ASTM E238
Pin-Type Bearing Test Fixture for Metallic Sheet and Plate
ASTM E238 Bearing Test Fixture – Universal Grip Data Sheet (PDF)
ASTM E238 is the standard test method for pin-type bearing test of metallic materials. It answers a question every riveted, bolted or pinned joint raises: how much load can the edge of a hole carry before it yields or tears out? A close-fitting cylindrical pin, harder and stronger than the specimen, is passed through a hole set a defined distance from the specimen edge and loaded in tension while the elongation of the hole is recorded. Universal Grip builds the E238 bearing fixture as a heat-treated clevis with hardened, ground pins in a range of diameters, with provision for a bearing extensometer and a matching grip for the other end of the specimen.
What ASTM E238 Measures
The method determines bearing ultimate strength, the maximum bearing stress the material sustains, and bearing yield strength, the bearing stress at which a specified limiting deviation from proportionality between bearing stress and bearing strain is reached (commonly taken at 2 % offset of the hole deformation). Bearing stress is the pin load divided by the projected bearing area, pin diameter times specimen thickness. Results depend on the edge distance to hole diameter ratio e/D, with e/D of 1.5 and 2.0 the most commonly tested conditions, and on the diameter to thickness ratio, so these are reported with the data. The standard notes that incidental lubricant on the bearing surfaces can significantly lower the measured bearing yield strength. ASTM E238 is the metals counterpart of ASTM D5961 for composite bearing response, and inch-pound units are the standard with SI for information.
How the ASTM E238 Test Works
Machine a flat specimen of the required width and thickness with a drilled or reamed hole at the specified edge distance; the pin diameter is matched to the hole within the standard's tolerance.
Measure specimen thickness and pin diameter; their product is the bearing area used for stress.
Degrease pin, hole and clevis faces so no lubricant alters the yield reading.
Insert the specimen into the clevis, pass the pin through the clevis and the hole, and grip the far end of the specimen in a wedge or pin grip.
Attach the bearing extensometer across the pin and a reference point on the specimen to measure hole elongation.
Load in tension at the rate the standard specifies and record pin load against bearing deformation until maximum load or tear-out.
Calculate bearing yield strength from the offset on the load–deformation curve and bearing ultimate strength from the maximum load.
Specimens and Setup
The clevis must load the pin symmetrically; a single-shear arrangement bends the pin and the specimen and lowers the apparent bearing strength.
Pin hardness and stiffness matter: a pin that yields or bends gives a bearing yield value for the pin, not the sheet.
Keep e/D and D/t within the ranges the current edition specifies and report them; results at e/D of 1.5 are not interchangeable with e/D of 2.0.
Run the unrestrained condition the standard describes, with the specimen faces not clamped at the hole, unless your specification calls otherwise.
Crosshead rates on the order of 0.05 in./min are typical; confirm the rate against the current edition and your material specification.
Universal Grip ASTM E238 Fixture
Hardened, ground bearing pins in a range of diameters
Clevis design applies load symmetrically to the specimen hole
Provision for a bearing extensometer to measure hole elongation
Supports a range of edge-distance-to-diameter ratios
Heat-treated alloy steel clevis
Load capacity 50 kN standard; higher capacities on request
Paired with a wedge or pin grip on the opposite specimen end; clevis pin or threaded adapters to suit your frame
Applications
Aerospace sheet and plate alloys
Bolted and riveted joint design data
Aluminum and titanium alloy qualification
Material allowables development
Related Standards and Products
Send us your specimen dimensions, required capacity and machine connection through our contact page and we will quote an ASTM E238 pin-type bearing fixture. Request a quote
ASTM E238 FAQ
What is bearing yield strength?
The bearing stress at which the material reaches a specified limiting deviation from proportionality of bearing stress to bearing strain, found by an offset construction on the load versus hole-elongation curve. Bearing ultimate strength is simply the maximum bearing stress reached.
What is e/D and why does it matter?
The ratio of edge distance (hole center to specimen edge) to hole diameter. Small e/D specimens fail by shear-out at the edge; larger e/D specimens fail by bearing deformation of the hole. E238 results are always reported with e/D, and 1.5 and 2.0 are the usual conditions.
Do I need an extensometer?
For bearing yield strength, yes: the offset is applied to hole elongation, which must be measured across the pin and the specimen. Bearing ultimate strength needs only the maximum load, pin diameter and thickness.
Is E238 the same as ASTM D5961?
They test the same joint behavior but for different materials. E238 covers metallic sheet and plate with an unrestrained pin; D5961 covers polymer matrix composite laminates and includes clamped (bolted) procedures as well as pin bearing.