Publications

Submitted
Q. Bao, D. Faas, and M. C. Yang., “Benefits and Limitations of Sketching & Prototyping in Early Stage Design.The Fourth International Conference on Design Creativity (4th ICDC), 2016. Submitted.Abstract

Previous research suggests that, for the design of simple mechanisms, sketching and prototyping are somewhat interchangeable in terms of their influence on design idea quantity and quality. This study explores whether this interchangeability holds true as well for a product design activity. Three experimental conditions are compared: sketching only, prototyping only, and both prototyping & sketching. A design evaluation metric, idea distance, is proposed to evaluate the breadth of design space exploration. Results showed that individuals who sketched early on generated more ideas and had more creative final designs, while individuals prototyped early on had designs that performed better functionally. Greater idea distance was found to correlate with more creative ideas. However, exploring too broad a design space reduced the depth of design idea exploration, and was negatively linked to the functional performance of the final design.

Keywords: Sketching, Prototyping, Idea Generation, Creativity

2016
G. Hein, et al., “The Changing Role of Professional Societies for Academics.Proceedings of ASEE Annual Conference, New Orleans, LA. vol. (ASEE2016-375625). 2016.Abstract

This research paper describes how professional societies provide services to their members with a focus on the Society of Women Engineers (SWE).  Professional societies fulfill many roles for their members. For underrepresented groups, the different roles become more important. Despite increasing numbers of women and other underrepresented groups in engineering academia, retention rates of women are still below the national average. Professional societies such as the Society of Women Engineers (SWE) may close the retention gap through community building. Not only do professional societies provide opportunities for networking and career building, but they also provide affirmation that there are others in similar roles. Although there are financial and time constraints to becoming active within a professional society not affiliated with one’s technical area, when academics feel that their involvement is valuable to their career development they will invest necessary time and money into the professional society. Similarities exist between how professional societies retain/attract faculty from underrepresented groups and how universities accomplish the same goal.

This research paper focuses on how one professional organization, SWE, is providing opportunities to women in academia that include professional development, recognition/awards, networking, leadership development, and career advancement. In the past, SWE has been viewed as a non-technical professional society. However, SWE is uniquely positioned to provide a community that transcends the organizational boundaries by encompassing technical, service, and professional development areas for women in academia that is inclusive, collaborative, and supportive as well as connected to industry, government and academia on multiple levels.

C. Lombardo, D. Faas, and A. Uttamchandani., “Improving Design Competency in Introductory Engineering Courses within a General Education Requirement.Proceedings of ASEE Annual Conference, New Orleans, LA. , vol. ASEE2016-15839. 2016.Abstract

This study discusses design competencies in several introductory engineering courses at the Harvard School of Engineering and Applied Sciences within the general education program as well as required introductory courses for electrical and mechanical engineering majors. Each of these courses has a final team project, with varying degrees of open-endedness, in lieu of a traditional exam.  Design competencies were measured in these courses, both pre- and post-experience, using self-reported surveys as well as instructor assessment of ABET learning outcomes.  The post-experience surveys as well as final project rubrics were used to measure changes in design competencies as well as changes in self-efficacy. There was a correlation between the changes of self-efficacy and ABET outcomes at the end of the courses for both major-specific and general education courses.  Students in the general education course scored lower in final self-efficacy compared to their peers in the major-specific courses but there may be a trade-off between making engineering material more accessible to general education requirements as compared to the depth covered in major-specific courses.  This paper shows that encouraging and motivating students to study engineering does not necessarily have to be distinct from teaching them technical design or engineering skills.  Learning outcomes in hands-on design courses are a critical component to student engagement and retention within engineering and the liberal arts.  All of the courses discussed within this paper play important but different roles within the engineering curriculum at Harvard.

D. Faas and S. Gong., “Improving Novelty and Quality during introductory mechanical design competitions.Proceedings of ASME 2016 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC16-59251). 2016.Abstract

This study explores whether changing design objectives during introductory mechanical engineering courses would improve design novelty and quality when these courses offer a competition element. Design fixation can occur when students are presented with the same design objective because the institutionalized “best” solutions are transferred from semester to semester and student to student.  Design competitions are a popular way to teach the design and construction components, often with a focus on robotics. Some competitions are newly designed and rebuilt every single semester, requiring advanced planning and often high budgets. Others reuse a similar competition from year to year without any changes to the design objectives. This paper tries to answer whether or not students are building more novel designs when the competition changes from semester to semester. In this study, robots from four different configurations for a design-and-build activity were analyzed. The unchanged design prompt and 3 semesters of different design prompts were included in the study.  The evaluations of the robots were based on the performance of the robots, the type and quality of the designs, and the relationship between the design competition and the robots.  Results from this study suggest that changing design objectives (i.e. challenges found in a robotic competition) allows for a wider variation in the designs.  While the average novelty did not change, students were no longer limited to and fixated on a very small range of designs.  

