High-speed Process Research Articles

Simulation of the influence of welding parameters on weld pool behavior during a TIG-MIG hybrid welding process

TIG-MIG hybrid welding produces better weld formation than traditional MIG welding at higher welding speeds. The adaptive heat source and arc pressure models of inclined TIG-MIG arcs on curved surface were improved based on their distribution on flat surface. A 3D transient model of heat and mass transfer in a weld pool was established to analyze the influences of various welding parameters on a high-speed TIG-MIG hybrid welding process. The influence of the TIG current, distance between electrodes, and welding speed on this hybrid welding process were simulated to study the quantitative relationships between process parameters, molten pool behavior, and weld beam formation. The heat flux field, temperature field, and fluid flow on the upper surface and longitudinal sections of the weld pool were simulated and analyzed under various welding conditions. Experiments were performed; the simulation results agreed well with the experiments.

Analysis of Necking Deformation Behavior in High-Speed In-line Drawing Process of PET by On-line Diameter and Velocity Measurements

Abstract To clarify the characteristic behavior of filament deformation in high-speed in-line drawing process of poly(ethylene terephthalate) (PET), on-line measurements of filament velocity and diameter were performed. In the process, velocity of the first godet roller was fixed at 2 km/min and the draw ratio was varied from 1.75 to 2.25 by changing the velocity of the second godet roller from 3.5 to 4.5 km/min. For comparison, on-line measurements were also performed for the high-speed melt spinning process at take-up velocities of 2 to 5 km/min. Diameter and velocity profiles of PET filament in the high-speed in-line drawing process indicated that the filament started to deform immediately after passing through the first godet roller (GR-1), and finished its deformation at 40 ~ 60 cm from the GR-1. The region of deformation became narrower and shifted toward the GR-1 with an increase in the draw ratio. Detailed analysis of necking deformation through simultaneous diameter measurements at two positions of close distance revealed that the position of necking deformation fluctuates along the drawing-line and its shape varies significantly depending on the direction of its movement. When the position of necking deformation was shifting toward the upstream, its shape was steeper than the one shifting toward the downstream. Results of the simultaneous on-line measurements of diameter and velocity supported this conclusion qualitatively. The analyzed maximum strain rate at the draw ratio of 2.0 reached a high value of 510 s– 1.

Direct sound printing

Photo- and thermo-activated reactions are dominant in Additive Manufacturing (AM) processes for polymerization or melting/deposition of polymers. However, ultrasound activated sonochemical reactions present a unique way to generate hotspots in cavitation bubbles with extraordinary high temperature and pressure along with high heating and cooling rates which are out of reach for the current AM technologies. Here, we demonstrate 3D printing of structures using acoustic cavitation produced directly by focused ultrasound which creates sonochemical reactions in highly localized cavitation regions. Complex geometries with zero to varying porosities and 280 μm feature size are printed by our method, Direct Sound Printing (DSP), in a heat curing thermoset, Poly(dimethylsiloxane) that cannot be printed directly so far by any method. Sonochemiluminescnce, high speed imaging and process characterization experiments of DSP and potential applications such as remote distance printing are presented. Our method establishes an alternative route in AM using ultrasound as the energy source.

Rock dynamic fracture of a novel semi-circular-disk specimen

The relationship between velocity, acceleration, and dynamic fracture toughness during rapid crack propagation is difficult to effectively capture. In this study, a novel semi-circular holed disc bend is proposed to achieve a long fracture path. Hopkinson pressure rods with crack growth and strain gauges are used to impact the semi-circular holed disc bend specimens and to monitor the cracking process of a mode-I fracture. The experiments show that the crack growth speed increases to a critical value after crack initiation and then oscillates as a result of the reflected stress wave. The dynamic propagation fracture toughness ( K IC d ) increases with increasing crack velocity for steady crack propagation; however, this does not apply for unsteady propagation. An experimental–numerical–analytical method is developed to determine the dynamic stress intensity factor , which initially increases with time, then decreases, and ultimately increases again. The acceleration ( v ˙ ) can be used to investigate the unsteady crack propagation process. K IC d values for v ˙ < 0 are greater than those for v ˙ > 0. An energy release rate formula related to v ˙ and the crack propagation velocity ( v ) is proposed and verified by the experiments. A thorough understanding of v , v ˙ , and K IC d is important to analyze high-speed fault rupture processes.

