What is Yield stress: Definition and 25 Discussions

In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible and is known as plastic deformation.
The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically. The yield strength is often used to determine the maximum allowable load in a mechanical component, since it represents the upper limit to forces that can be applied without producing permanent deformation. In some materials, such as aluminium, there is a gradual onset of non-linear behavior, making the precise yield point difficult to determine. In such a case, the offset yield point (or proof stress) is taken as the stress at which 0.2% plastic deformation occurs. Yielding is a gradual failure mode which is normally not catastrophic, unlike ultimate failure.
In solid mechanics, the yield point can be specified in terms of the three-dimensional principal stresses (

σ

1

,

σ

2

,

σ

3

{\displaystyle \sigma _{1},\sigma _{2},\sigma _{3}}
) with a yield surface or a yield criterion. A variety of yield criteria have been developed for different materials.

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1. Calculating Capacity of Steel Rack: Yield Stress Issues

Hi guys. Recently I've been assigned to know / calculate the capacity of the racks in our section. Our racks has layered steel pipes that are carrying the loads. After actual testing it can carry a load around 25 tons after yielding or having a bend. So my next step was to calculate for its...
2. Does strain rate ever decrease yield stress?

I've been digging through literature the last few days, and I'm starting to wonder if increasing strain rate EVER decreases yield stress? I found anomalies which increase it with increasing temperature. But I cant' find the reverse, so I was wondering if it was possible?
3. Determining yield stress via a bar subjected to tensile force

Homework Statement Homework Equations All Equations Below The Attempt at a Solution [/B]
4. Another one about Yield Stress....

Hi Forum, I´m happy I found this forum... I hope someone can answer my (simple) question: According to this thread https://www.physicsforums.com/threads/calculating-0-2-proof-stress-of-aluminium.206648/ on page 2 the stress/strain diagram is not the same as force/elongation. Due to the constant...
5. Desai Yield Surface, Parameters

Hey guys, Desai Yield Surface: I have a hard time understanding the parameters of the model for soils. If I have three principle stresses, σ1, σ2, σ3. And R is defined as the Tri-axial strength in tension, how would I define R. Lastly can I just say that I1 = σ1+σ2+σ3 J2= 1/6 * ((σ1-σ2)2...
6. Yield stress vs critical load stress

Homework Statement In Euler's theory , it's stated that the critical stress of beam is always larger than the yield stress of beam ...I don't really undertstand the differnce between them . Critical stress is defined as the stress that the mximum stress applied before the beam starts to...
7. Difference between 'plastic yielding' & plastic strength?

I am going through a literature where the terms like ( 'plastic yielding' , 'plastic yield strength', plastic strength' and 'plastic stress') are regularly used and I am confused. Are they different and if yes then how each term differs from the other? I also want to know relation of plastic...
8. How Do X-Braces Affect Indeterminate Truss Analysis?

Homework Statement For a larger project we had to redesign a truss to prevent certain members going beyond yield stress. I've found that due to the nature of the reaction forces and the supports used, the only way to do this is to introduce an X-brace in the bay nearest the supports (as well...
9. Reliability of Upper/lower yield point in tensile test.

Some metal give two yield point in stress strain diagram. One is called Upper yield point and Lower yield point. Why lower yield point is considered as more reliable. I can think of Upper yield point is much more dependent upon experimental apparatus settings. So why lower yield point is much...
10. Engineering Stress increases after yield stress?

