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A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues
Materials Today: Proceedings xxx (xxxx) xxx
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A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues S.P. Jadhav a, S.H. Sawant b a b
Mechanical Engineering, D.O.T. Shivaji University, Kolhapur, Maharashtra, India J.J. Magdum College of Engineering, Jaisingpur, Maharashtra, India
a r t i c l e
i n f o
Article history: Received 13 June 2019 Accepted 25 June 2019 Available online xxxx Keywords: Non exhaust pollution Friction material Natural ingredients Characterization of brake pad material Performance testing
a b s t r a c t Non exhaust brake emission is one of the important issue concerns with health and environment. In brakes operation, wear debris are released in atmosphere and pollute the environment. Brake pad is classified in to three categories namely metallic, non-metallic and Non Asbestos Organic (NAO). Constituent elements of a brake pad are a reinforcement, binder, friction modifier, abrasive, filler and elanstomer. As per report of WHO and Environment Protection Agencies, some of the metals oxidised and produces toxic gaseous. Toxicity leads and creates bad effect on human health. The Environment Protection Agencies set a limit and ban on some elements. This paper focuses on remedies over environment and health issue because of brake pad emission. It is an important to reduce percentage of toxic elements at source and develop novel material compositions which are less dangerous to the environment and human health. Also, it satisfies all requirements of a brake pad material as per international standards. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
1. Introduction
2. Environmental and health issues
In an automobile braking system is used to control and safety of occupants as well as a vehicle. The brake assembly consists of rotating element called as a drum or disc and the stationary friction element is a pad. In operation of a brake pad, friction element rubs against a drum or disc. In metallic and semi metallic brake pad the percentage of metals and its ingredients are more than non asbestos organic pad. The brake pad constituent materials are binder, reinforcement, filler, friction modifier and abrasive. In operation of a brake, wear debris released in the atmosphere. The brake pad composition contains numbers of ingredients. Some of the metallic and other ingredients are toxic in natures which pollute the environment. Increase in percentage of these toxic elements dangerous to the environment. Some of the environment agencies have found the bad effect of brake pads constituent elements on a human health. Use of Asbestos is banned by environment protection agency because it is found to be a carcinogenic. Also, other constituents in the brake pad are creating human health issues.
The researcher studied the problem and focused on human health issues from the brake wears released particulate matter. Brake pad composition contains numbers of ingredients. The wear particles revealed maximum concentration of Fe, Cu, Si, Ba, K, Ti and many more. Some of the metallic ingredients oxidize and produce toxic gaseous. These are hazardous to human health and environment. The standards were set by government agency of different countries. Based on numbers of study the most toxicity producer elements are Asbestos, Cu, Cd, Ni, Pb, Sb and Zn. These elements create human diseases like lung cancer, irritating to respiratory track, kidney failure, lever, cell and tissue damage etc [1]. The health hazard because of fiber materials used as an asbestos substitute. The numbers of asbestos substitute fibrous materials which are synthetic and natural fibers. The WHO has reported 14 types of hazards asbestos substitute materials which contains para-aramid, attapulgite and carbon fiber. According to results of WHO p-aramid fibers are carcinogenic and effect on lungs which are found in an animal’s testing. The study focuses on the toxicity produced due
https://doi.org/10.1016/j.matpr.2019.06.703 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
2
S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
to fibrous. It depends on fiber size, durability and type. Fiber thinner than 3 mm can reach lower airways, while fiber longer than 5–10 mm finds in the lungs longer than shorter fiber. The carbon fiber with size 5–10 mm diameter are non respirable. Cellulose also, found to be non respirable and not hazardous. Attapulgite fiber was highly hazardous which causes tumors when they are long. Potassium octatitanate fibers are also hazardous; it causes mesothelioma when injected in to intraperitoneal organs [2].The particles airborne debris thrown off from brakes is toxic to higher plants. The researcher studied acute phytotoxicity of brake pad wear particles and investigated using cress seed grown in soil with higher concentration of wear debris. He developed cement based pad and results were compared with commercial brake pad and concluded that though morphology of both pad were similar, debris from commercial brake pad were more phytotoxic than cementitious pads, causing in root elongation and loss of plasma membrane integrity [3]. 3. Development of novel friction material There is wide scope to select natural ingredients from classification of natural fiber or materials. 