What is Yield Strength?

Yield strength is a material property that indicates the amount of stress required to cause permanent deformation in a material. It is an important parameter in engineering design, as it determines the maximum load that a material can withstand without undergoing plastic deformation.

Key Points

• Yield strength is the stress at which a material begins to deform plastically.
• It is a measure of a material’s resistance to permanent deformation.
• Yield strength is typically determined by performing a tensile test.
• The yield strength of a material is affected by its composition, microstructure, and heat treatment.
• Yield strength is an important parameter in engineering design, as it determines the maximum load that a material can withstand without undergoing plastic deformation.

Yield Strength Formula

Yield strength is a material property that measures the amount of stress required to cause permanent deformation in a material. It is an important parameter in engineering design, as it determines the maximum load that a material can withstand without undergoing plastic deformation.

Formula

The yield strength of a material can be determined using the following formula:

$$ Yield strength = Ultimate tensile strength / Factor of safety $$

where:

• Yield strength is the stress at which the material begins to deform plastically.
• Ultimate tensile strength is the maximum stress that the material can withstand before it fails.
• Factor of safety is a number that is used to account for uncertainties in the material properties and the design conditions.

Example

For example, if a material has an ultimate tensile strength of 100 MPa and a factor of safety of 2, then its yield strength would be 50 MPa. This means that the material can withstand a maximum stress of 50 MPa without undergoing plastic deformation.

The yield strength of a material is an important material property that is used in a variety of engineering applications. It is a measure of the amount of stress required to cause permanent deformation in a material, and it is used to determine the maximum load that a material can withstand without undergoing plastic deformation.

Stress-Strain Curve

A stress-strain curve is a graphical representation of the relationship between stress and strain in a material. It is used to determine the mechanical properties of a material, such as its yield strength, ultimate tensile strength, and modulus of elasticity.

Stress

Stress is the force per unit area acting on a material. It is calculated by dividing the force applied to a material by the cross-sectional area of the material. The SI unit of stress is the pascal (Pa), which is equivalent to one newton per square meter (N/m²).

Strain

Strain is the deformation of a material under load. It is calculated by dividing the change in length of a material by its original length. The SI unit of strain is the meter per meter (m/m), which is also known as the strain unit.

Stress-Strain Curve

A stress-strain curve is a plot of stress versus strain for a material. The curve can be divided into three regions:

• Elastic region: In the elastic region, the material deforms elastically, meaning that it returns to its original shape when the load is removed. The slope of the stress-strain curve in the elastic region is the modulus of elasticity, or Young’s modulus.
• Plastic region: In the plastic region, the material deforms plastically, meaning that it does not return to its original shape when the load is removed. The stress at which the material begins to deform plastically is called the yield strength.
• Failure region: In the failure region, the material fails, meaning that it breaks or ruptures. The stress at which the material fails is called the ultimate tensile strength.

Applications of Stress-Strain Curves

Stress-strain curves are used to determine the mechanical properties of materials, such as their yield strength, ultimate tensile strength, and modulus of elasticity. These properties are important for designing structures and machines that are safe and efficient.

Stress-strain curves are also used to study the behavior of materials under different conditions, such as temperature, pressure, and loading rate. This information can be used to develop new materials and improve the performance of existing materials.

Stress-strain curves are a valuable tool for understanding the mechanical properties of materials. They are used to design structures and machines that are safe and efficient, and to study the behavior of materials under different conditions.

Yield Strength Graph

A yield strength graph is a graphical representation of the relationship between the yield strength of a material and its plastic strain. It is a type of stress-strain curve that is used to determine the material’s yield strength, which is the stress at which the material begins to deform plastically.

Yield Strength

Yield strength is the maximum stress that a material can withstand without undergoing plastic deformation. It is an important mechanical property that is used to design and engineer components and structures. The yield strength of a material is determined by a number of factors, including the material’s composition, microstructure, and heat treatment.

Yield Strength Graph

A yield strength graph is a plot of the stress applied to a material versus the resulting plastic strain. The graph is typically divided into two regions: the elastic region and the plastic region.

• Elastic region: In the elastic region, the material deforms elastically, meaning that it returns to its original shape when the stress is removed.
• Plastic region: In the plastic region, the material deforms plastically, meaning that it does not return to its original shape when the stress is removed.

The yield strength is the stress at which the material transitions from the elastic region to the plastic region. This point is typically marked on the graph as the “yield point.”

