Why Engineers Shake, Freeze, Cook, Drop and Drown Perfectly Good Products
A new product rolls out of engineering.
It works.
It looks good.
The software behaves.
The electronics power up.
The enclosure closes properly.
The prototype has probably already cost more money than anyone wants to discuss.
So what happens next?
An engineer may:
shake it,
freeze it,
cook it,
drop it,
spray it with water,
submerge it,
put it in a vacuum,
hit it with electromagnetic interference,
or combine several of those things at once.
Sometimes the test continues until something breaks.
This can look like a truly terrible way to treat something everybody just worked very hard to build.
But there is a reason.
The real world is going to abuse the product eventually.
Engineers would rather get there first.
That is the basic idea behind environmental testing, reliability testing and much of Verification & Test.
The goal is not destruction for entertainment.
Although occasionally the videos are excellent.
The goal is to find out what happens to a product before customers, weather, gravity, vibration, heat, water or physics get the opportunity to answer for us.
Verification Begins With an Annoying Question
Engineers design products based on requirements.
The car should operate in winter.
The aircraft electronics should survive vibration.
The marine display should resist water.
The industrial controller should tolerate heat.
The package should protect the equipment during shipping.
The satellite should survive launch.
Wonderful.
Now somebody has to ask:
How do we know?
That question is the beginning of Verification & Test.
A design requirement is a statement.
Testing produces evidence.
Sometimes the evidence comes from software.
Sometimes from analysis.
Sometimes from inspection.
And sometimes the most convincing evidence comes from taking the physical product into a laboratory and deliberately exposing it to the conditions it is expected to survive.
First, Shake It
Vibration is everywhere.
Cars vibrate.
Aircraft vibrate.
Ships vibrate.
Machines vibrate.
Construction equipment vibrates.
Rockets vibrate spectacularly.
And products mounted inside those systems have to continue working.
So engineers use vibration test systems — commonly called shakers or shaker tables — to reproduce mechanical environments.
A test article may be fitted with accelerometers and other sensors.
Then engineers apply controlled vibration while monitoring what the product does.
They are looking for problems such as:
- loose fasteners
- cracked solder joints
- connector failures
- fatigued wires
- structural resonances
- circuit board flex
- broken mounts
- intermittent electrical connections
IEC’s 60068 family of environmental test standards includes methods addressing environmental stresses such as vibration, shock, temperature and other conditions, while MIL-STD-810 uses a tailored environmental-engineering approach based on the actual stresses equipment is expected to experience during its service life. (quicksearch.dla.mil)
And sometimes the most interesting vibration failure occurs because something resonates.
A relatively small vibration input can produce a much larger response when the frequency happens to line up with a natural frequency of the product or structure.
Suddenly the enclosure is not merely vibrating.
It is enthusiastically participating.
Then Freeze It
A product that works perfectly on a comfortable engineering bench may behave very differently at -20°C.
Or -40°C.
Or colder.
Cold changes materials.
Plastics can become stiffer.
Seals can harden.
Lubricants become more viscous.
Batteries lose performance.
Dimensions change.
Electrical characteristics shift.
A connector that works beautifully at room temperature may become marginal when cold.
A display may slow.
A motor may draw more current.
A sensor may drift.
So engineers place products into environmental chambers and reduce the temperature.
Sometimes the product is powered.
Sometimes it is not.
Sometimes it is cold-soaked for hours before anybody even tries to turn it on.
Because one of the important questions may be:
Does it work cold?
But another may be:
Can it start cold?
Those are not necessarily the same thing.
Now Cook It
Go in the other direction.
Heat causes its own collection of trouble.
Electronics generate heat.
Engines generate heat.
Sunlight creates heat.
Industrial environments create heat.
And many failure mechanisms accelerate as temperature rises.
Engineers may test whether:
- electronics remain within limits
- cooling systems work
- adhesives remain attached
- seals stay functional
- insulation survives
- sensors remain accurate
- materials maintain strength
- batteries remain safe
Sometimes engineers are verifying a defined high-temperature requirement.