3.1. Selection of material The important factors while selecting materials includes, high coefficient of friction, low wear rate, high heat dissipation rate, good resistance to water swell, dimensional stability at high temperature, posses high tensile, compressive and shear strength and low absorption rate to water and oil etc. In literature review many researchers fabricate the brake pads by using natural ingredients like Bio composite [10] cocoa bean shells [11], saw dust [12], Palm Kernel Fibers [13] banana peels [17], Ternary Agro-Waste [18] etc. These natural ingredients are used as filler or reinforcement in manufacturing of brake pad which reduce percentage of metals toxicity and cost. 3.2. Classification of brake pad Basically the friction materials are classified into three categories namely metallic, semi metallic and non metallic matrix. The major components of semi metallic matrix friction materials are Iron powder, metal, ceramic and copper fibers. This gives high thermal stability and high tribological properties. But disadvantages are low frequency noise, poor resistance to corrosion and harmful to brake disk. In non metallic matrix, modified resins along with rubber are used as a binder. The reinforcement is done with either organic fiber or inorganic fiber and other friction additives. These matrixes give excellent thermal stability, high strength and toughness and wear resistance properties. Organic friction material is widely used because of their excellent properties and eco-friendly nature. The brake pad constituent materials are as follows, Binder: Thermosetting material resins are most inexpensive binders which are used as a matrix material to hold structural element, filler, abrasive friction modifier, etc. together in case of brake pad manufacturing process. It gives good physical and chemical properties after modification. Typical binder material is Epoxy resin. Reinforcement: To increase mechanical properties the reinforcement (structural) elements are required. There are various types of fibers made up of metals, carbon, synthetic fiber, Kevlar, minerals, ceramics, natural fiber, etc. The fiber orientation also gives good results of mechanical properties. Steel wool and fiber glass have excellent structural reinforcement properties and high thermal stability this improves the performance of the brake pad. Filler: This is inexpensive and cost saving ingredients which improve the manufacturability. Fillers are used to fill voids
between particulates. These are chosen on thermal stability and compatibility. Here researchers have more choice to select natural ingredients and reduce percentage of metallic material in brake pad application. Vermiculite, cashew powder, and Barium Sulfate, etc. are used as fillers for the brake pad which also control and reduce noise. Friction additives: Graphite and Zirconium oxide are the friction modifiers used to control the operating coefficient of friction within range. They are also useful to stabilize, keep low temperature and low wear rate. They are used with low percentage due to poor compatibility with binding material. It also helps to control interfacial film. Abrasives: They are used to making brake pad hard and brittle. Increase in hardness helpful to clean rotating element (disc or drum). But excessive increase in hardness, damages the disc or drum. So abrasives are used with lower percentage to manufacture brake pad [4]. 3.3. Brake’s friction materials are mainly affected by the following factors Material Properties, Braking conditions, Surrounding conditions, Surface conditions, contact property, etc. 3.4. Manufacturing of frictional material In Powder metallurgy method, powder were uniformly mixed, pressed and sintered at high temperature to get required strength, stability and remove porosity [7,9,10]. In the compression moulding manufacturing method of a brake pad, first step is to calculate total volume of mould. Then weight percentage and mass of each respective ingredient calculated by using its specific gravity or density. With the help of hammer mill or ball mill crushing of different materials is to be done at different grit sizes. In the compression moulding technique, constituents were mixed properly in a blender. Then homogeneous mixture was transferred to the hot press mould at a temperature of 150 °C and pressure of 100 kg/ cm2. The load is gradually increased and kept between 10 KN and 15 KN for 20 min. Apply leak proof agent at the upper and lower surface of the mould to avoid leakage. The prepared brake pad specimen of different composition is cured in the furnace at the temperature of 500 °C for 6 hrs [6,8]. 4. Characterization of friction pads Brake lining material free from crack, pin holes and embedded foreign material or any other physical defect which can be detected through visual inspection. Prior to the testing of a brake lining the manufacturer shall provides all relevant technical information. The brake lining shall be type approved after carrying out brake performance tests as per standards. Following tests are conducted to characterize brake friction pad. 4.1. Mechanical testing 4.1.1. Rockwell hardness test The hardness value is determined by using Rockwell hardness testing machine. Rockwell hardness is defined in term of depth of penetration of a spherical indenter in to the specimen
The Rockwell hardness ¼ ð130 eÞ where, e = observe depth of penetration in unit of 0.002 mm. The hardness value for each specimen shall be taken as the arithmetic mean of readings from at least three indentations.
