DES recently performed qualification testing on aerospace connectors which involved combined temperature and sinusoidal vibration testing, random vibration testing and shock testing. Combined temperature and sinusoidal vibration tests were performed per EIA 364-28F. EIA 364-28F required test conditions of 10-2000 Hz, 20G maximum acceleration sweeps at temperatures of -54°C and 200°C over the course of 4 hours per axis. Random vibration tests were also performed per EIA 364-28F. Random vibrations at 50-2000 Hz, 46.3 Grms were applied to the connectors for 8 hours per axis. The random vibrations were applied at room temperature. Finally, the connectors were subjected half sine shocks per EIA 364-27C. The shock requirements were three shocks per polarity, per axis at 300G over the duration of 3msec. A sample shock plot can be seen in Figure 1.
Thermal shock testing also called temperature shock testing or temperature cycling exposes products to alternating low and high air temperatures to accelerate failures caused by repeated temperature variations during normal use conditions. The transition between temperature extremes occurs very rapidly during thermal shock testing, greater than 15 °C per minute. Alternatively, temperature cycle testing uses slower rates of change between high and low temperatures. The failure acceleration rate for thermal shock testing is determined by the Coffin-Manson equation as previously discussed in DES’s blog article Temperature Cycling Testing: Coffin-Manson Equation.
Equipment with single or multiple chambers may be used to perform thermal shock testing. When using single chamber thermal shock equipment, the products or samples remain in one chamber and the chamber air temperature is rapidly cooled and heated. This usually results in a slower rate of change in the product response temperature as the entire chamber must be cooled down and heated up. However larger products can be tested in single compartment chambers. Some equipment uses separate hot and cold chambers with an elevator mechanism that transports the products between two or more chambers. This results in a more rapid rate of change in the air temperature. However, there is a limit to the size and weight than can be put in a chamber with an elevator mechanism. DES has both types of chambers for thermal shock testing.
Mass Air Flow Sensors (MAFS) are used to measure the mass flowrate of air entering engines in newer model cars. The mass air flow information is transmitted to the engine control unit (ECU) to balance and deliver the correct amount of fuel mass to the engine. These sensors operate in a very harsh environment, a car engine compartment! Testing their reliability and proving their durability is a very difficult task.
DES was awarded multiple contracts to perform combined temperature and vibration reliability testing of Mass Air Flow Sensors from various automotive part manufacturers and from a major auto parts supplier. Continue Reading Case Study: Combined Temperature & Vibration Testing of Automotive Mass Air Flow Sensors