Roller Geometry Research Articles

Roughness optimization of flow-formed tubes using the Taguchi method

The present study reports the effect of various flow-forming process parameters and roller geometry on the roughness of flow-formed tubes of commercial pure copper UNS C11000. Thickness reduction ratio, feed rate, angular speed of mandrel, attack angle of roller, roller tip radius, and smooth angle of roller were considered as variable parameters. The effects of these input parameters on the roughness have been critically analyzed using the Taguchi method. Through ANOVA analysis, it has been found that the roller tip radius is the most important parameter affecting roughness followed by thickness reduction ratio. Selection of an optimum combination of variable parameters was performed based on “average of results.” The minimum roughness of 1.37 μm was achieved when the process parameters were set at their optimum values.

Thermal modelling of the laser-assisted thermoplastic tape placement process

Thermoplastic tape placement opens the possibility of a fully automated composite production. The resulting quality is highly dependent on the thermal history during consolidation. This article focuses on the thermal modelling of a tape placement system employing a near-infrared laser. A nonlinear two-dimensional finite element model is presented for a carbon fibre reinforced thermoplastic (AS4/PEEK) composite placement process using a conformable roller. The relative influence of roller geometry, roller temperature and thermal contact resistance was studied. Temperature measurements were performed using thermocouples welded to the substrate. The model predictions show good correlation in terms of timing of the irradiation, shadow and consolidation regions. The roller temperature was found to have the most significant impact on the bond line temperature distribution.

Modeling of contact theories for the manipulation of biological micro/nanoparticles in the form of circular crowned rollers based on the atomic force microscope

This article has dealt with the development and modeling of various contact theories for biological nanoparticles shaped as cylinders and circular crowned rollers for application in the manipulation of different biological micro/nanoparticles based on Atomic Force Microscope. First, the effective contact forces were simulated, and their impact on contact mechanics simulation was investigated. In the next step, the Hertz contact model was simulated and compared for gold and DNA nanoparticles with the three types of spherical, cylindrical, and circular crowned roller type contact geometries. Then by reducing the length of the cylindrical section in the circular crowned roller geometry, the geometry of the body was made to approach that of a sphere, and the results were compared for DNA nanoparticles. To anticipatory validate the developed theories, the results of the cylindrical and the circular crowned roller contacts were compared with the results of the existing spherical contact simulations. Following the development of these contact models for the manipulation of various biological micro/nanoparticles, the cylindrical and the circular crowned roller type contact theories were modeled based on the theories of Lundberg, Dowson, Nikpur, Heoprich, and Hertz for the manipulation of biological micro/nanoparticles. Then, for a more accurate validation, the results obtained from the simulations were compared with those obtained by the finite element method and with the experimental results available in previous articles. The previous research works on the simulation of nanomanipulation have mainly investigated the contact theories used in the manipulation of spherical micro/nanoparticles. However since in real biomanipulation situations, biological micro/nanoparticles of more complex shapes need to be displaced in biological environments, this article therefore has modeled and compared, for the first time, different contact theories for use in the biomanipulation of cylindrical and circular crowned roller shaped micro/nanoparticles. The results of models indicate that the contact model of Hertz achieves the largest amount of deformation for the DNA nanoparticle in cylindrical form and the contact model of Heoprich achieves the largest deformation for the circular crowned roller shaped DNA. Of course, this finding is not always true for the other nanoparticles; and considering the mechanical and environmental characteristics, different results can be obtained. Also, by comparing the deformations of different types of nanoparticles, it was determined that the platelet type nanoparticles display the highest degree of deformation in all the considered models, due to their particular mechanical characteristics.

High pressure rolling of low carbon steel weld seams: Part 2 – Roller geometry and residual stress

Large residual stresses are an undesirable but inevitable side effect of fusion welding operations, and localised high pressure rolling of the weld seam is a proposed method for eliminating them. In this study, neutron diffraction has been used to map the residual stresses within low carbon steel weld seams treated with high pressure rolling. The effect on the residual stress distribution of using different roller types was determined, along with the influence of these different rollers on final weld seam geometry. Rolling was found to completely change the residual stress state in the weld, creating large compressive longitudinal residual stresses. It was effective for this purpose regardless of whether it was applied directly to the weld seam or to regions either side of it. The fatigue life of welded specimens was shown to be reduced by rolling; however, it is suggested that this is due to geometric and metallurgical effects.

