Shape Rolling Research Articles

The shape analysis of three-dimensional flexible rolling method

A new forming method, three-dimensional flexible rolling, is proposed for three-dimensional surface parts, which can form the parts effectively with the dieless characteristics. In this study, the shape of bending rolls is circle and the bending radii of upper and lower rolls are different; therefore, the roll gap is non-uniform. Because of the roll gap, an uneven compression appears at the transversal direction, which leads to a non-uniform elongation in feeding direction. The parts bend in two directions at the same time, and the three-dimensional surface shape is obtained. The forming rules of flexible rolling are proposed to analyze the relationship between the pressure ratio and the deformation extent of double-curved surface. The function between the non-uniform roll gap and the bending radius is deduced from the theory of invariable volume. An experimental device is developed to do the forming experiments. The feasibility of the device and the advantage of the method have been validated through numbers of experiments. Typical three-dimensional surface parts such as the convex and saddle parts have been completed for researching and analyzing. Some fine numerical simulation results of flexible rolling have been obtained. Finally, the simulation results are compared with the actual results to analyze the shape and illustrate the forming effect.

Design of roll profile for complex shape in shape rolling by combined 3D-EFA and BWT

A design method using three-dimensional electric field analysis (3D-EFA) and a backward tracing scheme (BWT) is proposed to improve the dimensional accuracy for a complex shaped product in shape rolling. A complex door hinge used in the door hinge of automobile is taken as a case study. A shape rolling process for this hinge is designed using the proposed method, and a backward tracing scheme is then applied to find a more suitable roll profile. 3D-EFA is carried out for this purpose, and the roll profiles at each pass are selected based on the 3D-EFA results using the reduction ratio in the area per pass. In addition, a BWT is applied to the selected roll profile in order to achieve the dimensions of the required product. The effectiveness of the proposed design method is verified via FE-simulation and experimentation using plasticine. The results of FE-simulation and experiment show that the proposed design method can be used to effectively design the roll profile for the complex door hinge, leading to an accurate shape and correct dimensions of the final within an allowable tolerance of ±0.5 mm. Therefore, it can be concluded that the proposed design method can be widely used to design roll profiles for producing a precise product.

Finite Element Modeling of Strain Distribution through Sheet Thickness during Cold Rolling with Grooved Rolls

Plastic strain control of aluminum alloys are of importance for improvement of sheet microstructure and properties. The paper presents a numerical analysis of the strain distribution through pure Al sheet thickness during cold rolling with flat and grooved rolls. FEM simulations were carried out with using software DEFORM 3D. For verification of the numeric modeling results, the experimental analysis was carried out. The influence of the roll shape on strain distribution through Al sheet thickness was studied. It was shown that the strain effective increases from 0.9 to 1.5 during cold rolling with grooved rolls, when depth of indentation of grooved rolls in sheet increases from 0.25 to 0.50 mm. FE model can be used to optimize the cold rolling process to improve microstructure and mechanical properties of aluminum sheets.

Frontal cellular automata simulations of microstructure evolution during shape rolling

The use of numerical modelling allows us to shorten the time for development of new technologies and to optimise the existing ones in view of final material properties. The paper presents the modelling of shape rolling of 5 mm round bars in diamond and oval grooves. Modelling scheme consists of three stages. The first stage is a development of rolling schedule, which is based on finite-element method simulations. The schedule design begins from the last pass. The paper presents the schedule developed for the last six passes. Then, in the second stage, finite-element method simulations were fulfilled in the proper rolling sequence. The aim of this stage is obtaining the thermomechanical parameters of the process. These parameters are transferred to frontal cellular automata model that takes into account the deformation and simulates microstructure evolution. Some results of finite-element method and frontal cellular automata modelling are presented in this paper.

유연한 CNT Nanosheet 기판을 이용한 생체연료전지 Roll 제작

The most promising application of the biofuel cells is implantable devices, so the biofuel cells should have an appropriate shape for the vascular vessel. We demonstrated the biofuel cell roll for using in tubes. MWNTs were aggregated by vacuum filtration on a nitrocellulose membrane filter, which was biocompatible and flexible. The MWNT aggregated nitrocellulose membrane used the electrodes of the biofuel cells because it was conductive as well as nanostuructured. Then, the membrane was rolled into the roll shape. The maximum power density of the biofuel cell roll was 7.9 μW/cm2 at 153mV and 50 mM glucose. Also, the power density is expected to increase in its practical application if there is flow in the tube, which makes the transportation of fuel easy. The biofuel cell roll contacts with the wall of the tube, so flow in the tube does not disturb. Also, the biofuel cell roll has multi-layers offering more electroactive area.

