bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on Curved Layer Fused Deposition Modeling (CLFDM) With Variable Extruded Filament (VEF)
Authors: Zhao Donghua , Guo Weizhong
Published: November 2018

Fused Deposition Modeling (FDM), an Additive Manufacturing (AM) technique, is widely used due to its low-cost and open source. Geometry accuracy and strength performance of the printed parts are closely related to inter-layer bonding between adjacent layers and inter-road bonding in the layer. Because of the limit of layer-based AM, the longitudinal tensile strength of the filaments is much higher than the bonding strength between adjacent filaments, which brings anisotropy of the printed part. While CLFDM is devoted to solve this problem and obtain better geometry accuracy and meanwhile decrease build time by virtue of high continuity of filament, reduced stair-step effect, and lesser number of layers, especially when manufacturing thin and curved parts (shells). However, to the best of our knowledge in the aspects of process modeling of CLFDM, available researches focus mainly on simple curved layer, instead of more intricate ones possessing tiny features, which are more common in manufacturing. Therefore, to realize Solid Freeform Fabrication (SFF), this paper researches CLFDM with VEF (simultaneously changing the direction and the dimension of extruded filament according to manufacturing demand of the curved layer), which would be a fundamental study and a foundation for Advanced Design for Additive Manufacturing (ADFAM), slicing and path planning (extruder path generation) in 3D space. To realize slicing and printing with homogeneous and inhomogeneous extruded filament between consecutive layers and within the layer (flat or curved), models of flat layer FDM and CLFDM with VEF are respectively established. Then, the relationships among key process parameters are analyzed. Finally, graphical simulation of the proposed strategy based on a vase is provided to verify its effectiveness and advantages from a theoretical point of view. In general, variable direction of extruded filament along tangential directions of part surface imparts smoother surfaces, instead of rough exterior appearance resulting from stair-step effects. And variable dimension of extruded filament maximizes material extruded to increase build speed wherever allowed and minimizes deposition size for resolution whenever needed, resulting in curved layer surfaces with uneven layer thickness and having tiny features.
Control-Display Affordances in Simulation Based Education
Authors: Harper Sam , Sivanathan Aparajithan , Lim Theodore , Mcgibbon Scott , Ritchie James
Published: November 2018

Mixed reality opens new ways of connecting users to virtual content. With simulation-based education and training (SBET), mixed reality offers an enriched environment to experience digital learning. In turn, learners can develop their mental models to process and connect 2D/3D information in real-world settings. This paper reports on the use of the Microsoft HoloLens to create a mixed reality SBET environment. The challenges of this investigation are harmonising augmented real-world content, including the use of real-time, low-latency tracking of tangible objects and the interaction of these with the augmented content. The research emphasis is on technology-mediated affordances. For example, what affordance does the HoloLens provide the leaner in terms of interactive manipulation or navigation in the virtual environment? We examine this through control-display (CD) gain in conjunction with cyber-physical systems (CPS) approaches. This work builds on previously attained knowledge from the creation of an AR application for vocational education and training (VET) of stonemasonry.
Influence of the Initial Temperature on the Clutch Hot Judder
Authors: Yu Liang , Kim Il Yong
Published: November 2018

In order to explore the effects of the initial temperature on the clutch hot judder, the thermodynamic analysis was conducted during the clutch engagement process. The finite element analysis was adopted to explore the contact pressure based on the consideration of the concentrated reactive force on the circlip. A 4-degree-of-freedom torsional vibration model was established to evaluate the hot judder behavior. The results demonstrated that the closer the surface was to the circlip, the greater the friction torque generated on friction surfaces was. Moreover, the higher the initial temperature was, the shriller the clutch hot judder was. The increased initial temperature not only resulted in the increase in the maximum surface temperature, but also could make the clutch engagement much shorter.
System Level Design Optimization Method for Lightweight Manufacturable Design
Authors: Nucci Michael , Sabiston Graeme , Carrick Christopher , Kim Il Yong
Published: November 2018

This paper presents a method for a system level design optimization, using currently available commercial tools. A process outlining the optimization steps to be used was created based on performing topology optimization on important components and performing a conceptual topology optimization on the entire system. Using this process, a study was performed on a ceiling structure provided by an industry partner. From the design requirements, three primary areas were targeted for design optimization, the component level optimization of the cross beam component, the component level optimization of a roof attachment bracket, and the system level of the general roof structure. This study produced a design for the ceiling structure that reduced the total mass of the system by 34%, while also reducing the amount of total components in the system by 30%.
A Geometric Path-Planning Algorithm in Cluttered Planar Environments Using Convex Hulls
Authors: Masoudi Nafiseh , Fadel Georges
Published: November 2018

