DEVELOPMENT OF STRUCTURAL METHODOLOGY FOR MAINTENANCE
AND RELIABILITY ANALYSIS OF AUTOMOBILE SYSTEMS
AJITH TOM JAMES
INDUSTRIAL TRIBOLOGY, MACHINE DYNAMICS AND MAINTENANCE ENGINEERING CENTRE (ITMMEC)
INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2017
Indian Institute of Technology Delhi (IITD), New Delhi, 2017
DEVELOPMENT OF STRUCTURAL
METHODOLOGY FOR MAINTENANCE AND RELIABILITY ANALYSIS OF AUTOMOBILE
SYSTEMS
by
AJITH TOM JAMES
Industrial Tribology, Machine Dynamics and Maintenance Engineering Centre
Submitted
In fulfillment of the requirements of the degree of Doctor of Philosophy
to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2017
This thesis is dedicated to my Parents and Grandparents
i
CERTIFICATE
This is to certify that the thesis titled “Development of Structural Methodology for Maintenance and Reliability Analysis of Automobile Systems” submitted by Mr. Ajith Tom James in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy, is a bonafide work of the researcher, carried out by him under our supervision and guidance. The thesis meets the standards of IIT Delhi for the award of the degree of Ph.D. The work is original and no part of the thesis has been submitted in part or in full by any researcher for the award of the degree of Ph. D.
Dr. O.P. Gandhi Dr. S.G.Deshmukh
Professor (Emeritus) Professor
ITMMEC Department of Mechanical Engineering Indian Institute of Technology Delhi Indian Institute of Technology Delhi
iii
ACKNOWLEDGEMENTS
I thankfully bend my head before the GOD Almighty for showering blessings on me with health, patience, confidence and knowledge to carry out this research work successfully.
This doctoral work is a major milestone in my life that has helped me to think in a different perspective through the incomparable guidance, facilities and academic environment, which I cherished during the period of my research at IIT Delhi. On this journey, I received blessings and selfless supports of many people at different stages of the research work. I owe deepest gratitude to all of them and it would be appropriate to express it at this juncture.
First of all, I would like to express my sincere gratitude to both of my research supervisors., Prof. O. P. Gandhi, Industrial Tribology, Machine Dynamics and Maintenance Engineering Centre, IIT Delhi and Prof. S.G. Deshmukh, Mechanical Engineering Department, IIT Delhi for the knowledge, wisdom, encouragement, guidance, appreciation, and challenges I received from them. I will always remember in my life the kind of academic wisdom they have transferred into me and teaching the lessons of life in personal and professional matters.
I would like to specially thank Prof. J.Bijwe, Head ITMMEC, for her support and encouragement. I am also thankful to my SRC and thank Prof. N. Tandon, Chairman (SRC) and SRC members Prof. V. K. Agarwal (ITMMEC), Prof. P.V. Rao (Department of Mechanical Engineering) and Prof.M.S.Kulkarni. I am also thankful to Prof.R.K.Pandey and Dr.Deepak Kumar, CRC members for their constructive suggestions and feedback throughout my research work.
I am highly indebted to my college management Charutar Vidya Mandal and Chairman Dr. C.L. Patel for putting faith in me and deputing for higher studies. I remember with gratitude the endless support provided by Dr.R.K.Jain, Principal, ADIT in completing my research work. I also thank Dr.Sudhir Gupte, Head, Automobile Department, ADIT and my colleagues and students for giving me the necessary support always.
I am also thankful to the staff at QIP office IIT Delhi for their cooperation during the course of study. I fondly remember the kind of help provided by Mr.Somarajan, Assistant Caretaker, Udaigiri Hostel, other staff and mess workers for their help and support.
I would like to express my sincere thanks to Mr. N.B. Sisodiya, former Divisional Controller, Mr. J. N. Patel, Senior Divisional Mechanical Engineer, Mr. S. J. Patel, Supply officer
iv
and all technicians of divisional workshop of Gujarat State Road Transport Corporation, Nadiad Division for rendering all kind of support and guidance for my case studies. I also would like to specially thank Mr.Asim Dalal, Maintenance Manager, Bhurawala Motors Himmatnagar, Management of ‘Team Professional Garage’ Kottayam and the management and technicians of other garages, where I performed my survey and case studies for my research. I also thank my students Mr. Bhakt Maharana, Mr. Karan Vyas, Mr. Kuldip Ruparel, Mr.Nayan Prajapati, Mr.
