Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 1Winter Quarter Stress and Strain Lab 4

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 2Winter Quarter Objectives To understand how engineers compare different materials. To understand how a strain gage works. To collect and analyze experimental data.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 3Winter Quarter Stress vs. Strain Where: E = Modulus of Elasticity  = stress  = strain For the bike fork material E = 29.0 x 10 6 psi. Strain:Stress: Hooke’s law:

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 4Winter Quarter Loads applied by rider STRAIN GAGE A sensor that measures strain Measuring Load on a Bicycle Fork

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 5Winter Quarter Loads applied by rider Loads applied by the road The fork is loaded by a combination of compression shear and bending Compression Bending Shearing Loads on a Bicycle Fork

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 6Winter Quarter Transducer Conditioning Circuits Recorder Data Processing Wheatstone Bridge + Amplifier Strain Gage Data Acquisition System

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 7Winter Quarter Grid (electrical resistor) Backing Film Copper-plated Solder tabs Transducer: Strain Gage Translates strain to electrical resistance. Resistance increases with length.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 8Winter Quarter Strain Gages Resistance is Proportional to Length or Where: S g is the “gage factor” and  is the strain.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 9Winter Quarter Strain Gages

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 10Winter Quarter Conditioning Module: Wheatstone Bridge The strain gages are connected as the four resistors in the Wheatstone Bridge.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 11Winter Quarter Where: V in = 5.0 volts A = 500 (amplification) S g = (gage factor) Conditioning Module: Wheatstone Bridge

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 12Winter Quarter Lab Experience: Part 1 – Static Test Part 1 – Static Test: Collect data for bicycle with no load, with a rider sitting, and with a rider pedaling. Part 2 – Dynamic Test: Collect data while simulating the bicycle being ridden over obstacles.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 13Winter Quarter Post-lab Requirements STATIC TEST: –Plot strain vs. time and stress vs. time. Label events on graphs (ex. “Rider 1 gets on”, “Rider 1 pedals”, etc.) –Calculate average stress while pedaling for each rider; plot vs. weight of rider. –Plot raw voltage data vs. time.

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 14Winter Quarter Post-lab Requirements DYNAMIC TEST: –Plot stress vs. time. Label events on graphs. –Modify assignment A13 to find min and max stress. –Compute ratios for each rider: Max stress dynamic : max stress static Min stress dynamic : min stress static

Engineering H192 - Computer Programming Gateway Engineering Education Coalition Lab 5P. 15Winter Quarter Lab Memo Guidelines Individual memos. Follow formatting guidelines in “FEH Guide to Lab Reports and Memos.” “Lab-specific requirements” not listed on the rubric. You must determine what is appropriate to include.