Other times they deliberately go beyond expected conditions to expose weaknesses.
That begins moving us toward reliability testing and HALT.
But before we get there, engineers may do something even more annoying.
They heat the product.
Then freeze it.
Then heat it again.
Then freeze it again.
Thermal Cycling Makes Materials Argue With Each Other
Almost every material changes dimensions with temperature.
But different materials expand and contract by different amounts.
That means a product made from:
metal,
plastic,
solder,
silicon,
rubber,
ceramic,
adhesive,
and fiberglass
contains a large collection of materials that repeatedly disagree about how big they should be.
One thermal cycle may do very little.
Hundreds or thousands can produce fatigue.
Solder joints crack.
Adhesives weaken.
Connectors shift.
Seals change compression.
Circuit boards flex.
Interfaces delaminate.
A product that survives both a hot test and a cold test may still fail after repeated transitions between the two.
That is why thermal cycling exists.
And it teaches one of the recurring lessons in Verification & Test:
The transition can be as important as the extreme.
Then Drop It
Gravity also contributes generously to engineering problems.
People drop products.
Packages fall.
Tools tumble.
Equipment gets knocked over.
Electronics slip off dashboards.
Shipping systems are not always gentle.
So engineers deliberately drop things.
A professional drop test is not simply:
Lift it up and let go.
Engineers control:
- drop height
- orientation
- impact surface
- number of drops
- product state
- instrumentation
- acceptance criteria
A product may be dropped onto:
a face,
an edge,
or a corner.
And that distinction matters.
Corner impacts can concentrate loads dramatically.
ISTA packaging procedures use controlled drop, vibration, impact, compression and atmospheric-conditioning tests to reproduce the damage-producing environments packages can encounter during transportation. (ista.org)
The package may look battered afterward.
That does not necessarily mean it failed.
Sometimes the box is supposed to sacrifice itself.
The important thing is that the expensive product inside survives.
Your Fifth-Grade Egg Drop Was Engineering
You may already understand this better than you think.
Remember the school egg-drop project?
Protect an egg.
Drop it from somewhere alarmingly high.
See whether it survives.
You had:
a requirement,
a fragile payload,
a design,
materials,
a physical test,
and a brutally clear pass/fail result.
Egg intact.
Or:
Splat.
Nobody may have mentioned that engineers do more sophisticated versions of the same experiment for a living.
The materials get more expensive.
The instrumentation gets better.
The reports get much longer.
But the fundamental question is familiar:
We think our design will protect it. How do we prove it?
Then Drown It
Water is exceptionally good at locating the one opening engineers hoped it would never find.
So engineers help.
They drip water onto products.
Spray them.
Blast them with water jets.
Submerge them.
Leave them underwater.
Then inspect.
Ingress testing evaluates whether enclosures protect equipment against water, dust and other foreign material.
The familiar IP ratings describe defined levels of protection.
But an IP rating is not simply a generic statement that something is “waterproof.”
Different tests represent different exposure conditions.
Rain is not the same as a water jet.
A water jet is not the same as immersion.
Immersion is not necessarily the same as high-pressure hot-water cleaning.
A product may survive one beautifully and fail another.
And even when an enclosure is carefully designed, the final result may depend on a surprisingly small component:
a gasket,
a cable gland,
a connector seal,
a screw,
an O-ring.
You can spend millions designing sophisticated electronics.
Then lose the whole argument to a $4 fitting.
Engineering is humbling that way.
Put It in a Vacuum
For aerospace and space systems, the environment gets stranger.
Spacecraft operate where atmospheric pressure is extremely low.
Temperature control behaves differently.
There is no normal convective cooling.
Materials can behave differently.
Electronics have to keep functioning.
So engineers use thermal-vacuum chambers, often shortened to TVAC, to reproduce combinations of low pressure and temperature.
