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Understanding Yield Strength and Tensile Strength

Yield Strength and Tensile Strength

Understanding the properties of materials is crucial when it comes to designing and manufacturing parts in a machine shop. Two key properties that engineers and manufacturers must consider are yield strength and tensile strength. Both properties provide valuable insights into a material’s behavior under stress and its ability to withstand deformation or failure.

Yield strength and tensile strength are essential properties that engineers and manufacturers must consider when designing and producing parts. Yield strength provides information on the maximum stress a material can endure before experiencing permanent deformation, while tensile strength indicates a material’s resistance to fracture or failure under tensile loads. Understanding these properties allows for better part design, optimized fabrication processes, and the selection of suitable materials for various applications.

Yield strength

Yield strength is a measure of the stress at which a material begins to undergo plastic deformation. In other words, it is the point at which a material transitions from elastic deformation, where it can return to its original shape, to plastic deformation, where it remains permanently deformed. Yield strength is typically expressed in units of pressure, such as Pascals (Pa) or pounds per square inch (psi).

When a material is subjected to increasing stress, it initially undergoes elastic deformation. As the stress increases beyond the yield strength, the material experiences the yield point phenomenon. This is where the material starts to deform plastically, and any further increase in stress results in permanent deformation. The yield point can be observed on a stress-strain curve, which shows the relationship between the applied stress and the resulting strain on a material.

Yield strength is a crucial factor in part design and manufacturing, as it indicates the maximum stress a material can endure before experiencing permanent deformation. This information is essential for engineers when designing parts that will be subjected to stress, as it helps ensure the parts will maintain their intended shape and function throughout their lifespan. Additionally, understanding a material’s yield strength allows manufacturers to optimize fabrication processes and avoid potential issues related to overloading or excessive deformation.

Tensile strength

Tensile strength, also known as ultimate tensile strength (UTS), is the maximum stress a material can withstand while being stretched or pulled before it breaks or fractures. Like yield strength, tensile strength is expressed in units of pressure, such as Pascals (Pa) or pounds per square inch (psi).

The ultimate tensile strength of a material can be found on a stress-strain curve, which plots the applied stress against the resulting strain. The peak of this curve represents the material’s tensile strength, and the corresponding strain at this point is called the fracture strain. Once a material reaches its ultimate tensile strength, it can no longer withstand the applied stress and will fail, either by breaking or fracturing.

Tensile strength is a vital consideration in part design and manufacturing, as it provides insights into a material’s ability to resist fracture or failure under tensile loads. Engineers need to understand a material’s tensile strength to design parts that can withstand the expected forces during their service life without breaking. This knowledge is also crucial for manufacturers, as it enables them to select the appropriate materials for specific applications and helps prevent potential part failures due to insufficient tensile strength.

Yield and Tensile strengths of common alloys

Note: The values provided in these tables are approximate and vary depending on factors such as material processing and heat treatment. Always consult material datasheets or manufacturer guidelines for precise values when designing and ordering parts.

Aluminum Alloys

Alloys Yield Strength Tensile Strength
Aluminum 2011
43,000 psi [296 MPa]
55,000 psi [379 MPa]
Aluminum 2024
47,000 psi [324 MPa]
68,000 psi [469 MPa]
Aluminum 6061
40,000 psi [276 MPa]
45,000 psi [310 MPa]
Aluminum 6262
39,000 psi [269 MPa]
42,000 psi [290 MPa]
Aluminum 7075
73,000 psi [503 MPa]
83,000 psi [572 MPa]

Stainless Steel Alloys

Alloys Yield Strength Tensile Strength
SS 303
35,000 psi [241 MPa]
90,000 psi [621 MPa]
SS 304
31,200 psi [215 MPa]
90,000 psi [621 MPa]
SS 304L
25,000 psi [172 MPa]
70,000 psi [483 MPa]
SS 310
30,000 psi [207 MPa]
80,000 psi [552 MPa]
SS 316
30,000 psi [207 MPa]
90,000 psi [621 MPa]
SS 316L
25,000 psi [172 MPa]
70,000 psi [483 MPa]
SS 404
131,980 psi [910 MPa]
162,400 psi [1,120 MPa]
SS 410
45,000 psi [310 MPa]
100,000 psi [689 MPa]
SS 416
40,000 psi [276 MPa]
95,000 psi [655 MPa]
SS 430
40,000 psi [276 MPa]
75,000 psi [517 MPa]
SS 440C
60,000 psi [414 Mpa]
100,000 psi [689 MPa]

