Feed Angle Research Articles

Multi-objective optimization for minimize cutting force and power consumption in corn stalk chopping processes

This study was on optimization of the cutting processes for corn stalks, which serve as significant sources of biomass and forage. The reduction of cutting force is crucial for enhancing energy efficiency. Cutting velocity rises, which can lead to significant power usage with minimal shear forces. Therefore, the objective is to minimize both the cutting force and power consumption. To address this multi-objective optimization problem, a modified Taguchi method was employed. Chauvenet's criterion was used to assess the validity of statistical scatter in repeated test data. The test samples had an 81 % moisture content. Through analysis of variance (ANOVA), the optimal chopping process parameters were identified as velocity of 4.4 m/s, approach angle of 30°, and feeding angle of 50°. The refined empirical relationships indicated that the cutting force ranges from 180.55 N to 393.37 N, while the cutting power ranges from 16.81 W to 44.05 W. In a single test, the output responses for the optimal parameter set were 26.32 W for power consumption and 242.60 N for cutting force, both are within the estimated range. The considerable scatter observed in repeated test data is likely due to variations in corn stalk thickness. These findings are valuable for the operation of chopping machines, ensuring minimal cutting force and power consumption when handling corn stalks residues.

A unified geometrical modeling and analysis method for evaluating CFRP machining performance: Cutting geometry space

Carbon Fiber Reinforced Polymer (CFRP) is extensively utilized in the cutting-edge industries, attributed to its superior mechanical performances. The machining performance of CFRP, however, is significantly influenced by its pronounced anisotropy, particularly the fiber orientation. Consequently, Fiber Cutting Angle (FCA) is widely employed to assess the relationships between cutting geometry and machining performance, yet the coupling of cutting orientation and fiber orientation, along with the absence of feeding angle, limits the further exploration into the underlying mechanisms. This article introduced a novel geometrical framework termed “Cutting Geometry Space” (CGS), for modeling CFRP machining process. Incorporating feeding orientation, cutting orientation and fiber orientation, CGS is applied in milling process for an enhanced comprehension of cutting geometry. Additionally, a pragmatic milling experiment is designed, efficiently evaluating the performances of 1092 combinations of CGS parameters in 13 T700-12K/epoxy CFRP specimens. Microscopical observations and morphological analyses reveals four predominant fracture mechanisms in CFRP machining, with fiber-matrix debonding and bending-induced fracture identified as the key contributors to macroscopic cavity formation. A designated "Damage Zone" within the CGS, encompassing a cutting angle range of 90°–270° and a fiber tilt angle of 15°–60°, is identified as a high-risk area for machining-induced surface cavities. Additionally, the impact of feeding orientation on the surface integrity is confirmed and explained by the influence on the equivalent FCA. Furthermore, the study elucidates chatter marks as a phenomenon induced by a confluence of factors, including generalized down milling, high FCA, and a significant effective cutting fiber count. The observed shift in chatter mark with varying feeding angles provides deep insights into the complex dynamics of machining parameters.

Design and Experiment of a Harvesting Header for Wide–Narrow-Row Corn

Aiming to solve the problems of the large harvesting loss and low harvesting efficiency of wide- and narrow-row corn harvesting header in China, a method for the side installation of a header is proposed. A wide–narrow-row corn harvesting header with high working efficiency and low harvesting loss was designed. The collision energy balance equation of corn ears was established. The analysis shows that the kinetic energy change before and after the collision between the ear and the picking plate is the main cause of the shedding of and damage to corn kernels. Based on this, the main structural parameters of the corn harvesting header were designed. Based on the principle of Box–Behnken test, the response surface test was designed. The effects of the plant feeding speed, feeding angle, and rotation speed of a stem pulling roller on harvesting performance were analyzed. The best combination of working parameters was determined: The plant feeding speed was 1.08 m/s, the feeding angle was 52.46°, and the rotation speed of the stem pulling roller was 835.25 r/min. At this time, the grain damage rate was 1.09% and the grain loss rate was 0.14%. The corresponding parameters are verified by experiments. The results show that the grain damage rate was 1.12% and the grain loss rate was 0.14%. The optimization results are essentially consistent with the verification results, which meet the requirements of corn harvesting performance.

