Numerical Modeling of Transport Phenomena and Dendritic Growth in Laser Conduction Welding of 304 Stainless Steel

2011 ◽  
Author(s):  
Wenda Tan ◽  
Neil S. Bailey ◽  
Yung C. Shin
Keyword(s):  
Stainless Steel ◽  
Molten Pool ◽  
Dendritic Growth ◽  
Quantitative Agreement ◽  
304 Stainless Steel ◽  
Experimental Result ◽  
Scale Model ◽  
Transient Model ◽  
Micro Scale ◽  
Macro Scale

A multi-scale model is developed to investigate the heat/mass transport and dendrite growth in laser spot conduction welding. A macro-scale transient model of heat transport and fluid flow is built to study the evolution of temperature and velocity field of the molten pool. The molten pool geometry and other solidification parameters are calculated, and the predicted pool geometry matches well with experimental result. On the micro-scale level, the dendritic growth of 304 stainless steel is simulated by a novel model that has coupled the Cellular Automata (CA) and Phase Field (PF) methods. The epitaxial growth is accurately identified by defining both the grain density and dendrite arm density at the fusion line. By applying the macro-scale thermal history onto the micro-scale calculation domain, the microstructure evolution of the entire molten pool is simulated. The predicted microstructure achieves a good quantitative agreement with the experimental results.

Numerical Modeling of Transport Phenomena and Dendritic Growth in Laser Spot Conduction Welding of 304 Stainless Steel

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Wenda Tan ◽  
Neil S. Bailey ◽  
Yung C. Shin
Keyword(s):  
Stainless Steel ◽  
Molten Pool ◽  
Dendritic Growth ◽  
Multiscale Model ◽  
Quantitative Agreement ◽  
Laser Spot ◽  
304 Stainless Steel ◽  
Experimental Result ◽  
Transient Model ◽  
Novel Model

A multiscale model is developed to investigate the heat/mass transport and dendrite growth in laser spot conduction welding. A macroscale transient model of heat transport and fluid flow is built to study the evolution of temperature and velocity field of the molten pool. The molten pool shape is calculated and matches well with the experimental result. On the microscale level, the dendritic growth of 304 stainless steel is simulated by a novel model that has coupled the cellular automata (CA) and phase field (PF) methods. The epitaxial growth is accurately identified by defining both the grain density and dendrite arm density at the fusion line. By applying the macroscale thermal history onto the microscale calculation domain, the microstructure evolution of the entire molten pool is simulated. The predicted microstructure achieves a good quantitative agreement with the experimental results.

Numerical Modeling of Grain Growth in Laser Engineered Net Shaping (LENS) of AISI 316 Stainless Steel

2017 ◽  
Author(s):  
Wenda Tan ◽  
Xuxiao Li
Keyword(s):  
Stainless Steel ◽  
Grain Growth ◽  
Molten Pool ◽  
Grain Structure ◽  
Scale Model ◽  
Modeling Framework ◽  
Laser Engineered Net Shaping ◽  
Macro Scale ◽  
Aisi 316 ◽  
Net Shaping

A multi-scale modeling framework is developed in this work to simulate the transport phenomena and grain growth in Laser Engineered Net Shaping (LENS) process of austenitic stainless steel AISI 316. A three-dimensional (3D) model is included to simulate the transient molten pool geometry and heat/mass transfer on a macro-scale; and a 3D meso-scale model based on the Cellular Automata method is included to predict the grain growth during molten pool solidification. The predicted grain structure is found to be consistent with the experimental results and reveals that the grain structure is highly dependent on the molten pool geometry.

scholarly journals Microstructure and mechanical performance of dissimilar metal joints of aluminium alloy and stainless steel by cutting-assisted welding-brazing

2021 ◽  
Author(s):  
Huibin Xu ◽  
Wei Cong ◽  
Donghua Yang ◽  
Yanlong Ma ◽  
Wanliang Zhong ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Aluminium Alloy ◽  
Cutting Tool ◽  
Mechanical Performance ◽  
Interfacial Structure ◽  
304 Stainless Steel ◽  
Small Scale ◽  
Joint Interface ◽  
Micro Scale ◽  
Macro Scale

Abstract The 5052 aluminium alloy and 304 stainless steel were successfully joined by cutting-assisted welding-brazing (CAWB) method without using flux. Dual-scale interfacial structures were achieved by manipulating the cutting tool profile. Results indicated that the macro-scale interfacial structure was produced at the joint interface when the taper step-shape cutting tool was adopted. As the cutting tool step was increased to 6-step, the micro-scale interface took on serrated morphology and a layer of continuous and wavy intermetallic compound (IMC) with an average thickness of 3.3 μm was formed at the interface. The τ 4 IMC particles and the FeAl 6 phases on a small scale were dispersed homogeneously in the welded seam. The maximum tensile strength of the joints reached 152.3 MPa upon tensile loading, 75% that of the 5052 aluminium base metal. The strong and reliable Al/steel dissimilar joints were attributed to the particle reinforced weld metal and the macro- and micro-scale dual self-locking structure at the interface.

