17.3 American Welding Society (AWS) Welding Codes

David Colameco, M.Ed.

During World War I, industry used welding to fabricate for the war effort. In 1919, Adams founded The American Welding Society. According to their “About AWS” page: “as a nonprofit organization with a global mission: “Advancing the science, technology, and application of welding and allied joining and cutting processes worldwide, including brazing, soldering, and thermal spraying.” For the purposes of this discussion, this chapter will focus on welding. This mission statement by AWS shows the broad knowledge and subject areas that the organization covers.

Development of AWS welding codes

AWS has many committees comprising experts and contributors working together to meet the mission described above. These committees come to decisions based on a consensus approach where voting members of the committees vote via ballot. It is a formal process where objections of voting members are discussed, and the public can provide input. Everyone, including you, has the opportunity to address these committees when they meet. To achieve the purpose of AWS, about 200 committees were formed to address various topics where the covers of these documents are color coded such as:

  • Fundamentals (Brown)
  • Qualification and Inspection (Green)
  • Processes (Blue)
  • Industrial Applications (Red)
  • Safety and Health (Yellow)
  • Materials (Tan)
  • Welding Equipment (Purple)

AWS maintains about 300 standards in the subject areas listed above. As you read over this small list of AWS standards, think of all of the possibilities your career can take in structural welding alone! The next few subsections of this AWS section will focus on providing an overview of the following structural codes:

  • AWS D1.1/D1.1M:2020 Structural Welding Code – Steel
  • AWS D1.2/D1.2M:2014 Structural Welding Code – Aluminum
  • AWS D1.3/D1.3M:2018 Structural Welding Code – Sheet Steel
  • AWS D1.4/D1.4M:2018 Structural Welding Code – Reinforcing Steel
  • AWS D1.5/D1.5M:2020 Bridge Welding
  • AWS D1.6/D1.6M:2017 Structural Welding – Stainless Steel
  • AWS D1.7/D1.7M:2010 Structural Welding – Strengthening and Repair
  • AWS D1.8/D1.8M:2021 Structural Welding – Seismic Supplement
  • AWS D1.9/D1.9M:2015 Structural Welding – Titanium

The codes listed above have a forward slash “/” with a repeat of the number and an “M” for metric. This enables one single standard to address both US and metric units rather than having two separate documents for each measurement system. In addition, there is a publication year given just before the colon “:”, which, as of the writing of this chapter, were the latest code versions. If your school, employer, union hall, library, or other organization provides copies of welding standards to read, it is important to request new standards when they come out to show your interest in an up-to-date collection. AWS standards are typically on a five-year publication cycle; however, you may have noticed in the list above that this does not always happen. For example, the D1.7 code hasn’t been revised for over ten years.

Basics of the AWS welding codes

The American Welding Society has recently put in a significant effort to streamline its standards to make them look similar in structure. Generally speaking, the codes listed in the section above have the following chapters, which are called Clauses in AWS standards; these are the Clauses from D1.1/D1.1M:2020:

  • Clause 1 General Requirements
  • Clause 2 Normative References
  • Clause 3 Terms and Definitions
  • Clause 4 Design of Welded Connections
  • Clause 5 Prequalification of WPSs
  • Clause 6 Qualification
  • Clause 7 Fabrication
  • Clause 8 Inspection
  • Clause 9 Stud Welding
  • Clause 10 Tubular Structures
  • Clause 11 Strengthening and Repair of Existing Structures

As a welder who is working towards certification, Clause 6 is the part of the standard that will detail the setup of the certification test, inspection criteria and destructive testing required.

The other standards listed in this chapter have similar structures for Clauses 1 to 8. D1.6 has the same Clauses 1 to 9, while D1.2 and D1.9 have an older structure that is similar but will likely be updated to the structure above in future releases. D1.5 has Clause 5 Workmanship and Clause 6 Technique, which together are similar to Fabrication clauses. During your welding career, if your welding takes you in the direction of a different welding code than you were previously using, it is recommended that you read over the sections pertaining to qualification, fabrication, and inspection at a minimum to better understand the requirements you are welding to.

