Reference revision · 2026-09-27
In Geometry, choose Roller, select the core metal and coating elastomer, and enter outer radius and coating thickness. Set Width condition and Roller width there. A roller is an auxiliary geometry element: adding, selecting or editing an unconnected roller does not create a load case, replace the specimen geometry, or change the active simulation. The usual geometry-driven case selection applies to specimens, not rollers. For an optional roller assessment, explicitly create a Rubber-covered roller contact case in Cases, select the roller in its Geometry input, and connect that case to a separate Simulation. Set force and contact condition there. An explicitly linked contact case or thermal-process roller station uses the roller width condition to choose its solver variant.
| Geometry choice | Calculation | Meaning of Roller width |
|---|---|---|
| Infinite width | Fast analytical elastic-layer fields with a numerical 2D contact solve. Plane strain: axial displacement and strain are zero. No free-end spreading. | Reference loaded span used to convert total force into line load F/width. It does not introduce physical ends into the calculation. |
| Finite width | 3D small-strain elastic contact. The two free rubber ends can bulge and spread axially; pressure varies across the width. This takes longer. | Full physical axial width of both rubber and core, uniformly pressed against the rigid flat. |
The rubber is perfectly bonded to the rigid metal core: no slip or separation at that interface. Changing width mode retains material choices, radius, thickness, width and load. Old records with only a case-level Roller face length retain that reference span in Infinite width until a width is entered in Geometry. Finite width always requires its dimension in Geometry.
Coating color, hollow cores and shafts
In Materials & coating, use the silicone color swatches or Custom color picker. Color is saved with the geometry and shown on the 3D surface, radial section and material legend. It changes appearance only, not material properties or contact results.
The geometry editor keeps relevant fields in one compact table. Use the information icon beside a field for its explanation. Calculated dimensions and More details expand below the inputs. Inactive bore, shaft and wall controls stay hidden while their saved values are preserved.
Core construction offers Solid core, Hollow core or Core with shaft. Hollow core adds Core bore diameter: a through hole smaller than the core outer diameter. The preview shows the opening and metal wall thickness. Core with shaft adds Shaft diameter and Shaft overall length. The shaft uses the selected core metal and is centred in the roller.
Shaft overall length is the full end-to-end dimension, including the coated Roller width. Each exposed end is (Shaft overall length − Roller width) / 2. For example, a 100 mm roller with a 150 mm overall shaft has 25 mm exposed at each end. Shaft diameter cannot exceed the core outside diameter. Roller width defines the loaded width for standalone contact and finite-width process rollers. In a thermal process, Infinite width uses the plate width as its loaded span. Shaft length never replaces the contact span.
Only dimensions for the chosen construction appear. Switching construction preserves the hidden values for reuse, and switching away from Roller and back preserves the whole configuration. The contact solver still assumes a perfectly rigid core: hollow-wall flexibility, shaft bending and bearing support are not predicted. Infinite width still means plane-strain coating response even when the preview includes a shaft.
Results and controls
Both variants give contact pressure, nip width, indentation, coating stress, strain and displacement. The finite variant adds the contact footprint across the width, axial displacement v, axial strain εy and end bulging. In the axial panel, choose Across width at the nip centre or Free end along the nip. Field selectors change the contour quantity. Mesh magnification changes display only. Field CSV exports the centre section; Axial fields CSV exports the half-width axial section and free end in mm, MPa and dimensionless strains.
Friction
Friction applies only between outer rubber and the rigid flat. Frictionless means no tangential traction; Sliding +x or −x prescribes traction on rubber q = ±μp. A friction coefficient alone cannot determine partial slip or free rolling. No adhesion, rolling resistance, heating or time-dependent rubber response is inferred.
Equations, convergence and limits
x follows the nip, y is the roller axis and z points into the coating. Both variants approximate the curved coating locally as a flat bonded layer, with initial contact gap x²/(2R). The long-roller solver uses Fourier/Airy elastic modes and force-balanced nonnegative contact pressures.