DETERMINATION OF THE NIP ZONE ANGLE IN HIGH-PRESSURE GRINDING ROLLS

A proposal of the nip zone angle determination in high-pressure grinding rolls (HPGR) crush- ing process is presented in the paper. Knowledge of the nip zone angle value makes it possible to deter- mine the real maximum pressing force in the high-pressure comminution. Two methods of determination of this maximum pressure were proposed and verified. The first method is based on the roll's geometry and the change of the HPGR chamber's volume together with the roll rotation, while the second one considers the outlet gap width. Results of the nip zone angle calculations according to both methods are similar and show that the nip zone angle is around 3 o . The verification was carried out in a piston-die press and experimental results show that the product size distributions from HPGR and piston-die press are similar. The methodology of the nip zone angle determination presented in the paper has then its practical confirmation. A proper determination of the nip zone border makes it possible to calculate the comminution probability of given type of material and is a basis for the HPGR crushing process modeling and optimization.

Prediction of surface roughness due to spinning in the incremental tube forming process

Incremental tube forming (ITF) is a new process allowing a flexible manufacturing of 2D and 3D bent tubes with load-optimized cross sections by means of the combination of the procedures spinning and bending. The aim of this paper is to acquire an in-depth process understanding concerning the surface roughness. This paper focuses on the spinning process operation of the ITF process. The influence of the spinning roll geometry and the process parameters on the theoretical surface roughness is studied in detail. Crest height h and roughness average parameter Ra are formulated as function of process parameters and spinning roll geometry. Also, a fishbone diagram with the parameters influencing the tube surface characteristics is provided. Experiments are performed to quantify the divergences of the equations. The theoretical approach can be used to understand the incremental tube forming process in more detail.

A new laboratory test for the estimation of wear in high pressure grinding rolls

As 75 up to 85% of the exhausted energy in mining and mineral processing industries is used for comminution processes, more energy efficient crushing technologies such as high pressure grinding rolls (HPGR) can help to reduce the consumption. Differing chemical compositions and physical properties of minerals due to origin and pre-treatment aggravate a wear prediction of the roller material, a key indicator for cost efficiency. To determine the wear characteristic of different minerals with respect to the complex wear system, consisting of abrasive wear (scratching) and surface fatigue (indentation), a laboratory scale apparatus is put into operation.The main wear influencing variables are roll speed, geometry and composition, grinding pressure and characteristics of the feedstock. Scaling up gained data on industrial processes assumes fundamental understanding of the coherences between these variables. Therefore, the influence on wear behavior of three selected parameters, grinding pressure, grain size and moisture of the feedstock are presented in this paper. The tests are carried out with rolls made of the martensitic hardened steel AISI L6 with a diameter of 100mm. The feedstock consists of silica sand (Bottrop, Germany) with grain sizes ranging from 0.2mm to 2mm to meet all demands concerning comminution in a confined material bed. Accompanying to the tests, traces of wear on the roll surface are examined with a scanning electron microscope (SEM).The tests add up to an increase in wear rate, i.e., volume loss per 1000 revs, as a result of increasing grinding pressure, an increase of the maximum feedstock grain size and an increase of feedstock moisture. Assumed wear mechanisms could be verified.The results provide for a better understanding of the complex wear system of HPGRs. More precise wear estimations of varying minerals is part of the ongoing work.

A dimensional analysis of front-end bending in plate rolling applications

Rolling under asymmetrical conditions such as temperature gradients within the material, difference of the circumferential velocity of the rolls and different friction coefficients cause the rolled slab to bend towards the direction of one of the rolls. This mechanical phenomenon is referred to as ski effect. In general this effect is undesired, since it hinders the further material transport and is a potential danger for the machine components in the proceeding processes. De facto it is possible to exert control on the ski effect in terms of selected peripheral speeds of the rolls. Unfortunately the essential mechanisms and the sensitivity of the influencing parameters in asymmetric rolling are still not comprehended sufficiently.In this contribution a mathematical description of the ski effect is provided, embedding this process into a finite element framework of plasticity in the context of large deformations. In order to qualify the impact of specific process parameters a corresponding dimensional analysis is performed. The introduced dimensionless quantities give rise to a complete parametric study of the process under consideration. Both the ratio of the circumferential velocity of the rolls and the difference of the friction coefficients as a cause for ski effect are exposed and their influence as well as their interdependency subjected to different roll geometries are studied.

Lifetime Determination of the Raceway of a Large Three-Row Roller Slewing Bearing

This paper deals with calculation procedure for lifetime determination of a large three-row roller slewing bearing. First, the contact force distribution between the rollers and the bearing raceway is determined both analytically and numerically. Then, the position and the magnitude of the maximum contact force are identified. In a separate numerical model finite element analyses are performed to determine the subsurface stress distribution as the result of contact between the raceway and different rollers. These stress fields serve as an input for the fatigue lifetime calculation, which is done in accordance with the stress-life approach (S-N). At the end the influence of roller geometry on the calculated fatigue life is presented.