The problem of finding a collision free path in an environment occupied by obstacles, known as path planning, has many applications in design of complex systems such as wire routing in automobile assemblies or motion planning for robots. Developing the visibility graph of the workspace is among the first techniques to address the path-planning problem. The visibility algorithm is efficient in finding the global optimal path. However, it is computationally expensive as it explores the entire workspace of the problem to create all non-intersecting segments of the graph. In this paper, we propose an algorithm based on the notion of convex hulls to generate the partial visibility graph from a given start point to a goal point in a 2D workspace cluttered with a number of disjoint polygonal convex or concave obstacles. The algorithm facilitates the attainment of the shortest path in a planar workspace while reducing the size of the visibility graph to explore.
Effect of Stiffener Configuration on Bulkhead Modal Parameters
Authors: Warwick Braden T. , Mechefske Chris K. , Kim Il Yong
Published: November 2018

Optimization of bulkhead stiffener configuration has been an active area of research over the past decade, but no real practical solutions have been generated. This research investigates bulkhead stiffener configuration on a rudimentary level, by analyzing the modal parameters of three different stiffener configurations. Experimental data was used to validate the computational models of two modified bulkhead stiffener configurations. Operational boundary conditions were then applied to the computational models to assess the modal density of the modified bulkheads within the aircraft engine rotational frequency range. Removal of one horizontal stiffener reduced the overall stiffener mass by 12.2% without generating any modes within 4% of the engine rotational frequency. The inconsistencies of natural frequency changes due to stiffener configuration highlights the difficulty with applying generalized optimization approaches without a thorough understanding of the modes of interest. The results of this work suggest that the fundamental analysis performed herein is necessary to generate a complete understanding of the modal parameters of the bulkhead prior to performing in-depth optimization work.
2-D Inverse Dynamics Knee Model: Aligning Anatomical Knee Model With Knee Extension Kinematic Data Using Ligament Forces
Authors: Salinas Jose Mario , Caruntu Dumitru I.
Published: November 2018

This paper deals with aligning knee geometrical anatomical data with kinematic data from experimental work in order to develop a two-dimensional inverse dynamics anatomical model of human knee. Motion capture cameras were used to collect the experimental data for a knee extension exercise. Reflective markers were placed on the subjects’ skin during the experiment. In this model, joints such as hip, knee, and ankle are represented by axes of rotation. These axes are determined by calculating the relative instantaneous center of rotation of one body segment with respect to an adjacent body segment. Body-fixed coordinate systems were defined using three reflective markers attached to the subject. The origin of each body fixed-coordinate system was located between the three markers on that body segment, the body-fixed x-axis was pointing towards the marker on the lateral side of the body segment, and the body-fixed y-axis fell on the same plane as the three reflective markers on the body segment. Moreover, the axis of rotation that represents the hip was determined by calculating the instantaneous center of rotation of reflective markers located on the pelvis with respect to a body fixed coordinate system on the thigh. The axis of rotation on the knee was determined by calculating the instantaneous center of rotation of reflective markers on the shin (tibia) with respect to the body-fixed coordinate system on the thigh (femur). The axis of rotation on the ankle was determined by calculating the instantaneous center of rotation of reflective markers on the shin with respect to a body-fixed coordinate system on the foot. Bone anatomical geometries of femur and tibia were represented mathematically as polynomials and superimposed over the experimental data. This was done by matching the center of rotation from experimental data with the geometric center of the femoral condyle. This is necessary for estimating the insertions/origins of knee ligaments. These ligaments are modeled as nonlinear elastic springs. Furthermore, ligaments were divided into separate fiber bundles. Both the posterior and anterior cruciate ligaments were divided into an anterior and posterior fiber bundle. The cruciate ligament forces for both exercises are discussed in this paper.
Torsion Vibrations and Dynamic Stability of a Marine Driveline With Hydraulically Actuated Multi-Disk Clutch
Authors: Cavallin Mauro , Doria Alberto , Meneghetti Giovanni , Sacchi Daniele
Published: November 2018

The driveline of many crafts during mooring maneuvers operates in the “trolling” mode, which is characterized by large slippages of the clutch. Sometimes the properties of clutch material and oil lead to the onset of self-excited torsion vibrations and wide fluctuations in torque. To analyze this phenomenon a numerical model of a typical marine driveline is developed, friction characteristics of the clutch are simulated by means of a LuGre model. A parametric stability analysis is carried out to highlight the effect of the parameters of the LuGre friction model on the stability of torsion vibrations. A series of experimental tests is performed on a specific test bench to identify the parameters of the driveline and to validate the numerical model. Results shows that the updated numerical model is able to replicate experimental results.
The Influence of Physical Examples on Originality and Fixation in Engineering Design
Authors: Simmons Christopher C. , Kershaw Trina C. , LeGendre Alexander , Bhowmick Sankha
Published: November 2018

