Pulling Speed Research Articles

Role of viscoelasticity in the adhesion of mushroom-shaped pillars

The contact behaviour of mushroom-shaped pillars has been extensively studied for their superior adhesive properties, often inspired by natural attachment systems observed in insects. Typically, pillars are modeled with linear elastic materials in the literature; in reality, the soft materials used for their fabrication exhibit a rate-dependent constitutive behaviour. Additionally, conventional models focus solely on the detachment phase of the pillar, overlooking the analysis of the attachment phase. As a result, they are unable to estimate the energy loss during a complete loading-unloading cycle.
This study investigates the role of viscoelasticity in the adhesion between a mushroom-shaped pillar and a rigid flat countersurface. Interactions at the interface are assumed to be governed by van der Waals forces, and the material is modeled using a standard linear solid model. Normal push and release contact cycles are simulated
at different approaching and retracting speeds.
Results reveal that, in the presence of an interfacial defect, a monotonically increasing trend in the pull-off force with pulling speed is observed. The corresponding change in the contact pressure distribution suggests a transition from short-range to long-range adhesion, corroborating recent experimental and theoretical investigations.
Moreover, the pull-off force remains invariant to the loading history due to our assumption of a flat-flat contact interface. Conversely, in the absence of defects and under the parameters used in this study, detachment occurs after reaching the theoretical contact strength, and the corresponding pull-off force is found to be rate
independent. Notably, the hysteretic loss exhibits a peak at intermediate detachment speeds, where viscous dissipation occurs, which holds true in both the presence and absence of a defect. However, the presence of a defect shifts the region where the majority of viscous dissipation takes place.

In vitro quantification of the resistance force properties of a hydraulic resistance device designed for sprinting

The hydraulic resistance device (HRD), a state-of-the-art device developed primarily for resisted sprint training, lacks exploration of its force-generating properties. This technical note aims to evaluate these properties in vitro. In a laboratory experiment, the HRD was pulled with a motorised winch at four speeds (1–4 m s−1) and 12 different HRD resistance levels (low, medium and high). The resistance force induced by the HRD was measured using a force plate mounted under the device, and calculated as mean horizontal force produced at a constant pulling speed. Resistance force repeatability between pulling speeds at specific resistance levels was assessed using the coefficient of variation (CV) whereas the intraclass correlation coefficient (ICC3,1) was calculated to determine the consistency. A linear regression model quantified resistance force as a function of HRD resistance level. Accuracy of the model was assessed using root mean square error (RMSE). Across 12 resistance levels, the HRD produced resistance forces ranging from 22.57 ± 4.84 to 164.57 ± 4.84 N. The CV decreased from 21.5% at the lowest resistance to 0.4% at the highest. The HRD produced resistance force with high consistency (ICC3,1 CI = 0.990–0.999). The linear regression model showed a near-perfect fit ( R2 = 0.99) and predicted resistance force more accurately at medium and high resistance (RMSE range = 0.97–4.57 N). The HRD provides favourable force-generating properties for resisted sprint training and testing, warranting further studies on its exploration in vivo.

Numerical simulation study on solidification proceoss of titanium slab ingot by electron beam cold hearth melting

Abstract Titanium and titanium alloys are key basic support materials in the field of engineering technology and high technology, and are widely used in the fields of natural gas transportation, chemical corrosion, and marine development. Titanium alloy ingots are often prepared with more solidification defects such as surface cracks and cold shuts, resulting in lower utilization of titanium metal and higher cost of titanium products. The root of this is the lack of in-depth knowledge of the ingot melting and casting process, and the failure to control the thermal conditions of the billet in the molding process within a reasonable range. In this study, based on the Lagrange Euler algorithm, combined with ProCAST finite element software to establish a numerical model, revealing the solid-liquid interface morphology, the length of the transition region, and the change rule of thermal stress under the influence of different process parameters in the solidification process of titanium slab ingot. The results show that with the increase in pulling speed, the depth of the solid-liquid phase line and the width of the mushy zone of slab ingot increase, and the length of the transition region grows. With the increase in casting temperature, the depth of the solid-liquid phase line of the slab ingot decreases, and the mushy zone gradually becomes narrower. The casting temperature and pulling speed are positively correlated with the value of the thermal stress equivalent stress in slab ingots, and the probability of cracks in the corners and ingot surface is higher. This study provides effective theoretical guidance for the realization of stable mass production of high-quality titanium slab ingot.

