This actually happens a lot in real life.
We test the part in lab:
✓ Hardness → okay
✓ Chemistry → okay
✓ Tensile strength → okay
✓ Microstructure → looks fine
Still, part breaks in service. Cracks. Fails. ⛔
So what’s wrong?
Truth is… lab tests are done in ideal conditions.
But… real world is not ideal.
Let me explain..
* 1. Leftover (residual) stress inside part:
After processes like welding, machining, or heat treatment, some parts have hidden stress inside.
You can’t see it from outside, but over time, especially under repeated load → it can cause cracks.
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* 2. Heat treatment not done properly:
On paper, heat treatment looks okay. But maybe some area didn’t get heated enough… or cooled too fast.
That creates uneven structure, some areas become too soft, others too brittle.
That makes the part weak.
* 3. Tiny defects inside the part:
Some defects are deep inside the metal, small cracks, inclusions, or shrinkage, which normal testing may miss.
These grow slowly during use and finally cause failure.
* 4. Hydrogen problem:
If the part was welded or pickled, hydrogen can get trapped inside.
If not removed properly, it makes part brittle.
It may break after few days or weeks, even if it looked perfect earlier.
* 5. Actual working conditions are harsh:
In lab, we test in calm, clean conditions.
But in real life, parts face high temp, vibration, pressure changes, or corrosion.
If design didn’t consider these, failure can happen.
* 6. Sharp corners or rough surface:
Even a small notch or sharp edge can start a crack.
Stress builds up there, especially if load keeps repeating.
Over time, crack grows and causes failure.
* 7. Right part, but wrong material:
Sometimes we use material that looks okay but isn’t fit for the job or service (FFS).
Like using soft steel in high-pressure application. Or cast iron where shock load is present.
It may pass tests, but won’t survive in real conditions.
••••••••
So..
Passing tests in lab is good..
but that doesn’t mean it’s ready for real world.
That’s why failure analysis is important. 🔬
It tells us what really happened, and how to stop it next time.
Sometimes..
1 real-life failure teaches more than 10 lab reports.
Let’s talk in the comments.
Your experience can help someone else.😊
