Development of explicit finite difference-based simulation system for impact studies

Development of numerical method-based simulation systems is presented. Two types of system development are shown. The former system is developed using conventional structured programming technique. The system incorporates a classical FD hydrocode. The latter system incorporates object-oriented design concept and numerous novel elements are included. Two explicit finite difference models for large deformation of several material characteristics are developed. The models are capable of handling impulsive and constant load, impact and gravitational force, etc. Their capabilities of handling relatively complex shapes, which are not possible to deal with using classical FD models, are shown and discussed. A robust algorithm is suggested to describe general stress-strain relationship, ranging from elastic-perfecdy plastic to multiple elastic modulii and plastic modulii with or without strain rate sensitivity. Hysteresis and Bauschinger effects are included as well. Development of contact-impact treatments is presented. Three novel contact elements are designed, developed and validated. Node-node and node-element contacts are formulated with all the elements developed. The contact-impact treatments include a novel method in handling potential voids and overlaps at contact intersection. Rigid Coulomb’s friction model is incorporated to handle sliding conditions. Formulation of a novel revolute joint element is illustrated and several possible methods are suggested for handling bending limits. Incorporation of resistive moment and damping effects are presented. The numerical stability of the revolute element is discussed and a stability criterion is proposed. The latter simulation system is used to model an idealised human body. Information from literatures, such as height and weight ratio of human segments, and resistive moment of human joints, is incorporated into the human model. Simulations are carried out according to a 2k factorial design of experiment to find the main effect(s) contributed to human head/brain injury when subjected to frontal collision. A simple motorcycle model based on Malaysian KRISS 110 motorcycle is developed as well. The human model is successfully integrated into the motorcycle model. Possibility of solving such model with the developed simulation system is studied

Fuzzy Rules Optimization in Fuzzy Expert System for Machinability Data Selection: Genetic Algorithms Approach

Machinability data selection is complex and cannot be easily formulated by any mathematical model to meet design specification. Fuzzy logic is a good approach to solve such problems. Fuzzy rules optimization is always a problems for a complex fuzzy rules from more than 10 thousand combinations. (Wong et aL 1997) developed fuzzy models for machinability data selection. There are more than 2 x 1029 possible sets of rules for each model. Situation would be more complicated if further increase the number of inputs and/or outputs. The fuzzy rules were selected by trial and error and intuition in reference (Wong et aL 1997). Genetic optimization is suggested in this paper to further optimizing the fuzzy rules optimization with genetic algorithms has been developed. Weighted centroid method is used for output defuzzi fication to save processing time. Comparisons between the results of the new models and the previously published literatures are made

Computational simulation of frontal impact of motorcycle telescopic fork

This paper presents modelling aspects of a high fidelity finite element model of a motorcycle telescopic fork. For validation purpose, a series of impact tests of which a frontal impact load imposed on the individual fork by a rigid striker was conducted using factorial experiment approach. The model was then used to simulate all the impacts accordingly. The outcomes were evaluated in terms of permanent deformations of the fork, energy dissipated in the impact, and the velocity and displacement time histories of the striker. The overall performance and sensitivity of the model was also assessed using the factorial analysis. The deviations of time histories data were quantified by mean error, mean absolute error and root mean square error. The key responses of the fork were found to be successfully simulated and compared well to the test results. The computed largest value among the respective metrics over the total errors was 6.2% of which corresponding to the root mean square error of the displacement time histories data, whereas others were less than 3%. It is thus concluded that the fork model has been successfully validated and the modelling methods has been established. Recommendations for improvements were also given in the paper

Bending analysis of a functionally graded rotating disk based on the first order shear deformation theory

The theoretical formulation for bending analysis of functionally graded (FG) rotating disks based on first order shear deformation theory (FSDT) is presented. The material properties of the disk are assumed to be graded in the radial direction by a power law distribution of volume fractions of the constituents. New set of equilibrium equations with small deflections are developed. A semi-analytical solution for displacement field is given under three types of boundary conditions applied for solid and annular disks. Results are verified with known results reported in the literature. Also, mechanical responses are compared between homogeneous and FG disks. It is found that the stress couple resultants in a FG solid disk are less than the stress resultants in full-ceramic and full-metal disk. It is observed that the vertical displacements for FG mounted disk with free condition at the outer surface do not occur between the vertical displacements of the full-metal and full-ceramic disk. More specifically, the vertical displacement in a FG mounted disk with free condition at the outer surface can even be greater than vertical displacement in a full-metal disk. It can be concluded from this work that the gradation of the constitutive components is a significant parameter that can influence the mechanical responses of FG disks