Investigation of thermal behavior of powder stream and molten pool during laser-based directed energy deposition

Laser-powder interaction and molten pool evolution are two main physical processes in laser-based directed energy deposition (L-DED), which greatly affect the morphology and quality of the deposition layer. In this research, a comprehensive three-dimensional analytical-numerical model which integrates a laser-powder interaction model and material deposition model is developed to study the multi-physics coupling characteristics in L-DED process. The concentration of the powder stream is modeled based on conservation of mass and is in good agreement with the experimental result which is captured by high-speed camera. The effects of main parameters, including laser power, powder feeding rate, powder feeding angle and defocus length on the laser attenuation and the temperature distribution of the in-flight powder particles are analyzed. The results show that the laser attenuation rate increases from 0.72% to 1.36% with the powder feeding angle increasing from 45 deg. to 65 deg-. However, the laser attenuation rate is almost the same with the defocus length of 25 mm, 35 mm and 45 mm. Moreover, the peak powder temperature on the deposition surface increases with the increase of powder feeding angle and decrease of defocus length. Accordingly, the heat and mass input conditions at the molten pool surface for the material deposition model, including powder mass flux, effective laser intensity and powder temperature are obtained from the laser-powder interaction model. The heat transport and fluid dynamics of the molten pool are discussed based on the calculated results from material deposition model. Finally, the calculated molten pool geometry shows good agreement with the experimental results with the relative error <8.5%. This work is helpful in process optimization from the point of view of adjusting the parameters related to the powder stream and deeper understanding of laser-powder interaction and molten pool evolution during the L-DED process.

A Hybrid Nondominant-Based Genetic Algorithm (NSGA-II) for Multiobjective Optimization to Minimize Vibration Amplitude in the End Milling Process

Aluminium is a noncorrosive, lightweight material used to fabricate parts for the aerospace, automobile, and construction industries. Due to the low-temperature resistance, more heat is generated. At the same time, in machining, tremendous efforts are taken to keep friction and chatter to a minimum and to attain better quality and perfect output, and also more attention is required while selecting the machining process parameters. Spindle speed, rate of feed, radial and axial depth of cut, and radial rake angle of the tool are the parameters utilized to machine aluminium 6063 using the HSS tool on CNC milling to estimate spindle and worktable vibration using a prediction model. In this study, the design of the experiment of the response surface methodology approach is used to create a second-order statistical equation for experimentation with the Design-Expert v12 software. The performance characteristics are analyzed using the ANOVA method. The spindle speed achieved the lowest vibration between 2000 and 3000 rpm. Next, axial and radial depths were the most vibration-affecting parameter compared to the rate of feed and radial rake angle of the tool. To find the best feasible response, the nondominant sorting genetic algorithm II (NSGA II) approach was trained and tested using MATLAB software. Using a Pareto-optimal technique, the optimum worktable vibration ranged from 0.00284 to 0.00165 mm/s2, whereas the spindle vibration ranged from 0.02404 to 0.01336 mm/s2. The predicted values were found to be in an excellent argument when Pareto-optimal solutions are used.

Effects of Welding Parameters on Droplet Transfer and Bead Geometry in Laser Welding with Aluminum and Stainless Steel Filler Wires

Laser welding is increasingly used in industries because it allows high production cycle time and single-sided welding, but is characterized by a high sensitivity to joint preparation. By inserting filler wires, the sensitivity to joint preparation can be suppressed. In this study, the effect of welding variables on the bead geometry and melted droplet transfer were investigated. Two wires with different thermal diffusivities and densities were selected: stainless steel (STS) and aluminum (Al) wires. According to the wire feeding angle, the melting area tended to differ between the STS and Al wires. This implied that the wire feeding angle had to consider the absorption rate of the material for the laser wavelength. With an increase in the distance between the wire tip and the substrate, the dominant force acting on the droplet was changed from surface tension to gravity. Therefore, the distance was considered as a major factor in determining the droplet transfer mode. In all cases, the droplet transfer period exhibited relatively small deviation when the wire feeding direction was leading. Furthermore, the focal length effects on droplet transfer were irrelevant.