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
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S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
4.1.2. Shore hardness test This property is applicable for rubber based soft molded linings. The equipment Shore (D) Durometer is used according to ASTM D2240 standard. The hardness values shall be reported as the mean of three readings. One thing is important in a hardness value of brake pad material; it should be lower than disk or drum material hardness. The drum or disc more wear out if hardness of brake material is greater than drum or disk hardness.
%Water absorption ¼
Wf Wi 100 Wi
where Wf = final weight Wi = Initial weight 4.3. Chemical testing
4.1.3. Cross breaking strength This test is carried out to determine the ultimate stress, by bending of specimen with rectangular cross section which is regular throughout. It is computed as follows,
Cross breaking strength ¼
150WL BD2
W = load at failure L = gauge length in mm B = mean width of specimen D = mean thickness of specimen in mm 4.1.4. Shear testing The vertical shear force acts on the brake pads during braking. For safety braking operation, the brake pads must be resistant to shear force. Shear testing is used to determine the resistance of the brake pad and the back plate against the shear force. The shear test is carried out according to ISO 6312. 4.2. Physical testing 4.2.1. Porosity In automotive brake pad application, main function of porosity is to absorb energy and heat. This is important for effectiveness of braking system. The review shows that higher friction coefficient and wear rate because of higher contact areas between mating surfaces because of the lower porosity. Brake pad should have certain amount of porosity to minimize the effect of water and oil on friction coefficient.[12,13].
Theoretical density Experimental density 100 Porosity ¼ Theoretical density 4.2.2. Density test Archimedes’s principle is used to determine the volume of body which is in any shapes. Therefore, the density of an irregularly shaped object is calculated by measuring its mass in air and submerged in water. The density is expressed in equation
Density ¼
Weight in air Volume of water displaced
4.2.3. Specific gravity The specific gravity computed as follows, [5]
Specific gravity ¼
Wa Wa Wb
4.3.1. Acetone extract
The percentage of acetone extract ¼
W3 W2 100 W1
where W1 = weight of specimen in gram, W2 = weight of empty crucible in gram W3 = Weight of crucible + extract in gram 4.4. Thermal analysis Thermal analysis is carried out to study thermal behavior of brake pad at highest temperature. 4.4.1. Heat swell Heat produced when brake applied can make a brake pad in swell and can create performance deterioration problem. Heat swelling of sample is carried out according to SAEJ160. The sample cut in to the 10 mm 10 mm 5 mm size and thickness was measured at six places accurately, then sample was heated at 200 °C in the muffle furnace for two hours. The thickness was measured of heated sample [5].
% of Heat Swelling ¼
Tf Ti 100 Tf
where Tf – Final Thickness. Ti – Initial Thickness. 4.4.2. Thermo Gravimetric analysis Differential Thermo Gravimetric Analyzer is used for checking weight loss with respect to rise in temperature for raw material and finished product. TGA analysis will exactly point out decomposition temperature of individual raw material used in formulation. 4.4.3. Thermal conductivity (TC) Thermal conductivity of a friction material is dependent on various factors, including type and amount of fillers, processing technique, etc. and operating parameters such as temperature, method used for measurement sample size etc. With the increase in temperature TC decreases. No two friction materials can have identical thermo-physical characteristics.
where Wa – weight of specimen in air in gram. Wb – weight of specimen in water in gram. 4.2.4. Water absorption According to ASTM 570-98, the specimen is prepared and weight is done. For 24 h the sample are kept dipping in water. Then percentage of water absorbed is calculated from following relation,
5. Brake performance characteristics testing (Brake inertia dynamometer Test) The performance characteristics will be carried out on a suitable brake performance test rig. As shown in Fig. 1 the performance of brake lining is evaluated using chase dynamometer which gives results about actual behaviour of brake pad by observing parameters such as brake efficiency, stopping distance and brake fade temperature
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
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S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
8. Conclusion
Fig. 1. Schematic representation of the brake pad test rig. Part list - fig a. Brake pedal-1, Brake Booster-2, Brake Fluid Reservior, Thermocouple-4, Brake Caliper Assembly-5, Brake Pad-6, Main Drive Shaft-7, Step Pulley-8, Flywheel Weight-9, Brake Disk-10, Electric Motor-11.