Uses Of The Aws Welding Codes In Industry Today

AWS codes are used worldwide with varying acceptance depending upon the country. In the United States, the AWS codes are used in all 50 states and inhabited territories. The section discussing WABO mentions that most structural steel in Washington State is done under WABO. Some industries in Washington State may also follow AWS standards for steel construction. WABO does not cover other materials aside from steel. Therefore, most structural welding of other metals, such as aluminum or stainless steel, would require an AWS code. AWS D1.5 Bridge Welding is used for fabrication of bridges:

Twin suspension bridges, known as the Tacoma Narrows Bridge, on a sunny day. Greenery is seen in the foreground, and cars drive over each bridge in the correct direction.
Figure 17.2. Tacoma Narrows Bridges / Photo Credit: Washington State Dept of Transportation, CC BY-NC-ND 2.0

Getting Certified To The Aws Welding Codes

Most community colleges and technical schools offer WABO certification, however some also offer AWS certification testing. As you explore your career options in welding, check out which codes and certifications employers in those career areas use and require.

For the purposes of this chapter, we will focus on the D1.1 certification tests because structural steel is one of the most common career paths. Prior to practicing for a certification test, you are highly encouraged to reach out to the testing facility to get up-to-date information because changes may have occurred to what is written here. Getting certified to AWS D1.1 or WABO will be beneficial to your career because employers know if you have gone through the certification process under one code, you are highly likely to successfully qualify under another code if you are given time to practice. Welders and welding operators are tested by welding on plates or tubular structures depending on the qualification. A list of qualification types is classified as follows in D1.1 Clause 6:

  • complete joint penetration (cjp) Groove Welds for Nontubular Connections
  • partial joint penetration (pjp) Groove Welds for Nontubular Connections
  • Fillet Welds for Nontubular Connections
  • CJP Groove Welds for Tubular Connections
  • PJP Groove Welds for Tubular Connections
  • Fillet Welds for Tubular Connections
  • Plug and Slot Welds for Tubular and Nontubular Connections

Complete joint penetration means that the weld penetrates the base material from one side to the other, in other words the weld bead(s) have been laid down from one side of the base material and built up until they reach the other side of the base material. Partial joint penetration means that the weld only goes part of the way through the base material depth in the joint. Let’s examine each one of these qualification type classifications in more detail.

CJP and PJP Groove Welds for Nontubular Connections

Tubular connections are welds that involve shapes such as pipes and tubes. Nontubular connections are typically flat shapes such as plates. Figure 17.3 below shows the four welding positions for plates with groove welds.

Four groove welding positions are presented. 1G is a flat position. A caption on 1G reads, “The welding position used to weld from the upper side of the joint; the face of the weld is approximately horizontal.” 2G is a horizontal position. The caption on 2G reads, “The position of welding in which the axis of the weld lies in an approximately horizontal plane and the face of the weld lies in an approximately vertical plane.” 3G is a vertical position. The caption on 3G reads, “The position of welding in which the axis of the weld is approximately vertical.” 4G is the overhead position. The caption on 4G reads, “The position in which welding is performed from the underside of the joint.”
Figure 17.3. Groove Welding Positions / Photo Credit: Nicholas Malara, CC BY 4.0

Welders and welding operators qualifying for CJP are qualified for PJP welding. AWS D1.1/D1.1M:2020 Clause 6, Table 6.1 lists the following weld types and positions for qualification tests on plates:

  • CJP 1G                CJP and PJP for Production Plate in the Flat position
  • CJP 2G                CJP and PJP for Production Plate in the Flat and Horizontal positions
  • CJP 3G                CJP and PJP for Production Plate in the Vertical position
  • CJP 4G                CJP and PJP for Production Plate in the Overhead position

The thickness of the plates used in qualification tests determines the thickness of plates a welder is qualified to weld in production as seen in Table 17.1.

