Material Flow Behavior Research Articles

Fabrication of Papillary Composite Microstructured Aluminum Surfaces by Laser Shock Imprinting and Ablation

Laser shock ablation is incorporated into laser shock imprinting for the fabrication of papillary composite microstructures on aluminum surfaces. The primary papillary structures are fabricated using laser shock imprinting. Subsequently, secondary structures were fabricated on the surface of these primary structures using laser shock ablation, forming composite papillary microstructures. The influence of various laser shock ablation process parameters on the formation effect of these papillary composite microstructure surfaces was investigated. The results indicate that both laser shock energy and shock frequency affect the integrity of the secondary microstructure coverage on the material surface, the height of the composite microstructure, and the surface morphology. Through comparative optimization, the optimal process parameters were determined to be 675 mJ of energy and one shock ablation. Additionally, the differences in the flow behavior of metallic materials between the center and the periphery of the beam spot, caused by the shock wave, were analyzed. The wettability of the composite microstructure aluminum surface was also explored. The variation mechanism of wettability was explained by detecting changes in the contact angle on the aluminum surface at different time intervals and analyzing changes in surface chemical composition before and after aging. Specifically, after laser shock ablation, the aluminum surface contains a large number of polar groups, making it hydrophilic. During aging treatment, these polar groups continuously adsorb non-polar alkyl organic compounds, eventually leading to hydrophobicity, with a stabilized average surface contact angle of 143°. Fluorination treatment can further achieve superhydrophobicity, with a contact angle of 151° achieved shortly after processing the composite microstructure aluminum surface.

Material Flow and Microstructural Evolution in Friction Stir Welding of LAZ931 Duplex Mg-Li Alloys

The material flow behavior during friction stir welding (FSW) plays a critical role in the quality of final joints. In this study, the FSW of LAZ931 duplex Mg alloy was carried out at a rotation speed of 800 rpm and welding speeds of 50, 100, and 200 mm/min, respectively. A thin pure Mg strip inserted at the interface between the two Mg-Li alloy plates was used as a marker to study the flow behavior of the materials in the FSW process. Sound welds with no defects were obtained for all three welding speeds. The microstructural evaluations along the marker on the horizontal cross-section around the keyhole of the welds were characterized. As the welding speed increased, the marker came closer to the keyhole, indicating the decreased extent of the plastic deformation of the material. In the shoulder-affected zone (SAZ), the thickness of the marker reduced gradually in the accelerating stage and finally accumulated together in the decelerating stage. However, in the pin-affected zone (PAZ), the thickness of the marker reduced sharply in the accelerating stage and then became dispersed in the decelerating stage, and the degree of dispersion decreased as the weld speed increased. As a result, an elongated grain structure was formed in the SAZ, while two equiaxial grain structures were formed in the PAZ. The material on the advancing side was refined by the pin and deposited in the weld to form a fine equiaxial grain structure due to the high strain rate. In contrast, the material on the retreating side was pushed by the pin and thus directly deposited in the weld to form a coarse equiaxial grain structure. In addition, the area of the fine equiaxial grain structure was reduced obviously with the increase in welding speed.

Material Flow Behavior and Thermal Cycle during Friction Stir Welding of AA5083/AZ91 Dissimilar Metals

Material Flow Behavior and Thermal Cycle during Friction Stir Welding of AA5083/AZ91 Dissimilar Metals

Effect of heat input on microstructure and mechanical properties of AA6061 alloys fabricated by additive friction stir deposition

Heat input (HI) is the major factor that affects the surface quality, microstructure and mechanical properties of the deposition during the additive friction stir deposition (AFSD) process. Effect of HI on the microstructure and mechanical performance of the AFSDed AA6061 has been in-depth explored via adjusting the values of traverse speed (v) and layer thickness (t). Results indicate that deposition with a higher HI promotes the material flow behavior as well as the plastic deformation, which effectively enhances the grain refinement and structural uniformity, and avoids the formation of defects. Meanwhile, TEM results confirm that the enhanced HI leads to the formation of a higher volume fraction of the finer precipitations (Mg2Si and AlFeSi phases), which assists in suppressing abnormal grain growth phenomenon and improves the bonding strength of the deposition. As HI decreases, the transfer efficiency of materials clearly reduces because of the incompletely softened materials, causing less plastic deformation and poor interlayer bonding strength of the deposition. The deposition with the lowest HI displays the worst tensile properties with the lowest micro-hardness (107 HV0.5), YS (273 MPa) and UTS (303 MPa).