Chirag Desai, Mr. Yasheshwar Prajapati, Mr.Udit Mital and Mr.Kushal Desai for sharing their experiences as practicing engineers in automobile and allied industries. I also thank Mr.Tomy Zachariah, Senior Manager, IOCL , for sharing his valuable knowledge during my work.
I have thoroughly enjoyed the company and support of my fellow researchers and seniors of ITMMEC. I express my sincere gratitude towards Dr. Piyush Gupta, Dr. V.N. Ajukumar, Dr.Girish Kumar, Dr. Muhammad Asjad, Dr. M.K. Loganatahan and Dr.Vinod Patel for extending their wholehearted supports at various stages of my research work. I also remember with heartfelt gratitude the generous help and support I have received from my friends namely, Jobin Wilson, Soby Varghese, Deepu Menon, Arun Unnikrishnan, Dr.Sudeep Menon, Dr. K.Sidra., Dr.Shailendra Jha, Dr.Viranchi Pandya, Dr. Samsheerali, Dr.Pravin Prajapati, Dr.Muhammed Safeer, Balasubramaniam, Vidhu Pillai and Reeno. I also would like to thank all my friends of IIT Delhi Malayalee Association for the support and affection I received from them. I would like to express my sincere thanks to following staff members of ITMMEC, Sri. Ashok Kumar, Sri. J.C.
Tuteja, Sri. Avtar Singh, Sri. S.K. Kapoor, Sri. Mohan Singh, Sri. S. K. Barua, Mrs. Malik and Mrs. Beena for their help during this course of work.
I also would like to express my strong feeling of thankfulness to all my teachers who taught me from school to post graduation and always inspired me to become a teacher.
I express my earnest and cordial feelings to my wife Jasmin for her moral support, patience and successful management of home and work during my absence from home for the study at IIT Delhi. From the bottom of my heart I express my ebullient feelings towards my son James and daughter Teresa for their innocence and sacrifice ,while they were deprived of my care and affection as I was away from them during my studies.
Last but not the least; I would like thank all who have helped me directly or indirectly
Ajith Tom James
v
ABSTRACT
Design plays an indispensable role in the development of automobile systems from maintenance, and reliability consideration and so do garage contextual factors during service and maintenance.
Moreover, there was a need for explicit system structure consideration for maintenance and reliability. In view of this, the research work in this thesis aimed and developed structural methodology for maintenance and reliability analysis of automobile systems. The thesis developed four aspects under maintenance and reliability for automobile systems from structural consideration that are: Fault diagnosis, Disassemblability and its index, Assessment of failures due to maintenance errors, and Failure knowledge modeling. The thesis is organized in nine chapters.
Chapter 1; ‘Introduction’, includes motivation of the work and how the thesis has been organized.
Literature review and Problem Formulation are described in Chapter 2, while in Chapter 3, Structural methodology for maintenance and reliability is presented. A methodology for fault diagnosis of automobile systems based on a systems structure approach using digraph model was presented in Chapter 4 for modeling the interrelationships among input and out parameters, including system and component failures. The methodology is general and applicable to any automobile systems, including with feedback and feedforward controls. The methodology is applied to Hydraulic Power Steering for illustration. This methodology is useful for service personnel in efficient and effective detection of faults.
Chapter 5 dealt with disassemblability and its index. Under disassemblability, its understanding and how to improve are elaborated. Later, a system structure approach of graph theory and matrix approach is developed for quantifying disassemblability of automobile systems that models the identified disassemblability factors and their interactions /interrelationships in terms of a disassemblability index. The index is a measure of easiness in disassembly. It guides in evaluation
vi
of the measures implemented at the design. A case study of disassembly of two gearbox models is conducted to validate the methodology. The methodology will be helpful in identifying the design and garage contextual factors that can vitally influence disassembly.
Occurrences of maintenance errors will induce failures and even adversely affect the safety of automobiles. Moreover, the reputation and goodwill of the maintenance service providers are also at stake. This thesis attempted to demonstrate the initiation and propagation of maintenance error through Event Tree Diagram (ETD). Further, the concept of Fishbone diagram is extended for the identification of maintenance error causes and sub-causes. A structural methodology of Fuzzy Cognitive Maps (FCMs) is developed for modelling the interrelationship among various maintenance error causes and assesses the severity of failures due to these. The applicability of the methodology is demonstrated through an example of bus engine maintenance.
