The ASTM standards in tensile testing are globally recognized guidelines by ASTM International that define the essential procedures for testing materials such as metals and plastics. These standards define how to measure properties like tensile strength and elongation, guaranteeing accurate and consistent results vital for material quality and safety in different industries.
There is a good chance that you've heard of the acronym ASTM. In 1898, the American Society for Testing and Materials, or ASTM, was founded to develop and publish international guidelines and standards voluntarily. Today, these standards are key to many industrial processes, ranging from producing materials like reinforced steel beams in our houses to high-tech electronic components such as circuit boards in our phones. These standards are an integral part of product manufacturing.
Our focus in this article will be on ASTM standards in tensile testing, specifically the most prevalent ones. Our discussion will cover how these standards guide the manufacturing of a variety of products and how they ensure safety and quality. As part of our exploration, we will review the most commonly used ASTM standards and their practical applications.
Why Standards are Important in Material Testing
It is important to understand the role standards play in general material testing before we discuss the standards themselves. Standards in material testing, particularly tensile testing, are crucial for guaranteeing a product's quality, safety, and reliability. From maritime to renewable energy, they assure the durability and performance of materials under specific conditions. A tensile test, for example, is needed in the maritime industry to verify the resilience of materials used in ship components under harsh sea conditions. Similarly, in the renewable energy sector, tensile testing confirms the endurance of wind turbine blade materials, assuring their efficiency and longevity.
These standards have been developed historically over several centuries, starting in the late 19th century and continuing until the early 20th century. This was a period marked by intense industrialization that necessitated the development of systematic testing methodologies. The American Society for Testing and Materials International (ASTM), established in 1898, along with the International Organization for Standardization (ISO), founded in 1947, have been at the forefront of creating these standards since the early 1900s. As a result of their efforts, many applications and industries have been able to maintain the integrity and consistency of the materials, preventing potential disasters from occurring.
In many cases, the reliability and safety of a product are directly related to compliance with tensile testing standards. In the automotive industry, for example, materials used in the construction of vehicles, such as steel in the axles and aluminum in the wheels, must undergo rigorous testing to withstand specific levels of stress to guarantee the safety of passengers in those vehicles.
A Distinction Between Tensile Sample Preparation and Tensile Testing Standards
When it comes to tensile testing, material testing standards are generally divided into two categories: those for tensile sample preparation and those for tensile testing themselves.
Tensile Sample Preparation Standards specify the procedures for preparing test specimens. Specifically, they describe the size, shape, and treatment of samples prior to testing. These standards make sure that tensile test specimens are consistent and suitable for the intended testing procedures. This category includes standards such as ASTM E8/E8M, which specifies the preparation methods for metallic test specimens.
Tensile Testing Standards, on the other hand, concern actual testing procedures. There are detailed instructions on how to conduct tensile tests, including the types of equipment to be used, the type of testing environment, and the interpretation of results. Mechanical properties such as tensile strength, ductility, yield strength, and elongation are determined by these standards. A few examples are ASTM A370 for mechanical testing of steel products and ASTM D638 for plastic tensile properties.
Having these standards separated reflects the preparation phase and the actual testing phase of material testing. When performing tensile testing, it is essential to prepare the specimen properly in order to obtain accurate and meaningful results. A test result may not accurately reflect the properties of a material without following the specific guidelines for sample preparation. Likewise, tensile tests should be conducted according to standardized methods to compare materials and assess their suitability.
ASTM E8/E8M: Essential for Metallic Material Testing
The ASTM E8/E8M standard is one of the most influential standards in material testing, specifically in tension testing of metallic materials. This method is used for quality control, material comparisons, and alloy development to evaluate the mechanical properties of metals.
ASTM E8/E8M assesses uniaxial tensile strengths and ductility of metals. Whether thin wires or heavy structural components, this standard applies to testing metallic materials at room temperature. The test measures yield strength, yield point elongation, tensile strength, elongation, and reduction in area. In engineering and manufacturing, these metrics are vital for understanding how materials will perform under different types of stress conditions.
A key feature of ASTM E8/E8M is its focus on room temperature testing, defined as temperatures between 10°C and 38°C (50°F and 100°F), ensuring standardized testing conditions. Most round specimens must have a gauge length of 4D (for E8) or 5D (for E8M).
