Tối ưu hóa thời hạn bảo dưỡng sửa chữa bộ phận chạy đầu máy diesel khai thác trong điều kiện việt nam tt tiếng anh

MINISTRY OF EDUCSTION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATION VÕ TRỌNG CANG OPTIMIZING THE REPAIR CYCLE OF THE RUNNING GEAR ON DIESEL LOCOMOTIVES OPERATED IN VIETNAMESE CONDITIONS Major: Mechanical dynamic engineering Code: 52 01 16 Minor: Exploitation and maintenance of locomotives, wagons SUMMARY OF DISSERTATION HA NOI – 10/2020 This thesis is made at : UNIVERSITY OF TRANSPORT AND COMMUNICATION Professional adviser(s): Prof Dr Đỗ Đức Tuấn Assoc.Prof Dr Đỗ Việt Dũng Reviewer 1: Reviewer 2: Reviewer 3: This thesis will be presented to the Thesis Committee of University of Transport and Communication At … the day month year 20 This thesis can be found in the library : - National Library of Viet Nam - The Library of University of Transport and Communication INTRODUCTION The reason for choosing the topic Currently, Vietnam's railway system is using a total of 282 diesel locomotives (of which 259 are in use), including 13 types with a capacity of 500 to 2,000 horsepower, originating from countries The locomotive maintenance and repair cycle system is still used by the VNR as recommended by the manufacturer, with certain adjustments However, these adjustments have almost no fundamental changes, only based on pure use experience, not yet derived from in-depth studies and not have a solid scientific basis Therefore, the completion of the system of maintenance and repair cycles (MRC) for locomotives used in the Vietnam's railway system (VNR) in general and the D19E locomotive in particular, taking into account technical factors in the operation and then considering the cost of maintenance and repair is an issue of scientific significance, practice, in line with the world's trends, and a new problem in Vietnam The goal of the subject Application of theory of reliability and theory of optimization to determine the repair cycles for diesel-electric locomotive parts used in VNR considering the gamma percentage life of details and planned repair costs Research subjects Diesel electric locomotive used in Vietnamese railway system This type of locomotive, with superior features compared to diesel hydrolic locomotive, with the number of locomotives in use accounting for 80.31% (208/259), with a total capacity of 86.74% (325,700 /375,500 horsepower), is the main traction source of Vietnam railway transport Research scope The running gear parts, which are important parts on the locomotive, are directly related to the operation and safety of the train, and that have a decisive influence on the commissioning of the locomotive The research content is specifically applied to the running wear of the D19E locomotives used at the Saigon Locomotive Enterprise Research Methods Theorical study Theories of reliability and optimization, set up algorithms, and build corresponding calculation programs Practical research: - Regarding the repair procedures and the locomotives’ parts repair methods are currently applied in the Vietnamese railway industry - Surveying and collecting statistics on wear and tear of parts during use as a basis for determining the optimal maintenance and repair cycle for studied subjects Research content Research on the basis theory to determine the working life of the locomotive’s parts, damaged by wear, and build a calculation program Research the basic theory of optimization of repair cycle system for locomotive’s part taking into account the gamma percentage life and planned repair costs, and develop a calculation program Collecting statistical data on wear and repair costs of D19E diesel locomotive components used at Saigon Locomotive Enterprise under Vietnam Railway Corporation Determine the optimum working life of D19E locomotive components used at Saigon Locomotive Enterprise according to gamma percentage life and planned repair cost Scientific and practical significance - Scientific significance The results of reliability theory, optimal theory have been applied, using Matlab programming language to build programs to calculate the gamma percentage working life of parts due to wear and tear systematic corresponding optimal repair cycle taking into account the costs of planned repairs The calculation programs are general programs, not only used for locomotives and wagons in particular, but also for other mechanical objects in general, with component packaging Complete software and commercialization - Practical significance The calculation results are the basis for reference for the managers and vehicle users to choose the plan suitable to the actual conditions, the harmony between ensuring the reliability in the exploitation process and minimum unit cost for repairs The research results of the thesis are a premise to open up the possibilities for next studies to apply in reality of the Vietnamese railway system, to encourage the managers and scientists, continuity to create conditions for more in-depth and comprehensive research on this issue Research results are also useful references for training in schools in particular and for scientific research in general In addition, the research results are also the basis for reference for the compilation of processes, standards and regulations on maintenance and repair of locomotives in general and D19E locomotives in particular in Vietnamese railway system New contributions of the thesis Collected a large number of statistics on wear and repair costs of running gear parts of 30 D19E diesel-electric locomotives used at Saigon Locomotive Enterprise of the Vietnam Railway Corporation for a period of years, from 2013 to 2017, and use it for research purposes That is also something that Vietnam railways system has not had the conditions to Having built in Matlab programming language a program to calculate the gamma percentage working time and determine the optimal repair cycle for parts working until failure due to worn on locomotives in general and on the running gear of D19E locomotives in particular The program is packaged into complete software with pure Vietnamese interface, friendly, easy to use, suitable for the purpose and content of the research The results received from the program are reliable The calculation software is an integrated program that can be used for all types of locomotives and wagons in Vietnam railways system Not only that, it can also be used for all kinds of equipment, mechanical machinery in general In addition to being used for the content of the thesis, this program (software) is also capable of commercialization Identified the optimal working time (repair cycle) of running gear parts for D19E locomotives used at Saigon Locomotive Enterprise with variants (scenario) according to the gamma-50%, -75%, -80%, -85% and -90% working time with the smallest total unit cost These scenarios are the basis of reference for the managers and vehicle operators to choose the variant that is appropriate to the actual conditions, and the harmony between ensuring reliability in operation and the minimum total unit cost for repairs The research results of the thesis, although are only initial step in the application