Assignment

1. Students will run the experiment in their lab groups.  Each group will conduct a three-point bending test using the Instron 4469 to determine the fully plastic bending load for the specimen.
    
2. Groups will use the results from this test and those obtained from their previous tension and torsion tests on steel to estimate which failure theory is best suited for the test material.
    
   • Sample Results using Instron's Bluehill software
   • Sample Calculations
   • Sample Results using Instron's Series IX software
   • Sample Calculations
      
3. Groups will also examine failed components.

   
    

   • Each group should select three failed items.
     • sorted by topic
     • sorted by number
   • Fill out the Preliminary Failure Assessment, using the Mechanical Failure Mode Taxonomy, and give the assessment to your teachers before you leave.  
   • On your own paper, sketch the failed items and write down your observations.  Note dimensions, markings, corrosion, discolorations, holes, notches, scratches, dents, etc.
   • You might want to consider the following as you examine the items.  
      
     • What kind of material(s) is the item made from?
     • What does the fracture surface look like?  Is it smooth, rough, flat, angled, etc?
     • What was the item used for?
     • In terms of force and moment, how do you think it was loaded?  Drawing a free-body diagram would be one way to do this.
     • What stresses would be caused by these loads?  How do these stresses compares to the material's limiting stresses?
     • What are the limiting stresses (yield, ultimate, fracture, etc) for this material?  Matweb is a convenient reference for this.
     • Are there features such as holes, fillets or welds that influence these stress levels?
     • Based on your estimates of the limiting stresses, how it was loaded, and the geometry, estimate the magnitude of the load(s) that caused failure.
     • What could be done to prevent this failure from occurring again?
        
4. Write a short (1 to 2 pages) creative story that describes a failure scenario involving all three items.  You might want to pretend to be a news reporter.  For example, you can pretend to interview someone that was listening to a polka band at the local bowling alley when a helicopter crashed into the building.  ...assuming your group was crazy enough to pick such seemingly unrelated items.  :)
   

   Sample Short Story

   1. Feel free to use the images provided here in your narrative.  Annotations can be used to refer to specific features in the images if you wish.
   2. You are also welcome to use images from web searches, news articles, etc to make the story more dramatic or believable.
   3. You might consider the following questions.  These questions, and the ones above, are provided simply to help you think through the analysis.  Since this is probably your first failure analysis, you will be graded based on your creativity, thoroughness and logic.
       
      • Was anyone hurt as a result of the failure?  Who was at fault?  Is there ongoing litigation?  
      • What is the cost of the failure?  Was it easy to repair?
      • Based on the Mechanical Failure Mode Taxonomy, which failure mode did each component experience?  Why did you select these failure modes? (Give reasons.) 
      • What do you think could be done to prevent these failures from occurring again?
      • What test(s) could be run on the failed component to assess the cause of failure...to verify your conclusions?
         
5. Optional:  Access the RED tutorial. 
    
   1. Perform a human centric, subsystem level RED analysis using the electromechanical matrix.  The functions that you need for step 4 in the RED tutorial are found above in the functional model on your component's info page.  
   2. Print a screenshot of the fever chart and functions selected on the results screen and submit this image with your write-up.  
   3. Save a risk report and open as a comma delimited spreadsheet and submit this document with your write-up.  
   4. Refer to this step-by-step procedure or the RED introduction for more information.
   5. Answer the following questions in your write-up.
      • What is the failed component's name and number?
      • Based on the Mechanical Failure Mode Taxonomy, lab activities, and RED analysis, what do you think the failure mode of your component was? 
      • Why did you select this failure mode? (Give reasons.) 
      • What do you think could be done to prevent this failure from occurring again?

    

6. Combine your results for the lab experiment and the group's failure investigation into a single document, as per your teachers' instructions, and submit at the start of the next lab class.