ONE APPLICATION OF THE INTERNATIONAL TERMINOLOGICAL STANDARD BDS ISO FOR THE DAMAGE IDENTIFICATION ON THE TEETH OF GEAR TRANSMISSIONS

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1 Proceedings of the 6th International Conference on Mechanics and Materials in Design, Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, July 2015 PAPER REF: 5691 ONE APPLICATION OF THE INTERNATIONAL TERMINOLOGICAL STANDARD BDS ISO FOR THE DAMAGE IDENTIFICATION ON THE TEETH OF GEAR TRANSMISSIONS Valentin Abadjiev 1, Georgi Dimchev 2, Emilia Abadjieva 1,3(*), Dimitar Karastoyanov 3 1 Institute of Mechanics, Bulgarian Academy of Sciences, Bulgaria 2 Technical University of Sofia, Bulgaria 3 Institute of Information and Communication Technologies (IICT), Bulgarian Academy of Sciences, Bulgaria (*) abadjieva@gmail.com ABSTRACT Extremely dynamical development of the contemporary political processes of the international integration demands on an adequately progress of the international scientific and industrial collaboration. Hence, the question for introduction of the uniform, European and on the international level terminology in the field of the basic characteristics of the engineering resources is very important. This work treats one application of the international terminological standard BDS ISO Gears. Wear and Damage to Gear Teeth. Terminology, for solving a judicial dispute. The objective conclusion of the technical specialist s report, designated by the court, is defined. Keywords: terminology standard, gear teeth damage, gear transmission. INTRODUCTION Some terms and definitions for standardization The specific thematically orientation of the current work requires to define in advance the following basic terms and definitions related to the term "standardization" and adequate its derivatives (BDS EN 45020:2007, 2007): Standardization. Activity of establishing, with regard to actual or potential problems, provisions for common and repeat use, aimed at the achievement of the optimum degree of order in a given context. International standardization. Standardization in which evolvements is open to relevant bodies from all countries. Standard. Document, established by consensus and approved by a recognized body, that provides, for common and repeated use, rules, guidelines of characteristics for activities of their results, aimed at the achievement of the optimum degree or order in given context. International standard. Standard that is adopted by an international standardizing/standards organization and made available to the public. Regional standard. Standard that is adopted by a regional standardizing/standards organization and made available to the public. Basic standard. Standard that has a wide ranging coverage or contains general provisions for one particular field

2 Track_F Tribology, Gears and Transmissions Terminology standard. Standard that is concerned with terms, usually accompanied by their definitions, and sometimes by explanatory notes, illustrations, examples, etc. The introduced terms and definitions are oriented to the specifics of the accomplished bellow expert assessments of the wears and damages of the studied transmission, when analyzing its operational suitability. Essence of the problems The extremely dynamic development of the contemporary political processes, which are connected with the enlargement of international political, military and economical unions, determine a natural dynamic of the international scientific and industrial collaboration processes. These processes also determine an extremely active economical exchange between different in their technical and technological level business structures. Therefore the question for the introduction of a uniform not only on a European but also on an international level, terminology in the field of the basic aspects of the engineering resources is very important. Such elements of that group of engineering resources are all types of gears. Hence a uniform world terminology in the field of gears geometry, firmness, manufacture technology, gears damages and wearing out should be introduced in the national standardization documents. For decades structures like Council for Mutual Economic Assistance (former economical structure of the East European countries), ISO, national standardization institutions and private certification organizations have worked and still work in the area of terminological unification. The approaching method, which basically is a development and approval of the national terminological standards, is inconsistent with the development of the European and world integration processes in the scientific, technical and manufacture areas (Arnaudov, 1990). The process of using a uniform terminology in every single direction of science should be treated as an element of strategy. This strategy is connected with the European and world integration processes. The mentioned method eliminates problems, which are local in character and are due to the linguistic specificity and national terminological traditions in the particular engineering area. This work is dedicated to the application of ISO Gears. Wear and Damage to Gear Teeth. Terminology in the solution of a court dispute, concerning the damage of the mechanical transmission elements of a tractor model URSUS The tractor has been used only during its guarantee period. (Abadjiev, 2004) An expert s report was made, which is a base for the court solution of the mentioned case. This expert s report was worked out with the application of the identical Bulgarian edition of the normative document BDS ISO The Bulgarian edition of the latest document, which is prepared by the first two authors of this study, was published in THE BASIC CHARACTERISTIC OF THE STANDARD BDS ISO The basic characteristics of this document are shown in its rubric Area of application (BDS ISO 10825, 1997). The BDS ISO determines the terms, which are used for description of the flanks of the teeth or the description of the damages, which could be observed on the gear mechanisms. It is given the short and exact description for every term. This description includes the important features of the tooth surfaces of the gear for identification of the shown wear or the damage