Steel Alloys

Alloys Yield Strength Tensile Strength
Steel 1008
41,300 psi [285 MPa]
49,300 psi [340 MPa]
Steel 1018
53,700 psi [370 MPa]
63,800 psi [440 MPa]
Steel 1045
45,000 psi [310 MPa]
90,000 psi [621 MPa]
Steel 1137
49,890 psi [344 MPa]
84,700 psi [584 MPa]
Steel 1215
60,200 psi [415 MPa]
78,300 psi [540 MPa]
Steel 12L14
60,000 psi [414 MPa]
78,000 psi [538 MPa]
Steel 4130
63,100 psi [435 MPa]
97,200 psi [670 MPa]
Steel 4140
60,200 psi [415 MPa]
95,000 psi [655 MPa]
Steel 8620
55,800 psi [385 MPa]
76,900 psi [530 MPa]
Steel A2
36,000 psi [248 MPa]
90,000 psi [621 MPa]
Steel M2
80,000 psi [552 MPa]
120,000 psi [827 MPa]

Titanium Alloys

Alloys Yield Strength Tensile Strength
Ti Grade 5
128,000 psi [882 MPa]
138,000 psi [952 MPa]
Ti Grade 23
110,000 psi [759 MPa]
125,000 psi [862 MPa]

Copper Alloys

Alloys Yield Strength Tensile Strength
Copper C360
20,000 psi [138 MPa]
58,000 psi [400 MPa]
Copper C353
16,000 psi [110 MPa]
54,000 psi [372 MPa]
Copper C230
10,000 psi [69 MPa]
42,000 psi [290 MPa]
Copper C464
32,000 psi [221 MPa]
70,000 psi [483 MPa]
Copper C443
15,000 psi [103 MPa]
52,000 psi [358 MPa]

Brass Alloys

Alloys Yield Strength Tensile Strength
Brass 353
16,000 psi [110 MPa]
54,000 psi [372 MPa]
Brass 360
20,000 psi [138 MPa]
58,000 psi [400 MPa]


Alloys Yield Strength Tensile Strength
Polyethylene (PE)
1,800 - 4,800 psi [12-33 MPa]
2,500 - 6,000 psi [17-41 MPa]
Polypropylene (PP)
3,500 - 5,500 psi [24-38 MPa]
4,500 - 7,000 psi [31-48 MPa]
Polyvinyl chloride (PVC)
2,500 - 6,000 psi [17-41 MPa]
3,500 - 7,000 psi [24-48 MPa]
Polymethyl methacrylate (PMMA)
6,000 - 9,000 psi [41-62 MPa]
7,000 - 11,000 psi [48-76 MPa]
Polycarbonate (PC)
9,000 - 12,000 psi [62-83 MPa]
9,500 - 14,000 psi [65-97 MPa]
3,500 - 8,000 psi [24-55 MPa]
5,000 - 12,000 psi [34-83 MPa]
10,000 - 20,000 psi [69-138 MPa]

Understanding Yield Strength and Tensile Strength

In order to fully understand the differences between yield strength and tensile strength, you’ll need to understand how materials behave and change under stress. This section explains the stress-strain curve, various types of material deformation, the distinction between ductile and brittle materials, and factors influencing the yield and tensile strength.

Stress-Strain Curve

The stress-strain curve is a graphical representation of a material’s response to applied stress. It plots stress, or the force applied per unit area, against strain, the change in the material’s dimensions relative to its original size. This curve is crucial in understanding how materials behave under different stress conditions and provides invaluable insights into their mechanical properties.

The stress-strain curve typically consists of several distinct regions. Initially, the curve follows a linear path, which represents the material’s elastic behavior. In this region, the material returns to its original shape once the stress is removed. As the stress increases, the material reaches its yield strength, the point at which plastic deformation begins.

Stress-Strain Curve
Stress-Strain Curve (Wikipedia)

Elastic and Plastic Deformation

Deformation can be classified into two types: elastic and plastic. 

Elastic deformation occurs when a material returns to its original shape after the removal of an applied stress. This behavior is governed by Hooke’s Law, which states that the strain is proportional to the stress applied within the elastic limit.