of reliability theory results and optimal theory to the practical problem of Vietnam in general and Vietnam’s railway transport in particular, have opened up the possibility for further research The research results of the thesis are the reference basis for the compilation of Procedures, Standards, Regulations on maintenance and repair of locomotives in general and D19E locomotives in particular for Vietnam railways system The structure of the Dissertation The thesis includes the Introduction, four chapters of research content, the Conclusion and recommendations and the Appendix CHAPTER OVERVIEW OF REPAIR SYSTEM AND OPTIMIZATION OF THE MACHINE REPAIR CYCLE 1.1 An overview of Vietnamese railway system Currently, Vietnamese railway system has a total of nearly 3,200 km with main lines and 03 sub-lines, including three types of gauge: 1,000 mm; 1,435 mm and cage (1,000 mm and 1,435 mm) [55] The density of Vietnam's railway network in general compared to its population and territorial area is very low: 35,135m / 1,000 inhabitants and 8.125 m / km2 of territory 1.2 Overview of locomotives in the Vietnamese railway system Currently, Vietnam's railway system is managing and using a total of 282 diesel locomotives with 13 types imported from different countries, with a capacity of 500 to 2,000 horsepower, with a total capacity of about 400,000 horsepower, structure speed does not exceed 120km/h [55] 1.3 An overview of the diesel locomotive maintenance and repair system 1.3.1 General concept 1.3.2 Some basic principles for setting maintenance and repair cycle of main components on diesel locomotives The principle of setting a Maintenance and Repair Cycle (MRC) is essentially setting the parts’ dissolution cycle when gaps or wear and other specifications are likely to reach critical values These cycles depend on the wear and tear of the most basic components on the locomotive, which have a decisive influence on its performance such as the diesel engine, powertrain and running gear parts 1.4 Locomotive maintenance and repair system 1.4.1 Overseas locomotive maintenance and repair cycle system 1.4.1.1 Some overseas systems of locomotive MRC 1.4.1.2 Analysis of some overseas systems of locomotive MRC In most developed countries [94, 99, 100], the problem of setting up a MRC system is done by experience-theoretical solution, i.e based on experience in using various types of locomotive, combined with summary results in theory when studying the reliability of some parts or some basic parts on the locomotives For various reasons, in reality, there is no unified system for checking and repairing locomotives In many countries, locomotive's planned repair system is becoming more and more flexible, more flexible with variable and different repair times under different application conditions 1.4.2 System of locomotives maintenance and repair cycle in Vietnam Currently, all the locomotives used in the Vietnam are imported from abroad and the maintenance and repair cycle system is regulated by the manufacturer During the process of using and operating, VNR has made certain adjustments to the MRC system, but these adjustments are only based on pure experience, has not come from in-depth studies and has a solid scientific basis 1.5 Overview of general vehicle repair maintenance cycle optimization Typical works include: maintenance strategy [64, 68]; maintenance optimization [59, 61, 64  67, 70  72, 75, 76, 78, 79, 85] After finding out that, it is not feasible to apply the above optimization and maintenance methods to the current Vietnamese conditions 1.6 Overview of locomotive maintenance cycle optimization 1.6.1 Studies abroad There have been many works related to this field, in which some typical works are ranked in chronological order as follows: [58], [62], [74], [84], [91 98] In the above works, especially the works of author Gorxki A.V., Vorobiev A.A and Puzankov A.D [94], [97] 1.6.2 Researches in Vietnam In Vietnam, in recent years, there have also been some initial single studies on determining the working time of parts on the locomotive through researches on wear and optimization of the repair cycle taking into account gamma percentage working time and repair costs, as shown in [33], [35], [36], [39], [43], [45  49], [51  54], [69], [87], [89], [90] In summary, the locomotive repair cycle system can be classified into two categories: + Traditional repair cycle system: purely technically set up, that is, considering only damage in general and wear in particular of parts; only concern about reliability and availability of machinery and equipment, regardless of cost and independent of the production process; + Advanced repair cycle system: a traditional repair cycle system is completed with different criteria, in which both general damage and wear in particular are considered and repair costs This system is quite diverse in form but has the same characteristics that it must ensure the reliability, the willingness to work of machines and equipment and ensure the minimum cost Currently, there are two methods of optimizing MRC for locomotives that are applicable to Vietnamese conditions: Optimizing the MRC system at a given level of confidence good parametric reliability, that is, taking into account planned repair costs and gamma percentage life; Optimizing the lowest cost repair cycle system for planned repairs and unscheduled repairs Among the two methods above, the first one is more feasible, so the researcher has selected and proposed a method for optimizing the MRC of the locomotive considering the gamma percentage life and planned repair cost, aiming to step by step approach the problem that has been raised Conclusion of Chapter 1 The planned maintenance and repair cycle (MRC) of a locomotive depends on the wear and tear of main components such as diesel engine, transmission system and running gear parts In developed countries still using the traditional maintenance system, but is being perfected in many different directions, including optimization of the repair cycle according to cost and step-by-step condition based maintenance The systems of MRC for locomotives in Vietnam are still the traditional repair system, mainly based on the manufacturer's regulation Completing these systems in the direction of optimization with cost consideration is still completely new and selected as the research content of this thesis CHAPTER BASIS OF DETERMINATION OF WORK TIME OF THE PARTS ON THE LOCOMOTIVE UNTIL DAMAGE BY WEAR AND BUILD A CALCULATION PROGRAM 2.1 Introduction of the running gear of the diesel electric locomotive D19E The overall structure of the D19E locomotive is shown in figure 2.1 [23] The overall structure of the D19E bogie is shown in figure 2.2 [23] Figure 2.1 Overall structure of the D19E locomotive Figure 2.2 Overall structure of the D19E bogie Fig 2.2: Crossbeams along edge; Wheel rim lubrication box; Wheel; Rubber springs; Pull bar; electric traction motor; Hand brake; Brake cylinder; Sandbox The structure of wheel axle of D19E locomotive is shown in figures 2.3 and 2.4 [23] The profile of the wheel rolling surface of D19E is shown in figure 2.5 Figure 2.3 The structure of wheel axle of D19E