3 Proceedings of the 6th International Conference on Mechanics and Materials in Design, Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, July 2015 Every classified external view of a wearing or a damage of the teeth is illustrated with one or more pictures, which are typical examples of one or several teeth. At some cases are shown a several illustrations of the concrete tooth or the type damage, which show the existence of possible variants or differences, which can exist for the different teeth geometry. Every illustration is accomplished with a comment to facilitate an explanation. This international standard is only terminological. It is worked out to assist for identification the type s damages and to determine the condition of the gears, after a period of exploitation. To achieve this goal, the standard doesn t contain any information for the possible reasons and а prevention methods for the established conditions. But the general conditions are well known only by the specialists due to their accumulated operational experience. APPLICATION The complete standard document, which treats the different types of wear and damages to the gear mechanisms, did not exist in Bulgaria till Some basic damages, related to strength calculation of the gears are partially mentioned in (BDS , 1991). The presence of the BDS ISO fills the gap in the field of standardization of gear mechanisms and it is used in designer s practice and in student s training. Besides purely engineering application, this standard is important for jurisprudence for classification of observed damage caused mechanism s crashes. Such is the case for the technical expert s report preparation. The report refers to the occurred crashes in mechanical transmissions of two tractors brand URSUS 1634, import from Poland. This expert s evaluation, which is elaborated for the needs of the court, contains the following classification of the established damages on the teeth of the gears of the studied transmissions: Planet cylindrical gears (Fig. 1, Fig. 2) Fig. 1 - Planet carrier with spur cylindrical gear from the tractor URSUS 1634 transmission Indentation (BDS ISO 10825, pp. 27, 1997). The large numbers of depressions on the tooth flanks are caused by a passing through the mesh region foreign bodies during the meshing -511-

4 Track_F Tribology, Gears and Transmissions period. The classification of the damages into this category is based on their type and on the fact that the different groups of depressions are situated in vicinity of a plane, perpendicular to the geometrical axis of the cylindrical gear. (Fig. 3) Fig. 2 - Planet cylindrical gears from the tractor URSUS 1634 transmission Fig. 3 - Indentation (BDS ISO 10825, pp. 27, 1997): The depressions in the active tooth flanks are caused by the foreign bodies (metal particles) during the meshing Plastic deformation (BDS ISO 10825, pp. 28, 1997). The observed dents on the teeth and the displacement of the material can be explained with the exploitation under high loading and friction conditions. Overload breakage (BDS ISO 10825, pp. 51, 1997). The breakage of the teeth of the planet cylindrical gears is characterized with fracture surface of damage. On the page 53, of BDS ISO 10825, it is illustrated the breakage of the small cylindrical gear. The fracture structure dues of to the damage. This damage is in result of high alternating load (brittle fracture) (Fig. 4)

5 Proceedings of the 6th International Conference on Mechanics and Materials in Design, Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, July 2015 Fig. 4 - Ductile fracture (BDS ISO 10825, pp. 53, 1997): The breakage, as a result of the overload of the teeth of the small gear. There are simultaneously brittle fracture (BDS ISO 10825, pp. 52, 1997) and ductile fracture Central cylindrical gear Indentation (BDS ISO 10825, pp. 27, 1997) and broken after a plastic deformation (BDS ISO 10825, pp. 51, 1997). The indentations are accomplished with plastic deformations. The character of these deformations can be explained with the fact, that the central cylindrical gear is meshed at the same time with three planet cylindrical gears. That is why; there are a bigger number of foreign bodies, which passes between conjugate tooth surfaces in the processes of work meshing. The discussed here damages are not illustrated. Conic pinion and crown (Fig. 5, Fig. 6) Fig. 5 - Conical pinion and crown from the tractor URSUS 1634 transmission Indentation (BDS ISO 10825, pp. 27, 1997). The damages classified in this group are characterized by the same reasons, which are defined in the cylindrical gears section

