Myung-Seob Shin

Structural optimization of the automobile frontal structure for pedestrian protection and the low-speed impact test

Abstract A variety of regulations are involved in the design of an automobile frontal structure. The regulations are pedestrian protection, the Federal Motor Vehicle Safety Standard (FMVSS) part 581 bumper test, and the Research Council for Automobile Repairs (RCAR) test. The frontal structure consists of the bumper system and a crash box that connects the bumper system and the main body. The detailed design of the bumper system is performed to meet two conditions: first, regulation for pedestrian protection (lower-legform impact test); second, FMVSS part 581. In the two regulations, the stiffness requirements of the bumper system conflict with each other. In order to meet lower leg protection, a relatively soft bumper system is required, while a relatively stiff system is typically needed to manage the pendulum impact. A new bumper system is proposed by adding new components and is analysed by using the non-linear finite element method. An optimization problem is formulated to incorporate the analysis results. Each regulation is considered as a constraint from a loading condition, and two loading conditions are used. Response surface approximation optimization is utilized to solve the formulated problem. RCAR requires reduction in the repair cost when an accident happens. The repair cost in a low-speed crash could be reduced by using an energy-absorbing structure such as the crash box. The crash box is analysed by using the non-linear finite element method. An optimization problem for the crash box is formulated to incorporate the analysis results. Discrete design using orthogonal arrays is utilized to solve the formulated problem in a discrete space.

Optimization of the eccentric check butterfly valve considering the flow characteristics and structural safety

Abstract The eccentric check butterfly valve is a butterfly valve that has an eccentric rotating axis. It is not only used as a butterfly valve to control the flowrate or pressure, but also as a check valve to prevent backward flow. A new design process is proposed for designing the valve. First, an optimization problem with a characteristic function is formulated to determine the amount of eccentricity. The characteristic function to be minimized is defined for the flow characteristics. Second, the waterhammer pressure of the valve disc is calculated by waterhammer analysis when the flow stops suddenly. Structural analysis is carried out to evaluate the waterhammer pressure of the valve disc and structural safety. Structural optimization is performed considering the structural safety and the flow characteristics. The process of structural optimization has two steps: topology optimization and shape optimization. Mass distribution of the disc housing is determined using topology optimization. Since topology optimization does not give the final dimensions, shape optimization is utilized to determine the details based on the results of topology optimization. A light design is derived to satisfy the structural safety and the flow characteristics.

Design of the active hood lift system using orthogonal arrays

Abstract The majority of pedestrian fatalities and injuries are caused by traffic accidents. Injuries of occupants in a vehicle have been considerably decreased due to many efforts by the industry. However, efforts for the protection of pedestrians still seem to be insufficient. Many industries are striving for better protection of pedestrians by using an active hood lift system, rather than reforming the existing structure. The active hood lift system lifts the hood when the vehicle hits a pedestrian, thus mitigating head injury to the pedestrian. In this research, the active hood lift system is designed to enhance the performance for protection. The active hood lift system is analysed by using the non-linear finite element method. Computer simulation is conducted for the impact between the headform and the hood. An optimization problem is formulated to incorporate the analysis results. An iterative optimization algorithm using orthogonal arrays is utilized for the design in a discrete space. The injury level to the head is significantly reduced in the newly designed product.

Axiomatic design of the motor-driven tilt/telescopic steering system for safety and vibration

Abstract The design process of the motor-driven tilt/telescopic steering column is established by an axiomatic design approach in conceptual design. Since independent design parameters are defined for improving the performance of the steering system, each detailed design can be carried out independently. In detailed design, occupant safety in a crash environment and vibration reduction are considered. The occupant analysis code SAFE (Safety Analysis For occupant crash Environment) is utilized to simulate the body block test. Segments, contact ellipsoids and spring-damper elements are used to model the steering column in SAFE. The model is verified by the result of the body block test. After the model is validated, the energy absorbing components are designed using an orthogonal array. Occupant analyses are performed for the cases of the orthogonal array. Final design is determined for minimum occupant injury. For vibration analysis, a finite element model of the steering column is defined for the modal analysis. The model is validated by vibration experiments. Size and shape variables are selected for the optimization process. Optimization is conducted to minimize the weight subjected to various constraints.

Occupant analysis and seat design to reduce neck injury from rear end impact

Occupant injury from rear end impact is rapidly becoming one of the most aggravating traffic safety problems with high human suffering and societal costs. Although rear end impact occurs at a relatively low speed, it may cause permanent disability due to neck injuries resulting from an abrupt moment, shear force, and tension/compression force at the occipital condyles. The analysis is performed for a combined occupant-seat model response, using the SAFE (Safety Analysis For occupant crash Environment) computer program. A simulation model is established to match the sled tests. A parameter study is conducted for various physical and mechanical properties. Seat design has been carried out based on the design of experiment (DOE) process with respect to five parameters: seat back collapse angle, joint stiffness between the seat back and seat cushion, headrest stiffness, the clearance between the occupants head and headrest, and friction coefficient of the seat back. An orthogonal array is employed for the DOE. A good design has been found from the results of the experiment. It is found that reductions of the seat back collapse angle and joint stiffness are the most effective for preventing neck injuries.