Applications of Yield Strength Graphs

Yield strength graphs are used in a variety of applications, including:

• Design of components and structures
• Failure analysis
• Quality control
• Research and development

Yield strength graphs are an important tool for understanding the mechanical properties of materials and for designing and engineering components and structures that are safe and reliable.

Yield Strength vs Tensile Strength

Yield strength and tensile strength are two important mechanical properties of materials. They are both measures of a material’s resistance to deformation, but they measure different aspects of deformation.

Yield Strength

Yield strength is the stress at which a material begins to deform plastically. This means that the material will continue to deform even if the stress is removed. The yield strength is an important property for materials that are used in structural applications, such as buildings and bridges.

Tensile Strength

Tensile strength is the maximum stress that a material can withstand before it breaks. This is an important property for materials that are used in applications where they will be subjected to high stresses, such as ropes and cables.

Comparison of Yield Strength and Tensile Strength

The yield strength and tensile strength of a material are related, but they are not the same. The yield strength is always less than the tensile strength. This is because a material will always deform plastically before it breaks.

The following table shows the yield strength and tensile strength of some common materials:

As you can see, the yield strength of steel is much higher than the yield strength of aluminum, copper, and plastic. This means that steel is more resistant to plastic deformation than these other materials.

The tensile strength of steel is also higher than the tensile strength of aluminum, copper, and plastic. This means that steel is more resistant to breaking than these other materials.

Yield strength and tensile strength are two important mechanical properties of materials. They are both measures of a material’s resistance to deformation, but they measure different aspects of deformation. The yield strength is the stress at which a material begins to deform plastically, while the tensile strength is the maximum stress that a material can withstand before it breaks.

List of Materials and their Yield Strength

Metals

• Steel: 250-800 MPa
• Aluminum: 70-700 MPa
• Copper: 70-300 MPa
• Titanium: 280-1200 MPa
• Nickel: 170-1000 MPa

Polymers

• Polyethylene: 10-50 MPa
• Polypropylene: 20-70 MPa
• Polystyrene: 30-100 MPa
• Polycarbonate: 60-120 MPa
• Nylon: 50-150 MPa

Ceramics

• Alumina: 200-3000 MPa
• Zirconia: 1000-2000 MPa
• Silica: 70-1000 MPa
• Carbide: 1500-3000 MPa
• Nitride: 1000-2000 MPa

Composites

• Carbon fiber reinforced polymer: 150-1500 MPa
• Glass fiber reinforced polymer: 50-500 MPa
• Kevlar reinforced polymer: 100-1200 MPa
• Boron fiber reinforced polymer: 300-2000 MPa
• Ceramic matrix composite: 100-1000 MPa

Natural Materials

• Wood: 50-100 MPa
• Bone: 100-200 MPa
• Leather: 10-50 MPa
• Rubber: 1-20 MPa
• Silk: 50-100 MPa

Yield Strength FAQs

What is yield strength?

Yield strength is the material property that determines the amount of stress a material can withstand before it begins to deform plastically. In other words, it is the point at which a material will no longer return to its original shape after being subjected to a load.

How is yield strength measured?

Yield strength is typically measured using a tensile test. In a tensile test, a specimen of the material is pulled until it breaks, and the stress-strain curve is recorded. The yield strength is the point on the stress-strain curve where the material begins to deform plastically.

What are the different types of yield strength?

There are two main types of yield strength:

• Tensile yield strength is the yield strength measured in a tensile test.
• Compressive yield strength is the yield strength measured in a compression test.

What factors affect yield strength?

There are a number of factors that can affect yield strength, including:

• Material composition: The composition of a material can have a significant impact on its yield strength. For example, materials with a higher carbon content are typically stronger than materials with a lower carbon content.
• Heat treatment: Heat treatment can be used to improve the yield strength of a material. By heating and cooling the material in a controlled manner, the microstructure of the material can be changed, which can make it stronger.
• Cold working: Cold working is a process of plastic deformation that can also be used to improve the yield strength of a material. By cold working the material, the dislocations in the material are rearranged, which can make it stronger.

What are some applications of yield strength?

Yield strength is an important material property that is used in a variety of applications, including:

• Structural design: Yield strength is used to determine the maximum load that a structural member can withstand before it begins to deform plastically.
• Mechanical design: Yield strength is used to design mechanical components that must withstand high loads.
• Materials selection: Yield strength is used to select materials for applications where strength is important.

Conclusion

Yield strength is an important material property that is used in a variety of applications. By understanding the factors that affect yield strength, engineers can select materials and design components that meet the requirements of their applications.