A Comparison of Function- and Affordance-Based Design

Function-based design is the traditional approach in engineering design theory, proving useful and practical in many cases but showing limitations in others. Affordance-based design is an alternative approach that attempts to address some of function theory’s limitations by focusing attention on the interactions between systems. This paper compares function-based design with affordance-based design by examining their philosophies, tools, abilities, and suitability along a number of dimensions. We conclude that the approaches are compatible and suggest future work to realize their integration.

Proposal of an Activity-Based Adaptive Process Model for Innovative Design

In this paper, we introduced an activity-based adaptive process model that views innovative design as a complex adaptive system. Instead of predefining the process architecture, we constructed the model framework by adaptively selecting the design activity by the activity value. We defined the activity value as the complexity reduction associated with the possibility of satisfying the design targets and design stages. Moreover, this paper contributes an expert evaluation methodology to evaluate the activity value in order to balance innovation and control. Finally, we applied the model to an industrial case and analyzed the simulation results.

A Nested Multivariate Utility Copulas Approach to Aggregating User Experience Partworths for Aircraft Cabin Interior Design

User experience (UX) design involves combination of different design attributes with their corresponding attribute levels to form different product profiles. This raises the issue of how to integrate corresponding UX of individual design attribute levels (i.e., partworth UX measures) into a holistic measure of UX of the entire product profile. Traditional methods often use a weighted sum of single partworth UX strategy without considering their dependence. This paper proposes to use utility copulas to accommodate the dependence of individual partworth UX measures. Single utility functions are constructed based on cumulative prospect theory, based on which multivariate Archimedean utility copulas are constructed using a nested structure based on the modularized attributes. A case study of aircraft cabin interior design is demonstrated to show the potential and feasibility of the proposed methodology.

Loading and Design Parameter Uncertainty in the Dynamics and Performance of High-Speed-Parallel-Helical Stage of a Wind Turbine Gearbox

The Wind Turbine Gearboxes (WTGs) are highly subjected to variable torsional and non-torsional loads. In addition, the manufacturing and assembly process of these devices results in uncertainty in the system. These gearboxes are reported to fail in their early life of operation, within three to seven years as opposed to the expected twenty years of operation. Their downtime and maintenance process is the most costly of any failure of subassembly of wind turbines. The objective of this work is to perform a probabilistic multibody dynamic analysis (PMBDA) of the high-speed-parallel-helical stage of the gearbox of wind turbine that considers uncertainty of generator side torque loading and the input shaft speed, assembly errors and design parameter uncertainty. System reliability, probability of failure, and probabilistic sensitivities of all the input variables towards several performance functions have been measured and conclusions have been drawn. PMBDA has demonstrated a new dimension of design and installation of wind turbine gearboxes than traditional deterministic approach. In addition to revealing system reliability or under-performance through probability of failure, the method will also help designers to consider certain variables critically through the sensitivity results.

Design and Test of Differential Planetary Gear System for Open Rotor Power Gearbox

The open rotor engine is a next generation aero-engine that satisfies the demand for high fuel efficiency and low CO2 emission. A differential planetary gear system is incorporated in the open rotor engine to connect the turbine output shaft and fan rotors in order to counter-rotate the fan rotors as well as allow the turbine and fan rotors to operate at more efficient speeds. The open rotor gear system is required to have not only 20,000 hp high power transmission, but also an increasingly high efficiency, high reliability and light weight. To achieve these requirements, the following design works were conducted; (1) a low misalignment and lightweight carrier, (2) a flexible structure to absorb the displacement caused by the flight load, (3) an optimum gear tooth modification and (4) reduction of oil churning and windage losses. Also, extensive analyses and simulations such as lube oil flow CFD, FEA and tooth contact analysis were conducted. A full scale prototype gear system was manufactured and validation tests were conducted using a newly constructed test rig to validate the design concept. A slow roll test, rated performance test and efficiency test were conducted. And the design concept was found to be valid. This paper describes details of the prototype design and the results of the validation tests.

