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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Dave White (white@spectralsolutions )
Organization:Spectral Solutions
Date posted: Fri Jun 4 17:06:40 US/Eastern 1999
Subject: Life Cycle Environmental Profile
Message:
Help! I am trying to create a Life Cycle Environmental Profile (LCEP) to help guide a series of qualification tests. The LCEP defines all of the environmental stresses that the product is likely to encounter from manufacturing, shipping, storage, installation, and use. I have been able to get reasonably good data on all of these environments except for installation. The product is a tower mounted reciever front end module, approximately 100 lbs. My problem is that the installation environment can vary quite a bit (from wall mounted to several hundred feet up whatever style of tower imaginable). I anticipate mechanical shock as the unit is hauled up the tower will be the main concern. Does anyone out there have any experience that could help? If I can not find existing data I plan to attempt a rough "worst case" estimate. Does this seem reasonable? Thanks for any help you can give me (I'm fairly new to reliability engineering) Dave


Reply:

Subject: Shock Test
Reply Posted by: Bruce Dudley (bdudley@iirti.org )
Organization: Reliability Analysis Center
Date Posted: Thu Jun 10 9:37:29 US/Eastern 1999
Message:
Bench handling conditions typical include worst case shock environmental design guides that specify an "g" range of 15 to 90 with a shock period of 11 milliseconds. For vibration levels, the typical range for ground mobile which is applicable to your transportation mode are 1 to 10 "g" of random vibration with a frequency range of 10 to 300 Hz. The shock test that should be applicable to equipment being mounted by tower installation, is stated in MIL-STD-810, and is test method 516.5 "Shock Test" which requires eight drops from 30 inches for a 100 pound package. These extremes should provide some degree of guidance for your life cycle environmental profile. An old techinical report that I found called "Revisions of Environmental Factors for MIL-HDBK-217B" by the Martin Marietta Corperation (RADC-TR-80-299) has an interesting influence matrix for many environments and over twenty conditions that might help.


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