Teaching Demo to Reinforce how Mechanical Properties Change Due to Heat Treatment Processes

Lecture coupled with some hands on demonstration is a powerful teaching strategy for engineering students. This style of teaching was incorporated into an engineering materials selection course. Students realize that changing material properties play an important role in understanding why materials are selected for different design specifications. Engineering students take courses in mechanics of material, machine design, finite element analysis and capstone senior projects. These courses require students to call out and specify the best and least expensive material according to some type of chemical, physical or mechanical loading conditions. Students should understand the way a material behaves in service depends upon its alloy composition, crystalline structure, manufacturing process and heat treat condition. This paper is written after developing a hands-on material lab that teaches engineering students how heat treatment processes affect material properties. Its main focus is with AISI 4140 alloy steel, however, other carbon and alloy steels can be used and explored by the same procedure outlined in the lab handout. The first part of the lab requires students to set up a heat treat furnace. They quench harden and temper thirteen charpy specimens. The range in hardness are from dead soft to its maximum hardness that the material can acquire. Hardness and toughness values are measured and the data are plotted to generate material behavioral curves. From the Brinell hardness number the ultimate tensile strength is estimated and plotted against hardness and toughness values. A series of design questions in the lab handout helps reinforce the theory taught in the class room to this hands-on learning process. Why this Teaching Method? Teaching materials selection can often be unimaginative and uneventful for students. They experience a lot of reading, memorization of processes and definitions in this class. A different approach developed from an ABET criteria for assessment was implemented as a hands-on lab to determine mechanical properties. The ABET assessment tool was “The Course Level Loop Assessment Action” shown in figure 1. This tool is intended to capture and document teaching and learning improvements based on informal assessment of ongoing courses. The assessment driving a particular action may be generated by student feedback, instructor generated, peer generated, etc. Problems are noted on the form and improvement actions are documented, implemented and then assessed. This closed loop assessment tool shown in figure 1 was implemented for this material selection course and prompted two actions for this paper. The first was to engage students in the learning process of mechanical properties by having them set up and break a bunch of charpy specimens of different heat treatments. Second, students lack completeness in generating graphs of lab data. This paper puts a strong emphasis on improving such graphing skills by having the students construct a series of material behavior graphs from the data and other equations implemented in the lab write up. P ge 2.11.2 ABET Course Level Loop Assessment Action 2009 Course: MET 3150 Materials Selection and Heat Treatment Faculty Responsible for Survey and Action Items: Prof. Magda Faculty Responsible for Proposed Future Action: Prof. Magda Faculty Responsible for Implemented Action: Prof. Magda