Torsional strength of shaft 35 mm dia grade 1020 and 4140

In summary, according to research, the ultimate tensile strength of 1020 grade steel is 710 MPa, while the UTS for 4140 grade is 1080 MPa. However, the torsional strength of 1020 grade is only .6 of the UTS for 4140 grade. So, if you are concerned with torsional strength, you may want to consider upgrading to a material with a higher UTS.
  • #1
yhshah
1
0
I have a grade specific query. We are currently using 35 mm dia shaft of 1020 grade steel. We want to upgrade to 4140 steel of same diameter. Researching on google and this forum i found out the ultimate tensile strength of 1020 grade is 710 MPa and UTS of 4140 grade is 1080 MPa. But that's general Strength i want to calculate Torsional strength for 35 mm dia and length of 680 mm for both the grade. how do i make comparison ? Urgently required the solution so thanking all of you in advance...I also read Torsional strength is .6 of UTS but does it apply to all grade of steel ?
 
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  • #2
For torsion you're going to want to compare your calculated stress numbers to the shear strength of the material. There are general tables which relate shear strength to tensile strength if you're material properties don't explicitly state the number. This table may be useful to get your shear strength:
http://www.roymech.co.uk/Useful_Tables/Matter/shear_tensile.htm
 
  • #3
You might also want to check the values listed here.

http://www.matweb.com/

You can calculate the shear modulus with knowledge of the elastic modulus and Poisson's ratio.

Here is the equation for that.

G = E / (2*(1 + v))

where

E is the elastic modulus
v is Poissons ratio


Thanks
Matt
 
  • #4
You may want to double check what material properties you currently have. 700 MPa for Sut sounds a bit too high for plain old 1018 or 1020.

Have you considered just a heat treatment instead of a material change?
 
  • #5
Off topic:

Fred, I have to ask you here because you can't accept messages. What is your avatar picture of? (Not the one Kurt Russel from Big Trouble in Little China.)

lol

Thanks
Matt
 
  • #6
It's a picture of myself with two fellow hookers in Suadia Arabia for Desert Shield on the ramp of our aircraft.
 
  • #7
Ohh you mean those kind of hookers ... yeah there cool too. LOL

Matt
 

1. What is the difference between grade 1020 and 4140 for torsional strength of a 35 mm diameter shaft?

Grade 1020 and 4140 are both commonly used grades of steel in industrial applications. However, they have different chemical compositions and mechanical properties, which can affect their torsional strength. Grade 1020 is a low carbon steel with a maximum carbon content of 0.20%, while grade 4140 is a medium carbon steel with a maximum carbon content of 0.40%. This difference in carbon content leads to a difference in hardness and strength, with grade 4140 being stronger and more suitable for high-stress applications such as shafts.

2. How is the torsional strength of a shaft calculated?

The torsional strength of a shaft is calculated using the formula T = (π/16) * S * d^3, where T is the torque in Nm, S is the shear stress in MPa, and d is the diameter of the shaft in meters. This formula takes into account the maximum shear stress that a material can withstand before failure and the size of the shaft.

3. What factors can affect the torsional strength of a 35 mm diameter shaft?

There are several factors that can affect the torsional strength of a 35 mm diameter shaft, including the material grade, the heat treatment process, the surface finish, and the design of the shaft (such as the shape and length). Other external factors such as temperature and corrosive environments can also impact the torsional strength of a shaft.

4. How does the heat treatment process affect the torsional strength of a shaft?

The heat treatment process plays a crucial role in determining the torsional strength of a shaft. Heat treatment involves heating the steel to a specific temperature and then cooling it down at a controlled rate. This process can alter the microstructure of the steel, resulting in changes in its mechanical properties, including its torsional strength. For example, quenching and tempering can increase the strength of a shaft, while annealing can improve its ductility.

5. Can the torsional strength of a 35 mm diameter shaft be increased?

Yes, the torsional strength of a 35 mm diameter shaft can be increased by selecting a higher grade of steel, optimizing the heat treatment process, and improving the design of the shaft. Other methods such as shot peening, cold rolling, and surface coatings can also be used to enhance the torsional strength of a shaft. However, it is essential to consider the trade-offs between strength, cost, and other factors to determine the most suitable approach.

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