ASTM E855 Test Fixture

Description

ASTM E855- Standard Test Methods for Bend Testing of Metallic Flat Materials for Spring Applications Involving Static Loading

 

ASTM E855 describes three test methods  for determining the modulus of elasticity in bending, the bending proof strength, and the offset yield strength in bending

of  metallic strips or sheets intended for the use in flat springs:

Test Method A—A cantilever beam test,

Test Method B—A three-point beam test (that is, a beam resting on two supports and centrally loaded)

Test Method C—A four-point beam test (that is, a beam resting on two supports and loaded at two points equally spaced from each support).

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ASTM E855 / Significance and Use

Measurements of bending proof strength, offset yield strength in bending, and modulus of elasticity in bending should be made for materials whose principal

stressing mode is bending.

For many materials, the tensile and compressive moduli are somewhat different.

Since the modulus of elasticity in bending is a combination of the tensile and compressive moduli, it is often different from each of them.

Precise measurements of the modulus of elasticity in bending offset yield strength in bending, and bending proof strength require due regard for numerous

variables that can affect their determination.

These include ;

(1) Material characteristics such as specimen orientation with respect to the Rolling direction, grain size, residual stresses, previous strain history, dimensions and

specimen preparation, orientation of deformed grains relative to the direction of the normal stress;

(2) Test conditions, such as temperature, temperature variations, condition of the test equipment, and adherence to the test procedure.

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ASTM E855 / TEST METHOD A—CANTILEVER BEAM TEST

This test method covers the determination of the modulus of elasticity in bending and the offset yield strength in bending of flat metallic strips or sheets

for spring applications.

The test procedure involves measurements of the applied moment and the corresponding deflection angle of a cantilever beam.

The thickness range covered is 0.015 in. to 0.130 in. (0.38 mm to 3.30 mm).

This test method should not be used for nonlinear elastic materials.

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ASTM E855 / TEST METHOD B: THREE-POINT BEAM TEST

ASTM E855 / TEST METHOD C: FOUR-POINT BEAM TEST

These test methods cover the determination of the modulus of elasticity in bending and the bending proof strength of flat metallic strips or sheets for spring

applications.

The test methods consist of deflection tests of a simple beam configuration subjected to either three- or four-point symmetrical loading.

The thickness range covered is 0.010 in. to 0.050 in. (0.25 mm to 1.3 mm).

Thickness ranges outside of those specified may be agreed upon between suppliers and users.

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ASTM E855 / Apparatus

The apparatus consists of two adjustable supports and a means for measuring deflection or curvature and for applying force.

Supports—The supports should have a 60° angle with a radius of 0.005 in. (0.13 mm) at the supporting edge.

One knife edge should be straight, and the other should be convex with a 0.50 in. (13 mm) radius of curvature.

Their mutual separation should be adjustable along the specimen longitudinal axis

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Testing Machines—In determining the suitability of a testing machine, the testing machine should be verified under conditions approximating those under

which the tests will be made, together with the force applicators, in accordance with Practices ASTM E4.

Corrections may be applied for systematic errors in force.

Any cumulative error in the machine loading system shall not exceed 1.0 %.

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Summary of Test Methods

The test specimen is loaded as a simple beam in either three- or four-point symmetrical loading.

The modulus of elasticity in bending is obtained by force-deflection measurements at stresses below the elastic limit in bending.

The bending proof strength is obtained by a stepwise increasing loading–unloading sequence carried out until a specified permanent strain is measured on unloading.

*** Before conducting ASTM E855 , it is important to read the entire specification. Standards can be obtained from appropriate standard authorities.

 

***PARSROS  offers several types of grips and fixtures which will enable you to perform a variety of tests

  that are accurate and repeatable.