Research of Three-High Screw Rolling of Aluminum Billets with Copper Inserts at Different Rolls Feed Angles

Three-high screw-rolling of aluminum alloy ingots was carried out at 12- and 20-degrees rolls feed angles. The ingots had two copper, cylindrical inserts oriented along the ingot axis: the center of one insert coincided with the ingot’s center, and the center of the other insert coincided with the ingot’s half-radius. The effect of the rolls feed angle value on the aluminum and copper microstructure as well as the hardness formation was established. X-ray study and three-dimensional modeling allowed the copper insert twisting angle to be estimated along the rolled billet axis. It also allowed detection of the number of breaks of the insert located in the ingot’s center and the insert located in the ingot’s half-radius depending on the rolls feed angle value.

Multi-objective optimization of process parameters during friction stir welding of similar AA6061 using MOORA

This work is an attempt to select the optimum process parameters for friction stir welding of similar AA6061 aluminum alloy based on multiple criteria decision-making approach. The friction stir welding experiments have been conducted according to the orthogonal L9 array and the chosen input parameters are tool rotational speed, feed, and tilt angle. The responses measured are tensile strength, hardness, and % of elongation of welded joint. The multi-criteria decision-making technique namely multi-objective optimization based on the ratio analysis (MOORA) is used to find the optimum process parameters combination. The optimum conditions are tool rotational speed of 1120 rpm, feed of 30 mm/rev and tilt angle at 1 o.

Experimental Investigation of SPIF Process for Conical Frustum

In sheet metal industries, single point incremental forming (SPIF) is a popular technology for quick prototyping and small series manufacturing techniques. In producing specific components with complicated geometries, the technique has become known for its flexibility, effectiveness, and simplicity of usage. The objective of this research work is to carry out the numerical investigation of the SPIF process to study the effect of different parameters on the formability for truncated cone. Al 1060 grade of aluminium is used for this study which is commonly used for kitchenware, reflectors, electronic components etc; where strength is not a major concern. Three dimensional models were developed for different set of parameters using commercial finite element software ABAQUS 6.13 with Dynamic/Explicit solver using solid mechanics model. Taguchi analysis has been carried out to find the effect of parameters (Tool rotational speed, Feed, Step size, Tool diameter and Wall angle) on thickness reduction. Each parameter was varied for three levels and L9 orthogonal array was used. The ANOVA tool has been used to summarize the contribution of each variable. Results have been compared with reported experimental results for validation. The process modelling is concluded with a brief overview of approaches for improving part quality.

Through-Wire Microstrip-to-Empty-Substrate-Integrated-Waveguide Transition at Ka-Band

The advantages of the Substrate-Integrated Waveguide (SIW) in terms of low profile, integration with Printed Circuit Board (PCB) and low cost are maintained by the Empty Substrate-Integrated Waveguide (ESIW). Moreover, as the dielectric fill is avoided, other advantages are also added: resonators with higher quality factor and lower insertion losses. Since 2014, when it was proposed, several devices for X-band to Ka-band applications have been accurately designed and manufactured. In this way, transitions are one of the most important components, as they allow the connection between the ESIW and other planar transmision lines such as microstrip. To accomplish this aim, different transitions have been proposed in the literature: based on sharp dielectric tapers combining metallized and non-metallized parts, which increases the manufacture complexity; with a broadened ESIW section, that is less complex at the cost of increasing reflection and radiation losses due to the abrupt discontinuity; based on tapered artificial dielectric slab matrix, more difficult to mechanize; using a tapered microstrip transition, with high radiation losses; and even transitions for multilayer devices. Among all the transitions, the most versatile one is the through-wire transition, as microstrip and ESIW can be implemented in different layers and allows any feeding angle between the microstrip line and the ESIW. In this paper the through-wire transition has been properly validated at Ku- and Ka-bands. Moreover, a back-to-back transition has been accurately manufactured in Ka-band with measured insertion losses lower than 3.7 dB and return losses higher that 11.7 dB, concluding that the transition is not frequency dependent.