When the automobiles are subjected to maintenance due to system or component failures, lot many information pertaining to the failures can be gathered. It would be advantageous, if the failure information gathering is explicit and structured. This information can be shared among OEMs/automobile designers, who can implement design changes based on the failure information of the predecessor components. Apart from these, this will help the maintenance service providers in fault detection and performance of the suitable maintenance actions. A failure coding scheme is suggested in Chapter 7 of this thesis for coding various entities in the failure knowledge and a structural methodology of Ontology is applied for its structuring and representation. The Ontology model developed is populated through case studies.
Chapter 8 presented utility of this research work and its implementation, while conclusions, contributions, limitation and scope for future work are given in the last chapter, i.e. Chapter 9.
vii
The work presented in this thesis is useful to designers and practicing maintenance personnel to analyze essential aspects concerning design of automobile systems and garage contextual factors that govern the maintenance and reliability of automobiles.
Keywords: Automobile systems, System structure, Fault diagnosis, Disassemblability, Maintenance errors, Failure knowledge.
viii
सार
डिजाइन रखरखाव, और डवश्वसनीयता पर डवचार से ऑटोमोबाइल डसस्टम के डवकास में अडनवायय भूडमका डनभाता है और सेवा
और रखरखाव के दौरान गैरेज प्रासंडगक कारक भी करता है। इसके अलावा, रखरखाव और डवश्वसनीयता के डलए सुस्पष्ट डसस्टम संरचना की आवश्यकता थी। इसे देखते हुए, इस थीडसस में अनुसंधान कायय ऑटोमोबाइल डसस्टम के रखरखाव और डवश्वसनीयता
डवश्लेषण के डलए संरचनात्मक पद्धडत को लडित और डवकडसत डकया है। थीडसस ने संरचनात्मक डवचार से ऑटोमोबाइल डसस्टम के
डलए रखरखाव और डवश्वसनीयता के तहत चार पहलुओं को डवकडसत डकया है: फॉल्ट िायग्नोडसस, डिसाइसेडबलडबडलटी और इसके
इंिेक्स, रखरखाव की त्रुडटयों के कारण असफलताओं का आकलन, और डवफलता ज्ञान मॉिडलंग। थीडसस को नौ अध्यायों में व्यवडस्थत डकया गया है।
अध्याय 1; 'पररचय' में, काम की प्रेरणा और कैसे थीडसस का आयोजन डकया गया है साडहत्य की समीिा और समस्या तैयार करने के
अध्याय 2 में वडणयत है, जबडक अध्याय 3 में, रखरखाव और डवश्वसनीयता के डलए संरचनात्मक पद्धडत प्रस्तुत की गई है। डसस्टम और घटक डवफलताओं सडहत इनपुट और आउट पैरामीटर के बीच अंतर संबंधों को मॉिडलंग के डलए अध्याय 4 में डिफ्रैप्चर मॉिल का
इस्तेमाल करते हुए डसस्टम संरचना दृडष्टकोण पर आधाररत ऑटोमोबाइल डसस्टम के दोष डनदान के डलए एक पद्धडत। काययप्रणाली
सामान्य और डकसी ऑटोमोबाइल डसस्टम पर लागू होती है, डजनमें फीिबैक और फीिववयिय डनयंत्रण शाडमल होते हैं। उदाहरण के डलए हाइड्रोडलक पावर स्टीयररंग पर काययप्रणाली लागू होती है। यह काययप्रणाली दोडषयों के कुशल और प्रभावी पहचान में सेवा कडमययों के
डलए उपयोगी है। अध्याय 5 में असंबद्धता और इसके सूचकांक के साथ डनपटा गया। असमानता के तहत, इसकी समझ और सुधार कैसे
डकया जाता है । बाद में, ग्राफ डसद्धांत और मैडिक्स दृडष्टकोण की एक प्रणाली संरचना दृडष्टकोण ऑटोमोबाइल डसस्टम के
डिसएसेडबलडबडलटी को मापने के डलए डवकडसत डकया गया है, जो एक डिससेंडबलडबडलटी इंिेक्स के संदभय में पहचाने गए
डिसएसेबडबडलटी कारक और उनके इंटरैक्शन / अंतसंबंधों के मॉिल हैं। सूचकांक डदससेंबली में सुगमता का एक उपाय है। यह डिजाइन
