Yield Strength - Definition, Example, Formula, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:44 PM IST

Introduction
In this article, our focus will be on yield strength, yield stress, yield strength of steel, yield point, the tensile strength of steel, etc.

What is Yield Strength?

The yield strength determines whether an object is rigid or pliable. It is the moment at which an object becomes plastic rather than elastic. Yield strength aids in the selection of appropriate construction materials based on the requirements. Because it would have been impossible to mould metals into the unorthodox shapes that we so passionately love, the toys that we so dearly love were constructed from something as pliable as plastic rather than metals.

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What is Yield Strength?
Formula of Yield Strength
Difference between Yield Strength and Tensile strength

Yield Strength - Definition, Example, Formula, FAQs

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What Does Yield Strength Mean?

Yield strength is a measurement of the greatest stress that a material can withstand without deforming plastically. It is a practical approximation of the elastic limit and is the pressure by which the object shows a definite deformation.

Yield strength is critical in engineering structural design. When constructing a component, for example, it must be able to withstand the force applied during operation and not distort plastically. To put it another way, a material with adequate yield strength should be used.

The yield strength is frequently used to calculate the upper limit of forces that can be applied without producing permanent deformation since it reflects the upper limit of forces that can be applied without generating permanent distortion.

The yield strength of an object determines whether it is difficult to shape or not. The upper yield strength of a material is the point at which it ceases to be elastic and becomes plastic. These upper and lower yield points assist us in determining the best materials for the job. Toys, for example, are typically constructed of plastic since moulding them into the many shapes required to produce them is impractical.

Formula of Yield Strength

The 0.2 per cent offset rule is the most frequent engineering approximation for yield stress. Assume a yield strain of 0.2 per cent and multiply by Young's Modulus for your material to apply this rule. Then the yield strength formula is given by:

It is also called the yield stress formula. Although the offset method can be used to calculate stress along a single axis, some applications require a formula that can handle two axes. Use the von Mises criteria to solve these issues:

stress-strain graph

The Stress-Strain Graph has certain unique characteristics. The following are some of them:

Proportional limit: Hooke's Law is preserved at the proportional limit of the stress-strain curve. As a result, the stress-to-strain ratio yields a proportionality constant known as Young's modulus. The proportionate limit is the point on the stress-strain graph OA.
Elastic Limit: This is the point at which the material returns to its original state once the load operating on the body is eliminated. The material does not return to its original state after reaching this limit, resulting in plastic deformation of the material.
Yield Point: The yield point definition is given as, the point at which a material begins to deform in its current state and, in most cases, turns into plastic. After the point is passed, the object undergoes a permanent distortion in one of two ways. One could be a lower yield point, while the other could be higher.
Ultimate Stress Point: The ultimate stress point is the point at which the material can endure the most stress before deforming. If the material is pushed past this point, it will fail.
Breaking or Fracture Point: This is the point at which the material fails

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Yield Stress of Steel

Yield strength is the maximum force that may be given to an object before it changes its shape or structure. The tensile test is used to determine the strength of any material. The material is stressed and pulled aggressively in both directions during this test. A graph, also known as a stress-strain graph, can be generated as a result of this test.

Yield strength of mild steel: 250MPa

Tensile Strength

Tensile strength is the force required to pull an object, such as a structural beam, wire, or rope, to its breaking point. The largest amount of tensile stress that a material can withstand before breaking into little pieces is its tensile or yield strength. The largest stress a material can endure before breaking down is referred to as tensile ultimate strength.

Tensile Strength of Steel

By definition, tensile refers to the ability of steel to be drawn out. Tensile strength is the steel's ability to resist breaking under tensile force. It's used to describe the moment at which steel changes from an elastic to a plastic state. It's commonly expressed in terms of force per area cross-section. The steel rips apart when it is moved away from its stress point.

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Tensile Strength of Mild Steel

The maximum amount of stress that any material can bear when pushed or stretched is known as tensile strength. Any tensile strength is put to the test by placing samples of a material with a defined area of cross-section within a tensometer and increasing the force until it breaks.

Few materials break down without deforming, whereas more ductile materials stretch just slightly and shrink when under great stress. Tensile strength is thus quantified in Pascal, pounds per square inch, or Megapascal as a force per unit of area.

Mild steel, on the other hand, is less ductile than other steels because it contains less hardening alloy and carbon. It has a tensile strength of 400MPa, which is relatively low.

