Week 1 Spur Gear Challenge

Material Effect on Spur Gear Simulation

We must compare these materials for Equivalent Stress, Total Deformation and Stress Intensity.

Some of the Properties of these materials are:

Materials	Cast Iron	Cast Steel	Cast Bronze
Density(Kg/m3)	7130	7820	8810
Tensile Yield (Mpa)	344	349	144
Tensile Ultimate (Mpa)	548	505	267

In all three cases, the maximum deformation is same which is equal to 30 mm, so we can’t decide about material based on total deformation.

Equivalent Stress Comparison:

By going through results, and comparing them with their respective mechanical properties we can conclude following;

a)Cast bronze Spur gear will FAIL because maximum stress(452.72 Mpa) exceeds Ultimate strength(267 Mpa).

b)Cast Steel Spur gear will FAIL because maximum stress(521.73 Mpa) exceeds Ultimate strength(505 Mpa).

c)Maximum stress induced in Cast Iron Spur is 510.53 Mpa , which is lower than its ultimate strength(548 Mpa).i.e Cast Iron can sustain the load, but Plastic Deformation will take place.

Location For Possible Fracture:

In all three cases, the maximum stress occurs at the contact point between 2 teeths. All the three materials being brittle will fail by fracture only. So, location for possible fracture will be at contact point, shown as maximum stress location in above figure.

What is Stress Intensity ?

Stress Intensity is about knowing when a crack present in a component becomes Critical. Numerically it is denoted by Stress Concentration Factor(K),

K = (Geometric Factor)*(stress)*(pi*CrackLength)^0.5

The stress Intensity factor is a concept in fracture Mechanics that is used to measure the stress concentration at the crack tip.

In safety design, it is compared to a critical value and evaluate whether a component or structure is prone to fracture. The critical value is typically a material parameter.

Stress is to Strength as stress intensity is to Fracture Toughness.

Stress Intensity Comparison:

As we are unaware of any crack present in this problem, so stress intensity will be maximum at the same location where equivalent stress is maximum.

Material Recommendation:

Based on the results obtained for given loading Condition and comparing the equivalent stress values, only Cast Iron Ductile has Ultimate Strength value greater than maximum induced stress .

Select Cast Iron Ductile.

Attachments

pdf Report.