Accumulation of Hydrogen Bonds and van der Waals Interactions Determines Force Response between Two Parallel Cellulose Chains: Steered Molecular Dynamics Simulations.

We investigated the response forces between two parallel cellulose chains during the shearing and tearing processes by using steered molecular dynamics simulations. It was found that there are two logarithmic dependencies between response force and pulling speed in shearing processes but only one in tearing, according to Bell's equation by fitting the f-ln v curve. The mechanism is that there are 2-fold interactions determining the force response between two parallel cellulose chains resisting chain separation during a shearing process. Our results indicate that hydrogen bonds dominate the interchain interactions in the fast pull mode (FPM) for shearing, while van der Waals interactions dominate in the slow pull mode (SPM). For tearing, the one-by-one breaking of hydrogen bonds and van der Waals interactions plays a main role.

Morphological diversity in directionally-solidified microstructures with varying anisotropy of solid-liquid interfacial free energy

Morphological diversity in directionally-solidified microstructures of fcc-based binary alloys was investigated using quantitative phase-field simulation. The growth morphology for each set of anisotropy parameters was identified from the degree of undercooling of the dendrite tip and a morphology map was constructed. We investigated the effects of solidification conditions and alloy systems on growth morphology and found that the pulling speed has a significant effect, while temperature gradient and partition coefficient have only small effects on the morphology selection. Furthermore, we examined the emergence of doublon and triplet dendrites under conditions of weak interfacial anisotropy.

A Soft Measurement Method for the Tail Diameter in the Growing Process of Czochralski Silicon Single Crystals

In the Czochralski silicon single crystal growth process, the tail diameter is a key parameter that cannot be directly measured. In this paper, we propose a real-time soft measurement method that combines a deep belief network (DBN) and a support vector regression (SVR) network based on system identification to accurately predict the crystal diameter. The main steps of the proposed method are as follows: First, we address the delay problem of the effects of the temperature and crystal pulling speed on the tail diameter growth by using a back propagation (BP) neural network based on the mean impact value (MIV) method to determine the optimal delay time. Second, we construct a prediction model of the tail diameter by using the DBN network with the temperature and crystal pulling speed as input variables in the crystal growth process. Third, we improve the DBN network by using the SVR network to enhance its linear regression capability. We also employ the ant colony optimization (ACO) algorithm to obtain the optimal parameters of the SVR network. Finally, we compare the performance of the DBN-ACO-SVR network based on system identification with the DBN and SVR networks, and the results show that our method can effectively deal with the delay problem and achieve the accurate prediction of the tail diameter in the Czochralski silicon single crystal growth process.

Optimization of Thermoplastic Pultrusion Parameters of Jute and Glass Fiber-Reinforced Polypropylene Composite.

Thermoplastic pultrusion is a suitable process for fabricating continuous unidirectional thermoplastics with a uniform cross-section, high mechanical properties due to continuous fiber reinforcement, low cost, and suitability for mass production. In this paper, jute and glass fibers were reinforced with a polypropylene matrix and fabricated using the thermoplastic pultrusion process. The volumetric fraction of the composite was designed by controlling the filling ratio of the reinforcing fiber and matrix. The effects of molding parameters were investigated, such as pulling speed and molding temperature, on the mechanical properties and microstructure of the final rectangular profile composite. The pulling speed and molding temperature varied from 40 to 140 mm/min and 190 to 220 °C, respectively. The results showed that an increase in molding temperature initially led to an increase in mechanical properties, up to a certain point. Beyond that point, they started to decrease. The resin can be easily impregnated into the fiber due to the low viscosity of thermoplastic at high temperatures, resulting in increased mechanical properties. However, the increase in molding temperature also led to a rise in void content due to moisture in jute fiber, resulting in decreased mechanical properties at 210 °C. Meanwhile, un-impregnation decreased with the increase in molding temperature, and the jute fiber began to degrade at high temperatures. In the next step, with varying pulling speed, the mechanical properties decreased as the pulling speed increased, with a corresponding increase in void content and un-impregnation. This effect occurred because the resin had a shorter time to impregnate the fiber at a higher pulling speed. The decrease in mechanical properties was influenced by the increase in void content and un-impregnation, as the jute fiber degraded at higher temperatures.

