A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. Scope 1. SI units are provided for information only. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use.

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A number in parentheses indicates the year of last reapproval. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.

It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Referenced Documents2. The deviation is expressedin terms of strain. Current edition approved April 1, Published April Originallyapproved in Last previous edition approved in as E — United States Significance and Use4.

For many materials, thetensile and compressive moduli are somewhat different. Sincethe bending modulus is a combination of the tensile andcompressive moduli, it is often different from each of them. These include 1 characteristics such as specimen orientation with respect to therolling direction, grain size, residual stresses, previous strainhistory, dimensions and specimen preparation, orientation ofdeformed grains relative to the direction of the normal stress;and 2 test conditions, such as tem-perature, temperature variations, condition of the test equip-ment and adherence to the recommended test procedure.

Fundamental Assumptions5. The test procedure involves measurements of the appliedmoment and the corresponding angle of deflection of acantilever beam.

The thickness range covered is 0. This test method is not applicable fornonlinear elastic materials. Summary of Test Method7. When the maximum desireddeflection is reached, the bending moment is removed and thepermanent set angle resulting from the bend is recorded.

The bending momentand deflection data obtained are normalized with regard tospecimen geometry. These normalized terms are then plotted toproduce a stress-strain curve for cantilever bending that issimilar to a stress-strain curve for tension or compression. Themodulus of elasticity in bending and the offset yield strength inbending are determined from the bending stress-strain curveusing a procedure similar to that used for tensile stress-straincurves.

Significance and Use8. These values are useful to spring designers todetermine spring constants and permissible maximum deflec-tion of flat springs. It should be recognized that the offset yieldstrength in bending as determined by this test method is notnecessarily equal to either the yield strength in tension, thecyclic yield strength in bending, or to bending proof strengthsdetermined by other methods.

These approximations are explained in Appendix X1. Actual rate of stressing will depend on the specimenwidth and thickness and the weight of the pendulum. The specimen holder isrotated about point O. The4The Olsen Stiffness Tester meets the requirements of this test method. For apendulum system Fig. The loading pinhas a diameter of 0. The reason for specifying the pin diameter and pin location isexplained in Appendix X1. Test Specimens Specimenorientation relative to the rolling direction must be identified.

Specimen curvature due to coil set is permitted if the ratio ofthe radius of curvature to thickness exceeds However, thespecimen cannot be twisted or wavy. No attempt shall be madeto flatten or straighten specimens prior to testing.

Care shall beexercised not to alter the microstructure during specimenpreparation. All burrs shall be removed before testing. Testingmachine capacity will determine the maximum allowablespecimen size. The thickness shall be measured at thefour corners and the center of the specimen.

Hence, thickness is by far the most critical measure-ment in the determination of the modulus. NOTE 1—For example, an error in the thickness measurement of Additional sources of uncertainty are the preci-sions of determining the span length, the specimen width, and the beamdeflection. The width shall be measured at both ends and the center of thespecimen. Specimens having width variations greater than0. The minimumspecimen width shall be 0. The specimen widthshall not extend beyond the vise or the loading pin.

Set the bendingspan to 2. When contact is made, the angular deflectionindicator shall be set to indicate zero angle. The specimen then shall be unloaded. The permanent set angleresulting from the bend shall be read on the angular deflectionscale with the specimen contacting the loading pin at zero load.

For specimens having an initial residual curvature, halfof the specimens shall be tested with the concave surfacefacing upwards and half with the convex surface facingupwards.

All specimens shall be deflected to the same maxi-mum angle.


ASTM E 855



ASTM E855 Bend Testing of Metallic Flat Materials for Spring Applications




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