The spacecraft or component may sit inside a large chamber surrounded by instrumentation while engineers monitor:
- temperatures
- electrical performance
- pressure
- communications
- subsystem operation
It is another example of taking something that worked perfectly well in a normal laboratory and asking:
Fine. But does it still work somewhere that looks nothing like the laboratory?
Blast It With Electromagnetic Interference
Some environmental threats are invisible.
Modern products live surrounded by:
radios,
motors,
antennas,
high-voltage systems,
power electronics,
chargers,
wireless networks,
radar,
and other electronic systems.
An electronic product must often satisfy two broad EMC questions:
Does it create unacceptable electromagnetic interference?
and:
Can it continue functioning when electromagnetic interference exists around it?
EMI/EMC engineers use specialized chambers, antennas, amplifiers, receivers and instrumentation to investigate those questions.
Compared with a crash test, it may not look exciting.
Until switching on one system causes another system to do something very unexpected.
Then excitement arrives quickly.
Sometimes One Test Is Not Enough
Suppose the product passes:
the heat test,
the vibration test,
and the humidity test.
Congratulations.
Now expose it to:
heat + vibration + humidity.
Something fails.
Why?
Because environmental stresses can interact.
Heat changes material stiffness.
Then vibration acts on the altered material.
Cold changes seal behavior.
Then water finds a gap.
Vibration creates a microscopic crack.
Then thermal cycling makes it grow.
Humidity enters.
Corrosion begins.
This is why engineers perform combined environmental testing.
MIL-STD-810 specifically emphasizes tailoring environmental tests to realistic service-life conditions rather than blindly applying one universal set of stresses. (quicksearch.dla.mil)
The real world does not have separate test chambers.
A product experiences one world.
Sometimes Sequence Matters Too
Not all combined testing happens simultaneously.
Sometimes engineers deliberately expose a product to stresses in sequence.
For example:
Thermal cycling → vibration → ingress testing
Why?
Maybe thermal cycling stresses the seals.
Vibration loosens something slightly.
Then the water test reveals the weakness.
Reverse the order and the product may pass everything.
The same individual tests.
Different sequence.
Different result.
Environmental damage can accumulate.
This makes the test plan itself part of the engineering problem.
Then Push It Beyond the Specification
Up to this point, many tests may simply verify requirements.
The requirement says:
survive 10 g of vibration.
The product survives.
Pass.
The requirement says:
operate to 60°C.
It operates.
Pass.
The requirement says:
survive a one-meter drop.
It survives.
Pass.
But an engineer may still ask:
How much farther could we go?
This is the distinction between testing to specification and testing toward failure.
A spec test asks:
Does it meet the requirement?
Failure testing asks:
Where is the limit?
A product required to survive 60°C that fails at 62°C technically passed.
So did one that works until 95°C.
But those two designs do not have the same margin.
Testing beyond the requirement can reveal that difference.
Sometimes Engineers Actually Want Something to Fail
This sounds backwards.
Usually a failed test is bad.
But failure can be enormously valuable during development.
Suppose a prototype fails during vibration.
Engineers investigate.
A connector mount is weak.
They redesign it.
Test again.
Now something else becomes the weakest point.
Fix that.
Test again.
Development testing becomes a process of discovering and removing weaknesses.
The worst outcome is not necessarily:
The prototype failed.
The worst outcome may be:
The prototype contained the weakness, and our test failed to find it.
Because then the customer gets the discovery instead.
HALT Takes That Philosophy Seriously
HALT — Highly Accelerated Life Testing — deliberately exposes products to increasing stresses beyond normal expected use to reveal failure modes and design weaknesses quickly.
Typical HALT stresses can include:
- extreme high and low temperatures
- rapid thermal transitions
- repetitive-shock vibration
- combined temperature and vibration
ESPEC describes HALT as a step-stress approach that deliberately goes beyond normal use so failure modes can be detected and corrected. (espec.com)
HALT is not simply:
Did it pass?
