The science behind steel springback

[bruce1337]

I stumbled upon this little article and though it was fascinating

Bending Basics: The hows and whys of springback and springforward

Simply put, you can define the degrees of springback (D) using the inside bend radius (Ir) and material thickness (Mt), along with a material factor.

D = [Ir / (Mt × 2.1)] × Material factor

The baseline material factor (1.0) is cold-rolled steel; 304 stainless steel has a factor of 3.5; H32 aluminum is 3.0. 

The yield strength of the material has a tremendous influence on the amount of springback that occurs during bending. The higher the yield strength is, the greater the amount of springback. Also notice how the amount of springback increases in proportion to an increase of the inside radius. Variables in springback abound. The stronger (higher tensile) a material is, the greater the springback will be. The sharper the radius is, the less springback there will be (up to a point).

[bruce1337]

To add onto this with my own knowledge from bending. The sharper the V you can get during a kink will make the crush easier by two factors:

1 - slightly longer legs on the bar so you have more leverage
2 - smaller bend radius = less spring back

This is why stainless is so hard on the crush, both because its material properties make it naturally more springy, but also that it bends over a bigger radius.

They did not have data on other steel as it was based on sheet metal bending, but the knowledge is profound.

[jculpepper]

On 11/28/2021 at 1:37 PM, bruce1337 said:

I stumbled upon this little article and though it was fascinating

Bending Basics: The hows and whys of springback and springforward

Simply put, you can define the degrees of springback (D) using the inside bend radius (Ir) and material thickness (Mt), along with a material factor.

D = [Ir / (Mt × 2.1)] × Material factor

The baseline material factor (1.0) is cold-rolled steel; 304 stainless steel has a factor of 3.5; H32 aluminum is 3.0. 

The yield strength of the material has a tremendous influence on the amount of springback that occurs during bending. The higher the yield strength is, the greater the amount of springback. Also notice how the amount of springback increases in proportion to an increase of the inside radius. Variables in springback abound. The stronger (higher tensile) a material is, the greater the springback will be. The sharper the radius is, the less springback there will be (up to a point).

Could you write me a dissertation that I can show to my family explaining why bending stuff isn't for big dumb guys? 

 

In all seriousness, I enjoy geaking out on the math. Any chance your an engineer or math teacher? 

 

Thanks for the intelligent post!

[bruce1337]

3 hours ago, jculpepper said:

Could you write me a dissertation that I can show to my family explaining why bending stuff isn't for big dumb guys? 

 

In all seriousness, I enjoy geaking out on the math. Any chance your an engineer or math teacher? 

 

Thanks for the intelligent post!

I am an analytical chemist, but I have always enjoyed doing deep dives into the physics of things.

I think there is a whole are of uncharted territory when it comes to steel bending if we can get into the physics and chemisty of what happens when we bend. I think a deeper knowledge into that area will open up more doors for new and improved training styles.

[jculpepper]

2 minutes ago, bruce1337 said:

I am an analytical chemist, but I have always enjoyed doing deep dives into the physics of things.

I think there is a whole are of uncharted territory when it comes to steel bending if we can get into the physics and chemisty of what happens when we bend. I think a deeper knowledge into that area will open up more doors for new and improved training 

I am an electrical engineer. So, I get it. I have been pondering using different metal types to work on the different portions of the bend. For example the crush is my weakest part of the bend. 

I mean that's how guys work on their deadlifts. Deficit pulls to help with the lower portion and pin pulls if you have trouble with the lockout. 

 

Maybe I am overthinking it but I am kinda weak and need all the help I can get.

[bruce1337]

2 minutes ago, jculpepper said:

I am an electrical engineer. So, I get it. I have been pondering using different metal types to work on the different portions of the bend. For example the crush is my weakest part of the bend. 

I mean that's how guys work on their deadlifts. Deficit pulls to help with the lower portion and pin pulls if you have trouble with the lockout. 

 

Maybe I am overthinking it but I am kinda weak and need all the help I can get.

I have found that isometric crushes on steel you are trying to finish is a great method of training. 

Lets say you are trying to bend a 5/16 x 7" stainless. You get through the kink and sweep easily but the crush stops you dead, wont move a millimetre further. This bar becomes your ISO bar. When you feel rested and ready you take that bar and crush it every which way till' Sunday . I will usually do my ISO crushes at the end of a session. Eventually, one day out of the blue, that bar will move, and when it does it will be a glorious feeling. You rinse and repeat this method until the bar is at or under 2". Then you wrap a fresh 5/16 x 7" stainless and attempt again. You will most likely finish it or come really close. 

With isometrics you are essentially doing maximum intensity 1rm without moving the bar (yet).

[jculpepper]

28 minutes ago, bruce1337 said:

I have found that isometric crushes on steel you are trying to finish is a great method of training. 

Lets say you are trying to bend a 5/16 x 7" stainless. You get through the kink and sweep easily but the crush stops you dead, wont move a millimetre further. This bar becomes your ISO bar. When you feel rested and ready you take that bar and crush it every which way till' Sunday . I will usually do my ISO crushes at the end of a session. Eventually, one day out of the blue, that bar will move, and when it does it will be a glorious feeling. You rinse and repeat this method until the bar is at or under 2". Then you wrap a fresh 5/16 x 7" stainless and attempt again. You will most likely finish it or come really close. 

With isometrics you are essentially doing maximum intensity 1rm without moving the bar (yet).

Thanks for the advice. Infact I have using the same strategy for the last few weeks. Maybe I'm just a whimp but it seems the iso 's take more than they give. They beat me up pretty good. I will stick with them since they seem to be the go to. I was just curious about ways to get that same level of intensity and keep the bar moving. I have been bending for several Months now and still figuring what will work best for me.

 

I did finish off one of my iso bars the other day. The revenge felt pretty good. 

[Ole' Puller]

On 11/28/2021 at 2:37 PM, bruce1337 said:

I stumbled upon this little article and though it was fascinating

Bending Basics: The hows and whys of springback and springforward

Simply put, you can define the degrees of springback (D) using the inside bend radius (Ir) and material thickness (Mt), along with a material factor.

D = [Ir / (Mt × 2.1)] × Material factor

The baseline material factor (1.0) is cold-rolled steel; 304 stainless steel has a factor of 3.5; H32 aluminum is 3.0. 

The yield strength of the material has a tremendous influence on the amount of springback that occurs during bending. The higher the yield strength is, the greater the amount of springback. Also notice how the amount of springback increases in proportion to an increase of the inside radius. Variables in springback abound. The stronger (higher tensile) a material is, the greater the springback will be. The sharper the radius is, the less springback there will be (up to a point).

Spectacular article brother! This helps to explain why drill rod, stainless steel and heavy quality bolts are the best types of steel to train with for big bends down the road!