Tensile strength
Tensile strength: Everything you need to know
In this article, tensile strength is defined as the maximum load that a material can withstand without breaking or stretching.
It is measured as force per unit area and is often expressed in psi (pounds per square inch). When a material is stretched and the load is below its tensile strength, it returns to its original shape and size in whole or in part.
When the tensile strength is reached, a ductile material begins to deform plastically and forms a constricted region, the so-called neck, where it finally breaks.
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More InformationMaterial | Tensile strength (MPa) |
|---|---|
Rubber | 15 |
Glass | 33 |
HDPE | 37 |
Pine wood | 35 |
Oak wood | 70 |
Brass | 400 |
Steel | 850 |
Diamond | 2.800 |
Aramid/Kevlar | 3.500 |
Carbon fiber | 7.000 |
Boron nitride nanotubes | 33.000 |
Graphs | 130.000 |
Please note that these values are approximate and may vary depending on the specific composition, heat treatment and manufacturing process. It is always advisable to consult the manufacturer’s specific data sheets for exact information.
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#1 Tensile strength: Basics
Tensile strength is a key measure of how much load a material can withstand without breaking when it is stretched.
This property is defined by the maximum load that a material can bear without breaking, divided by the original cross-sectional area of the material. It is often expressed in pressure units such as Pascal (MPa or GPa for stronger materials).
A common method for measuring tensile strength is the tensile test with a universal testing machine (UTM), which applies a controlled stress until the material breaks. An extensometer measures the changes in the length of the sample material.
The shape of the specimen for tensile tests is typically a round bar with a wide shoulder area at each end where the UTM holds the material during the application of tensile stress.
The change in the measuring length is recorded while the sample is being drawn.
The tensile strength is not only a measure of the load-bearing capacity of a material under tension, but also provides information about the behavior of the material under these conditions.
For example, some materials show an abrupt break when the tensile capacity is reached, while others deform or “constrict” before they break completely. In alloys, the tensile strength is influenced by the composition, such as the carbon content in carbon steels.
#2 Tensile strength: materials in comparison
The tensile strength varies depending on the type of material. Graphene, for example, is considered one of the strongest materials in terms of tensile strength with a value of 130,000 MPa, which is higher than steel (400 – 2,700 MPa).
Due to its high capacity for tensile stresses, this carbon allotrope can be produced as extremely thin but very strong and durable films.
Boron nitride nanotubes have a tensile strength of 33,000 MPa and are therefore suitable for aerospace applications.Plastics, on the other hand, generally have a relatively low tolerance to tensile stresses.
Metals and alloys
Steel, titanium, tungsten and Inconel are among the materials with the highest tensile strength. Their resilience is crucial for applications that require high strength, such as in the construction, automotive and aerospace industries.
For example, the tensile strength of steel varies considerably depending on the alloy and heat treatment. In general, however, the tensile strength of steel is usually around 400 to over 2,500 MPa, while titanium alloys can reach even higher values.
Non-metallic materials
Wood species such as oak and pine have significantly lower tensile strengths, typically in the range of 35 MPa for pine wood to around 70 MPa for oak wood.
These values are sufficient for many construction applications where wood is preferred, such as house construction or furniture.
Composites and high-performance materials
Modern composite materials such as carbon fiber or aramid (Kevlar) have very high tensile strengths.
Carbon fiber can achieve a strength of up to 7,000 MPa in tensile tests, while aramid fibers can have values of around 3,500 MPa.
These materials are particularly known for their high strength and low weight and are used in areas such as aerospace, sports equipment and ballistic protective clothing.
Thermoplastics and elastomers
Plastic materials such as polycarbonates and ABS have significantly lower tensile strengths compared to metals and composites, but these are sufficient for many consumer and industrial applications.
O-rings made of FFKM for example, only achieve a tensile strength of 10-20 MPa.
#3 Tensile strength: test methods and standards
Tensile strength testing is a critical step in the investigation of the mechanical properties of materials. There are several standards that define the tensile strength testing procedure to ensure that the results are reliable and internationally comparable.
ASTM standards
One of the most commonly used standards is ASTM E8 or ASTM E8M for metals, which describes testing at room temperature.
ASTM E8 refers to measurements in inches and pounds, while ASTM E8M uses metric units. Both standards define the preparation of the samples and the test procedure to minimize the influence of the machining process on the materials, as this could affect the results of the tensile strength test.
Another important standard is ASTM D638, which deals with the tensile strength properties of plastics.
ISO standards
In addition to the ASTM standards, there are also ISO standards such as ISO 6892-1, which focuses on the tensile strength testing of metals at room temperature.
This standard specifies the method for determining characteristic values such as yield strength, tensile strength and elongation at break. There are also specific standards for different temperature ranges and material types to meet the different requirements.
Testing equipment and challenges
Choosing the right testing equipment is crucial, especially with regard to quality assurance and supplier relationships.
The testing equipment should be calibrated and equipped with secure specimen grips, extensometers to measure strain and a data acquisition system to ensure accurate measurements.
Challenges can arise when a vendor’s testing equipment does not match the high-quality machinery of a material supplier, which can lead to discrepancies.