Difference between Yield Strength and Tensile strength

Yield strength	Tensile strength
1. The highest stress that a material can sustain while deforming is referred to as yield strength.	1. The utmost strength that any solid substance may withstand before failing is called ultimate strength.
2. Under any tensile loading, it is the maximum stress that coincides with the yield point in the stress-strain curve.	2. In the curve below tensile loading, it is referred to as the stress that corresponds to ultimate tensile strength.

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Frequently Asked Questions (FAQs)

1. What is Yield? Or What do you mean by Yield? Or Definition of Yield

2. What is Yield Point?

The stress at which a solid material that has been stretched begins to flow or change shape permanently is known as the yield point in structural engineering. It is the point on a stress-strain curve that denotes the end of stretchability and the start of plastic behaviour. When a material's stretchability is lower than the yield point, it deforms and after the removal of yield stress point, it regains its original shape.

3. Hindi meaning of Yield is …………………….

The Hindi meaning of Yield is उपज.

4. What is Yield value?

The minimal shearing or normal stress that must be applied to a solid to cause continuous deformation is the yield value.

5. What are upper yield point and lower yield point?

The upper yield point is the starting point for plastic deformation. This is because the dislocations in the crystalline structure begin to move. After a while, though, the dislocations become too many and obstruct each other's movement. This is known as strain hardening, and the lower yield point is when strain hardening begins. Plastic deformation occurs beyond the elastic limit, and strains are not fully recovered. When the load is removed, there will be permanent deformation or set. Upper and lower yield points are the terms used to describe these two positions.

6. What is proof stress? Or proof stress definition

A material's proof stress is the maximum amount of stress it can withstand before undergoing a small bit of plastic deformation. Proof stress is defined as the point where the material demonstrates 0.2 percent plastic deformation.

This type of stress is commonly employed in the industrial business to guarantee that a material's elastic limit is not exceeded. That is, a safe load is provided to the object so that it is not stressed to the point of irreversible size or shape change. If a material is allowed to surpass its proof stress, it might permanently distort, leading to failure or fracture.

In the maritime and offshore industries, proof stress is particularly useful. The proof stress of ships and platform legs is crucial in evaluating how much force these structures can withstand before permanently deforming.

Because it is the stress required to make the material yield, proof stress is also known as offset stress.

7. Definition of strength of materials.

In material mechanics, strength refers to a material's ability to withstand a load without failure or plastic deformation. The link between external loads applied to a material and the consequent deformation or change in material dimensions is referred to as material strength. These characteristics must be considered when constructing structures and equipment so that the material chosen has sufficient strength to resist applied loads or forces while maintaining its original shape. The ability of a material to endure this imposed stress without failure or plastic deformation is its strength.

8. What is tensile strength of metals?

By definition, tensile means able to be stretched or dragged out. The resistance of steel to breaking under tensile tension is known as tensile strength. It's usually expressed as force units per cross-sectional area. A piece of steel will split apart once it has been pulled past its tensile stress point.

9. My strength meaning in Hindi is …………………….

My strength meaning in Hindi is मेरी शक्ति.

10. How does yield strength differ from ultimate tensile strength?

Yield strength is the point where a material begins to deform plastically, while ultimate tensile strength is the maximum stress a material can withstand before failing. Yield strength occurs before ultimate tensile strength in a stress-strain curve.

11. Why is yield strength important in engineering design?

Yield strength is crucial in engineering design because it determines the maximum stress a material can withstand without permanent deformation. Designers use it to ensure structures and components remain safe and functional under expected loads.

12. How is yield strength measured?

Yield strength is typically measured through tensile testing, where a sample is stretched until it yields. The stress at the yield point is calculated by dividing the force applied by the original cross-sectional area of the sample.

13. Can yield strength change with temperature?

Yes, yield strength typically decreases as temperature increases. This is because higher temperatures increase atomic vibrations and reduce the force needed to cause plastic deformation.

14. How does strain hardening affect yield strength?

Strain hardening increases yield strength by creating more dislocations in the material's crystal structure. These dislocations interact and impede each other's movement, requiring more stress to cause further deformation.

15. What is the yield strength formula?

The yield strength formula is σy = F / A, where σy is the yield strength, F is the yield force, and A is the original cross-sectional area of the sample.

16. How does grain size affect yield strength?

Generally, smaller grain sizes lead to higher yield strength. This is described by the Hall-Petch relationship, where yield strength is inversely proportional to the square root of the average grain diameter.