The finite solver uses 3D eight-node B-bar bricks: full integration of deviatoric elasticity and mean volumetric strain to reduce near-incompressible locking. The core boundary has u = v = w = 0. Symmetry at y = 0 fixes only v; the outer end is traction free. Distant x boundaries are fixed, six coating thicknesses or more from the nip centre. Contact is solved with a finite penalty, active contact set and total-force balance. A second mesh must change indentation and maximum outward end displacement by less than 5%. This check does not establish convergence of sharp-edge peak pressure or stress. Stress/strain contours recover volume-weighted element-centre fields.
The coating must be thin relative to the radius (h/R ≤ 0.2), contact extent small (a/R ≤ 0.15), and strains and indentation/thickness within 15%. The core modulus must be at least 100 times the coating modulus. These are screening limits, not accuracy guarantees. Finite width requires measured Poisson ratio below 0.5; exactly incompressible rubber needs a mixed-pressure model. Large deformation, hyperelasticity, core bending, end caps, crown, tilt and imperfect bonding are excluded.
Numerical checks cover constant-strain elasticity, rigid motion, contact force equilibrium, bonded displacement, free-end spreading symmetry, friction reversal, mesh/domain/penalty sensitivity, and the wide-roller approach to the plane-strain result. These are numerical checks, not experimental validation for a specific rubber compound.
Wide roller · film traction and buckling
In the contact case, set Film assessment to On. These controls appear only with Infinite width geometry. Film assessment is Off by default. Switching to Finite width retains the entries but excludes film traction and buckling screening from the run; switching back restores them.
Film thickness, modulus and Poisson ratio describe an isotropic elastic film passing through the nip. Film width is the film span across the roller axis, no larger than the geometry reference width. Entry tension is total force across that film width. Roller speed and web speed are signed in the +x direction; Slip speed smooths the transition around zero relative velocity. Equal velocities produce zero traction in this regularized sliding model, not a static-friction solution.
The film friction law is μ(p) = min(μcap, max(0, μ0 + gain ln(1 + p/pref))). Set pressure gain to zero for constant friction. Traction on the film is τ = μ(p)p tanh((vroller − vfilm)/vslip). The membrane force balance is d(σx h)/dx = −τ. Entry tension is specified; exit tension is predicted. The earlier linear exit-stress adjustment is deliberately omitted because it changes stress without adjusting traction. These film tractions are a one-way assessment using the pressure; they do not recalculate rubber displacement or its separate outer-surface friction loading.
Positive stress is tensile; negative stress is compressive. Film strain is σx/E before buckling. Film rigidity D = Eh³/[12(1−ν²)]; critical compressive stress σcr = kπ²D/(b²h). Film buckling coefficient k describes assumed support conditions. Film effective span b accepts a positive physical unsupported span, or zero for the source-inspired nip estimate: the extent above 2% peak pressure, bounded to 0.5–25 mm. The estimate uses panel edges; the earlier estimate used sample centres.
Buckling index is max(0,−σx)/σcr. One means the screening threshold is reached. The factor is σcr divided by maximum compressive stress; with no compression it is reported as No compression. Contact fraction above threshold measures length within contact above 1% peak pressure; it is also the area fraction under the uniform-width assumption. The graph selector offers stress, strain, film traction and buckling index. Film CSV exports all four, pressure, friction, critical stress and effective span.
This unsupported-plate estimate is not a validated supported-nip instability calculation. No wrinkle wavelength/amplitude, nonlinear film state, postbuckling, rubber buckling, or feedback of film deformation into contact is predicted. Negative exit force means the imposed speed/tension combination demands compression and needs a postbuckling/contact model to determine its realized state.
Adapted elements: pressure-dependent friction, regularized slip, film membrane equilibrium and plate-buckling screening from the supplied silicone_roller_contact_MASTER_V4_FILM_TRACTION_BUCKLING.m. The supplied Silicone Roller Pressure Model_v2.pdf describes local hyperelastic foundations and explicitly excludes exact bonded lateral constraint; those foundation laws have not replaced the bonded elastic-layer solver.