locomotive Figure 2.4 The wheel axle of D19E Figure 2.5 The profile of the wheel rolling surface of D19E Fig 2.3: Wheel axle (shaft end); Wheel cartridges; , Hydraulic oil plug; Wheel rims (wheels); Wheel rolling surface; Wheel edge; Motor support bearing; Dust barrier; Secondary gear of the shaft gearbox; Dmax- Maximum diameter of the wheel when new;Dmin – Miinimum diameter of the wheel (at the limited wear) Fig.2.4: 2.4: Wheel axle; Gear drive; Wheel The overall structure of the electric traction motor on the wheel axle of a diesel electric locomotive is generally shown in Figure 2.6 The D19E traction electric motors are shown in Figures 2.9, 2.12 Figure 2.6 The overall structure of the electric traction motor on the wheel axle of a diesel electric locomotive in general The traction motor support on the bogie frame; Active gear; Passive gear; Shell shaft gearbox; Traction motor bearing on wheel axle; Ring sealing; 7,13 Silver above and below of the motor bearing; Cover cap; Thin steel plate; 10 Plug; 11 Lubricating woolen lube; 12 Support; 14 Key; 14,19 Small support bars; 16 Springs; 17 Link bolts; 18 Link bar; 20 Top link bar; 21 Safety latch 10 11 12 13 14 15 16 17 18 19 868 20 21 22 23 720 866 Figure 2.9 The section of the rotor of the traction motor on D19E Bolts; Ball grease cover; Ball bearings; Shaft flange; Axle head bolt; Rear top cover; Neck ring bolt; Arc stamping rim; Coal rack box; 10 Pile for catching brush holder; 11 Coal price catch bolt; 12 Bolts to catch coal cables; 13 Rotor body; 14 Stator shell; 15 Front cover; 16 Cap bolts; 17 Bolts for front end grease cover; 18 Outer fat blocking rim; 19 Roto axis; 20 Cylindrical bearings; 21 Inner fat rim; 22 Front end grease cover; 23 Commutator Figure 2.12 The traction motor ZQDR 310 1.Traction motor case; The opening of the folding pipe for cooling gas; Ears hanging on the bogie frame; Drive covers and ventilation holes; Active gear and shaft of the traction motor; Axle suspension bracket; Box of lubricating oil; Power cord and gutters 2.2 Damage types of parts on diesel locomotives The damage on the locomotive is influenced by a series of factors that always interact and depend on each other such as: load, oscillation, impact, vibration, environmental conditions, quality of infrastructure: vertical alignment, curves, operating speed on the route, etc While it is not possible to conduct studies to evaluate the effects of each factor on wear and tear, damage of locomotive parts during the exploitation process, It is possible to evaluate the combined effects of all factors through statistics on wear and tear in the actual operation on the route in a certain time period This approach has been applied by countries when building a planned backup maintenance system of locomotives [92  100] and is also chosen by this PhD reasearcher Through the above analysis, it is possible to summarize the types of wear and tear of the parts on the locomotive as shown in Table 2.4 Table 2.4 The types summary of wear and tear of the parts on the locomotive Damages caused by external forces Damages over time of impact (load, vibration, impact, vibration, environmental conditions, quality of infrastructure: vertical alignment, curve, operating speed on the route ) Due to mechanical Due to motorized Due to chemical-thermal Failure gradually Failure suddenly wear impact effects (progressively) (unexpected) - Normal wear and tear Gravel, warping, Curled, warped, twisted, - Mechanical wear Curled, warped, twisted, cracked, (having rules) warping, twisting, cracked, broken, flaking, - Fatigue broken, flaked, peeled, - Unusual wear and tear cracking, breaking, flaking, punctured, burnt, - Aging punctured, tired, burned, pitted (few rules) flaking, peeling, pitted, corroded (rusted), (There are rules) (few rules) puncturing aging Considering types of damages Failure gradually (progressively) Failure suddenly (unexpected) The wear and tear law of the part over time is the basis for establishing a + Rarely has a rule planned backup repair cycle, also known as periodic repair Sudden failures that go into repair are called ad hoc repairs (repair by state) It is not part of the periodic repair system + If there is a rule Then it can be put into the system for periodic repair A periodic repair system is then upgraded one step and is called a more advanced repair system The thesis topic only focuses on gradual damage, namely damage caused Thesis topic has not had research conditions on unexpected by mechanical wear of some main details working in the friction mode damage In the next time can put research problems on this issue under the combined impact of all information factors through the intensity of their wear and tear during the extraction process 2.3 Model to determine and evaluate the wear and tear characteristics of some of the main components of diesel electric locomotives When studying the wear and tear process of the running parts of diesel locomotives in general and diesel electric locomotives in particular, first of all attention should be paid to the wear and gap of the following main parts and components Here: wear of rolling surface and rim wear; wear (seams) of support bearing of traction motor; wear of the commutator of traction motor Normal wear and tear of the wheel include: Rolling surface and edge wears (fig 2.13) The models are shown in tables 2.5  2.7 wear area on the edge and rolling surfac concave wear area on roller Hình 2.13 Wear and tear of the wheel include: Rolling surface and edge wears Table 2.5 General model to process statistics to determine the wear characteristics of rolling surface and edge of the wheels on diesel locomotives No data n axle BXT BXP Colect n data The wear The wear characteristics of characteristics of the left BX1 T the right BX1 P Colect 2n data The wear characteristics generated on axle No.1 The wear of rolling surface and edge of the wheels axle j axle m BXP BXT BXP The wear The wear The wear The wear characteristics characteristics of characteristics of characteristics of of the right the left BXj T the left BXm T the right BXm P BX j P BXT The wear characteristics generated on axle No.j The wear characteristics generated on axle No m summary BXT BXP The wear characteristics of all BX P The wear characteristics of all BX T The wear characteristics generated on all the axles Table 2.6 General model to process statistics to determine the wear characteristics (the gaps) of bearing of traction motor on diesel locomotives No data n Colect n data Colect 2n data The wear (clearance) of support bearing of traction motor axle axle j axle m BXT BXP BXT BXP BXT BXP The wear The wear The wear The wear The wear The wear characteristics of characteristics of characteristics of characteristics of characteristics of characteristics of the left BX1 T the right BX1 P the left BXj T the right BX j P the left BXm T the right BXm P The wear characteristics generated on The wear characteristics generated on The wear characteristics generated on axle No.1 axle No.j axle No m summary BXT BXP The wear The wear characteristics characteristics of all BX P of all BX T The wear characteristics generated on all the axles Table 2.7 General model