Rolling Load Research Articles

Improving Steel Processing Through Thermo-Mechanical Simulation Studies

Thermo-mechanical simulation studies can be effectively utilized for optimization of processing parameters apart from development of new alloys, quality/yield improvement and material characterization. Physical simulation, being very close to the real world process, can be very helpful in near exact reproduction of the process, and in turn, better results. Thermo-mechanical simulation studies using Gleeble System found extensive applications in steel research and its processing. It can help in careful design of alloy chemistry, proper continuous casting operation to produce defect-free casting, and optimization of hot rolling and post-cooling parameters to produce the desired microstructure and annealing process after cold rolling to achieve the desired microstructure and properties, welding for easy fabrication, etc. Each of these steps needs to be fine-tuned and optimized to achieve the maximum benefit towards reduction in alloy additions, as well as quality and yield improvement during steel processing. A number of studies like continuous casting simulation for production of Cr-alloyed rail steel, hot deformation simulation and phase transformation behavior to optimize hot rolling of difficult to process high boron steel, and hot deformation simulation to bring down the rolling load and annealing simulation to achieve the desired hardness in low nickel stainless steel, etc. undertaken, helped to improve the processing of these steels. Details of these studies, results obtained, and the way to improve processing were discussed.

Residual Stresses Due to Rigid Cylinder Indentation and Rolling at a Very High Rolling Load

In this paper, residual stresses due to indentation and rolling of a rigid cylinder on a finite plate at a very high rolling load with a relative peak pressure of 22 are examined by two-dimensional plane strain finite element analyses using abaqus for the first time. In the finite element analyses, the roller is modeled as rigid and has frictionless contact with the finite plate. The geometry of the finite plate and its boundary conditions are assigned to correspond to those of fillet rolling of crankshafts with the constraint in the rolling direction. Finite element analyses with different meshes for single indentation on an elastic flat plate under plane strain conditions are first carried out, and the results are benchmarked with those of the elastic Hertzian solutions to establish the requirement of the finite element meshes for acceptable numerical results. The results show that the accuracy of computational results is limited by the discretization of the finite element analysis by a plot of the contact width as a function of the load. For accurate peak pressure, a total of at least eight linear elements are needed. Finite element analyses with different meshes for single indentation on an elastic–plastic flat plate under plane strain conditions are then carried out. The plate material is modeled as an elastic–plastic power-law strain hardening material with a nonlinear kinematic hardening rule for loading and unloading. The computational results are compared to establish the requirement of the finite element meshes for acceptable numerical results within 4 mm distance to the rolling surface for the crankshaft fatigue analyses. The computational results for rolling at the relative peak pressure of 22 show that the symmetric Hertzian or modified Hertzian pressure distribution should not be used to represent the contact pressure distribution for rolling simulation, while the computational results for rolling at the relative peak pressure of 5 show that the symmetric Hertzian or modified Hertzian pressure distribution may be used to represent the contact pressure distribution for rolling simulation. The computational results for the rolling case also show a significantly higher longitudinal compressive residual stress and a lower out-of-plane compressive residual stress along the contact surface when compared to those for the single indentation case. The results suggest that the effects of rolling must be accounted for when two-dimensional finite element analyses of crankshaft sections are used to investigate the residual stresses due to fillet rolling of the crankshafts under the prescribed roller loads. Due to the boundary conditions of the finite plate, the compressive residual stresses are larger when compared to those when the boundary conditions of the finite plate are fully relaxed.

Finite Element Analysis of Deformation Behavior in Al-2.2 wt.%Mg Alloy Subjected to Differential Speed Rolling

This paper reported the deformation characteristics of Al-2.2 wt.%Mg alloy processed by differential speed rolling (DSR) based on microstructure evolution and finite element (FE) analysis. The FE analysis was carried out to examine the distribution of the effective strain during DSR deformation with respect to the roll speed ratio. As the roll speed ratio increased from 1:1 to 1:4 for the lower and upper rolls, the amount of the effective strain imparted to the sample during DSR deformation increased, which was also accompanied with reasonably homogeneous distributions of microstructure and microhardness over the entire samples. At the roll speed ratio of 1:4, the effective strain of ~1.5 was calculated in the top part of the DSR-deformed sample. In addition, the rolling load was observed to decrease with the roll speed ratio increased, which was attributed mainly to the influence of friction between the rolls and sample.