Architected Design and Fabrication of Soft Mechanical Metamaterials

This study proposes a systematic design approach to 3D print soft mechanical metamaterials by tuning material flow behavior and using optimal toolpaths and print parameters. Planar printing tool paths, utilized in layer‐by‐layer printing such as fused deposition modeling (FDM) and prevalently used in most slicing algorithms, severely limit the realization of complex topologies required in metamaterials. Utilizing parametric design principles, the proposed approach employs discrete and continuous 3D freeform tool paths for supported and unsupported direct ink writing (DIW) of elastomeric structures. The resulting textured, soft topologies significantly enhance the performance of various mechanisms in soft robotics and impact energy‐absorbing wearable devices. Various bioinspired structures such as cilia, webs, leaf‐like structures, and lattices are explored using extrusion‐based silicone 3D printing, achieving features with high aspect ratios (L/D ≤ 12) without support. These complex structures are challenging to 3D print using conventional planar toolpaths. To demonstrate the enhanced functionalities enabled by these new topologies, cilia arrays added to suction cups increased the pull‐off forces by 18%. Additionally, 3D‐printed elastomeric lattice slabs used as energy‐absorbing structures reduced the maximum impact peak forces by 85%. Further functionalities, including magnetic, thermochromic, and signal transmission properties, are also showcased using functional soft mechanical metamaterials.

Recent Advances in Additive Friction Stir Deposition: A Critical Review.

Additive friction stir deposition (AFSD) is a novel solid-state additive manufacturing method developed on the principle of stirring friction. Benefits from its solid-phase properties, compared with traditional additive manufacturing based on melting-solidification cycles, AFSD solves the problems of porosity, cracks, and residual stress caused by the melting-solidification process, and has a significant improvement in efficiency. In AFSD, the interaction between feedstocks and high-speed rotating print heads suffers severe plastic deformation at high temperatures below the melting point, ending up in fine, equiaxed recrystallized grains. The above characteristics make components by AFSD show similar mechanical behaviors to the forged ones. This article reviews the development of AFSD technology, elaborates on the basic principles, compares the macroscopic formability and material flow behavior of AFSD processes using different types of feedstocks, summarizes the microstructure and mechanical properties obtained from the AFSD of alloys with different compositions, and finally provides an outlook on the development trends, opportunities, and challenges to the researchers and industrial fields concerning AFSD.

3D modeling for effect of tool eccentricity on coupled thermal and material flow characteristics during friction stir welding

A novel three-dimensional numerical model is proposed to investigate the effect of tool eccentricity on the coupled thermal and material flow characteristics in friction stir welding (FSW) process. An asymmetrical boundary condition at the tool−workpiece interface, and the dynamic mesh technique are both employed for the consideration of the tool eccentricity during tool rotating. It is found that tool eccentricity induces the periodical variation of the heat densities both at the tool−workpiece interface and inside the shear layer, but the fluctuation amplitudes of the heat density variations are limited. However, it is demonstrated that tool eccentricity results in significant variation of the material flow behavior in one tool rotating period. Moreover, the material velocity variation at the retreating side is particularly important for the formation of the periodic characteristics in FSW. The modeling result is found to be in good agreement with the experimental one.

Microstructural Characterization of Friction Stir Welds of Aluminum 6082 Produced with Bobbin Tool.

This study utilized a bobbin tool to friction stir weld aluminum 6082 workpieces under two sets of process parameters: a tool rotation speed of 280 rev/min with a weld velocity of 280 mm/min (280/280) and a tool rotation speed of 450 rev/min with a weld velocity of 450 mm/min (450/450). The weld microstructures were characterized through optical microscopy utilizing polarized light and through transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with chemical analysis by energy dispersive spectroscopy and electron back scatter diffraction. The microstructural studies were supplemented by hardness measurements (Vickers) performed on the same sections as the metallographic examinations. The produced weldments were free from cracks and any discontinuities. Fine, equiaxed grains that were several microns in size characterized the stir zones (SZs), and the advancing (AS) and retreating (RS) sides revealed distinct microstructural features. On the AS, the transition from the thermo-mechanically affected zone to the SZ was well defined and sharp, but on the RS, the transition appeared as a continuous, gradual change in microstructure. The lower weld energy (280/280) produced lower hardness in the stir zone than the higher energy weld (450/450), ~95 HV1 versus ~115 HV1; however, the 280/280 welds showed higher tensile strengths than the 450/450 welds, ~238 MPa as opposed to ~172 MPa. These behaviors in mechanical performance correlated with the temperature histories produced by each set of weld parameters in relation to the precipitation behavior of the alloy. The fracture characteristics of the weldments were notably different with the 450/450 sample fracturing in a quasi-brittle manner with slight plastic deformation and the 280/280 sample fracturing ductilely. A numerical simulation supported the investigation by elucidating the temperature and material flow behavior during the joining process.