Improving creativity in engineering design continues to be a challenge. The relationship between fixation and creativity within engineering is mixed, as engineers desire to be innovative, yet are usually working from their existing knowledge to redesign existing products. In the current study, we wanted to examine the influence of physical examples on originality and fixation at the freshmen and senior level in a Mechanical Engineering program. We compared concepts for garbage collection systems generated by two groups — one provided with an example product (Example group), and another who did not receive an example product (No Example group). Using metrics established in prior publications, we found that seniors had higher levels of originality than freshmen whether an example product was received or not, reinforcing our previous findings. Fixation scores were higher for the group that did have an example. Receiving an example product was not a predictor of originality on its own, but did interact with curriculum and fixation level. Within the group that received an example product, there was a negative relationship between fixation and originality, particularly for the seniors. Within the group that did not receive an example product, there was no significant relationship between fixation and originality. Further analysis of our results are required to delineate how not receiving an example product influences design approach in freshmen and senior engineering students.
A Proposed Quality Metric for Ideation Effectiveness
Authors: Cheeley Avery , Weaver Morgan B. , Bennetts Caleb , Caldwell Benjamin W. , Green Matthew G.
Published: November 2018

A suitable quality metric is essential to improving ideation effectiveness. Many proposed quality metrics struggle to adequately capture this critical, subjective concept in a reliable and efficient way. This paper shows our development and testing of a quality metric that is meaningful, repeatable, and efficient. This quality metric is a weighted sum of quality dimensions adapted from the literature. The weighting factors for each dimension are adjusted to the specific ideation problem, and we present here a systematic method to quickly determine these weightings by experimental means. We demonstrate repeatability of the quality metric through interrater reliability, we show meaningfulness by comparing with raters’ intuitive interpretation of quality, and we demonstrate efficiency in the rating process. These initial findings show the quality metric has great promise and merits additional testing and refinement in future work.
Inclusive Toy Design From a Lead User With Extraordinary Needs
Authors: Grover Micki C. , Clarke-Sather Abigail R.
Published: November 2018

Products designed for the mass market, especially toys, can leave children with extraordinary needs unable to use them; products created using inclusive design principles can limit the intention of the design by altering original design parameters to become as wide as possible so that users with a range of abilities can use them. In contrast, designing for lead users with disabilities by focusing on a select group of people with extraordinary needs can drive design forward for a less specific population. Undergraduate engineering students from the University of Minnesota Duluth designed toys to meet the unique developmental needs of such a lead user, a child with hemiplegic cerebral palsy (CP). By focusing on the extreme needs of one specific child, the students designed toys that were engaging for the lead user as well as the preschoolers.

Three toys were prototyped using 3D printing and woodworking techniques and given to the lead user, age 4, as well as a group of children from a local daycare center, ages 16 to 33 months. The duration of each child’s interactions with the toys as well as the number of children able to accomplish the intended functions of the toys were tracked. The lead user accomplished 6 of the 9 total functions designed for the toys, 4 of which while using two hands. Additionally, the lead user accomplished 4 functions that under 50% of the daycare children accomplished. In general, the daycare center children played with the toys longer than the lead user. The toys engaged all the children in play that encouraged two-handed fine motor development, a challenge for children with hemiplegic CP.
Design Methods Used During Early Stages of Product Development: Three Company Cases
Authors: Lauff Carlye A. , Kotys-Schwartz Daria , Rentschler Mark E.
Published: November 2018

Companies need to employ new design methods and tools to remain competitive in today’s global economy. Design methods are used to help teams move through the different stages of the design process, such as during project scoping, concept generation, and concept selection. Concept generation design methods are meant to help teams generate diverse, novel, and creative potential solutions. However, most design methods are developed and refined based on studies with student teams. This limits our understanding of how professionals engage with design methods in practice. This is a case study exploring the design methods used by three companies during the early stages of new product development. These companies are from the consumer electronics, footwear, and medical devices industries, and each design team within the companies was tasked with developing a new physical end product. We identified that all three teams heavily relied on internal and external benchmarking and reverse engineering design methods as part of concept generation. Ultimately, the products they developed were all considered evolutionary, meaning that the final product was a slightly improved version of similar products already on the market. This contrasts revolutionary products, which can change or disrupt the current field in one or more ways. This research contributes to design theory and methodology through empirically studying how companies engage in the design process, identifying the methods employed by professionals, and raising new questions about design methods, especially translation to industry. This research also contributes to design education by identifying methods that professionals use in practice, which can translate to direct recommendations for improving project-based engineering design courses.
A Stochastic Approach for Performance Prediction of Aircraft Engine Components Under Manufacturing Uncertainty
Authors: McKeand Austin M. , Gorguluarslan Recep M. , Choi Seung-Kyum
Published: November 2018

