manufacturing

Laser beam welding (LBW) had been successfully applied to the welding of Ti–6Al–4V plates by wire arc additive manufacturing. The effects of solution treatment on microstructure, tensile properties, and microhardness after LBW in different deposition directions were studied. When the wire speeding was 3 m/min and travel speed was 0.36 m/min, the difference in mechanical properties was related to the anisotropy of the microstructure. The long columnar grain along the building direction could provide an α path with a large aspect ratio and high elongation. More grain boundaries are present along the scanning direction than in others, showing high strength. The microstructure of the as-deposited condition mainly consists of coarse prior-β grains, partial basket-weave structure, and numerous martensite α′ phase. In LBW without solution treatment, the microstructure of the welds mainly consists of a large amount of martensite α′ and a small amount of basket-weave structure. The weld had high strength and hardness. The tensile strength was between 930 and 970 MPa. The hardness was between 415 and 456 HV. The elongation ranged from 5% to 7%. Afterwards, the temperature was maintained at 870 °C for 2 h, cooled to 600 °C in the furnace for 1 h, and finally air cooled to room temperature. The martensite α′ was almost completely transformed into platelet α. The microstructure of the welds mainly consists of partial β grains, thimbleful martensite α′, and a large of α path. The strength and hardness of the welds were reduced. The tensile strength is between 910 and 950 MPa. The hardness was between 398 and 445 HV. However, the elongation was significantly improved, and the elongation ranged from 10% to 12%.

Download Full-text

Experimental Study on Steel to FRP Bonded Lap Joints in Marine Applications

Advances in Materials Science and Engineering ◽

10.1155/2015/164208 ◽

2015 ◽

Vol 2015 ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

Çiçek Özes ◽

Nurhan Neşer

Keyword(s):

Surface Roughness ◽

Adhesive Bonding ◽

Weight Ratio ◽

Steel Structures ◽

High Strength ◽

Lap Joints ◽

Bonded Joints ◽

Bonding Performance ◽

Marine Industry ◽

Marine Applications

Steel structures coated with fiber-reinforced polymer (FRP) composites have gained wide acceptance in marine industry due to their high strength-to-weight ratio, good protection from environmental degradation, and impact loads. In this study, adhesive bonding performance of single-lap bonded joints composed of steel coated with FRP has been investigated experimentally for three different surface roughness and two epoxy types. Single-lap bonded joints have been tested under tensile loading. The adhesive bonding performance has been evaluated by calculating the strain energy values. The results reveal that the surface roughness of steel has a significant effect on the bonding performance of steel to FRP combinations and the performance of the resin can be improved by using the primer in an economical way.

Download Full-text