17. How does yield strength relate to Hooke's Law?

Yield strength marks the end of the linear elastic region described by Hooke's Law. Below the yield strength, stress is proportional to strain; above it, this relationship no longer holds.

18. What is the yield ratio?

The yield ratio is the ratio of yield strength to ultimate tensile strength. It provides information about a material's ductility and its behavior under load.

19. What is meant by "yielding" in materials science?

Yielding refers to the onset of plastic deformation in a material. It's the point where a material transitions from elastic (reversible) to plastic (permanent) deformation under applied stress.

20. What is yield strength in materials science?

Yield strength is the stress at which a material begins to deform plastically, meaning it won't return to its original shape when the stress is removed. It marks the transition from elastic to plastic deformation.

21. Can yield strength be negative?

No, yield strength cannot be negative. It represents the minimum stress required to cause plastic deformation and is always a positive value.

22. What is the 0.2% offset yield strength?

The 0.2% offset yield strength is a convention used when materials don't have a clear yield point. It's defined as the stress that produces a plastic strain of 0.2% and is used as a practical approximation of yield strength.

23. How does alloying affect yield strength?

Alloying typically increases yield strength by introducing impurity atoms that impede dislocation movement in the crystal structure. This makes it harder for the material to deform plastically.

24. What's the difference between yield strength and yield point?

Yield strength is the stress at which a material begins to deform plastically, while the yield point is the exact moment this occurs. Some materials have a clear yield point, while others transition more gradually.

25. What's the difference between yield strength and proof stress?

Yield strength and proof stress are often used interchangeably, especially for materials without a clear yield point. Proof stress is the stress that causes a specific amount of permanent deformation, typically 0.2%.

26. How does yield strength compare in metals and polymers?

Metals typically have higher yield strengths than polymers. Metals deform through dislocation movement, while polymers deform through chain sliding and uncoiling, which generally requires less stress.

27. Can yield strength be improved?

Yes, yield strength can be improved through various methods such as work hardening, heat treatment, alloying, and grain size reduction.

28. How does yield strength relate to fatigue strength?

Yield strength and fatigue strength are related but different. While yield strength is the stress for onset of plastic deformation, fatigue strength is the highest stress a material can withstand for a given number of stress cycles without failing.

29. What's the significance of yield strength in ductile vs. brittle materials?

Yield strength is more significant in ductile materials, which undergo substantial plastic deformation before fracture. Brittle materials often fracture with little or no plastic deformation, making ultimate strength more relevant.

30. How does strain rate affect yield strength?

Higher strain rates generally increase yield strength. This is because rapid deformation gives dislocations less time to overcome obstacles through thermal activation, requiring higher stress to cause plastic deformation.

31. How does crystal structure influence yield strength?

Crystal structure significantly affects yield strength. For example, body-centered cubic (BCC) structures typically have higher yield strengths than face-centered cubic (FCC) structures due to differences in dislocation mobility.

32. What is the relationship between yield strength and hardness?

There's generally a positive correlation between yield strength and hardness. Both properties relate to a material's resistance to plastic deformation, though they're measured differently.

33. How does yield strength relate to elastic modulus?

While both are material properties, yield strength and elastic modulus are distinct. Elastic modulus describes a material's stiffness in the elastic region, while yield strength marks the transition to plastic deformation.

34. What is work hardening and how does it affect yield strength?

Work hardening, or strain hardening, is the strengthening of a material through plastic deformation. It increases yield strength by creating and tangling dislocations, making further deformation more difficult.

35. How does yield strength vary with material purity?

Generally, increasing material purity decreases yield strength. Impurities often act as obstacles to dislocation movement, so their removal can make plastic deformation easier.

36. What's the difference between engineering stress and true stress in yield strength measurements?

Engineering stress is calculated using the original cross-sectional area, while true stress uses the instantaneous area. True stress is higher than engineering stress after yielding due to necking.

37. How does yield strength relate to residual stress?

Residual stresses can effectively lower the apparent yield strength of a material by adding to applied stresses. If residual stresses are high enough, they can cause yielding even without external loads.

38. What is the significance of the yield strength to weight ratio?

The yield strength to weight ratio, or specific strength, is important in applications where both strength and weight are critical, such as in aerospace. Materials with high specific strength can provide strength with less weight.

