Catheter Analysis tab

The Analysis tab reports the predicted static properties of each section once the model is built. Until you build, it shows a short "build the model first" state with a button that takes you to Catheter Setup.

Sections are read one at a time. Pick one from the Sections list in the left rail and its KPI cards fill the page, with that section's peel-away and cross-section drawings beside them. The catheter's colour bar runs down the outer margin, proximal at the top, and clicking a band jumps to that section. Figures that belong to the whole catheter rather than to one section sit in the Catheter Total card under the picker. ↻ Recalculate Analysis in the header re-runs the numbers without rebuilding the model.

At a glance

KPI	What it tells you	Section below
Tensile Failure Load (First Yield)	Axial pull at which the first material reaches its tensile strength: a conservative first-yield onset, not the higher ultimate rupture load.	Failure Mode Analysis
Torque Failure	Applied torque at which the first material reaches its shear capacity.	Failure Mode Analysis
Min. Bend Radius (first yield)	Core sections: bend radius at which the core polymer first yields.	Failure Mode Analysis
Yield Moment (first yield)	Core sections: the bending moment at that first-yield radius.	Failure Mode Analysis
Burst Pressure	Internal fluid pressure at which the wall ruptures.	Failure Mode Analysis
External Crush Pressure	External pressure at which the structure collapses inward.	Failure Mode Analysis
First Failure Mandrel	Simulated: largest mandrel the section can be wrapped on before it takes permanent damage.	Kink Radius
Governing Mode	Simulated: which permanent event produced the first-failure figure (the ISO kink, or a named layer creasing).	Kink Radius
Collapse Onset Mandrel	Simulated: the mandrel at which the bending moment peaks, the onset of collapse.	Kink Radius
Collapse Mode	Simulated: how the section ends when bent tighter: moment peak, snap-through, lumen closure, or not applicable.	Kink Radius
50 % Lumen Loss Mandrel	Simulated: the mandrel at which the lumen has lost half its area.	Kink Radius
Snap-Through Mandrel	Simulated: the tightest mandrel at which the section still holds a stable shape.	Kink Radius
Bending Stiffness (EI)	Resistance to bending. Drives trackability and tip behavior.	Stiffness Properties
Bending Stiffness (EIx / EIy)	Anisotropic sections: the device-axis bending pair, in place of the single EI.	Stiffness Properties
Torsional Stiffness (GJ)	Resistance to twisting.	Stiffness Properties
Axial Stiffness (EA)	Resistance to stretching/compression along the axis.	Stiffness Properties
Axial Compliance (L/EA)	How far a section stretches or compresses per unit axial load. Sums over sections to a catheter total.	Stiffness Properties
Torsional Compliance (L/GJ)	How far a section twists per milli-newton-metre of torque. Sums over sections to a catheter total.	Stiffness Properties
Linear Density	Mass per unit length.	Stiffness Properties
Braid / Coil characteristics	Angle, pitch, coverage, fill factor and wire length, per reinforced layer.	Reinforcement Characteristics
Total / Articulating Length, Total Mass	Whole-catheter dimensions, and how much of the shaft the pullwires actually articulate.	Catheter Total
Stiffness Transitions	The EI step between each pair of adjacent sections.	Catheter Total

Units adapt to the global Metric/Imperial setting (see Menu Bar > Units). See Model accuracy for typical accuracy by regime.

Failure Mode Analysis

Kink / lumen collapse

Kink and collapse are not predicted by a closed form here: a single number cannot see the bend direction, the pull-wire lumens, a guidewire in the bore, or which layer creases first. They are simulated instead by the Kink Radius tab, which publishes its results to the Kink Radius card below.

• Tensile Failure Load (First Yield): The axial pulling force at which the first material in the section is predicted to reach its tensile strength. This is a conservative first-yield onset (the load at which the section begins to fail), not the ultimate rupture load, which is higher because ductile wires keep carrying load past first yield.
• Torque Failure: The applied torque at which the first material in any layer is predicted to reach its shear capacity.
• Min. Bend Radius (first yield) and Yield Moment (first yield): shown for multi-lumen core sections only, where a solid shaped core replaces the round bore these pressure limits assume.

Buckling / pushability

Column buckling is not reported as a per-section number here: a single Euler load says little about a real push, where the free length, the tip's end condition and vessel support change the answer by an order of magnitude. Use the Pushability tab for the push-force / buckling curve of the free distal length under the end conditions, vessel support, and friction you choose.

• Burst Pressure (First Yield): The internal fluid pressure at which the first material in the wall is predicted to reach its tensile strength in hoop. This is a conservative first-yield onset, not the ultimate rupture pressure, which is higher because the polymer keeps carrying pressure after the reinforcement wires give way. It is the same model as the tensile limit, applied around the circumference instead of along the axis, and the projection inverts between them: a near-circumferential coil governs burst even though it never governs in tension. Hover the row to see which material and layer set the limit. No bench anchor; confirm by physical testing before relying on it.
• External Crush Pressure: The maximum external pressure the section can withstand before its structure collapses inward. For coil-reinforced sections this is computed as the more conservative of two mechanisms (polymer-only elastic ring collapse, polymer matrix yield in hoop compression).

