<p>According to our materials experts, you should always be careful interpreting the start of the force-displacement diagram. It is possible that the test needs to "set" itself, important issues are:</p>

<ul>
<li>the clamping of the test articles in the test bench vices</li>
<li>alignment of the test article in the test bench</li>
<li>size of the test articles (the load suggests small test articles/small diameter)</li>
<li>how is displacement measured (displacement/elongation sensors "slip" easily depending on the expertise of the operator)</li>
<li>artifacts in the test article?</li>
</ul>

<p>Instead of proceeding the test till rupture (prior to the in-elastic/plastic region), it would have been beneficial if the test had been stopped at about 8&nbsp;kN and relaxed to 0&nbsp;kN to commence a new test.</p>

<hr>

<p><em>From my own experience with creep test articles we see similar issues and apply a displacement offset so that the "second section" (using your words) is extrapolated to zero load. Usually this is just a few hundredths or tenths of a mm. In this case you could shift the whole diagram 0.3&nbsp;mm to the right by applying a similar offset of about -0.3&nbsp;mm.</em></p>

<p><a href="https://i.sstatic.net/sZLRB.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/sZLRB.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2020-01-06T15:27:13.087Z
2020-02-06T22:55:49.000Z
2020-02-06T22:55:49.000Z
0scar
<p>When I do a tensile test on 17-4 PH stainless steel, the stress-strain curve is very strange, two sections of Young’s modulus appeared. What is going on? The sample is made by SLM.</p>

<p><a href="https://i.sstatic.net/5mZFx.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/5mZFx.jpg" alt="17-4 PH stainless steel load vs. displacement curve"></a></p>

<metal-parts><slm><part-testing>
17-4 PH Tensile Test
user17488
# 17-4 PH Tensile Test

(Asked by: username_0 on 2019-12-18)

When I do a tensile test on 17-4 PH stainless steel, the stress-strain curve is very strange, two sections of Young’s modulus appeared. What is going on? The sample is made by SLM.

[![17-4 PH stainless steel load vs. displacement curve](https://i.sstatic.net/5mZFx.jpg)](https://i.sstatic.net/5mZFx.jpg)

**Tags:** metal-parts, slm, part-testing

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## 1 answers

### Answer by username_1 on 2020-01-06. Score: 2

According to our materials experts, you should always be careful interpreting the start of the force-displacement diagram. It is possible that the test needs to "set" itself, important issues are:

* the clamping of the test articles in the test bench vices
* alignment of the test article in the test bench
* size of the test articles (the load suggests small test articles/small diameter)
* how is displacement measured (displacement/elongation sensors "slip" easily depending on the expertise of the operator)
* artifacts in the test article?

Instead of proceeding the test till rupture (prior to the in-elastic/plastic region), it would have been beneficial if the test had been stopped at about 8 kN and relaxed to 0 kN to commence a new test.

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*From my own experience with creep test articles we see similar issues and apply a displacement offset so that the "second section" (using your words) is extrapolated to zero load. Usually this is just a few hundredths or tenths of a mm. In this case you could shift the whole diagram 0.3 mm to the right by applying a similar offset of about -0.3 mm.*

[![enter image description here](https://i.sstatic.net/sZLRB.png)](https://i.sstatic.net/sZLRB.png)


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