Optimization of drilling parameters in vertical machining centre drilling on magnesium AZ91D alloy under dry condition with Taguchi design

Drilling using a Vertical Machining Centre (VMC) remains a prevalent machining technique, even if current metal cutting processes have improved. Drilling settings on a VMC are optimized using the Taguchi technique to minimize surface roughness, hole diameter, and circularity error roundness test in this experimental investigation. In order to obtain the optimum process parameters in the VMC drilling on Magnesium AZ91D Alloys, L16 orthogonal arrays was formed by changing the four different speed, feed and end point angle. In the trials, an AZ91D alloy was employed and a variety of process factors, like drilling speed (250, 350, 450 and 550 rpm), feed rate 0.025, 0.05, 0.075 and 0.1 mm/rev), and end point angle (55, 75, 95 and 118°) were examined. Experimental results shows that a combination of slow speed (250 rpm), higher feed (0.1 mm/rev), and a medium end point angle (75°) resulted in the lowest roughness average value. It was possible to achieve the hole diameter accuracy by using the parameter at higher speed (450 rpm), higher feed (0.1 rev/min) and an end point angle of 118°. The lowest possible cylindricity error was perceived at 250 rpm speed, 0.01 mm/rev feed and 118° end point angle respectively. The lowest possible roundness error was perceived at 250 rpm speed, 0.05 mm/rev feed and 118° end point angle respectively. It was noticed from this experimental study and Taguchi technique, the surface roughness of the drilled hole is greatly affected by speed, feed and end point angle of the drill bit tool. Lower magnitude of drill tool speed and lower end point angles cause the good surface roughness values rather than the higher magnitude. The drilled hole’s diameter accuracy is significantly influenced by lower tool speed, higher feed rate and higher end point angle of the drill bit tool. The lower tool speed and higher end point angle of the drill bit tool are the two major factors, which are influenced the minimum cylindricity and roundness errors. It was observed from this experimental study, the lower drill bit tool speeds, higher tool feeds and higher end point angles are the important factors, which are significantly affected the quality of the drill holes during the machining of Magnesium AZ91D alloy in Vertical Machining Centre ((VMC) under dry conditions.

Wide Dual-Band Circularly Polarized Diecletric Resonator: Innovative Integration of a Single Hybrid Feed and Thin Grounded Metasurface.

This article presents an application of a grounded substrate-based metasurface for hosting dielectric resonators (DRs), enabling a wide dual-band circularly polarized (CP) operation. The antenna structure comprises centrally positioned rectangular DRs, one above the other, along with a 7 × 7 square-slotted metasurface. The metasurface and DRs are hosted above a grounded substrate, which is fed through a single coaxial feed placed at a specific angle, employing a modified upper probe of the coaxial feed. The proposed hybrid technique utilizes the combined benefits of the feed angle and a well-matched metasurface, resulting in performance improvement. Notably, a measured impedance bandwidth of 88.1% for |S11| is achieved within the frequency range of 4.0 GHz to 10.3 GHz. Furthermore, the antenna design exhibits two overlapping measured 3-dB axial ratio (AR) bandwidths: 23.62% from 4.25 GHz to 5.4 GHz and 5.12% from 7.6 GHz to 8 GHz. The peak gain of the antenna is measured at 8.4 dBic. Consequently, this innovative single-feed antenna design, characterized by its compact profile, holds significant potential for realizing multi-band operations. Furthermore, the developed antenna is well-suited for deployment in indoor radio links and INSAT applications.

Do it yourself: fabricating and evaluating a mosquito (Diptera: Culicidae) blood-feeding device to replace a commercial option.

Tools for rearing hematophagous insects, such as mosquitoes (Diptera: Culicidae), in an insectary are essential for research and operational evaluations in vector biology and control. There is an abundance of low-cost options for practitioners without conventional infrastructure. However, few midrange options exist that provide a balance of efficiency and low material waste. We present here a reproducible design for an electrically powered blood-feeding device that offers long-term reusability, low material waste, and customizability for different species or experiments. The limitation is the requirement for electricity, but the gain is a simple, low-skill device that can be modified as needed. To validate the design, assessments of feeding angle and blood-feeding success were compared between the Salt Lake City Mosquito Abatement District artificial membrane feeder (SLAM) and a commercial system (Hemotek). Engorgement in Aedes aegypti (80-90%), Culex pipiens (50-80%), and Culex tarsalis (30-75%) was similar between the 2 units, resulting in nearly identical fecundity outcomes between devices. Additionally, 45° angles were more successful, generally, than presenting the feeders flat or vertical to the mosquitoes (df3,48, P = 1.014 × 10-15). This angle is simple to present with the SLAM device. Materials for in-house reproduction of the SLAM system are now widely available in regions with access to e-commerce and shipped goods. This results in a device schematic that should fit well into a relatively modular, do-it-yourself paradigm where the practitioner needs only to assemble some materials without complex engineering. This article provides schematics, cost comparison, and validation of the in-house-made SLAM system.