Kink Radius

This section is the one part of the tab that is not produced by the build. It is filled in by the Kink Radius tab, which bends the section's real cross-section step by step, and it reports what that run measured.

The tool runs one section at a time, so after a run that section shows its numbers while the others still read Not run. Three different blanks appear on these rows, and they are three different facts:

• Not run: nobody has simulated this section yet. The only one of the three with an action behind it.
• Not reached: the section was simulated and this event never happened on the bend ramp. That is an answer, not a gap.
• --.--: the tab's marker for "computed, not applicable here". On these rows it means the section can never be meshed at all, however many times the tool is run: a manual-stiffness section has no layup, and a rigid section is not in the flexible model.

Rebuilding the model clears these rows: the events were measured on the previous cross-section, so re-run the sections you care about.

Each event is one row, given as the mandrel a bench wrap would use: mandrel = 2R − OD, the pin, because that is what a bench test measures directly. A mandrel depends on the section's OD, so it does not compare between sections of different diameter; each row's hover says so, and the Kink Radius tab prints the centerline radius beside every event, which does compare. The rows sit in the same order as that tab's results.

• First Failure Mandrel: The largest mandrel this section can be wrapped on before it takes PERMANENT damage: the earlier of 50 % lumen loss and the first layer reaching its crease strain. This is the number to design to, and the one a mandrel-wrap test measures directly. Wrapped on anything larger nothing has yielded; tighter, something is permanently deformed.
• Governing Mode: WHICH permanent event produced the First Failure radius above, named rather than left to be inferred. The distinction is the point: a section whose lumen halves and one whose jacket creases both report a first-failure radius, and they call for different design changes. When a crease governs, the layer that went first is named. None reached means the ramp finished with no permanent damage at all: a result, and a good one, not a missing measurement. Hover the row for the per-layer crease ordering: each layer that creased and the bend it creased at, in the order the bend meets them.
• Collapse Onset Mandrel: The mandrel at which the section stops getting harder to bend and starts getting easier: the peak of its moment-curvature curve. It is a criterion, not a mechanism: on a round tube it is classical Brazier collapse (the bore flattens); on a multi-lumen core the same peak comes from whatever gives first: the webs between lumens folding, a lumen flattening. Nothing has yielded at the peak itself, but the section is losing stiffness from here on and bending past it may damage it. Blank when the moment was still rising where the model stopped: there is no peak to report, and the row's hover says so and gives the bend it stopped at.
• Collapse Mode: HOW this section ends when it is bent tighter and tighter, which a blank Collapse Onset row cannot tell you on its own. A moment peak is the best-converged answer. Snap-through means the run snapped without ever peaking, so the snap becomes the onset, a much wider error band. Lumen closure means it ovalises shut with no peak and no snap, which is a real answer: this section does not kink, it closes. A solid multi-lumen core reports Not applicable, because it has no bore to ovalise into a limit point and its real failure mode is material strain. Not determined means the bend ramp ended before any of those happened: the only one of them that means "we did not measure it".
• 50 % Lumen Loss Mandrel: The mandrel at which the lumen has lost 50 % of its undeformed cross-sectional area: the ISO 25539-2 / EN 13868 definition of a kink.
• Snap-Through Mandrel: The tightest mandrel at which the section still holds a stable shape. Past it there is no shape it can settle into: it snaps, and the bore closes. This is not the 50 % lumen loss above it: the lumen is often still well open here, and the ISO kink may never be reached at all. What ends here is the section's stability, not its lumen. The model carries no self-contact between the bore walls, so read this as the end of what was solved, and as a bound on anything tighter: an event reported as Not reached may simply lie past it.

Reinforcement wire buckling is not reported here

The Kink Radius tab also flags braid or coil wires snaking sideways out of the wall, as a risk (Likely / Possible / Unlikely) with the bend it would start at. It stays on that page. The trigger load behind it is only known to within about 2–3×, so it is deliberately kept out of every alert and out of this card, where a bare radius sitting beside numbers offered for comparing designs would invite exactly the comparison it cannot support.

A Design Sweep with its per-section kink simulation enabled reports the same events as centerline radii, so a sweep surface and this page are describing the same measurements. They are not interchangeable numbers: the sweep solves a deliberately coarser screening preset (a 48-point section mesh against this tool's 96, twelve ramp steps against twenty), which is what buys it hundreds of design points instead of one. Where the two disagree, the Kink Radius tab is the better estimate. Mandrels have no sweep column at all: a mandrel depends on the OD, so it cannot be compared across designs of different diameter.

