Understanding the behavior of car components under various impact conditions is crucial for improving vehicle safety and performance. For instance, analyzing how a car door reacts during an impact can reveal insights into its performance during a crash, enabling the development of safer designs. This detailed examination also helps in selecting materials that are more effective at absorbing or damping vibrations, which contributes significantly to overall vehicle safety.
The same applies to wheels, which are among the first components to respond to forces generated by obstacles on the road surface, such as potholes or curbs. Their design and the materials influence how well the vehicle handles these impacts. Minimizing or damping vibrations contributes to a perception of quality and attention to detail, which can enhance customer satisfaction and brand reputation
To optimize the safety and comfort of cars it is crucial to understand how components deform during dynamic processes and under stress, like the closing of a door or hitting an obstacle with the tire. One challenge in assessing deformation is covering a large area comprehensively, which traditional measurement methods often struggle to address. The following measurements on a car door and tire illustrate an approach using, video data only, which allows for capturing the necessary insights with little effort and increased efficiency.
For our test measurement, we used a Chronos high-speed camera to capture video data of both scenarios, recording at 1000 frames per second. Given the uniform surfaces of the car door and tire, we needed to prepare them to provide visual cues of any pattern shifts or distortions. To accomplish this, we applied white tape in a criss cross pattern to the door and the tire. The camera was placed on a tripod around 1,5m away and rearranged into different angles.
Since the measurements were taken in a relatively dark test facility, we used flicker-free lighting to ensure optimal image acquisition during the recording process.
Traditional methods like using multiple acceleration sensors or a multi-point laser Doppler vibrometer are costly, complex and time-consuming. Sensors add weight, altering the structure's deformation, while laser systems require precise, often non-repeatable conditions, necessitating test hammer excitation.
When a car door is closed, significant force propagates through the door panel and its internal structure. Since this is a dynamic process occurring within milliseconds, capturing the event accurately is essential. To achieve this, the Chronos High-Speed Camera and lights were positioned at various angles, with the most relevant data obtained from an angle of approximately 30 to 40 degrees to the car.
In order to understand how this energy is distributed, the video data is imported into our vibration analysis software WaveCam. WaveCam then amplifies the supposedly invisible vibrations of the car door and makes them visible to the human eye. In the resulting visualization, red indicates the maximum deformation, representing the upper limit of the scale, while light blue shows the areas of minimal deformation.
In the second measurement, we focused on understanding the deformation behaviour of tires when hitting an obstacle. Specifically, we analysed how the tire reacts when an obstacle strikes the sidewall of the wheel, aiming to identify the resulting stress points and deformation patterns within the tire structure. To accurately simulate the shock impulse, a rubber hammer was used to deliver one controlled impact.
Given that our primary interest was in the tire's response rather than the rim's, we applied a cut-out during post-processing to isolate and examine the tire's deformation in detail. Various measurement angles were considered, with the most informative results captured at an angle of around 30 degree.
The time ODS (Operational Deflection Shape) from the first measurement clearly illustrates how the impulse travels through the door structure. It vividly shows that the bottom middle section of the door as well as the one around the door handle resonate more strongly than other sections.
The time ODS of the tire shows how the impulse travels through the complete tire. Meanwhile, the Frequency ODS reveals specific resonances: a prominent resonance across a larger portion of the tire at 39 Hz and higher frequency modes, such as those observed at 188 Hz, which are associated with the outer part of the tire.
The measurements conducted on the car door and tire have proven that using Vibration Analysis with WaveCam technology in combination with a high-speed camera is a valid method to gain valuable information of the deformation behaviour of car parts in frequency and time domain. This vibration monitoring approach allows for the analysis of responses to various impacts with minimal effort and in a short time frame. For a more detailed analysis, it could be beneficial to work with a smaller tape, or a patterned foil for a higher resolution. Additionally, capturing different angles, e.g. the top view of the tire, could hold additional information.