Billet Size Optimization for Hot Forging of AISI 1045 Medium Carbon Steel Using Zener-Hollomon and Cingara-McQueen Model

This study investigates the effects of initial billet size variations on material flow behavior in hot forging processes, aiming to optimize the forging process using validated predictive models. Material and high-temperature compressive tests inform mathematical models, while simulations are conducted via the finite element method (FEM). Results align with the Zener-Hollomon and Cingara-McQueen approaches. The Arrhenius model predicts AISI 1045 steel flow stress with an R2 of 0.968 and an average absolute relative error (AARE) of 7.079%. The Cingara-McQueen equation achieves an R2 of 0.997 and an AARE of 2.960%. Reducing billets size from 260 mm to 230 mm decreases the material usage by up to 11.5%, while maintaining workpiece integrity. Experimental and simulated loads exhibit an AARE of about 2.69%, thereby indicating potential cost and efficiency improvements in hot forging processes.

An energetic approach to the statistical analysis and optimization of friction welding processes applied to an aluminum-steel-joint

The present publication deals with an energy-oriented approach to the statistical analysis of rotational friction welding processes. To illustrate the methodological approach, it is applied to investigate the effects of energy flow on material flow behavior and joint quality during friction welding of an AA6060 alloy with a low-alloy 16MnCr5 filler steel. The influences of the setting parameters on the energetic states are first analyzed by means of an initial screening. The evaluation using process simulation and statistical methods enables the generation of regressive response surfaces for the friction power, the friction time and the resulting induced friction energy. Based on these findings, a second experimental field is formed and evaluated, which considers the interaction between the energy input of the frictioning stage and the workpiece forging. This new approach results in the functional separation of the frictioning and forging stage, which eliminates the usual statistical interaction effects and thus facilitates analysis and optimization. The qualitative result variable required for the purpose of interpreting the results is the ultimate tensile strength of the friction-welded joint. Additionally determined hardness curves provide information about the properties of the thermally influenced zone and strength-relevant process sequences. The result is that, in addition to the amount of energy induced, the frictional power with which the former is induced also has a considerable influence on the joint strength, as it influences the material flow and the properties of the joining zone.

Finite element modeling of the glass sealing process for solid oxide cell stacks

The sealing process for solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) stacks is a vital step in the assembly and manufacturing of these systems. The cell seal and stack seal serve to prevent leakage and the mixing of air with hydrogen and steam during operation. Good seals are critical for reporting accurate cell and stack performance and durability, as leaks can mask degradations and manifest as performance improvement. Predictive modeling of seal materials during sealing processes for SOFC and SOEC stacks has been largely unexplored and could provide design and manufacturing insights for these systems. In this work, finite element modeling was conducted to simulate the assembly and stack sealing of planar cells to capture the densification, viscous flow, and crystallization behavior of the G18 glass ceramic seal material during full scale stack fabrication. The Skorohod-Olevsky viscous sintering material model was implemented in the ANSYS finite element program and modified to account for crystallization effects to simulate the response of the G18 seal material. The effects of initial cell/stack curvature were captured via preliminary stack manufacturing simulations, and its influence on stack sealing quality was studied. Effects of compressive loading sequence and configuration were investigated.

Strain path dependent dynamic recrystallization and its resulted material flow and microstructure evolution of a titanium alloy