Table 17.1. Plate Qualification Ranges

Plate Thickness

Qualification

⅜”

Qualifies the welder for ⅛” to ¾”

⅜” to 1”

Qualifies the welder for ⅛” to twice the thickness of the test plate

1” and over

Qualifies the welder for ⅛” to unlimited thickness

(AWS, D1.1/D1.1M:2020, Table 6.11)

Visual acceptance criteria for welder and welding operator testing are listed by area below. For welders interested in qualifying for production plate welding, please contact the testing facility and/or consult the latest version of D1.1 for the specific acceptance criteria. The acceptance criteria are broken down into the following areas in Table 8.1 of AWS D1.1/D1.1M:2020:

  • Crack Prohibition
  • Weld/Base Metal Fusion
  • Crater Cross Section
  • Weld Profiles
  • Time of Inspection
  • Undersized Welds
  • Undercut
  • Porosity

These areas listed above provide a general idea of what topics an inspector is comparing your weld to in order to determine if it is acceptable or not visually. Following a visual inspection that meets the criteria, your weld would undergo a bend test in accordance with D1.1 or the standard you are qualifying for. There are face bends, root bends, and side bends.

The illustration below shows a test plate and the locations where face bends are cut out for testing. In D1.1, there is a space between the bend specimens.

Test specimen locations are indicated on the test plate. These locations for side bends, tension tests, and macroetch, are used by the destructive tester to cut specimens to the appropriate size from
Figure 17.4. Test Specimen Directions / Photo Credit: Nicholas Malara, CC BY 4.0

Once the specimens are cut out of the welder’s test plates, they are bent in a bend test machine similar to the one shown below. Some test machines are manually operated, while others are powered electrically or through air pressure (pneumatically).

An illustration of a bend test machine on pneumatic power. The machine looks a bit like a guillotine in that it has a pneumatic lever that lowers a tool that puts pressure against the weldment being tested and forces it into a U-shaped groove at the base of the machine. The downward pressure of the bending tool forces the metal to bend.
Figure 17.5. Bend Test Machine / Photo Credit: Nicholas Malara, CC BY 4.0

The use of a manual or machine bend testing machine typically depends on the budget and number of bend tests performed in a given period of time. A manual bend tester would be more ideal for performing a few bend tests, that are also done infrequently. For example, if you were testing your own welds at home about once or twice a year, then a hand operated system would make sense. If you were a company or school that was performing dozens of bend tests a month, then a machine, like the one in the following figure, makes more sense from a productivity standpoint.

A bend test machine with a weldment placed over the U-shaped groove is being lowered onto the weldment in preparation for bending it into a U.
Figure 17.6.Photo Credit: U.S. Department of Transportation, Federal Highway Administration, PD

The material specimens are placed into the machine between the plunger and the U-shaped die as seen above. To achieve a root or face bend depends on which side is facing away from the plunger. To get a root bend, the root faces away from the plunger and is visible on the outside of the bend; this causes the root portion of the weld to stretch. To get a face bend, the weld face faces away from the plunger and is visible on the outside of the bend; as with the root bend, this causes the face portion of the weld to stretch.

An illustration featuring root and face bends. Both illustrations show a U-shaped weldment. On the left, the root bend shows shading indicating the weld at the base of the U facing the space at the top of the U. The root of the weld is facing the outside of the U, indicating a root bend tests. On the right, the shaded weld portion of the illustration shows the face of the weld facing the outside of the U, indicating a face bend test.
Figure 17.7. Root and Face Bends / Photo Credit: Nicholas Malara, CC BY 4.0

A “perfect” bend test would show a continuous surface free of any changes such as tears and holes from porosity or slag inclusions, also known generally as discontinuities. The inspector will check the surface of the bend for any discontinuities, such as tears and holes, and compare the size, shape, and quantity to the code’s visual acceptance criteria. The bend test passes if a discontinuity is smaller than the acceptance criteria. If the discontinuity is larger than the acceptance criteria, then the discontinuity is too large, and it is a defect; the bend test fails.

Fillet Welds for Nontubular Connections

Fillet welds made on plates are non-tubular connections. Figure 17.8 below shows four test positions for fillet welds on “T” joints.