Finite element approach toward an advanced understanding of deep rolling induced residual stresses, and an application to railway axles

Abstract A full-scale railway axle, made of medium strength steel EA4T and adopted for high-speed applications, is deep rolled. The induced residual stresses were experimentally characterized by X-ray diffraction and hole drilling. A realistic finite element model is proposed to overcome some of the existing shortcomings in simulation of deep rolling. Deep rolling coverage is defined, formulated and incorporated into the simulation. The model is validated by the experimental measurements. A parametric study is performed to investigate the effect of rolling force (4–19 kN), rolling feed (0.1–0.7 mm/rev) and roll geometry (1.5–10 mm roll tip radius) on the distribution of residual stresses and the induced hardening. A fatigue crack propagation algorithm is used to analyze the influence of the technological parameters on the lifetime of railway axles. Lower feeds, higher loads and thicker rolls, all resulting in higher coverage, can result in higher improvement against fatigue crack propagation. However, extremely high coverage can deteriorate the performance of deep rolled components. Coverage can effectively serve as a master parameter in deep rolling. As a general rule of thumb, adopting deep rolling feed to get a coverage level of 500–900%, while avoiding too high rolling loads and too thin rolls, can induce a suitable compressive residual stress distribution; and effectively prevent/retard fatigue crack propagation.

A first step towards a simple in-line shape compensation routine for the roll forming of high strength steel

The roll forming process is increasingly used in the automotive industry for the manufacture of structural and crash components from Ultra High Strength Steel (UHSS). Due to the high strength of UHSS (<1GPa) even small and commonly observed material property variations from coil to coil can result in significant changes in material yield and through that affect the final shape of the roll formed component. This requires the re-adjustment of tooling to compensate for shape defects and maintain part geometry resulting in costly downtimes of equipment. This paper presents a first step towards an in-line shape compensation method that based on the monitoring of roll load and torque allows for the estimation of shape defects and the subsequent re-adjustment of tooling for compensation. For this the effect of material property variation on common shape defects observed in the roll forming process as well as measurable process parameters such as roll load and torque needs to be understood. The effect of yield strength and material hardening on roll load and torque as well as longitudinal bow is investigated via experimental trials and numerical analysis. A regression analysis combined with Analysis of Variance (ANOVA) techniques is employed to establish the relationships between the process and material parameters and to determine their percentage influence on longitudinal bow, roll load and torque. The study will show that the level of longitudinal bow, one of the major shape defects observed in roll forming, can be estimated by variations in roll load and torque.

Numerical Treatments of Slipping/No-Slip Zones in Cold Rolling of Thin Sheets with Heavy Roll Deformation

In the thin sheet cold rolling manufacturing process, a major issue is roll elastic deformation and its impact on roll load, torque and contact stresses. As in many systems implying mechanical contact under high loading, a central part is under “sticking friction” (no slip) while both extremities do slip to accommodate the material acceleration of the rolled metal sheet. This is a crucial point for modeling of such rolling processes and the numerical treatment of contact and friction (“regularized” or not), of the transition between these zones, does have an impact on the results. Two ways to deal with it are compared (regularization of the stick/slip transition, direct imposition of a no-slip condition) and recommendations are given.

Analysis of Properties of Selected Aluminium Alloys, Obtained by Twin Roll Casting Method and Subjected to Cold Rolling Process

Modern manufacturing technologies of flat cold-rolled products made of aluminium and its alloys are based on raw materials produced with the use of continuous casting technology. One of the most frequently used integrated production processes, based on continuous casting of metal, is twin roll casting method (TRC). In TRC method liquid metal flows into the area formed by two water-cooled rolls, solidifies and next is deformed (rolled) which allows to obtain strip with several millimetres thickness. Thanks to this, it is possible to eliminate hot rolling stage from the typical production technology, and directly subject obtained sheets to cold rolling process.This paper presents results of cold rolling strain dependency on the mechanical properties of tested aluminium alloys from 1XXX, 3XXX and 8XXX series, produced in the laboratory conditions with the use of TRC method. Furthermore the rolling loads and basic mechanical properties, determined in an uniaxial tensile, were examined.

Influences of off-sized rollers on mechanical performance of spherical roller bearings

Based on a set of formulae for calculating elliptical contact parameters and elastic deformation developed by Houpert and mechanical analysis, a numerical model is established for calculating the roller load distribution and shaft axis orbit of spherical roller bearings with considering off-sized rollers in this paper. A numerical calculation example is carried out to investigate the effects of single off-sized roller and multiple off-sized rollers on spherical roller bearing roller load distribution and axis orbit. Results show that the roller maximum load will increase as its off-sized diameter becomes larger than the nominal diameter, and the roller maximum load will decrease as its off-sized diameter is smaller than the nominal diameter. The maximum loads of the rollers in the two rows neighboring on the off-sized roller/rollers can also be affected. Meanwhile, roller diameter error will largely affect the axis orbit and inner ring radial displacement of spherical roller bearings.

