An environmental chamber is an enclosure used to test the effects of specified environmental conditions on industrial products, materials, and electronic devices. The chambers can provide constant temperature exposure, variable temperature exposure at various thermal ramp rates and humidity from 15% to 95%. Such a chamber can be used as a stand-alone test for environmental effects on test specimens, as preparation of test specimens for further physical tests or chemical tests. Chamber testing parameters can be selected for qualification testing where product failures are usually cause for rejection or chamber parameters can be selected for reliability testing. During reliability testing, products are stressed beyond use temperature to eventually precipitate failure from which product design improvement opportunities are exposed. Testing products to fail is also a mechanism to quantitatively measure reliability growth across an evolving or multi-generational product portfolio.
A highly accelerated life test (HALT) is a stress testing methodology for rapid product reliability assessment. HALT testing is currently in use by most major engineering organizations to improve product reliability in a variety of industries and is performed during the product design and early manufacturing cycles. Environmental stresses are applied in a testing procedure which eventually reaches levels significantly beyond those expected during use and eventually cause failure. The determination of product operating limits and destruct limits allow greater levels of operating margin to be designed into a product which leads to fewer field reliability failures (lower Weibull hazard rate). Temperature cycling and repetitive shock, power margining and power cycling are the most common forms of failure acceleration for electronic equipment. Using extensive product monitoring of internal signals and temperatures, AES can provide quantitative performance data over the simple and less valuable pass/fail attribute data. Any HALT lab can take a product to failure but Accolade is one of the few HALT facilities that has extensive failure analysis capability to analyze HALT failures and deliver root cause data and corrective action recommendations. Without root cause and corrective action, reliability growth as a byproduct of HALT will not be achieved. HALT chambers are characterized by wide temperature range and fast thermal rates concurrent 3-axis, 3 rotations (roll, pitch and yaw) to achieve 6 degree of freedom (6dof) random vibration. The HALT chambers at AES, using patented QRS vibration technology, provide exceptional low frequency performance when compared to repetitive shock (RS) type HALT chambers. To learn more about the two dominant HALT chamber vibration technologies and their associated performance differences, refer to the paper "Differences Between QRS and RS Type Vibration Systems" in the technical forum page
A mechanical or physical shock is a sudden acceleration or deceleration caused primarily by impact or drop. Impact shock interaction can be characterized by the peak acceleration, the duration and the shape of the shock pulse (half sine, sawtooth, triangular, trapezoidal, etc.). The shock magnitude can reach levels of several thousand G's and sub-millisecond durations depending on the testing protocol. Impact shock testing is performed by attaching a product to a table which is raised and accelerated toward a reaction mass where well defined shock pulse shape, magnitudes and durations are selected for the product. For lower magnitude shock testing (less than 75G's) an electrodynamic shaker can be used. The electrodynamic shaker platform allows easier realization of sawtooth, triangular and trapazoidal shock pulse shapes. The test sample may have accelerometers attached to record the shock response spectrum or strain gauges to evaluate distortion of selected structures in or on a sample. During drop shock testing, an individual sample or a boxed sample is dropped at selected drop heights onto hard (steel) or semi-rigid (wooden) surfaces and is typically used for transportation testing.
Vibration testing is accomplished by introducing a forcing function into a structure, usually with an electrodynamic or hydraulic shaker. Vibration testing is performed to examine the response of a device under test to a defined vibration environment. The measured response may be fatigue life, resonant frequencies or simulation of real world environments for product qualification. For relatively low frequency and high displacement forcing, servohydraulic shakers are used. For higher frequency and lower displacement forcing electrodynamic shakers are used. The most common profiles of vibration testing services conducted by vibration test labs are Sine, Swept Sine and Random. Sine tests are performed to survey the structural response of the device under test. A random test is generally considered to more closely replicate a real world environment such as road inputs to a moving automobile.
Accolade Engineering Solutions offers a variety of environmental testing applications services. Contact us today to discuss your testing needs with someone who can provide you with the expert knowledge to determine the right testing solution for you. .
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