Plastic deformation, on the other hand, refers to the permanent change in a material’s shape after the applied stress exceeds the yield strength. In this region, the stress-strain curve becomes nonlinear, and the material undergoes irreversible changes, such as dislocation movements and slip. The ability of a material to undergo significant plastic deformation before breaking is a measure of its ductility.

Ductile vs Brittle Materials

Materials can be broadly classified as ductile or brittle based on their ability to withstand deformation. Ductile materials, such as metals and certain polymers, can undergo large amounts of plastic deformation before fracture. These materials typically exhibit a high degree of toughness and energy absorption capacity, making them ideal for various applications, including automotive components and structural elements.

Brittle materials, on the other hand, are characterized by their inability to undergo significant plastic deformation. These materials, which include ceramics, glasses, and some polymers, often have high strength but low toughness. They tend to fracture suddenly and without warning, making them less suitable for applications where impact or sudden stress is expected.

Factors Influencing Yield and Tensile Strength

Various factors influence a material’s yield and tensile strength, which are critical properties for designing and manufacturing reliable parts. Some of these factors include:

Material Composition: The elements that make up an alloy greatly influence its mechanical properties, including yield and tensile strength. For example, adding carbon to iron creates a carbon-steel alloy, which has greater strength and toughness than pure iron.

Heat Treatment and Processing: The way a material is processed can have a significant impact on its mechanical properties. Heat treatments, such as annealing, quenching, and tempering, can alter a material’s strength by changing its microstructure. Similarly, processes like cold working or hot working can influence a material’s mechanical behavior by introducing dislocations, affecting grain size, or inducing residual stresses.

Grain Size and Orientation: The size and orientation of a material’s grains or crystallites play a crucial role in determining its mechanical properties. Finer grains typically result in higher strength and toughness due to the increased number of grain boundaries, which impede dislocation movement. The orientation of grains can also influence a material’s response to stress, as some orientations are more favorable for slip and dislocation movement than others.

Choosing the right material for your parts

Selecting the best material for a specific application is a critical aspect of the design and manufacturing process. A well-informed decision requires finding the right balance between yield strength, tensile strength, and other material properties, considering the specific requirements of the application, and accounting for factors such as cost, availability, machinability, and environmental conditions.

Balancing Yield Strength, Tensile Strength, and Other Properties

The key to choosing the right material lies in understanding the relationship between yield strength, tensile strength, and other material properties such as ductility, toughness, hardness, and fatigue resistance. These properties often interact with one another, and an increase in one property may lead to a decrease in another. For example, increasing a material’s strength may reduce its ductility.

When selecting a material, it’s essential to prioritize the properties that are most important for the specific application. For instance, a component subjected to high impact forces may require a material with high toughness and ductility, while a part exposed to cyclic loading might need a material with excellent fatigue resistance. By understanding these trade-offs, you can make informed decisions that optimize the performance of your components.

Material Selection Based on Application Requirements

The primary step in material selection is identifying the application’s specific requirements. This may involve considering factors such as load-bearing capacity, operating temperature, corrosion resistance, and exposure to chemicals or other environmental conditions. For example, a component used in a high-temperature environment may require a material with excellent thermal stability and resistance to creep, while a part exposed to a corrosive environment might need a material with exceptional corrosion resistance.

Additionally, the material’s yield strength and tensile strength should be matched to the anticipated loads and stresses the component will experience during its service life. By assessing the application requirements, you can narrow down your material options and make a more informed selection.

Factors to Consider

Several factors should be taken into account when choosing a material for a specific application. Some of these factors include:

  1. Cost: Budget constraints often play a significant role in material selection. Although more expensive materials may offer superior performance, it is essential to weigh these benefits against the increased cost to determine if the additional expense is justified.
  2. Availability: The availability of a material can also influence the selection process. Some materials may have long lead times or be difficult to source, which can impact production schedules and project timelines.
  3. Machinability: The ease with which a material can be machined, formed, or processed is another crucial consideration. Some materials are more challenging to work with or require specialized equipment, leading to increased production costs and manufacturing complexities.
  4. Environmental Factors: The environmental conditions where the part will be used should also be considered when selecting a material. Temperature, humidity, exposure to chemicals, and UV radiation can significantly impact a material’s performance and longevity. Choosing a material with suitable resistance to these environmental factors can help ensure the long-term reliability of your components.

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