In such cases, close cooperation and coordination of test methods and equipment is required to ensure consistency of test results.
#4 Tensile strength: application examples
The strength determined in the tensile test is a decisive property in many branches of industry and applications and has a significant influence on the selection and design of materials.
Aerospace
In the aerospace industry, the tensile strength of materials is crucial to reduce weight and lower fuel consumption without compromising safety or performance requirements.
Composite materials, which are a combination of different materials, are often used due to their superior specific strength compared to individual materials.
The tensile strength of adhesive joints, carpets, cables, seals, hoses, seat belts and wiring are also thoroughly tested here.
Automotive industry
In the automotive sector, tensile strength is essential for the development and quality control of lightweight and high-strength materials, which is important for safety and fuel efficiency.
Among other things, it is used to determine the breaking strength of seat belts and to test the quality of exterior and interior linings such as seals and handles.
Metal and construction industry
In the metal and construction industry, the ASTM E8 method is used to evaluate the tensile strength of steel, to produce materials with the correct ductility and strength, and to meet compliance standards for high quality and safe materials.
The tensile strength of safety nets, timbers and geotextiles is also tested.
Electrical and electronics industry
In the electronics industry, understanding the mechanical and electrical behavior of conductive films and substrates used in flexible electronics is essential.
The characterization of the pull-off properties of electrical contacts and components is also important.
Medical devices and materials
In the medical field, tensile strength is used to assess the compression and strength of lenses, surgical tubes, catheters and other materials such as surgical gloves and silicone rubbers.
Packaging and paper industry
Tensile strength testing is also very important for the packaging and paper industry, where the strength and elongation of plastics, cardboard or paper is measured.
Plastics and rubber industry
In the plastics and rubber industry, tensile strength is tested to determine whether products have sufficient strength to withstand external physical stress.
Sports and fitness industry
Tensile strength also plays an important role in the sports sector, e.g. in the production and testing of racket strings or in testing the tear and tensile strength of materials used in shoes and sports equipment.
Textile industry
In the textile industry, tensile strength is used to assess whether a fabric is strong enough to withstand regular use and resist damage.
#5 Tensile strength: future prospects and innovations
The future of tensile strength testing is strongly influenced by the further development and implementation of new materials and technologies.
Increasing automation in test laboratories makes it possible to optimize processes and increase efficiency. Automated test procedures minimize human error and increase the reliability of results.
In addition, advanced technologies such as artificial intelligence and machine learning enable more precise adaptation and prediction of material behavior under load.
The remote monitoring and control of test systems, which became increasingly important during the COVID-19 pandemic, is expected to be maintained and further expanded in the long term. Materials science is also developing rapidly.
Innovative materials such as cellulose nanofibers, which are stronger than steel and spider silk, and platinum-gold alloys, which produce a diamond-like carbon under stress and can act as a lubricant, are just some of the developments that have the potential to transform manufacturing in various industries.
Trends in materials science are moving towards the development of sustainable materials, intelligent and reactive materials, the use of nanotechnology and the expansion of additive manufacturing.
These developments have far-reaching implications for industries such as aerospace, automotive and construction, where lightweight but high-strength materials are becoming increasingly important.
#6 Tensile strength: Questions briefly answered
In the following chapter we will answer further questions on the subject of tensile strength and tensile testing.
#6.1 Tensile strength of screws
The tensile strength of screws is decisive for their load-bearing capacity under tensile stress. It determines how much force a screw can withstand before it breaks. Important in areas such as construction, mechanical engineering and the automotive industry. They are often labeled with classes such as 8.8 or 10.9.
#6.2 Tensile strength of steel
The tensile strength of steel, expressed in MPa, is central to its performance. It varies depending on the steel grade and treatment. Higher values indicate greater resilience and resistance, which is particularly important in construction, automotive engineering and mechanical engineering.
Material | Tensile strength (MPa) |
|---|---|
Structural steel S235 | 400 |
Structural steel S355 | 550 |
Tool steel (unalloyed) | 700 |
Tempered steel C45 | 750 |
Stainless steel 304 | 800 |
316 stainless steel | 820 |
High-strength steel S690 | 900 |
Spring steel | 1500 |
Please note that these values are approximate and may vary depending on the specific composition, heat treatment and manufacturing process. It is always advisable to consult the specific data sheets of the steel manufacturer for exact information.
#6.3 Tensile strength aluminum
The tensile strength of aluminum alloys varies greatly, typically between 70 and 700 MPa.
She strength of aluminum depends on the alloy composition and heat treatment. Due to its high strength and low weight, aluminum is often used in the aerospace, automotive and construction industries
#6.4 Calculate tensile strength
Tensile strength is calculated by dividing the maximum load at which a material breaks by its cross-sectional area. This calculation is fundamental to materials science and helps to understand the load-bearing capacity of materials.
This formula makes it possible to evaluate the load-bearing capacity and resistance of a material to tensile forces.
σ=F(max)/A
Here is:
- the tensile strength,
- is the maximum force at which the material breaks,
- is the cross-sectional area of the material.
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