Materials testing laboratory selection by the scope on the certificate

Selecting a laboratory

1. Read the accreditation scope, not the website. Accreditation bodies publish the exact methods each laboratory is accredited for. Check that your method appears, by standard number, rather than relying on a general claim of accreditation.
2. Name the method in the enquiry. Different standards for the same property give different numbers, and a laboratory quoting against an unnamed method will choose the cheapest. State the standard and the acceptance criteria in the request.
3. Ask what is subcontracted. Many laboratories subcontract part of a panel. That is acceptable when declared and disclosed on the report, and it affects turnaround, chain of custody and who is accountable for the result.
4. Establish sample requirements before shipping. Quantity, conditioning, packaging and how the sample must be identified. Samples rejected on arrival or conditioned incorrectly are the commonest cause of a delayed report.
5. Compare turnaround including reporting. Test time and report time are different, and the second is frequently longer. Ask for the quoted turnaround to be to a signed report, and ask what expediting actually costs.
6. Decide in house against outsourcing on volume and defensibility. Routine high volume testing with a stable method suits in house equipment. Occasional testing, unusual methods and anything requiring accreditation is almost always cheaper and safer outsourced.

Scope is the whole question, whether it is a polymer testing laboratory or a metal testing laboratory

A certificate of accreditation is accompanied by a schedule listing the methods, materials and ranges it covers. That schedule is the useful document, and it is public. Reading it takes minutes and prevents the discovery that a report cannot be used.

Where your method is outside the scope, ask whether it can be added, what that costs and how long it takes. Sometimes it is straightforward; usually it is not worth waiting for.

Uncertainty is part of the result

A measurement without a stated uncertainty cannot be compared to a specification limit honestly, because a result near the limit may or may not exceed it. Accredited reports state it; unaccredited ones often do not.

Ask for it explicitly, and use it when setting internal limits. A specification tighter than the measurement uncertainty is a specification that will fail randomly.

Accreditation for the method, not the laboratory, and the ISO 17025 lab schedule

A laboratory is accredited for specific methods on specific materials, listed on a schedule. Accreditation in general does not cover a test that is not on it, so the question to ask is whether your exact method and material appear, and to read the schedule rather than the certificate.

Sector approvals go further. Aerospace and similar industries maintain their own approval schemes, and a laboratory without the relevant approval cannot produce a report the customer will accept, however good its work is. That approval, not the price, usually decides the choice.

Failure analysis at a metallurgical testing laboratory is a sequence, not a test

Investigating a failure starts with the part as found: photographs, the fracture surface untouched, the service history and the specification it was made to. Cleaning or sectioning before that record exists destroys the evidence that would have identified the mechanism.

Then it proceeds in order: visual and fractographic examination, chemical composition, metallography, hardness and mechanical properties, and only then a conclusion. A laboratory that starts by cutting the part up is running tests rather than an investigation, and the distinction matters when the report has to support a claim.

Destructive and non-destructive tests at a plastic testing laboratory answer different questions

A destructive test measures the property of a sample and tells you about the material. A non-destructive examination looks for flaws in the actual component and tells you about that part. A structure needs both: qualification of the material and inspection of the item.

Non-destructive work is personnel-certified as much as laboratory-accredited, because the result depends on the examiner. Ask what level of certification the people hold for the method and the product, and for the written procedure the examination follows.

Thermal methods and what each measures

One family measures mass change as a sample is heated, which gives composition, filler content, moisture and decomposition. Another measures heat flow, which gives transitions: melting, crystallisation, glass transition and reaction enthalpy. They answer different questions and are frequently run together.

Thermal conductivity is a third and separate measurement, made on a specimen of defined geometry, and it is what a thermal design needs rather than a transition temperature. Asking for thermal analysis without saying which property is wanted is the usual source of the wrong quotation.

Calibration, mapping and the paperwork that travels

Dimensional calibration certifies a gauge, a fixture or an instrument against traceable standards, with an uncertainty statement. That uncertainty is what propagates into every measurement made with it, and a certificate without one is of limited use.

Mapping an oven, an incubator or a chamber establishes the spread of temperature across its working volume, loaded as it will be used. It is what justifies where a sample may be placed, and in a regulated setting it is repeated on a schedule and after any change.

materials lab testing, and the disciplines inside it

A materials laboratory is several laboratories under one roof, and they are accredited separately: chemistry for composition, mechanical for strength and hardness, metallography for structure, non-destructive testing for flaws, corrosion for durability, and thermal and polymer analysis for plastics. A failure investigation uses most of them in a sequence. A conformity check uses one against a standard. So the first question is which discipline your question belongs to, since a laboratory strong in mechanical testing may subcontract the chemistry, and a subcontracted result carries someone else's accreditation.

aerospace materials testing, and what the sector adds

Aerospace work adds approvals and traceability to ordinary materials testing: the laboratory holds sector accreditation as well as the general standard, the specifications are the primes' own rather than a generic standard, and every result is traceable to a material lot and often to a part. Test matrices are larger because design allowables need statistics, environmental conditioning is routine, and non-destructive inspection sits beside destructive testing. Ask which approvals the laboratory holds and which specifications it is qualified to test to.

Common questions

Does accreditation mean every test is accredited?

No. It applies to a defined scope of methods, and laboratories routinely perform unaccredited work alongside accredited work. The report should distinguish them, and you should check which yours is.

Why do two laboratories report different values?

Different standards, different specimen conditioning or different sample preparation, in that order. Naming the standard and the conditioning in the request removes most of the discrepancy.

When does in house equipment pay?

When the same test is run often enough that per sample outsourcing exceeds the cost of the instrument, calibration and the person. Single purpose instruments used occasionally are usually a poor investment, because calibration continues whether they are used or not.

What should a test report contain?

The method by its standard reference, the specimen description and conditioning, the equipment used, the result with its uncertainty, any deviations, and a signature. A number without those is not a report.

Is an accredited laboratory accredited for my test?

Not necessarily. Accreditation covers specific methods on specific materials, listed on a schedule. Read the schedule rather than the certificate, and check for any sector approval your customer requires.

What should I not do before a corrosion testing laboratory investigation?

Do not clean, cut or handle the fracture surface. The part as found is the evidence; photographs, service history and the specification come before any sectioning, or the mechanism cannot be established.

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