6 Track_F Tribology, Gears and Transmissions Fig. 6 - Conical pinion from the tractor URSUS 1634 transmission Breakage (BDS ISO 10825, pp. 56, 1997). The broken edges of the teeth of the conic pinion and the crown can be explained with bearing inaccuracy. These type spatial gear mechanisms are sensitivity to the bearing inaccuracy (hypoid and conical gears with spiral teeth). This cause edge contact and non-uniform loading between meshed teeth (Fig. 7). Fig. 7. Breakage (BDS ISO 10825, pp. 56, 1997): The both illustrations show, that from all teeth of the gears are broken edges or parts, that are close to the tips of the teeth. Those two gears are damaged due to inaccurate assembling, that caused non-uniform loading of the meshed teeth -514-

7 Proceedings of the 6th International Conference on Mechanics and Materials in Design, Editors: J.F. Silva Gomes & S.A. Meguid, P.Delgada/Azores, July 2015 CONCLUSIONS The realized study covers the analysis of the gears robust and the lubrication of the gear mechanisms: The central gear measured robustness on the gear flanks is 60-62Rc, and in the base of the gear is 50-59Rc. Planet gear obtains robustness from 50-52Rc at its gear flanks, and in the core of the gear is 49-50Rc. The measured robustness is an ordinary for the gear flanks of these type gear mechanisms. This robustness confirms the fact, that the gear mechanisms are elaborated from low carbon lubricated steel. After that they are adequately thermo-chemically treated. The lack of damages, which are classified accordingly BDS ISO Sliding wear (pp. 5-7), Polishing (8pp.), and Scratching (scoring) (pp ), are evidence, that the spreading of the gear mechanisms, is accomplished with optimal oil for operational gear transmission. The classification of the damages of the studied gears helps to define the objective conclusion about the reason of damage appearance. These gears are part of the structure mechanical transmissions of two tractors URSUS The final expert conclusion is: The documented damages are result of considerable overload. This overload causes the defined breaks. The defined damages are in result of non-uniform loading of the meshed teeth, which is caused by inaccurate assembly of the gear pair. The other reason for the damages is occurring of the foreign bodies between teeth of the gears. This foreign bodies impact over the tooth flanks in the process of the work meshing. ACKNOWLEDGMENTS The authors gratefully acknowledge the funding by project AComIn: Advanced Computing for Innovation of the FP7 Capacity Programme, Research Potential of Convergence Regions, FP7-REGPOT REFERENCES BDS EN 45020:2007. Standardization and related activities - General vocabulary (ISO/IEC Guide 2:2004), Publishing House Standardization Print Co, Available from pp. Abadjiev V, Dimchev G, Abadjieva Е. An application of ISO in the solution of the court dispute, 12 International Scientific Conference CO-MAT-TECH 2004, October 2004, Trnava, Slovak Republic, 2004, Published on CD. Arnaudov K, Minkoff K, Parushev P, Bojdev V, Takov I. On the problem of an unique international terminology in the gear mechanisms Area. Vestnik Mashinoctroeniq (Monthly Journal for Science, Techniques and Manufacture), 12, Mashinostroenie, Moscow, 1990, p

8 Track_F Tribology, Gears and Transmissions BDS ISO Gears-wear and damage to the gear teeth.terminology. Publishing House Standardization Print Co., 17, Sanction on , Available from pp. BDS Cylindrical, involutе gear mechanisms with external meshing. calculation of the robustness of the gear teeth. Publishing House Standardization Print Co, 529, Sanction on Available from pp