Efficient modeling of uncertainty introduced by the manufacturing process is critical in the design of the components of the aircraft engines. In this study, a stochastic approach is presented to efficiently account for the geometric uncertainty, associated with the manufacturing process, in the accurate performance prediction of aircraft engine components. A semivariogram analysis procedure is proposed in this approach to quantify spatial variability of the uncertain geometric parameters based on the manufactured specimens. Karhunen-Loeve expansion is utilized to create a set of correlated random variables from the uncertainty data obtained by variogram analysis. The detailed model of the component is created accounting for the uncertainties quantified by these correlated random variables. A stochastic upscaling method is then utilized to form a simplified model that can represent this detailed model with high accuracy under uncertainties. Specifically, a parametric model generation process is developed to represent the detailed model using Bezier curves and the uncertainties are upscaled to the parameters of this parametric representation. The modal frequency-based reliability analysis of a turbine blade example is used to demonstrate the efficacy of the proposed approach. The application results show that the proposed method effectively captures the geometric uncertainties introduced by manufacturing while providing accurate predictions under uncertainties.
Design Innovation Approaches for Sustainable Smart Energy Systems
Authors: Lan Lan , Tushar Wayes , Sng Karen Hui En , Yuen Chau , Wood Kristin L. , Saha Tapan
Published: November 2018

This paper studies an interdisciplinary approach for improving smart energy systems, and, in particular, building energy efficiency. Currently, energy audit is the most widely used approach to improve building energy efficiency. Energy audit increases the building energy efficiency by identifying, analyzing and implementing energy saving opportunities in existing buildings. The procedure of existing energy audit approach is relatively standardized, and energy audit professionals usually refer to Energy Conservation Measures (ECMs) checklists to determine opportunities for energy savings. In this context, this paper aims to improve the general energy audit process by integrating, adapting, and extending Design Innovation (DI) techniques which help to identify more energy saving opportunities beyond the existing energy audit checklists and deliver user-centered and disruptive innovative energy-saving solutions which are missing in the traditional energy audit procedure. The motivation, advantages, and the implementation procedure of selected DI approaches are explained separately. To demonstrate the effectiveness of the proposed mechanism, an example of developing a smart energy system for a building testbed is given.
Matrix Analysis of Second-Order Kinematic Constraints of Single-Loop Linkages in Screw Coordinates
Authors: Wu Liheng , Müller Andreas , Dai Jian S.
Published: November 2018

Higher order loop constraints play a key role in the local mobility, singularity and dynamic analysis of closed loop linkages. Recently, closed forms of higher order kinematic constraints have been achieved with nested Lie product in screw coordinates, and are purely algebraic operations. However, the complexity of expressions makes the higher order analysis complicated and highly reliant on computer implementations. In this paper matrix expressions of first and second-order kinematic constraints, i.e. involving the Jacobian and Hessian matrix, are formulated explicitly for single-loop linkages in terms of screw coordinates. For overconstrained linkages, which possess self-stress, the first- and second-order constraints are reduced to a set of quadratic forms. The test for the order of mobility relies on solutions of higher order constraints. Second-order mobility analysis boils down to testing the property of coefficient matrix of the quadratic forms (i.e. the Hessian) rather than to solving them. Thus, the second-order analysis is simplified.
Design Processes of Design Automation Practitioners
Authors: Anderson David , Perez K. Blake , Xuereb Zack , Otto Kevin , Wood Kris
Published: November 2018

The use of computers during the design process continues to grow, calling for a better understanding of how experts make use of computer tools to automate and augment their design efforts. In this study, we examine how architects and engineers consider the use of computers and computation in planning a solution to a sample design problem. We find the design automation design process can be modeled with four phases; discovery, evaluation, extrapolation and interpolation. Unlike many design methods, we find the evaluation phase generally preceded the extrapolation phase. In addition, we identify common computational strategies and challenges faced by practitioners. Understanding this information can help advise and provide directions for designers across levels of expertise, to better integrate computers and computation in existing design work, and to direct further efforts in design automation research.
Nonlinear Response of an Inextensible, Cantilevered Beam Subjected to a Nonconservative Follower Force
Authors: McHugh Kevin A. , Dowell Earl H.
Published: November 2018