This literature review focuses on bad effect of non exhaust emission on human health and environment. The researchers are also, studied its adverse effect on plants. Review papers shows that brake pads are manufactured by different natural ingredients and compares their results with traditional one. Some of researchers manufacture brake pad by the compression moldings and powder metallurgy method. Wear rate and coefficient of friction are found using Pin on disc apparatus. Performance of brake pad is tested using chase dynamometer. SEM Method is used to study morphology of brake pad specimen. There is wide scope to replace the metals by studying and characterizing natural materials and its ingredients. To minimize health and environment issues, novel material is developed with highest percentage of natural ingredients and the brake pad manufacturer must follow the regulations which are made by different countries in accordance with the percentage of metallic elements while manufacturing brake pad. References
Fig. 2. Schematic diagram of pin on disc apparatus. Part list- fig.b. Input Weight-1, Weight Holder-2, Vertical Adjuster-3, Horizontal Adjuster-4, Disk (Hardened)-5, Bearing-6, Chuck-7, Specimen-8, Shaft-9, Frequency Inveter-10, Rotating Shaft-11, Pulley-12&13, Belt-14, Bearing-15, Motor and Gear-16.
6. Tribological testing This will be done on pin on disc apparatus as shown in Fig. 2. The tribological behaviour of brake lining material is checked using pin on disc apparatus which give result about coefficient friction, wear rate at variable speed, different load condition and different sliding distances. 7. SEM-EDX analysis SEM images can help us to observe distribution of grain structure and surface defects. That is useful to optimize research processes, perform better analysis and save valuable time. The manufacturing defects are also identified and studied by SEM images.
[1] R. Ciudin, P.C. Verma, S. Gialanella, G. Straffelini, Wear debris materials from brake system environmental and health issue, Department of Industrial Engineering, University of Trento, Italy. Sustainable City IX, Vol. 2. 1423. [2] Seung-Hyun, Types and health hazards of fibrous materials used as asbestos substitute, J. Safety Health Work (2018) 360–364. [3] Simone Maiorana Federico Teoldi, sara silvani, alessandro Mancini, alessandro sanguineti, federico mariani, Claudia cella, aitziber lopez, marco albetro carlo potenza, marco lodi, damien dupin, tiziano sanvito, andrea bonfanti, emilio benfenati, diego baderna. Phytotoxicity of wear debris from traditional and inovative brake pad. J. Environ. Int. 2018, pp. 156-163. [4] Xingming Xiao, Yan Yin, Jiusheng Bao, Lu Lijian, Xuejun Feng, Review on friction and wear of brake materials, Adv. Mech. Eng. (2016). [5] Bureau of Indian Standards , Automotive vehicle – Brake Linings, Part-3, Methods of Test, New Delhi, March 1994. [6] P. Manooj Kumar, Bachina Harish, S. Gowthaman, K. Rajesh, Development and study of tribological properties of bio composite for brake pad application, Int. J. Mechan. Product. Eng. Res. Dev. 7 (6) (2017). [7] Filler Adeyemi Ibukun Olabisi Nuhu. A. Ademoh, Modestus Okwu, Development and Assessment of Composite Brake Pad Using Pulverized Cocoa Beans Shells Filler. Int. J. Mater. Sci. Appl. 5(2) 2016, pp. 66-78. [8] Sadiq Sius LAWAL, Katsina Christopher BALA, and Abdulkareem Tunde ALEGBEDE, Development and production of brake pad from sawdust composite, Mech. Eng. Dept., Federal University of Technology, P.M.B. 65, Minna,Niger State, Nigeria. [9] K.K. Ikpambese, D.T. Gundu, L.T. Tuleun, ‘‘Evaluation of Palm Kernel Fibers (Pkfs) for Production of Asbestos-Free Automotive Brake Pads, King Saud University, Journal of King Saud University, Engineering Science, University of Agriculture, p.m.b. 2373, Makurdi, Nigeria. 6 February 2014. [10] O.I. Sekunowo, S.I. Durowaye, G.I. Lawal, Synthesis and Characterization of Iron Millscale Particles Reinforced ceramic Matrix Composite, Department of Metallurgical and Materials Engineering University of Lagos, Akoka Lagos, 2017. [11] U.D. Idris, V.S. Aigbodion, I.J. Abubabkar, C.I. Nwoye, Eco-Friendly Asbestos Free Brake-Pad: Using Banana Peels”, King Saud University Journal of King Saud University Engineering Sciences Samaru College of Agriculture, Ahmadu Bello University, Zaria, Nigeria 11 June 2013. [12] Ibrahim Mutlu, Ilker Ssugbzu, Ahmet Keskin, The effect of Porosity in Friction Performance of Brake Pad using Waste Tire Dust, Technology Faculty Afyon Kocatepe University Tarsus Technology Faculty Mersin University Mersin Turkey, Bolu Vocational School Abant Izzet Baysal University Bolu Turkey. Afyonkarahisar, Turkey.Polimeros Vol. 25 no.5 Silo Carlos Sept/Oct. 2015. [13] Rathod Abhik , Umasankar V, M. Anthony Xavior, ‘‘Evaluation of Properties for Al-SiC Reinforced Metal Matrix Composite for Brake Pad”, 12th Global Congress on Manufacturing and Management, GCMM 2014 Procedia Engineering 97 (2014) 941 -950 SMBS, VIT University,Vellore 632014, Tamilnadu,India.
