Testing Methods and Quality Control
How engineers test parts and keep them within tolerance: destructive and non-destructive testing, quality control, and the gauges and inspection used to check that each part meets the standard.
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Checking the work
Engineers cannot just hope a part is good enough. They test materials and parts, and they check finished parts against a standard. This module looks at destructive and non-destructive testing, at quality control, and at how tolerance sets the range of sizes a part is allowed to be.
Testing words
Learn these four terms before you study testing and quality control.
Destructive vs non-destructive
The big difference is whether the part survives the test.
Ask one question first
When you meet a test, ask one thing: does the part survive it? If the part is destroyed, it is destructive testing and only a sample can be tested. If the part survives, it is non-destructive and every part can be checked. Keep both apart from quality control, which checks that each finished part sits within tolerance.
Match the test
- impact test
- hardness test
- dye penetrant test
- ultrasonic test
- strikes a sample to see what force breaks it
- presses into the surface to measure how hard it is
- reveals cracks that reach the surface
- uses sound waves to find flaws inside a part
Match the limit
- tolerance
- upper limit
- lower limit
- go and no-go gauge
- the gap between the largest and smallest allowed size
- the biggest size a part is allowed to be
- the smallest size a part is allowed to be
- a tool that checks a size is within its limits
Spot the non-destructive test
Which of these is a non-destructive test?
- An X-ray of a weld to look for hidden cracks.
- Pulling a bar in a machine until it snaps.
- Striking a sample until it breaks.
- Bending a sample until it cracks.
Pick the destructive tests
Select the TWO tests that destroy the sample.
- An impact test that breaks a sample.
- A hardness test that dents the surface.
- A dye penetrant check of the surface.
- An ultrasonic scan for inside flaws.
Quality control steps
Put the steps of a quality control check in order, earliest first.
- Set the required size and tolerance
- Make the part
- Measure or gauge the finished part
- Accept the part or reject it as out of tolerance
Complete the rules
A test that destroys the sample is called _____ testing. A test that leaves the part usable is called _____ testing. The allowed range between the upper and lower limit is the _____. Checking that each made part meets the standard is called quality _____. A go and no-go _____ is used to check a size quickly.
Work out the tolerance
A shaft has an upper limit of 52 millimetres and a lower limit of 48 millimetres. The tolerance is the upper limit minus the lower limit. What is the tolerance in millimetres?
Find the non-destructive tests
Tap the TWO tests that leave the part usable.
- dye penetrant test
- X-ray inspection
- impact test
- hardness test
Name the check
Read each activity and choose which kind of check it is.
- A sample bar is pulled in a machine until it snaps in two
- An X-ray photo is taken of a weld to look for hidden cracks, and the part is then used
- Every finished bolt is passed through a go and no-go gauge to check its size
Explain the testing
Explain the difference between destructive and non-destructive testing, and explain why quality control matters in engineering.
- Explain what destructive testing is and give an example
- Explain what non-destructive testing is and give an example
- Explain why quality control and staying within tolerance matter