The dynamic stability of a cantilevered beam actuated by a nonconservative follower force has previously been studied for its interesting dynamical properties and its applications to engineering designs such as thrusters. However, most of the literature considers a linear model. A modest number of papers considers a nonlinear model. Here, a system of nonlinear equations is derived from a new energy approach for an inextensible cantilevered beam with a follower force acting upon it. The equations are solved in time, and agreement is shown with published results for the critical force including the effects of damping (as determined by a linear model). This model readily allows the determination of both in-plane and out-of-plane deflections as well as the constraint force. With this novel transparency into the system dynamics, the nonlinear post-critical limit cycle oscillations are studied including a concentration on the force which enforces the inextensibility constraint.
How Do Designers Choose Among Multiple Noisy Information Sources in Engineering Design Optimization? An Experimental Study
Authors: Chaudhari Ashish M. , Bilionis Ilias , Panchal Jitesh H.
Published: November 2018

Designers make process-level decisions to (i) select designs for performance evaluation, (ii) select information source, and (iii) decide whether to stop design exploration. These decisions are influenced by problem-related factors, such as costs and uncertainty in information sources, and budget constraints for design evaluations. The objective of this paper is to analyze individuals’ strategies for making process-level decisions under the availability of noisy information sources of different cost and uncertainty, and limited budget. Our approach involves a) conducting a behavioral experiment with an engineering optimization task to collect data on subjects’ decision strategies, b) eliciting their decision strategies using a survey, and c) performing a descriptive analysis to compare elicited strategies and observations from the data. We observe that subjects use specific criteria such as fixed values of attributes, highest prediction of performance, highest uncertainty in performance, and attribute thresholds when making decisions of interest. When subjects have higher budget, they are less likely to evaluate points having highest prediction of performance, and more likely to evaluate points having highest uncertainty in performance. Further, subjects conduct expensive evaluations even when their decisions have not sufficiently converged to the region of maximum performance in the design space and improvements from additional cheap evaluations are large. The implications of the results in identifying deviations from optimal strategies and structuring decisions for further model development are discussed.
Methods and Analysis of 3D Shape Unfolding and Folding for Radiotherapy
Authors: Li Rui , Peng Qingjin , Ingleby Harry , Sasaki David
Published: November 2018

A sheet of material called bolus is commonly used in the high-energy radiotherapy to treat tumors near the skin surface of patients for a desired dose distribution. The existing method of bolus shaping is a manual process to cut the material into 2D shapes and then wrap them to fit the targeted body surface in clinic. This method cannot cover the bolus on some irregular surfaces such as knee, nose and elbow precisely. The inaccurate coverage will generate air gaps between the bolus and skin. An unfolding method for bolus shaping is introduced in this paper to reduce the air gaps. The shaping process is achieved by planning unfolding strategy to overcome limitations of existing software tools. A case study of bolus shaping for human nose is presented to examine the proposed shaping process. The shaping process includes the surface scanning to obtain point cloud data, 3D surface forming, segmentation and unfolding of the surface. The solution is verified by comparing the 3D model surface and wrapped shape of unfolded patches.
Improved Benchmarking Method Using Kinematics Analysis in Design of an Upper Limb Exoskeleton Rehabilitation Device
Authors: Shi Yanlin , Peng Qingjin
Published: November 2018

Conceptual design plays an important role in product development to meet requirements of the product function, cost and other factors. Existing methods of the product conceptual design rely on experience of designers or benchmarking methods to estimate design parameters, which limits the design automation and optimization. This paper improves the benchmarking methods by integrating the kinematics analysis with quality function deployment in design of an upper limb exoskeleton rehabilitation device. Parameters such as velocity, acceleration and displacement of the product are included for rating benchmarking products to evaluate the rehabilitation device based on customer needs. By integrating the benchmarking method and kinematics analysis, products with the best performance can be determined accurately to help designers to improve the existing product or develop a new product. The proposed method is verified in the design of an upper limb rehabilitation device.
Adaptive Extended Jacobian Can Improve the Global Conditioning Index of Redundant Robots
Authors: Simas Henrique , Di Gregorio Raffaele
Published: November 2018

The extended Jacobian is a solution technique of redundant robot’s instantaneous kinematics. It is based on the definition of secondary tasks through constraint functions that are added to the mapping between joint rates and end-effector’s twist. Several approaches showed its potential, its applications and limitations. In general, the constraint functions are a linear combination of basic functions with constant coefficients. This paper proposes the use of adaptive coefficients in such equations by using the conditioning index of the extended Jacobian as a quality measure. A good conditioning of the extended Jacobian keeps the robot far from singularities and contributes to the solution of the inverse kinematics. In this paper, initially the extended Jacobian and the proposed algorithm are discussed, then two tests in different circumstances are presented to validate the proposal.
Numerical Assessment of 2D Aeroacoustic Simulations for Landing Gear
Authors: Alqash Sultan I. , Behdinan Kamran
Published: November 2018

