University of Pennsylvania Department of Bioengineering

Aims/Objective & Hypothesis(es):

MATERIAL TESTING: ROCKWELL HARDNESS & IMPACT ENERGY

Group 101B5

Objective: To determine correlations, if any, between impact energy, Rockwell hardness, and density for different types of wood.

Hypotheses: • There will be a significant statistical difference for impact energies, hardness, and density between dowel rods of different wood.

• There will be a positive correlation between density and hardness for dowel rods of different wood.

• There will be a negative correlation between impact energies and Rockwell hardness values for dowel rods of different wood

University of Pennsylvania Department of Bioengineering

Methods, Protocol & Equipment:• Prepare each 36” dowel rod into 5-6 samples.

• Measure the mass and geometric properties of the dowel rods.

• Perform impact tests on up to six types of wood dowel rods – pine, birch, cherry, oak, walnut, balsa – using the impact pendulum.

• Practice using manual Rockwell hardness tester on surrogate Popsicle sticks.

• Perform Rockwell B hardness test for all samples used in the failure tests using the manual Rockwell hardness tester.

• Perform ANOVA on impact, hardness, and density data for up to six types of tested wood dowel rods.

• Analyze the data by graphing impact energy versus hardness and hardness versus density for all trials and finding the best fit line.

• Perform Regression Analyses to see if the correlations between impact energy-hardness and hardness-density are significant.

University of Pennsylvania Department of Bioengineering

Proposed Results/Findings/Deliverables:

Potential Pitfalls:

• We expect to find balsa wood to have the lowest density, smallest hardness value, and largest impact energy and birch to have the highest density, largest hardness value, and lowest impact energy of the materials tested.

• An ANOVA and subsequent t-tests (αBon = 0.01) will show significant differences between balsa and birch and possibly others for density, hardness values, and impact energy.

• Regression Analyses on impact energy versus hardness and hardness versus density will give Fsig<0.05.

• Rockwell hardness standard compatibility to materials used.

• Variability in impact energy for a given type of wooden dowel rod (i.e. due to grain orientation differences).

• Not enough variability in hardness or impact energy across groups.

University of Pennsylvania Department of Bioengineering

Materials and Budget & Justification:100 Popsicle Sticks …………………………….. $8.75900 Linear inches of ¼” Balsa Dowels…….....$67.25900 Linear inches of ¼” Birch Dowels………...$6.85900 Linear inches ¼” Oak Dowels…………....$12.78900 Linear inches ¼” Pine Dowels……….......$18.13900 Linear inches ¼” Walnut Dowels………...$43.89900 Linear inches ¼” Cherry Dowels………...$37.59Craftsman 6” Coping Saw…………………..…..$8.55Precise Hardness Tester with Auto Weight Selection………………………………$778.68

Subtotal …………………………………..……$982.47Giandomenico Donation..…………..…...….$1018.53

Total…………………………………………...$2000.00

*All Prices Include Shipping to Penn