American Welding Society Forum
AWS D1.1 shows the dimensions of bending equipment (rollers) which is relevant to a 3/8" specimen. We are trying to qualify a 1/4" welds on Q&T steel plate.
Logic tells me that the bending equipment dimensions should be proportional to the qualified plate's thickness (let's say roller diameter of around 1.5" instead of 2.5") in order to firmly bend the plates, but I haven't found a reference for that in the code.
What do you think?
The bending radius is based upon the specified or actual yield strength of the base metal. I haven't used one the the fancy wrap around coupon benders but I think you would have to size the roller for your base material yield strength and not the specimen thickness. My plunger type coupon bender is made with round bar vs rollers. See AWS D1.1:2015, Fig 4.12 for the wrap around roller diameters and Fig 4.13 for the plunger diameter and spacings. Regardless of the type of bender, the higher the yield, the larger the bend radius.
The radius of the bend mandrel is a function of both the test specimen thickness and the yield strength of the base metal. The wrap around test fixture is the easiest bending machine to use when multiple base metal types, thicknesses, and yield strengths are tested.
Typically, the cam follower is just one size. The bend mandrel is what the test specimen is wrapped around, so it acts as the pivot point of the bending machine. They aren't that hard to design or build and a lot less expensive than having several different plunger and die sets to accommodate all the different thicknesses and yield strengths you will encounter.
Thanks a lot for replying guys. As always you are very helpful.
The wraparound bend test seems like the right solution for multiple use. I once built one for aluminium, I might change the design to meet the current situation.
If I understand the wraparound figure (4.12 on d1.1 2015) correctly, the bend mandrel changes only according to the material's yield strength and not it's thickness. That's interesting.
I'm still trying to figure out what does the sentence:
"Any convenient means may be used to move the plunger member with relation to the die member" (22.214.171.124). When dealing with thin plates, in order to avoid sliding/distance between the specimen and the plunger, what means can one use? Spacers laying between the specimen and the shoulders?
D1.1 presupposes the the text coupon is 3/8-inch thick, whether it is a face and root bend or a side bend.
Working with other standards makes it more likely you will bend materials of different thicknesses. They typically provide an equation to calculate the diameter or radius of the bend mandrel.
You have use something to prevent the bend specimen fixed so it doesn't move when you "wrap" it around the mandrel.
You can use move or wrap the specimen around the mandrel manually (long lever) or hydraulics, i.e. a cylinder or motor.
Thanks again Al,
Can you specify in which standard can I find such a bending equation?
I see something that might be helpful to you an AWS B2.1 2009 revision.
Notes for Figures
ASME also includes the equation
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