Modern sheet-glass cutting technologies

The main types of sheet-glass cutting are examined. Mechanical roller cutting, being the most widely used cutting method at the present, is described in greatest detail. The effect of the roller geometry and load on the edge quality is explained. A general description of the hydro-abrasive and laser cutting technologies is also presented. The advantages and disadvantages of the existing technologies are indicated.

S162023 特殊形状を有したローラによるウェブ拡張メカニズムの実験的検証([S16202]柔軟媒体ハンドリングと画像形成システム(2))

A web is thin and flexible materials such as paper, optical film, metallic lamina etc. In recent years, the web is expected fusion with printed electronics. The web is produced by Roll to Roll producing system with high productivity. However, when web defects are occurred in the producing processes, the web defects result in waning productivity. It is known that the web defects can be prevented using specially shaped rollers. Among them, a concaved roller which has large edge diameter compared with center diameter can be made by easy process. Therefore, most of engineers empirically use concave roller. However, when engineers mistake roller geometry and use, web defects might be caused oppositely. Therefore, to understand the preventing mechanism and effect is very important for web handling engineers. This paper describes the spreading mechanism and effect by concaved roller. The spreading effect of concaved roller is measured by slit separation of web. As a result, concaved rollers were confirmed that these separated web. Consequently, concaved rollers showed that there was an effect of web spreading. In addition concaved roller with micro-groove showed slit separation of web under low tension.

Load capacity of a three-row roller slewing bearing raceway

A calculation model for fatigue lifetime determination of a three-row roller slewing bearing raceway is presented. First, the contact force distribution between the roller and the raceway is analytically determined from the basic bearing geometry and the external loads acting on the bearing assembly. Then a numerical model is employed to calculate subsurface stress distribution in the raceway as a result of the contact force between the roller and the raceway. Numerically calculated subsurface stress field serves as an input for the fatigue calculation of the raceway, which is done according to the stress-life approach. Two different types of rollers are investigated: plain cylindrical roller and a profiled roller. Finally, the influence of the roller geometry on the fatigue life is pointed out.

Design of Synchronous Processes of Rolling-Leveling and Ultrasonic Electrochemical Finishing of Holes

A new finishing method of holes that uses an effective electrode and a nonconductive roller to execute the design of synchronous processes of ultrasonic electrochemical finishing and rolling-leveling is investigated. The submitted processes can be used among the traditional techniques of various holes machining. Through simple equipment attachment, ultrasonic electrochemical finishing and rolling-leveling can follow to execute the finishing process on the same machine. Among the factors affecting finishing processes, the performance of rolling-leveling combined with ultrasonic electrochemical finishing is primarily discussed. In the experiment, the electrode is used with continuous and pulsed direct current. The controlled factors include roller material, roller geometry, chemical composition and concentration of the electrolyte, and flow rate of electrolytes. The experimental parameters are frequency and power level of ultrasonics, feed rate of electrode and roller, rotational speed of the finish-tool, die material, electrical current rating, and pulsed period. The design of the synchronous processes through rolling-leveling is the most influential parameter in this study. An adequate finish-tool rotational speed produces better finishing. The average effect of the ultrasonic is better than the pulsed current while the machining time needs not to be prolonged by the off-time. An effective and low-cost finishing process through the ultrasonic electrochemical finishing and using the rolling-leveling assistance after the process of traditional holes machining make the surface of the holes smooth and bright is presented.

Grain orientation dependence of extended planar dislocation boundaries in rolled aluminium

The dislocation boundary alignment in 124 grains in cold-rolled aluminium has been investigated by a combination of backscattered electron channelling contrast and electron backscatter diffraction . The asymmetric slip geometry of the Copper and S orientations together with the existence of different symmetry variants of these orientations is exploited to analyse whether the grain orientation (and consequently the slip systems) or the symmetric rolling geometry determines the boundary alignment. The results unambiguously point at the grain orientation as the controlling factor.

Effect of roller nose radius and release angle on the forming quality of a hot-spinning process using a non-linear finite element shell analysis

This research presents a non-linear dynamic finite element (FE) analysis of a tube-spinning process based on the Belytschko—Lin—Tsay shell element with an explicit time integration scheme. A brief description of the FE formulation of a first-order shear deformation shell element as well as plane stress elastoplastic analysis, internal forces calculation, nodal mass calculation, and prediction of stable time step are presented. An explicit FE code is designed and its implementation algorithm is described in detail. The optimum geometry of a roller is attained using the FE simulations of a hot-spinning process with various roller geometries. The dome-forming process of a seamless pressure vessel using modified roller geometry is performed to confirm the successful process predicted by FE simulation. The vessel is cut longitudinally and its profile is measured. A comparison between longitudinal cross-section profiles calculated by the FE analysis and that obtained from the experiment shows a good agreement.