Moving thermal process · roller boundaries
Open the thermal case, set Process mode to Moving Process, then open Upper or Lower. Select a Plate or Rectangular section workpiece. Choose a roller ID directly in a row’s Boundary condition dropdown. Create your rollers in Geometry first; adding a geometry alone never changes the process. Add a row at each desired contact centre. Up to 12 roller assignments are supported; the same geometry can be reused at several locations with independent force and temperature. The separate Rollers tab is no longer needed.
| Control | Function |
|---|---|
| Boundary condition / roller ID | Selects core, elastomer, radius, coating thickness and width variant. Its material links travel with the simulation. |
| Upper / Lower tab | Chooses the surface. Opposed rollers may share a centre. |
| Position / centre (m) | The row location is the nip centre, measured from the inlet. Its edges are predicted from roller geometry, material and force, independently of spacing between rows. At the inlet/outlet only contact within the scheduled travel is applied. |
| Coordinate | Length enters centres in metres. Time enters arrival times in minutes, with x = velocity × time. Switching coordinates preserves physical centres. Changing velocity in Length mode changes dwell time; in Time mode it changes centre locations. |
| Contact settings button | Opens temperature, conductance, pressure dependence and outside-contact settings beside the chosen roller. Force is entered directly in the table. |
| Applied load | Roller rows show Force (N): the total normal force on that roller. Contact pressure and nip width are calculated from this force, roller geometry and the active contact material properties. Ordinary rows show Pressure (MPa). Values are stored separately; changing boundary type never converts pressure into force. |
| Roller (°C) | Prescribed surface temperature, or initial roller temperature when Rotating thermal model is selected. |
| h (W/m²·K) | Thermal contact conductance at the reference pressure. The initial 1000 is an editable example, not a calibrated prediction. |
| Pressure exponent / reference pressure | Optional contact law h = h_ref (p/p_ref)^n. Default n = 0 gives constant conductance; p_ref is in MPa. Use measured or justified values. |
| Outside contact | By default, Follow profile interpolates the background from neighboring ordinary rows; the roller centre is not a background knot. Select Custom to use its saved boundary type, environment temperature and shared background pressure as an explicit point. Background pressure remains additive and can be edited here. The main temperature cell becomes roller temperature; it is not interpolated into surrounding environmental temperatures. |
| Remove roller / row | Choose an ordinary boundary condition to remove just that face’s roller. Deleting a row removes its upper and lower roller assignments. Roller geometry is retained; normal undo and record save apply. |
| Fill boundary down / Copy to opposite surface | Copies the selected boundary and roller settings to subsequent rows or the opposing face at the same centre. Added rows do not automatically inherit a roller. Overlapping same-face nips are rejected when solving. |
Older saved station positions are shown as boundary rows without changing the background temperature or pressure profile; edits save their row bindings. Normal record copying and snapshots retain roller geometry references and boundary settings.
Pulling velocity maps position to time: x = vt. Each roller uses its selected coated or metal contact model to predict its nip pressure. Upper and lower roller pressure are independently added to the existing cycle pressure. The contact heat flux is h times the difference between roller and surface temperatures. It replaces the ordinary thermal boundary over the covered area while that part of the workpiece passes through the nip; the uncovered area retains the existing boundary.
The Upper/Lower editor uses compact Workbench rows, with the Pressure & temperature plot to the right. Drag the divider to resize the table and plot. The plot remains available before a roller is assigned, showing the background schedule. Boundary settings holds the face’s film coefficient and its existing lock control; it applies to background convection/tool contact, while roller contact uses its own conductance. Process settings holds die length and the inlet/outlet assumptions; mode and speed remain in the toolbar. LiveLoad also shows the combined plot. Contact pressure is recalculated in the background from the current force, geometry and material properties. The plot uses °C on the left and MPa on the right, with one shared pressure curve and a dashed global-pressure line. Both tables and the material models use this same through-thickness pressure. It is the global profile plus the largest active roller contribution at each position; opposing pressures are not added. This is a 1D pressure-envelope approximation, not a coupled roller equilibrium solution. Outside a roller’s predicted nip its contribution is zero. The pointer readout shows global + roller = total, and selecting a roller in the zoom list shows this breakdown at its centre. Shaded bands mark predicted nip widths. Choose a roller in the zoom list to inspect its narrow pressure profile. Moving the pointer shows sampled values; Plot CSV exports the full process. When inputs change, the previous prediction is hidden while recalculating.