 

Keywords: Engineering Education, Mechanical Design, Design Competition, Novelty

2015
D. Faas and R. D. Howe, “Best Practices for Introductory Mechanical Design Competitions,” Proceedings of ASME 2015 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, Boston MA. 2015.Abstract

Freshman/sophomore design projects provide students with hands-on experiences in conceptual design and manufacturing.  For some of these courses, a design competition is used to teach the design and construction components. These competitions are often reused from semester to semester, so the students typically suffer from design fixation. When design competition tables are erected new every single semester, it requires advanced planning and high budgets. This paper discusses a case study of a different structure for introductory design courses and competitions at Harvard. We summarize a yearlong effort to improve an existing early design competition with more machine component elements and linkage design.  The goal of a interchangeable design competition was to prevent design fixation while at the same time providing boundaries for students to successfully implement their robot designs, independent of their previous mechanical engineering exposure.  

 

Keywords: Engineering Education, Mechanical Design, Design Competition, Best Practices.

C. Lombardo, D. Faas, A. Utt, and E. Hu, “Self-Directed Summer Design Experience Across Disciplines and the Globe.Proceedings of ASEE Annual Conference, Seattle WA. ASEE-5823. , 2015.Abstract

During the summer of 2014, the Harvard School of Engineering and Applied Sciences and the Hong Kong University of Science and Technology initiated a multidisciplinary international design experience for the benefit of the student populations of both institutions. The goal of this program was to create an international multidisciplinary team-based research and design project that included exposure to the academic and industrial environments in both Hong Kong as well as the United States (specifically the Boston area). The Harvard-HKUST International Summer Design Experience occurred completely outside of any classroom setting during nine weeks and was co-located in Boston and Hong Kong for four weeks each. The reason to hold this program in both Hong Kong and Cambridge, MA was to give the students a chance to work within and experience both campuses, culturally and geographically. The pedagogical approach was unique, as there was no embedded curriculum and students were able to freely pursue a project in a given topic area that they were interested in. The major topic for this summer was Visible Light Communication systems. In this paper we present the general pedagogical approach to this experience and provide some insights and examples of the effect the program had on students.

2014
D. Faas, Q. Bao, and M. C. Yang, “Preliminary Sketching and Prototyping: Comparisons in Exploratory Design-and-Build Activities.Proceedings of ASME 2014 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, Buffalo NY. 2014.Abstract

This study explores the role of sketching when designers are creating fast, preliminary prototypes during hands on design-and-build activities. Many studies have noted the value of both sketching and the building of preliminary prototypes in the early stages of the design process. In a typical design scenario, exploratory sketches are made before prototypes are fabricated. However, in certain cases, the differences in the design exploration value of a sketch and a simple, preliminary prototype may not always be clear. In this study, three conditions for a design-and-built activity were compared: a control group (allowed to freely sketch throughout), a limited sketch group (only allowed to sketch at the beginning) and a no sketch group. The study was conducted twice, using different prototyping materials each time. One focused on assembly only (an Erector set) and one that requires both part fabrication and assembly (foam core). The performance of the prototypes, the type and quality of the sketches, and the relationship between sketches and prototypes were evaluated.  Results for this study suggest that fast, preliminary prototypes are equally as useful for design exploration as sketching in building simple mechanisms, though results would likely be different for more complex design tasks.

2013
D. Faas, Q. Bao, M. C. Yang, and D. D. Frey, “The Influence of Immersion and Presence in Early Stage Engineering Designing and Building.Artificial Intelligence for Engineering Design, Analysis and Manufacturing (AIE-2013-021), , 2013.Abstract

This paper explores the role of a designer’s sense of engagement in early stage design. In the field of virtual reality, presence and immersion are standard measures of an individual’s sense of engagement and involvement in an activity. High levels of presence might indicate that the designer is highly focused on the work. The central research question is: Do designers who are more engaged in design activity, as measured by presence and immersive tendency questionnaires, produce better designs? An experiment was conducted to assess presence and immersive tendencies within the context of a hands-on, open-ended design-and-build activity. Results indicate that designers' sense of immersion and presence ranged widely as well as their sense of frustration and calmness while performing the design activity. It was found that higher levels of presence correlated with either high design performance or, surprisingly, low design performance. Lower levels of presence correlated with average design performance. No correlations were found between immersive tendency and design performance. This study suggests that some level of presence can be linked with better design, and implies that level of presence might serve as an indicator of performance and learning in similar design-and-build activities.