Landing gears (LG) are primarily designed to support the entire loads of an aircraft during landing, taxiing, and taking off. From aerodynamic design prospective, many of the LG components are exposed to the air flow giving rise to what so-called aerodynamic noise. Numerical study of complex systems such as LG as a three-dimensional (3D) model is not only CPU and memory consuming, but also it is way beyond the demand of industries for quick estimate during the design stage [1–3]. To understand the underlying physics of the flow induced noise, a two-dimensional (2D) flow past a circular cylinder is simulated using ANSYS Fluent. Two different Reynolds numbers, Re = 150 and 90000 are examined. For low Re, two distinct numerical conditions relevant to steady and unsteady flow are simulated and compared to examine the effect of the time dependency on the acoustic field. At high Re, the acoustic field is computed using the built-in Ffowcs William and Hawkings (FW-H) acoustic analogy solver in Fluent. The results show the importance of including the unsteady state term to extract the flow data. The far-field noise prediction is found to be highly dependent on the location of the near-field data.
The Homotopy Analysis for the Nonlinear Dynamics of Planetary Gear Trains
Authors: Xun Chao , Jiao Sujuan , Chen Yong , Long Xinhua
Published: November 2018

In this paper, the homotopy analysis method (HAM) is proposed to study the nonlinear oscillators of planetary gear trains, in which the periodically time-varying mesh stiffness and gear backlash are included through a nonlinear displacement function. In contrast to the traditional perturbation methods, the HAM does not require a small parameter in the equation under study, and then can be applied to both of the weakly and strongly nonlinear problems. In this article, firstly the closed-form approximations for the dynamic response of planetary gear trains are obtained by HAM. The analytical solutions give insight into the nonlinear dynamics and the impact of system parameters on dynamic response. The accuracy of HAM solutions is evaluated by numerical integration simulations. Results indicate that with large tooth separation times, the amplitude-frequency curves obtained by HAM agree better with the results obtained by NI than those obtained by the MMS.
Performance Analysis of Rapid Tool in Electrical Discharge Machining During Machining of Titanium Alloy (Ti6Al4V)
Authors: Sahu Anshuman Kumar , Mahapatra Siba Sankar
Published: November 2018

Titanium and its alloys are a class of metallic materials having high strength to weight ratio with excellent properties of resistance to temperature, corrosion and oxidation. These properties increase their use in aerospace, chemical and biomedical industries. Electrical discharge machining (EDM), a non-conventional machining process, is the most suitable process for the machining of titanium and its alloys. Generally, tool electrode for EDM application is prepared through various conventional and non-conventional machining processes. The cost of production of EDM electrodes accounts for more than 50% of the cost of the final product. Therefore, additive manufacturing (AM) technology can be suitably applied for direct manufacturing of the complex EDM electrodes. Selective laser sintering (SLS) is one of the appropriate AM processes for preparation of EDM tool electrode. In the present work, machining performance of the AlSi10Mg tool electrode produced through AM process along with copper and brass tool electrodes have been studied considering titanium alloy (Ti6Al4V) as work piece material and commercial grade EDM 30 oil as dielectric fluid. In addition to the tool electrodes, two more EDM parameters such as pulse-on-time (Ton) and discharge current (Ip) have been considered. Four performance measures like material removal rate (MRR), tool wear rate (TWR), average surface roughness (Ra) and surface crack density (SCD) are used to assess the machining performance. In order to reduce the number of experiments, design of experiment (DOE) approach like Taguchi’s L9 orthogonal array is used. Since the performance measures are conflicting in nature, grey relational analysis (GRA) is used to convert four performance measures into an equivalent single performance measure. The best parametric condition is reported for optimal grey relational grade.
Using the Parts Used to Be Removed to Improve Compliant Joint’s Performance
Authors: Xie Zhongtian , Qiu Lifang , Yang Debin
Published: November 2018

Compliant mechanisms gain their mobility from the deflection of flexible members. Compliant joints are the basis of compliant mechanisms, their performance has great influence on compliant mechanisms’ characteristics. This paper presents the concept that the parts used to be removed during design and manufacture processes can be retained and redesigned to improve compliant joints’ performance. They are designed specially to help to improve the joints’ ability to resist tension and compression. Some examples are proposed and discussed. 3D models are created and analyzed using finite element analysis (FEA) to verify the design concepts. A benchmark Lamina Emergent Torsional (LET) joint is also analyzed through FEA. The results obtained from FEA confirm the design concepts presented in this paper very well. Some other applications are also proposed and discussed.
Design for Additive Manufacturing of Conformal Cooling Channels Using Thermal-Fluid Topology Optimization and Application in Injection Molds
Authors: Wu Tong , Tovar Andres
Published: November 2018