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues S.P. Jadhav a, S.H. Sawant b a b
Mechanical Engineering, D.O.T. Shivaji University, Kolhapur, Maharashtra, India J.J. Magdum College of Engineering, Jaisingpur, Maharashtra, India
a r t i c l e
i n f o
Article history: Received 13 June 2019 Accepted 25 June 2019 Available online xxxx Keywords: Non exhaust pollution Friction material Natural ingredients Characterization of brake pad material Performance testing
a b s t r a c t Non exhaust brake emission is one of the important issue concerns with health and environment. In brakes operation, wear debris are released in atmosphere and pollute the environment. Brake pad is classified in to three categories namely metallic, non-metallic and Non Asbestos Organic (NAO). Constituent elements of a brake pad are a reinforcement, binder, friction modifier, abrasive, filler and elanstomer. As per report of WHO and Environment Protection Agencies, some of the metals oxidised and produces toxic gaseous. Toxicity leads and creates bad effect on human health. The Environment Protection Agencies set a limit and ban on some elements. This paper focuses on remedies over environment and health issue because of brake pad emission. It is an important to reduce percentage of toxic elements at source and develop novel material compositions which are less dangerous to the environment and human health. Also, it satisfies all requirements of a brake pad material as per international standards. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
1. Introduction
2. Environmental and health issues
In an automobile braking system is used to control and safety of occupants as well as a vehicle. The brake assembly consists of rotating element called as a drum or disc and the stationary friction element is a pad. In operation of a brake pad, friction element rubs against a drum or disc. In metallic and semi metallic brake pad the percentage of metals and its ingredients are more than non asbestos organic pad. The brake pad constituent materials are binder, reinforcement, filler, friction modifier and abrasive. In operation of a brake, wear debris released in the atmosphere. The brake pad composition contains numbers of ingredients. Some of the metallic and other ingredients are toxic in natures which pollute the environment. Increase in percentage of these toxic elements dangerous to the environment. Some of the environment agencies have found the bad effect of brake pads constituent elements on a human health. Use of Asbestos is banned by environment protection agency because it is found to be a carcinogenic. Also, other constituents in the brake pad are creating human health issues.
The researcher studied the problem and focused on human health issues from the brake wears released particulate matter. Brake pad composition contains numbers of ingredients. The wear particles revealed maximum concentration of Fe, Cu, Si, Ba, K, Ti and many more. Some of the metallic ingredients oxidize and produce toxic gaseous. These are hazardous to human health and environment. The standards were set by government agency of different countries. Based on numbers of study the most toxicity producer elements are Asbestos, Cu, Cd, Ni, Pb, Sb and Zn. These elements create human diseases like lung cancer, irritating to respiratory track, kidney failure, lever, cell and tissue damage etc [1]. The health hazard because of fiber materials used as an asbestos substitute. The numbers of asbestos substitute fibrous materials which are synthetic and natural fibers. The WHO has reported 14 types of hazards asbestos substitute materials which contains para-aramid, attapulgite and carbon fiber. According to results of WHO p-aramid fibers are carcinogenic and effect on lungs which are found in an animal’s testing. The study focuses on the toxicity produced due
https://doi.org/10.1016/j.matpr.2019.06.703 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 1st International Conference on Manufacturing, Material Science and Engineering.
