Additive Manufacturing Tensile Properties Testing: Standards, Specimens, Methods, and Applications

Additive manufacturing tensile properties testing is the core mechanical evaluation used to qualify metal and polymer 3D-printed materials for demanding engineering applications. By measuring tensile strength, yield strength, elongation, and modulus along different build orientations, accredited third-party laboratories help manufacturers demonstrate compliance with internationally recognized standards such as ISO 6892-1, ASTM E8/E8M, and ASTM D638. This article explains the specimen types, test items, methods, and industry applications of tensile testing for additively manufactured parts.

Technical Overview

Additive manufacturing (AM), commonly known as 3D printing, builds components layer by layer through processes such as laser powder bed fusion (LPBF), electron beam powder bed fusion (EB-PBF), directed energy deposition (DED), binder jetting, and material extrusion. This layer-wise consolidation produces directionally dependent microstructures, lack-of-fusion porosity, residual stresses, and surface roughness that differ fundamentally from wrought or cast materials. As a result, tensile testing is the primary and most widely accepted method for evaluating the structural performance of AM materials and for qualifying AM processes before parts enter service.

Because AM materials can exhibit significant anisotropy, tensile properties must be characterized with respect to the build direction. Specimens are typically manufactured in at least two orientations: horizontal or in-plane (perpendicular to the build direction) and vertical (parallel to the build direction). Test results are interpreted together with the feedstock specification, machine parameters, build layout, and any post-processing operations such as stress relief, hot isostatic pressing (HIP), or solution treatment and aging.

The main standards framework for AM tensile testing consists of the following documents:

• ISO 6892-1 and ASTM E8/E8M for tensile testing of metallic materials at room temperature
• ISO 6892-2 and ASTM E21 for tensile testing of metallic materials at elevated temperature
• ASTM D638 and ISO 527-2 for tensile properties of rigid plastics used in polymer AM
• ISO/ASTM 52900 for additive manufacturing terminology and general principles
• ASTM F3122 (now superseded by ISO/ASTM 52927) for evaluating mechanical properties of metal materials made via additive manufacturing
• Material-specific AM specifications such as ASTM F3001 (Ti-6Al-4V ELI) and ASTM F3055 (IN718) for powder bed fusion
• GB/T 228.1, the Chinese national adoption of ISO 6892-1, for domestic compliance programs

Testing Samples

Machined Metallic Specimens

Machined dog-bone specimens are the reference approach for determining the intrinsic tensile properties of AM metals. Flat sheet-type or cylindrical proportional specimens are manufactured per ASTM E8/E8M or ISO 6892-1, with blanks printed slightly oversized and then machined to final dimensions. Machining removes the as-built surface, near-surface porosity, and partially melted particles, allowing the bulk material properties of the printed structure to be measured. Specimen blanks must be clearly identified with their build orientation, build plate position, and post-processing condition.

As-Built Specimens

As-built specimens retain the original printed surface and gauge section geometry directly from the machine. Their results reflect the actual performance of parts used without surface finishing, which is valuable for design allowables and lot acceptance testing. Because surface roughness acts as a stress concentrator, as-built specimens generally show lower elongation and fatigue-sensitive behavior than machined specimens, and the two data sets should be reported separately.

Witness Coupons and Part-Attached Specimens

For production quality control, witness coupons are co-built on the same build plate as the actual components, often at defined reference positions, so that each build lot is represented. Small tensile coupons may also be integrated into the part or its support structure and removed after printing. This practice, recommended in AM qualification frameworks of the ISO/ASTM 52900 series and material-specific specifications, links every delivered part to a verified mechanical test record without sacrificing the part itself.

Polymer AM Specimens

Tensile specimens for polymer AM processes such as FFF/FDM, SLA, and SLS are produced per ASTM D638 (Types I through V) or ISO 527-2 (specimens 1A and 1B). Moisture-sensitive materials such as polyamide (nylon) are conditioned in standard atmospheres per ISO 291 before testing. Print orientation, layer height, infill strategy, and raster angle are documented because they strongly influence the measured strength and ductility.

Testing Items

A complete AM tensile test program quantifies the following properties, each reported together with build orientation and post-processing state:

• Ultimate tensile strength (Rm or UTS): the maximum engineering stress sustained before fracture
• Yield strength (Rp0.2): the 0.2 percent offset proof stress used for design calculations
• Tensile elastic modulus (E): Young's modulus determined from the linear elastic region
• Fracture elongation (A or A50 mm): total plastic extension at break, a key indicator of ductility
• Uniform elongation (Ag): elongation at maximum force, before necking begins
• Reduction of area (Z): a ductility measure for cylindrical specimens, sensitive to internal porosity
• Poisson's ratio: optionally measured using bidirectional extensometers or digital image correlation (DIC)
• Orientation anisotropy ratio: the ratio of in-plane to build-direction properties, critical for AM design
• Elevated-temperature tensile properties: Rm, Rp0.2, and elongation at defined service temperatures

Testing Methods

Tensile testing of AM materials follows the controlled workflow of the applicable metallic or polymer standard, with additional steps that address the specifics of printed material.

