Test Locations for Tensile Testing ASTM A370 1

[LEB1]

Regarding Test locations for Tensile Test sample extraction.

ASTM A370 indicates Testing at 1/4T
API6A indicates testing within the 1/4T envelope.

Can any direct me to a definitive explanation of the 1/4T envelope , preferably with drawings.

Is there any criteria that depicts where the 1/4T envelope starts/ and finishes? for example on 100mm Sq sample the 1/4T would be 25mm from the surface and the 1/4T envelope would extend to anywhere within 25mm from surface to the centre of the material.

if this sample was then 200mm sq - the 1/4T would be 50mm from surface - would there be a region in the centre of 50-mm sq where the 1/4T envelope stops and this becomes 1/2T

Regards
LEB1

 

[redpicker]

Perhaps I misunderstood the requirements all these years.

I thought 6A required testing beneath the 1/4T envelope. That is, on a 4" square test coupon, the centerline of the specimen can be no closer than 1" to the surface. If you had a 8" square test coupon, the centerline can be no closer than 2" to any surface.

That is, the 1/4T envelope is an envelope from the surface to 1/4 of the thickness of the part. As long as the specimen is below this envelope, the test location is acceptable.

I thought 6A had a drawing depicting this.

There can be no specimens taken below the 1/2T envelope, since you can not get farther away from a surface than 4" on an 8" square coupon.

 

[LEB1]

Hi Redpicker.

APi 6A does indeed have drawings representing the areas in question.

I am seeking to clarify the 1/4T envelope location. In API 6A 5.6.4.1 it states that the test specimens shall be removed from the TC such that their longitudinal axis is wholly within the centre core 1/4T envelope of a solid..
Thus on a 100mm square sample the actual 1/4T location would be 25mm from surface and the envelope would be 25mm from surface to the centre of the material. In API I think it is slightly confusing where they have shown in figure 3 the Square section appears with a 1/2T designation. This is further backed up in VGS 24.2.1.14 where there is reference to 1/4T envelope but no reference to 1/2T

 

[metengr]

Is there any criteria that depicts where the 1/4T envelope starts/ and finishes? for example on 100mm Sq sample the 1/4T would be 25mm from the surface and the 1/4T envelope would extend to anywhere within 25mm from surface to the centre of the material.

Because a test coupon is required to demonstrate compliance of heat treatment performed to a part, the test coupon (TC) is based on an Equivalent Round (ER) factor as described in 5.6.2. The ER must be equal to or greater than the dimensions it qualifies.

So, the T/4 envelope and T/2 is defined for rectangle or plate shown in Figure 3 for an ER of 1.5T.