Multi-scale residual stress prediction for selective laser melting of high strength steel considering solid-state phase transformation

2022 ◽  
Vol 146 ◽  
pp. 107578
Author(s):  
Yong Chen ◽  
Yan Liu ◽  
Hui Chen ◽  
Ying Wu ◽  
JingQing Chen ◽  
...  
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Solid State ◽  
Selective Laser Melting ◽  
High Strength Steel ◽  
High Strength ◽  
Laser Melting ◽  
Multi Scale ◽  
Stress Prediction ◽  
Solid State Phase Transformation

scholarly journals Analysis of a High-Strength Steel SMAW Database

2021 ◽  
Vol 100 (12) ◽  
pp. 410-420
Author(s):  
KRISHNA SAMPATH ◽  
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Carbon Content ◽  
High Strength Steel ◽  
High Strength ◽  
Regression Equations ◽  
Austenite Decomposition ◽  
Impact Properties ◽  
Transformation Temperatures ◽  
Solid State Phase Transformation

Recently, Dr. Glyn M. Evans posted a large shielded metal arc (SMA) weld metal (WM) database on the ResearchGate website (researchgate.net). This database contains more than 950 WM compositions, along with their respective WM tensile and Charpy V-notch (CVN) impact properties. In particular, the CVN impact properties list the test temperatures that achieved 28 and 100 J impact energy for each WM composition. While the availability of this SMA WM database is a valuable and rare gift to the welding community, how could the welding community analyze this database to gain valuable insights? This paper utilizes a constraints-based model (CBM) as a simple and effective framework to organize and analyze this very large Fe-C-Mn SMA WM database. A CBM is built on the metallurgical principle that one needs to lower relevant solid-state phase transformation (i.e., austenite decomposition) temperatures to improve WM strength and fracture toughness while simultaneously reducing carbon content and Yurioka’s carbon equivalent number (CEN) to improve the weldability of high-strength steels. To this end, a CBM identifies and simultaneously solves several statistical (regression) equations that relate the chemical composition of high-strength steel WM with Yurioka’s CEN and selected solid-state phase transformation temperatures related to austenite decomposition. The results of the current effort demonstrate that the analysis of Evans’s shielded metal arc welding database using a CBM as a framework reaffirms that controlling carbon content, the value of the CEN, and calculated solid-state phase transformation temperatures, particularly the difference between the calculated Bs (bainite-start) and Ms (martensite-start) temperatures, is critical to developing and identifying high-performance, high-strength steel welding electrodes. A dual approach that manipulates the contents of principal alloy elements such as C, Mn, Ni, Cr, Mo, and Cu, and adds controlled amounts of Ti, B, Al, O, and N, appears to offer the best means to lower relevant solid-state phase transformation temperatures to produce high-strength and high-toughness WMs.

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

Simple Benchmark Problems for Finite Element Weld Residual Stress Simulation

2013 ◽  
Author(s):  
Mike C. Smith ◽  
Steve Bate ◽  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Phase Transformation ◽  
Solid State ◽  
Residual Stresses ◽  
Benchmark Problems ◽  
Transient Temperature ◽  
Beam Specimen ◽  
Weld Residual Stress ◽  
Solid State Phase Transformation

Finite element methods are used increasingly to predict weld residual stresses. This is a relatively complex use of the finite element method, and it is important that its practitioners are able to demonstrate their ability to produce accurate predictions. Extensively characterised benchmark problems are a vital tool in achieving this. However, existing benchmarks are relatively complex and not suitable for analysis by novice weld modellers. This paper describes two benchmarks based upon a simple beam specimen with a single autogenous weld bead laid along its top edge. This geometry may be analysed using either 3D or 2D FE models and employing either block-dumped or moving heat source techniques. The first, simpler, benchmark is manufactured from AISI 316 steel, which does not undergo solid state phase transformation, while the second, more complex, benchmark is manufactured from SA508 Cl 3 steel, which undergoes solid state phase transformation during welding. A number of such beams were manufactured using an automated TIG process, and instrumented with thermocouples and strain gauges to record the transient temperature and strain response during welding. The resulting residual stresses were measured using diverse techniques, and showed markedly different distributions in the austenitic and ferritic beams. The paper presents the information necessary to perform and validate finite element weld residual stress simulations in both the simple austenitic beam and the more complex ferritic beam, and provides performance measures for the austenitic beam problem.

Predicting Welding Residual Stress Distributions in P92 Steel Joints Considering the Influence of Solid-State Phase Transformation

2016 ◽  
Author(s):  
Dean Deng ◽  
Hidekazu Murakawa
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Solid State ◽  
Computational Approach ◽  
Residual Stress Distribution ◽  
Welding Residual Stress ◽  
Stress Distributions ◽  
P92 Steel ◽  
Solid State Phase Transformation ◽  
Steel Joints

In this study, an advanced computational approach based on SYSWELD software was developed to simulate welding residual stress distributions in P92 steel joints with the consideration of solid-state phase transformation. Using the developed numerical method, we calculated the welding residual stress distribution in a single-pass weld joint, and clarified the influences of volume change, variation of yield strength and phase transformation induced plasticity on the formation of residual stress. Meanwhile, experiment was carried out to measure the welding residual stress distributions in the single-pass joint. The effectiveness of the developed computational approach was verified by the experimental results. In addition, the features of welding residual stress distribution in multi-pass P92 steel joint were discussed based on the results obtained by numerical simulation, and some new viewpoints on welding residual stress in multi-pass P92 steel joints were obtained.

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