to process statistics to determine the wear characteristics of the commutator of traction motor on diesel locomotives No n The wear on axle No m The wear on axle No m j The wear on axle No m Generally Wear characteristics of the motor on the axle No Wear characteristics of the motor on the axle No j Wear characteristics of the motor on the axle No m Generally wear charactoristics Notes for tables 2.5 - 2.7: wear and tear statistics: i = 1, 2, , n; - Number of wheel axes of the locomotive to be surveyed: j = 1,2, , m; - Locomotive D9E, D12E: m = 4; - Locomotive D13E, D18E, D19E, D20E: m = 6; Symbols: BX T - left wheel; BX P - right wheel 2.4 Basıs of determınatıon of work tıme untıl damage by wear of the parts on the locomotıve 2.4.1 General concept The wear and tear process can be considered according to two models: the traditional model (the classical model) and the probability model The process of the wear and tear of the details according to the traditional model can be found in [31], [32], [49] In this thesis, not consider the traditional wear model, only consider the wear and tear process of the details from the point of view of probability 2.4.2 The wear of the parts from a probabilistic point of view The random wear process is shown in figure 2.16 [16], [41] Figure 2.16 Random wear and time distribution density functions to wear failure f (t) and time wear distribution density function at the time t, f (I) To determine the reliability parameters of the worn part group can be carried out in two ways [16], [41] 2.4.3 Determine the reliability parameters according to the working time to failure by wear Probability of failure at the moment when the wear of the elements has reached the limit value t Igh , Q  t    f  t dt  St1 (2.2) The value of this integration is equal to the area St1 on the distribution density function diagram f(t) Non-failure probability (reliability function) at the time t 11 sudden failure The content of the thesis is only limited to the gradual failure process but specifically the mechanical wear of some main details working in the friction mode The study of unexpected failure types has not yet been conducted Having built up the models to determinate wear characteristic for the calculation of the working life when the parameters of their wear and clearance reach the specified limits In programming language Matlab has built a calculation program to determine the working time at a given confidence level (gamma percentage working time) of the parts until the failure due to wear and is packed into a complete software package Identified the gamma 50%, 75%, 80%, 85% and 90% working time until the failure due to wear of wheels, bearings and commutator of D19E locomotives used at the Saigon Locomotive Enterprise, which are input into determining the optimal working time in consideration of their repair costs, will be discussed in chapters and CHAPTER BASIS FOR OPTIMIZING WORKING TIME UNTIL DAMAGE BY WEAR OF THE LOCOMOTIVES’ PARTS AND BUILD A CALCULATION PROGRAM 3.1 The basis of optimization of the system of repair cycles of the parts on the machine head Optimization of a planned MRC system is carried out by minimizing the total unit costs for maintenance and repairs, then the objective function takes the form: N q( L1, L2 , , LN )   L  i 1 Ci (3.6) i With constraints:  Li  L i , with i = 1, 2, , N (3.7) in which: q- total cost unit for repair, VND/km running; Ci - cost of restoration of ith part , VND; Li repair cycle of ith part , km; N - the number of parts; l i - gamma percentage life of the ith part at a fixed reliability level , km When examining the repair cycle structure of the locomotive [93 ÷ 97], it is found that they are all built according to the principle of multiples of the running between repairs The ratio  Li Li 1 (3.8) is the multiple of repair cycle the ith part where: Li-1 - repair cycle of i-1 part; Li - repair cycle of ith part According to the numbering just selected, the distance running Li ≥ Li-1, so the multiples of - are positive integers, meaning can get the values 1, 2, 3, Repair cycles of various parts or components taking into account their multiples are written in the form: 12 L2 = a2.L1 (3.9) Li =ai.ai-1… a2 L1 Ln = an.an-1… a2 L1 Since the running distance between repairs of all parts is a multiple of the recovery cycle of the first part, the service life is minimal, so call the part is a "base" part If the baseline distance and the multiples of all other parts are known, the distance between their repairs can be calculated using (3.9) Then, the objective function (3.6) will take the form: N Ci (3.10)  min; q( L , a , a , , a )  N  a a i 1 i i 1 .a2 Li and the constraints (3.7) take the form: < ai.ai-1… a2 L1 ≤ li (3.11) < Ll ≤ l1; (3.12) in which: a2 ,…, an ; i = 2,…,n - the multiple factors (positive integers); Ll - repair cycle of first part (base part) Note that: l i - the gamma % working time (life) of the ith element, determined from statistics on the wear and tear of the parts under the specific conditions of the Vietnam railway Therefore this is a constraint on exploitation conditions in Vietnam; Ci - the cost of the ith detailed or part restoration is also determined in the specific operating conditions of Vietnam railway, so it is also a binding condition of the operating conditions in Vietnam Thus, it can be said that the constraints on the exploitation condition in Vietnam are implicit, through l i and Ci constraints Constraints (3.11) and (3.12) are denoted by linear functions, while the objective function (3.6), (3.10) is not linear relative to the running distance with integer multiples The problem of finding optimization of the nonlinear objective function is converted to the form of nonlinear mathematical planning problems N Expression (3.10) can be rewritten as follows: q   q (L ) i i i 1 Absolute minimum of the target function the total unit costs for recovering the part or part under consideration in the repair cycle L1 , L2 ,…,LN considering multiples between them:  N    q*   qi ( Li )   i 1   L1  1 LN   N In order to determine the optimal structure of the repair cycle of parts and components, a dynamic planning method with the following basic functional equations is needed: f k ( Lk )  q ( L )  fk 1( Lk 1) , Lk   k k k (3.23) Using the dynamic planning method allows finding 1* ( L1) - the minimum total unit costs for the recovery of all parts considered at the fixed part repair cycle first L1 and next - is the minimum value of the target function q* 13 3.2 Develop a program to calculate the optimal repair cycle system of the part on the locomotive with consideration of minimum repair costs and gamma percentage life of the part 3.2.1 Set up algorithm flowcharts - Algorithm flowchart of optimized structure of part repair cycle by gammapercentage life of the parts corresponding to a given value of running distance L1 (Figure 3.1a) - Algorithm flowchart of optimal structure of part repair cycle according to gamma-percentage life of the parts (Figure 3.1b) Figura 3.1a Algorithm flowchart of optimized structure of part repair cycle by gammapercentage life of the parts corresponding to a given value of running distance L1 Data