Experimental Investigations on the Dynamic Behaviour of O-Type Wire-Cable Vibration Isolators

A series of periodic loading experiments were carried out on the O-type wire-cable vibration isolators. The isolators were loaded under shear, roll, and tension-compression loadings. When subjected to shear and roll loads, the restoring force-deformation curves generated by the isolators formed symmetric hysteresis loops. However, when the isolators were loaded with tension-compression loads, the isolator produced asymmetric hysteresis loops. It is found through the experiment that the dynamic characteristics of the isolator are determined by the loading amplitude as well as the geometric parameters of the isolator while they are almost independent of loading frequency within the testing frequency range. Based on the experimental data, the dynamic response of the isolator was modeled by a modified normalized Bouc-Wen model. The parameters of this model were identified through an identification procedure that does not involve any nonlinear iterative algorithms. Comparison between the identification results and the experimental data suggests that the identification method is effective. With the model and the identified parameters, the frequency response of an O-type wire-cable vibration isolator-mass system was evaluated. Typical nonlinear response behaviors were found when the isolator was used in tension-compression mode while the response appears to be similar to that of a linear system when the isolator was used in shear and roll mode.

Friction Coefficient’s Numerical Determination for Hot Flat Steel Rolling at Low Strain Rate

In this paper, a non-linear quadratic expression of the coefficient of friction at both entry and exit sides have been derived from the equations of rolling load in Hot Rolling Bland and Ford’s program (HRBF). The study developed a numerical model for the estimation of coefficient of friction for steel (HC SS316) of different thicknesses on two high reversing mills. The equations for coefficient of friction on entry and exist sides of the mills were modelled from Hot Rolling Bland and Ford’s program (HRBF). The equations were modelled such that the friction coefficient can be expressed as a function of process parameters measurable during rolling. The capability of the model was verified by using a number of specimens of HC SS316 with predetermined hot rolling experimental data. A good agreement was noted between the predicted friction coefficient and the measured one.

Grain and geometry size effects on plastic deformation in roll-to-plate micro/meso-imprinting process

Roll-to-plate (R2P) imprinting process is an efficient technique to fabricate functional surface microstructures on a metallic substrate, which is widely used in the fields of microfluid, heat and mass transfer, and friction/drag reduction. However, the plastic deformation of microfeatures is significantly influenced by size effects. In this paper, the effects of grain and geometry size on the plastic deformation in R2P micro/meso-imprinting process were investigated by experiments and numerical simulations. According to the characteristics of the R2P micro/meso-imprinting process, a numerical model of R2P micro/meso-imprinting process was established. The experiments with pure copper were conducted through a self-developed R2P micro/meso-imprinting system. The size effects were studied via the evaluation of the formed height, rolling force and microhardness distribution. It is concluded that the rolling load reduces because of the decrease of flow stress caused by the weakening of grain boundary strengthening effect when the grain size increases. The wider groove and larger fillet could enhance the microforming ability of material and reduce the forming loads. The effect of groove width is more significant than that of the fillet. The microhardness distribution shows that the coarse-grained material has higher hardness than the fine-grained material in the central regions of the cross-section for the formed feature due to the penetration effect of deformation. However, the hardness in the central regions dwindles with the increase of the groove width and fillet. It is also found that the profile irregularity and surface roughness of the formed feature increase with the grain size and rolling depth. The results would provide a basis for further exploration in R2P micro/meso-imprinting process.

Optimal Sizing and Control of Battery Energy Storage System for Peak Load Shaving

Battery Energy Storage System (BESS) can be utilized to shave the peak load in power systems and thus defer the need to upgrade the power grid. Based on a rolling load forecasting method, along with the peak load reduction requirements in reality, at the planning level, we propose a BESS capacity planning model for peak and load shaving problem. At the operational level, we consider the optimal control policy towards charging and discharging power with two different optimization objectives: one is to diminish the difference between the peak load and the valley load, the other is to minimize the daily load variance. Particularly, the constraint of charging and discharging cycles, which is an important issue in practice, is taken into consideration. Finally, based on real load data, we provide simulation results that validate the proposed optimization models and control strategies.