Fatality prediction model for motorcycle accidents in Malaysia

This paper involves building a fatality predictive model for motorcycle accidents data in Malaysia. The number of registered motorcycles in Malaysia has increased four-fold compared to the last 20 years. Thus, the motorcycle accidents rate and fatality rates among riders and pillion in Malaysia has also increased dramatically. However, results show that when taken into account the numbers of fatalities per 10,000 registered motorcycles, the fatality rate shows a decreasing trend starting from 1996 onwards. The motorcycle accident data for the period of 1996 to 2010 was analyzed using Smeed’s Law and regression method. The results show that regression method approach gives better estimates of fatality rate than Smeed’s equation

Identification of traffic and roadway variables affecting safe motorcycling along urban roads

In Malaysia, motorcycles represented 45% of all registered vehicles. Alarmingly, motorcyclists comprise 65% of total road deaths. One major reason being that these vulnerable road users get entangled with other mixed vehicles. It is appreciated that roadway design guidelines are based on the characteristics of drivers/automobiles and not riders/motorcycles. Thus, motorcyclists are expected to occupy the dynamically changing space that is available along the roadway. An effective engineering measure to tackle motorcycle safety problems in mixed traffic conditions would be to segregate the motorcycles exclusively. However, this measure is not appropriate for urban roads. One practical approach to address motorcycling safety along urban roads is to identify the traffic and road environment variables that affects safe motorcycling. This list of variables can be used to check the safe motorcycling status along segments of urban roads. The variables relating to bicyclist’s perception on the roadway segments were adopted for the variables affecting motorcycling safety along urban roads. To corroborate the adopted variables factors with the actual perception of motorcyclist, the questionnaires related to the variables affecting safe motorcycling were responded by 137 motorcyclists. The variables were identified to be pavement condition, on-street parking, traffic volume, divided/undivided roadway, left-side kerb clearance, lane width, and travelling speed. To further understand these seven variables from the aspect of motorcyclist perceptions, 14 short clips were presented to 483 motorcyclists who rated each clip based on their perception of safe motorcycling. Results found that the odds of feeling unsafe riding on bad pavement is 61.5 times greater than the odds of riding on good pavement. The odds of unsafe motorcycling along roads with on-street parking is 43.2 times higher than without on- street parking. Overall, it infers that the maintenance of road pavement conditions must be of high priority to the local authorities followed by issues of on-street parking along urban links

General Strategies in Developing Alloy Steel Fuzzy Model for Machinability Data Selection of Turning Process

In this paper, several fuzzy models have been proposed for machinability data selection of turning process of alloy steel. The selection of the machinability data is a crucial task, and normally done by the skilled machinists. Thus, fuzzy models-have been suggested for predicting the optimum machinability data, which are cutting speed and feed rate. These fuzzy models are developed based on the relationship of two-input (material hardness and depth of cut) and two-utput (cutting speed and feed rate). A few general strategies in developing fuzzy models are presented and discussed in this paper. Generally, there are three different strategies that are suggested in this paper. The objective of implementing these strategies is to simplify the process of fuzzy model development. The predicted cutting speed and feed rate are compared with the data obtained from the Machining Data Handbook (Metcut Research Associate 1980) and a good correlation has been shown throughout the comparison

Quick cost estimation model for early order stage

On time quotation and accurate cost estimate are two important factors influencing the ability of a company to sustain its business operation. Failure to fulfill requests for quotation can severely effect its business survival. Late and uncompetitive quotations will result in lost of customers. It is vital for manufacturing companies to generate cost estimates quickly and accurately otherwise they might either loose their business or not make sufficient profit. Cost estimation process requires good knowledge in the structure of the part and its manufacturing processes. Cost estimation can be done with a high degree of accuracy but it takes too long and if it is done in a short period of time the accuracy is usually quite poor. Generating detailed process plan requires a substantial amount of time and data. Unfortunately, not all necessary information is available during the costing stage. This paper shows the possibility of developing part cost estimate without having to construct its detail process plan. It presents a model for estimating part process cost which allows a cost estimate to be generated quickly with certain degree of accuracy by utilizing parametric techniques and part feature representation

Workpiece surface temperature for in-process surface roughness prediction using response surface methodology

As manufacturing technology has been moving to the stage of full automation over the years, one of the fundamental requirements is the ability to accurately predict the output performance of machining processes. The focus of present study is to predict surface roughness using the workpiece surface temperature of a turning workpiece with the aid of an infrared temperature sensor. Relationship between the workpiece surface temperature and the cutting parameters and also between the surface roughness and cutting parameters were found out for indirect measurement of surface roughness through the surface temperature of the workpiece. A 33 full factorial design was used in order to get the output data uniformly distributed all over the ranges of the input parameters. Response Surface Method (RSM) and analysis of variance (ANOVA) are used to get the relation between different response variables (Surface roughness and workpiece surface temperature) and the input parameters (speed, feed and depth of cut). Based on variance analysis for the second order RSM model, most influential design variable is feed rate and depth of cut on surface roughness and workpiece surface temperature respectively and the experimental results show that the workpiece surface temperature can be sensed and used effectively as an indicator of the cutting performance