Scaling up microbial dynamics for soil carbon cycling models

2020 ◽  
Author(s):  
Stefano Manzoni ◽  
Arjun Chakrawal ◽  
Naoise Nunan
Keyword(s):  
Soil Heterogeneity ◽  
Scale Model ◽  
Soil Drying ◽  
Integration Step ◽  
Soil Core ◽  
Microbial Dynamics ◽  
Element Cycling ◽  
Micro Scale ◽  
Macro Scale ◽  
Soil Heterogeneities

<p>Soils are heterogeneous at all scales and so are the biogeochemical reactions driving the cycling of carbon (C) and nutrients in soils. While the microbial processes involved in these reactions occur at the pore scale, what we observe at the soil core or pedon scale depends on how micro-scale processes are integrated in space (and time). This integration step requires accounting for the inherent patchiness of soils, but models used to describe element cycling in soils typically assume that conditions are well-mixed and that kinetics laws developed for laboratory conditions hold. Similarly, the response functions used in models to capture the effects of environmental conditions on C and nutrient fluxes neglect the contribution of spatial heterogeneities, which might alter their shape. There is therefore a need to re-evaluate model structures to test whether they can account for micro-scale heterogeneities. Alternatively, one can ask why some models are clearly successful in capturing observations despite neglecting soil heterogeneities. In this contribution, we present examples of how soil heterogeneities – in particular the spatial placement of soil microorganisms and their substrate – may affect decomposition kinetics and microbial responses to soil drying. We show that the kinetics laws used in current models are different from the kinetics obtained by integrating microbial dynamics at the micro-scale, and that respiration responses to soil drying may vary depending on soil heterogeneity. These results thus highlight structural uncertainties in current models that we propose can be assessed using existing ‘scale-aware’ methods to derive macro-scale model formulations. Model advances will need to be supported by empirical evidence bridging the gap between pore and core (or larger) scales, but can also provide new theory-based hypotheses for novel experiments.</p>

scholarly journals High-Speed Welding of Stainless Steel with Additional Compensatory Gas Jet Blow Molten Pool

2018 ◽  
Vol 8 (11) ◽  
pp. 2170 ◽  
Author(s):  
Changwen Dong ◽  
Jiaxiang Xue ◽  
Zhanhui Zhang ◽  
Li Jin ◽  
Yu Hu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Cross Sections ◽  
Molten Pool ◽  
High Speed ◽  
Fracture Load ◽  
304 Stainless Steel ◽  
Gas Jet ◽  
Butt Welding ◽  
Steel Sheets ◽  
Welding Processes

To avoid humping bead defects in high-speed welding, this paper proposes the method of an additional and compensatory gas jet blow molten pool. A pulsed metal inert gas high-speed welding test platform was constructed for compensatory gas jet blow molten pool. A total of 304 stainless steel sheets were used as the welding workpieces under equal heat inputs. Two high-speed butt welding processes were conducted and compared, in which the workpieces were welded with and without compensatory gas jets at 154 cm/min and 167 cm/min, respectively. After high-speed welding with compensatory gas jet blow, the weld appearance was straight, uniform, and high-quality, with no humping bead or undercut defects. The macroscopic morphologies and microstructures of cross-sections of the weld at the toe, near the surface, the middle, and the bottom portion all showed the stirring effect of the gas jet on the molten pool and improved grain refinement degrees. Hardness was enhanced in the weld center and the heat-affected zone. At welding speeds of 154 cm/min and 167 cm/min, the fracture load capacities of the welds were increased by 24.9 and 10.4%, respectively.

Investigation on Weld Pool Dynamics in Laser Welding of AISI 304 Stainless Steel With an Interface Gap Via a Three-Dimensional Dynamic Model and Experiments

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Kyung-Min Hong ◽  
Yung C. Shin
Keyword(s):  
Stainless Steel ◽  
Molten Pool ◽  
Three Dimensional ◽  
Lap Joints ◽  
304 Stainless Steel ◽  
Weld Strength ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
Lap Welding ◽  
Welding Processes

This paper reports on numerical and experimental investigations involving examination of the effects of an interfacial gap in the range of 0–0.3 mm on keyhole and molten pool dynamics. A numerical model was developed to investigate the three-dimensional transient dynamics of the keyhole in lap welding processes with an interface gap. The model was able to reliably predict the weld profile. In addition, the modeling results provided detailed information regarding the interaction between the molten pool and the solid/liquid boundary that led to the extended weld width. Experimentally, AISI 304 stainless steel was joined in a lap welding configuration using an IPG YLR-1000 fiber laser. The tensile shear and T-peel testing of the lap joints showed that adding an adequate amount of interface gap improves weld strength.