39. How does yield strength relate to toughness?

While related, yield strength and toughness are different properties. A material with high yield strength may not necessarily be tough. Toughness involves both strength and ductility, representing a material's ability to absorb energy before fracturing.

40. What is meant by "yield criterion" in materials science?

A yield criterion is a mathematical expression defining the limit of elasticity under any combination of stresses. Common examples include the von Mises and Tresca yield criteria.

41. How does yield strength differ in compression versus tension?

For many materials, yield strength in compression is similar to that in tension. However, some materials (like concrete) have significantly different yield strengths in compression and tension.

42. What is the Bauschinger effect and how does it relate to yield strength?

The Bauschinger effect is the phenomenon where plastic deformation in one direction reduces the yield strength in the opposite direction. It's important in cyclic loading scenarios.

43. How does yield strength relate to creep resistance?

While not directly related, materials with higher yield strengths often have better creep resistance. However, creep involves time-dependent deformation and can occur below the yield strength at elevated temperatures.

44. What is dynamic yield strength?

Dynamic yield strength is the yield strength of a material under high strain rate conditions, such as impact loading. It's typically higher than the static yield strength due to strain rate effects.

45. How does yield strength relate to fracture toughness?

Yield strength and fracture toughness often have an inverse relationship. Materials with very high yield strengths tend to have lower fracture toughness, as they're less able to blunt crack tips through plastic deformation.

46. What is the Hall-Petch equation and how does it relate to yield strength?

The Hall-Petch equation relates yield strength to grain size: σy = σ0 + k/√d, where σy is yield strength, σ0 is a material constant, k is the strengthening coefficient, and d is the average grain diameter.

47. How does yield strength change in nanocrystalline materials?

In nanocrystalline materials, yield strength initially increases as grain size decreases (following the Hall-Petch relationship). However, below a critical grain size, this trend can reverse due to grain boundary sliding.

48. What is meant by "upper and lower yield points"?

Some materials, particularly low-carbon steels, exhibit distinct upper and lower yield points. The upper yield point is the maximum stress before yielding begins, while the lower yield point is the stress during continued yielding.

49. How does yield strength relate to dislocation density?

Yield strength generally increases with dislocation density. More dislocations mean more obstacles to dislocation movement, requiring higher stress to cause plastic deformation.

50. What is the difference between macroscopic and microscopic yield strength?

Macroscopic yield strength refers to the bulk material property, while microscopic yield strength relates to yielding at the crystal or grain level. Microscopic yielding can occur before macroscopic yielding is observed.

51. How does yield strength relate to the concept of "safe stress"?

Safe stress in design is typically a fraction of the yield strength, determined by applying a safety factor. This ensures that under normal conditions, the material remains in the elastic region, preventing permanent deformation.

52. What is meant by "yield surface" in multiaxial stress states?

A yield surface is a mathematical construct in stress space that defines the combination of stress components that will cause yielding in a material under multiaxial loading conditions.

53. How does yield strength relate to the ductile-to-brittle transition?

The ductile-to-brittle transition is characterized by a change in fracture behavior, often accompanied by an increase in yield strength. This transition is temperature-dependent and is particularly important in materials like steel.

54. What is the relationship between yield strength and dislocation pinning?

Dislocation pinning increases yield strength by creating obstacles that impede dislocation movement. This can be achieved through various mechanisms such as solute atoms, precipitates, or other dislocations.

55. How does yield strength relate to the concept of "plastic zone" in fracture mechanics?

The plastic zone is the region near a crack tip where the local stress exceeds the yield strength, causing plastic deformation. The size of this zone is inversely related to the yield strength of the material.

56. What is meant by "yield locus" in sheet metal forming?

A yield locus is a two-dimensional representation of the yield surface, often used in sheet metal forming to describe the onset of plastic deformation under different stress states.

57. How does yield strength relate to the concept of "strain energy"?

Strain energy is the energy stored in a material due to elastic deformation. The area under the stress-strain curve up to the yield point represents the elastic strain energy per unit volume that the material can store.

58. What is the significance of the yield strength to elastic modulus ratio?

The ratio of yield strength to elastic modulus (σy/E) is important in determining the elastic strain limit of a material. It's particularly relevant in applications requiring high elastic deformation, such as springs.

59. How does yield strength relate to the concept of "plastic collapse" in structural engineering?

Plastic collapse occurs when a structure develops enough plastic hinges to form a mechanism. The yield strength of the material determines the load at which these plastic hinges begin to form, influencing the overall structural behavior.