Laboratory Experiment in Engineering Materials for Upper-Level Undergraduate and Graduate Students

摘要

Laboratory experiments are a critical part of the required curriculum for upper-level undergraduate and graduate students seeking degrees in the science, technology, engineering and mathematics (STEM) fields. These laboratory experiments usually involve materials and/or material properties that were designed to establish a level of specification and implementation methodology. However, often these laboratory experiments were developed for well defined systems in controlled environments in order to take advantage of limited resources such as expensive materials, laboratory space and testing supplies. Material systems that incorporate a dependence on more than one parameter for processing and subsequent characterization pose a significant problem in that the experiment designer may not possess the information to identify the key parameters that influence the critical properties sought after. The ultimate goal is for the student experimental designer to predict parameters and properties based on a limited number of experiments or available data. This paper focuses on the educational merits of a laboratory experiment in engineering materials, and what was learned about educating the upper-level and graduate students. The proposed methodology in this paper describes a general full factorial design for experiments involving the mechanical characterization, specifically the mechanical strength and processing parameters, of a material. This Factorial Design Analysis (FDA) approach facilitates a 'between-participants' design analysis that includes more than one independent variable, and has the advantage over a simple randomized design in that you can test the effect of more than one independent variable and the interactive effect of the various independent variables. The method is validated for the optimization of the boundary conditions that influence the material properties of electrodeposited metals. Specifically, a 2~k factorial statistical analysis is conducted, analyzed, and a mathematical model derived, to describe how the electrolytes' boundary conditions influence the mechanical strength of electrodeposited nickel-iron (Ni_(80)Fe_(20)). The critical external boundary conditions examined for this material system include the current density of the electrolytic bath, the bath temperature, and the speed of agitation in the bath. Results show the ANOVA (analysis of variance) table of results for the critical factors, as well as the F-test on the interactions. Based on the results, regression models are developed and surface plots presented for the mechanical strength of the material system as a function of the external boundary conditions.