Numerical study of continuous Czochralski (CCz) silicon single crystal growth in a double-side heater

The effect of heater power control on heat, flow, and oxygen transport for the CCz growth of 8-inch diameter silicon crystal in a triple-crucible was numerically studied. Three different designs of a double-side heater at different power ratios of the lower and upper side heaters (PRSD = 0.25, 1, and 4) were compared with the case of a single-side heater. For the cases considered in the present work, a design in which the upper side heater was shorter than the lower one at PRSD = 0.25 could be a good choice for improving the crystal quality and CCz growth. This was shown by the reductions in the crystal-melt interface deflection and oxygen content and the increase in the melt temperature in the feeding zone. In this case, reducing the interface deflection and crucible bottom wall temperature could enhance the pulling speed. However, the power consumption in this condition was higher than that in the single-side heater case. Achieving a lower heater power was feasible with a higher PRSD value. However, it was important to note that the oxygen content would be higher, and the melt temperature in the outer melt significantly dropped.

Pultrusion of thermoplastic composites with mechanical properties comparable to industrial thermoset profiles

Pultruded thermoplastic composite profiles offer several advantages over their conventional thermoset counterparts, such as high impact toughness, recyclability, and smaller environmental footprint. However, thermoset profiles outperform thermoplastic composite profiles in terms of mechanical properties through high fiber volume fraction. The study is aimed at producing thermoplastic profiles with high content of reinforcing fibers, using preconsolidated tapes manufactured in-house from glass fiber/polypropylene commingled yarns with fiber content of 80 % by weight. The tapes were manufactured with the use of extrusion machine at speeds of 2, 5, and 8 m/min under the same temperature conditions. The strip profiles of 75 mm × 3.5 mm with fiber volume fraction of 50 % were produced of 76 tapes by thermoplastic pultrusion process at the pulling speed of 0.2 m/min. The results of mechanical tests show that flexural strength and modulus of obtained thermoplastic profiles exceed minimal requirements to industrial thermoset profiles, constituting at least 488 MPa and 37 GPa respectively. Thermoplastic profile pultrusion from tapes made of commingled yarns does not require the use of a preheating chamber, produces profiles with 1 % porosity, and more energy efficient pultrusion process than pultrusion from commingled yarns.

Rate-dependent adhesion together with limb collaborations facilitate grasshoppers reliable attachment under highly dynamic conditions

Dynamic attachment is indispensable for animals to cope with unexpected disturbances. Minor attention has been paid to the dynamic performance of insects' adhesive pads. Through experiments pulling whole grasshoppers off a glass rod at varying speeds, surprising findings emerged. The feet did not always maintain contact but released and then reconnected to the substrate rapidly during leg extension, potentially reducing the shock damage to pads. As the pulling speeds increased from 1 to 400mm/s, the maximum forces of single front tarsus insects and entire tarsi insects were nearly proportional to the 1/3 power of pulling speeds by 0.11 and 0.29 times, respectively. The force of some individuals could be even 800 times greater than their weight, which is unexpectedly high for smooth insect pads. This work not only helps us to understand the attachment intelligence of animals but is also informative for artificial attachment in extreme situations.