Changing strain path is an effective method to optimize the hot working process and improve microstructure and mechanical performance of titanium alloys. In this work, dynamic recrystallization (DRX) and its resulted material flow and microstructural behaviors in monotonic torsion (MT) and forward-reverse torsion (FRT) were comparatively explored by experimental and crystal plastic finite element simulation methods. The results indicate that both MT and FRT can induce discontinuous DRX (DDRX) and continuous DRX (CDRX). However, compared to MT where CDRX always prevails, FRT makes DDRX more important since it inhibits CDRX by recovering the lattice rotation during the reversal stage. Moreover, in FRT, the driving force and the grain boundary content for DDRX nucleation and bulging are relatively low at a small total strain. And the recovery of lattice rotation in FRT can also suppress CDRX. Therefore, DRX kinetics is obviously delayed at a smaller strain. As strain increases, both the stored energy for DDRX and the long-range misorientation gradient for CDRX are gradually greater, thus improve DRX kinetics. With these effects by DRX, although FRT exhibits a lower grain refinement degree at a smaller total strain compared to MT, it can make grain refinement degree rapidly rise and even close to that in MT at a greater strain. Also, FRT can obviously weaken the deformation texture by inducing extensive DDRX grains and recovering the lattice rotation of retained grains. In addition, the texture formed in forward stage and DRX delaying can result in a decrease in yield strength and softening rate in reversal stage, respectively, i.e., exhibiting remarkable Bauschinger effect, especially at a higher forward strain. These results can provide a basic guidance for designing the hot working process of titanium alloys to obtaining more refined microstructure and excellent properties of the components.

Influence of material in sheet-bulk metal forming from coil

AbstractSheet-bulk metal forming (SBMF) represents an innovative approach for the efficient manufacturing of functional integrated parts from sheet metal by applying bulk forming processes to sheet metal. It combines the advantages of part weight optimization and process chain shortening. In view of the increasing demand for functionally integrated components, the forming from coil offers an economical possibility to produce high output rates. Nevertheless, an underfilling of functional elements as well as an asymmetric part forming are current challenges. In order to apply SBMF from coil in industrial contexts, it is necessary to understand the causes of these process limits and to develop measures for improving the forming of functional elements and thereby push existing forming limits. In this paper, both a lateral and a backward extrusion process from coil for the forming of internal and external geared SBMF parts are investigated to develop a fundamental process understanding. In a combined numerical-experimental approach, the influence of the flow behavior of different materials as well as the impact of the main material flow direction of the process on the dimensional part accuracy is analyzed. This enables the evaluation of fundamental material-related dependencies and influences regarding the geometrical part accuracy, the mechanical component properties and the tool load for forming of the conventional deep-drawing steel DC04 (t0 = 2 mm), a high-strength steel material (HC260LA) and an aluminum alloy (AA6082 T6). Based on these findings, measures for material flow control are identified and investigated to counteract the challenges of SBMF from coil. These findings permit the identification of potential transferability of the identified cause-effect mechanisms to different processes, component geometries and materials. Thereby, in particular, an increase in coil width as well as lower a strain hardening behavior of the material offers the possibility to improve the geometrical accuracy of the components.

A Discrete Element Method Calibration Approach for Large Ore-flow Applications

The major constraint for large discrete element method (DEM) simulations is the high demand for computation power. To keep the model in a feasible range of simulation time and to conduct the numerical calculations efficiently, the implemented material can be simplified and upscaled. After this, a calibration of the material is inevitable and sets the link between the simulation model and reality. Therefore, an alternative calibration approach is established in this contribution to mimic the flow behaviour of the original material with multi-spherical DEM particles. The calibration approach utilises flow zone dimensions, which were observed in block-caving operations. Additionally, a passive draw-point is used to calibrate the angle of repose. Applying the calibration approach for Kiruna iron ore showed that, with the help of the calibration approach, the material in the simulation could successfully reproduce the targeted flow zone and angle of repose.

Assessing the Performance of a Dual-Speed Tool When Friction Stir Welding Cast Mg AZ91 with Wrought Al 6082.

A novel dual-speed tool for which the shoulder and pin rotation speeds are separately established was utilized to friction stir weld cast magnesium AZ91 with wrought aluminum 6082-T6. To assess the performance and efficacy of the dual-speed tool, baseline dissimilar welds were also fabricated using a conventional FSW tool. Optical microscopy characterized the weld microstructures, and a numerical simulation enhanced the understanding of the temperature and material flow behaviors. For both tool types, regions of the welds contained significant amounts of the AZ91 primary eutectic phase, Al12Mg17, indicating that weld zone temperatures exceeded the solidus temperature of α-Mg (470 °C). Liquation, therefore, occurred during processing with subsequent eutectic formation upon cooling below the primary eutectic temperature (437 °C). The brittle character of the eutectic phase promoted cracking in the fusion zone, and the "process window" for quality welds was narrow. For the conventional tool, offsetting to the aluminum side (advancing side) mitigated eutectic formation and improved weld quality. For the dual-speed tool, experimental trials demonstrated that separate rotation speeds for the shoulder and pin could mitigate eutectic formation and produce quality welds without an offset at relatively higher weld speeds than the conventional tool. Exploration of various weld parameters coupled with the simulation identified the bounds of a process window based on the percentage of weld cross-section exceeding the eutectic temperature and on the material flow rate at the tool trailing edge. For the dual-speed tool, a minimum flow rate of 26.0 cm3/s and a maximum percentage of the weld cross-section above the eutectic temperature of 35% produced a defect-free weld.