Prediction of microstructure evolution during multi-stand shape rolling of nickel-base superalloys

AbstractIn this paper, a comprehensive numerical approach to predict the microstructure of nickel-base superalloys during multi-stand shape rolling is presented. This approach takes into account the severe deformation that occurs during each pass and also the possible reheating between passes. In predicting the grain size at the end of the rolling process, microstructural events such as dynamic recrystallization (DRX), metadynamic recrystallization (MDRX), and static grain growth are captured at every deformation step for superalloys. Empirical relationships between the average grain size from various microstructural processes and the macroscopic variables such as temperature (T) and effective strain ( ε ̄ ) and strain rate ( ε ̄ ̇ ) form the basis for the current work. These empirical relationships are based on Avrami equations. The macroscopic variables are calculated using a finite element analysis package wherein the material being rolled is modeled as a non-Newtonian fluid with viscosity that depends on the effective strain rate, strain, and temperature. A two-dimensional transient thermal analysis is carried out between passes that can capture the MDRX and/or static grain growth during the microstructural evolution. The presented microstructure prediction algorithm continuously updates two families of grains, namely, the recrystallized family and strained family at the start of deformation in any given pass. In addition, the algorithm calculates various subgroups within these two families at every deformation step within a pass. As the material undergoes deformation between the rolls, recrystallization equations are invoked depending on critical strain and strain rate conditions that are characteristics of superalloys. This approach predicts the microstructural evolution based on recrystallization kinetics and static grain growth only. The methodology was successfully applied to predict the microstructure evolution during the multi-pass rolling of nickel-base superalloys. The predicted results for Alloy 718 for a 4-stand rolling followed by air cooling and for a 16-stand rolling followed by a combination of air and water cooling are also compared with experimental observations.

심리스 파이프 제조를 위한 일롱게이션 공정의 유한요소해석

Elongation rolling process is an intermediate process to make the uniform thickness and uniform surface roughness during producing seamless pipes. The thickness and surface roughness of seamless pipes are generally affected by the distance of rolls and guide shoes, the roll shape, and its cross angle. In this study, finite element analysis for shape forming process is based on the analysis model of elongation rolling mill with guide shoes. This paper shows how the cross angle of the roll, the rolling rpm, and the distance of the guide shoe influence on the outer diameter and the thickness of seamless pipes. The rolling rpm did not give much influence on outer diameter.

Multiscale Model of Shape Rolling Taking into Account the Microstructure Evolution – Finite Element Modeling

The use of appropriate forming processes allows to obtain materials of required quality, which are fulfill different technological criteria. The basic type of properties, which are fundamental for material use in specific operating conditions, are mechanical ones. They directly depend on the microstructure. Model of microstructure evolution allows for multi-criteria optimization of technological processes in view of final product properties, taking into account technological conditions. The objective of this study is development a multiscale model of microstructure evolution during the shape rolling process and presentation the finite element modeling results for 5 mm round bars rolled in diamond, oval and round grooves. The model allows to obtain parameters of technological process (by means of finite element model - FEM) and microstructural parameters (with use cellular automata - CA). FEM is used for design and selection of the grooves on the first stage [1] and for the simulations of shape rolling process in macro scale on the second stage. The next stage includes the use of FEM modeling results for simulation of microstructure evolution by cellular automata. The article presents the simulation results of shape rolling (5 mm round bars in diamond - oval scheme) with used the finite element method. This stage is the second one in the calculation sequence of the developed multiscale model. The basic process parameters such as temperature, components of strain and strain rate tensors and strain rate intensity at arbitrary points of deformed material are the modeling results. Selected FEM simulation results are presented in the article.

Nudging children towards whole wheat bread: a field experiment on the influence of fun bread roll shape on breakfast consumption.

BackgroundMany children do not eat enough whole grains, which may have negative health consequences. Intervention research is increasingly focusing on nudging as a way to influence food choices by affecting unconscious behavioural processes. The aim of this field study was to examine whether the shape of bread rolls is able to shift children’s bread choices from white to whole wheat during breakfast to increase whole grain intake.MethodsIn a between-subjects experiment conducted at twelve primary schools in the Netherlands, with school as the unit of condition assignment, children were exposed to an assortment of white and whole wheat bread rolls, both varying in shape (regular versus fun). Children were free to choose the type and number of bread rolls and toppings to eat during breakfast. Consumption of bread rolls was measured at class level via the number of bread rolls before and after breakfast. In addition, children (N = 1113) responded to a survey including questions about the breakfast.ResultsResults of the field experiment showed that about 76% of bread consumption consisted of white bread rolls. Consumption of white bread rolls did not differ according to shape (all P-values > 0.18). However, presenting fun-shaped whole wheat bread rolls almost doubled consumption of whole wheat bread (P = 0.001), particularly when the simultaneously presented white bread rolls had a regular shape (interaction P = 0.02). Survey results suggest that slight increases in perceived pleasure and taste are associated with these effects.ConclusionsOverall, presenting whole wheat bread in fun shapes may be helpful in increasing consumption of whole wheat bread in children. Future research could examine how improving the visual appeal of healthy foods may lead to sustained behaviour changes.