में लागू उपायों के मूल्यांकन में मागयदडशयका पद्धडत को मान्य करने के डलए दो डगयरबॉक्स मॉिल के डवस्फोट का एक केस स्टिी आयोडजत
ix
डकया जाता है। डिजाइन और गेराज प्रासंडगक कारक की पहचान करने में पद्धडत उपयोगी होगी जो डक असंतुष्ट रूप से प्रभाडवत कर सकती
हैं।
रखरखाव त्रुडटयों की घटनाएं डवफलताओं को प्रेररत करती हैं और यहां तक डक ऑटोमोबाइल की सुरिा को भी प्रडतकूल रूप से प्रभाडवत करती है इसके अलावा, रखरखाव सेवा प्रदाताओं की प्रडतष्ठा और सद्भावना भी दांव पर लगा रहे हैं। इस थीडसस ने इवेंट िी आरेख (ईटीिी) के माध्यम से रखरखाव त्रुडट के दीिा और प्रचार का प्रदशयन करने का प्रयास डकया। इसके अलावा, डफशबोन आरेख की
अवधारणा को रखरखाव त्रुडट कारणों और उप-कारणों की पहचान के डलए बढाया गया है। फजी संज्ञानात्मक मानडचत्र (एफसीएम) की
एक संरचनात्मक पद्धडत को डवडभन्न रखरखाव त्रुडट कारणों के बीच अंतराल के मॉिडलंग के डलए डवकडसत डकया गया है और इन वजहों
से डवफलताओं की गंभीरता का आकलन डकया गया है। काययप्रणाली की प्रयोज्यता को बस इंजन रख-रखाव के उदाहरण के माध्यम से
प्रदडशयत डकया गया है।
जब ऑटोमोबाइल को डसस्टम या घटक असफलताओं के कारण रखरखाव का सामना करना पड़ता है, डवफलताओं से संबंडधत बहुत सी जानकारी इकट्ठी हो सकती है। यह लाभप्रद होगा, अगर डवफलता की जानकारी एकत्र करना स्पष्ट और संरडचत है। यह जानकारी
ओईएम / ऑटोमोबाइल डिजाइनरों के बीच साझा की जा सकती है, जो पूवयवतती घटकों की डवफलता की जानकारी के आधार पर डिजाइन पररवतयन लागू कर सकती हैं। इन के अलावा, यह रखरखाव सेवा प्रदाताओं को गलती का पता लगाने और उपयुक्त रखरखाव कायों के प्रदशयन में मदद डमलेगी। डवफलता कोडिंग योजना का सुझाव है डक इस थीडसस के अध्याय 7 में डवफलता के ज्ञान में डवडभन्न संस्थाओं को कोडिंग के डलए सुझाव डदया गया है और इसकी संरचना और प्रडतडनडधत्व के डलए एक तंडत्रकी पद्धडत का उपयोग डकया
जाता है। डवकडसत ओटटालोजी मॉिल मामले के अध्ययन के माध्यम से आबादी है।
अध्याय 8 ने इस शोध कायय की कायायन्वयन और इसकी कायायन्वयन, जबडक भडवष्य के कायों के डलए डनष्कषय, योगदान, सीमा और
गुंजाइश डपछले अध्याय में दी गई है, अथायत अध्याय 9
x
इस थीडसस में प्रस्तुत कायय ऑटोमोबाइल प्रणाली के रखरखाव और डवश्वसनीयता को डनयंडत्रत करने वाले ऑटोमोबाइल डसस्टम और गेराज प्रासंडगक कारकों के डिजाइन से संबंडधत आवश्यक पहलुओं का डवश्लेषण करने के डलए डिजाइनरों और रखरखाव कडमययों के
डलए उपयोगी है।
कीवर्ड: ऑटोमोबाइल सिस्टम, सिस्टम िंरचना, दोष सनदान, सििएिेमेसलसबसलटी, रखरखाव त्रुसटयां, सवफलता ज्ञान।
xi
CONTENTS
Certificate i
Acknowledgements iii
Abstract v
Contents xi
List of Figures xv
List of Tables xvii
Nomenclature xix
Abbreviations xxi
Chapter 1 Introduction 1
1.1 Motivation 8
1.2 Thesis organization 9
Chapter 2 Literature Review and Problem Formulation 11
2.1 Fault diagnosis 11
2.2 Disassemblability and its evaluation 17
2.3 Failures due to maintenance errors 24
2.4 Failure knowledge modeling 30
2.5 Models and procedures employed 35
2.5.1Graph and digraph models 36
2.5.2 Fuzzy cognitive maps 37
2.5.3 Ontological modeling 38
2.5.4 Analytic hierarchy process 39
2.5.5 Event tree diagram 40
2.5.6 Fishbone diagram 40
2.6 Research gaps 40
2.7 Problem formulation and research objectives 2.8
43
2.8 Research activities 43
xii
2.9 Research deliverables 46
Chapter 3 Structural Methodology for Maintenance and Reliability 47
3.1 Understanding automobile systems 47
3.2 System structural model 50
3.2.1 Considered maintenance and reliability aspects and their structural models
51
3.3 Structural methodology 52
3.4 Background and supportive Inputs for chosen models 55