The significance of ASTM E8/E8M goes beyond testing raw materials. It is often used for acceptance testing of commercial shipments, verifying that the materials being delivered meet the required specifications and standards. It's important to note that the results from standardized specimen tests may not accurately reflect the properties of the whole product or its behavior in different environments. Due to this limitation, comprehensive testing and analysis are necessary in many situations.
From automotive to aerospace, this standard is widely recognized and used for mechanical properties of metal components. For instance, it's used to test automotive components such as axles and engines, as well as materials used in aircraft structures.
Specially Designed for ASTM E8: TensileTurn CNC for Round Specimen Preparation
A good result requires compliance with ASTM E8/E8M, especially when preparing tensile specimens. Therefore, we cannot ignore introducing you to our fully advanced TensileTurn CNC - Round Specimen Preparation machine. With the ASTM E8 standard compliance, this automatic CNC lathe excels at preparing round tensile specimens.
TensileTurn CNC has a user-friendly interface and is ideal for operators regardless of their machining experience. Using the machine's award-winning touch screen, you can prepare specimens quickly and easily. The TensileTurn CNC is capable of making specimens up to 2 inches in diameter and 16 inches in length efficiently by choosing a standard tensile size from its extensive library of standards (ASTM, ISO, DIN, etc.).
TensileTurn CNC's compact footprint makes it suitable for a wide range of laboratory sizes. For untrained CNC machinists, it offers a turnkey solution for tensile specimen preparation. With the machine, you are guaranteed accurate and repeatable results every time, crucial for reliable tensile testing.
Moreover, the TensileTurn CNC is flexible enough to prepare sub-size specimens, threaded tensile specimens, button-head tensile bars, fatigue specimens, and other round-testing specimens. With Carbon software, experienced operators can program the machine for cutting, sanding, knurling, drilling, facing, or turning.
The machine's ability to produce high-quality tensile specimens quickly aligns perfectly with the ASTM E8/E8M standard, which means specimens are ready for testing in minutes. A combination of its advanced features, such as the 2.2KW heavy-duty motor, the 3-Jaw Universal Manual Chuck, and the 25L coolant tank capacity, makes the TensileTurn CNC an ideal choice for laboratories aiming to comply with ASTM E8/E8M.
ASTM A370 Standard for Steel Testing
The ASTM A370 standard covers a range of mechanical tests for steel, stainless steel, and related alloys. ASTM A370 includes tension, bend, hardness, and impact tests. It is important to note that ASTM A370 emphasizes both the mechanical and chemical requirements of the tested materials, unlike ASTM E8, which primarily tests tensions in metallic materials. ASTM A370 has specific chemical requirements, such as a specified manganese content, which ASTM E8 does not have. Among the differences between ASTM A370 and E8 are yield and tensile strength requirements.
A370 focuses on tensile testing, highlighting the most commonly measured properties. This standard assesses a material's resistance to elastic deformation by determining its Modulus of Elasticity. Yield Strength measures the stress level at which material deformation becomes permanent. Tensile Strength gauges the maximum force a material can withstand, directly linked to its strength, not ductility. The Area Reduction is indeed a measure of ductility. Total Elongation, another important metric, indicates how much the material elongates before failure. These metrics collectively give a complete view of material performance under stress.
Because of the standard's versatility, it is indispensable for industries that rely on steel products for their strength, durability, and composition. The ASTM A370 guarantees the quality and safety of construction materials and aerospace components. Providing manufacturers and engineers with reliable data, its comprehensive approach to testing makes it an essential component of the material testing process.
In terms of tensile testing, ASTM A370's detailed assessment of material properties under various stresses is crucial to determining the suitability of steel and alloy products for practical use. With its implementation, critical sector materials can withstand the required stress levels and maintain their integrity under real-world conditions. Finally, ASTM A370 is considered a cornerstone standard in material science and engineering.
ASTM D638 for Tensile Testing of Plastics
Standards are not limited to metallic materials - ASTM D638 is a pivotal standard for determining plastic tensile properties, including unreinforced and reinforced forms. This method is important for quality control and research because it tests the mechanical behavior of plastics under tensile stresses. It's designed for different plastic materials, measured in the form of standard dumbbell-shaped test specimens, under specific environmental conditions.
ASTM D638's sensitivity to environmental factors and specimen preparation is one of its key features. Thus, it is crucial to control these factors to achieve precise comparative results. Among the properties determined by the standard are tensile strength, yield strength, modulus of elasticity, and elongation at break. Despite this, the test results are highly sensitive to strain rate and environmental conditions. This limits their use for applications under conditions vastly different from the test setup.