High-Speed Erichsen Testing of Grain-Refined 301LN Austenitic Stainless Steel Processed by Double-Reversion Annealing

Austenitic Cr–Ni stainless-type 301LN steel was subjected to a double-reversion annealing (DRA) treatment to develop bulk grain-refined microstructures. The tensile properties and formability of the DRA structures were determined by high-speed tensile and Erichsen cupping tests at a strain rate of 1.5 s−1 (50 mm s−1) and compared with those of coarse-grained steel. Detailed microstructural features of the DRA structures were characterized using the electron backscatter diffraction technique and X-ray diffraction analysis. The DRA structures achieved by annealing for 1 second at 800 °C and 900 °C exhibited a superior combination of yield (~ 950 and 770 MPa, respectively) and tensile (~ 1050 and 950 MPa, respectively) strengths and ductility (~ 35 and 40 pct, respectively, as well as reasonable Erichsen index values under high-speed biaxial strain. Due to adiabatic heating, the DRA structures had higher austenite stability during high-speed stretch forming, i.e., were less prone to strain-induced martensitic transformation. The finite-element method (FEM) was used to conduct coupled field thermomechanical analyses of the high-speed deformation processes for the coarse-grained and DRA structures. Comparison of the FEM analyses with the experimental results revealed a considerable influence (~ 20 pct) of martensitic transformation on the adiabatic temperature rise. The balance of the yield strength and Erichsen index value of the developed nanograined microstructure is comparable to that of coarse-grained commercial steel.

Humping Formation and Suppression in High-Speed Laser Welding.

Increasing welding speed can promote the productivity of laser welding. However, humping defects often occur, which limits the application of this strategy. The existing explanations for the humping formation remain vague, and mitigation and suppression methods are limited. In this research, high-speed imaging experiments and numerical simulation of the high-speed laser welding process are performed. Through careful examination, the humping phenomenon is explained. At high welding speed, the high-speed melt flow caused by recoil pressure is hindered by the solidified region in the melt pool, leading to the occurrence of a swelling. The swelling then grows, forming a valley in front of the swelling under the effect of surface tension. The solidification of the valley results in the occurrence of a second swelling. This process repeats and humping defect forms. Marangoni force and viscous force also have influence on this process. In addition, it is found that adding a Tungsten Inert Gas arc behind the laser beam can effectively suppress the humping.

How does high-speed rail construction affect air pollutant emissions? Evidence from the Yangtze River Delta Urban Agglomeration in China

Taking the construction of high-speed rail as a “quasi-natural experiment”, the panel data of 26 cities in the Yangtze River Delta from 2004 to 2018 were selected as samples, and a difference-in-differences model was constructed to study the impact of high-speed rail construction on air pollutant emissions. Furthermore, the meditating effect model and difference-in-differences model were built to explore the paths of high-speed railway construction affecting air pollutant emissions. According to the study, the construction of high-speed rail reduces industrial sulfur dioxide emissions and increases the emission of industrial smoke and dust, which are more obvious in areas with good economic conditions. The role of high-speed rail in reducing emissions is realized through the structure effect, technological effect and substitution effect. However, the construction/renovation process of high-speed rail lines or stations does increase the industrial smoke and dust emissions. In this study, the bidirectional effects of high-speed rail construction on different air pollutant emissions were identified, including the high-speed rail construction process into the research. Multiple paths of action were proposed, bridging the gap of existing studies. The study reveals that controlling the air pollution emissions throughout the full life cycle of the high-speed rail, from the construction process to its operation, was essential.