3.4.1 Digraph Model 55
3.4.2 Fuzzy cognitive map (FCM) model 58
3.4.2.1 Structural modeling using FCM 59
3.4.3 Ontological Modeling
3.4.1 Structural modeling using FCM
62 3.4.3.1 Structural modeling using Ontology 63 3.4.4 Analytic Hierarchy Process (AHP) 64 3.4.4.1 Procedure of AHP for evaluating weightages 66
3.5 Conclusions 67
Chapter 4 Fault Diagnosis 68
4.1 Overview of Lapp and Powers methodology 68
4.2 Extension of methodology to automobile Systems 70 4.3 Application to hydraulic power steering system 76 4.4 Observations and comments on the proposed approach 92
4.5 Applications of the approach 93
4.6 Conclusions 94
Chapter 5 Disassemblability and its Index 95
5.1 Disassemblability 95
5.1.1Need for disassemblability evaluation 97 5.2 Development of disassemblability index 99
5.3 Disassemblability factors 99
5.3.1 System Design (SD) 101
5.3.2 Garage Policy (GP) 102
5.3.3 Service Support System (SSS) 103
xiii
5.3.4 Personnel Resources (PR) 104
5.3.5 Servicing Ambience (SA) 106
5.4 Disassemblability modeling 108
5.4.1 Matrix representation 111
5.5 Disassemblability evaluation 113
5.5.1 Quantification of diagonal elements 113
5.5.2 Quantification of off-diagonal elements 121
5.5.3 Disassemblability indices 121
5.5.3.1 Disassemblability index 121
5.5.3.2 IDI, DIR and DTR 122
5.5.3.5 Sensitivity analysis 123
5.6 Steps for disassemblability evaluation 123
5.7 Case study 124
5.8 Observations and Comments 136
5.9 Conclusions 137
Chapter 6 Failures Due to Maintenance Errors 139
6.1 Typical maintenance errors 139
6.1.1 Initiation and propagation of maintenance error 141
6.2 Causes of maintenance errors 144
6.2.1 Fishbone diagram for maintenance error causes 146 6.2.1.1 Inspection and diagnostics (ID) 151 6.2.1.2 Maintenance procedures (MP) 152 6.2.1.3 System and maintenance tool (SMT) 154 6.2.1.4 Personnel elements (PE) 155 6.2.1.5 Parts, fasteners and consumables (PFC) 156 6.2.1.6 Garage ambience (GA) 156
6.3 Fuzzy cognitive map modeling 157
6.3.1 FCM inference mechanism 160
xiv
6.4 FCM extension for automobile failures 160
6.4.1 Sensitivity analysis 163
6.4.2 Steps for application of FCM methodology 164
6.5 Case Study 166
6.5.1 Observations and comments 174
6.6 Conclusions 175
Chapter 7 Failure Knowledge Modeling 176
7.1 Automobile failure knowledge 176
7.2 Ontological modeling and its extension to automobile system failures
178
7.2.1 Overview of ontological model 178
7.2.2 Extension to automobile system failures 180
7.2.2.1 Development of concepts 180
7.2.2.2 Failure codes and coding scheme 182 7.2.2.3 Populating the ontological model 192
7.3 Conclusions 197
Chapter 8 Utility of the Work and Implementation 199
8.1 Utility 199
8.2 Implementation 203
Chapter 9 Conclusions, Contributions, Limitations and Scope for Future Work
206
9.1 Conclusions 209
9.2 Contributions 210
9.3 Limitations of work 212
9.4 Scope for future work 213
9.5 Concluding remarks 214
References 215
Appendix A - Generalized Operators for Control Loops:
Feedback and Feedforward
A1-A3 Appendix B - Garage survey to identify of disassemblability
factors
B1-B7 Appendix C - Publications based on research C1 Appendix D – Permissions from publishers D1-D2 BIO-DATA
xv
LIST OF FIGURES
Figure No. Title Page No.