input: N - number of parts; lγi - gamma percentage life of the i part; ni - number of ith parts; Ci – (absolute) cost of the repair or replacement of an ith part; L1 - - repair cycle of first part (base part) determined from the condition < Ll ≤ lγ1 (after having sorted the parts in ascending order according to gamma duty percentage life time, means that the first unit will have the smallest gamma percentage lif) On the other hand, for this value to be unique, then L1≥ lγ1 /2+1 14 Output result: The goal is to determine the optimal repair cycle L={L1, L2, , LN} and the multiple a={a1, a2, , aN} Steps to be taken: Step On the basis of repair cycle of the first part selected L1, determine the optimal repair cycle for the remaining parts with the objective function of total unit cost for N restoration parts return to minimum value: q( L1, L2 , , LN )   CL ti i 1 i in which: Cti = niCi - total repair cost of the ith part With constraints: ≤ Li ≤ li - the ith part repair cycle does not exceed its percentage gamma duty period The ith repair cycle is a multiple of L1 and is a multiple of the ith repair cycle:  Li Li 1 Step To solve the above problem, use the following dynamic planning method: From the objective function and the constraints, the basic functional equation of dynamic planning is established (the minimum total unit costs for the restoration of all parts, starting from the kth part to the nth part according to all repair cycles Lk  k , Lk+1  k+1 , , LN  N considering the multiplicity principle of repair cycles) is: (*) f k ( Lk )  q ( L )  fk 1( Lk 1) Lk   k k k Step Determination (*): derived from fN (LN ) because it can be calculated immediately by the formula: fN (LN ) = qN (LN) From there, according to (*) all remaining fk (Lk) values can be determined Step For each fk (Lk) found, there are corresponding Lk which is the optimal repair cycle of that part Step After determining, Lk will determine who by the formula: = Li/Li-1 Input data input: similar to figure 3.1a algorithm In addition, adding the value ∆L1 is the running step of the variable L1, in fact, it is usually chosen: ∆L1 = 1,000 km Output result: The goal is, from the algorithm of Fig 3.1a, to calibrate to find the optimal repair cycle so that the percentage gamma working life of parts L={L1, L2, , LN} is utilized and multiple a = {a1, a2, , aN}, the corresponding minimum total unit cost z* Steps to be taken: - Step 1: Perform algorithm in Figure 3.1a, output optimal repair cycle L ={L1, L2, , LN } and multiple coefficient a = {a1, a2, , aN} corresponds to L1 selected - Step 2: Gradually increase the value of L1 in increments of ∆L1 = 1,000 km, keep the values a,, receive new repair cycle values L, and calculate the total cost of the equivalent unit correspond to z (save these values for comparison) - Step 3: When increasing L1, until one of the repair cycle L1 values exceeds the percentage gamma service life of the ith part, the values a must be recalculated by reexecuting the algorithm figure 3.1a with existing L1 Then, repeat step again - Step 4: Step and step are repeated continuously until the L1 value exceeds the percentage gamma working time of the first part - Step 5: Compare all found z values The optimal repair cycle is the repair cycle with z at least z* 15 Figure 3.1b Algorithm flowchart of optimal structure of part repair cycle according to gamma-percentage life of the parts 3.2.2 Main features of the program The program has been packaged into a complete software package and is described in full in Appendix Conclusion of chapter On the basis of theory of optimization, in Matlab programming language, a general program of calculation has been established to determine the optimal working time of parts in general and of running gear parts in particular on the locomotives, according to the gamma percentage life and planned repair costs of the parts, are packaged into a complete software The program has been tested through a number of input data sets and the results calculated from foreign documents [94] show that the results received are completely identical, from which it can be concluded that this program has been built to be completely reliable The calculation program is an integrated program that can be used for all types of locomotives and wagons in Vietnam's railway system, not only that it can also be used for all kinds of equipment and mechanical machinery in general In addition to being used for the thesis content, this program (software) is completely commercialized 16 Having determined the optimal working time considering the repair costs of the parts of the D19E locomotives used at the Saigon Locomotive Enterprise corresponding to the working time with gamma 50%, 75%, 80%, 85% and 90%, discussed in detail in chapter CHAPTER DETERMINATION OF THE OPTIMAL WORKING TIME UNTIL FAILURE BY WEAR OF RUNNING GEAR PARTS ON DIESEL ELECTRIC LOCOMOTIVE D19E USED IN SAIGON LOCOMOTIVE ENTERPRISE 4.1 Determınatıon of workıng tıme untıl faılure by wear of runnıng gear parts on dıesel electrıc locomotıve D19E used ın Saıgon Locomotıve Enterprıse 4.1.1 The problem of collecting statistics on the wear and tear of the parts Investigated, measured and made statistics on the wear of the wheel rolling surface and edge, the wear and gap of the bearing of the traction motors, the wear of the commutator of the traction motors, the working term (in km) between repairs , corresponding to data on the wear and clearance of identified parts for all 30 D19E locomotives operating on the Hanoi-Saigon route managed by Saigon Locomotive Enterprise over a period of years, from 2013 to 2017 1.2 Determine the wear and tear characteristics of the part From the statistical data, by the calculation program, the wear and tear characteristics of the parts have been determined Figure 4.3 shows the results of setting the wear intensity distribution function f(c) of wheel rolling surface of D19E locomotives synthesized for axes with display of wear characteristics, including wear intensity c = 3.761mm/105km Figure 4.3 Interface for setting the wear intensity distribution function f (c) of wheel rolling surface D19E synthesized for axes with display of wear characteristics, including wear intensity c = 3.761 mm/105km Likewise, the wear characteristics have been determined, including the wear intensity of the components investigated during the application as follows (synthesized from the results in Table 4.1  4.4 of this thesis) No Value Number of items Wear intensity wheel rolling surface , mm/105 km wheel edge, mm/105 km clearance in support bearing of traction motor, mm/105 km commutator of traction motor 3.761 2.685 0.102 0.055 864 864 240 180 17 In advanced countries, when optimizing the repair cycle taking into account the cost of repairs, there are standards for reliability in vehicle operations, including regulations on the use of gamma percentage life-time (or “gamma life”) is 90% [94] This provision ensures a high level of reliability for the locomotive during operation In Vietnam, there are currently no national standards or standards on reliability in the design and manufacture of mechanical products as well as in the use and operation of vehicles