It asks:
Where does normal operation end?
Where does damage begin?
What fails first?
What can we improve?
That makes finding a meaningful failure potentially a successful HALT result.
And HASS Tries to Catch Manufacturing Problems
Once the design is mature, a different problem emerges.
Production.
Manufacturing introduces variation.
A soldering process drifts.
A supplier changes.
A fastener is under-torqued.
A connector is installed badly.
An adhesive application varies.
HASS — Highly Accelerated Stress Screening — uses accelerated stresses at controlled levels to help expose manufacturing defects before production units reach customers.
ESPEC distinguishes the roles neatly: HALT is used to find weaknesses in the design, while HASS is used as a production screen to detect process deviations and defective units. (espec.com)
Or, in slightly less formal language:
HALT asks: What did we design wrong?
HASS asks: What did we build wrong?
Testing Is Not Just About Hardware
Verification & Test also extends deep into software and electronics.
Modern products may use:
- model-in-the-loop testing
- software-in-the-loop testing
- hardware-in-the-loop testing
- automated software verification
- formal verification
- test automation
A hardware-in-the-loop, or HIL, system can connect a real controller to a simulated environment.
An automotive ECU can be made to believe it is controlling a real vehicle before that vehicle even exists.
Engineers can simulate:
sensor failures,
voltage problems,
dangerous operating conditions,
driver inputs,
fault combinations.
That allows testing of conditions engineers would rather not reproduce with an actual car and an actual human.
Sometimes the best way to test reality is to make the hardware believe the simulation is reality.
Simulation Is Not the Enemy of Testing
There is a temptation to frame engineering as:
Simulation versus physical testing.
That is usually the wrong argument.
Simulation lets engineers explore enormous numbers of conditions quickly.
Physical testing shows what real hardware actually does.
The two inform each other.
A simulation predicts a structural load.
A physical test measures it.
If they agree:
confidence increases.
If they disagree:
something interesting has been discovered.
Maybe:
the model is wrong,
the material properties were wrong,
the boundary conditions were wrong,
the prototype differs from the design,
or the test itself is wrong.
That feedback loop makes both methods better:
Simulate → Build → Test → Compare → Learn → Improve
Verification Is Not the Same as Validation
Another pair of engineering words frequently gets mixed together.
Verification generally asks:
Did we build the product correctly according to the requirements?
Validation asks:
Did we build the right product for the intended use?
Imagine engineers design a rugged marine display.
It passes vibration.
Ingress.
Temperature.
Electrical verification.
Perfect.
Then actual boat operators try it and discover the interface is impossible to read in bright sunlight while standing at the helm.
The product may have been beautifully verified against its technical requirements.
It may still have a validation problem.
Both questions matter.
Why Do Engineers Test Things Customers Will Never Do?
Some laboratory tests look absurdly severe.
Why would anybody subject a product to conditions no normal customer would intentionally create?
Several reasons.
First, engineers need margin.
Real environments vary.
Manufacturing varies.
Products age.
Customers improvise.
Second, accelerated testing can reveal slow weaknesses faster.
Waiting ten years to discover whether something lasts ten years is inconvenient.
Third, harsh tests can expose failure mechanisms that would otherwise appear only after thousands of normal cycles.
But there is an important limit.
Testing harder is not automatically better.
Push far enough and eventually you create failures that have nothing to do with real service.
A useful test should answer an engineering question.
Random destruction answers mostly:
How expensive was that noise?
How Much Abuse Is Enough?
This is one of the hardest questions in testing.
At what point do engineers stop?
More testing always sounds safer.
But more testing costs:
money,
hardware,
time,
laboratory capacity,
engineering resources,
schedule.
And some tests destroy the product.
Eventually teams must decide whether they have enough evidence.
That decision may depend on:
- product risk
- consequence of failure
- applicable standards
- regulatory requirements
- customer requirements
- design margin
- statistical confidence
- available prototypes
- cost
- schedule
A decorative consumer device does not necessarily need the same evidence as:
a flight-control computer,
a medical device,
or a pressure vessel.
