Category: Engineering and Technology Degree Level: Undergraduate ...
Category: Engineering and Technology Degree Level: Undergraduate Abstract ID#1099
Hector Ramirez Lara & Joseph Mielinski Shefelbine Lab
Macroporosities and Crack Propagation The toughness of a material is the measure of how easily fractures propagate. Macroscopic holes affect crack propagation. Our research explores the relationship between the size, location and quantity of macropores and crack propagation. A three point bending test was applied to notched extruded acrylic samples in order to analyze the relationship in between porosity and crack propagation. Different configurations of sample were made to consider the location quantity and size of the porosities. Using the collected data, we have constructed graphs showing the stress vs. strain curves of the test. This in turn has allowed us to compare the changes in toughness between samples with different holes. So far our research has shown a definitive difference between the samples based on whether or not there is a hole in the sample. This difference regards the force and work needed to break the sample. We strive to further our research to manipulate crack propagation by changing the location of the macro porosities. We are also collaborating within our own lab to model our experiment and predict other possible configurations that can further deepen our understanding of crack propagation.
We compared the energy and force needed to break a notched sample as compared with a 2mm macropore. We found: • A significant increase in the energy needed to break the samples. • A second loading period in which the force decreased. • Mechanical variance due to macropore configuration
Background: •
•
• Base for fracture toughness analysis
Instances of fracture Issues Bone Wood(Boats) Mines Macroporosities (Holes) affect the mechanical properties of materials
Figure 3: Analysis of clear sample
Goal: • • • •
Understand the mechanical implications of fracture paths in the presence of macroporosities Utilize the understanding of macroprosities to manipulate fracture paths Develop a system to diminish fracture damage through macroporosities Stretch Goal: Eventually manipulate fracture paths in bone.
Figure 4: Analysis of Macropore Sample
Figure 5: Analysis of Notched Sample
Material: • The samples being used were an acrylic, extruded rod that had been machined to 60 mm. by 9 mm. by 9mm. • The notch for the notched and hole samples was machined into the middle of the sample and the 2 mm. diameter hole was drilled into the center of the notched with hole samples.
Conclusion: We have determined that the notch and hole do indeed produce a recognizable difference in the mechanical performance.
Further Research: Figure 1: Instron 3-Point Bend Test
References:
Method: • Used a Three Point Bending Test to determine material qualities. • Load rate of 0.1 mm. per second. • Compared different trials which each other to help determine how differences in the structure affected mechanical performance
In the future we hope to expand this research with: different macropore configuration, translation to different materials, and finite element analysis of the failure. Ostoja-Starzewski. M., Wang. G. (2005) Particle Modeling of Random Crack Patterns in Epoxy Plates. Probabilistic Engineering Mechanics, Volume(21), pp. 267-275 Al-Ostaz. A., Jasiuk. I. (1997) Crack initiation and propagation in materials with randomly distributed holes. Eng Fract Mech; Volume (58) pp. 395–420
Acknowledgements: Figure 2: Broken Sample
We would like to thank Dr. Sandra Shefelbine for providing constant assistance, encouragement, and financial support as well as Jon Daughty for providing machining expertise and manufacturing assistance.
Hector Ramirez Lara & Joseph Mielinski Shefelbine Lab
Macroporosities and Crack Propagation The toughness of a material is the measure of how easily fractures propagate. Macroscopic holes affect crack propagation. Our research explores the relationship between the size, location and quantity of macropores and crack propagation. A three point bending test was applied to notched extruded acrylic samples in order to analyze the relationship in between porosity and crack propagation. Different configurations of sample were made to consider the location quantity and size of the porosities. Using the collected data, we have constructed graphs showing the stress vs. strain curves of the test. This in turn has allowed us to compare the changes in toughness between samples with different holes. So far our research has shown a definitive difference between the samples based on whether or not there is a hole in the sample. This difference regards the force and work needed to break the sample. We strive to further our research to manipulate crack propagation by changing the location of the macro porosities. We are also collaborating within our own lab to model our experiment and predict other possible configurations that can further deepen our understanding of crack propagation.
We compared the energy and force needed to break a notched sample as compared with a 2mm macropore. We found: • A significant increase in the energy needed to break the samples. • A second loading period in which the force decreased. • Mechanical variance due to macropore configuration
Background: •
•
• Base for fracture toughness analysis
Instances of fracture Issues Bone Wood(Boats) Mines Macroporosities (Holes) affect the mechanical properties of materials
Figure 3: Analysis of clear sample
Goal: • • • •
Understand the mechanical implications of fracture paths in the presence of macroporosities Utilize the understanding of macroprosities to manipulate fracture paths Develop a system to diminish fracture damage through macroporosities Stretch Goal: Eventually manipulate fracture paths in bone.
Figure 4: Analysis of Macropore Sample
Figure 5: Analysis of Notched Sample
Material: • The samples being used were an acrylic, extruded rod that had been machined to 60 mm. by 9 mm. by 9mm. • The notch for the notched and hole samples was machined into the middle of the sample and the 2 mm. diameter hole was drilled into the center of the notched with hole samples.
Conclusion: We have determined that the notch and hole do indeed produce a recognizable difference in the mechanical performance.
Further Research: Figure 1: Instron 3-Point Bend Test
References:
Method: • Used a Three Point Bending Test to determine material qualities. • Load rate of 0.1 mm. per second. • Compared different trials which each other to help determine how differences in the structure affected mechanical performance
In the future we hope to expand this research with: different macropore configuration, translation to different materials, and finite element analysis of the failure. Ostoja-Starzewski. M., Wang. G. (2005) Particle Modeling of Random Crack Patterns in Epoxy Plates. Probabilistic Engineering Mechanics, Volume(21), pp. 267-275 Al-Ostaz. A., Jasiuk. I. (1997) Crack initiation and propagation in materials with randomly distributed holes. Eng Fract Mech; Volume (58) pp. 395–420
Acknowledgements: Figure 2: Broken Sample
We would like to thank Dr. Sandra Shefelbine for providing constant assistance, encouragement, and financial support as well as Jon Daughty for providing machining expertise and manufacturing assistance.
