Codes and Standards Packet
This packet is intended for use in a mechanical engineering strength of materials course. Engineering codes and standards are discussed, including a brief history of standards development. Types of standards are examined, as well as the organizations that create these standards. ASTM E8 is specifically addressed, and two kinds of test specimens are reviewed, per ASTM guidelines.
Time for presentation is approximately 30 minutes.
Objective:
To introduce mechanical engineering students to basic safety concerns involving codes and standards, specifically tensile testing standards.
This packet includes the following items:
- Preview the Lecture material for instructor
- Preview the Overheads for use during lecture
- Preview the Handouts for students
- Preview the Homework problems
Download Codes and Standards Module in printable Adobe Acrobat Format (pdf). This includes overheads in a ready to use format.
Homework problem solutions, exam problems, and exam solutions are available to qualified recipients. Send an email with request information to Dr. Donald Bloswick.
Codes and Standards Lecture Outline
Engineering Codes and Standards (OVERHEAD 1)
Standards in engineering specify an adherence to a level or quality that must be maintained to insure the safety of those involved.
Standards promote safety, reliability, productivity, efficiency, and consistency.
Historical Codes and Standards
Throughout history, standards have evolved from using the king’s foot and arm as units of measure, to complex standards that guarantee compatibility and interoperability anywhere in the world. At the first meeting of the American Society of Mechanical Engineers in 1880, standardized sizes for screw threads were discussed.
The demand for compatibility came from an understanding of the importance of safety. (OVERHEAD 2)
An example of this occurred in 1904, during a fire in Baltimore, Maryland. More than 1500 structures burned to the ground.
Fire companies came from areas such as New York, but could not help because their hose couplings did not fit the fire hydrants in Baltimore.
Many jobs have emerged from the need for correlation, and engineers have a responsibility to uphold these high standards.
Professional Engineers abide by a Code of Ethics. (OVERHEAD 3)
The primary focus is the first fundamental canon: "to hold paramount the safety, health, and welfare of the public."
Engineers can maintain this focus by adhering to the standards set by the government and the private sector.
Engineers can affect standards by becoming members of engineering organizations which develop and maintain the standards.
Types of Standards
There are two main types of standards: (OVERHEAD 4)
A performance standard, which specifies what a product is supposed to accomplish, and
A design standard, which describes what the product is made of and how it is to be constructed.
Initially, performance standards are favored over design standards, as greater flexibility is allowed in subsequent product design and development.
Design standards exist for thousands of products and processes. They may describe product quality, performance, and dimensions, or discuss test methods for insuring that the product conforms to the given standard.
Government and private sector standards vary. (OVERHEAD 5)
Standards regulated by the government typically focus on protecting health, safety, and the environment.
Private sector standards are completely voluntary, as their use is optional and they are developed through donated efforts.
The use of private sector standards, when required, should be specified in contracts.
Most U.S. standards are produced by developmental committees that consider various points of view.
Standards Development Organizations
Hundreds of U.S. organizations that develop standards can be broken into four categories: (OVERHEAD 6)
professional societies (i.e., the American Society of Mechanical Engineers),
trade associations (i.e., the Electronic Industries Association and the American Gas Association),
testing and certifying organizations (i.e., Underwriters Laboratories and Factory Mutual), and
standards developing organizations (i.e., the American Society for Testing and Materials).
With all of these organizations developing standards, a way to distinguish American national standards must be present. (OVERHEAD 7)
The American National Standards Institute (ANSI) establishes a way for standards developers to have some or all of their standards designated as American national standards.
ANSI accredits organizations that meet specified criteria and also authorizes product certifiers.
ANSI also helps to register assessors for International Organization for Standardization (ISO) 9000 and ISO 14000, which are the international quality and environmental standards, respectively.
The American Society for Testing and Materials (OVERHEAD 8)
The American Society for Testing and Materials maintains more than twenty percent of all U.S. voluntary standards.
Many of these standards are used around the world.
ASTM E8 is used in this lecture.
The standard is called "Standard Test Methods for Tension Testing of Metallic Materials."
Tension tests are used to verify that the tensile properties of a given material are in compliance with the appropriate standard.
This is important from a safety perspective in that the materials may be used for an application that could directly affect people.
For example, the material may be used for constructing a walkway.
If a portion of the manufactured material does not meet the specified codes and regulations, the walkway may collapse, injuring members of the community.
Tensile Testing
Tensile tests provide information on the strength and ductility of materials under uniaxial tensile stresses. (OVERHEAD 9)
According to ASTM, this information can then be used to compare materials, develop alloys, maintain quality control, and assist with some aspects of design.
