Mechanical Testing

Mechanical testing is how a specification gets checked against reality. The range we cover is unusually wide, from polymer and coating samples that fail under a few hundred pounds to steel sections that need more than a hundred thousand, so the same work that identifies your material can also tell you what it will carry.

Tensile testing

A tensile test pulls a machined specimen to failure and records the whole story on the way: the load at which permanent deformation begins, the maximum the material carries, and how far it stretches before it lets go. Testing follows ASTM E8/E8M for metallic materials and ASTM A370 for steel products, with ISO 6892-1 where a job is written to ISO or EN rather than ASTM, and ASTM D638 for plastics.

Reported values are the ones a specification is written around:

• Yield strength, normally 0.2% offset, or upper and lower yield where the material shows a distinct point
• Ultimate tensile strength
• Elongation over a defined gauge length
• Reduction of area

Specimen form follows the product: round specimens from bar, forgings, and heavy sections; flat or strip specimens from plate and sheet; full-section or strip specimens from tube and pipe; and sub-size specimens when a failed component only yields so much material.

Three tensile testing machines

Those specimens are pulled on three machines. Two carry the metals work, one rated to 60,000 lbf and the other to 120,000 lbf, while a third, rated to 11,000 lbf, is kept for polymers, coatings, and thin sections. The specimen decides which machine it runs on, since a load has to sit well inside a machine's range before the numbers mean anything.

From coatings and polymers to heavy steel

Very few metallurgical labs cover both ends of this range. A frame sized for pipe steel cannot resolve the few hundred pounds that break a polymer dogbone, and a frame sized for polymers cannot begin to load a plate coupon. Having all three available means a plant that runs steel piping, a polymer liner, and a coated vessel gets its answers on one report, interpreted against one another.

On the light frame we test polymer and elastomer specimens, including HDPE, PP, ECTFE and TPV, thin sheet and strip, and coated or lined materials, both as pull-off adhesion on the coating itself and as tensile testing of the coated substrate, where the question is how the system behaves rather than the substrate alone. That work sits naturally alongside our coating analysis, where thickness, adhesion, and defects are measured on a cross-section.

Impact testing

Charpy V-notch impact testing to ASTM E23 measures toughness, the energy a material absorbs when it is struck rather than pulled, and it is the test that exposes brittle behaviour a tensile test will not. Results are reported as absorbed energy with lateral expansion and percent shear fracture, and can be run as a temperature series to locate the ductile-to-brittle transition, which is the number that decides whether a steel is fit for cold service.

Transverse tensile specimens cut across a weld are part of the mechanical testing behind a weld procedure or welder qualification under ASME Section IX or AWS D1.1, and impact specimens can be notched in the weld metal or the heat-affected zone where the code calls for them.

Testing welds and components

Where a specimen is taken from decides what it means. Orientation relative to the rolling direction, position relative to the weld and its heat-affected zone, and depth through the wall all change the result, so specimen layout is planned before anything is cut, and recorded with the results. For failure work the layout usually pairs a specimen from the failed region with one from sound material on the same component, which turns a single number into a comparison.

Where it fits with the rest of the work

Mechanical results are most useful next to the metallurgy that explains them. A low yield strength means one thing on its own and something far more specific when the microstructure shows a missed heat treatment. A tensile test that fails a specification is the beginning of a failure analysis, not the end of the job. Where a component cannot be sectioned at all, Automated Ball Indentation derives yield and tensile properties in place, non-destructively, and hardness testing gives a fast, local strength indication on prepared cross-sections.

What we need from you

• The material specification and grade the part was bought to, if known
• Enough material to machine the specimens, or the component itself so we can plan the layout
• The service conditions that matter, particularly minimum design temperature for impact work
• The question behind the request: qualification, spec compliance, fitness-for-service, or failure investigation