D. Faas and D. D. Frey, “Quickly Building Students’ Confidence in their Fabrication Abilities,” Proceedings of ASEE Annual Conference, Portland OR. vol. ASEE-5823. 2013.Abstract

Undergraduate mechanical engineering education usually places a high priority on design experience.  Such courses serve to enhance student interest in engineering, improve retention, and improve results in later courses.  A challenge to implementing early design experiences in engineering programs is the readiness of the student population for hands-on design work.  One of the main obstacles the students face is the lack of fabrication experience. This typically leads students to begin work too late.  This has been referred to as “time scallop”- as deadlines are approached, effort levels rise rapidly and fall back to low levels repeatedly. A problem motivating this paper is that students seemed hesitant to use machine tools despite previous introductory training including mills, lathes, saws, sheet metal cutting and bending.  In this course, each student is expected to conceive, design, build, and operate a robot to carry out a specified set of tasks. This paper describes an activity that allows students to quickly build and test a robot within a 3-hour time frame. This robot, called “Mini-Me” serves most students as a starting point to build a more complex machine later on.  Surveys indicate the activity builds students’ confidence in their fabrication skills and that the gains are largest for female students. This work shows the benefit of giving students smaller subtasks to reduce anxiety about not having adequate skills to design and build a robot.  This activity has enabled students to extract key concepts and the students felt more confident that they could complete a more complex robot. Overall, student’s self-reported knowledge of servos, motors and using manufacturing equipment increased based on survey results.  The activity described in this paper has had a large impact on overall manufacturing confidence and course outcome for students.

 

2012
D. Faas, D. D. Frey, and M. C. Yang, “Analysis of Immersion and Presence and its Role in Early Stage Engineering Design,” Design Computing and Cognition DCC’12. 2012.Abstract

An experiment was conducted to assess presence and immersive tendencies within the context of a design activity.  The central research question is if designers who are more immersed or present during an activity also produce better designs. Participants were asked to complete standard presence and immersive tendency questionnaires after being presented with a design activity. Participants were instructed to build a vertical displacement mechanism for Ping-Pong ball. The design outcome indicator was maximum vertical displacement (height) of the plastic ball. The average height measured was 21.43  ± 5.46 in. A correlation between presence and design outcome was found to be statistically significant (p=0.014), but the experiment did not reveal a correlation between immersive tendencies and design outcome. Results indicate that designers' sense of immersion and presence ranged widely. There were 3 types of mechanisms built during the design activity: catapult, fulcrum and pulley. On average, each participant explored 3 different ideas during the design activity. This study suggests that there is a level of presence, which is necessary but not a sufficient condition for performance. Understanding the roles of immersion and presence might lead to a better understanding of cognitive activities during design activities.

C. Buffinton, D. Faas, and D. Sedmera, “Stress and Strain in Load-dependent Remodeling of the Embryonic Left Ventricle Assessed by Finite Element,” Biomechanics and Modeling in Mechanobiology, 2012.Abstract

Altered pressure in the developing left ventricle (LV) results in altered morphology and tissue material properties. Mechanical stress and strain may play a role in the regulating process. This study showed that confocal microscopy, three-dimensional reconstruction, and finite element analysis can provide a detailed model of stress and strain in the trabeculated embryonic heart. The method was used to test the hypothesis that end-diastolic strains are normalized after altered loading of the LVduring the stages of trabecular compaction and chamber formation. Stage-29 chick LVs subjected to pressure overload and underload at stage 21 were reconstructed with full trabecular morphology from confocal images and analyzed with finite element techniques. Measured material properties and intraventricular pressures were specified in the models. The results show volume-weighted end-diastolic von Mises stress and strain averaging 50–82% higher in the trabecular tissue than in the compact wall. The volume-weighted-average stresses for the entire LV were 115, 64, and 147Pa in control, underloaded, and overloaded models, while strains were 11, 7, and 4%; thus, neither was normalized in a volume-weighted sense. Localized epicardial strains atmid-longitudinal levelwere similar among the three groups and to strains measured from high-resolution ultrasound images. Sensitivity analysis showed changes in material properties are more significant than changes in geometry in the overloaded strain adaptation, although resulting stress was similar in both types of adaptation. These results emphasize the importance of appropriate metrics and the role of trabecular tissue in evaluating the evolution of stress and strain in relation to pressure-induced adaptation.