Figure 3.1 Hierarchical structure of an automobile system 49
Figure 3.2 Transmission system 49
Figure 3.3 Structural models for maintenance and reliability analysis 53 Figure 3.4 A framework of structural methodology for the research work 54 Figure 3.5 A simple Digraph
Digraph and its adjacency matrix
55
Figure 3.6 Digraph and its equivalent matrix 56
Figure 3.7 A general FCM structure 60
Figure 3.8 Concepts and their relations in ontology 64
Figure 3.9 Hierarchical structure of AHP 66
Figure 4.1 Interrelationship between input and output parameters and digraph model for pump 69
Figure 4.2 Line diagram of hydraulic power steering system 78
Figure 4.3 Line diagram and Input-Out parameter model of vane pump 79 Figure 4.4 Figure 4.4 (a),(b) and (c) Line diagram, Input-Output and digraph models of sub-
system/assembly/component
81-83
Figure 4.5 System digraph of hydraulic power steering 84
Figure 4.6 First step of fault tree development for event: ‘Loss of power’, i.e. ‘P2 (-1) 86
Figure 4.7 Second step of fault tree development 88
Figure 4.8 Sub-Fault tree for low coolant flow rate 89
Figure 4.9 Sub -Fault tree for very low coolant pressure 89
Figure 4.10 Fault tree for ‘Loss of power’ 91
Figure 5.1 Automobile system disassemblability digraph 110
Figure 5.2 Disassemblability digraph of the gearboxes ‘A’ and ‘B’ 132 Figure 6.1 Event tree diagram for ABS due to incorrect connection of hydraulic lines 144 Figure 6.2 Fishbone diagram of automobile maintenance error causes and sub-causes 151
Figure 6.3 A general fuzzy cognitive map 158
Figure 6.4 FCM of engine failure severity due to maintenance errors 168
xvi
Figure 6.5 FCM for sensitivity analysis 172
Figure 7.1 Failure coding scheme for automobile systems 184
Figure 7.2 Frequency of failure symptoms of buses of state transport 186 Figure 7.3 Ontological framework model for automobile failure knowledge 190
Figure 7.4 Failure code scheme for case 1 193
Figure 7.5 Failure code scheme for case 2 195
Figure 7.6 Failure code scheme for case 3 196
Figure 8.1 Implementation of the research work 203
Figure 8.2 Implementation of methodology for fault diagnosis of braking system of truck 204
Figure 9.1 Flowchart of the research work 207
Figure A1 Operator for negative feedback loop A2
Figure A2 Operator for negative feedforward loop A3
Figure B1 Frequency distribution of responses B4
Figure B2 Frequency distribution of garage contextual factors B5
xvii
LIST OF TABLES
Table No. Title Page No.