Effect of Radial Stress on the Nanoparticle-Based Electrolyte Layer in a Center-Wound Roll with Roll-to-Roll Systems.

Recently, slot-die coating based on the roll-to-roll process has been actively used to fabricate nanoparticle-based electrolyte layers because it is advantageous for high-speed processes and mass production of uniformly thick electrolyte layers. In this process, the fabricated electrolyte layer is stored as a wound roll throughout the rewinding process. We analyzed the defects and geometric changes in an electrolyte layer, i.e., gadolinium-doped cerium oxide (GDC), due to the radial stress in the wound roll. We found that the thickness of the coated layer could be decreased by increasing the radial stress, i.e., cracks can be generated in the coated layer if excessively high radial stress is applied to the wound-coated layer. More thickness changes and crack defects were generated with time due to the residual stress in the wound roll. Finally, we analyzed the effects of taper tension profiles on the defects of the coated layer in the wound roll and determined the taper tension profile to minimize defects.

Dynamic tensile mechanical behavior of polyurethane films incorporated with functionalized graphene oxide

Since high-speed collisions often give rise to catastrophic damage, investigating the enhancement and dynamic behavior of composites is essential. Herein, graphene oxide (GO) and its surface-modified derivative were separately incorporated into the polyurethane matrix and their dynamic mechanical properties were examined and compared. A drop-weight dynamic tension device was used to characterize the mechanical properties of composites. The collected results show significant improvement in failure strength while incorporating GO as the nanofiller. And, the slightly reduced graphene oxide (SRGO) grafted with polyethyleneimine (SRGO-PEI) is beneficial in improving the plastic stress. The high-speed deformation process reveals severe strain localization before the break. The morphology of fracture surfaces indicates the SRGO-PEI plays a vital role in hindering crack propagation. Then the constitutive equation was derived to describe the stress-strain curves of modified polyurethane films. This work involves the synergistic effect between surface modification of nanofillers and the dynamic behavior of polymer-based composites, which could be regarded as a guideline for designing the composites under high-velocity impact environments.

Investigation on deformation of DP600 steel sheets in electric-pulse triggered energetic materials forming

Electric-pulse triggered energetic materials forming (ETEF) is a high-speed manufacturing process, which utilizes the chemical energy released by energetic materials (EMs) triggered by underwater wire discharge to plastically shape metals. ETEF is not fully understood, particularly in research on the discharge characteristics of energetic materials triggered by metal wires and the deformation process of metal sheets. The above two problems were investigated in this paper using experimentation and numerical simulation. For the pulse discharge characteristics, the peak values of voltage and current were reduced during the triggering process of energetic materials, and the triggering energy consumption of energetic materials was quantified to be about 200 J. The matching parameters of different capacitor-voltage devices may be insensitive to triggering the energy release of energetic materials. The maximum major strain and thinning rate of the bulged specimen under ETEF conditions were significantly reduced when compared to the quasi-static specimen with the same bulging height, and the specimen’s deformation uniformity and strain distribution were improved. The simulation results showed that the addition of energetic materials significantly improved the plastic strain energy of the blank. The deformation of the blank in ETEF can be divided into two stages: the initial chemical energy action stage and the inertia action stage. The bulging height of sheet metal increased by nearly 301% in inertia action stage, accounting for 80% of the total deformation time, and the effective plastic strain distribution was more uniform.

Tool wear monitoring of high-speed broaching process with carbide tools to reduce production errors

