Engineering Design in a Materials Processing Laboratory Course through a Guided Case Study

Materials selection and evaluation is an integral aspect of the Engineering Design Process and an essential skill for the practicing engineer. Materials and their associated processing and forming methods serve to both enable and limit product design and performance. The current work presents the use of guided case studies as an approach to achieve a designcentric laboratory experience. The developed case study employed in the current investigation is the selection of sustainable materials for single use beverage containers. The learning outcomes of this approach were evaluated by surveys administered to two different groups of students: one group participating in the case study (intervention) and other participating in the pre-existing materials processing laboratory investigations (control) at two matched time points during the same semester. The initial self-assessment was administered before the three week case study intervention and the second survey was administered after the conclusion of the three week case study. Statistical analyses of survey results reveal significant difference between the two groups, in that students in the case study (intervention) group reported significant new learning in their ability to “design a materials specification” between the initial and final time points. Introduction: Largely driven by calls from industry, the pedagogical approach in engineering education has seen a broad shift towards a design-led paradigm, whereby fundamental disciplinary knowledge is conveyed in a manner incorporating the broader knowledge and skills needed by a practicing professional engineer. While a range of different engineering design education frameworks exist, the shared objective of these approaches is to provide graduating engineers not just the fundamental scientific/engineering knowledge required but also the complex problem solving, social awareness, and interpersonal skills required to function as practicing engineers [1]. It is the goal of the current work to develop and assess hands-on, laboratory based, course content which teaches materials selection for engineering design. In the context of engineering design, material selection is not merely the selection of an existing material from which to fabricate a finalized engineering component or design. Rather, materials selection should be treated as an integral component of the iterative design process in which the material, process, and design are refined and optimized in parallel to address a market need, see Figure 1 [2], [3]. In this context, the specific educational objectives for the course are that students should be able to: 1) quantify and differentiate, with order of magnitude precision, typical ranges of physical properties (density, hardness, elastic modulus, and tensile strength) of the three primary classes of engineering materials (metals, ceramics, and polymers), 2) carry out standardized materials testing procedures required to characterize and compare the properties of engineering materials, 3) describe and predict the role of several common processing methods (such as cold work and heat treating) on the structure and properties of example engineering materials, 4) recall the important materials selection considerations in the concept, embodiment, and detail stage of engineering design, 5) evaluate the suitability of an engineering material and processing method for a model application given specific design parameters and testing methodologies, 6) propose a materials enabled component or solution to a stated engineering design challenge and suggest suitable candidate materials, 7) design and implement a materials qualification specification suitable to evaluate a specific material for the proposed application. Figure 1. Both material and process selection run in parallel and support the overall engineering design process (After Ashby 2014) [3]. Instructional Approach: The design-first approach has been widely adopted in introductory level materials science lecture courses [3], [4]. Yet, there remain significant challenges to and relatively few examples of the successful integration of Engineering Design into a hands-on materials processing laboratory course, particularly at the introductory level [2]. Notable limitations include the size, cost, and training required to obtain and operate state-of-art materials characterization and processing equipment. In addition, there is tremendous diversity in off-theshelf materials, processing methods, and characterization techniques which themselves are often codependent (i.e., material choice impacts process choice, both of which may limit or impact choice of suitable characterization methods). Consequently, the depth and freedom allowed in any formal hands-on materials selection design challenge is significantly limiting. However, carefully selected hands-on case studies may provide the opportunity to engage students in materials and process selection at each stage of the design process. The use of guided case studies, rather than open ended design challenges (common in upper class and senior design projects), provides students with the opportunity to be active participants in the materials selection and design process as a limited subset of materials and processing methods can be made available for hands-on investigation. A suitable case study should be chosen for its significance and relevance in modern society. Further, the product should be familiar, allowing students to draw on their own experiences, interests, and background knowledge to inform and scaffold the design process. Finally, if possible, the case study should also allow for multiple approaches and potential solutions to the same design problem, such that successive course offerings are not diminished by the availability of “example” solutions from prior years. Example Case Study: The case study employed in the current work focuses on the selection of materials for single use beverage containers. This case study was chosen based on both the familiarity of the application and the significant societal impact of single use beverage containers, from a sustainability or life cycle perspective. In addition, the variety of beverage products and container types available in the marketplace suggests the potential for multiple viable solutions based on product requirements and market demand. Table I. Weekly activities for Single Use Beverage Container Case Study. Pre-lab activity / Discussion Hands-on Lab Activities Follow Up / Broader Impact Week 1: Concept 1) Reading: Beverage container market survey. 2) Activity: Translating Design requirements. 3) Screening: Typical ranges of mechanical properties. 1) Translating requirements for beverage containers. 2) Mechanical testing of beverage container materials (glass, polymer, and metal). 1) Lab report: Failure analysis and mechanical limitations of different materials classes. 2) Broader Impacts: Weight limited design, brittle failure. Week 2: Embodiment 1) Prelab discussion: Materials forming methods. 2) Prelab discussion: process energy 1) Heat capacity measurements of beverage container materials. 2) Plastic Forming: by vacuum molding 1) Lab Report: Relationship between heat capacity and process energy. 2) Lab Report: Limitation of forming methods. 3) Broad Impact: Economic analysis of production volume and forming methods. Week 3: Detail 1) Prelab discussion: Sustainability in Engineering Design. 2) Life cycle Analysis 1) Eco-audit of alternative materials for an actual beverage container. 1) Broader Impact: Alternative design solutions; Eco-audit: Comparison of canned soda and a soda stream The case study takes place over the course of three weeks. Each week the case study focuses on one of the successive stages of materials and process selection for engineering design, following Figure 1 above. The first week focuses on conceptualization and translating design needs, including comparing mechanical properties of various material classifications. The second week focuses on the embodiment including processing energies and forming methods. The final week includes a detailed eco-audit in order to compare and inform sustainability issues associated with selection of various material options. Each weekly module includes a prelab activity or discussion introducing that week’s activity, a hands-on experimental component, and follow up analysis and impact assessment in the form of a written lab report. Specific activities for each week are summarized in Table I. Assessment Methods and Statistical Analyses: The materials processing laboratory is a core course in the Stevens Institute of Technology “Design Spine” curriculum, with 276 students enrolled in 23 different sections (~12 students per section) during the Fall 2015 semester. In order to pilot and assess the new case study content, a single section was selected to undergo the pilot intervention. All other sections followed the standard pre-existing practice of weekly closed ended laboratory experiences in materials science. Typical closed ended laboratories include both “traditional” experiments such as heat treating a steel alloy by quenching and measuring changes in hardness, and “trending” topics like assembling a dye-sensitized solar cell and measuring its’ power output. In the pilot (hereafter “intervention”) section, the final three closed ended laboratory experiences were replaced with the case study content and activities summarized above (Table I). The pilot and control sections were chosen at random from the available sections. The learning outcomes of this case study intervention approach were evaluated by anonymous subjective surveys administered to students participating in the case study investigation at two time points: once before and once after the conclusion of the three week case study. In addition, a control group participating in a traditional materials processing laboratory format class was evalu