Additive manufacturing allows the fabrication parts and tools of high complexity. This capability challenges traditional guidelines in the design of conformal cooling systems in heat exchangers, injection molds, and other parts and tools. Innovative design methods, such as network-based approaches, lattice structures, and structural topology optimization have been used to generate complex and highly efficient cooling systems; however, methods that incorporate coupled thermal and fluid analysis remain scarce. This paper introduces a coupled thermal-fluid topology optimization algorithm for the design of conformal cooling channels. With this method, the channel position problem is replaced to a material distribution problem. The material distribution directly depends on the effect of flow resistance, heat conduction, as well as forced and natural convection. The problem is formulated based on a coupling of Navier-Stokes equations and convection-diffusion equation. The problem is solved by gradient-based optimization after analytical sensitivity derived using the adjoint method. The algorithm leads a two -dimensional conceptual design having optimal heat transfer and balanced flow. The conceptual design is converted to three-dimensional channels and mapped to a morphological surface conformal to the injected part. The method is applied to design an optimal conformal cooling for a real three dimensional injection mold. The feasibility of the final designs is verified through simulations. The final designs can be exported as both three-dimensional graphic and surface mesh CAD format, bringing the manufacture department the convenience to run the tool path for final fitting.
Development of LCA Module Integrated With CAD for Eco-Assessment of Machined Products
Authors: Tao Jing , Yu Suiran
Published: November 2018

LCA predicts the life cycle impacts of product solutions and can help determine what solution is better for the environment. However, LCA is very data dependent and requires in-depth knowledge to explicit relate environmental impacts of product to its design attributes. Current LCA methods are generally still not adapted to designers, who often lack the expertise and time to make LCA efficiently useful to their daily work. This study aims to develop a LCA module integrated with CAD system for machined products. The module employs a feature-based approach for identify, extract and convert life cycle related data in existing product models for LCA modeling and analysis. A coding system for machining feature representation and a rule-based reasoning package to generate manufacturing plans based on feature codes are developed to enable convenient eco-assessment along with CAD modeling of machined products. A step shaft LCA case study is presented to demonstrate the proposed approach.
Life Cycle Assessment of SOFCs-Based Auxiliary Power Unit in China
Authors: Wen An , Tao Jing , Yu Suiran
Published: November 2018

Reducing energy consumption and environmental pollution of road transportation is one of the major challenges to China’s commitment to sustainable development. This paper aims to establish the LCA model of solid oxide fuel cells-based auxiliary power unit (SOFC-APU) for heavy vehicles with Chinese background for analysis of potential environmental benefits of its implementation in China. First, the LCA of the SOFC power using natural gas as the cells’ fuel is performed using eBalance, which is the Chinese LCA software with high quality domestic underlying database, and the results show that the fuel production phase is a major contributor to SOFC-APU’s life-cycle environmental impacts. Then the comparative LCA analysis of SOFC-APU using biomass ethanol from different feedstock planting areas in China is presented and results show that using corn-based ethanol fuel can potentially lower the lifecycle environmental impacts of SOFC-APU by 37.7%.
Students As Sequential Decision-Makers: Quantifying the Impact of Problem Knowledge and Process Deviation on the Achievement of Their Design Problem Objective
Authors: Shergadwala Murtuza , Bilionis Ilias , Panchal Jitesh H.
Published: November 2018

Factors such as a student’s knowledge of the design problem and their deviation from a design process impact the achievement of their design problem objective. Typically, an instructor provides students with qualitative assessments of such factors. To provide accurate assessments, there is a need to quantify the impact of such factors in a design process. Moreover, design processes are iterative in nature. Therefore, the research question addressed in this study is, How can we quantify the impact of a student’s problem knowledge and their deviation from a design process, on the achievement of their design problem objective, in successive design iterations? We illustrate an approach in the context of a decision-making scenario. In the scenario, a student makes sequential decisions to optimize a mathematically unknown design objective with given constraints. Consequently, we utilize a decision-making model to abstract their design process. Their problem knowledge is quantified as their belief about the feasibility of the design space via a probability distribution. Their deviation from the decision-making model is quantified by introducing uncertainty in the model. We simulate cases where they have a combination of high (or low) knowledge of the design problem and high (or low) deviation in their design process. The results of our simulation study indicate that if students have a high (low) deviation from the modeled design process then we cannot (can) infer their knowledge of the design problem based on their problem objective achievement.
A MEMS Threshold Acceleration Switch Powered by a Triboelectric Generator
Authors: Pallay Mark , Ibrahim Alwathiqbellah I. , Towfighian Shahrzad
Published: November 2018