Automating the Design of Cold Roll Forming Roll Sets

The design of cold roll forming roll tools, roll geometry and the number of tool sets, can typically be referred to as experiential design. Within a multi-occupant design office there will normally, for the same sectional profile, be as many different designs as there are designers. This variation in design results in a lack of design consistency and hence makes the process of developing design understanding, increasing profile complexity, maintaining quality, and roll tool predictability very difficult. This paper contains an explanation of the approach taken within the Hadley Group to identify the discrete steps associated with roll tool set design. To implement methods to standardise these steps including strip width and clearance calculations. With appropriate design steps standardised an explanation is provided as to how elements of this design process is automated leading to a system of assisted design for roll tool sets. The results, including increased design capacity, of the assisted roll design after being incorporated into the design office are discussed.

Reducing thickness variation of hot rolled steel strip by non-circular back-up roll geometry

Typically, back-up rolls in hot strip mills are equipped with sliding bearings and it is common to use a key that prevents relative motion between the conical sleeve and the roll shaft. The key groove causes deformation of the sleeve under load. This sleeve 'spring' is observed as rolling force variation, which causes systematic thickness variation of the steel strip. Although there is a keyless bearing construction on the market, an alternative solution was studied. A non-circular camlike geometry that compensates the sleeve spring was ground on the back-up rolls by a three-dimensional grinding method. As a result, ∼50% of the rolling force and the thickness variations, which were synchronised with the back-up rolls of the mill stand studied in the present paper, were reduced.

Rolling of mozzarella cheese: Experiments and simulations

Mozzarella cheese is a visco-elastic-plastic shear-thinning material with a yield stress, which in a shear flow may be approximated by the Herschel–Bulkley model. The material was rolled in the SER extensional rheometer used as a rolling device with an aspect ratio of radius to minimum gap R/ H 0 = 4.3. For different feed thickness ratios and roll speeds, the exit thickness ratios and torques were measured and found to increase substantially with roll speed and initial sample thickness. Two-dimensional finite element simulations based on the rolling geometry and the rheological data provide yielded/unyielded zones, pressure, and stress distributions along the rolls. The results from the simulations are in good agreement with the experimental torque values but underestimate (by an order of magnitude) the thickness of the exiting sheets. It is argued that the latter is due to strong viscoelastic effects, which manifest themselves in free-surface flows, where (extrudate) swell becomes significant.

Rolling of bread dough: Experiments and simulations

Bread dough (a flour–water system) has been rheologically characterized using shear rheometry at room temperature. Its flow curve shows a viscoplastic shear-thinning material, which obeys the Herschel–Bulkley model. In addition, substantial wall slip is exhibited by the material, and an appropriate slip law has been formulated. The material has been rolled using the Sentmanat Extensional Rheometer (SER) (Xpansion Instruments) with an aspect ratio of radius to minimum gap of R/ H 0 = 4.3. Rolling experiments have been performed for different feed thickness ratios and roll speeds. The exit thickness ratios and the torques to roll the samples have been measured. They have been found to increase substantially with roll speed and initial sample thickness. Two-dimensional finite-element simulations based on the rolling geometry and the rheological data with slip provide a wealth of information regarding yielded/unyielded zones, pressure and stress distributions along the rolls. The results from the simulations are in good agreement with the experimental torque values although underestimate the thickness of the exiting sheets. It is argued that the latter is a consequence of viscoelasticity of the bread dough, which manifests itself in a free-surface flow, where (extrudate) swell becomes significant.

Stochastic inflation revisited: non-slow-roll statistics and DBI inflation

Stochastic inflation describes the global structure of the inflationary universe bymodeling the super-Hubble dynamics as a system of matter fields coupled togravity where the sub-Hubble field fluctuations induce a stochastic force into theequations of motion. The super-Hubble dynamics are ultralocal, allowing us toneglect spatial derivatives and treat each Hubble patch as a separate universe. Thisprovides a natural framework in which to discuss probabilities on the space ofsolutions and initial conditions. In this paper we derive an evolution equationfor this probability for an arbitrary class of matter systems, including DBI andk-inflationary models, and discover equilibrium solutions that satisfy detailedbalance. Our results are more general than those derived assuming slow roll or aquasi-de Sitter geometry, and so are directly applicable to models that do notsatisfy the usual slow-roll conditions. We discuss in general terms the conditionsfor eternal inflation to set in, and we give explicit numerical solutions of highlystochastic, quasi-stationary trajectories in the relativistic DBI regime. Finally, weshow that the probability for stochastic/thermal tunneling can be significantlyenhanced relative to the Hawking–Moss instanton result due to relativistic DBIeffects.