BYOE: A low-cost material testing machine to increase engagement in a materials science lab course

Abstract

As a field, engineering is a profession with rich and deep theoretical foundations in each of its numerous subject areas. Helping students understand these foundational theoretical concepts can sometimes be difficult, and it is not uncommon for students to "get lost" in the details and fail to understand the main concepts. One way to help overcome this problem is to use laboratory classes. Laboratory classes provide students with hands-on learning experiences that help them connect theory and practice. One way students do this is by running experiments, collecting data, analyzing it, and comparing the results to those predicted by theoretical models. This discovery process can help build students' confidence in existing theories and help them understand these theories at a much deeper level. Although this sounds great, the reality for students in many engineering programs is different. Laboratory equipment is expensive, and even in relatively small laboratory classes (such as one with a dozen students), equipment can be overbooked. Although one or two students may get to run the equipment themselves, the rest may not get those experiences and don't benefit in the same way as the students who did. This is the exact situation the author faced with a materials science lab course. The bottleneck in this case was the tensile testing machine, and feedback from students about the class included the fact that much of their lab time was spent "sitting around" while they waited to be able to use the (one and only) tensile testing machine. To address this problem, we developed a small low-cost tensile testing machine so that students could eventually work concurrently in groups of 2 or 3, each with their own tensile testing machine. The current tensile testing machine prototype has a crosshead with 18in of vertical travel and replaceable load cells of 5kg(11lb) to 500kg (1100lb). This prototype uses a dual leadscrew with a hand crank, an optical encoder to measure distance, a load cell to measure force, and a small 7" monitor to display the results in real time to the user. An Arduino board is used for data acquisition from the encoder and load cell, and this is connected to a Raspberry Pi computer, which is in turn connected to the monitor. A wireless keyboard with an integrated track pad was used to interface with the machine, whose output is shown on the small 7" monitor.