Real-time monitoring in CNC machine tools is focused on the early detection of tool wear, and in this way to assess part piece quality. The machining process known as broaching is critical for firtree slots (dovetails) production in turbomachinery components, such as turbine disks. Tight tolerances on one hand, even less than 5 µm in firtree-slots pressure faces, and high productivity on the other, are the two main requirements. Besides, broaching tools are very expensive and the cutting edges wear must be estimated during the process; in fact, tool wear in difficult-to-cut materials machining may cause a waste not only in terms of the tool but also of the very expensive workpieces. Broaching usually is one of the last operations in the process chain, so components start the operation with a very high-added value. Hence, only one bad slot implies an unrecoverable piece and therefore a huge waste of time and money.In this paper, a monitoring method for efficient broaching is proposed by combining real-time monitoring and off-line tool wear inspection. Firstly, the cutting tool characteristics are defined, and those affected by tool degradation. Secondly, some broaching cycles were carried out while measuring a) process accelerations through two accelerometers, b) cutting force by load cells, and c) motor drive consumption. They were simultaneously recorded. Furthermore, the sensitivity between tool wear and broaching process natural frequencies is established.Finally, a series of experimental tests were executed for verification, showing the useful approach for daily life production. The paper focuses on signals and their sensitivity to significant process variations.

Effect of ironing on forming characteristics in the Lorentz-force-driven hole flanging process

Ironing that achieved by reducing the clearance between forming tools have been proved to be able to generate high collar, regular geometry and good formability in conventional flanging process. In this paper, the effect of ironing on flanging characteristics during the Lorentz-force-driven (LFD) hole flanging process were investigated with the use of 5182 aluminum alloy. The ironing phenomenon in the LFD flanging process were realized by decreasing the diameter of die and keeping the punch diameter constant. To reveal the formation mechanism with or without ironing in this high-speed process, the elastoplastic finite element simulation model was established. Typical features in the final profiles, including junction ridge, spring-back, tip inclination, that determined by three critical clearance-thickness ratios ( R cc1 , R cc2 and R cc3 ) were analyzed. Especially, the evolution of spring-back and tip inclination with respect to the varying clearance-thickness ratios ( R c ) were discussed in details. According to three R cc values, ironing identification and ironing extents (mix-ironing and pure-ironing) separation could be achieved at the same time. Based on the analysis of radius, wall and tip in the flanged part, a height calculation method was proposed for the replacement of simulation in flanging cases with R c lowered than R cc2 . The comparison with experimental heights proved the feasibility of prediction formula.

Flame acceleration and deflagration-to-detonation transition in narrow channels filled with stoichiometric hydrogen-air mixture

Understanding flame acceleration (FA) and deflagration-to-detonation transition (DDT) is important for combustion applications. However, DDT is a high-speed, nonlinear and complex process and the exact underlying mechanisms remain unclear, especially for narrow channels with a width smaller than detonation cell size. In this paper, numerical simulations were carried out to study the FA and DDT in a stoichiometric hydrogen-air mixture in narrow channels with width on the order of magnitude comparable to laminar flame thickness. The fully-compressible reactive Navier-Stokes equations were solved by using a high-order numerical method. Hydrogen-air combustion was taken into account using a calibrated simplified chemical-diffusion model. Four different channel widths, i.e., d = 2.0 mm (∼6 δl), 1.0 mm (∼3 δl), 0.5 mm (∼1.5 δl), 0.25 mm (∼0.7 δl), were considered in the simulations to explore the size effect, where δl is the laminar flame thickness. The results show that the FA is mainly determined by boundary layer effects for all the channels considered. In the early stages, the flame keeps accelerating due to the stretching effect of boundary layer that leads to a significant increase in flame surface area. In the later stages of acceleration, an ultra-fast flame develops in the boundary layer ahead of the flame front due to the viscous heating effect associated with wall friction. It was found that the DDT mechanism is essentially consistent in all the channels. Detonation arises from the contact of two neighboring flame fronts in the shocked region that is vulnerable to a mild temperature gradient or fluctuation. The contact of the two high-temperature reaction fronts instantly causes a very high concentration of heat flux and consequently a detonation wave emerges from the contact spot. The detonation propagation after DDT, however, depends on the channel width. When d ≥ 1.5 δl, a quasi-steady or a single-head detonation forms and sustains until the end of the combustion. For the case of d < 1.5 δl, the detonation decays into a high-speed flame. When the channel width is sufficiently small, e.g., d ∼0.7 δl, detonation initiation can occur occasionally, but soon decouples into a shock and a flame.

