Force vs strain controlled fatigue identifies which quantity a cyclic test controls. A report can contain force and strain information while controlling only the specified quantity. Ask the laboratory to name that control mode before comparing its results with another report.
For aluminum procurement, keep the requested test tied to the material condition, specimen and engineering question. A force value on a page does not by itself identify a force-controlled test.
On this page
Two fictional reports contain the same field name
Imagine a purchasing file, C74, containing two laboratory report summaries for an aluminum development project. Both summaries include a force column and cycle information. Their front pages do not clearly state the control mode.
The purchaser cannot resolve the mode by pointing to the force column. The laboratory needs to identify what its test controlled and what that column reports.
| Summary | Information still needed |
|---|---|
| A: force column shown | Was force controlled, or was it a reported response under another control mode? |
| B: force column shown | Which quantity was controlled, and which strain information was recorded? |
C74 is an invented document example. No fatigue results, approved test settings, customer project or material-life claim are presented.
The first useful correction is a clear control-mode statement from the issuer. Retain the original report, its specimen reference and that clarification together.
Check 1: identify force vs strain controlled fatigue
The ASTM E466-21 public overview describes axial force-controlled fatigue testing at constant amplitude. Its stated scope concerns specimens with predominantly elastic strains under the described test conditions.
The ASTM E606/E606M-21 public overview describes strain-controlled fatigue testing. It identifies cyclic total-strain measurement and cyclic plastic-strain determination, with total strain usually controlled throughout a cycle.
These public descriptions make the control distinction explicit. Keep the actual method and test configuration in the laboratory record instead of treating a report’s largest value as its control definition.
Ask the laboratory to explain any abbreviated mode label. A useful clarification names the controlled quantity and links it to the reported specimen and test history.
If an alternative mode is proposed for a quotation, record it as a proposed change to the test scope. Have the responsible technical reviewer determine whether it addresses the intended material question.
Do not approve an alternative solely because its report still contains stress or force entries. The named output fields need to be read in relation to the control mode.
Check 2: retain the specimen and method scope
E466’s public scope is restricted to the described axial specimens under a constant-amplitude periodic force in air at room temperature. It excludes full-scale component, structure and consumer-product testing.
E606/E606M also limits its method to specimens rather than full-scale components or structures. Its overview identifies material, strain history and environmental considerations in interpreting the resulting evidence.
For a purchasing review, identify which sample was actually tested. Keep its material designation, supplied or processed condition and specimen reference beside the report.
A prepared material specimen and a finished aluminum assembly need their respective scopes preserved. Ask the responsible engineer how the specimen evidence relates to the current component and its intended service.
The aluminum fatigue-strength inquiry guide covers the broader application evidence request. This comparison addresses the specific control-mode field within a laboratory record.
Retain the actual method edition in the quotation and report. Public overviews are background for this article; use the complete applicable method and the laboratory’s approved procedures for execution.
The source descriptions do not establish an aluminum part’s acceptance criterion here. Keep the project’s requirement and technical review with the actual evidence.
Check 3: distinguish control from measured response
Ask which channels the report records and what each field means. Preserve their units, definitions and relevant reference information with the output.
A strain-controlled record can include force or stress information. A force-labelled entry therefore needs its stated role: controlled input, measured response or another reported quantity.
For any strain entry, ask the laboratory to identify the reported strain quantity. Keep a named total-strain or plastic-strain entry attached to its definition instead of shortening both to one ambiguous heading.
If a report includes more than one trace, keep its legend and specimen reference. Ask the issuer to explain how those traces relate to the identified cycle or stage.
Retain cycle information with its reported outcome. The fatigue-runout record guide addresses the separate question of preserving a planned stop and its outcome label.
Do not combine observations from different modes into an unlabelled average. Request the responsible reviewer’s comparison basis and retain the original records.
Similarly, keep a static material-property certificate identifiable as its own evidence. A certificate entry does not fill in a missing cyclic test configuration.
Send a laboratory request that closes the gap
Identify the material and required development or acceptance question. Provide the specimen or sampling information approved by the project’s technical authority.
Name the requested method, edition and control mode where these have been defined. If they remain unresolved, ask the laboratory and responsible engineer to agree the scope before execution.
Please confirm the control mode for report C74 and identify each force and strain field’s role. Link the clarification to the specimen, method edition, test history and reported outcome. Explain any difference from the scope requested in the order.
This wording is an original request for the fictional file. The actual order should use its own references and approved scope.
Request the report contents that the reviewer needs to interpret the result. Preserve any laboratory limitation or unresolved condition in the purchasing file.
When the reply changes a quotation, retain the revised scope and its approval with the original inquiry. This lets the receiving team see which work was actually ordered.
Coordinate the aluminum blank handoff
Give the cutting supplier the approved stock description, blank drawing, quantities and source references. Identify any required orientation and labelling arrangement for the delivered blanks.
Keep laboratory specimen preparation with its responsible team. A saw-cut blank does not establish a completed fatigue specimen or a test control mode.
Define the blank’s dimensional and handling checks separately. Retain the stock identity so the laboratory can connect the received pieces to the intended material.
Send JiurunCut your aluminum stock and blank-cutting requirements for a machine discussion. Keep the subsequent test specification and engineering review linked to the handoff.
Questions about force vs strain controlled fatigue
Does a force column prove that force was controlled?
Ask the issuer to identify the control mode and the column’s role. A reported response is a separate field from the controlled quantity.
Does a method number approve the complete aluminum assembly?
Read the specimen scope and obtain the responsible application review. Preserve the difference between the test record and component acceptance.
Can records from the two modes be compared automatically?
Retain their conditions and ask the qualified reviewer to establish the comparison basis. Keep each original record identifiable.
What should a missing control-mode statement become?
An explicit clarification from the laboratory, linked to the actual specimen and report.