Optimizing thermoplastic pultrusion parameters for quality long fiber thermoplastic pellets in glass fiber-reinforced polypropylene

A long fiber thermoplastic pellet (LFTP) is a pellet that contains discontinuous fibers reinforced in thermoplastic. In this experiment, LFTPs were produced using the thermoplastic pultrusion process. The thermoplastic pultrusion process is uncomplicated in terms of the machine device, and it can improve the impregnation quality of LFTP. Glass fiber was used as the reinforced fiber, and PP fiber was used as the matrix. This experiment studied the effect of molding temperature and pulling speed on impregnation. The die system contained six heating zones. In the first step, zones 3 and 4 (melting zone) were varied at 200, 210, 220, and 230°C. The melting zone that exhibited good results was selected for the next step. In the second step, zones 5 and 6 (heat reduction zone) were varied at 160°C–190°C and 150°C–180°C, respectively. After determining the optimal molding temperature, the pulling speed was studied, with speeds varied at 10, 20, 30, 40, and 50 cm/min. The impregnated quality of the LFTP was investigated through microstructure analysis. A data logger was used to record the temperature profile in the pultrusion die. Furthermore, the impregnation quality and microstructure of LFTP from thermoplastic pultrusion were compared to commercial LFTP. The results showed that un-impregnation decreased with an increase in the melting zone temperature. In the heat reduction zone, un-impregnation decreased with a decrease in temperature. For the pulling speed, un-impregnation decreased with a decrease in speed. The optimal die system had a melting zone temperature of 230°C and a heat reduction zone temperature of 160 and 150°C. The optimal pulling speed was 10 cm/min, resulting in an un-impregnation rate of 8.06%. Additionally, commercial LFTP had an un-impregnation rate of 13.73%.

Design and Testing of a Clamping Manipulator for Removing Abnormal Plants in Rape Breeding

Aiming at the time-consuming, laborious, and inefficient process of removing abnormal rape plants during breeding, combined with the agronomic requirements for planting rapeseed, a clamping manipulator was designed. This manipulator is mainly composed of hollow splints, grip-force sensors, connecting rods, cylinders and other components. Additionally, a removing test platform was built. Single-factor and Box-Behnken experiments were conducted. Taking the output air pressure, pulling angle and pulling speed as the test factors, the rape uprooted removal rate, rape removal breakage rate and pulling force were the test indicators. Mathematical models for multiple regression were established separately for each evaluation index, and analysis of variance was conducted. Objective optimization was performed using the Numerical component to obtain the optimal combination of operating parameters: output air pressure of 0.47 MPa, pulling angle of 68.8° and extraction speed of 8 cm/s. The field validation test showed that the uprooted removal rate was 83.33%, the removal breakage rate was 6.67% and the pulling force was 84.9 N at the output air pressure of 0.5 MPa, pulling angle of 70° and pulling speed of 8 cm/s. The validation test values are in good agreement with the parameter optimization values, indicating that the parameter optimization model is reasonable.

Experimental and numerical analyses of the thermoplastic pultrusion of large structural profiles

The selection of optimal process conditions is very important for the production of large pultruded thermoplastic profiles. This study investigates the influence of pulling speed on the temperature distribution and consolidation of glass fiber/polypropylene (GF/PP) preconsolidated tapes during thermoplastic pultrusion. For this purpose, several pultruded thermoplastic profiles with a cross-section of 75 mm × 3.5 mm were produced at various pulling speeds, and their cross-sections were studied under a microscope. In addition, a 3D numerical model was developed to analyze the influence of the pulling speed on the temperature distribution and to predict the consolidation of the tapes. Full consolidation of the tapes was observed in the profiles produced at a pulling speed of 0.2 m/min. The profiles produced at a pulling speed of 0.4 m/min contained unconsolidated tape, which resulted in reduced flexural, tensile, and compressive strengths by as much as 43%, 15%, and 23%, respectively. The results of the simulations and microscopic investigations show that the GF/PP tapes consolidate at temperatures above the Vicat softening temperature. Finally, a GF/PP tube with dimensions of 50 mm × 40 mm × 5 mm was produced using the optimum pulling speed and temperature determined using the developed 3D model. These results provide valuable insight into the design of thermoplastic pultrusion regimes.