Therefore, the researcher has proposed variants (scenario) to determine the optimal repair cycle according to gamma life 50%, 75%, 80%, 85% and 90% From these variants, users can choose the one that matches the actual conditions, the harmony between ensuring the reliability in the operation and the minimum unit cost for repair 4.1.3 Determine the working time of the D19E wheel set according to the wear of rolling surface According to the Repair procedure issued by the Vietnam Railway Corporation, for D19E [24], [25] locomotive: - Allowable wheel rolling surface wear during application is Igh = mm; - The new wheel diameter of the D19E locomotive is 1,000mm; - Minimum wheel diameter when discarding is 930mm; - Then the wear reserve amount is Igh = 1,000 - 930 = 70mm The results of determining the working time gamma 50%, 75%, 80%, 85% and 90% for all axes with allowed rolling surface wear Igh = 7mm shown on the interface in figure 4.6; with limited wear reserve Igh = 70 mm, shown in figure 4.7 Figure 4.6 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life of D19E wheel set according to the wear of rolling surface with wear limit Igh = 7mm Figure 4.7 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life of D19E wheel set according to the wear of rolling surface with wear reserve Igh = 70mm 4.1.4 Determining the working time of D19E wheel set due to wheel edge wear 4.1.5 Determining the working time of the support bearing of D19E traction motor According to the Repair procedure issued by the Vietnam Railway Corporation, for D19E [24], [25] locomotive: - Initial clearance of the support bearing DKK is Sbd = 0.30mm; - The maximum permissible gap of the bearing at the repair level is Sgh, Rd = 0.75mm; - The maximum allowable increase in clearance at the repair level Rd is ∆SRd = 0.45mm - The maximum permissible gap of the traction motor support bearing at the rejection limit (max) is Sgh, max = 1.00mm; - The maximum permissible increase in clearance at rejection limit (max) ∆S gh, max is 0.7mm The calculation results are shown in Figures 4.14 and 4.15 18 Figure 4.14 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life by the support bearing clearane of traction motor of D19E with Sgh,Rd = 0.75 mm and ∆SRd = 0.45 mm Figure 4.15 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life by the support bearing clearane of traction motor of D19E with Sgh,Rd = 1.0mm and ∆SRd = 0.7mm 4.1.6 Determine the working time of the D19E traction motor according to the wear of commutator According to the Repair procedure issued by the Vietnam Railway Corporation, for D19E locomotive [24], [25]: - The maximum permissible wear of commutator of traction motor at repair level Rd is Igh,Rd = 0.5mm; - The maximum permissible wear of commutator at rejection limit is Igh,max =3.5mm The calculation results are shown in Figures 4.18 and 4.19 Figure 4.18 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life of D19E traction motor by the wear of commutator synthesized for all axes with Igh, Rd = 0,5 mm Figure 4.19 Interface for determining the 50%, 75%, 80%, 85% and 90% gamma life of D19E traction motor by the wear of commutator synthesized for all axes with Igh,max = 3,5mm 4.1.7 Summary of the calculation results of percentage gamma working time of parts of D19E locomotive used at Saigon Locomotive Enterprise Summary of calculation results shown in Table 4.5 Table 4.5 Summary of the calculation results of the gamma percentage working time of running gear parts of D19E locomotives used at Saigon Locomotive Enterprise Parameters Objects Wear limits , mm Work.time t =50%, km t =75%, km t =80%, km t =85%, km t =90%, km Wear limits , mm Wheel roll surf Igh = 7,0 186.140 152.500 145.960 139.010 131.160 Igh= 70 Wheel edge Igh = 12 446.900 328.310 308.050 287.390 265.020 - Support bearing Sgh, Rd = 0,75; ∆SRd = 0,45 439.240 339.160 321.040 302.220 281.450 Sgh, max= 1,0; ∆Sgh, max = 0,7 Commutator Sgh, Rd = 0,5 904.840 641.420 598.270 554.760 508.250 Sgh, max = 3,5 19 Parameters Objects Work.time t =50%, km t =75%, km t =80%, km t =85%, km t =90%, km Wheel roll surf 1.861.350 1.524.960 1.429.590 1.390.140 1.311.610 Wheel edge - Support bearing 683.250 527.590 499.400 470.10 437.810 Commutator 6.333.880 4.489.960 4.187.860 3.883.300 3.557.760 The results of the percentage gamma working life of the parts are the basis for establishing the optimal repair cycle system considering the maintenance and repair costs, considered in the next contents 4.2 Calculation and determination of optimal repair cycle for D19E locomotive parts used at Saigon Locomotive Enterprise 4.2.1 Calculated data Calculated data includes defined percentage gamma working life (table 4.5) and repair costs including unit labor cost, corresponding spare parts and supplies of running gear parts (data provided by the Saigon Locomotive Enterprise), shown in table 4.8 with a gamma working time of 90% Table 4.8 The gamma 90% working time and the repair cost of the running gear parts of D19E locomotive at Saigon Locomotive Enterprise No Damaged part Quantity Repear operations Wheel disk 12 Support bearing of traction motor 12 Traction motor Wheel disk 12 Traction motor Turning the wheel roll surf when its wear reaches 7,0 mm - in Ky repair level Replacing the traction motor support bearing when the gap reaches 1,0 mm and its increasing gap reaches 0,7 mm - OVH level Turning the commutator when its wear reaches 0,5 mm - OVH level Replacing the wheels when their diameters remain 70 mm Replacing the traction motor when the wear of commutator reaches 3,5 mm Gamma working time 90 %, (103 km) Cost for repair to work, 103 VNĐ For one For all items, item, Ci Cph= m.Ci 131,16 560 6.720 437,81 15.000 180.000 508,25 600 3.600 1.311,61 22.131 265.572 3.557,760 396.500 2.379.000 4.2.2 Calculation results Of the parts above, the traction motor commutator has the maximum lifetime value (l=90% = 3,557.760 [103km]), so all calculations will be started from this part The initial survey is L1 = (0,5l1 + 1) or L1 = [(0,5  131,16)+1] 103km = 66,580 km  67,000km The calculation process and calculation results are shown on the interfaces figures 4.20  4.26 Figure 4.20 The interface displays initial data of the D19E locomotive running gear parts Figure 4.21 The interface calculates repair strategies for D19E locomotive parts at the running distance L1 = 67,000km 20 Figure 4.22 Interface to chart the possible repair strategies of the D19E locomotive running gear parts at the running distance L1 = 67,000km Figure 4.23 Interface to graph the optimal repair cycle structure of D19E locomotive running gear parts at running distance L1 = 67,000km Figure 4.24 Interface to adjust the optimal repair cycle structure of D19E locomotive running gear parts Figure 4.25 Graphical interface of the relationship between total unit costs for the recovery of running gear parts and the running distance of D19E locomotive Figure 4.26 Interface to draw the optimal repair cycle structure of D19E locomotive parts at running distance L1 = 67,000km Likewise, the optimal repair cycle of the D19E locomotive running gear parts was determined with 50%, 75%, 80% and 85% gamma working times and costs repair of details