Simulation Analysis of In-Service Bamboo and Pine EGP Composite Flooring

Bamboo is a renewable material that has been gaining attention in several sectors of production and research because of its potential. Its special characteristics of rapid growth, short harvest cycle, diversity and excellent mechanical properties. The objective of this work was a physical-mechanical analysis of flooring manufactured by a combination of bamboo (Dendrocalamus giganteus) laminate slats and wood (Pinus taeda) edge-glued panels (EGP). It was based on the ASTM D2394-83/1994 standard, which describes the procedures for mechanical simulation of in-service floors, such as indentation loads applied on small areas, falling ball impact, rolling load, abrasion and friction tests. The results were satisfactory when compared with those of other types of wood. The research showed lignocellulosic composite of Pine EGP with a bamboo surface, in terms of mechanical strength according the ASTM’s standard, is viable and feasible. Therefore, it results that “EGP/Bamboo” composite can be successfully applied for internal floors.

Numerical Simulation on Correcting Camber and Wedge of Steel Slabs in Hot Rolling Mill

In the hot rolling process, the steel slab may experience a temperature gradient along its transverse direction which may cause camber and wedge after rolling. Camber and wedge phenomenon will affect the quality of the steel plate. To eliminate camber and wedge phenomenon, a pair of side guides is placed before and behind the hot rolling mill. The position mode and the force mode are the control modes for side guides to correct the slab shape and to guide the slab to follow rolling direction. Finite element analysis using ABAQUS was applied to simulate hot rolling process to find the correction mechanism of rolling equipment. The centerline of slab was traced and the shape of slab was predicted. The difference of rolling load between work side and drive side of roller was determined. Furthermore, the load, stress and velocity distribution on the slab at roll bite were analyzed. By using numerical model, hot rolling parameters including side guide control strategy can be predicted, which can provide the hot rolling line as a guideline to improve the quality of the steel slab.

Load Distribution in a Rolling Element Bearing under Dynamic Radial Load

External load in a bearing is transferred from one race to another race through the rolling elements. In the present work, an investigation has been made to estimate the load on a rolling element in a bearing subjected to dynamic loading. The dynamic loading, in the present study, included harmonic and periodic loadings which are deterministic functions of time. The roller load is also investigated under random loading with known statistical values of mean and variance. Numerical values have been obtained for NJ204 bearing with known radial clearance. These results show the variation in the spectra obtained for different nature of external loadings. These results can be expected to satisfy the difference in theoretical and experimental spectra obtained by earlier researchers.

Estimation of lateral tire–road forces and sideslip angle for electric vehicles using interacting multiple model filter approach

Vehicle control systems require certain vehicle information (e.g., tire–road forces and vehicle sideslip angle) concerning vehicle-dynamic parameters and vehicle–road interaction, which is difficult to measure directly for both technical and economedic reasons. This paper proposes a novel method to estimate lateral tire–road forces and vehicle sideslip angle by utilizing real-time measurements. The estimation method is based on an interacting multiple model (IMM) filter that integrates in-vehicle sensors of in-wheel-motor-driven electric vehicles to adapt multiple vehicle–road system models to variable driving conditions. Based on a four-wheel nonlinear vehicle dynamics model (NVDM) considering extended roll dynamics and load transfer, the vehicle–road system model set of the IMM filter is consists of a linear tire model based NVDM and a nonlinear Dugoff tire model based NVDM. Therefore, the IMM filter can integrate the estimates from two kinds of different vehicle–road system models to improve estimation accuracy. To address system nonlinearities and un-modeled dynamics, the interacting multiple model-unscented Kalman filter (IMM-UKF) and the interacting multiple model-extended Kalman filter (IMM-EKF) are investigated and compared simultaneously. Simulation using Matlab/Simulink-Carsim is carried out to verify the effectiveness of the proposed estimation methods. The results show that the developed estimation methods can accurately estimate lateral tire–road forces and the vehicle sideslip angle.