In this paper a novel electrostatic MEMS combined shock sensor and normally-closed switch is presented. The switch uses combined attractive and repulsive forcing to toggle a cantilever beam to and from the pulled-in position. The attractive force is generated through a parallel plate electrode configuration and induces pull-in. The repulsive force is generated through electrostatic levitation from a third electrode and serves to pull the beam out of its pulled-in position. A triboelectric transducer converts impact energy to electrical energy to provide voltage for the third electrode, which temporarily opens the switch if enough impact energy is supplied. Triboelectricity addresses the high voltage requirement for electrostatic levitation. The multi-electrode sensor also addresses the low current output from the generator because it acts as an open circuit between the parallel plate and levitation electrodes. A theoretical model of the switch is derived to analyze stability and the dynamic response of the cantilever. Threshold voltages to pull-in and release the beam through repulsive forcing is calculated. Output voltage plots from a prototype generator under a single impact are applied to the sensor-switch model to demonstrate the working principle of the sensor-switch is feasible.
Localization of a Miniature Spherical Rolling Robot Using IMU, Odometry and UWB
Authors: Nguyen Van Duong , Soh Gim Song , Foong Shaohui , Wood Kristin
Published: November 2018

Robots that rolls with a spherical body or spherical robots, exhibits a high degree of mobility and amazing recovery capability from collisions while traversing in the environment. However, the localization of spherical robots in a GPS-denied environment for Intelligent Surveillance and Reconnaissance (ISR) task is a challenging problem due to the complexity of its system dynamics and the limited available sensors technology to sense out of the spherical shell. In our prior work, a kinematic localization technique based on odometry and inertial measurement unit (IMU) sensing was proposed and implemented onto our miniature spherical robot Virgo, for pose estimation. However, it suffers from errors due to slippages during locomotion or as a result of the collision. In this paper, we present a solution to this problem by the inclusion of an additional ultra-wideband (UWB) sensor and fuse it with our kinematic pose estimator using Extended Kalman Filter for indoor localization. Experiments are conducted on a multi-waypoint trajectory to verify its validity and had shown to improve localization performance.
A Time-Frequency Analysis Approach Based on Plane Partition for Fault Diagnosis of the Planetary Gearbox Under Nonstationary Conditions
Authors: Hu Yue , Tu Xiaotong , Li Fucai
Published: November 2018

The planetary gearbox is one of the key components in the rotating machinery. The planetary gearbox is prone to malfunction, which increases downtime and repair costs. Hence, the fault diagnosis of the planetary gearbox is an important research topic. The acquired signal from the planetary gearbox exhibit strongly time-variant and nonstationary features since the planetary gearbox usually works at time-varying speeds. In this study, a new time-frequency analysis method is proposed. This method takes the spectrum shape into account and partitions the time-frequency into several components. Then the fault feature of the planetary gearbox is detected by analyzing the decomposed components. The simulated signal and the experimental signals under nonstationary conditions are analyzed to verify the effectiveness the proposed method. Results show that the proposed method can efficiently extract the fault feature of the planet gear.
Study on the Dynamics of IMU Isolation System Based on Transfer Matrix Method for Multibody Systems
Authors: Tao Yu , Rui Xiaoting , Yang Fufeng , Zhang Jianshu
Published: November 2018

An important way to improve the dynamical test accuracy of an inertial measurement unit (IMU) is to suppress its vibration. In this paper, the dynamics model of a laser gyro strapdown IMU is developed based on the new version of the transfer matrix method for multibody systems (MSTMM). According to the dynamics model, acceleration responses of the IMU system with and without control are numerically computed under random excitation. The results show that the work situation of the IMU can be significantly improved by adopting magnetorheological elastomer (MRE) isolators, which provides a new technical means of upgrading the output precision of IMU.
Studying the Effect of Freeplay on Nose Landing Gear Shimmy Using a Fully Nonlinear Model
Authors: Rahmani Mohsen , Behdinan Kamran
Published: November 2018

Shimmy is a common instability of landing gear systems which has been known for a long time. Yet, it is often studied using simplified dynamic models in which the chief system nonlinearities are neglected. Particularly, the influence of worn components and loose joints manifesting itself as a freeplay nonlinearity has been only touched upon in few works. The present paper utilizes a fully nonlinear landing gear dynamic model to obtain nonlinear stability boundaries and to study the onset, severity, frequency jumps, and mode shifts of the system as a result of the torque link freeplay. Using stability maps in the parameter space and time histories of the oscillations the degrading effect of excessive clearance and wear in the torque links is demonstrated, which in turn offers insights for designing shimmy-free landing gears.