Role of H2 and Ar as the diluent gas in continuous hot-wire CVD synthesis of SiC fiber

W-core SiC fiber was synthesized with CH3SiCl3 as the precursor by continuous hot-wire CVD approach. Using H2 and Ar as the diluent gas, the temperature profile and the production of atomic hydrogen (H) in high-speed deposition process were studied by computational flow dynamics (CFD) simulation, and the growth kinetics and microstructure of the deposit were systematically investigated. H2 significantly increases the H production, which reduces the formation of amorphous phase and structural defects (e.g. stacking faults and twins) during SiC growth. Ar could establish a steep thermal gradient in reactor, which enhances the deposit’s surface quality. The mean tensile strength of SiC fiber reaches its peak value (3.15 GPa) with H2 at 1200 sccm, and a high Weibull modulus (14.7) is achieved with Ar at 1600 sccm. These findings indicate H2 is crucial to promote the mechanical performance of SiC fiber, while Ar is beneficial to improving its uniformity.

A review on environmental friendly cutting fluids and coolant delivery techniques in grinding

Grinding is a very high-speed machining process, specifically, it is complex and often fails to achieve the accuracy, coolants are necessary for grinding to achieve the desired production rates. Coolant disposal is a serious issue since it poses a risk to the environment and land pollution. To reduce the friction and of frictional heating during grinding, suitable coolants and lubrication systems should be used, therefore, many approaches to eco-friendly coolant delivery techniques are been illustrated. Continuous long-term scientific research is needed toward green machining. “Go green, think green, and act green” statement should be followed in the industry during production and manufacturing. This literature survey was needed because it highlights previous and present research work on eco-friendly fluid delivery techniques, also the study explained how important this method will play in considering the future environment and workers’ health.

Formation of nanostructured surface layer, the white layer, through solid particles impingement during slurry erosion in a martensitic medium-carbon steel

The extremely altered topmost surface layer, known as the white layer, formed in a medium-carbon low-alloy steel as result of impacts by angular 10–12 mm granite particles during the slurry erosion process is comprehensively investigated. For this purpose, the characteristics, morphology, and formation mechanism of this white layer are described based on the microstructural observations using optical, scanning and transmission electron microscopies as well as nanoindentation hardness measurements and modelling of surface deformation. The white layer exhibits a nanocrystalline structure consisting of ultrafine grains with an average size of 200 nm. It has a nanohardness level of around 10.1 GPa, considerably higher than that of untempered martensitic bulk material (5.7 GPa) achieved by an induction hardening treatment. The results showed that during the high-speed slurry erosion process, solid particle impacts brought forth conditions of high strain, high strain rate, and multi-directional strain paths. This promoted formation of a cell-type structure at first and later, after increasing the number of impacts, development of subgrains following by subgrain rotation and eventually formation of a nanocrystalline structure with ultra-high hardness. The model confirmed that high strain conditions - much higher than required for the onset of plastic deformation - can be achieved on the surface resulting in severe microstructural and property changes during the slurry erosion test.

In-situ transfer vat photopolymerization for transparent microfluidic device fabrication

While vat photopolymerization has many advantages over soft lithography in fabricating microfluidic devices, including efficiency and shape complexity, it has difficulty achieving well-controlled micrometer-sized (smaller than 100 μm) channels in the layer building direction. The considerable light penetration depth of transparent resin leads to over-curing that inevitably cures the residual resin inside flow channels, causing clogs. In this paper, a 3D printing process — in-situ transfer vat photopolymerization is reported to solve this critical over-curing issue in fabricating microfluidic devices. We demonstrate microchannels with high Z-resolution (within 10 μm level) and high accuracy (within 2 μm level) using a general method with no requirements on liquid resins such as reduced transparency nor leads to a reduced fabrication speed. Compared with all other vat photopolymerization-based techniques specialized for microfluidic channel fabrication, our universal approach is compatible with commonly used 405 nm light sources and commercial photocurable resins. The process has been verified by multifunctional devices, including 3D serpentine microfluidic channels, microfluidic valves, and particle sorting devices. This work solves a critical barrier in 3D printing microfluidic channels using the high-speed vat photopolymerization process and broadens the material options. It also significantly advances vat photopolymerization’s use in applications requiring small gaps with high accuracy in the Z-direction.