Here, an example introduces the final computational interfaces with gamma 75% and gamma 90% life time as shown in Figures 4.28 and 4.31 The results of the calculation of optimal repair cycle of D19E locomotive running gear parts according to the minimum repair costs with different percentage gamma working time are given in Table 4.9 21 a) b) Figure 4.28 Interfaces defining minimum repair cost (a) and optimal repair cycle (b) by 75% gamma life time of parts a) b) Figure 4.31 Interfaces defining minimum repair cost (a) and optimal repair cycle (b) by 90% gamma life time of parts Table 4.9 Summary of optimal repair cycle calculation results of D19E locomotive running gear parts according to minimum repair cost with different percentage gamma working times No Parameters Gamma working time L50%, 103 km Optimal repair cycle, 103 km Minimum total units cost, 103 VNĐ/km Gamma working time L75%, 103 km Optimal repair cycle, 103 km Minimum total units cost, 103 VNĐ/km Gamma working time L80%, 103 km Optimal repair cycle, 103 km Minimum total units cost, 103 VNĐ/km Gamma working time L85%, 103 km Optimal repair cycle, 103 km Minimum total units cost, 103 VNĐ/km Gamma working time L90%, 103 km Optimal repair cycle, 103 km Minimum total units cost, 103 VNĐ/km Replacing the traction Turning the Replacing the Turning the motor support bearing commutator wheel when wheel roll surf when the gap reaches when its its wear when its wear 1,0mm and its increasing wear reaches reaches reaches 7,0mm gap reaches 0,7 mm 0,5mm 70mm 186,614 L1=155 683,25 L2=620 152,50 L1=124 527,59 L2=496 145,96 L1=116 499,40 L2=464 139,01 L1=107 470,11 L2=428 131,16 L1=131 437,81 L2=393 904,84 L3=620 0,90861 641,42 L3=496 1,1358 598,27 L3=464 1,2141 554,76 L3=428 1,3162 508,25 L3=393 1,4163 Replacing traction motor when the wear of the commutator reaches 3,5mm 1.861,35 L4=1.860 6.333,880 L5=5.580 1.459,60 L4=1.488 4.489,96 L5=4.464 1.459,60 L4=1.392 4.187,86 L5=4.176 1.390,14 L4=1.284 3.883,33 L5=3.582 1.311,61 L4=1.179 3.557,76 L5=3.537 We see, when the optimal repair cycles are defined in terms of 50% gamma working time (mean time) and (75%, 80%, 85% and 90%) the lowest value of minmum unit cost for repairs is 0,9861.103 VND / km running, then gradually increasing and respectively 1,1358 103; 1,2141 103; 1,3162 103 and 1,4163.103 VND/km As the confidence level increases, the likelihood of unsafe train operation decreases, which also reduces the likelihood of unexpected damage 22 4.3 Comparing the results of calculating the optimal working time of running gear parts of D19E locomotive with the current repair cycle of VNR The current D19E locomotive repair cycle system of Vietnam Railway Corporation is the general system for the whole D19E locomotives The working time or repair cycle of the D19E locomotive running gear parts that this thesis has identified is only five (5) specific subsystems, including: Working time (cycle repair) of the wheel rolling surface, support bearings and rotor of traction motors, when their wear and gap reach the specified limit; Maximum service life until the removal (life-time) of the wheel wheel and rotor of the traction motor (these two parameters are not repair cycle) In these subsystems, at the time of repair we have information about the probability of non-failure and the minimum total unit cost for repair of these parts Optimal repair cycles of identified D19E locomotive running gear parts may be shorter or longer than corresponding repair cycle currently in the process of VNR, depending on gamma percentage working time of details (Table 4.9, 4.11) The comparison of the calculation results of the optimal working time of running gear parts with the current D19E locomotive repair cycle of VNR is not really compatible, only specific local Results of comparison are given in table 4.11 Table 4.11 Comparison of the optimal working time determined by different gamma percentage life of running gear parts of D19E locomotives used at Saigon Locomotive Enterprise with repair cycle in VNR Repair process T T Parts Quantity Wheel disk 12 Traction motor support bearing Traction motor 12 Wheel disk 12 Traction motor ‘s rotor Repair operation Turning the rolling surf when its wear reaches 7,0mm Repair level R2=120 Replacing when the gap reaches 1,0 mm or the gaps increase to 0,7 mm (removed) Repair level Rk(2)=480 Turning the commutator when its wear reaches 0,5 mm Repair level Rk(3)=720 Replacing when finished reserved wear reaches 70mm (diameter remains 930mm) Repair level Rđ=960 Replacing when the wear of commutator reaches 3,5mm The optimal working time corresponds to the working time gamma % (103km) 50%, 75%, 80%, 85%, 90% Minimal Total Minimal Total Minimal Total Minimal Total Minimal Total unit unit cost, unit cost, unit cost, unit cost, cost, 1,4163.103 3 3 0,90861.10 1,1358.10 1,2141.10 1,3162.10 VNĐ/km VNĐ/km VNĐ/km VNĐ/km VNĐ/km L1,tu =155 L1,tu =124 L1,tu =116 L1,tu =107 L1,tu =131 1,29R2 1,03R2 0,97R2 0,89R2 1,09R2 L2,tu = 620 L2,tu =496 L2,tu =464 L2,tu =428 L2,tu = 393 1,29Rk(2) 1,03Rk(2) 0,97Rk(2) 0,89Rk(2) 0,82Rk(2) L3,tu = 620 L3,tu = 496 L3,tu = 464 L3,tu = 428 L3,tu = 393 0,86Rk(3) 0,69Rk(3) 0,64Rk(3) 0,59Rk(3) 0,55Rk(3) L4,tu =1.861 L4,tu =1.488 L4,tu =1.392 L4,tu =1.284 L4,tu =1.179 1,94Rđ 1,55 Rđ 1,45 Rđ 1,34 Rđ 1,23 Rđ L5,tu =5.580 L5,tu =4.464 L5,tu =4.176 L5,tu =3.582 L5,tu =3.537 Repair level Rđ=960 5,81Rđ 4,65Rđ 4,35Rđ 3,73Rđ 3,68Rđ Repair level Rđ(3)=2.880 1,94Rđ(3) 1,55Rđ(3) 1,45Rđ(3) 1,24Rđ(3) 1,23Rđ(3) With the proposal to select the optimal repair cycle system according to the gamma life of 75%, it can be compared with the current cycles in the VNR process as follows (Figure 4.37 - 4.38): - The turning of the wheel rolling surface when the wear reaches 7.0 mm, equivalent to the grade R2(1); Rk(1); R2(2); Rk(2); R2(3); Rk(3); R2(4) and Rđ, have a cycle of 120,000 km - The replacement of the support bearings of traction motor when the gap reaches 1.0 mm and the increase of clearance reaches 0.7 mm is equivalent to the 23 grades Rk (2) and Rđ, with the repair cycle is 480,000km - Turning the commutator in specification when the wear rate reaches 0.5 mm is equivalent to the grades Rk(2) and Rđ, with a repair cycle of 480,000km - The replacement of the wheel when the diameter is 930mm is equivalent to 1.5 overhaul period (1.5 Rđ), which is equivalent to Rk (2) level in the second overhaul - The replacement of the rotor of traction motor when the commutator wear reaches 3.5mm is equivalent to 4.5 overhaul period (4.5 Rđ) Figure 4.37 The optimal repair cycle determined with a 75% gamma working life for parts of D19E locomotives used at Saigon Locomotive Enterprise Figure 4.38 D19E locomotive repair cycle (by Decision No 814/QD-ĐS dated 03 June 2016) Conclusion of chapter Collected a large number of statistics on wear and repair costs of running gear parts of 30 D19E diesel-electric locomotives used at Saigon Locomotive Enterprise of the Vietnam Railway Corporation for a period of years, from 2013 to 2017, and use it for research purposes That is also something that Vietnam railways system has not had the conditions to Defined the percentage gamma working time with five options: 50%, 75%, 80%, 