This method is tailorable only for cargo requiring extraordinary attention, e.g., one-of-a-kind, high value, or key military materiel. Any changes to the test procedure and criteria must be approved by the Director, SDDCTEA, Attn: SDTE-DPE, Building 1900W, 1 Soldier Way, Scott AFB, IL 62225.
2.1 Sequence Among Other Methods
- a. General. Use the anticipated life cycle sequence of events as a general sequence guide (see Part One, paragraph 5.5).
- b. Unique to this method. Sequencing among other methods will depend upon the type of testing i.e., developmental, qualification, endurance, etc., and the general availability of test items for test. Normally, schedule shock tests early in the test sequence, but after any vibration tests. The order of the rail impact testing will be determined by the requesting organization, and specific sequential test requirements should be stated in the test plan.
- c. Considerations.
- (1) If the rail impact environment is deemed particularly severe, and the chances of materiel survival without major structural or functional failure are small, the rail impact test should be first in the test sequence. This provides the opportunity to redesign the materiel to meet the rail impact requirement before testing to the more benign environments.
MIL-STD-810H
METHOD 526.2
- (2) If the rail impact environment is deemed severe but the chances of the materiel survival without structural or functional failure is good, perform the shock test after vibration and thermal tests, allowing the stressing of the test item prior to rail impact testing to uncover combined vibration, temperature, and shock environmental failures.
- (3) If the rail impact environment could damage joints or seals or otherwise affect Electromagnetic behavior, perform the rail impact test before Electromagnetic Environmental Effects Testing.
- (4) There are often advantages to applying rail impact tests before climatic tests, provided this sequence represents realistic service conditions. Test experience has shown that climate-sensitive defects often show up more clearly after the application of the rail impact environment. However, internal or external thermal stresses may permanently weaken materiel resistance to vibration and rail impact that may go undetected if shock tests are applied before climatic tests.
2.1.1 Effects of Rail Impact
Rail impact shock has the potential for producing adverse effects on the physical and functional integrity of transported materiel. The following are examples of problems/failures that could occur when materiel is exposed to the rail impact environment.
- a. Loosening of restraints.
- b. Failure of attachments, creating a safety hazard.
- c. Shifting of materiel on the railcar.
- d. Failure of materiel.
- e. Structural failure.
- f. Fuel spills.
2.2 Design and Modeling Guidance
If it is desired to determine if a test item is capable of withstanding the rail impact environment, an analytical simulation may be created to predict response levels on the item of interest. A rail impact shock example for the railcar deck was computed for use in design specifications and may be used as a starting point for dynamic models of materiel transported by rail. Detailed information can be obtained from paragraph 6.1, reference b, that provides insight to support shock design for rail transport, but should not be considered as approved design guidance. Subjecting materiel to a lab shock test or performing an analytical simulation does not eliminate the requirement to conduct a rail impact test.