Development of a Diagnosis Method of a Gear Tooth Surface by Predicting Laser Beam Reflection

We developed a new diagnostic method by using a laser beam. This method is as follows: A tooth surface is irradiated by the zonal laser beam from an oblique direction, and then the irradiated laser beam line is shifted along the surface of the tooth according to gear rotation. If the damage on the irradiated tooth surface exists, the voltage proportional to laser reflection increases. We developed the method to predict and make the reflection benchmark on the normal condition according to the gear surface. To make the benchmark of the diagnosis, the three dimensional basic-data map (x: irradiated angle, y: irradiated distance, z: reflection intensity) was created by measuring the gear only whose material, heat treatment, and roughness were same as the targeted gear. By using the equations of tooth profile and fillet curves calculated from the specifications of the targeted gear, the distance and angle relations between the laser sensor and the tooth surface can be derived. By using the three dimensional basic-data map, the benchmark can be created. The measured reflection data of the non-damage gear agreed well with the benchmark, therefore we can diagnose the various specification gears, if the targeted gear’s material, heat treatment, and roughness are same. Finally, by using the benchmark which was made by our developed method, we proposed a novel diagnosis method. The procedure of the method is as follows: 1) The benchmark is made from the targeted gear’s specifications. 2) To take into account the fluctuation of the benchmark line influenced by the roughness on the gear surface, normal condition area of the reflected data is defined in the range between −0.05 V and +0.05 V of the benchmark line. 3) The normal condition area and measured data is compared, if the measured data is deviated from the normal condition area, there is defined as the abnormal area possible to be damaged. To confirm the validity of this diagnosis method, the measured value of the damage area with caliper directly and calculated value from the method as mentioned above. The errors of the area and the location were within 20 %. Therefore, the effectiveness of the method using the benchmark data can be confirmed.

Tooth Flank Breakage: Influences on Subsurface Initiated Fatigue Failures of Case Hardened Gears

Pitting and tooth root breakage are typical fatigue failure modes of case hardened gears. Both failure types are usually initiated at the surface or close to the surface. General trends in modern gear industry, such as improved gear design with adequate flank modifications, high-quality gear materials and high-performance lubricants, modern manufacturing processes with additional post-processes as shot peening and superfinishing as well as advanced calculation methods, have allowed an optimized utilization of the allowable pitting and bending stress numbers in recent years. As a result of the increased power density, however, the stresses below the surface rise with the consequence of an increased risk of fatigue failure initiation in the material below the surface. This paper describes main characteristics of a failure mode characterized by tooth breakages which start in the area of the active flank from cracks that are typically initiated at a considerable depth beneath the loaded flank surface. Based on theoretical and experimental investigations, relevant influence parameters related to gear design, operating conditions and material strength on the failure mode “Tooth Flank Breakage” will be discussed and basic principles of a developed calculation model to evaluate the risk of such failures presented. Finally, exemplarily experimental results from gear running tests, which failed due to flank breakage, are compared to the results of the new calculation model.

Robust Optimization of Cylindrical Gear Tooth Surface Modifications Within Ranges of Torque and Misalignments

Tooth surface modifications are small, micron-level intentional deviations from perfect involute geometries of spur and helical gears. Such modifications are aimed at improving contact pressure distribution, while minimizing the motion transmission error to reduce noise excitations. In actual practice, optimal modification requirements vary with the operating torque level, misalignments, and manufacturing variance. However, most gear literature has been concerned with determining optimal flank form modifications at a single design point, represented by fixed, single load and misalignment values. A new approach to the design of tooth surface modifications is proposed to handle such conditions. The problem is formulated as a robust design optimization problem, and it is solved, in conjunction with an efficient gear contact solver (LDP), by a direct search, global optimization algorithm aimed at guaranteeing global optimality of the obtained micro-geometry solutions. Several tooth surface modifications can be used as micro-geometry design variables, including profile, lead, and bias modifications. Depending on the contact solver capabilities, multiple performance metrics can be considered. The proposed method includes the capability of simultaneously and robustly handling several conflicting design objectives. In the present paper, peak contact stress and loaded transmission error amplitude are used as objective functions (to be minimized). At the end, two example optimizations are presented to demonstrate the effectiveness of the proposed method.

Improving Overlapping Between Testing and Design in Engineering Product Development Processes

Testing components, prototypes and products comprise essential, but time consuming activities throughout the product development process particularly for complex iteratively designed products. To reduce product development time, testing and design processes are often overlapped. A key research question is how this overlapping can be planned and managed to minimise risks and costs. The first part of this research study investigates how a case study company plans testing and design processes and how they manage these overlaps. The second part of the study proposes a significant modification to the existing process configuration for design and testing, which explicitly identifies virtual testing, that is an extension to Computer Aided Engineering which mirrors the testing process through product modelling and simulation, as a distinct and significant activity used to (a) enhance and (b) replace some physical tests. The analysis shows how virtual testing can mediate information flows between overlapping (re)design and physical tests. The effects of virtual testing to support overlap of test and (re)design is analysed for the development phases of diesel engine design at a case study company. We assess the costs and risks of overlaps and their amelioration through targeted virtual testing. Finally, using the analysis of the complex interactions between (re)design, physical and virtual testing, and the scope for replacing physical with virtual testing is examined.