2011
D. Faas and J. M. Vance, “BREP Identification during Voxel-Based Collision Detection for Haptic Manual Assembly,” Proceedings of ASME 2011 World Conference on Innovative Virtual Reality 2011. , vol. WINVR2011-5524. 2011.Abstract

This paper presents a novel method to tie geometric boundary representation (BREP) to voxel-based collision detection for use in haptic manual assembly simulation. Virtual Reality, in particular haptics, has been applied with promising results to improve preliminary product design, assembly prototyping and maintenance operations. However, current methodologies do not provide support for low clearance assembly tasks, reducing the applicability of haptics to a small subset of potential situations. This paper discusses a new approach, which combines highly accurate CAD geometry (boundary representation) with voxel models to support a hybrid method involving both geometric constraint enforcement and voxel-based collision detection to provide stable haptic force feedback. With the methods presented here, BREP data can be accessed during voxel-based collision detection. This information can be used for constraint recognition and lead to constraint-guidance during the assembly process.

D. Faas, “A Hybrid Method for Haptic Feedback to Support Manual Virtual Product Assembly,” Proceedings of ASME 2011 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference. DETC2011-47665. 2011.Abstract

Experience with current Virtual Reality (VR) systems that simulate low clearance assembly operations with haptic feedback indicate that such systems are highly desirable tools in the evaluation of preliminary designs, as well as virtual training and maintenance processes. The purpose of this research is to develop methods to support manual low clearance assembly using haptic (force) feedback in a virtual environment. The results of this research will be used in an engineering framework for assembly simulation, training, and maintenance. The proposed method combines voxel-based collision detection and boundary representation to support both force feedback and constraint recognition. The key to this approach is developing the data structure and logic needed to seamlessly move between the two representations while supporting smooth haptic feedback. Collision forces and constraint-guided forces are blended to provide support for low clearance haptic assembly. This paper describes the development of the method.   

2010
D. Faas and J. M. Vance, “Assessment of PointShell Shrinking and Feature Size on Virtual Manual Assembly,” Proceedings of ASME 2010 World Conference on Innovative Virtual Reality, Ames, IA. , vol. WINVR2010-3765. 2010.Abstract

This paper investigates the effect of pointshell shrinking and feature size on manual assembly operations in a virtual environment with haptic force feedback.  Specific emphasis is on exploring methods to improve voxel-based modeling to support manual assembly of low clearance parts.  CAD parts were created, voxelized and tested for assembly.  The results showed that pointshell shrinking allows the engineer to assemble parts with a lower clearance than without pointshell shrinking.  Further results showed that assemble-ability is dependent on feature size, particularly part diameter and clearance. In a pin and hole assembly, as the pin diameter increases, for a given percent clearance, assembling low clearance features becomes difficult. An empirical equation is developed to guide the designer in selecting an appropriate voxel size based on feature size. These results advance the effort to improve manual assembly operations via haptic feedback in the virtual environment.

2009
E. Marsh, D. Faas, D. Niedergeses, and K. Whitney, “A Preliminary Incongruent Movement Study in an Immersive Virtual Reality Setting,” Proceedings of Emerging Technologies Conference 2009, Ames, IA. ETC2009-0030. . 2009.Abstract

The study of human‐computer interaction requires an understanding of how humans handle sensory information. This paper presents the results of a preliminary research project that challenged users to process sensory data that violated normal expectations by using a Virtual Reality environment to horizontally invert the results of a participant’s actions. By observing learning processes and measuring rates of improvement, the researchers found that users employ a variety of strategies to compensate for the change in visual stimuli. These preliminary results suggest that over time users can become as proficient with altered visual stimuli as with normal stimuli.

2008
D. Faas and J. M. Vance, “Interactive Deformation through Mesh-free Stress analysis in Virtual Reality,” Proceedings of ASME 2008 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, New York, NY. 2008.Abstract

Virtual reality (VR) techniques are used to create an environment that allows an engineer to modify the shape of a part and see the changes in the stress state immediately. A virtual reality application, Interactive Virtual Design Application (IVDA), that allows fast mesh-free analysis of multiple element types, including two-dimensional (2D) elements, is described in detail. Taylor series approximations and Pre-conditioned Conjugate Gradient (PCG) methods are used with mesh-free analysis to perform quick reanalysis during interactive shape modification. Prior to this work, only 3D elements were incorporated into the method. The addition of 2D elements greatly expands the potential application of this work. Several software packages including VR Juggler, OpenHaptics, OPCODE, Tahoe and OpenGL/GLM/GLUT libraries are combined in the resulting application to handle a variety of elements. This approach also supports concurrent product design and assembly methods prototyping. The addition of 2D analysis capability is discussed in this paper. The method is described and a sample problem presented.