• Specimen receipt and traceability: orientation, build identification, powder lot, and heat treatment records are verified before testing
• Dimensional inspection: gauge section cross-section is measured at multiple locations to compute the true stress-bearing area
• Post-processing documentation: stress relief, HIP, solution and aging treatments are recorded because they alter strength and ductility
• Alignment verification: gripping and load-string alignment are checked per practices such as ASTM E1012 to limit bending strains in the gauge section
• Strain rate control: tests use stress-rate or strain-rate control per ISO 6892-1 Method A or the rate ranges of ASTM E8/E8M, since AM metals can be strain-rate sensitive
• Strain measurement: calibrated extensometers of a defined accuracy class, clip-on or automated, are used for modulus and proof stress determination; full-field DIC is increasingly applied to capture anisotropic strain localization
• Modulus determination: performed with strain-rate control in the elastic region using an averaged method over a defined stress interval
• Fracture and post-test evaluation: fractured halves are reassembled to measure final elongation; fracture surfaces and section contraction are examined for porosity and layer-bonding defects
• Elevated-temperature testing: performed per ISO 6892-2 or ASTM E21 with calibrated furnaces and temperature soaking for high-temperature AM alloys
• Reporting: results are reported per orientation, and statistical summaries are produced when multiple replicates are tested

For polymer specimens, crosshead speed, grip pressure, and specimen conditioning are controlled per ASTM D638 or ISO 527, and modulus is determined with an extensometer rather than crosshead displacement to avoid system compliance errors.

Applications

Tensile properties testing of additively manufactured materials supports qualification, certification, and production release across many industries:

• Aerospace: qualification of Ti-6Al-4V, IN718, AlSi10Mg, and Scalmalloy-type alloys for brackets, structural fittings, and engine components, with orientation-dependent allowables used in structural analysis
• Medical devices: verification of titanium and cobalt-chromium implant materials against material specifications and regulatory submission requirements
• Automotive and motorsport: validation of lightweight topology-optimized parts, conformal cooling inserts, and rapid tooling components
• Energy and turbomachinery: assessment of repair deposits made by directed energy deposition on blades, vanes, and valve components
• Defense and marine: material acceptance for mission-critical printed hardware exposed to static and environmental loads
• Research and development: benchmarking new alloys, powders, machines, and parameter sets, and generating design allowables for the ISO/ASTM 52900 framework and material-specific specifications
• Production quality control: routine witness-coupon testing that provides lot-level evidence of stable machine performance

FAQ

Why do additively manufactured parts show anisotropic tensile properties?

Layer-by-layer consolidation creates elongated grains, directional melt-pool boundaries, and layer interfaces, so the bonding between layers differs from the bonding within a layer. Vertical specimens built parallel to the build direction typically show lower elongation, and sometimes lower strength, than in-plane specimens, which is why both orientations must be tested.

Which build orientations should be tested?

At minimum, specimens should be built perpendicular to the build plate (vertical, Z) and parallel to it (horizontal, X or Y). For thick sections and DED parts, diagonal orientations such as 45 degrees are frequently added to map the full anisotropy of the process.

Should machined or as-built specimens be used?

Machined specimens define the intrinsic capability of the material and are used for material qualification and comparison with specifications. As-built specimens reflect real part surfaces and are used for design allowables and lot acceptance. A complete program typically includes both.

How do heat treatment and HIP affect tensile results?

Stress relief stabilizes dimensions with limited strength change. Solution treatment and aging can raise yield strength substantially in precipitation-hardenable alloys such as IN718 and 17-4PH. HIP closes internal porosity, usually improving elongation and fatigue-related behavior. All post-processing must be documented with the test report.

How many specimens are needed per test condition?

For screening and process development, a minimum of three valid replicates per orientation is common practice. For statistically based design allowables or certification programs, larger data sets are required to characterize the distribution of strength and elongation for the specific machine, material, and process.

Which standards apply to polymer AM tensile testing?

Polymer AM parts are tested per ASTM D638 or ISO 527-2, using specimen types appropriate to the available print volume and material ductility, with conditioning per ISO 291. Print parameters and orientation are always reported alongside the mechanical results.