ABSTRACT
Determination of surface wear of engineering materials was carried out using Pin-on- disc wear testing machine. Wear is a dynamic and complex process which involves not only surface and material properties but operating conditions as well. The wearing of surfaces may lead to extra cost of maintenance or manufacturing process. The present study developed dual condition Pin-on-disc wear testing machine with which both dry and lubricated surface contact of engineering material can be determined. The surface wear of Aluminium 6061, Bronze and Brass pins were investigated. The performance test was carried out based on varying loads, timeand speeds. The study determined pin wear rate, wear resistance and specific wear rate of the pins. The various pins were subjected to different performance test at constant sliding speed of 0.158m/s and 0.1975 m/s and at forces of 5N, 8N and 10N respectively. During experimental testing the pins were removed after 300 seconds and the final volume of each pin determined.The study indicated that Aluminium 6061 pin of 4mm diameter under dry surfaces at speed of 0.158m/s and applied force of 8N had highest wearing rate of 0.2129 mm3/m as compared to 6mm diameter pin used. The wear test for Bronze pin at constant speedof 0.158m/shad the lowest wearing rate of 0.0394mm3/m with a pin diameter of 6mm under applied force of 5N. The wearing rate per second under applied force of 5N and at sliding speed of 0.158m/s of 6mm diameter pin during lubricated condition include 20.5 for Aluminium 6061, Bronze and Brass respectively. The lubricated surface reduces wear to 54%. Bronze has 59.32 % lower wear rate per second in compare to Aluminium 6061 and Brass using the pin-on- disc developed by this study. This indicated that wear resistance increases in the order of Bronze, Brass and least occurred in Aluminium 6061 pin. The specific wear rate of 6mm diameter pin with lubricated surface has least wearing rate at sliding speed of 0.158m/s and sliding distance of 568.8m. The results ofspecific wear rate for Brass pin, Aluminium 6061 pin and Bronze pin were0.3172 × 10−3mm3/Nm, 0.5901 × 10−3mm3/Nm and0.2428 × 10−3mm3/Nm. In conclusion, engineering surface with good lubricating surface and higher surface area in contact have reduce wear rate. The study contributes to indigenous technology development in both Machine Design and Tribology.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
The study of wear, friction and lubricationare encompassed by the term Tribology. The word ‘Tribology’ is derived from the Greek word Tribos, which means rubbing or attrition. Tribology is a study of friction, wear and lubrication between two interacting surfaces in relative motion and of relative subjects and practices (John, 2008). The present study focuses on wear behaviour of engineering materials in which four broad general classes are known. They are adhesive wear, surface fatigue wear, abrasive wear and chemical/corrosion wear (Stolarski, 2000). Wear is among the most significant factors in processing of engineering materials (Kalpakjian and Schmid, 2009). Stolarski (2000) defined wear as loss of material fromcontacting bodies in relative motion. It is controlled by the properties ofthe material, the environmental operating conditions and the geometryof the contacting bodies. The wear mechanisms are in two groups. The firstdominated by the mechanical behaviour of materials, and the second defined by the chemical nature of the materials.
Kalpakjian and Schmid (2009) stated that wear is an undesired cumulative change in dimensions caused by thegradual removal of discrete particles from contacting surfaces in motion, due predominantlyto mechanical action. Also, corrosion often interacts with thewear process to change the character of the surfaces of wear particles through reaction withthe environment. Wear is, in fact, not a single process but a number of different processesthat may take place by themselves or in combination. Based on this understanding, Dalgobind and Anjani (2013) classified wear in to five major subcategories and they include: adhesive, abrasive, corrosive, surface fatigue and
deformation wears. This agreed with classes of wear mentioned by Stolarski (2000). John (2008) understood that wear is the progressive loss of substance from the surface of a solid body caused by mechanical action that involves the contact and relative motion with a solid, liquid or gaseous counter-body. The wear always hampered the positive benefit of engineering material and reduces the life cycle of the material (Kutz, 2006).
The engineering material experiences wear when subjected to variables such as temperature, force, velocity, external material and harsh environment like more acidic or basic condition.The complexity of the wear process may be better appreciated by recognising the involved variables. These variables are hardness, toughness, ductility, modulus of elasticity, yield strength, fatigue properties, and structure and composition of the mating surfaces, contact geometry, contact pressure, temperature, stress distribution, coefficient of friction, sliding distance, relative velocity, surface finish, lubricants, contaminants, and ambient atmosphere at the wearing interface (Kutz, 2006).
There will be engineering material surface damage or removal of material from one or both side of solid surfaces in a sliding, rolling or impact motion relative to one another by this aforementioned variable (John, 2008). The wear condition has surface interactions in different region base on relative speed on the surface contact. This result to transfer of heat during contact surface, it leads to loses as a wear particle. However, Lim and Ashby (2005) opined that wear of engineering material resulted from corrosive, adhesive/abrasive or frictional, fatigue and impact surfaces.