Verification should be proportional to risk.
The Test Setup Can Be Wrong Too
Here is another uncomfortable truth.
Sometimes the product did not fail.
The test failed.
The fixture was wrong.
The sensor loosened.
The chamber temperature was not the product temperature.
The shaker input did not reach the test article correctly.
A cable broke.
The data-acquisition system clipped the signal.
The mounting condition was unrealistic.
Test engineers have to question the experiment itself.
This is why Verification & Test is not merely operating equipment.
It requires experimental design.
Measurement.
Instrumentation.
Physics.
Statistics.
Troubleshooting.
And a healthy suspicion of suspiciously convenient results.
Passing Is Not Always the Most Valuable Result
A qualification engineer wants a pass.
A reliability engineer may want information.
A development engineer may want a failure.
A manufacturing engineer may want to know why one unit behaves differently from another.
The word test hides many different objectives.
That is why a result saying:
PASS
may tell you everything you needed to know.
Or almost nothing.
The value depends on the question the test was designed to answer.
Customers Are Terrible Test Engineers
Customers perform environmental testing constantly.
Unfortunately, they rarely document it properly.
They:
leave electronics in hot cars.
Drop products.
Operate machinery in cold weather.
Spray equipment.
Ignore maintenance.
Overload things.
Use devices near interference sources.
Store products improperly.
Combine environmental stresses.
Then customer support receives the test report:
It stopped working.
No temperature history.
No accelerometer data.
No high-speed video.
No calibrated sensors.
No synchronized logs.
This is why engineers want failures to happen in the laboratory first.
The lab is controlled.
Instrumented.
Observable.
Repeatable.
And the engineering team can actually inspect what happened.
Finding a Failure Early Can Be Incredibly Cheap
Suppose testing reveals that a product leaks because a fastener is positioned slightly too far from one corner.
Engineering changes the CAD model.
Moves the fastener.
Builds another prototype.
Problem solved.
Now imagine discovering the same problem after:
tooling is complete,
suppliers are contracted,
50,000 units are manufactured,
products are shipped worldwide.
The engineering change may still be tiny.
The business problem is not.
This is the financial case for Verification & Test.
The test chamber may look expensive.
Field failure can make it look extremely cheap.
Environmental Testing Is Really About Confidence
No amount of testing can prove that a product will never fail.
Eventually something will.
Materials age.
Conditions exceed expectations.
Unexpected combinations occur.
Manufacturing defects slip through.
Customers become inventive.
Verification does something more realistic.
It builds evidence.
Each successful analysis or test removes some uncertainty.
The team learns:
how the product behaves,
where its margins are,
what failure modes exist,
what conditions matter,
and whether the requirements have been satisfied.
Eventually the evidence becomes strong enough to support a decision:
Ship it.
Install it.
Certify it.
Or in the case of a rocket:
Launch it.
Verification does not create certainty.
It creates justified confidence.
Why Engineers Seem So Mean to Perfectly Good Products
Viewed from outside an engineering laboratory, the behavior can look strange.
Someone built this thing carefully.
Now another group is deliberately trying to hurt it.
But the test engineer is not the product’s enemy.
Quite the opposite.
They are giving it an opportunity to fail somewhere safe.
Before production.
Before installation.
Before launch.
Before a warranty claim.
Before an accident.
Before the customer discovers the weakness.
The lab is where engineering gets to ask uncomfortable questions while the answers are still relatively cheap.
What Happens After Something Breaks?
This is the part outsiders often miss.
The test does not end when something breaks.
That may be when the real work begins.
Engineers investigate.
They review:
- sensor data
- temperature history
- vibration traces
- high-speed video
- electrical measurements
- software logs
- physical damage
- simulation results
They may use:
microscopy,
X-ray,
CT scanning,
materials analysis,
teardown,
additional testing.
Then they ask:
What actually caused the failure?