scholarly journals Creep Life Prediction Based on Stochastic Model of Microstructurally Short Crack Growth

1989 ◽  
Vol 111 (2) ◽  
pp. 169-175 ◽  
Author(s):  
Takayuki Kitamura ◽  
Ryuichi Ohtani
Keyword(s):  
Stainless Steel ◽  
Crack Length ◽  
Crack Growth ◽  
Short Crack ◽  
304 Stainless Steel ◽  
Experimental Result ◽  
Multiple Cracks ◽  
Single Crack ◽  
Creep Life ◽  
Creep Fracture

A nondimensional model of microstructurally short crack growth in creep is developed based on a detailed observation of the creep fracture process of 304 stainless steel. In order to deal with the scatter of small crack growth rate data caused by microstructural inhomogeneity, a random variable technique is used in the model. A cumulative probability of the crack length at an arbitary time, G(a,t), and that of the time when a crack reaches an arbitary length, F(t,a), are obtained numerically by means of a Monte Carlo method. G(a,t) and F(t,a) are the probabilities for a single crack. However, multiple cracks generally initiate on the surface of a smooth specimen from the early stage of creep life to the final stage. Taking into account the multiple crack initiations, the actual crack length distribution observed on the surface of a specimen is predicted by the combination of probabilities for a single crack. The prediction shows a fairly good agreement with the experimental result for creep of 304 stainless steel at 923 K. The probability of creep life is obtained from an assumption that creep fracture takes place when the longest crack reaches a critical length. The observed and predicted scatter of the life is fairly small for the specimens tested.

scholarly journals Analytical Micromechanics Models for Elastoplastic Behavior of Long Fibrous Composites: A Critical Review and Comparative Study

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1919 ◽  
Author(s):  
Yanchao Wang ◽  
ZhengMing Huang
Keyword(s):  
Comparative Study ◽  
Critical Review ◽  
Scale Model ◽  
Fibrous Composites ◽  
Elastoplastic Behavior ◽  
Micro Scale ◽  
Micromechanics Models ◽  
Macro Scale ◽  
Stress Concentration Factors ◽  
Well Correlation

Elasto-plastic models for composites can be classified into three categories in terms of a length scale, i.e., macro scale, meso scale, and micro scale (micromechanics) models. In general, a so-called multi-scale model is a combination of those at various length scales with a micromechanics one as the foundation. In this paper, a critical review is made for the elastoplastic models at the micro scale, and a comparative study is carried out on most popular analytical micromechanics models for the elastoplastic behavior of long fibrous composites subjected to a static load, meaning that creep and dynamic response are not concerned. Each model has been developed essentially following three steps, i.e., an elastic homogenization, a rule to define the yielding of a constituent phase, and a linearization for the elastoplastic response. The comparison is made for all of the three aspects. Effects of other issues, such as the stress field fluctuation induced by a high contrast heterogeneity, the stress concentration factors in the matrix, and the different approaches to a plastic Eshelby tensor, are addressed as well. Correlation of the predictions by different models with available experimental data is shown.

Predicting Multi-Scale Dimensional Accuracy of Engine Cylinder by Honing

2017 ◽  
Author(s):  
Zaoyang Zhou ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Lifeng Xi
Keyword(s):  
Surface Texture ◽  
Dimensional Accuracy ◽  
Scale Model ◽  
Cylinder Wall ◽  
Initial Shape ◽  
Abrasive Resistance ◽  
Micro Scale ◽  
Multi Scale ◽  
Macro Scale ◽  
Cylinder Bore

The deviations of cylinder bore dimensional accuracy have tremendous influence on engine performances including friction power loss, vibration, leak tightness between piston ring and cylinder wall, and abrasive resistance. Many researches were devoted to capturing cylinder dimensional accuracies by honing using analytical, experimental and simulation methods. These researches investigated the topography and roughness of the honed surface, the relationship between the process parameters and the dimensional accuracies. However, most researches focused on macro-scale dimensional accuracy and micro-scale surface texture respectively. To overcome the limitation, a multi-scale model for cylinder bore honing is proposed to predict the dimensional accuracy and surface texture of cylinder bore at macro-scale and micro-scale simultaneously. The model integrates the microscale factors of the honing stone abrasives distribution characteristics, abrasive wear process, previous cylinder surface topography, and macro-scale factors of cylinder geometry and honing head motion trajectory. A Force matching method is adopted to determine the feed depth of cylinder honing process. Thus the model can predict the roundness, cylindricity, roughness and Abbott-Firestone curve of the honed cylinder bore at multi-scale levels. Simulation results show that material removal distribution is closely related to cylinder bore initial shape deviations. The deviations with long wavelengths cannot be eliminated by the sequential honing.

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