The wear on the surface is tested usingdual condition pin-on-disc machine to assess erosive surface of material from its main source. It is simply achieved by measuring workability of engineering material used in frictional state. There is need to perform mechanical tests condition or experimental condition based on available data.This will be critical if a material subjected to wear testfailed the quality test or engineering materials test. In engineering material test there is need for load or force that acts as impact on the defined materialsin use (Williams, 2006). According to Kutz (2006) pin- on-disc wear tests is done using application of load mountedon a pin in direct surface contact on a rotating disc. The surface contact will be on rotating disc at constant speed to obtain weight loss. The loss can be continually measured to determine wear rate of pin material. This method helps in characterising coefficient of friction and its applied force, and also wearing rate that exist between materials in surface contact.
This present study includes design, fabrication and performance analysis test as a concept of development of reliable dual machine. The design and fabrication process of the machine wasdeveloped through indigenous process by instituting a dual process instead on single pin condition. Altenburg et al. (2006) stated the development of this kind of machine in under-developed country such as Nigeria will boost trends of technology advancement.
1.2 Statement of the Problem
Wear is a dynamic and complex process which involves not only surface and material properties but operating conditions as well. The wears in engineering material include wearing of bolts and nuts experienced by machines and equipment used in workshop. In manufacturing process whenever there is dull drill bits, there is need for regrinding the drill bit for sharpening. The worn cutting tools can also be changed or replaced or repaired in this situation. The underground or buried pipelines that transport fluid may be subjected to wear due to corrosion (Kalpakjian and Schmid, 2009). Based on this, it is important to develop a machine that can test the surface wear of engineering material.
The wearing surfaces may lead to extra cost of maintenance and production. It also causes time consuming activities during reworking process. Most of the existing techniques for wear measurement are carried out on assumption. Based on this background, the present study addresses these challenges in terms of periodic measurement of the material with accurate digital liquid crystal display screen, sensor gauge and the machine perform at high speed of operation,which allows for faster and dynamic measurements of wear components. This gives better accuracy of the readings in the wearing process and wearing environment.
1.3 Aim of the Study
The study aims to develop a dual condition pin-on-disc wear testing machine that can be used to determine surface wear of engineering material in a laboratory.
1.4 Objectives of the Study
The objectives of this study include:
i. Design and fabrication of dual condition pin-on-disc wear testing machine capable of determiningwear on pin surface.
ii. Assembly of the pin-on-disc wear testing machine.
iii. Develop monitoring device that will continuously measure the pin length reduction.
iv. Carrying out performance testing analysis to determine surface wear behaviour and determine specific rate of wear of the pinbeing subjected to variable parameters such as load, time and speed.
1.5 Justification and Significance of the Study
Industries and institutions in Nigerialack locally fabricated wear testing equipment for carrying out wear testing research. Most available types that are used are foreign wear testing machines. Engineering field of wear surface research adopts foreign made wear machines which are expensive and not readily available to the researchers. For this reason, the present study developed dual condition machine for testing surface wearing behaviour of material. This was manufactured with components and available materials sourced locally in Nigeria. The machineischeaper and readily available for studying surface wear of engineering material. In addition, this improves productivity, quality control, good manufacturing practice and also spurs national economic growth. This is the most important reason that justifies the development of wear testing machine.
The significance of this study include developed pin-on disc wear testing machine, which will be useful for graduates or students who study engineering related courses such as, machine design, manufacturing/production engineering and material engineering course in university. The design and fabrication concept will aid student to design similar machines in the university. This can be adopted as wear testing machine in engineering laboratory of Mechanical Engineering of Federal University of Technology on completion. The study points out wear parameters that affects engineering materials and this can be used for studying reliability and failure analysis of such materials by the students. With the developed machine, the identification of wear regions, behaviour, processes, or estimation of degree of wear will become possible.
However, it is not easy to access foreign type of the machine by researchers on reliability and failure to analyse the effect of surface wears on engineering materials. This resulted in high cost of importation of such machine from manufacturers abroad.
This study will be beneficent to researchers on related concept by adopting the similar approach for machine design and wear analysis. The society at large will benefited from technological know-how acquired by this study through application of the outcome of the study. This is due to adoption of local innovation technology concept. This can be used as one of tool for boosting Nigeria economy. Thus, the development of dual condition pin-on-disc wear testing machine will create improvement in development and sustainable of local technology concept.
1.6 Scope of the Study
The scope of the present study is to: design, fabricate, assembly and carrying out performance evaluation test on dual condition pin-on-disc wear testing machine. The dual condition pin-on-disc wear testing machine was developed locally. The design analysis for the production was based on machine design concept. The computer aided design for designing the machine prototype was Pro-E software. The variable parameters of wear behaviour considered include speed, time and load by this study. However, the wear results were compared to other wear performance testing of other authors report.
This material content is developed to serve as a GUIDE for students to conduct academic research
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