Independent welding consumables professional
- FMA
- The Fabricator
- FABTECH
- Canadian Metalworking
Categories
- Additive Manufacturing
- Aluminum Welding
- Arc Welding
- Assembly and Joining
- Automation and Robotics
- Bending and Forming
- Consumables
- Cutting and Weld Prep
- Electric Vehicles
- En Español
- Finishing
- Hydroforming
- Laser Cutting
- Laser Welding
- Machining
- Manufacturing Software
- Materials Handling
- Metals/Materials
- Oxyfuel Cutting
- Plasma Cutting
- Power Tools
- Punching and Other Holemaking
- Roll Forming
- Safety
- Sawing
- Shearing
- Shop Management
- Testing and Measuring
- Tube and Pipe Fabrication
- Tube and Pipe Production
- Waterjet Cutting
Industry Directory
Webcasts
Podcasts
FAB 40
Advertise
Subscribe
Account Login
Search
Consumables Corner: Breaking down CTOD and CVN testing
- By Nino Mascalco, Rob Koltz, and Steve Sigler
- May 13, 2016
- Article
- Consumables
Q: We're a job shop and much of our work is customized or unique. Because of this, we have to work with multiple welding codes and sometimes we have to verify welding procedures. We have been bidding on some new projects that have welding crack tip opening displacement (CTOD) requirements. How is CTOD different from Charpy V-notch (CVN) testing, and is it better?
A: That's a great question, so let's look at what each test is typically used for, how the tests differ, and what the results mean.
Neither test is better than the other, as each provides different information concerning the material or weld. Simply put, they are similar because they are used to measure the material's resistance to failure in the presence of a known flaw. CVN tests are commonly used for shipbuilding, bridge and structural, pressure vessel, and construction and mining equipment, whereas CTOD tests are typically used for offshore oil and gas platform building among other applications.
The most common toughness test used is the CVN test. It is performed by taking several small machined samples from the test piece and breaking them with impact at the minimum operating temperature for the part. CVN testing is a relatively inexpensive and straightforward test that measures qualitative values.
Results from a CVN test verify that the operating temperature did not fall below the material’s ductile-brittle transition temperature. Why is this important? Because when a material is utilized below this temperature, it is prone to brittle failure. A brittle failure means there will be little or no warning before the material catastrophically fails. This is similar to a piece of glass or ice breaking when force is applied. This type of failure mechanism must be avoided at all costs.
CTOD testing is performed on a sample that is representative of an actual part thickness (or scaled appropriately) and is subjected to in-service loading conditions and temperatures. The test part has an opening machined into it along with a fatigue crack of known dimension. The piece is then placed under a gradual load, reflecting service conditions until the crack sufficiently opens or cleaves, which may be either partial or complete failure.
The information that is of interest is the load at failure, displacement of the opening (width) at the time the crack propagated. This information, along with load/displacement data collected throughout the test loading, is then used to determine the material's toughness. There is considerably more analysis of the testing variables, which are simulating conditions that are required for accurate CTOD tests, but that is not the focus of this column.
The results from a CTOD test can help determine or predict when necessary repairs are needed to a structure. In many cases, a small crack in a structure doesn't mean it will fail or that it requires immediate repair. Being able to schedule repairs when deemed necessary can save time and potentially tens of thousands of dollars or more in lost production. The CTOD test saves downtime and unnecessary repairs, and it reduces the overall costs to maintain a structure.
About the Authors
Rob Koltz
Application Engineer
411 S. Ebenezer Rd.
Florence, 29501
636-485-2253
Steve Sigler
Application Engineer
411 S. Ebenezer Rd.
Florence, South Carolina 29501
636-485-2253
About the Publication
Related Companies
subscribe now
The Welder, formerly known as Practical Welding Today, is a showcase of the real people who make the products we use and work with every day. This magazine has served the welding community in North America well for more than 20 years.
start your free subscription- Stay connected from anywhere
Easily access valuable industry resources now with full access to the digital edition of The Fabricator.
Easily access valuable industry resources now with full access to the digital edition of The Welder.
Easily access valuable industry resources now with full access to the digital edition of The Tube and Pipe Journal.
Easily access valuable industry resources now with full access to the digital edition of The Fabricator en Español.
- Podcasting
- Podcast:
- The Fabricator Podcast
- Published:
- 03/05/2024
- Running Time:
- 65:35
After Ludlow Manufacturing Inc. (LMI) received The Fabricator's 2024 Industry Award, Todd Ludlow, founder and president of the...
- Trending Articles
A welding instructor’s career path to working with metal
Urban Steel Rockstars festival will highlight welding and steel industry
Keys to adopting welding automation successfully
Aluminum Etc.: You can cut aluminum on a CNC plasma system
Portable MIG welding machines offer automatic setup
- Industry Events
NASCC: The Steel Conference
- March 20 - 22, 2024
- San Antonio,
The Fabricator's Manufacturers & Suppliers Event (MSE)
- March 26, 2024
- Schaumburg, IL
Coil Processing Workshop & Tours
- April 2 - 3, 2024
- Corpus Christi, TX
GOLF4MFG South
- April 15, 2024
- Charlotte, NC
16th Annual Safety Conference
- April 30 - May 1, 2024
- Elgin,