PawsUp: Pet Elevator

Static Failure Analysis

A static analysis was performed on the platform, scissor arms, and base since they were the primary load-bearing structures. 

To the right is an image representing some of the hand calculations we did to begin our static analysis. We later conducted the same analysis using Solidworks FEA to double check our stress values.

• Platform bending stress: 2,100 psi (SF = 4.29)

• Scissor arm compression: 843.75 psi (SF = 47.41)

Buckling Analysis

Buckling failure analysis was performed on the scissor arms, which act as slender compression members in the lift. Each arm was modeled to carry a load of 50 lb at the minimum operating angle of 10 degrees. 

A material comparison between 4130 steel and 6061-T6 aluminum revealed that aluminum provided nearly 50% weight savings and a lower cost, while still meeting strength requirements.

• Critical slenderness ratio calculated: 70.25

• Minimum required thickness: 0.474 inches

• Safety factor about weak axis: 2.5

Fatigue Analysis

A fatigue failure analysis was performed to ensure the scissor arms could withstand cyclic loading from repeated lifting operations. 

The 6061-T6 aluminum arms were analyzed with the stress concentration from the pivot hole taken into account, using a fatigue stress concentration factor of 2.06. Using the calculated stress and the S-N curve of the material, we found that the arms have an effectively infinite cycle for their intended use.

• Scissor arm fatigue life: 4.51x10^10 cycles (infinite life)

• Bolt fatigue safety factor: 16.33

Connection Design

Static and fatigue failure analyses were conducted for our bolts, and we analyzed the critical bolts and the middle and corner connection points.

• Bolts: 7/16"-14 UNC Grade 5 steel

• Static failure SF: 91.81

• Joint separation SF: 17.37