Table 2.1 Research activities and steps for achieving research objectives 45 Table 3.1 Identification of structural models for maintenance and reliability aspects 51 Table 3.2 Assigning value to pair wise comparisons of matrix elements 66
Table 3.3 Random index values 67
Table 5.1 Factors and sub-factors of disassemblability for automobile systems 107 Table 5.2 Assigning value to sub-factors of system design (𝐷1) 115-116 Table 5.3 Assigning value to sub-factors of garage policy (𝐷2) 117 Table 5.4 Assigning value to sub-factors of service support system (𝐷3) 118 Table 5.5 Assigning value to sub-factors of personnel resources (𝐷4) 119 Table 5.6 Assigning value to sub-factors of servicing ambience (𝐷5) 120 Table 5.7 Degree of influence among disassemblability factors 121 Table 5.8 Normalized relative weights of disassemblability factors 130 Table 5.9 Evaluation of the disassemblability factor‘𝐷1’specific to gearbox A and B 131 Table 5.10 Evaluation of the disassemblability factors 𝐷2,𝐷3,𝐷4and 𝐷5 common for
the gearboxes A and B. 131
Table 5.11 Result of sensitivity analysis 136
Table 6.1 Typical maintenance errors in automobiles 139
Table 6.2 Typical cause categories of schemes for Fishbone diagram 147
Table 6.3 Cause –Scheme relationship matrix 148
Table 6.4 Correlation of established causes of schemes with causes identified for the
scheme of automobile maintenance 149
Table 6.5 Maintenance error causes for automobile system 150
Table 6.6 Linguistic variable and corresponding numerical values 162 Table 6.7 Target concept values for different input concept vectors 170 Table 6.8 Target concept values for different input concept vectors for sensitivity
analysis 173
Table 7.1 Features of ontological modeling 179
xviii
Table 7.2 Main concepts and properties 181
Table 7.3 Relations between the concepts, their explanation and terminology 181
Table 7.4 Coding scheme for systems of automobiles 181
Table 7.5 Coding scheme for sub-systems and components of the engine 184 Table 7.6 Coding scheme for functions of the automobile system at hierarchical
level 185
Table 7.7 Coding scheme for failure symptoms 186
Table 7.8 Coding scheme for diagnosis 187
Table 7.9 Coding scheme for failure causes 188
Table 7.10 Coding scheme for maintenance actions 189
Table 8.1 Utility of the work 201
Table 9.1 Quantum of work 207
Table B1 Questionnaire for identification of disassemblability factors in automobile maintenance
B2-B3
Table B2 Survey Results B4
Table B3 Personal opinion on garage contextual factors B6
xix
NOMENCLATURE
AMD Equivalent Matrix of the Digraph
AWij Adjacency Weight Matrix of Weightages of Influences among Concepts ‘i’ and ‘j’
aij Relative importance of element ‘i’ with respect to ‘j’
aim mth assembly of ith sub-system C (t) Initial concept matrix
Ci(t) Activation level of the ith concept at time step ‘t’
Ci(t+1) The updated value of the concept at time‘t+1’
ckim kth component of mth assembly
Di ith disassemblability factor or its value
Dij ‘jth’ sub-factor of the ‘ith’ disassemblability factor E Set of directed edges
eij Degree of influence among disassemblability factors ‘i' and ‘j’
f’ Transformation function
Gd Automobile system disassemblability digraph GMi Geometric mean of ith row
HD Disassemblability matrix
HD1 Equivalent matrix of disassemblability digraph K1 Pairwise comparison square matrix of ‘N’ elements
M Mass flow rate
N Number of disassemblability factors/elements
P Pressure
PD Equivalent matrix of digraph with ‘N’ elements
Per Permanent
Pi Pressure at the ith stream Pj Pressure at the jth stream S System of automobile
xx
Sij Score assigned to ‘jth’ sub-factor of the ‘ith’ disassemblability factor si ith sub-system of automobile
T Temperature
V Set of nodes representing disassemblability factors Wi Weightage of ‘ith’ disassemblability factor
Wij Weight of influence between concepts ‘i’ and ‘j’
WEi Normalized weight of each element λmax Maximum eigenvalue
xxi
ABBREVIATIONS
AHP Analytic Hierarchy Process
CI Consistency Index
CR Consistency Ratio
DI Disassemblability Index
DIR Disassemblability Index Ratio DTC Diagnostic Trouble Codes
DTR Disassembly Time Ratio
ETA Event Tree Analysis
ETD Event Tree Diagram
FCM Fuzzy Cognitive Maps
FES Failure Effect Spectrum
FTA Fault Tree Analysis
GA Garage Ambience
GP Garage Policy
ID Inspection and Diagnostics
IE Initiating Event
IT Information Technology
KM Knowledge Management
KMS Knowledge Management System
MHE Material Handling Equipment MIL-HDBK Military Handbook
MP Maintenance Procedures
xxii
MTM Method Time Measurement
MTTR Mean Time To Repair
OBD On-board Diagnostics
PM Preventive Maintenance
PMS Periodic Maintenance Service
PMTS Pre-determined Motion Time Standards
PE Personnel Elements
PFC Parts, Fasteners and Consumables PPE Personal Protective Equipment
PR Personnel Resources
RI Random Index
SA Servicing Ambience
SAP System Analyses and Programme
SD System Design
SDF System Disassemblability Function
SM Structural Modeling
SMT System and Maintenance Tools
SSS Service Support System