ASTM D638 specifies testing materials up to 14 mm thick. One of the highlights of this standard is its ability to measure Poisson's ratio at room temperature. Result precision is such that variations in specimen thickness are taken into account when determining surface-volume ratios. For comparable results, it is recommended to use specimens of equal thickness.
In addition to phenolic resin or laminated materials, ASTM D638 also accommodates electrical insulation standards like D229 and D651. The ASTM D638 standard is fundamental in guaranteeing the reliability and performance of plastics. ASTM D638's tests are conducted with a constant rate of crosshead movement, revealing important characteristics of plastics in their state under stress, as a result of these tests.
ASTM E21 For Elevated Temperatures
The ASTM E21 standard, which tests metallic materials at elevated temperatures for tensile strength, is of significant importance to industries exposed to extreme temperatures. This standard evaluates critical mechanical properties of metals, such as their tensile strength, yield strength, elongation, and reduction of area under thermal stress.
According to the standard, the property measurements have to be made using precise testing methods that use advanced equipment, such as force measuring systems, extensometers, and thermocouples The process also involves determining the cross-sectional area of specimens before and after the test to assess their response to stress at elevated temperatures as a result of elevated temperature.
Although ASTM E21 provides a comprehensive evaluation of materials at elevated temperatures, it excludes the determination of modulus of elasticity and proportional limit. Moreover, it does not cover testing of materials subjected to rapid heating or strain rates during the evaluation process. There are many requirements in the standard that emphasize the need for precise alignment of the testing machine. In addition, the standard specifies the necessary equipment and conditions for accurate temperature and strain measurements to guarantee a reliable assessment of metal behavior under elevated temperature conditions.
ASTM E345 Standard for Metallic Foils
The next standard in our list is ASTM E345, which is specifically designed for the tensile testing of metallic foil at room temperature. Often used in a wide range of industries because of their unique characteristics, this standard is essential for determining tensile strength and elongation of extremely thin and delicate metallic materials used in a variety of fields.
Among other tensile testing methods such as ASTM E8/E8M, ASTM E345 is unique due to its approach to handling the fragility of foil specimens. Because foil is thinner than thicker materials, it should be handled carefully during testing to avoid damaging it during the process. Using ASTM E345 as a standard, specimen thickness can be determined by the weight of the specimen, a method that minimizes the risk of damaging these delicate samples during the measurement procedure. Moreover, the standard allows the measurement of elongation from the displacement of the crosshead, providing an alternative to the conventional contact extensometers that may alter test results if they interact with the specimen during the test.
Moreover, the ASTM E345 standard offers a great deal of flexibility when it comes to specimen thickness measurement and elongation calculation, making it an invaluable standard for industries that deal with foil materials. Due to its nuanced approach to specimen handling and testing, even the most delicate metallic foils can be tested for their tensile properties without compromising the integrity of the specimen.
ASTM A615: Reinforcing Concrete with Steel Bars
Following on our list of ASTM standards is ASTM A615. This is a specification for defining the characteristics of plain and deformed carbon-steel bars used in concrete reinforcement. The strength and durability of reinforced concrete are of particular importance in construction and civil engineering.
ASTM A615 covers carbon-steel bars in different grades, primarily Grades 40 , 60 , 75 , and the more recent addition, Grade 100 . Each grade number represents the minimum yield strength in thousands of pounds per square inch (psi) or megapascals (MPa), indicating the material's resistance to deformation under stress. For instance, Grade 40 bars have a minimum yield strength of 40,000 psi or 280 MPa.
Steel bars are produced using specific methods, including electric-furnace, basic-oxygen, or open-hearth processes. The ASTM A615 standard requires steel materials to conform to specific compositions of carbon, manganese, phosphorus, and sulfur based on heat analysis. Furthermore, the steel specimens must undergo tensile tests to determine their tensile strength, yield strength, and elongation.
ASTM A615 includes deformation tests, tension tests, and bend tests in its specifications. The tests verify that the steel bars are not only strong enough to reinforce concrete, but also flexible and ductile. The specification covers, among other things, the elongation and bending properties of steel bars, which are critical for their performance in structural applications.
A615 differs from other tensile testing standards in terms of its application scope and test methods. Specifically, it addresses the concrete reinforcement needs of the construction industry, ensuring that steel bars used in building structures will be robust, durable, and safe.
