Test Method 525 Time Waveform Replication Testing

Time waveform replication testing provides a degree of confidence that materials can withstand test time traces. As a MIL-STD 810 compliance certified lab, we realize the importance of time waveform replication testing. Meeting the MIL-810 military standard requirements can be difficult. We understand the challenges and guide companies through the process.

We are in constant communication throughout the entire test process. Our proven process helps avoid product launch delays. Keystone takes a consultative approach throughout the entire test program. We provide comprehensive reports shortly after completion of the MIL-810 standard testing. Our pricing is competitive and we offer volume discounts. Keystone Compliance creates an accurate test plan to eliminate expensive over-testing. 

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The Importance of MIL-STD-810 Time Waveform Replication Testing

Replication of a time trace in the laboratory is performed for two reasons. First off, this MIL-STD 810 test method is used to provide a degree of confidence that the material can withstand the measured test time trace to which the material is likely to be exposed in the field environment. Second, this method is used to experimentally estimate the material’s fragility level. This is in relation to form, level, duration, or repeated application of the test time traces.

This 810-test method discusses Time Waveform Replication (TWR) from a single-exciter/single-axis (SESA) perspective. Multi-exciter TWR is explained in Method 527.2. Time waveform replication testing provides guidelines for developing test tolerance criteria for single axis TWR testing.

The replication of time traces representing measure samples of the field environments varying in time and frequency was not possible. Currently, SESA TWR consists of the replication of either measured or analytical specified time traces in the laboratory. This includes a single exciter in a single axis. It is performed to accurately preserve the spectral and temporal characteristics of the measured environment.

How Method 525 Time Waveform Replication Affects Products

MIL-STD-810 Test Method 525 is broadly consistent with the philosophy of test tailoring. A high amplitude field measured time trace has potential for producing negative effects on all electronic material. The potential for adverse effects may be related to transition time and duration of the time trace. In performing a TWR test, it is desirable that the onset/termination of the significant environment be consistent with the onset/termination of the environment foreseen in the field.

Information on the MIL-STD-810H Test Standard

Generally, significant time-varying traces may occur at any time during the life cycle of the material. These traces are usually interspersed among stationary random and shock environmental conditions that are covered under guidance provided in Methods 514 and 516, respectively.

The following six forms of time trace are potentially useful candidates for Time Waveform Replication Lab testing.

• Stationary random Gaussian time trace with arbitrary ASD of arbitrary duration
• Stationary random non-Gaussian time trace with specified ASD of arbitrary duration
• Short duration time trace
• Non-stationary/stationary time trace that is respective at fixed period
• Non-stationary/stationary time trace that has time-varying amplitude, time-varying frequency or both of an average duration
• Non-linear form time trace

This MIL-STD-810 Standard has two basic military standard test procedures. (1) The SESA replication of a field measured material time trace input/response. (2) the SESA replication of an analytically specified material time trace input/response.

For Procedure I, it is not recommended that a factor be applied to enhance the measured time trace for testing. For Procedure II, any scaling must be consistent with information in the paragraphs above. Generally, the scaling must not be ad hoc in nature.

For the TWA replication of measured time traces in the laboratory, the test levels are fully specified by the field measures time traces. If several field-measured traces are available, the tester will want to make up a single ASCII file consisting of several “events” correctly spaced in time.

Some other general considerations include it being essential that the test time trace be fully documented. The ASCII file of the test time trace can be made to other laboratories for application and testing. Secondly, the test item may be instrumented at other locations rather than at the point of “control”.

Lastly, for the TWR procedure, the test item is subjected to a sufficient number of suitable time trace events to meet the specified test conditions and is determined by the material’s life cycle profile.

Limitations of the MIL-STD-810 Time Waveform Replication Test

While applying the tailoring process, note the limits explained within this method. All measured time traces can be replicated with TWR. Provided they are within band limit capabilities of the exciter control system to which they are applied for testing purposes. Limitations of this method include

• Does not include long hour time traces that can be termed “stationary” in nature. It is possible to repeat a trace multiple times. However, variations associated with the experiment repetitions in the field will not be captured
• Does not address repeated environments that may be of a non-stationary nature because of the occurrence pattern of the environment.
• Generally does not address the characteristics of the time trace on the material in terms of material “rise-time” response

Keystone Compliance Provides Time Waveform Replication Compliance Testing Services

Keystone’s expert MIL-STD-810 testing lab technicians strive to give our customers more time and energy on product development instead of testing. In addition to MIL-STD-810 time waveform compliance testing, Keystone has a full scope of expertise including pyroshock, fungus, immersion, and sand and dust. We have a full lab of test equipment which permits us to provide short lead times on scheduling. 

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