Dynamic modelling and efficiency prediction for forging operations under a screw press

Accurate predictions concerning a forging process can be obtained by numerical simulation, but only with a thorough knowledge of the main process variables. The material flow behavior and the interface effects are already well studied in the literature, but not the machine behavior, although it is required to estimate blow efficiency and deduce the energy actually transmitted to the workpiece. In this paper, an experimental methodology was applied to determine a spring-mass-damping model and its associated parameters for a screw press. The model and its parameters were identified with press strikes performed without billet. For validation, simulations were performed to predict blows on copper billets. The model’s predictions were in good agreement with the experimental measurements for ten consecutive blows on a copper billet. The decrease of process efficiency and the evolution from inelastic blows to elastic blows were correctly depicted by the model.

Food Rheology: An Introduction and Fundamentals Concepts

Food rheology is the study of the flow and deformation of food materials. It involves understanding the physical and mechanical properties of food, such as how it behaves when subjected to external forces or changes in temperature. Understanding food rheology is essential in various food processing and manufacturing industries as it helps in product development, quality control, and optimization of processing parameters. Some fundamental concepts in food rheology include as follows. Viscosity refers to a material’s resistance to flow. In food rheology, it is a measure of how easily a food material flows under an applied force. Food materials can exhibit different types of viscosity, such as Newtonian, pseudoplastic, dilatant, and viscoelastic behavior. Shear stress is the force per unit area applied to a food material, while the shear rate is the rate at which the food material deforms. In food rheology, these two variables are used to describe the flow behavior of food materials. Different food materials have different flow behaviors. Some foods, like water, exhibit Newtonian flow behavior, where the viscosity remains constant regardless of the applied shear rate. Other foods, like ketchup or mayonnaise, exhibit non-Newtonian flow behavior, where the viscosity changes with the shear rate. Elasticity refers to a material’s ability to regain its original shape after deformation. In food rheology, elasticity is important in determining the texture and shelf life of food products. Viscoelasticity refers to the combined properties of both viscosity and elasticity, where a material exhibits both liquid-like (viscous) and solid-like (elastic) behavior. Yield stress is the minimum amount of shear stress required to initiate flow in a material. Many food materials, such as gels or semisolid foods, exhibit yield stress where they behave like a solid until a certain stress threshold is reached. By understanding these fundamental concepts, food scientists and engineers can manipulate and control the rheological properties of food materials to achieve the desired texture, mouthfeel, and sensory attributes, as well as optimize processing conditions to improve the overall quality of food products.

Effect of material flow behavior on the formation of interfacial reaction layers and fatigue performance of dissimilar friction stir welded S45C and AA6061-T6

Effect of material flow behavior on the formation of interfacial reaction layers and fatigue performance of dissimilar friction stir welded S45C and AA6061-T6

Simulation of Material Flow Behavior during Friction Stir Welding of 7075 Aluminum Alloy

Simulation of Material Flow Behavior during Friction Stir Welding of 7075 Aluminum Alloy

Optimizing profiled ring preforms for enhanced deformation uniformity using the isothermal field method

One of the main challenges faced by the profiled ring rolling (PRR) process is to ensure the deformation uniformity of the ring, which is closely related to the design of the ring preform. The paper explores the application of the isothermal field method (IFM) in designing preforms for PRR processes, targeting the aerospace sector's high-end equipment manufacturing. Through the integration of advanced computational models and practical design principles, a comprehensive approach involving IFM, finite element simulation, support vector machine modeling, and genetic algorithm optimization is employed to determine the geometric dimensions of rational preforms. The material flow behavior during the PRR process is analyzed, and the effects of different isotherms combinations on strain, stress and temperature distribution are discussed. The findings demonstrate that adjusting the preform's shape during the section forming stage can optimize the uniformity of strain, stress, and temperature within the forging. The stable ring rolling process revealed no macroscopic or microscopic defects, validating the design method of ring preform based on IFM is reasonable. The research contributes to advancing near-net shape forming technologies, offering a novel approach to preform design that marries theoretical analysis with practical manufacturability considerations.