Fillet weld test positions 1F, 2F, 3F, and 4F are illustrated. There are captions designing each weld position. All of these welds are T-shaped, where one piece of metal and welded halfway across another perpendicularly. 1F is flat position, and the caption reads, “The welding position used to weld from the upper side of the joint; the face of the weld is approximately horizontal. 2F is the horizontal position, and the caption reads, “The position in which welding is performed on the upper side of an approximately horizontal surface and against an approximately vertical surface.” 3F is the vertical position. The caption reads, “The position of welding in which the axis of the weld is approximately vertical.” 4F is the overhead position. The caption reads, “The position in which welding is performed from the underside of the joint.”
Figure 17.8. Fillet Welding Positions / Photo Credit: Nicholas Malara, CC BY 4.0

Welders and welding operators qualifying for CJP are qualified for PJP welding. AWS D1.1/D1.1M:2020 Clause 6, Table 6.1 lists the following weld types and positions for qualification tests on plates:

Table 17.2. CJP Fillet Positions and Qualification

Weld Position

Qualification

CJP 1F

CJP and PJP for Production Plate in the Flat position

CJP 2F

CJP and PJP for Production Plate in the Flat and Horizontal positions

CJP 3F

CJP and PJP for Production Plate in the Vertical position

CJP 4F

CJP and PJP for Production Plate in the Overhead position

Note: From AWS D1.1/D1.1M:2020 (Clause 6, Table 6.1). Copyright 2020 by the American Welding Society.

The thickness of the plates used in qualification tests determines the thickness of plates a welder is qualified to weld in production. AWS D1.1/D1.1M:2020 Table 6.11 lists “Fillet Option 1” thickness as ½” which qualifies the welder for ⅛” to unlimited thickness.

This test requires both a macroetch and a fillet weld break test. The fillet weld break test is shown below, where a force is applied to the fillet weld. If the fillet does not fail under the required force, then the test passes.

An illustration of a fillet rupture test. A fillet weld is turned so that the weld on the fillet is facing up so that the weldment makes a triangle like a camping tent. The weldment is placed on a block. A red arrow labeled force is pointing down at the fillet, demonstrating how force would be applied right over the weld.
Figure 17.9. Fillet Rupture Test / Photo Credit: Nicholas Malara, CC BY 4.0

The macroetch test is performed by cutting the T-Joint perpendicular to the weld bead. In Figure 17.9 imagine that the arrow labeled “Force” was a cutting blade that cut the T-joint in half to expose the fillet weld internals. Once the cut is made the surface is prepped and an acid is applied to etch the metal. This makes the grain structure of the weld and heat affected zone show making it easier to inspect. Figure 17.10 shows a macroetch of a T-joint.

Macroetch of a T-joint is shown where a weld joint has been cut perpendicular to the direction of welding to expose a cross section of the weld beads. This surface is then treated with an acid solution to highlight the differences in the microstructure of the metal. This image has been enhanced with special lighting contrasts to show the heat affected zones and the individual grains in the weld metal.
Figure 17.10. Macroetch Of A T-Joint / Photo Credit: U.S. Department of Transportation, Federal Highway Administration, PD

This test requires that the largest single bead fillet weld be made on one side of the T-joint and the minimum multipass beads be made on the other side as shown above. The acceptance criteria are:

  • Fillet welds shall have fusion to the root of the joint but not necessarily beyond
  • Minimum leg size shall meet the specified weld size.

If the weld passes the acceptance criteria the macroetch test passes. The legs of the weld are the size of the weld along the base material prior to welding. The legs are denoted by the “Proper Size” labels in Figure 17.11 below.

An illustration of a T-Joint with labels for the parts of a T-Joint. Two pieces of metal plate are welded perpendicular to one another. The joint is in the horizontal position, and the weld bead is to the right of the perpendicular piece of metal. The weld is a rounded trianglular shape, forming a right-angle triangle where the two pieces are welded together. Two labels at the base of the image, pointing to the bottom of the weld bead read sufficient penetration to root and complete fusion. The label complete fusion also appears at the top of the weld bead where it meets the perpendicular piece of metal. Two other labels on the weld bead read good profile and satisfy undercut requirements. Finally, four dotted lines showing the size of the weld bead demonstrate the proper size of the weld, which demonstrates how the inspection would align the measurement with the edge of the bead looking at the distance between the top of the weld and the base of the weld as well as the edge of the welded metal to the outside of the weld bead.
Figure 17.11. Parts of a T-Joint / Photo Credit: Nicholas Malara, CC BY 4.0