In a tensile test: (OVERHEAD 10)
A test specimen is placed between two grips of a testing machine and loaded in tension until failure occurs.
Elongation of the specimen’s test section (gage length) is recorded, as well as the loads up to and at failure.
ASTM E8 discusses the standards for conducting a tensile test, including descriptions of the test specimen, the testing equipment, and procedures.
The ASTM standard tension specimen has a 0.500 inch diameter and a gage length of 2.0 inches between the gage marks.
For a correctly designed test specimen, failure will occur where the stress distribution is uniform and the specimen is only subjected to pure tension.
Tensile Test Examples (as per ASTM E8) (OVERHEAD 11)
A standard round test specimen, typically used for testing cast and wrought metallic materials, has the following dimensions:
Gage Length of 2.000 +/- 0.005 inches.
Diameter of 0.500 +/- 0.010 inches.
Radius of fillet, min. of 3/8 inches.
Length of reduced section, min. of 2 1/4 inches.
A rough sketch of a testing machine is shown in OVERHEAD 12.
The test specimen is held in the machine by grips.
The load cell measures the force being placed on the test specimen.
The extensometer measures the elongation of the specimen in the test section.
A linear variable differential transformer (LVDT), usually located in the actuator assembly, also measures the displacement, but of the total system and on a cruder scale.
A tensile test was performed on an aluminum alloy, using a standard round test specimen. (OVERHEAD 13)
From the test data, the gage length was found to be 2.25" long at failure, using the actuator and the extensometer.
From the final gage length measurement, the percent elongation can be found using the following equation (LF is the final length; LO is the initial length):
For this test, the percent elongation is:
(OVERHEAD 14) The load cell indicated that the maximum load was approximately 11760 pounds. The initial area was
Using this area and the maximum load, the ultimate strength can be calculated:
(OVERHEAD 15) The yield strength (sY) can be found using the 0.2% offset method, as shown in the graph. This is performed by drawing a line parallel to the initial linear portion of the stress-strain curve, starting at strain equal to 0.2%. When this line intersects the curve, the yield strength is determined. For this example, sY = 43 ksi.
Engineering strain at failure can be calculated by:
The modulus of elasticity can be calculated using the following equation, and values from the initial straight line portion of the diagram:
Conclusion (OVERHEAD 16)
The proper use of codes and standards can insure the safety of those in contact with the products manufactured in compliance with those standards.
The Professional Engineers’ promise "to hold paramount the safety, health, and welfare of the public" can be upheld with confidence if codes and standards are stringently followed.
Lecture outline adapted from:
Beer, Ferdinand P., and E. Russell Johnston, Jr. Mechanics of Materials. 2nd ed. United States: McGraw-Hill, 1992.
Gere, James M., and Stephen P. Timoshenko. Mechanics of Materials. Boston: PWS Publishing Company, 1990.
Hibbeler, R.C. Mechanics of Materials. Upper Saddle River, NJ: Prentice Hall, 1997.
Leight, Walter, Belinda Collins, and Domenic A. Canonico. "Setting the Standards." Mechanical Engineering February 2000: 46-52.
1999 Annual Book of ASTM Standards, Section 3: Metals Test Methods and
Analytical Procedures
http://www.asme.org/
Engineering Codes and Standards
Standards in engineering specify an adherence to a level or quality that must be maintained to insure the safety of those involved.
Standards promote safety, reliability, productivity, efficiency, and consistency.
The demand for compatibility came from an understanding of the importance of safety.
An example of this occurred in 1904, during a fire in Baltimore, Maryland. More than 1500 structures burned to the ground.
Fire companies came from areas such as New York, but could not help because their hose couplings did not fit the fire hydrants in Baltimore.
Professional Engineers abide by a Code of Ethics.
The primary focus is the first fundamental canon: "to hold paramount the safety, health, and welfare of the public."
Engineers can maintain this focus by adhering to the standards set by the government and the private sector.
Engineers can affect standards by becoming members of engineering organizations which develop and maintain the standards.
Types of Standards
There are two main types of standards:
A performance standard, which specifies what a product is supposed to accomplish, and
A design standard, which describes what the product is made of and how it is to be constructed.
Government and private sector standards vary.
Standards regulated by the government typically focus on protecting health, safety, and the environment.
Private sector standards are completely voluntary, as their use is optional and they are developed through donated efforts.
The use of private sector standards, when required, should be specified in contracts.
Most U.S. standards are produced by developmental committees that consider various points of view.