2007
D. Faas, C. Buffinton, and D. Sedmera, “3D Reconstruction and Nonlinear Finite Element Analysis of the Embryonic Left Ventricle,” Proceedings of the ASME 2007 Summer Bioengineering Conference, Keystone Resort & Conference Center, Keystone, Colorado, USA. 2007.Abstract

Changes in mechanical loading in the developing heart produce changes in morphology, mechanical material properties, and proliferative patterns [1-3]. Understanding the relationship of these changes to mechanical stress and strain requires a geometrically accurate model of the entire ventricle including the trabecular pattern and material property, boundary condition, and loading specification. A 3D reconstruction and finite element technique were developed to reconstruct the heart from serial confocal sections and then calculate stress and strain distributions over the entire volume for the passive state. A sensitivity study to variations in pressure loading and material properties was also performed. Control hearts and two treatments, pressure overload and pressure underload, were modeled. The results show that stresses in the trabeculae are much larger than those in the ventricular walls. Strains in the pressure-overloaded hearts were significantly smaller than control or underloaded, so a negative feedback system in strain level is not indicated.

D. Faas, A. Fischer, and J. M. Vance, “Interactive Mesh-Free Stress Analysis for Mechanical Design Assembly with Haptics.Proceedings of ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, Las Vegas, NV. DETC2007-34660. . 2007.Abstract

This paper describes a virtual reality application that performs fast stress reanalysis coupled with virtual reality and haptics that allows rapid evaluation of multiple designs throughout the product design process.  The Interactive Virtual Design Application (IVDA) allows the engineer to interactively explore new design geometry while simultaneously examining the finite element analysis results.  In the presence of other parts in the assembly, the new shape can be analyzed and modified, taking into consideration mating part fits.  This approach supports concurrent product design and assembly methods prototyping. A “two-step” approach utilizing Taylor series approximations and Pre-conditioned Conjugate Gradient methods is used to perform quick reanalysis during interactive shape modification.  The virtual environment provides an immersive three-dimensional workspace. Haptics are used to provide feedback of the stress gradient as the part geometry is changed, thus facilitating the designer’s understanding of the impact of shape change on product performance.

 

2006
C. Buffinton, D. Faas, and D. Sedmera, “3D Reconstruction and Finite Element Stress/Strain Analysis of the 6-d Chick Heart,” Weinstein Cardiovascular Development Conference, St. Pete Beach, FL. . 2006.Abstract

The morphology and material properties of the embryonic heart change in response to mechanical loading. Understanding the control system operative in this response requires modeling the entire ventricle to determine the distribution of mechanical stress and strain. A 3D reconstruction and finite element technique was developed to calculate this stress/strain distribution. Optical sections in 3mm steps in a dorsoventral direction were produced from confocal imaging of 6-d whole-mount chick hearts. Z-stacks contained 500-600 sections; two to four stacks of 512x512 x-y pixels covered the left and right ventricles. AMIRA software imported the image stacks which were then merged in x-y and downsampled to 6-mm cubic voxels. Tracing with interactive pen display segmented the left ventricle (LV) and interventricular septum from the atria, right ventricle, and valves, which were removed from the image. Thresholding techniques segmented the gray-scale image into myocardial tissue and background. Finally, the surface was triangulated into approximately 100K surface elements. The surface meshes were imported into Hypermesh to create a volumetric tetrahedral mesh of approximately 300K elements. Boundary conditions of fixation at the superior surface and internal pressure of ~500 Pa were applied. The tissue was represented by a Mooney-Rivlin hyperelastic rubber model, u=0.475 and stress-strain properties from uniaxial tensile tests of LV strips. The k-file from Hypermesh was imported into LSDYNA for a nonlinear explicit finite element solution. The results show that, in passive diastolic loading, the stresses and strains in the trabeculae are large while those in the exterior LV wall are relatively much less. Thinner areas of the septum also have larger stresses and strains. Most of the trabeculae are in tension, but the compact wall shows both tension and compression. Thus the trabeculae may play an important role in sensing and actuating the myocardial response to mechanical load. Supported by NIHNIBIB EB002077.