ASTM A615 Compliance: Introducing the Servo Hydraulic Universal Testing System
Our TensileTurn CNC for Round Specimen Preparation has already been introduced to you, but now we would like to introduce you to our UTM, which is specifically designed for tensile testing - the Servo Hydraulic Universal Testing System 600kN / 1000kN with Precision Load Cell. It meets and exceeds the requirements of a number of international standards, including ASTM A615.
Designed for high-force mechanical testing, the SHM Class A Series Servo Hydraulic Universal Testing Machine is a robust and versatile solution. The unit delivers accurate readings within 5% of the reading value for a wide range of applications, including tension, compression, shearing, and bending. Precision is a must for materials testing, especially when it comes to stringent standards like ASTM A615 for concrete reinforcement bars.
The system features a multi-column frame structure capable of holding loads of 600kN to 1000kN. It is equipped with a hydraulic-operated tensile grip and can be used with a wide range of materials. A tensile testing area is located on top of the testing system, and a compression and bending area is located at the bottom. In one unit, this dual capability allows for comprehensive material testing.
The Servo Hydraulic Universal Testing System is further enhanced by its advanced load cell that measures testing force directly. In comparison to traditional oil pressure sensors used in competitor brands, which are generally less accurate, this system stands out with its high precision (0.5 class) load cell.
Furthermore, EVOTest, the system's software, has a user-friendly interface and an extensive library of international testing standards. For in-depth analysis during testing, it provides various control modes and graphical representations. Its overload protection feature and automated reminders increase its functionality, guaranteeing safe and efficient testing.
ASTM E646 for Metallic Sheet Material Testing
The last standard in our article is ASTM E646, which determines the tensile strain-hardening exponents (n-values) of metallic sheet materials.
An ASTM E646 test determines the strain-hardening exponent, which measures a material's stretch and formability. As a result of plastic deformation, the n-value of a material increases in strength. Among other metal sheets, this measurement is particularly useful for evaluating the performance of formable low-carbon steel products. For determining the n-value, engineers typically use a strain interval of 10–20%.
This test method is designed to analyze the plastic stress-strain response of metallic sheet materials before necking. It is applicable to sheet materials with a thickness of 0.005 in. (0.13 mm) to 0.25 in. (6.4 mm). However, the method has been successfully applied to other forms and thicknesses through agreement, which shows just how versatile it is.
ASTM E646 does not apply to portions of the true stress versus true strain curve that exhibit discontinuous behavior, such as yield point elongation and the Portevin-Le Chatelier effect. Nevertheless, the standard allows for the use of curve-smoothing techniques by agreement, although caution is advised since these techniques may affect n.
Depending on the metal and test temperature, the n-value may vary with displacement rate or strain rate. This variability highlights the necessity of conducting the test under controlled conditions for accurate and reliable results. For industries where metallic sheet materials are extensively used, ASTM E646 strain-hardening exponents provide invaluable data for guiding material selection and product design.
Using ASTM Standards to Guide the Industry
ASTM standards serve as important guidelines in material testing. In this article, we've discussed a few of the most common ones. Each standard has an important role to play in assuring the quality and safety of materials in different industries. These standards are not mere recommendations, but are the foundation of material quality assurance. Ranging from ASTM E8/E8M, which specifies the tensile strength of metallic materials, to ASTM A615, which specifies the robustness of steel bars in reinforced concrete, standards play a crucial role in material testing. In concrete structures and beyond, they guarantee the integrity of steel reinforcements by defining properties such as tensile strength.
Sectors such as construction, automotive, aerospace, and renewable energy require understanding and adhering to these standards. By comparing materials, developing alloys, and conducting quality control, manufacturers can guarantee that products meet the rigorous requirements of safety and functionality. Despite their long history, these standards continue to evolve as materials science and engineering progress.
At TensileMill CNC, we recognize the importance of these standards in your work. We're here to help you with tensile testing, sample preparation, and detailed information about each of these standards. You can achieve compliance with ease and confidence using our expertise and a range of tools designed for sample preparation and tensile testing.
If you are interested in our sample preparation tools or tensile testing equipment, please request an online quote or contact us directly. We are ready to provide you with the support and information you need to meet your testing requirements. We must never forget that standards compliance is more than just compliance. It is about building a better, safer world.