Standards Development Organizations
Hundreds of U.S. organizations that develop standards can be broken into four categories:
professional societies such as the American Society of Mechanical Engineers
trade associations such as the Electronic Industries Association and the American Gas Association
testing and certifying organizations, two of which are Underwriters Laboratories and Factory Mutual
standards developing organizations of which the American Society for Testing and Materials (ASTM) is a major contributor in the United States.
The American National Standards Institute (ANSI) establishes a way for standards developers to have some or all of their standards designated as American national standards.
ANSI accredits organizations that meet specified criteria and also authorizes product certifiers.
ANSI also helps to register assessors for International Organization for Standardization (ISO) 9000 and ISO 14000, which are the international quality and environmental standards, respectively.
The American Society for Testing and Materials
The American Society for Testing and Materials (ASTM) maintains more than twenty percent of all U.S. voluntary standards.
Many of these standards are used around the world.
ASTM E8 is called "Standard Test Methods for Tension Testing of Metallic Materials."
Tensile Testing
Tensile tests provide information on the strength and ductility of materials under uniaxial tensile stresses.
According to ASTM, this information can then be used to compare materials, develop alloys, maintain quality control, and assist with some aspects of design.
In a tensile test:
A test specimen is placed between two grips of a testing machine and loaded in tension until failure occurs.
Elongation of the specimen’s test section (gage length) is recorded, as well as the loads up to and at failure.
ASTM E8 discusses the standards for conducting a tensile test, including descriptions of the test specimen, the testing equipment, and procedures.
The ASTM standard tension specimen has a 0.500 inch diameter and a gage length of 2.0 inches between the gage marks.
For a correctly designed test specimen, failure will occur where the stress distribution is uniform and the specimen is only subjected to pure tension.
A standard round test specimen has the following dimensions:
Gage Length of 2.000 +/- 0.005 inches.
Diameter of 0.500 +/- 0.010 inches.
Radius of fillet, min. of 3/8 inches.
Length of reduced section, min. of 2 1/4 inches.
Tension
Testing Machine
A tensile test was performed on an aluminum alloy, using a standard round test specimen.
From the test data, the gage length was measured and found to be 2.25" long at failure, using the actuator and the extensometer.
From the final gage length measurement, the percent elongation can be found using the following equation (LF is the final length; LO is the initial length):
For this test, the percent elongation is:
The load cell indicated that the maximum load was approximately 11760 pounds. The initial area was
Using this area and the maximum load, the ultimate strength can be calculated:
The yield strength (sY) can be found using the 0.2% offset method, as shown in the graph. This is performed by drawing a line parallel to the initial linear portion of the stress-strain curve, starting at strain equal to 0.2%. When this line intersects the curve, the yield strength is determined. For this example, sY = 43 ksi.
Engineering strain at failure can be calculated by:
The modulus of elasticity can be calculated using the following equation, and values from the initial straight line portion of the diagram:
Conclusion
The proper use of codes and standards can insure the safety of those in contact with the products manufactured in compliance with those standards.
The Professional Engineers’ promise "to hold paramount the safety, health, and welfare of the public" can be upheld with confidence if codes and standards are stringently followed.
Engineering Codes and Standards
Standards in engineering specify an adherence to a level or quality that must be maintained to insure the safety of those involved.
Standards promote safety, reliability, productivity, efficiency, and consistency.
Historical Codes and Standards
Throughout history, standards have evolved from using the king’s foot and arm as units of measure, to complex standards that guarantee compatibility and interoperability anywhere in the world. At the first meeting of the American Society of Mechanical Engineers in 1880, standardized sizes for screw threads were discussed.
The demand for compatibility came from an understanding of the importance of safety.
An example of this occurred in 1904, during a fire in Baltimore, Maryland. More than 1500 structures burned to the ground.
Fire companies came from areas such as New York, but could not help because their hose couplings did not fit the fire hydrants in Baltimore.
Many jobs have emerged from the need for correlation, and engineers have a responsibility to uphold these high standards.
Professional Engineers abide by a Code of Ethics.
The primary focus is the first fundamental canon: "to hold paramount the safety, health, and welfare of the public."
Engineers can maintain this focus by adhering to the standards set aside by government and the private sector.
Engineers can also affect standards as members of engineering organizations.
Types of Standards
There are two main types of standards:
A performance standard, which specifies what a product is supposed to accomplish, and
A design standard, which describes what the product is made of and how it is to be constructed.
Generally, performance standards are favored over design standards, as greater flexibility is allowed in product design and development.
Design standards exist for thousands of products and processes. They may describe product quality, performance, and dimensions, or discuss test methods for insuring that the product conforms to the given standard.
Government and private sector standards vary.
Standards regulated by the government typically focus on protecting health, safety, and the environment.