Surface Finish Comparison of Dry and Coolant Fluid High-Speed Milling of JIS SDK61 Mould Steel

This paper investigates the influence of dry high-speed milling on the surface quality of JIS SKD61 hard steel, compared to the conventional coolant fluid method. This research was conducted in a Super MC 500 high-speed CNC milling machine with a Hitachi coated carbide 20mm in diameter. High-speed cutting parameters such as cutting speed V, cutting depth t, and spindle speed S were considered as variants. The experiment was designed based on Taguchi's L9. Surface quality, including Ra and Rq, was measured using the Mitutoyo Surftest SV-210. A mathematical regression model was found for the average values of surface roughness through regression analysis for dry and coolant fluid conditions. The chosen high-speed milling parameters and the respective Ra and Rq values were obtained by ANOVA. The grey relation scores for wet and dry milling surface quality for cut depth, feed rate, and cutting speed were 0.7527, 0.7869, 0.6302, and 0.8167, 0.7199, 0.6040, respectively. The results showed that the feed rate had the greatest influence on the surface quality during the high-speed coolant milling of hardened steel, while the depth of the cut had the greatest influence on the surface quality during the high-speed dry milling process.

Improvement of welding stability and mechanical properties of galvanized DP800 steel lap joint by high-speed tandem beam laser

Dual beam laser welding has shown promise to improve the weldability of galvanized dual phase steels. In this study, the lap joints of galvanized dual phase steel were welded with tandem beam laser at speed up to 100 mm/s. The power ratio for the dual beams was set to 50%:50%, 40%:60%, 30%:70%, and 20%:80%, respectively. A high-speed camera was used to observe the dynamic process of zinc vapor, molten pool, and keyhole behaviors under different welding conditions. The corresponding metallographic and mechanical analysis were conducted to reveal the effects of variable welding thermal cycles on the microstructures and properties of the welded joints. The results indicate that the fusion zone (FZ) is composed of blocky-lath martensite, whereas the heat-affected zone (HAZ) is characterized by the lath microstructure containing tempered martensite (TM) and ferrite (F). The power ratio of dual beams significantly affects the microstructures and hardness profiles of welded joints. It also influences the zinc-vapor and molten pool dynamic behaviors, thus affecting the weld bead formation. The weight of spatter decreases with the decrease of leading beam power in tandem beam laser welding process. In addition, the mechanical properties of the welded lap joints are significantly affected by the high-speed tandem dual beam laser welding process parameters. The failure load of tensile-shear testing reaches the maximum value when the beam power ratio is 30%:70%.

Intelligent computational of Experimental Study of Intermittent Feed High-speed Grinding Method utilising PSO basis FEM Solver

ABSTRACT The high-speed grinding and polishing machine can not only significantly increase the performance of grinding but also improve the consistency of processing effectively. It is one of the most significant guidelines for the advancement of grinding technology today. Since the high-speed grinding technology has been booming these days, this study develops intermittent high-speed grinding technique for feed which has been under the basic high-speed grinding process. Using a simple list of a straight line, a piece of work can be easily retreated and fed. By affordable arrangement distance of feed-in single grinding, time of action on grinding work piece and grinding wheel has been reduced, it will affect the process of grinding heat sending that does not get fixed sate, it was decreasing grinding temperature at the time of single grinding, the surface temperature was freezer to the closed room temperature throughout the room. The lower grinding temperature was achieved according to this path. The simulation study and experiment were performed on TC4 titanium alloy materials in intermittent high-speed feed grinding, and critics of grinding elements considered grinding temperature along with grinding force have been implemented as end production using finite element analysis of the particle swarm optimization (PSO) basis.