Induced side-branching in smooth and faceted dendrites: theory and phase-field simulations

The present work is devoted to the phenomenon of induced side branching stemming from the disruption of free dendrite growth. We postulate that the secondary branching instability can be triggered by the departure of the morphology of the dendrite from its steady state shape. Thence, the instability results from the thermodynamic trade-off between non monotonic variations of interface temperature, surface energy, kinetic anisotropy and interface velocity within the Gibbs–Thomson equation. For the purposes of illustration, the toy model of capillary anisotropy modulation is prospected both analytically and numerically by means of phase-field simulations. It is evidenced that side branching can befall both smooth and faceted dendrites, at a normal angle from the front tip which is specific to the nature of the capillary anisotropy shift applied. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

Microstructure and Characterization of Ti-Al Explosive Welding Composite Plate

In order to study the interface characteristics and microstructure formation of Ti-Al composite plate, explosive welding was carried out with TA2 titanium as the fly plate and 5083 aluminums as the base plate. Optical microscope and electron microscope were used to analyze the microstructure of intermetallic compounds. SPH method was used to simulate the welding process of composite plates. The formation conditions and initial defects of intermetallic compounds were analyzed. The results show that most of the melted metal in the wave-front stays in the wave-waist region, and there was a relative velocity difference between the vortex and the titanium tissue, which led to the existence of small pieces of fragmentation. The outer layer of the vortex had higher velocity than the inner layer. The formation of Ti3Al, its antioxidant capacity wound lead to the formation of cracks. The temperature of outer vortex was higher than that of inner vortex, and the vortex has a transition layer of 5 μm, which is thinner than the transition layer of 8 μm between cladding plate and substrate. The jet was mostly composed of aluminum metal, and the interface jet velocity reaches 3000 m·s-1 and the interface temperature reaches up to 2100 K. Compared with the molten metal in the wave-back vortex, the jet temperature at the interface was higher, resulting in a thicker transition layer at the bonding surface. The residual stress at the interface wound cause the density of the material to increase.

Dimensional analysis and ANN simulation of chip-tool interface temperature during turning SS304

Introduction. During machining, the resulting temperature has a wider and more critical impact on machining performance. During machining, the power consumption is mainly converted into heat near the cutting edge of the tool. Almost all the work performed during plastic deformation turns into heat. Researchers have put a lot of effort into measuring the cutting temperature during machining, as it significantly affects tool life and overall machining performance. The purpose of the work: to investigate the temperature of the chip-tool interface, taking into account the influence of cutting parameters and the type of tool coating during SS304 turning. The chip-tool interface temperature is measured by changing the cutting speed and feed with a constant cutting depth for uncoated and PVD single-layer TiAlN and multi-layer TiN/TiAlN coated carbide tools. In addition, an attempt is made to develop a model for predicting the temperature of the chip-tool interface using dimensional analysis and ANN simulating to better understand the process. The methods of investigation. Experiments are carried out with varying the cutting speed (140-260 m/min), feed (0.08-0.2 mm/rev) and a constant cutting depth of 1 mm. The chip-tool interface temperature is measured using the tool-work thermocouple principle. The Calibration Setup is designed to establish the relationship between the produced electromotive force (EMF) and the cutting temperature during machining. Statistical dimensional analysis and artificial neural network models have been developed to predict the temperature of the chip-tool interface. Tangential cutting force and chip attributes such as chip width and thickness are also measured depending on the cutting conditions, which is a prerequisite for dimensional analysis simulation. Results and Discussion. A tool made of TiAlN carbide with PVD coating had a lower temperature at the chip-tool interface than a tool with TiN/TiAlN coating. It has been observed that the chip-tool interface temperature increases prominently with the cutting speed, followed by the chip cross-sectional area and the specific cutting pressure. However, a lower cutting force was observed when using a carbide tool with a multi-layer TiN/TiAlN coating, which can be attributed to a lower coefficient of friction created by the front surface of this tool for flowing chips. On the other hand, the greatest cutting force was observed in uncoated carbide tools. It was noticed that the developed models allow predicting the temperature of the chip-tool interface with an absolute error of 5%. However, the lowest average absolute error of 0.78% was observed with the ANN model and, therefore, can be reliably used to predict the chip-tool interface temperature during SS304 turning.

SLIDING FRICTION WEAR BEHAVIOUR OF SEASHELL PARTICULATE REINFORCED POLYMER MATRIX COMPOSITE – MODELING AND OPTIMIZATION THROUGH RSM AND GREY WOLF OPTIMIZER

In this work, the friction wear behaviour of seashell particles reinforced in thermoplastic polymer Nylon-6 is investigated.. Seashells were collected from the seashores, uniform size 75 µm is obtained using mechanical ball milling and vibrating sieve. Various proportions of seashells such as 12, 15 and 18% by weight are added to nylon-6 and the polymer composites wear performance in dry sliding is studied as per ASTM G99 standard, loss of material in wear, friction coefficient and interface temperature are optimized. For experiment design Response surface methodology (RSM) based Box-Behnken method (BBD) is adopted and multi-objective analysis is performed using desirability analysis. Observation shows that interface temperature is highly influenced by rotational speed (41.61%), % reinforcement of seashells influences the wear loss significantly (35.71%) and coefficient of friction is influenced greatly by rotational speed (41.48%)and % reinforcement of seashells (18.18%). A novel metaheuristic algorithm Grey wolf optimizer is used for constrained optimization, which shows that for 0.3 CoF and 25°C interface temperature as constraint wear loss is 35.77 microns for % reinforcement of seashell as 3.59, whereas for 0.3 CoF and 30°C interface temperature wear loss is 28.99 microns for a seashell reinforcement of 18%.