CJP and PJP Groove Welds for Tubular Connections

Welders and welding operators qualifying for CJP are qualified for PJP welding. AWS D1.1/D1.1M:2020 Clause 10, Table 10.12 lists the following weld types and positions for qualification tests on plates:

Table 17.3. Groove Weld Positions and Qualification

Plate Position

Qualification

1G Rotated

CJP and PJP for Production Pipe in the Flat position

2G

CJP and PJP for Production Pipe in the Flat and Horizontal positions

5G

CJP and PJP for Production Pipe in the Flat, Horizontal, Vert. position

6G

CJP and PJP for Production Plate in All Positions

(2G + 5G)

CJP and PJP for Production Plate in All Positions

Note: From Structural Welding Code – Steel. AWS D1.1/D1.1M (Clause 10, Table 10.12), 2020. Copyright 2020 American Welding Society.

The size and thickness of the pipes used in qualification tests determines the size and thickness of plates a welder is qualified to weld in production. AWS D1.1/D1.1M:2020 Table 10.13 lists three size and thickness combinations:

Table 17.4. Size and Thickness of Pipes in Qualification Tests

Pipe Size*

Qualification

≤ 4” Pipe, Unlimited Thick

Qualifies ¾” to 4” Pipe for ⅛” to ¾” Thickness

> 4” Pipe, ≤ ⅜” Thickness

Qualifies 4”* to Unlimited Pipe for ⅛” to ¾” Thickness

> 4” Pipe, < ⅜” Thickness

Qualifies 4”* to Unlimited Pipe for 3/16” to unlimit Thickness

Note. The minimum pipe size qualified shall be ½ the test diameter or 4”, whichever is greater. AWS D1.1/D1.1M:2020 (Table 10.13). Copyright 2020 American Welding Society.

It is important to note that Table 10.13 is rather extensive; welders wishing to qualify on tubular connections are highly encouraged to speak with their training facility, testing facility and to consult AWS D1.1/D1.1M:2020 Table 10.13 or the latest version of D1.1 for up to date information about your certification test and its requirements.

Groove welds made on tubular connections are shown in Figure 17.12 for various positions.

An illustration of groove welding positions in tubes. There are four separate illustrations labeled 1G, 2G, 5G, and 6G. The caption on 1G reads, “Horizonatal rolled position. The position of a pipe joint in which the axis of the pipe is approximately horizontal, and welding is performed in the flat position by rotating the pipe.” The caption on 2G reads, “Vertical position. The position of a pipe joint in which welding is performed in the horizontal position and the pipe is not rotating during welding.” The caption on 5G reads, “Horizontal fixed position. The position of a pipe joint in which the axis of the pipe is approximately horizontal and the pipe is not rotated during welding.” The caption on 6G reads, “Inclined position. The position of a pipe join in which the axis of the pipe is approximately at an angle of 45 degrees to the horizontal and the pipe is not rotated during welding.”
Figure 17.12. Groove Welding Positions in Tubes / Photo Credit: Nicholas Malara, CC BY 4.0

Fillet Welds for Tubular Connections

Fillet welds made on tubular connections are shown in Figure 17.13 below.

Four fillet welding positions on tubular connections are illustrated. The positions include 1F, 2F, 4F, and 5F. All illustrations start with a tube welded to a flat piece of metal, similar to a T-Joint, but the tube is not flat. The caption on 1F reads, “Flat position. The welding position used to weld from the upper side of the joint; the face of the weld is approximately horizontal and the pipe is rotated during welding.” The caption on 2F reads, “Horizontal position. The position in which welding is performed on the upper side of an approximately horizontal surface and against an approximately vertical surface and the pipe is not rotated during welding.” The caption on 4F reads, “Overhead position. The position in which welding is performed form the underside of the joint and the pipe is not rotated during welding.” The caption on 5F reads, “Multiple position. The position in which the axis of the pipe is approximately horizontal and the pipe is not rotated during welding.”
Figure 17.13. Fillet Welding Positions / Photo Credit: Nicholas Malara, CC BY 4.0