Development of Finite Element Analysis Model for Plug Mill Rolling

In the seamless pipe rolling process, the pipe wall thickness is largely determined at the mandrel mill or plug mill. It is possible to obtain the target thickness at these mills by defining the gap of a grooved roll and an inside tool such as a plug. However, the thickness of the free deformation part, which is not in contact with the roll and tool, had generally been estimated by experimental techniques. Although a number of analytical studies of mandrel mill rolling had been reported, few reports had examined plug mill rolling. Therefore, in this research, a finite element analysis model for plug mill rolling was developed by extending the rigid plasticity finite element model "Computational Rolling Mill (CORMILL)." Good agreement between the calculated results and experimental results was obtained for the wall thickness, and it was found that the thickness of the flange part decreases with reduction of the wall thickness at the grooved bottom. These results suggested that the wall thickness distribution of rolled pipes can be controlled by using a suitable inside tool and roll shape in each rolling pass, and the necessary shapes can be obtained by using the newly-developed model.

Multiscale Model of Shape Rolling Taking into Account the Microstructure Evolution – Frontal Cellular Automata

Properties of traditional materials including steels can be improved by using the prediction and control of microstructure evolution in technological processes. Models of microstructure evolution, which take into account the technological conditions, allow to optimize the process in view of final product properties. A multiscale model of microstructure evolution have been developed and adopted for simulation of the shape rolling process. The model contains module based on finite element method (FEM) for simulation of technological processes and cellular automata (CA) module for simulation of microstructure evolution. Design and selection of grooves and simulations of rolling process in macro scale are realized by FEM. The modeling results obtained by FEM are transferred to CA and used as input data. The results of simulations of microstructure evolution can be presented as snapshots of microstructure at arbitrary time, changes of average grain size, a grain size distribution, recrystallization fraction and flow stress during the process. The results of microstructure evolution obtained by FCA for 5mm round bars rolled in diamond and oval grooves are presented in the paper.

Development of a geometric modelling strategy for roll pass optimal design

Roll pass design is one of the most important tasks in shape rolling operations that are employed to provide raw materials with appropriate cross-section profiles for various industrial applications. Currently, many approaches, such as experience-based trial-and-error strategies, finite element methods, and expert systems, are applied to improve both quality and efficiency of roll pass design. However, due to lack of a flexible geometrical modelling strategy, the application of extant approaches is largely limited. This study attempts to develop a novel approach for generic geometrical modelling to support optimal design of roll passes. Features of the proposed model are analysed to support its application. Furthermore, a parameters estimation approach based on genetic algorithm is also developed to facilitate the transformation between the generic model and other geometrical models, as well as to improve its flexibility and applicability. The results from the case study presented in the paper indicate that the new model is more flexible and efficient, and that the parameters estimation approach also can achieve high transformation accuracy and efficiency.

Measurement of Grain Shape Uniformity

Abstract Cold working is well known to change the properties of metals and alloys. Deformation increases the strength of metals but usually reduces its toughness and leads to anisotropy of properties, that is, directionality. Hot working also produces similar affects; the microstructural results after hot work with low finishing temperatures may appear to be the same as from cold working. Hot rolling of shapes, sheet, plate or bar, for example, elongates the nonmetallic inclusions in the deformation direction, which will reduce the isotropy of mechanical properties. Hot working can also lead to segregation being elongated parallel to the deformation direction, which also reduces isotropy. Reducing the finishing temperature, i. e., the temperature of the steel at the final deformation pass, will promote “banding” – parallel alignment of the constituents into layers, such as alternate bands of ferrite and pearlite. This also promotes anisotropy of mechanical properties, chiefly toughness and ductility. Strength is not usually affected to a significant degree by banding, compared to toughness and ductility. In single phase metals and alloys, the grains will become elongated due to cold working. In hot working, the grain shape may not be equiaxed upon cooling if the finishing temperature is not high enough to promote complete recrystallization upon cooling to ambient temperature.

Ring-rolling design of yaw ring for wind turbines

In this work, a ring-rolling process to formulate ring-shaped components for a wind turbine is designed by means of a simulation and in an experimental approach. The target of the ring-rolling design is a yaw ring with an outer diameter of approximately 3,130 mm. The ring-rolling design includes the design of the geometry and the optimization of the process variables. A calculation method was used for the geometry design, in this case for the initial billet and the pre-form (or blank) sizes, and for the final rolled ring shape. Also, a deformation map-based approach was utilized to determine the initial ring-rolling temperature and feed rate of the mandrel. A three-dimensional finite element method was used to predict the formation of rolling defects and the deformed shape in the ring-rolled components. The design criteria are to achieve uniform distributions of the strains and temperatures as well as defect-free ring-shaped components. Finally, an optimum process design to obtain a sound large-scale yaw ring without defects is proposed. It is validated by comparisons between the experimental data and the FE analysis results.