85% and 90% of the running gear parts including: wheel rolling surface and wheel edge, bearing of traction motors and commutator of traction motor according to the wear and gap parameters specified by the manufacturer and shown in the D19E locomotive Repair procedure issued by Vietnam Railway Corporation Identified optimal repair cycles of components with variants according to 50%, 75%, 80%, 85% and 90% gamma woring time with the smallest total unit cost The corresponding most is 0.9881.103; 1.1358.103; 1.2141.103; 1.3162.103 and 1.4163.103 VND/km The obtained results are only the initial steps, but have proven that it is feasible to apply the selected research method into practice CONCLUSIONS AND RECOMMENDATIONS Conclusion In programming language Matlab has built a program of calculation to determine the gamma percentage working time and determine the optimal repair cycle for parts of the D19E locomotive until wear and tear and packaged into one complete software, the results obtained from the program are reliable 24 The calculation software is an integrated program that can be used for all kinds of equipment, mechanical machinery in general In addition to being used for the content of the thesis, this program (software) is also capable of commercialization Identified the optimal working time (repair cycle) of the parts with variants (scenario) according to the working time with gamma 50%, -75%, -80%, -85% and -90% with the smallest total unit cost These scenarios are the basis of reference for the managers and vehicle operators to choose the variant that is appropriate to the actual conditions, and the harmony between ensuring reliability in operation and the minimum total unit cost for repairs The research results of the thesis, although are only initial step in the application of reliability theory results and optimal theory to the practical problem of Vietnam in general and Vietnam’s railway transport in particular, have opened up the possibility for further research The research results of the thesis are the reference basis for the compilation of Procedures, Standards, Regulations on maintenance and repair of locomotives in general and D19E locomotives in particular for Vietnam railways system Recommendatıons The author proposes to choose the optimal working time until failure due to wear of some parts of the D19E locomotives used at the Saigon Locomotive Enterprise It is necessary to build a complete, comprehensive, unified, continuous and reliable statistical system of statistics on damage and wear of main parts on locomotives in general and running gear parts in particular more reliable for determining their time It is necessary to have data on maintenance and repair costs for the overall locomotive in general and the parts on the locomotive in particular to be more complete and reliable for the optimization of the working time cost-based work Only when there are input data on repair costs in a comprehensive, complete and accurate manner, can the results determine the optimal repair cycles of the parts that ensure the necessary level of confidence It is necessary to continue to research and apply the method of optimizing the repair cycle system according to the smallest cost for planned repair and unexpected repair This method can be applied to urban railway comming into operation in Vietnam, because the running gear of diesel electric locomotive is completely similar to the driving parts of the dynamic wagon in the urban metro train FURTHER RESEARCH DIRECTIONS It is necessary to continue to survey the wear and tear of the D19E locomotive parts not only at Saigon Locomotive Enterprise but in the whole VNR industry In addition the running gear parts, it is necessary to survey the wear and tear of other basic parts on the D19E locomotive in order to develop an extended optimized maintenance cycle system It is necessary to continue to research and apply the method of optimizing the repair cycle system according to the smallest cost for planned repair and unexpected repair Research on the application of this method to urban railway in Vietnam LIST OF PUBLISHED WORKS RELATED TO THE CONTENT Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2015), “A program for establishing the relationship between failure stream parameters and working time of details with sudden failure and determining their optimized repair cycles with considering the repair costs”, Science and Technology Development, Vol.18, K7-2015, pp.117-125 ISSN 1859-0128 Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2015), "Building a computer program to calculate the optimized repair cycle structure of rolling stock details with considering the repairing cost and the gamma – percent lifetime”, Transport and Communications Science Journal, Special issue – 11/2015, pp 134-139 ISSN 1859-2724 Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2016), "Building a computer program to determine optimized repair intervals of sudden failure rolling stock details with considering the cost of planned repair and sudden repair”, Transport and Communications Science Journal, Vol.50, pp 99-104 ISSN 1859-2724 Đỗ Đức Tuấn (cb), Nguyễn Đức Toàn, Võ Trọng Cang (2016), Basis for assessing the reliability of machine parts and vehicles damaged by wear, VNU-HCM ISBN 978-604-73-4150-4 Võ Trọng Cang (2016), Reliability-Based Optimizing Repair Intervals of Vehicle (R&D Proj report, C2014-20-04, HCMUT) 12/2016 Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2016), "Building a computer program to calculate the optimized repair interval system of unexpected failure rolling stock details according to minimum cost of planned and unexpected repair”, Transport and Communications Science Journal, Vol.53, pp 21-25, 50 ISSN 1859-2724 Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2018), "Development of a calculation program to determine the lifetime of mechanical elements damaged due to wear”, Transport and Communications Science Journal, Vol.64, 6/2018, pp 36-43 ISSN 1859-2724 Võ Trọng Cang, Đỗ Đức Tuấn (2018), “Research on reliability centered maintenance (RCM) application on transport means” Proc Science and Technology conference on Transportation - IV, 2018, HCM city- Việt Nam, (pp 384-390) ISBN 978-604-76-1578-01 Đỗ Đức Tuấn, Nguyễn Đức Toàn, Võ Trọng Cang (2018), "Development of a calculation program to determine the lifetime of irrepairable and unexpected failure mechanical elements", Proc of the 5th National Conf on Mechanical Science & Technolog (VCME 2018), NXB KHKT, Section 1: Mechanical engineering (pp 746-754) ISBN 978-604-67-1103-2 ... components of diesel electric locomotives When studying the wear and tear process of the running parts of diesel locomotives in general and diesel electric locomotives in particular, first of all attention... planned repair costs Research subjects Diesel electric locomotive used in Vietnamese railway system This type of locomotive, with superior features compared to diesel hydrolic locomotive, with the... territory 1.2 Overview of locomotives in the Vietnamese railway system Currently, Vietnam's railway system is managing and using a total of 282 diesel locomotives with 13 types imported from different