Bucknell University Senior Design - Metal Adhesives Project
My senior design project was sponsored by Peter Rebar, a Bucknell alumni who owns a small engineering consulting company in Ohio, and was having issues with the reliability of brazing in his products. Brazing requires a significant amount of labor, skill, time, and money, and we were tasked with investigating metal adhesives as an alternative to brazing. We found that metal adhesives were more consistent than the provided brazed samples and a viable alternative for parts that would be used under static loads; however, the adhesives were very weak when subjected to impact loads in comparison to the brazed samples.
The Gap? A Bucknell alumni who owns an engineering consulting firm was having a lot of issues with brazing in his manufacturing processes. The brazed bonds were very inconsistent depending on who was producing them, and often failed, leading to wasted time and resources.
The Solution? We designed and manufactured fixtures for Bucknell's stress testing equipment, in addition to a series of samples, which we adhered and tested using 3 different metal adhesives. |
Fixture & Sample Design
Static Stress TestASTM 4562 was chosen for the static shear test. Pin and collar samples were adhered. The fixture (shown in transparent view) held the sample in place, supporting the collar while the assembly was mechanically loaded. The applied load caused the adhesive to fracture within the pin and collar interface due to shear stress.
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Impact Stress TestASTM 950 was selected for the impact test. Rectangular samples were adhered in a single lap joint. The fixtures held the samples in place, aligning the top sample with the striker of the swinging pendulum arm of the Tinius 92T. The impact of the pendulum arm caused the adhesive bonds within the sample interface to fracture in shear.
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Testing Procedures
Results
Recommendation/Impact
Metal adhesives exhibited more consistent results, in addition to reducing the required time, skills, and other resources, as compared to brazing. The accuracy and precision of the adhesives was much stronger than that of their brazed counterparts, but the adhesives lacked the ability to resist high impact loads. The adhesives were more easily manufactured, yielding approximately 37 viable samples per adhesive compared to 7 viable brazed samples. Our team recommended that Peter use Torque 20RC in applications would not be subjected to impact or loads exceeding 3000 psi rather than brazing; in cases where the bonds would be subjected to impact loads, brazing would be the better option, despite the poor manufacturability.