Influence of Friction on the Loads in a Roll Forming Simulation with Compliant Rolls

Roll forming is an important economic forming process for manufacturing of profiles. For an optimal design of the process, it is important to determine the loads occurring during the forming process. Furthermore, the information of the load behavior enables an evaluation of the formability of the planned profiles with the chosen roll forming machine. An experimental determination of loads in roll forming processes requires a complex measurement setup in combination with a high amount of measurement devices. Hence, the analysis of roll loads by means of finite element simulation is of special interest. The use of roll forming simulations for the determination of geometrical outputs is state of the art. However, due to simplifications, a realistic and reliable output of roll loads in roll forming is impossible. Therefore, the compliance behavior under load and the frictional behavior have to be incorporated in the simulation model. The friction behavior in roll forming processes is presented to be very insignificant in literature. The value of the friction coefficients vary in a broad range. Due to lack of knowledge in the compliance behavior of the used stands, simulation models with rigid rolls are still state of the art. This paper will show the reproduction of realistic roll loads, e.g. torques and forces, in a roll forming simulation. Therefore, the friction coefficients of each roll-sheet metal contact will be gained experimentally and implemented in the numerical model. Furthermore, a characteristic compliance of the roll forming stands will be analyzed and also considered in the simulation. Finally, the influence of changing parameters, e.g. raise of the friction coefficients, on the roll loads will be investigated. To verify the simulation the numerical results will be compared to data gained by experiments.

Dynamic Transformation during the Torsion Simulation of Strip Rolling

Seven-pass strip rolling simulations were carried out on a 0.06%C and a 0.09%C-0.036%Nb steel. The rolling loads (mean flow stresses or MFS’s) did not increase as the temperature decreased during the simulation. This is ascribed to the occurrence of dynamic transformation. The simulation results are compared to the high temperature flow curves determined on eight plain C and Nb-modified steels in both compression and torsion and at a series of temperatures and strain rates. When the associated MFS’s are plotted against inverse absolute temperature in the form of Boratto diagrams, the stress drop temperatures, normally defined as the upper critical temperature applicable to rolling, Ar3*, are shown to be about 40 degrees above the paraequilibrium and about 20-30 degrees above the orthoequilibrium Ae3’s. These drops are ascribed to the dynamic transformation of austenite to ferrite, a softer phase. The characteristics of the ferrite produced dynamically are described and the transformation is shown to be displacive in nature, leading to the appearance of fine Widmanstätten plates. These plates coalesce into polygonal grains on further deformation and on holding.

Allowable Bending Fatigue Stress of Rails

Allowable bending fatigue stress is an important input for rail section design because of the nature of repeated loading on railways. The majority of rail failures have their origin in fatigue. In the American Railroad Engineering and Maintenance-of-Way Association (AREMA), there is only a fatigue test under the name of rolling load test for bonded joints; there are no fatigue tests for parent rail and welded joints. With respect to bonded joints, there is no known railroad or transit agency that uses plain bonded joints as an alternative to either flash butt weld (FBW) or alumino thermite weld (ATW) joints. A rail or weld should be able to resist at least 2 million stress cycle repetitions without developing any cracks. In this paper, allowable bending fatigue stress is formulated analytically with the nominal stress method (S-N). Marin’s six modification factors are applied to the laboratory-determined fatigue limit to account for surface conditions, size, load, temperature, reliability, and shape. Then, Goodman’s mean stress correction factor is applied to account for mean tensile stress in the rail. A brief literature review on the modification factors is included. The allowable bending fatigue stress is calculated and validated theoretically, then compared with the recommended AREMA value. Finally, the current AREMA formula and its recommended value for allowable bending fatigue stress are discussed.

Methods and instrumentation for the biomechanical analysis of slalom water skiing

Many highly dynamic sporting activities are now quantitatively analyzed to optimize athletic performance and provide information required for equipment optimization. Water skiing (with its challenging environmental conditions) has to date received only minimal attention in this area. The objective of this study was to create an instrumentation system suitable for analyzing the biomechanics of slalom water skiing. An instrumentation system and methodology were designed and implemented to collect quantitative data for slalom water skiing at the advanced level. The chosen performance parameters of interest for slalom water skiing turns were skier velocity, ski acceleration, ski deceleration, ski roll and rope load. Four sensors were used to collect data to calculate the parameters of interest: a boat-based global positioning sensor unit, a skier-mounted global positioning system unit, axial load transducer mounted in the tow rope and a ski-mounted inertial measurement unit. A novel custom-fabricated and programmed wireless communication system was incorporated in the study to allow rapid data communication and acquisition. Results indicate that the instrumentation system developed for this study was successful in providing the data deemed necessary for the biomechanical analysis of slalom water skiing. The data provide a unique look into the complex three-dimensional biomechanics of slalom water skiing. This same quantitative data would be suitable for advanced ski equipment design, injury prevention and high-level athlete coaching of slalom skiers. It is also expected that the equipment developed for this study would be suitable for use at novice and intermediate levels of water skiing and with minor alternations could be applied to the analysis of other open-water sports.