Thermal results include the same combined plot for the saved run, plus Roller boundary history. Choose pressure, conductance or boundary temperature; zoom to a station and export Boundary CSV. The station table reports nip width, local peak pressure, entry/exit time and force-balance error. Pressure curves are averaged across workpiece width, so local finite-roller peak pressure differs from the plotted average. The time solver resolves individual nip panels even when the normal output interval skips the contact; additional snapshots are saved across each nip.
Supported scope and assumptions
Infinite-width process rollers span the full workpiece width with uniform coverage across it. Their line load is total applied force divided by workpiece width; the saved geometry width remains available for standalone contact. Coverage along travel is still limited to the predicted nip. Finite-width rollers use their actual width, are centred across the plate, and may not exceed the workpiece width. Same-side nips may not overlap. Roller forces and thermal conditions remain independently prescribed. The shared pressure envelope is not an equilibrium solution for a freely bending web. The workpiece is locally a rigid flat for contact and a through-thickness thermal section for heating. A partial-width contact is averaged across the workpiece; lateral and axial temperature gradients are not resolved. A full-width infinite roller can replace a prescribed-temperature background during nip contact and restore it outside the nip. Partial-width finite rollers require convection, tool contact or insulation on that face; a prescribed-temperature background cannot represent that mixed condition. A width-mismatch message reports plate width and actual roller coverage.
Pressure supplies a boundary history and the optional contact-conductance law. It does not automatically solve compaction, resin flow, thickness change or plate deformation. Prescribed-temperature mode does not include roller heat capacity. Rotating thermal mode adds roller heat storage and conduction. Frictional heat, rate-dependent rubber behavior, temperature-dependent contact stiffness and film buckling remain excluded. The separate wide-roller film assessment remains available in its standalone case. Contact conductance needs its own calibration; rubber pressure alone cannot determine it.
Thermal contact conductance and interface heat transfer background
Rotating roller heat transfer
In a roller row, open Contact settings and choose Rotating thermal model. The row temperature becomes its initial temperature. By default RPM = web speed / circumference, with consistent metre/minute units and no slip. Machine age at web entry controls how long the roller has already operated when the analyzed strip enters. It is separate from that strip’s travel time. Set the surrounding air temperature and film coefficient, plus optional absorbed irradiation outside the nip.
The solver tracks temperature around the circumference and through radial metal/coating layers. Rotation transports the stored heat; conductivity redistributes it, and density × specific heat determines storage. The predicted nip and conductance supply the contact arc. Constant thermal properties come from the selected core and elastomer materials. No heat is generated merely by rotation.
During contact the boundary is h(Tweb − Troller). Outside contact it is hair(Tair − Troller) plus absorbed flux. The hollow bore is insulated and removes the corresponding thermal mass; shaft extensions and axial/end heat losses are excluded. Both coated and all-metal rollers are supported. Infinite-width geometry uses the workpiece span; finite rollers use a width-averaged thermal cross-section, not a 3D end-temperature solution.
The plate and roller temperatures are iterated to a 0.1°C contact-temperature tolerance. Warm-up uses one fixed contact-web temperature from the selected moving-web solution, representing continuous feed at approximately stationary process conditions. This is not a simultaneous startup simulation of every strip in the line. The existing pressure model does not change with roller temperature. Friction and rubber hysteresis heating are not included.
Thermal results show contact, mean-surface and core temperatures against machine running time, plus RPM, surface range, energy residual and Thermal CSV. The input preview continues to show initial temperatures until Run. The 72 angular × 16 radial cell model conserves energy but averages very narrow nips; local flash-temperature predictions require a finer dedicated contact model.