The Effect of Pulling Speed on the Structure and Properties of DZ22B Superalloy Blades

DZ22B alloy is commonly used as a blade material for aircraft engines and gas turbines, and its preparation process is an important factor affecting its performance. In the present work, a reliable numerical model is established through ProCAST numerical simulation and auxiliary experimental verification methods, based on which the effect of casting speed on the grain and dendrite growth of DZ22B superalloy blades is studied. The results indicate that increasing the pulling speed can reduce the spacing between secondary dendrites, which is beneficial for the growth of dendrites. Based on numerical simulation and experimental verification, it is suggested that the pulling rate of the directional solidification DZ22B superalloy blade should be 6-2mm/min variable speed pulling to improve the production success rate.

Development of a Control System for a Technological Line for the Production of Products from Foamed Polysty

Purpose of research. When designing new and modernizing existing control systems for the polymer drawing process, an important role is played by solving the problems of creating mathematical or simulation models and synthesizing control algorithms that reduce the share of manual labor. The article provides an overview of approaches to the development and modeling of automated control systems for extrusion production lines for the production of polymer products. The possibility of developing and modeling a multidimensional control system for the process of stretching foamed polystyrene based on the Matlab mathematical analysis package is considered. The relevance of the research topic is related to the trend of growth in the consumption market and the implementation of management in the context of creating more complex forms of packaging from polymers.Methods. For the development of the control system and its analysis, the fundamentals of the theory of multidimensional systems in control problems, the theory of plastics processing, methods of computer simulation of control systems were applied.Results. The article presents an algorithm for controlling the molding process and its implementation in the Simulink environment. Graphs of changes in the pulling speed and winding speed, changes in the thickness and tension of the web over time are presented and analyzed. A scheme of process line automation based on the developed algorithm is presented.Conclusion. The results of testing the model show that the use of mathematical modeling of the control system for stretching the expanded polystyrene web is possible to solve the problem of increasing production efficiency on existing equipment, which will bring their characteristics closer to new production lines, leaving the mechanical part unchanged. The significance of the work is due to the fact that the use of modern control systems can improve the quality of manufactured products, reduce the consumption of raw materials. Materials and research methods can be applied in the development of projects for other installations, for example, in the production of an optical sheet.

Stability of interfacial thermal balance in thick β-Ga2O3 crystal growth by EFG

When n-type β-Ga2O3 crystals with large thickness are grown by edge-defined film-fed growth (EFG), fusing often occurs, due to the massive release of latent heat of crystallization and infrared absorption of crystals, which affects the integrality and quality of crystals. In order to solve this problem, a furnace structure with larger axial temperature gradient (from 17.40 K/mm to 27.46 K/mm) over the die was designed by ANSYS FLUENT software. Considering the interface thermal and the pressure balance of the meniscus, the relationship between the overheating temperature on the upper surface of the die and the pulling speed was calculated. It is found that the overheated fusing starts from the center of the crystal and then to the edge, which is consistent with the actual growth of the crystal. The pulling speed of 20 mm/h was selected for the growth experiment. Through the optimization of thermal field environment and the selection of pulling speed, high-quality two-inch β-Ga2O3 crystals without overheat fusing was realized. This work provides more help for understanding β-Ga2O3 crystal growth by EFG.

Chain Sliding versus β-Sheet Formation upon Shearing Single α-Helical Coiled Coils.

Coiled coils (CCs) are key building blocks of biogenic materials and determine their mechanical response to large deformations. Of particular interest is the observation that CC-based materials display a force-induced transition from α-helices to mechanically stronger β-sheets (αβT). Steered molecular dynamics simulations predict that this αβT requires a minimum, pulling speed-dependent CC length. Here, de novo designed CCs with a length between four to seven heptads are utilized to probe if the transition found in natural CCs can be mimicked with synthetic sequences. Using single-molecule force spectroscopy and molecular dynamics simulations, these CCs are mechanically loaded in shear geometry and their rupture forces and structural responses to the applied load are determined. Simulations at the highest pulling speed (0.01nm ns-1 ) show the appearance of β-sheet structures for the five- and six-heptad CCs and a concomitant increase in mechanical strength. The αβT is less probable at a lower pulling speed of 0.001nm ns-1 and is not observed in force spectroscopy experiments. For CCs loaded in shear geometry, the formation of β-sheets competes with interchain sliding. β-sheet formation is only possible in higher-order CC assemblies or in tensile-loading geometries where chain sliding and dissociation are prohibited.

