Case Study: Combined Temperature & Vibration Testing of Automotive Mass Air Flow Sensors

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.

Mass Air Flow Sensors (MAFS) Combined Temperature Vibration Testing
Mass Air Flow Sensors (MAFS) Combined Temperature Vibration Testing

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.

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Vibration Testing: A Questionnaire for Clients

Figure 3.  Vibration Testing using a Cube Fixture

Vibration testing can be a complicated process. We have created this questionnaire to help make communication between the vibration test lab and customer more efficient. The questionnaire allows us to capture all the pertinent facts about your test requirements. Providing the information below will help us provide an accurate quotation and to perform a successful vibration test. We can help you with answering the questions if needed. Many engineers, not familiar with vibration and shock testing, a subject not taught by universities, may wish to further their education.  May we respectfully suggest that you visit http://equipment-reliability.com/training-calendar/vibration-and-shock-testing/  for vibration and shock training courses.

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What is Pyroshock Testing?

First we should answer, what is a pyroshock or a pyrotechnic shock? Both pyroshocks and pyrotechnic shocks are the same thing. A pyroshock occurs when explosive events are used to separate the stages of rockets or missiles, or from a ballistic impact to a structure by a projectile. When a pyroshock occurs, a stress or shock wave propagates through the structure and into the electronic equipment contained within the structure.

Pyroshocks are unique shocks that have high G-level, high frequency content with very little velocity and displacement change during the shock. The frequency range of a pyroshock is usually 100 Hz to 10,000 Hz or greater. Pyroshocks have a very short duration of usually less than 20 milliseconds. The acceleration time history of a pyroshock approximates a combination of decaying sinusoids as shown in Figure 1.

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Delserro Engineering Solutions Featured in Desktop Engineering

Delserro Engineering Solutions (DES) was honored to be featured in a recent article discussing the capabilities of engineering testing companies. The article highlighted the benefits, in terms of both design and cost, of adequately testing designs, preferably as early in the process as possible. It also discussed the ins and outs of partnering effectively with a reliability testing facility.

The goal of this article was to teach product developers how to get the most bang for their testing buck; a goal that aligns perfectly with DES’s philosophy. No matter what your testing needs are, be they HALT, HASS, or other environmental or stress tests, DES is able to help you design and implement the most comprehensive and accurate test possible. As always, our client’s success is the source of our satisfaction.

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How a HALT Test Shows The Future

Circuit Board HALT
HALT of Circuit Boards
Highly Accelerated Life Testing Procedures

Speeding up the process of device or circuit failure requires extreme inputs, those that are unlikely to occur during real-world use by customers regardless of the environment. Three common testing inputs are high and low temperatures, rapid cycling of the same and vibration along six-axes. In some cases, a highly accelerated life test (HALT) will incorporate combined temperature and vibration stresses. These inputs can result in component failure in the span of days, hours, or even minutes compared to months or years of typical usage.

 

Benefits of HALT Testing

While the percentages of failure based on the stress applied to a product can vary significantly, highly accelerated life testing can typically expose weaknesses faster than other means of testing. For example, of the above inputs, roughly two-thirds of failures will only come after the introduction of vibration alone or combined vibration and temperature tests. This means that during the product development process, a significant number of potential flaws would not be identified through testing that did not include these two stresses.

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Accelerated Life Product Reliability Testing of a Carrying Handle

HALT Accelerated Product Life Cycle Testing
Customized ALT Setup by DES

A leading medical technology company contracted DES to perform Product Reliability Testing of a carrying handle. A sample of the test can be seen below and in our video library. The carrying handle had to be pulled, released, rotated and subjected to a sizable lifting force, approximately 20,000 times during its life time. 

DES has considerable capability to complete product reliability testing. The main challenge for this project was that each cycle consisted of complex motion. The motion included pulling/releasing the handle to unlatch/latch a pin while rotating the handle. In order to achieve this, DES had to design fixtures and mechanisms that would reposition the carrying handle into each of the designated positions. The number of cycles was automatically counted until failure or 20,000 cycles were completed. During the test, the force to pull the handle was measured at various intervals. The Accelerated Life Testing was completed successfully demonstrating a high reliability.

Please visit our video library to see more examples of DES’s capabilities.

Random Vibration Testing

Random Vibration Testing is one of the more common types of vibration testing services performed by vibration test labs. A primer containing a technical explanation on random vibration testing can be found in our blog article Sinusoidal and Random Vibration Testing Primer.

Real world vibrations are usually of the random type. Vibrations from automobiles, aircraft, rockets are all random. A random vibration test can be correlated to a service life if the field vibrations are known. Since random vibration contains all frequencies simultaneously, all product resonances will be excited together which could be worse than exciting them individually as in sine testing. Sometimes random vibrations are mixed with sine vibrations in Sine-on-Random Vibration Testing. Also, a low level of broad band random vibration can be mixed with additional high levels of narrow band random vibrations in Random-on-Random Vibration Testing.

Some common test standards that have specifications for Random Vibration Testing are:

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DES Increases Combined Temperature & Vibration Testing Capabilities

Vibration Testing - Delserro Engineering SolutionsVibration Testing - Delserro Engineering SolutionsDES added another larger AGREE Chamber to perform Combined Temperature and Vibration Testing. This gives DES additional capability to perform combined environmental testing on larger products. DES has performed Combined Temperature and Vibration Testing on car engine sensors, helicopter sensors and outdoor heavy industrial products. Some of the test specifications include MIL-STD-810 and General Motors GMW 3172.

The Equipment Capabilities Are:

  • Combined shock or sinusoidal, random, mixed mode vibration and temperature
  • Temperature range from -80°C to +180°C (-112°F to +356°F)
  • Temperature rate of change up to 20°C/minute
  • 9 cubic feet interior work space, cvo

To learn more about our combined temperature and vibration testing services, visit our website, and be sure to contact us if you would like to find out how our services can work for your products.

Sinusoidal Vibration Testing

Sinusoidal or Sine Vibration Testing is one of the more common types of vibration testing services performed by vibration test labs. See Sinusoidal Vibration Basics to learn more about vibration fundamentals. A primer containing a more technical explanation on sinusoidal vibration testing can be found in our blog article Sinusoidal and Random Vibration Testing Primer. The types of Sinusoidal Vibration Testing are Sine Sweep Vibration Testing, Sine Dwell Vibration Testing, and Sine-on-Random Vibration Testing.

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Accelerated Life Cycle Testing of a Case Handle

A leading commercial product manufacturer contracted DES to perform Accelerated Life Cycle Testing of a case handle.  A sample of the test can be seen below and in our video library. The handle had to be opened and closed many thousands of times during its life time. In addition, two thirds of the cycles had to be completed with the sample exposed to hot and cold temperatures.


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