PetStep Testing

                                                   
       

PetSTEPTM Destructive Failure Testing

Using Tinus-Olsen Compression Tester

 

Testing Team:

Dr. Fred Barez

David Hemer

Rudha Ben-Yuhmin

San Jose State University

COE and MAE

May 29 2002


Objective:

            To test the “PetSTEPtm” until failure is achieved. Determine maximum allowable load under given testing conditions 

Test Setup:

            PetSTEPtm was mounted on the test bed via two header beams (A) run in parallel to the its side rails. Two 2X4 cross members were used as supports at either end (D). The specimen was tested in a horizontal flat position as a means of achieving maximum bending stress under a concentrated load (see fig.1). The load application footprint was a 6X12(in) block positioned in the center of the PetSTEPtm  (C). A tape measure was placed on the table to measure relative deflection of the load point (B).

     
       
 
 
                   
         

Figure 1: PetSTEPTM Test setup.

                       
 

Procedure:

The head of the testing unit was brought onto the specimen for an initial ten pound pre-load. Then the load was increased in increments of 100 pounds and deflection from initial position was measured from a relative reference point.

   
                 

Figure 2: PetSTEP deflection under 200 pound load

                     
   

Results:

Applied force Vs. deflection data was collected until product failure as shown on the attached plots. (see Excel plots)

   
     

 

 

 

 

 

 

 

 

 

 

 

TEST #1

 

TEST #2

 

LOAD (Lbs)

Deflection (in)

 

LOAD (Lbs)

Dflection #2 (in)

 

10

 

 

0

 

10

 

 

0

 

100

 

 

0.875

 

100

 

 

0.875

 

200

 

 

2

 

200

 

 

1.875

 

300

 

 

3.5

 

300

 

 

3

 

380

 

 

5.5

 

360

 

 

5

 

 

 

 

 

 

 

 

 

 

                 
                   

Figure 3: Excel plots of PetSTEPTM Failure testing

             
           

Observations:

The product seems to have a considerable amount of deflection, primarily due to its material properties. The fracture point for both tests was very consistent. The fist sign of failure came from the outside bottom rails. The side with the ergonomic handle has trouble dealing with the tension in the thin sections. Another notable condition is the plug areas. These areas are inherently weakened by the plughole and showed considerable concern on both test. A “real” world application test was performed during this testing as well, it consisted of pushing a 290 lbs motorcycle up the product into the bed of a pickup truck. During the real test the product achieved considerably less deflection, due to distribution  of the force over a larger surface area.

                                             
                       

Figure 4: Results and “real world” testing

               
             

Conclusions:

The successful mounting of the “PetSTEPTM” on the test table made it easy to achieve the results that are obtained herein. The test data outlined above should be used as a guide to making liability protection clauses in the instructions and safe use portions of the product literature under the specified condition noted in the test process. An average (for a sample of two tests) maximum load that this product can handle is about 370 lbs for the case of a concentrated load at the center of this product. It is our opinion that larger loads may be carried on this product where the loads are more distributed resulting in less deflection to avoid stress concentrations and ultimate damage. In such a case, a distributed load of up to 570 lbs may be carried on this product before any damages occur.  Revisions to design would consist of relocating the plug locations on the molds which would relocate the stress concentrations that were present at several plug positions (E).
 
                         

Figure 5: Plug locations / stress concentrations 

 

 

       
                       

Apendix:

       

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