Live Process · 3D boundary view
For a moving thermal process, open Upper or Lower and choose Live Process beside Pressure & temperature. Both surfaces, zones and rollers appear together and update when the boundary rows, forces or geometry definitions change. Roller centres follow their row positions. The continuous workpiece spans the scheduled travel distance; it is not an animation of a finite coupon.
Solid plate shows the workpiece as one body. Layered laminate uses its assigned laminate, actual ply thicknesses and material finishes. Link a laminate to the thermal case or workpiece to enable this option. All dimensions use a common scale. Finite rollers retain their coating color, face width, core and shaft dimensions. Infinite rollers are drawn across the plate width.
Drag to rotate, Shift-drag to pan, and scroll to zoom toward the pointer. Double-click a zone or roller to fit it, or empty space to magnify it. The + / − controls and percentage selector also change zoom. Side and Top provide fixed starting views. Expand opens a larger window; Fit selected frames the selected zone or roller; Fit whole process resets the view. Keyboard arrows rotate and Home resets. Select an object or use the inspection dropdown to read its details. Callouts adds labels on the scene; All zones & rollers expands the full list. SVG saves the current view.
Zones show the upper and lower boundary conditions, programmed temperature ranges and global pressure. Rollers show applied force, prescribed surface temperature, contact conductance, dimensions and predicted nip / peak pressure. Red arrows indicate force direction and red strips indicate predicted contact footprints. These are boundary inputs and contact predictions, not solved interior temperatures or a deformed plate. Incomplete contact inputs produce a pressure-preview message while retaining the geometry view.
Live Process boundary symbols
Symbols shows each zone’s upper and lower boundary types and roller contact locations. Curled air lines indicate convection; opposed red/blue arrows indicate contact heating or cooling; a thermometer indicates prescribed temperature; a hatched surface indicates insulation. Symbols are schematic and do not specify airflow, equipment size or solved heat-flow direction.
Open Boundary symbol key & annotations and select a zone. Its Upper and Lower selectors default to Auto, following the actual boundary inputs. You can choose a symbol-only annotation for convection, contact, radiation or the planned laser-heating model. Radiation uses wavy rays; laser uses a beam and spot. Annotations are shared with the expanded view during this view session and do not change saved boundary conditions. Radiation is not separately solved by the current film law, and selecting a laser symbol does not activate a laser solver.
All-metal rollers
In Geometry → Roller materials, set Roller surface to All metal. Select steel (or another metal) in Core metal. Roller outer radius now describes the metal surface; the derived outer diameter is twice this radius. Coating material, thickness and color are hidden and retained if you switch back.
Metal contact model offers Elastic metal fields and Hertz pressure only. Both predict the same elastic Hertz pressure against a rigid flat from force, radius, loaded width and the selected metal’s modulus and Poisson ratio. Elastic metal fields also shows local stress, strain and displacement; its sliding traction is a one-way calculation that does not alter the normal pressure. Hertz pressure only is the faster frictionless option.
Model limits and deformation reference
These are local line-contact models, including for finite-width metal geometry. They do not predict axial end spreading, shaft bending, hollow-shell ovalization, plasticity or bearing compliance. The half nip must be at most 5% of radius, loaded width at least ten nip widths, and metal depth at least eight half nips. The displayed field extends eight half nips into the metal; this is not a fixed core boundary. Displacements use a datum at the bottom centre of that local field. Geometric nip flattening is a²/(2R), not the total approach of the roller shaft. Verify the elastic assumption against the selected material’s yield limits.
Select the roller ID in a moving thermal boundary row as usual. Enter force in N. Its calculated pressure is added to the global pressure over the predicted nip; temperature and contact conductance remain the boundary-row settings. Finite-width metal contact is averaged over the workpiece in the same way as other roller pressure.
Hertz cylinder-contact reference · Elastic half-space reference
References
- Bonded elastic-layer Airy formulation
- Greenwood & Barber: finite-layer contact
- Bower: B-bar finite elements and volumetric locking