Stiffness Properties

• Bending Stiffness (EI): This value, also known as Flexural Rigidity, defines the catheter section's resistance to bending.
• Bending Stiffness (EIx / EIy): For anisotropic designs, the direction-dependent pair shown in place of the single EI (see Multi-lumen core sections).
• Torsional Stiffness (GJ): This value, also known as Torsional Rigidity, defines the catheter section's resistance to twisting.
• Axial Stiffness (EA): This value represents the resistance to stretching and compression along the axis.
• Axial Compliance (L/EA): How far a section stretches or compresses per unit of axial load: its length divided by its axial stiffness. The reciprocal view of EA, and the one that adds up: sections load in series, so the per-section values sum to the Catheter Total row for it.
• Torsional Compliance (L/GJ): How far a section twists per milli-newton-metre of applied torque: its length divided by its torsional stiffness. Sections twist in series, so these also sum to a Catheter Total. Useful for estimating how much handle rotation is absorbed by the shaft before the tip responds.
• Linear Density: This is the mass per unit length of the section.

Reinforcement Characteristics

Calculated for each reinforced layer in each catheter section. Braid layers report:

• Braid Angle: Wrap angle of the braid wire.
• Braid Pitch: The axial distance between successive wraps of the braid wire.
• Braid Coverage: The percentage of the catheter's surface area covered by the reinforcing wires.
• Braid Fill Factor: The volume fraction of the reinforced layer occupied by braid wire.
• Braid Total Wire Length: The total unspooled length of wire required to construct this specific layer for the current section length.
• Filars per Carrier: Wires running side by side within each carrier (a multi-filar or multi-end braid). They widen the band a carrier lays down, so coverage saturates sooner and the weave jams at a lower PPI.
• Axial Wires and Axial Coverage: on a triaxial braid, the number of straight axial wires and the share of the surface they cover, reported separately from the bias-wire coverage above.

Coil layers report Coil Angle, Coil Coverage, and Coil Total Wire Length.

Catheter Total

The card under the section picker holds the figures that belong to the catheter rather than to any one section:

• Total Length, and Articulating Length: the length distal of the pull-wire anchor, the part of the catheter the pull-wires actually articulate. Shown once pullwires are anchored.
• Total Mass, when every section's mass is known.
• Axial Compliance (L/EA) and Torsional Compliance (L/GJ) summed over the sections, since both add in series.
• Stiffness Transitions: one row per adjacent pair of sections, giving the ratio of their bending stiffness (EI). A large step concentrates curvature at the joint, which is where whipping and joint kinking start; the step is invisible while you read one section page at a time, which is why it is reported here. Where a section bends differently about its two axes, the ratio uses each section's stiffer axis and the row's hover says so.

Multi-lumen core sections

Sections built on a multi-lumen extruded core report a slightly different KPI set, because a solid shaped core is not a thin-walled round tube:

• Min. Bend Radius (first yield) and Yield Moment (first yield): the bend at which the core polymer first yields (onset of permanent set), the meaningful bend limit for a solid core. Conservative: it ignores stress concentration at the lumen webs.
• Bending Stiffness (EIx / EIy): anisotropic designs (shaped cores, ovals, pullwire-dominated tips with >1% anisotropy) show the device-axis bending pair in place of the single EI row (EIx resists deflection along X, EIy along Y), matching the independent X/Y stiffness the dynamic simulation uses. Isotropic sections within such a design read EIx = EIy = EI; fully isotropic designs show only the single EI row.
• Bending EI (min / max): the principal EI range (which can differ from the X/Y pair on rotated cores) is reported on the wizard's Review page and in the PDF/Excel reports.
• Burst Pressure and External Crush Pressure show N/A: those formulas assume a single round bore. The Kink Radius tab meshes the core itself (its lumens, webs and septa) and is the tool for a core section's bend limit.

Model accuracy

The stiffness values shown above (EA, EI, GJ) and the derived failure-mode KPIs come from the composite-mechanics model. Accuracy is regime-dependent: typically within ~10–15% on common designs, wider on densely-packed braids at extreme angles. Errors are systematic rather than random, so relative comparisons between similar designs remain reliable even when absolute accuracy is wider.

See Model Accuracy for the full regime guidance, including which KPIs share these accuracy characteristics, how A/B-style design comparisons stay useful in lower-accuracy regimes, and how variation in material properties versus the Materials Library defaults affects predictions.

Related pages

• Catheter Setup Tab: where braid coverage, angle, pattern, and polymer choice are defined.
• Kink Radius: the simulation that fills in the bend limits above.
• Pushability: the push-force and buckling curve that replaced the per-section Euler load.
• Simulation Readouts: runtime metrics (bending moment, bend radius) that reference the same EI used here.
• Model Accuracy: calculator + simulator accuracy characterization, with verification report PDFs.