Week 1 Spur Gear Challenge

CASE 1-

For the first case in which we have to take a cast iron(ductile) as material for the spur gears and then we have to perform analysis on it.

-So, in this case I take material Ductile Iron grade 120-90-02 and its mechanical properties is noted from matweb site. Its properties are as follows-

Density	7.20g/cm3
Ultimate tensile strength	827Mpa
Tensile strength yield	621Mpa
Poisson ratio	0.28
Youngs modulus	170Gpa

• After feeding this material data, I imported the geometry into the ANSYS.
• During meshing, I have taken the mesh by default just changed the relevance center from coarse to fine. And the mesh that generate is Hexdominal and it can be seen below-

After this whole same process is done which was given in the video and analysis is done by following those steps.

Stress intensity : When fracture occurs, crack develops to form an opening where stress is concentrated more than other areas. So, Engineers are more interested in knowing the maximum stress near the crack tip and whether it exceeds the fracture toughness. In reality, it is difficult to estimate the stresses at these zones. So, Stress Intensity factor K determines whether the crack will grow or not.

Stress Intensity Factor “K” is given by the formula: K=σ √πa where σ is Applied stress and a usually represents the crack width

Results-

In this we done analysis to fine these results-

Total Deformation

30mm (Max)

Equivalent Stress

382.25Mpa (Max)

Stress Intensity

430.83Mpa (Max)

Factor of safety

1.6 (Min)

In this stress intensity is maximum at the where the teethes of two gears come in contact with each other.

CASE 2- In this case we have to take a cast steel as material for the spur gears and then we have to perform analysis on it.

• -So, in this case I take material AISI4340 and its mechanical properties is noted from azom.com. Its properties are as follows-

Density	7.85g/cm3
Ultimate tensile strength	745Mpa
Tensile strength yield	470Mpa
Poisson ratio	0.3
Youngs modulus	210Gpa

-After feeding this material data, I imported the geometry into the ANSYS.

-Mesh is generated as same as that in case 1.

-Results

Total Deformation

30mm (Max)

Equivalent Stress

388.5Mpa (Max)

Stress Intensity

436.51Mpa (Max)

Factor of safety

1.2 (Min)

In this case also the stress intensity is maximum at the place where the teethes of the two gears comes in contact.

CASE 3- In this last case we have to take a cast bronze as material for the spur gears and then we have to perform analysis on it.

• -So, in this case I take material Bronze SAE40 and its mechanical properties is noted from matweb. Its properties are as follows-

Density	8.82g/cm3
Ultimate tensile strength	255Mpa
Tensile strength yield	125Mpa
Poisson ratio	0.3
Youngs modulus	93Gpa

-After feeding this material data, I imported the geometry into the ANSYS.

-Mesh is generated as same as that in case 1.

-Results-

Total Deformation

30mm (Max)

Equivalent Stress

376.3Mpa (Max)

Stress Intensity

417.93Mpa (Max)

Factor of safety

0.33 (Min)

Stress intensity develop at same place as that in case of the above two cases

Comparison between all three cases

	CASE 1	CASE 2	CASE 3
Total Deformation	30mm (Max)	30mm (Max)	30mm (Max)
Equivalent Stress	382.25Mpa (Max)	388.5Mpa (Max)	376.3Mpa (Max)
Stress Intensity	430.83Mpa (Max)	436.51Mpa (Max)	417.93Mpa (Max)
Factor of safety	1.6 (Min)	1.2 (Min)	0.33 (Min)

From above data we can conclude that which material has to be taken for these gears-

Cast iron have more FOS as compare to other cases as the iron have more yield strength as compare to other materials that is 621Mpa therefore it has more FOS than others. We can take cast steel also but iron have more FOS so it will be better to be on safe side. We should not take cast bronze because it has FOS<1 so it will fail under these circumstances.

• - We can also decide whether to take iron or steel as both have FOS>1 on basis of availability, cost and manufacturability.
• -As iron have the least density as compare to steel and bronze so the gears made of iron will be lighter in weight as compare to steel and bronze.

My recommendation will be toward cast iron as the gears made up of this material will more strength, FOS and light weight.