Czochralski (CZ) process modification with cooling tube in the response to market Global silicon shortage

Recently, the silicon wafer producers, affected by Covid-19 and USA-China competition, looks for new production processes to increase the production. On the other hand, the common parts of CZ puller such as heater, crucible and thermal shield are optimized over time and now the common CZ process is reached to limitation for further improvement. Here, we propose a modified CZ method by adding a cooling tube into the growth zone. The new proposed Cz method is applied to the 8″ crystal growth process. A fully 3D transition model including energy equation, Navier–Stokes equation, surface-to-surface radiation heat transfer, moving mesh and thermal stress equations is implemented. The simulation is performed for both original and new CZ method. It was proved that the new CZ method increases the pulling speed up to 25 %. To ensure about the crystal quality, the thermal stress is compared between original and new proposed CZ method. Although it was found that the thermal stress increases about twice but still the maximum von Mises stress never exceeds the critical value 25 MPa. Additionally, the power consumption is also found to enhance maximum 2 kW under new conditions. To evaluate the model the interface and heater power for the original CZ puller is compared with industrial CZ process and it shows acceptable accuracy.

Sensitivity enhancement of gold nanospheres assisted CO2 laser tapered optical fiber for refractive index sensor

Tapered optical fibers (TOFs) have been intensively used as sensors due to their high sensitivity, simple structure, and excellent coupling efficiency. In this paper, we reported the successful rapid tapering of single mode and multimode fibers using CO2 laser beam at working wavelength of 10.6 μm. Clean and symmetric tapers could be produced in just 5 s using this method. Arduino-based microcontroller was included in the tapering set-up to precisely control the fiber pulling speed and distance. Smaller waist diameters that were observed in multimode than in single mode fibers generated more evanescent waves on the cladding of tapered multimode fibers (TMMFs). This implied that TMMFs performed better refractive index (RI) sensitivity, within the range of 1.3325–1.4266, than tapered single mode fibers (TSMFs). Furthermore, localized surface plasmon resonance (LSPR) effect was coupled with evanescent wave through AuNSs immobilization on the TOF surface. The AuNSs having average particle diameter of 12.70 nm was synthesized by citrate reduction route. The formation of AuNSs was confirmed by (ultraviolet–visible) UV–vis and high-resolution transmission electron microscopy (HRTEM) data. Self-assembly monolayer approach was conducted to immobilize AuNSs on the 3-mercaptopropyl trimethoxysilane (MPTMS)-functionalized surface of the TOFs. The AuNSs immobilization on TMMFs could improve the sensitivity up to 122 %. Besides sensitive to RI changes, the sensors were also excellent in terms of repeatability and reversibility performances. Finally, this paper described the amplitude modality-based RI sensing mechanism due to evanescent wave and LSPR effects.

Bi-LSTM-Based Dynamic Prediction Model for Pulling Speed of Czochralski Single-Crystal Furnace

Abstract With the rapid development of microelectronics science and technology, the quality of IC-grade silicon single crystal directly affects the yield and stability of the performance of semiconductor device production. As the main equipment for the preparation of such materials, the monitoring and maintenance of the working condition of the single crystal furnace are crucial. Bi-directional long short-term memory (Bi-LSTM) is an innovative neural network paradigm that is used to predict future occurrences by learning the bi-directional long-term dependencies of time-steps and serial data. This paper built a Bi-LSTM based model that can dynamically predict the pulling speed of a Czochralski (Cz) single-crystal furnace by modeling the time series of operational parameters. The Bi-LSTM model is validated using real data from a silicon single-crystal factory. It is proven that the model achieved higher accuracy than LSTM, ANN, SVR, and XGBOOST. The experimental results verify the validity of modeling the pulling speed of single-crystal furnace devices through the Bi-LSTM model by using the time series of multi-dimensional parameters. Therefore, the Bi-LSTM model can serve as a reference for modeling the parameters of such devices.