Simultaneous Estimation of Genotoxic Impurities 4-Nitrobenzene Trifluoride, 4-Aminobenzene Trifluoride, and Benzo Trichloride in Cinacalcet Hydrochloride by GC-MS/MS Method

The main objective of this study is to develop and validate a novel, fast, and more sensitive gas chromatography-mass spectrometry (GC-MS/MS) method for the simultaneous estimation of 4-Nitrobenzotrifluoride (4-NBTF), 4-Amino-benzotrifluoride (4-ABTF), and Benzotrichloride (BTC) impurities in Cinacalcet hydrochloride (CH). The chromate-graphic separations were performed on a DB-624, 30m × 0.32mm × 1.8µm column with injector temperature of 150°C, and mode of injection is split with asplit ratio 1: 20. The carrier gas used was helium with a flowrate 1.5 mL/min, and theinjection load was 1.0 µL. Mass spectrometry quantitation was achieved by aquadrupole analyser with EI (Electron Ionization) ion source atasource temperature of 250ºC and interface temperature of 250ºC. The retention times for 4-NBTF, 4-ABTF, and BTC were at 6.13, 6.74and 7.64min, respectively. The calibration curve was linear over the concentration ranging from LOQ level to 150 % level with the correlation coefficient (r) of > 0.99. The percentage recovery was found to be within the specified range, i.e., 70.0 to 130.0 for the three impurities. The limit of detection (LOD) was established to 0.19, 0.19, and 0.18 ppm, whereas thelimit of quantification (LOQ) was obtained to 1.14, 1.12, and 1.11 ppm for 4-NBTF, 4-ABTF, and BTC, respectively. The test solutions with impurities were found to be stable in the diluent for 24 hours. A simple GC-MS/MS method was developed and validated for simultaneous estimation of three impurities in CH. The method was accurate, precise, linear, specific, sensitive, robust, and rugged as per ICH guidelines. The method has been applied to the real-time batch analysis and found to be suitable for routine quality control analysis of CH.

Investigation of Bath/Freeze Lining Interface Temperature Based on the Rheology of the Slag

Freeze lining is a solidified layer of slag formed on the inner side of a water-cooled pyrometallurgical reactor, which protects the reactor walls from thermal, physical, and chemical attacks. Because of the freeze lining's high thermal resistance, the reactor heat losses strongly depend on the freeze lining thickness. In a batch process such as slag fuming, the conditions change with time, affecting the freeze lining thickness. Determining the freeze lining thickness is challenging as it cannot be measured directly. In this study, a conceptual framework based on the morphology and microstructure of freeze lining and the rheology of the slag is discussed and experimentally evaluated to determine the freeze lining thickness. It was found that the bath/freeze lining interface lies just below critical viscosity temperature. The growth of the freeze lining is primarily controlled by the mechanical and thermal degradation of the crystals forming at the interface. The bath/freeze lining interface temperature for the measured slag lies in the range of 1035–1070°C.

Molecular dynamics simulation of interface atomic diffusion in ultrasonic metal welding

The formation of a reliable joint between a large number of aluminum strands for battery applications is crucial in automotive industry, especially in the technology of autonomous vehicles. Therefore, in this study, mechanical deformations and diffusion patterns of the mating interface in ultrasonic welding of aluminum were investigated using molecular dynamics simulations. Furthermore, microscopic observations of the joints between aluminum strands from ultrasonic welding illustrating the influence of two process parameters were done. To study the nanomechanics of the joint formation, two aluminum crystallites of different orientations were built. The impact of the sliding velocity and the compression rate of the upper crystal block on the diffusion pattern at the interface of the two crystallites were quantified via the diffusion coefficient. Tensile deformations of several joint configurations were performed to investigate the load-bearing capacity of the solid state bond, taking into account the compression rate, the sliding velocity and the crystallite orientation. The atomic scale simulations revealed that the orientations of the crystallites govern the interface diffusion and the tensile strength of the joint significantly. Furthermore, interface atom diffusion increased with increasing the sliding velocity. Additionally, it was observed that a higher sliding velocity enhances the friction heat generation between the crystallites and significantly increases the interface temperature.

Analysis of the Accuracy of Mass Difference-Based Measurement of Dry Clutch Friction Material Wear

The paper demonstrates that the dry clutch friction plate wear rate, measured based on the plate mass difference method, exhibits a transient behavior after each change of friction interface temperature level. The effect is hypothesized to be caused by a temperature-dependent change in the moisture content/mass level in the friction material. To test this hypothesis, a series of synchronized characterization experiments have been conducted by using two friction plates, one for wear tests and the other for drying in an oven under the same temperature conditions. Based on the analysis of test results, a moisture content compensation procedure, which reduces the transient wear rate from being 100% to being 50% higher compared to stabilized wear rate, is proposed and verified. The gained insights are used to set recommendations on the organization of routine wear characterization experiments aimed at avoiding the effect of moisture content influence on the accuracy of wear measurement. The main recommendations are to minimize the number of temperature target level changes through proper design of the experiment, insert a run-in test after every long test pause, and execute a pre-heat, blind wear test at the beginning of each test day.