Constitutive modeling of rolled shape memory alloy sheets taking into account pre-texture and anisotropic hardening

The drawing or rolling process endows polycrystal shape memory alloy with a crystallographic texture, which can result in macroscopic anisotropy. The main purpose of this work is to develop a constitutive model to predict the thermomechanical behavior of shape memory alloy sheets, which accounts for the crystallographic texture. The total macroscopic strain is decomposed into elastic strain and macro-transformation strain under isothermal condition. Considering the transformation strain in local grains and the orientation distribution function of crystallographic texture, the macro-transformation strain and the effective elastic modulus of textured polycrystal shape memory alloy are developed by using tensor expressions. The kinetic equation is established to calculate the volume fraction of the martensite transformation under given stress. Furthermore, the Hill's quadratic model is developed for anisotropic transformation hardening of textured SMA sheets. All the calculation results are in good agreement with experimental data, which show that the present model can accurately describe the macro-anisotropic behaviors of textured shape memory alloy sheets.

Control method for centering rolls in radial-axial ring rolling process

The control method of centering rolls was developed to ensure the circularity of rings and remove the process instability during a radial-axial ring rolling (RARR) process. The position control method is determined by the growth velocity of rolling rings and mathematical correlations among the key process variables, such as ring geometries, roll shapes, and feed rates of rolls. The moving coordinate of centering rolls were calculated by the growing velocity of an outer radius of the ring, VR, and the angle between the links of the ring’s center with the mandrel’s center and with the centering roll’s center, a, in the RARR process. The growth behavior of a ring and the angle provided moving coordinates for the centering rolls in real time. The hydraulic adjustment mechanism for establishing a successful RARR process is also proposed using the parameter design of the linkage assembly and beam bending theory. In order to verify the reliability of the control method, the FE-simulation under a FORGE software environment and ring rolling experiments of 42CrMo4 rings with an outer diameter of 510mm. The results show that these methods provided a high ring circularity and process stability.

Flatness Detection and Roll Shape Adjustment of Cold Rolled Material

Cold rolling rules according to the fixed incoming crown distribution of each crown control, raw material convexity fluctuations will destroy convex degree program, light is left with the residual stress, heavy waves. This paper discusses test incoming convexity, convexity control allocation method of residual stress.

Design method for intermediate roll in multi-stage profile ring rolling process: The case for excavator idler rim

In this paper, the design method for intermediate rolls has been developed to manufacture excavator idler rims in multi-stage profile ring rolling process, based on the uniform volume distribution element technique (UVDET) and the extremum rolling ratio(λmax). UVDET is presented as the ratio of the volume change of ring blanks to that of undeformed rings per unit height. λmax is defined as the ratio of the cross-sectional area of blanks to that of rolled rings. The theoretical value of intermediate roll shapes were determined by UVDET and λmax, i.e. the outer diameter and cross-sectional shape of the intermediate ring, respectively. FE simulations and profile ring rolling experiments using AISI 1035 steel alloys were performed to prove the validity of proposed design method. In order to investigate the deformation behavior in profile ring rolling of excavator idler rims, the expanding rule of plastic zone should be carried out firstly. The proposed roll design method led to the successful ring shape and the highest dimensional precision.

Prediction of geometrical profile in slit rolling pass

In the shape rolling process, the reduction of the number of passes is a challenging topic for the steel industry. This can be achieved by enhancing the design approach or by developing new rolling passes that allow the production of high cross-section reductions such as with the slit roll pass. However, in order to design a robust roll pass, the lateral spread of the workpiece must be predicted correctly to prevent incomplete, or even worse, excessive roll groove fulfilling (which may cause roll damage). In the present investigation, the possibility of using a finite element model to predict the lateral spread in a slit roll pass is investigated. The results of the finite element model are then used to adapt and calibrate two analytical models that were developed originally for strip rolling and shape rolling with concave grooves.

Convective instability in layered sloping warm-water aquifers

In a recent paper (McKibbin et al., 2011) some questions were posed about fluid and heat flows in a stratified groundwater aquifer with a small slope, subject to a perpendicular temperature gradient. The strength of shear flows in the direction of the maximum slope and the associated convected heat flux were quantified. This paper provides a method to quantify the stability of such flows and the shape and amplitude of convective rolls that may form when the critical Rayleigh number is exceeded. The associated issue of how the mean flow-path of a soluble species introduced into the aquifer is affected by the convective rolls, is also considered. The models formulated are for buoyancy-driven fluid flow in long, sloping warm-water aquifers with both smoothly- and discretely-layered structures.