I need to know why the Engineering stress increases after reaching the yield stress point, and continues to increase until reaching the UTS. Am I correct when I remember that there is strain hardening that occurs along the region from Yield stress to the Ultimate tensile stress? Engineering...
11. Brittle Materials: Bending Yield Strength

It seems to me that the ultimate strength of a brittle material can be easily determined by a bending test, but what about the yield? In the brittle regime, I can see how you couldn't, since the sample would fail before it would flow significantly. However, brittle materials can be made to flow...
12. Differential Yield Stress and Von Mises Criterion

If I have the differential yield stress σd=(σ1-σ3) for a material, what can I derive from that for use with the von mises criterion? Do I have k=0.5×(σ1-σ3) or σy in axial tension, where σ3 = 0? Essentially is my axial yield stress = σd or √3 × σd /2? (in plane stress)
13. Calculating Stress Values for Cylindrical Steel Sample

I have a cylindrical steel sample tested in tension. It's cross-sectional area is 500 mm2. I am also told that: Force at yield = 205 kN Maximum force = 258 kN Force at fracture = 200 kN I am asked to calculate the yield stress, ultimate tensile stress and fracture stress if the reduction of...
14. How do i calculate or find out the yield stress of sugarcane?

Hi, from what I know, the crushing force for sugar cane is somewhat similar to pine wood which is about 40 MPA. But since there's water content in it, I need to readjust the yield stress for to crush the sugarcane. I've tried googling it but couldn't find much useful information. Anyone knows...
15. Obtaining yield stress knowing only Poisson's ratio and UTS?

Greetings all, I have been trying to find a method of calculating the yield stress for a material when only given; -The loading type (Two bars soldered together in tension) -The dimensions of the shaft and solder (ie thickness of solder, length, cross sectional area) -The Ultimate...
16. Initial yield stress Vs. tensile strength

Are those the same? if not, how do I calculate the initial yield stress from the tensile strength? all the materials properties I see on the web only specify tensile strength, and I need the initial yield stress as an input on non-linear FEA analysis. Is it possible to extract the initial yield...
17. Finding a max load from the yield stress

1. Homework Statement I have a bar, 500mm long (0.05m) 10mm wide (0.01m) and 3mm deep (0.003 m)The bat has a load applied in the centre of 30nI know the maximum yield stress is 150 mpa 150x10^6How do I calculate the maximum load the bar can take?2. Homework Equations I used stress = m y / I3...
18. Finding the maximum load of a bar from the yield stress

Homework Statement I have a bar, 500mm long (0.05m) 10mm wide (0.01m) and 3mm deep (0.003 m) The bat has a load applied in the centre of 30n I know the maximum yield stress is 150 mpa 150x10^6 How do I calculate the maximum load the bar can take? Homework Equations I used...
19. Calculating torque from yield stress understanding

Hello, I'm new here and so if I've put this in the wrong section or anything, please let me know and I'll fix/change whatever needs to be done. I just wanted to see if someone could help me understand something. When choosing a torque value, is it just ~90% of the yield stress of the...
20. Yield stress from tensile test and yield stress from hardness tests

Why can there sometimes be a difference observed between them?
21. Shemy's Puzzle: Calculating Yield Stress for a Metal

Right this is the question, Determine the yield stress for a metal with an average grain diameter of 0.045mm, if the yield stress for a metal changed from 650Nmm^-2 to 720Nmm^-2 when the average grain diameter decreases from 0.054mm to 0.037mm. I cannot figure this out, I've been trying...
22. Effect of Temp on yield stress and fracture toughness

Homework Statement I am given the trends for yield stress and fracture toughness as functions of temperature for steel. I need to explain the trends Homework Equations none The Attempt at a Solution I am guessing the yield stress is the stress that the material can withstand...
23. Difference between Yield stress and Proportional Limit

Is there a difference, when looking at the stress-strain diagram, between the "Proportional Limit stress" and the "Yield Stress" ? Thanks!
24. Debunking Yield Stress Myths: The Truth About Fluid Properties

Is Yield Stress for a fluid a real property? Or is it a time dependent illusion we are measuring? For example - some glass materials are referred to as super-cooled fluids and yet behave and appear like solids. In reality though these super cooled fluids flow - very slowly. Some old...
25. Finding yield stress with only modulus of elasticity and Poisson's ratio?

Is it possible to find the yield stress of a material with only modulus of elasticity and Poisson's ratio? I was given a problem that: What is the min. aluminum needed to support a block (10 Newton) to 1 meter high? E=70GPa and v=0.3 are the only given aluminum properties. I would know...