A novel heterogeneous multi-wire indirect arc directed energy deposition for in-situ synthesis Al-Zn-Mg-Cu alloy: Process, microstructure and mechanical properties

Aiming to decouple the inherent relationship between mass transfer and heat transfer in traditional arc-based directed energy deposition, a novel heterogeneous multi-wire indirect arc directed energy deposition (DED) has been developed for in-situ synthesis of Al-Zn-Mg-Cu alloy components. Multi-wires (Al-Cu and Al-Mg) with a bypassing Zn wire have been used to replace the traditional homogeneous twin-wires. The process, microstructure and mechanical properties of the deposited Al-Zn-Mg-Cu alloy components obtained by multi-wire indirect arc DED were investigated. The results indicate that the wire feeding speed, current and angle between the two wires have a significant influence on the multi-wire indirect arc DED process. When the current was 200 A, the different wire feeding speeds could be used for both wires and the angle between them was 90°. The resulting indirect arc presented a ‘heart’ shape and allowed to obtain an Al-5.7Zn-3.4Mg-1.6Cu (wt%) alloy with a high deposition rate of 5.1 kg/h. The Al-5.7Zn-3.4Mg-1.6Cu alloy is mainly composed of α-Al, S (Al2CuMg), η (Mg (Al, Zn, Cu)2) and η′ phases. The composition and phases are in accordance with the 7xxx series aluminum alloys. The microstructure is dominated by columnar and equiaxed grains, and it has obvious periodic distribution along the building direction, which is related to the process thermal cycle. Fine second phases η′ are observed to precipitate during the manufacturing process. Furthermore, the average hardness, ultimate tensile strength and elongation of the fabricated material are 98.6 HV, 243.9 MPa and 5.9%, respectively. These mechanical properties are higher than those of as-cast 7050 aluminum alloy, thus showing the potential of this new process variant to fabricate high strength Al alloys in the as-deposited state. The fracture morphology exhibit features mainly associated to a ductile-like fracture, accompanied by some transgranular and partial cleavage fracture characteristics. This novel multi-wire indirect arc DED provides a new choice for arc-based directed energy deposition of Al-Zn-Mg-Cu alloys and shows great potential for the in-situ synthesis of other high-performance alloys.

Calculation of Parameters of Prism Deflector for Laser Scanner

The prism deflector which is a multifaceted prism with reflective facets is the most common scanning element that allows to quickly fill a wide scanning area with laser radiation pulses along one coordinate. The parameters of a prismatic deflector are related to the characteristics of the laser radiation of the scanned area parameters and of the deflector position, and are also limited by various factors, such as safety requirements or scanning time. The aim of this work was to analyze the relationship between the external operating conditions of a laser scanning system and the internal design parameters of a prism deflector.A variant of calculating of laser pulses frequency by the number of spots and their overlap coefficient is considered. A method for calculating of a prism deflector characteristics based on external parameters, such as the angle of incidence of radiation to the facet and the width of the Gaussian beam with dimensions that are safe for а human eye is proposed. Рrismatic deflectors parameters are proposed depending on the number of reflecting facets. Dependence of a deflector size on the angle of radiation incidence to the reflecting face is shown.When designing a prismatic deflector of a laser scanner used to fill a certain scanning area with the required angular size σ by varying such parameters as the number of faces m and the feed angle α it is possible to achieve optimal deflector characteristics and scanning mode for the task.

Multi-response optimization of process parameters during friction stir welding of AA2014-AA7075 using TOPSIS Approach

In this study, multi-objective optimization for Friction stir welding of dissimilar AA2014-AA7075 has been presented to provide optimum tensile strength, hardness, and % of elongation. The input parameters considered for the analysis are tool rotational speed, feed, and tilt angle. Experiments are designed based on Taguchi L9 orthogonal array. Investigative analysis on the effect of input parameters on the responses is carried out using the MINITAB14 software package. The parametric influence on responses is discussed through the main effects plot. Further, multi-objective optimization is performed with the Technique for order of preference by similarity to ideal solution (TOPSIS). Results demonstrated that tool rotational speed is the most significant factor affecting the response followed by feed and tilt angle. The optimum cutting parameters obtained are tool rotational speed 710 rpm, Feed 30 mm/rev, and Tilt angle 2o.

