Vibration testing reproduces the loads generated by road irregularities, engine operation and component resonance while the vehicle is driving, verifying structural integrity and functional stability under vibration. It is one of the tests closest to real use and the most likely to expose design weaknesses.
Test types
Sine vibration: a single frequency or a swept sine, used to examine resonance response at particular frequencies; mostly for component-level screening.
Random vibration: multiple frequency components applied simultaneously per a power spectral density (PSD) curve. This is closest to real road excitation and is the mainstream automotive method.
Combined vibration and temperature cycling: temperature and vibration applied together, reproducing driving conditions in extreme climates at higher severity.
The three inputs to severity
Mounting location sets the vibration level. A part on a body structure and one near the suspension, seats or wheels see very different vibration.
Vehicle type sets the excitation level. A passenger car, a heavy truck and a construction vehicle see different levels on the same road.
The transmission path affects the actual load. Whether a part is mounted through a bracket, a rubber isolator or a hanging harness changes the vibration reaching it significantly compared with rigid mounting.
Reading a PSD curve
The horizontal axis is frequency; the vertical axis is acceleration spectral density, usually expressed in g2/Hz.
The area under the curve corresponds to the RMS acceleration, reflecting vibration intensity.
Energy concentrates near resonance frequencies, which are structural weak points to be avoided in design or damped.
Different mounting locations have different reference PSD curves, given as a matrix in the standard.
Common failure modes
Connector loosening: insufficient strength in the locking feature or insufficient preload.
Solder joint cracking: mismatched thermal expansion plus vibration load acting together.
Harness abrasion: rubbing against structure wears through the jacket and exposes conductors.
Bracket fracture: resonance frequency coinciding with excitation frequency, concentrating stress.
Intermittent poor contact: fretting wear makes contact resistance fluctuate, showing up as sporadic faults.
Frequently asked questions
Can random and sine vibration severity be converted directly?
No. The two distribute energy differently: random vibration acts at many frequencies at once, sine at a single frequency. Standards give severity parameters separately, so a simple peak conversion is not valid. Actual projects follow what the customer specifies.
How long does a vibration test run?
The duration in the severity parameters is set by the standard, but it is not equivalent to service life. The purpose of vibration testing is to verify that the structure does not fail at a given severity; it does not indicate how many years the product will last in a real vehicle. Assessing life requires fatigue analysis or accelerated life testing.
Service notes
Our laboratory holds both CMA and CNAS accreditation, covers about 10,000 m2 and runs more than 500 sets of equipment. All testing is carried out in our own laboratories — nothing is subcontracted. Plant visits and on-site witnessed testing are welcome.
Scheduling follows the actual project pipeline. You can state your preferred lead time when you submit samples; we will confirm a feasible plan against current capacity and keep you updated at each milestone. Once the report is issued we send the electronic copy; corrective-action advice can be arranged separately.
