P13226: Power Steering Test Stand
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Engineering Analysis

Table of Contents

Extraneous Loading of Torque Sensor


How To Calculate Extraneous Loads
Extraneous Load Factors
Torque Sensor Free Body Diagram

Torque Sensor Free Body Diagram


Based on the Equations and coefficients in the above links from Futek, the 1300 in-lb Torque Sensor selected for this project is limited to 15,000 psi for Maximum Stress. Below are the calculations used to find the estimated expected stress.
These calculations imply that for the worst case scenario estimated for this application, the torque sensor chosen should theoretically support infinite fatigue life for fully reversing loads, while including a factor of safety of greater than 2.

These calculations imply that for the worst case scenario estimated for this application, the torque sensor chosen should theoretically support infinite fatigue life for fully reversing loads, while including a factor of safety of greater than 2.

Servo Shaft Key

The key that will transmit force between the servo and shaft that will lead to the EPS input spline, was analyzed. The analysis was based off of distortion theory as outlined in Shigley's Mechanical Engineering Design. The results show a minimum safety factor of 81 based on a yield strength of 415MPa for 316 cold drawn stainless steel bar.

 Key Analysis

Key Analysis

Slip Shaft Analysis

Slip Shaft Design

Outline of Slip Shaft Solid Model of Slip Shaft
Outline of Slip Shaft

Outline of Slip Shaft

Solid Model of the Slip Shaft.

Solid Model of the Slip Shaft.

Using ANSYS APDL Software, The Slip Shaft was designed based on a 3/4in DD Steering Shaft and Tube combination. Both the Tube (OD 1in) and the shaft (OD .75in) were 6 inches long, with a 3 inch overlap.

Results

The Slip Shaft experiences less than 12000 psi maximum stress under the max specified torque of 67.5 N-m

The Slip Shaft experiences less than 12000 psi maximum stress under the max specified torque of 67.5 N-m

The Maximum Stress occurs on the DD Shaft, pictured above.

The Maximum Stress occurs on the DD Shaft, pictured above.

An end view detailing the radial stress experienced by the Slip Shaft.

An end view detailing the radial stress experienced by the Slip Shaft.


Using the Maximum Yield Stress of 1016 cold drawn Steel, the Shaft has an ultimate yield strength of 50800 psi, providing an approximate factor of safety of 4.2.