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ASTM E28.04 Workshop. Workshop on the Speed of Testing May 21, 2007 Norfolk, VA. Schedule of Presenters. Earl Ruth, Tinius Olsen Jim Hartman, Honeywell Carpenter Representative Byron Skillings, Ladish Len Manning, Dofasco Sue Morford, Howmet

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ASTM E28.04 Workshop

Workshop on the

Speed of Testing

May 21, 2007 Norfolk, VA


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Schedule of Presenters

Earl Ruth, Tinius Olsen

Jim Hartman, Honeywell

Carpenter Representative

Byron Skillings, Ladish

Len Manning, Dofasco

Sue Morford, Howmet

Rich Brazill, Alcoa


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ASTM E28.04 Workshop

Ballot Item:

Revise ASTM E 8 Standard Test Methods for Tension Testing of Metallic Materials by replacing existing section 7.6

Rationale:

For years the limitation on yield speed in E 8 has been in terms of rate of stressing. The wide range of acceptable test speeds currently in E 8 is another source of non reproducibility. This change to E 8 attempts to simplify the speed of testing section, make it more clear as to how to control today’s testing machines, and improve the reproducibility of tests.


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ASTM E28.04 Workshop

Earl Ruth, Tinius Olsen

Proposed Change to

Standard E8 Speed of Testing Section


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Existing

7.6.3 Speed of Testing When Determining Yield Properties—Unless otherwise specified, any convenient speed of testing may be used up to one half the specified yield strength or up to one quarter the specified tensile strength, whichever is smaller. The speed above this point shall be within the limits specified. If different speed limitations are required for use in determining yield strength, yield point elongation, tensile strength, elongation, and reduction of area, they should be stated in the product specifications. In the absence of any specified limitations on speed of testing, the following general rules shall apply:

7.6.3.1 The speed of testing shall be such that the forces and strains used in obtaining the test results are accurately indicated.

7.6.3.2 When performing a test to determine yield properties, the rate of stress application shall be between 1.15 and 11.5 MPa/s

(10 000 and 100 000 psi/min).

Proposed

7.6.3 Speed of Testing When Determining Yield Properties—Unless otherwise specified, the following speeds shall apply. Any convenient speed of testing may be used up to one half the specified yield strength or up to one quarter of the specified tensile strength, whichever is smaller. The speed above this point shall be within the limits specified. If different speed limitations are required for use in determining yield strength, yield point elongation, tensile strength, elongation, and reduction of area, they should be stated in the product specifications. In the absence of any specified limitations on speed of testing, the following rules shall apply:

7.6.3.1 The speed of testing shall be such that the forces and strains used in obtaining the test results are accurately indicated.

7.6.3.2 When performing a test to determine yield properties, the strain rate or the crosshead speed shall be 0.00025 mm/mm/s (0.015 inches/inch/min) +/- 20%.

Tinius Olsen - Changes to ASTM E8


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Tinius Olsen - Test Matrix

  • 1 sheet steel specimen tested on

    4 different testing machines at

    6 different speed control settings

  • 4 Machines

    • 5kN single screw machine w/ wedge grips

    • 50 kN twin screw machine w/ wedge grips

    • 300 kN Hydraulic machine w/ wedge grips

    • 150 kN twin screw machine w/ hydraulic grips


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Tinius Olsen -6 Pre-Yield Test Speeds

  • 1 – Existing E 8 Upper Limit using a position rate to achieve 100,000 psi/min

    • (Position rate required varied with machine stiffness from 0.039 to 0.217 inches/min)

  • 2 – Existing E 8 Lower Limit using a position rate to achieve 10,000 psi/min

    • (Position rate required varied with machine stiffness from 0.004 to 0.025 inches/min)

  • 3 – Existing E 8 Upper Limit using a strain rate of 0.0033 /min

    • (Strain Rate corresponding to a Stress Rate of 100,000 psi per minute for steel with a Modulus of Elasticity of 30X 106 psi)

  • 4 – Existing A 370 Upper Limit using a position rate of 0.175 inches/min

    • (ASTM A370 rate 1/16 of an inch per inch of reduced section per minute. Position rate of 0.175 in/min = 0.0625 /min X 2.8 inches)

  • 5 – Proposed new rate using position control

    • (Position rate of 0.042 in/min = 0.015 /min X 2.8 inches)

  • 6 - Proposed new rate using strain rate control

    • (0.015 /min)


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    Tinius Olsen -Test Notes

    • The Stress Rate was determined in the elastic portion of the curve.

    • The strain and position rates were determined at the 0.2% Offset



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    Tinius Olsen - Strain Rate vs. Test Type

    • 1 – Existing E 8 Upper Limit using a position rate to achieve 100,000 psi/min

    • 2 – Existing E 8 Lower Limit using a position rate to achieve 10,000 psi/min

    • 3 – Existing E 8 Upper Limit using a strain rate of 0.0033 /min

    • 4 – Existing A 370 Upper Limit using a position rate of 0.175 inches/min

    • 5 – Proposed new rate using position control at 0.042 inches/min

    • 6 - Proposed new rate using strain rate control at 0.015 /min


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    Tinius Olsen - Effect on Yield Strength

    • 1 – Existing E 8 Upper Limit using a position rate to achieve 100,000 psi/min

    • 2 – Existing E 8 Lower Limit using a position rate to achieve 10,000 psi/min

    • 3 – Existing E 8 Upper Limit using a strain rate of 0.0033 /min

    • 4 – Existing A 370 Upper Limit using a position rate of 0.175 inches/min

    • 5 – Proposed new rate using position control at 0.042 inches/min

    • 6 - Proposed new rate using strain rate control at 0.015 /min


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    Tinius Olsen – Production Considerations

    • 1 – Existing E 8 Upper Limit using a position rate to achieve 100,000 psi/min

    • 2 – Existing E 8 Lower Limit using a position rate to achieve 10,000 psi/min

    • 3 – Existing E 8 Upper Limit using a strain rate of 0.0033 /min

    • 4 – Existing A 370 Upper Limit using a position rate of 0.175 inches/min

    • 5 – Proposed new rate using position control at 0.042 inches/min

    • 6 - Proposed new rate using strain rate control at 0.015 /min


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    Tinius Olsen - Conclusions

    • We should be able to reduce interlaboratory scatter by specifying the default ASTM E 8 speed in terms of Strain Rate instead of Stress Rate.

    • We can get comparable results by controlling the test in position rate or strain rate.

    • ASTM A370 speed of 1/16 of an inch per inch of reduced section is too fast for some machines.

    • Controlling position rate to achieve a 0.005 /min strain rate (popular in many aerospace specifications) makes for a very long test time.

    • A strain rate of 0.015 /min which allows both position control and strain rate control is reasonable because it can be achieved on machines without closed-loop strain rate control, there is good agreement between the position rate and the strain rate, and production testing is not harshly impacted.


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