Torsion Testing Machine

The Torsion Testing Machine Virtual Lab is a fully interactive simulator that lets you perform virtual torsion tests on solid and hollow round shafts. In a real laboratory, a torsion testing machine clamps the specimen between a fixed chuck and a rotating chuck, twisting it at a controlled angular speed while a torque cell records the moment required at each angle. This simulator reproduces that workflow, generating real-time torque-angle curves and calculating modulus of rigidity, shear yield strength, ultimate shear strength, modulus of rupture, and the angle at fracture.

The simulator includes thirteen built-in materials eight built-in materials — mild steel, aluminium 6061-T6, cast iron, copper, brass, high-carbon steel, stainless steel 304, and titanium Ti-6Al-4Vmdash; mild steel, aluminium 6061-T6, cast iron, copper, brass, high-carbon steel, stainless 304, Ti-6Al-4V, nickel, magnesium AZ31B, phosphor bronze, Inconel 718, and tool steel D2 — plus a "+ Custom" material builder with validated input. You can switch between solid and hollow shaft geometry, adjust outer diameter, inner diameter (hollow only), gauge length, and twist rate. A built-in SI / Imperial unit toggle switches all values between metric (N·m, MPa, mm) and US customary units (lbf·ft, psi, in). After the test, export results as CSV, PNG, or a full industrial-style PDF report.

When you first load the simulator you are in Simulate mode. The torsion machine canvas is on the left and the torque-twist graph is on the right. Below the graph you will find the action bar (Mount, Start, Reset, Solid/Hollow toggle, exports) and the controls panel (material, diameter, gauge length, twist rate).

To begin: (1) Select a material. (2) Choose Solid or Hollow geometry. (3) Adjust outer diameter, inner diameter (hollow only), and gauge length. (4) Set the twist rate. (5) Click Mount to clamp the specimen into the chucks. (6) Click Start to apply torque. The machine animation, digital readout, and torque-twist curve update live. When the specimen fractures, a snapping sound plays and the eight result cards reveal the measured properties.

Unit Toggle: Click SI or Imperial in the top bar — readouts, graph axes, badges, stepper labels, the report, and the custom material form all switch instantly.

Right-click menu: Right-click the graph canvas to copy the value at the cursor, save PNG, export CSV, toggle the grid, or reset.

The machine canvas shows a horizontal torsion testing machine: a motorised gearbox on the right turns the rotating chuck while the fixed chuck on the left holds a torque cell. The specimen is the round bar between them, with a twist indicator scale showing the angle of rotation. A cross-section A–A view in the top-right corner of the canvas shows the radial shear-stress gradient (zero at centre, maximum at outer fibre, labelled τ=0 and τmax) and a rotating reference line that tracks the live twist of the rear face against the fixed front face. As the test progresses, the specimen visibly twists, and on fracture the failure surface appears — either a transverse (90°) plane for ductile materials such as mild steel, or a helical (45°) plane for brittle materials such as cast iron. Right-click the machine canvas to toggle the dimension lines (L₀, d, dᵢ) on or off.

The graph canvas plots torque (N·m) versus angle of twist (degrees). Yield, ultimate, and fracture points are marked. After the test, eight result cards appear: modulus of rigidity, yield shear stress, ultimate shear stress, modulus of rupture, yield torque, max torque, angle at fracture, and polar moment of inertia J.

Explore mode is an illustrated reference covering four categories: Machine Parts (fixed chuck, rotating chuck, torque cell, gearbox, twist indicator), Formulas (polar moment of inertia, shear stress, angle of twist, modulus of rigidity), Standards (ASTM E143, ISO 7800), and Failure Modes (ductile transverse, brittle 45° helical, hollow shaft buckling). Each card includes a description, a key formula where applicable, and a worked numerical example.

Practice mode generates random torsion calculations: shear stress from torque and diameter, polar moment of inertia for solid or hollow shafts, modulus of rigidity from torque and twist, angle of twist from material and geometry. Type the answer, click Check, and use Show Solution for a step-by-step walkthrough.

Quiz mode delivers five mixed multiple-choice and numerical questions per session, scored with a star rating. Use it to gauge readiness before an exam.

• Start with mild steel as a solid shaft to see a clear elastic-plastic torque-angle curve with yield, plastic, and fracture regions.
• Compare ductile mild steel against brittle cast iron — note the dramatic difference in fracture surface (flat vs 45° helical).
• Switch to hollow geometry — for the same outer diameter, hollow shafts have a smaller J, so they need less torque to twist but reach the same surface shear stress at the outer fiber. This is why drive shafts are hollow: best stiffness-to-weight ratio.
• Use the diameter stepper to see how shear stress scales as 1/d³ — doubling the diameter cuts surface shear stress by 8× at the same torque.
• Increase the gauge length and observe how the angle of twist grows linearly with L for the same torque.
• Use Imperial mode to study US-standard ASTM E143 reporting (lbf·ft and psi).
• Click Export Report to generate a print-ready industrial torsion test certificate with specimen data, machine settings, results, the torque-twist curve, and signature lines.
• Right-click the graph to copy the torque/angle value at any cursor position, toggle the grid, or jump to other exports.
• Use the T – θ / τ – γ toggle above the graph to switch between the engineering view (Torque vs Angle) and the material-science view (Shear Stress vs Shear Strain). The τ-γ curve normalises away the geometry so two specimens of different size can be compared.
• After a test, click Reset to keep the previous curve as a faint ghost overlay behind your next run — perfect for A/B comparing two materials or solid vs hollow. Click Clear Ghost to remove it.
• Open the Learning panels below the graph: live equations (rendered as classical math with KaTeX), the cross-section stress distribution chart showing τ(r) across the radius, and the failure mode coach that explains why this material fractured the way it did.
• Click Show Calculation in the Test Control panel to open a step-by-step modal that derives J, G, τ_y, τ_u, the modulus of rupture, and the angle at fracture from the raw test data. Equations are rendered in proper math notation.
• The on-canvas cross-section A–A panel shades the radial shear-stress gradient (τ=0 at the centre, τ_max at the outer fibre) so you can see why hollow tubes work so well.