Not:
What broke first?
Those can be different questions.
A cracked component may only be the final visible consequence of a chain that started somewhere else.
Root-cause analysis turns failure into engineering knowledge.
Then They Do It Again
This is perhaps the simplest summary of product development.
Design.
Build.
Test.
Fail.
Investigate.
Improve.
Test again.
Eventually:
Pass.
Then someone changes something.
A supplier.
A material.
A process.
A component.
A requirement.
And testing begins again.
There is a reason Verification & Test never really disappears from engineering.
Products evolve.
Environments change.
Requirements change.
And reality remains stubbornly interested in finding weaknesses.
Why This Is Also a Fascinating Engineering Career
There is another reason we have spent so much time on these tests.
Someone gets paid to do all of this.
There are careers where engineers:
run vibration shakers,
operate environmental chambers,
instrument prototypes,
program test automation,
perform HIL testing,
conduct crash tests,
analyze failures,
run thermal-vacuum chambers,
perform EMI/EMC testing,
design test fixtures,
and yes —
drown electronics.
If what attracts you to engineering is the idea of:
working with physical hardware,
pushing machines toward their limits,
collecting data,
solving mysteries,
and figuring out why things break,
Verification & Test may be a career worth exploring.
You may even have started preparing in elementary school.
Remember the egg drop?
Engineering Is Not About Preventing Every Failure
That sounds strange, but it matters.
You cannot design every product to survive everything.
A phone does not need to survive the bottom of the Mariana Trench.
A coffee maker does not need spacecraft-level vibration qualification.
A shipping box does not need to survive reentry.
Engineering is about designing appropriately for the intended use.
That means test requirements need to reflect reality.
MIL-STD-810 makes this point explicitly: its methods are not meant to be universal design specifications; the environmental conditions and tests should be tailored to the equipment’s realistic service-life environment. (quicksearch.dla.mil)
In other words:
Do not simply ask:
How hard can we test it?
Ask:
What does this product genuinely need to survive?
The Ultimate Verification Question
Everything in this field eventually comes back to one deceptively simple question:
How do we know?
How do we know the aircraft component will survive?
Test it.
How do we know the enclosure will stay dry?
Test it.
How do we know the electronics work when frozen?
Test them.
How do we know the package protects the product?
Drop it.
How do we know the simulation reflects reality?
Measure reality.
How do we know the rocket is ready?
Test the pieces.
Test the systems.
Test them together.
Then decide whether the evidence is strong enough to proceed.
That is Verification & Test.
It is not a department whose job is to make life difficult for design engineers.
Although occasionally it may feel that way.
It is the part of engineering that turns:
We think it will work
into:
Here is the evidence.
The Bottom Line
Engineers deliberately abuse perfectly good products because the physical world eventually will too.
So they:
shake them
to find loose connections, resonances and structural weaknesses.
freeze them
to expose cold-temperature problems.
cook them
to find heat-related limits.
cycle them between hot and cold
to make materials repeatedly expand and contract.
drop them
to understand shock and impact.
drown them
to find weak seals.
put them in vacuums
to reproduce aerospace environments.
blast them with electromagnetic interference
to see whether electronics continue behaving.
combine stresses
because the real world does not separate them neatly.
And sometimes:
keep pushing until something fails
because knowing where the boundary is can be more valuable than simply knowing the product passed.
All of this may look like engineers have developed an extremely elaborate profession around mistreating expensive hardware.
There is some truth to that.
But the reason is serious.
A failure in the laboratory can produce data.
A failure during development can produce a redesign.
A failure during qualification can prevent a dangerous launch.
A failure before production can save millions of dollars.
And a failure found by the engineer is almost always preferable to the same failure being discovered later by the customer.
So yes.
Engineers really do get paid to:
shake things,
freeze things,
cook things,
drop things,
crash things,
and drown things.
Not because they want products to fail.
Because eventually every important engineering design has to face the same final examiner:
the real world.
