Environmental Test

Environmental testing determines how well products withstand the stresses likely to be experienced in normal use. Of course, you may need to know if a design will survive one event representing 10x the normal stress. This type of requirement arises in seismic testing of telecommunications racks. Because communications networks are critical to security and safety during emergencies, network operators must ensure that equipment will keep on working even after an earthquake.

Although test-like-you-fly directly relates to aerospace projects, the underlying intention is to mitigate risk by running the most appropriate tests. In that sense, the phrase applies more broadly. Skipping or compromising on any part of a test, even one that may seem to be inconsequential, has led to mission failure. So, it is no wonder that test-like-you-fly has gained a special meaning among mil/aero professionals.

One of the most difficult aspects of selecting an accelerometer for a particular application is interpreting the accelerometer’s specifications. Often you understand your test requirements well but run into difficulty matching these requirements with available accelerometer models.

To gain optimum results from highly accelerated life test (HALT) and highly accelerated stress screen (HASS), it is important to properly plan, implement, document, and take corrective action when embarking on this path. When design defects are removed proactively before manufacturing, warranty costs are reduced and sales and reorders increase because customers are more satisfied with the product.

Many shaker controllers for random vibration testing are based on the well-established FFT data processing algorithm. A test specification is given in the frequency domain in terms of power spectral density (PSD), and time histories are reconstructed from the prescribed PSD by the inverse FFT (IFFT).

If all products were operated in controlled, benign conditions, there would be little need for environmental testing laboratories. When used in the real world, equipment is exposed to shock, vibration, temperature extremes, dust, humidity, and many more factors that affect performance. As part of a thorough design process, manufacturers subject products to simulated stresses to ensure that specifications will continue to be met in the actual use environments.

Cost-effective burn-in-with-test is essential to produce high reliability components. To ensure uniform burn-in of all components, a test solution must control the temperature, voltage, power, test sequence, and inputs/outputs to the DUT. Of these, temperature becomes significantly harder to control as the power level of the devices increases.

Three tests'shaking a product first in the X axis, then in the Y axis, and finally in the Z axis'are not realistic. But MIL-STD-810, published in 1962, revised six times since 2000, and currently in its F revision, has only offered the single-axis-at-a-time method. However, the G revision, scheduled
for release in May 2008, will include the new Multiexciter Test Method 527.

Three tests'shaking a product first in the X axis, then in the Y axis, and finally in the Z axis'are not realistic. But MIL-STD-810, published in 1962, revised six times since 2000, and currently in its F revision, has only offered the single-axis-at-a-time method. However, the G revision, scheduled
for release in May 2008, will include the new Multiexciter Test Method 527.

Vibration testing emerged in the early 1960s as electronics systems became more complex and widely available. This led to a need for greater reliability, with one of the major early adopters being the manned mission to the moon.

Vibration testing helps to predict how well a product will withstand its intended service or transportation environment. Some new vibration controllers have the capability to replicate data recorded while the product is being used. For example, the accelerations a vehicle's suspension experienced on a bumpy road could be recorded and then played back to test car suspensions.

Hurricane Katrina produced a massive surge of water on the U.S. Gulf Coast that overtopped and eroded away more than 50 levees and floodwalls that compose the New Orleans and Southeast Louisiana Hurricane Protection System (Figure 1). In the aftermath of this catastrophic disaster, several investigations were conducted into the performance of the levees and floodwalls and the causes of the damage and failures.

Simplify test definition and shorten test throughput times by using an instrument that has universal adoption and inexpensive test automation software.

The latest design is finished. But before the R&D manager will sign the shipment release, he wants to see the design verification test results, and the test department manager won't approve the release until he reviews the environmental characterization results.

One of the most critical decisions in developing random vibration tests also is the most neglected.

The location of the control accelerometer is one of the most critical decisions when developing random vibration tests. As proven in numerous experiments, the position of the accelerometer can greatly affect the results of a test.

For successful HALT testing, repeatability is as important as accuracy.

Generally, one of the more important objectives when implementing an experiment is test reFpeatability. An experiment must be repeatable to validate the test results. In fact, a well-written test report contains all the information needed for anyone to repeat a given test and verify the results. When performing a highly accelerated life testing (HALT) experiment, the same is true, but test repeatability is defined differently.

Even with technology changing faster than validation procedures can be rewritten, it still is possible to perform thorough product testing.

With the ever-changing complexity of automotive electronics and the resulting complexity of hardware/software interactions, validation testing often misses key failure modes and problem areas. Often problems only are found late in a program development or as warranty returns from the field.

Heat flow considerations play an important role in any strategy for burning in high-power devices.

The purpose of burn-in with test is to significantly increase the reliability of high-power devices by detecting and eliminating parts that fail early in service. Devices are stimulated by various inputs, including pulsed inputs or built-in self-test (BIST) techniques. Device temperatures typically are held at set points from 100'C to150'C.

Reproducing real-world vibration environments for testing may introduce a higher level of product reliability.

Widely accepted as a method to improve product quality, vibration testing is used to qualify products for production. Either alone or combined with an environmental chamber, vibration testing is a critical step in the successful development of new products.

An industry expert shares some common sense about a very simple approach to product improvement and cost reduction.

After reading several recent technical articles on highly accelerated life testing (HALT) and highly accelerated stress screening (HASS), I noted that there seemed to be many incorrect conceptions floating around. One article talked about HALT as an extreme over-design activity that eventually would sink a company due to costs from continuing improvements without end. This end result is one that, indeed, could occur if those performing HALT had no knowledge of correct procedures and concepts. The crux here is correct procedures and concepts.

Today's mine detectors survive some tough treatment long before they ever reach the battlefields.

In an age of global terrorists, military readiness means the capability to deploy equipment needed for the job anywhere at a moment's notice. When the Pentagon needed rapid environmental testing of a new, hand-held landmine detector, Sypris Test & Measurement put the product through its paces.