Engineering Update

Analytical Process

Structural Analysis

The Hands Free Crutch system, as previously stated, is a device which will assist an individual to maneuver around with the use of only a single leg. The majority of individuals who will use this device will be doing so because they have a lower leg injury; for this reason, it is crucial that the device does not experience structural failure as this would cause further injury.

Normal Stress

One mode of stress which the components in the Hands Free Crutch system will experience are normal stresses due to various load types. One possible load type is an axial force acting on a component, to calculate the stress caused by an axial force, equation 1 will be utilized. The other type of loading which a component will experience is a transverse load. Transverse loads cause a bending moment which induces a normal stress on the component, equation 2 will be used to calculate this stress.

1. σaxial=P/A

σaxial: Normal stress (axial);

P: Axial force

A: Cross-sectional area

2. σbend=-(M*y)/I

σbend: Normal stress (bending)

M: Bending moment

I: 2^nd moment of area; y: Distance from neutral axis

Shear Stress

Another mode of stress which the components in this device will experience are shear stresses. The first of two load types which will be considered is a torqueing moment acting on the component. This load type will cause a torsional shear stress which will be calculated using the first equation below. The second type of loading which a component will experience, that induces a shear stress, is a transverse load. This loading scenario will cause a transverse shear stress, this particular stress will be calculated using the second equation below.

1. τ=(T*ρ)/J

τ: Shear stress

T: Torque

J: Polar 2^nd moment of area

2. τ=(V*Q)/(I*b)

τ: Shear stress

V: Shear force

I: 2^nd moment of area

Q: 1^st moment of area

b: Width of cross section

Failure Analysis

After all stress values within each component of the Hands Free Crutch system are calculated, the stress values will be utilized to determine if failure will occur. In order to do so, first all the principal stresses, which include normal and shear stress, will be determined in each component using the equations below.

Finite Element Analysis

In order to run a more in-depth analysis on some high risk parts, Finite Element Analysis (FEA) will be utilized. This process will take place using Creo Parametric, and more specifically Creo Simulate. Using Finite element analysis will help show whether the product will break, wear out, or work the way it was designed. It is called analysis, but in the product development process, it is used to predict what is going to happen when the product is used. FEA will only be used on parts that are deemed high-risk, and those that the team would like a better analysis of.