Evolutionary modifications of Astyanax larval prey capture (LPC) in a dark environment.

Feeding strategies of an organism depend on the multimodal sensory processing that most efficiently integrates available visual, chemosensory, and/or mechanoreceptive cues as part of their environmental adaptation. The blind cavefish morph of Astyanax mexicanus has developed sensory-dependent behaviors to find food more efficiently than their eyed, surface-morph counterparts while in darkness. In the absence of light, adult cavefish have evolved enhanced behaviors, such as vibration attraction behavior (VAB), and changes in feeding angle. Here, we identified evolved differences in cavefish larval prey capture (LPC) behavior. In the dark, LPC is more efficient in cavefish than in surface fish. Furthermore, different cave populations express laterality in their LPC and strike towards prey preferentially located on their left or right sides. This suggests the occurrence, to some extent, of divergent LPC evolution among cave populations. While LPC can be triggered exclusively by a vibration stimulus in both surface and cavefish, we provide evidence that LPC is, at least partially, a multimodal sensory process different from adult VAB. We also found that a lack of food may exacerbate the laterality of LPC. Thus, we proposed a mathematical model for explaining laterality based on a balance between: (1) enlarged range of foraging field (behavioral or perceptive) due to asymmetry, (2) food abundance, and (3) disadvantages caused by laterality (unequal lateral hydrodynamic resistance when swimming, allocation of resources for the brain and receptors, and predator escape).

Optimization of Drilling Parameters in Sisal-Human Hair Hybrid Composite Using Grey Relational Analysis

Sisal is the most commonly used natural fiber in polymer composites due to its high strength, durability, and ability to stretch. In this present work, sisal and human hair were used as reinforcement for epoxy resin-based hybrid composites, and their effect on the mechanical properties was reported. Four composite plates with fiber volume fractions of 10%, 20%, 30%, and 40% were fabricated by the hand lay-up method. Chopped sisal fiber and human hair of 30 mm length were mixed with epoxy resin to fabricate the composites. In addition, high-speed steel (HSS) drills were used to study the influence of drilling parameters such as speed, feed, and drill point angle on the quality of the drilling. Three factors with three levels were considered for the design of the experiment. The drilling parameters were optimized using Grey Relational Analysis and the Taguchi method for the reduction of delamination. The experimental results indicate that a flexural strength of 38 MPa was achieved in a 60% epoxy, 20% sisal, and 20% human hair composite. NI vision assistant software was used to process the images taken on the drilled holes using the Matrix Vision camera. The optimization results showed that the feed rate played a pivotal role in deciding the delamination on the entry side of the hole. In contrast, the drill point angle significantly affects the delamination at the exit side of the hole. Better quality holes are achieved with a cutting speed of 2500 rpm and a feed rate of 50 m/min.

Effect of process parameters on forming quality of hollow axle blank with rotary piercing

At present, hollow axles are mostly manufactured by precision forging and then deep processing, which has long technological process and high cost. In order to realize the integrated forming of hollow axles with short process and low cost piercing and skew rolling, a method of piercing billet by two-roll skew rolling is proposed in this paper, and the finite element model of the forming process is established by using SimufactForming software. The effects of roll feed angle, roll speed and plug advance on the wall thickness uniformity of piercing tube billet are explored, and the process parameters with the best wall thickness uniformity are obtained. It lays a technical foundation for the blank guarantee and the realization of the integrated forming process of hollow axle.

Analysis of Temperature Influence on Strain-Speed Parameters of Radial-Shear Rolling of Al-Zn-Mg-Ni-Fe Alloy.

The comprehensive analysis of temperature influence on the strain–speed parameters of radial-shear rolling of Al-Zn-Mg-Ni-Fe alloy including the investigation of rheological properties, FEM simulation, and in-depth analytical interpretation of results was carried out. The rolling temperature has significant effect on the kinematic of metal forming, speed parameters, configuration, and length of trajectories. With the decrease in temperature, the speed of metal movement reduces, and this is the same for different components. The greatest decrease is noted for the axial speed component. In general, according to the nature of effect on the strain kinematic state, a temperature reduction of 100 °C (from 500 to 400 °C) acts similarly to a decrease in feed angle of about 4° and, in particular, increases the rolling time, nonuniformity of deformation, tightening, and temperature effect of deformation heating.