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The problem
Most mechanical failures are fatigue failures: parts break under repeated loads far below their static strength — valve springs, suspension springs, fasteners. The S-N curve that predicts fatigue life is measured on dedicated rigs that cycle specimens thousands of times, equipment most colleges cannot afford per batch. A benchtop spring fatigue tester fills this teaching gap: a motor drives a cam that compresses a coil spring once per revolution while a digital counter tracks every cycle, letting students run real fatigue trials and observe crack initiation, stiffness loss and permanent set. Running several springs at different deflections builds a classroom dataset that shows cycle life falling as stress amplitude rises — the core fatigue lesson, demonstrated on hardware instead of a blackboard.
Measures free length with a vernier caliper and inspects the spring.
Follow the working sequence
How it works
- A coil spring is seated between the rig's plates and the deflection is set via the cam and follower height.
- The starting free length is measured with a vernier caliper and recorded on the observation sheet.
- The motor is started at the controller-set speed; the cam compresses and releases the spring once per revolution.
- A limit switch on the follower fires each cycle and the digital counter increments on the LED display.
- At the target count the rig is stopped; free length is re-measured and the spring is inspected for cracks and permanent set.
- Repeating at several deflections shows how cycle life falls as stress amplitude rises — the fatigue lesson in the student's own data.
Tech stack:
- MS angle/plate frame fabrication
- Cam-and-follower mechanism
- DC gear motor with PWM speed controller
- Digital cycle-counter module with limit-switch trigger
- Test coil springs (sourced/fabricated)
- Vernier caliper for free-length measurement
| Parameter | Value |
|---|---|
| Drive | DC gear motor with PWM speed controller |
| Cycling | 1 compression-release per cam revolution (design) |
| Counter | Digital LED module, limit-switch triggered |
| Deflection | Adjustable via cam and follower height |
| Frame | MS angle and plate, fabricated |
| Measurement | Vernier caliper free-length checks, visual crack inspection |
| Test articles | Coil springs, multiple deflection levels |
Project features
- [Cam-and-follower cycling] A motor-driven cam compresses the coil spring once per revolution — simple, repeatable cyclic loading with no hydraulics.
- [Digital cycle counter] Every cycle is counted on an LED display, triggered by a limit switch on the follower, so long runs need no supervision.
- [Adjustable deflection] Cam selection and follower height set the spring deflection, letting students test at several stress amplitudes.
- [Speed-controlled motor] A PWM controller sets the cycling rate; students can trade test speed against observation comfort.
- [Rigid test frame] Fabricated MS frame keeps the spring, cam and follower aligned through thousands of cycles.
- [Observation sheets] The manual's sheets record free length, crack checks and stiffness before and after each run.
- [Classroom S-N dataset] The procedure is designed so a batch of students builds a shared deflection-vs-life dataset.
What is included
- Working spring fatigue testing machine
- Fabrication drawings (frame, cam, follower, spring seats)
- Wiring documentation (motor, controller, counter, limit switch)
- Experiment manual with observation sheets
- Set of test coil springs
- Project report PDF (fatigue theory, S-N concept, rig design)
- PPT presentation for final review
- Viva Q&A preparation document (fatigue, endurance limit, S-N curves, crack initiation)
Limitations & prerequisites
- Tests coil springs in compression cycling only — tension and bending fatigue need different fixtures.
- Cycle counts are comparative classroom data, not certified material qualification.
- Deflection settings are discrete (cam/follower positions), not continuously variable load control.
- No automatic crack detection — inspection is visual and manual.
Frequently Asked Questions
What does the counter actually count?
Complete compression-release cycles: a limit switch on the follower fires once per cam revolution and increments the digital display.
How long does a test take?
It depends on the target count and motor speed — the counter lets long runs proceed unattended, and the manual suggests count plans per deflection level.
What do students observe after a run?
Change in free length (permanent set), visible cracks, and stiffness change — all recorded on the observation sheets.
Can it test other parts?
The rig is built for coil springs; other geometries would need new seats and cams, documented as future scope.
Is this project suitable for a final-year project?
Yes — for Mechanical Engineering programs. It makes fatigue — usually a purely theoretical topic — into a hands-on experiment with real cycle data. Suitable for B.E./B.Tech final-year projects in Mechanical Engineering.
Components & software requirements
- MS angle/plate frame fabrication
- Cam-and-follower mechanism
- DC gear motor with PWM speed controller
- Digital cycle-counter module with limit-switch trigger
- Test coil springs (sourced/fabricated)
- Vernier caliper for free-length measurement
Delivery information
Built-to-order project. Delivery timeline is shared after order confirmation based on current queue.
Support terms
Complete documentation, setup guide, and viva preparation included. Support for setup and explanation provided.
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