Welders and welding operators qualifying for CJP are qualified for PJP welding. AWS D1.1/D1.1M:2020 Clause 10, Table 10.12 lists the following weld types and positions for qualification tests on plates:

Table 17.5. Qualification Tests on Plates

Weld Test Position

Description

1F

Fillets for Production Pipe in the Flat position

2F

Fillets for Production Pipe in the Flat and Horizontal positions

2F Rotated

Fillets for Production Pipe in the Flat and Horizontal positions

4F

Fillets for Production Plate in the Flat, Horizontal,Overhead positions

5F

Fillets for Production Plate in All positions

The thickness of the plates used in qualification tests determines the thickness of plates a welder is qualified to weld in production. AWS D1.1/D1.1M:2020 Table 6.11 lists three plate thicknesses:

  • Unlimited Size, ≥ ⅛”
  • Qualifies the welder for diameter pipe tested to unlimited
  • ⅛” to unlimited wall thickness
  • 30 to unlimited dihedral angle

A dihedral angle is the angle measured in a plane perpendicular to the line of the weld, to the tangents of the pipe surfaces being welded together. This is a rather complicated angle to describe in words; please see the first Figure in Annex Q of AWS D1.1/D1.1M:2020. As you look at this Figure note that the toughest part to weld is where the local dihedral angle is the smallest while the easiest part of the weld to access is where the local dihedral angle is the largest.

Plug and Slot Welds for Tubular and Nontubular Connections

Plug and slot welds are used to join two metal surfaces together where there normally isn’t a joint or seam to weld them together. Imagine two very large plates that are more than 10’ by 10’ that you want to weld together. If you only welded them at the edges, the two plates might come apart at the center if they are oriented parallel to the ground because they will sag under their own weight. To prevent this sagging you could cut holes or slots in the area away from the edge and weld the two plates in more locations to join them across the entire faying surface. The faying surface is the surface where two pieces of metal come in contact with each other.

Figure 17.14 and Figure 17.15 show plug and slot welds respectively. These figures provide the instructions to first weld a fillet weld around the inside of the plug or slot cutout and then fill as necessary.

Welders and welding operators qualifying for plug and slot welding will refer to AWS D1.1/D1.1M:2020 Clause 6, Table 6.10 lists the following statement about qualifications:

  • Plug: Qualifies Plug and Slot Welding only for the Positions Tested

For thicknesses tested and thicknesses qualified, D1.1/D1.1M:2020 Table 6.11 lists:

  • ⅜” Plate: Qualifies for ⅛” to Unlimited Thickness
a plug joint which consists of a tapered hole in a piece of metal that is being welded to another piece of base material.
Figure 17.14. Plug Joint In Flat Position / Photo Credit: Nicholas Malara, CC BY 4.0
Slot Joint. Similar to a plug joint with the exception that the hole is elongated instead of circular.
Figure 17.15. Slot Joint In Flat Position / Photo Credit: Nicholas Malara, CC BY 4.0

Attributions

  1. Figure 17.2: Tacoma Narrows Bridges by Washington State Dept of Transportation is released under CC BY-NC-ND 2.0
  2. Figure 17.3: Groove Welding Positions by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  3. Figure 17.4: Test Specimen Directions by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  4. Figure 17.5: Bend Test Machine by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  5. Figure 17.6: Test setup by U.S. Department of Transportation, Federal Highway Administration in the Public Domain; United States government work
  6. Figure 17.7: Root and Face Bends by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  7. Figure 17.8: Fillet Welding Positions by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  8. Figure 17.9: Fillet Rupture Test by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  9. Figure 17.10: Photo. Example macroetch of a T-joint mockup. by U.S. Department of Transportation, Federal Highway Administration in the Public Domain; United States government work
  10. Figure 17.11: Parts of a T-Joint by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  11. Figure 17.12: Groove Welding Positions in Tubes by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  12. Figure 17.13: Fillet Welding Positions by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  13. Figure 17.14: Plug Joint In Flat Position by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
  14. Figure 17.15: Slot Joint In Flat Position by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
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Introduction to Welding Copyright © by David Colameco, M.Ed. is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.