Private sector standards are completely voluntary, as their use is optional and they are developed through donated efforts.
The use of private sector standards, when required, should be specified in contracts.
Most U.S. standards are produced by developmental committees that consider various points of view.
Standards Development Organizations
Hundreds of U.S. organizations that develop standards can be broken into four categories:
professional societies (i.e., the American Society of Mechanical Engineers)
trade associations (i.e., the Electronic Industries Association and the American Gas Association)
testing and certifying organizations (i.e., Underwriters Laboratories and Factory Mutual) and
standards developing organizations (i.e., the American Society for Testing and Materials).
With all of these organizations developing standards, a way to distinguish American national standards must be present.
The American National Standards Institute (ANSI) establishes a way for developers to have some or all of their standards designated as American national standards.
ANSI accredits organizations that meet specified criteria and also authorizes product certifiers.
ANSI also helps to register assessors for International Organization for Standardization (ISO) 9000 and ISO 14000, which are the international quality and environmental standards, respectively.
The American Society for Testing and Materials
The American Society for Testing and Materials comprises more than twenty percent of all U.S. voluntary standards.
Many of these standards are used around the world.
ASTM E8 is used for this lecture.
The standard is called "Standard Test Methods for Tension Testing of Metallic Materials."
Tension tests are used to verify that the tensile properties of a given material are in compliance with the appropriate standard.
This is important from a safety perspective in that the materials may be used for an application that could directly affect people.
For example, the material may be used for constructing a walkway.
If a portion of the manufactured material does not meet the specified codes and regulations, the walkway may collapse, injuring members of the community.
Tensile Testing
Tensile tests provide information on the strength and ductility of materials under uniaxial tensile stresses.
According to ASTM, this information can then be used to compare materials, develop alloys, maintain quality control, and assist with some aspects of design.
In a tensile test:
A test specimen is placed between two grips of a testing machine and loaded in tension until failure occurs.
Elongation of the specimen’s test section (gage length) is recorded, as well as the loads up to and at failure.
ASTM E8 discusses the standards for conducting a tensile test, including descriptions of the test specimen, the testing equipment, and procedures.
The ASTM standard tension specimen has a 0.500 inch diameter and a gage length of 2.0 inches between the gage marks.
For a correctly designed test specimen, failure will occur where the stress distribution is uniform and the specimen is only subjected to pure tension.
Tensile Test Examples (as per ASTM E8)
A standard round test specimen, typically used for testing cast and wrought metallic materials, has the following dimensions:
Gage Length of 2.000 +/- 0.005 inches.
Diameter of 0.500 +/- 0.010 inches.
Radius of fillet, min. of 3/8 inches.
Length of reduced section, min. of 2 1/4 inches.
A rough sketch of a testing machine is shown.
The test specimen is held in the machine by grips.
The load cell measures the force being placed on the test specimen.
The extensometer measures the elongation of the specimen in the test section.
A linear variable differential transformer (LVDT), usually located in the actuator assembly, also measures the displacement, but of the total system and on a cruder scale.
A tensile test was performed on an aluminum alloy, using a standard round test specimen.
From the test data, the gage length was found to be 2.25" long at failure, using the actuator and the extensometer.
From the final gage length measurement, the percent elongation can be found using the following equation (LF is the final length; LO is the initial length):
For this test, the percent elongation is:
The load cell indicated that the maximum load was approximately 11760 pounds. The initial area was
Using this area and the maximum load, the ultimate strength can be calculated:
The yield strength (sY) can be found using the 0.2% offset method, as shown in the graph. This is performed by drawing a line parallel to the initial linear portion of the stress-strain curve, starting at strain equal to 0.2%. When this line intersects the curve, the yield strength is determined. For this example, sY = 43 ksi.
Engineering strain at failure can be calculated by:
The modulus of elasticity can be calculated using the following equation, and values from the initial straight line portion of the diagram:
Conclusion
The proper use of codes and standards can insure the safety of those in contact with the products manufactured in compliance with those standards.
The Professional Engineers’ promise "to hold paramount the safety, health, and welfare of the public" can be upheld with confidence if codes and standards are stringently followed.
Obtain a copy of ASTM E8. Answer the following questions. Please reference the section in ASTM E8 where your answers were found.
1. At what temperature should tensile tests be performed?
2. Discuss the accuracy necessary when measuring test specimen dimensions.
3. What factors are used in defining the speed of testing?
(a) How are limits of speed determined?
(b) Why does the testing speed matter?
4. If no speed limitations are listed, what rules apply when determining yield properties and tensile strength?
5. What testing information should be reported when applicable?
6. Why are test standards important?