Design of the occupant protection system for frontal impact using the axiomatic approach

Abstract The functional requirements (FRs) and design equation of a flexible system change in a continuous manner with respect to a variable such as time. An event-driven flexible system is defined as a subcategory of the flexible system in that it changes in a discrete space. A design scenario is developed for the event-driven systems. The design equation for each event should be defined by using the axiomatic approach and the design equations are assembled to form a full design equation. The design equation for each event can be established by sensitivity analysis. In conceptual design, the design order is determined on the basis of the full design equation. Design parameters (DPs) are found to satisfy FRs in sequence. A DP may consist of multiple design variables. In a detailed design, the design variables are determined. The occupant protection system is an event-driven flexible system because the design matrix and its elements change according to the impact speed. The involved devices are designed on the basis of the developed method. FRs at different impact speeds and corresponding DPs are defined. In a detailed design, the full factorial design of experiments is employed for the design variables of the DPs to reduce the injury levels of the occupant. Computer simulation is utilized for evaluation of the injuries. The results are discussed.

A Study on Structural Analysis of Butterfly Valve Components by Pressure Testing of the Industrial Standard

Butterfly valves are widely used in current industry to control the fluid flow. They are used for both on-off and throttling applications involving large flows at relatively low pressure-drop especially in large size pipelines. In this study, we carried out the structure analysis of the butterfly valve components according to pressure testing of the industrial standard. the numerical simulation was performed by using ANSYS Workbench. The reliability of valve is evaluated under the investigation of the strain rate, the leak test and the durability of the valve.

Simulation of Gas Flow in a Microchannel by Lattice Boltzmann Method

In recent years, microflow has become a popular field of interest due to the appearance of microelectromechanical systems (mems). Generally, the navier-stokes equations cannot adequately describe gas flows in the transition and free-molecular regimes. In these regimes, the boltzmann equation of kinetic theory is applied to govern the flows. However, this equation cannot be solved easily, either by analytical techniques or by numerical methods. In this work, the lattice boltzmann method is applied to simulate the two-dimensional isothermal pressure driven microchannel flow. This method is regarded as a numerical approach for solving the boltzmann equation in discrete velocity. We have been applied for rarefied shear-driven and pressure driven flows between parallel plates at knudsen numbers between 0.01 and 1.0. Our numerical results correspond well with those obtained analytically and experimentally. From this study, we may conclude that the lattice boltzmann method is an efficient approach for simulation of microflows.

An orthogonal-array-based design-of-experiments method for designing a vehicle hood and bumper structure

Although the numbers of pedestrian fatalities and injuries are steadily declining worldwide, pedestrian protection is still an important issue. Extensive research has been carried out for pedestrian protection in order to establish appropriate regulations for pedestrian safety. The automobile hoods and bumpers are fairly important for pedestrian protection because pedestrians frequently collide with them during accidents, and they should be designed for the safety of the pedestrians. A new design method for hoods and bumpers is proposed to enhance pedestrian protection by using an orthogonal-array-based design-of-experiments method. Two analysis methods, namely a real experiment and a computer simulation, are utilized to design safe structures of the hood and the bumper. A real experiment is very expensive while computer simulation has modelling imperfections. A design method which uses an experiment and simulation simultaneously is developed. Orthogonal arrays are employed to link the two analyses. The minimum number of experiments is allocated to some rows of an orthogonal array and the simulations are allocated to the rest of the rows to save the cost. Real experiments and computer simulations are conducted for the rows of orthogonal arrays. Design problems are formulated and the orthogonal arrays are directly used to find the design variables by performing the analysis-of-means process in a discrete space. Mathematical error analysis is conducted. Based on the proposed method, a hood and a bumper are designed to protect pedestrians. The results show that the errors are distributed uniformly and a precise design is obtained.

Design of an Automobile Seat With Regulations Using Axiomatic Design

The automobile seat must satisfy various safety regulations for the passenger’s safety. In many design practices, each component is independently designed by concentrating on a single regulation. However, since multiple regulations can be involved in a seat component, there may be a design confliction among the various safety regulations. Therefore, a new design methodology is required to effectively design an automobile seat. The axiomatic approach is employed to consider multiple regulations. The Independence Axiom is used to define the overall flow of the seat design. Functional requirements (FRs) are defined by safety regulations and components of the seat are classified into groups which yield design parameters (DPs). The classification is carried out to keep the independence in the FR-DP relationship. Components in the DP group are determined by using the orthogonal arrays of the design of experiments (DOE). Numerical analyses are utilized to evaluate the safety levels by using a commercial software system for nonlinear transient finite element analysis.© 2005 ASME