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
2
S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
to fibrous. It depends on fiber size, durability and type. Fiber thinner than 3 mm can reach lower airways, while fiber longer than 5–10 mm finds in the lungs longer than shorter fiber. The carbon fiber with size 5–10 mm diameter are non respirable. Cellulose also, found to be non respirable and not hazardous. Attapulgite fiber was highly hazardous which causes tumors when they are long. Potassium octatitanate fibers are also hazardous; it causes mesothelioma when injected in to intraperitoneal organs [2].The particles airborne debris thrown off from brakes is toxic to higher plants. The researcher studied acute phytotoxicity of brake pad wear particles and investigated using cress seed grown in soil with higher concentration of wear debris. He developed cement based pad and results were compared with commercial brake pad and concluded that though morphology of both pad were similar, debris from commercial brake pad were more phytotoxic than cementitious pads, causing in root elongation and loss of plasma membrane integrity [3]. 3. Development of novel friction material There is wide scope to select natural ingredients from classification of natural fiber or materials. 3.1. Selection of material The important factors while selecting materials includes, high coefficient of friction, low wear rate, high heat dissipation rate, good resistance to water swell, dimensional stability at high temperature, posses high tensile, compressive and shear strength and low absorption rate to water and oil etc. In literature review many researchers fabricate the brake pads by using natural ingredients like Bio composite [10] cocoa bean shells [11], saw dust [12], Palm Kernel Fibers [13] banana peels [17], Ternary Agro-Waste [18] etc. These natural ingredients are used as filler or reinforcement in manufacturing of brake pad which reduce percentage of metals toxicity and cost. 3.2. Classification of brake pad Basically the friction materials are classified into three categories namely metallic, semi metallic and non metallic matrix. The major components of semi metallic matrix friction materials are Iron powder, metal, ceramic and copper fibers. This gives high thermal stability and high tribological properties. But disadvantages are low frequency noise, poor resistance to corrosion and harmful to brake disk. In non metallic matrix, modified resins along with rubber are used as a binder. The reinforcement is done with either organic fiber or inorganic fiber and other friction additives. These matrixes give excellent thermal stability, high strength and toughness and wear resistance properties. Organic friction material is widely used because of their excellent properties and eco-friendly nature. The brake pad constituent materials are as follows, Binder: Thermosetting material resins are most inexpensive binders which are used as a matrix material to hold structural element, filler, abrasive friction modifier, etc. together in case of brake pad manufacturing process. It gives good physical and chemical properties after modification. Typical binder material is Epoxy resin. Reinforcement: To increase mechanical properties the reinforcement (structural) elements are required. There are various types of fibers made up of metals, carbon, synthetic fiber, Kevlar, minerals, ceramics, natural fiber, etc. The fiber orientation also gives good results of mechanical properties. Steel wool and fiber glass have excellent structural reinforcement properties and high thermal stability this improves the performance of the brake pad. Filler: This is inexpensive and cost saving ingredients which improve the manufacturability. Fillers are used to fill voids
between particulates. These are chosen on thermal stability and compatibility. Here researchers have more choice to select natural ingredients and reduce percentage of metallic material in brake pad application. Vermiculite, cashew powder, and Barium Sulfate, etc. are used as fillers for the brake pad which also control and reduce noise. Friction additives: Graphite and Zirconium oxide are the friction modifiers used to control the operating coefficient of friction within range. They are also useful to stabilize, keep low temperature and low wear rate. They are used with low percentage due to poor compatibility with binding material. It also helps to control interfacial film. Abrasives: They are used to making brake pad hard and brittle. Increase in hardness helpful to clean rotating element (disc or drum). But excessive increase in hardness, damages the disc or drum. So abrasives are used with lower percentage to manufacture brake pad [4]. 3.3. Brake’s friction materials are mainly affected by the following factors Material Properties, Braking conditions, Surrounding conditions, Surface conditions, contact property, etc. 3.4. Manufacturing of frictional material In Powder metallurgy method, powder were uniformly mixed, pressed and sintered at high temperature to get required strength, stability and remove porosity [7,9,10]. In the compression moulding manufacturing method of a brake pad, first step is to calculate total volume of mould. Then weight percentage and mass of each respective ingredient calculated by using its specific gravity or density. With the help of hammer mill or ball mill crushing of different materials is to be done at different grit sizes. In the compression moulding technique, constituents were mixed properly in a blender. Then homogeneous mixture was transferred to the hot press mould at a temperature of 150 °C and pressure of 100 kg/ cm2. The load is gradually increased and kept between 10 KN and 15 KN for 20 min. Apply leak proof agent at the upper and lower surface of the mould to avoid leakage. The prepared brake pad specimen of different composition is cured in the furnace at the temperature of 500 °C for 6 hrs [6,8]. 4. Characterization of friction pads Brake lining material free from crack, pin holes and embedded foreign material or any other physical defect which can be detected through visual inspection. Prior to the testing of a brake lining the manufacturer shall provides all relevant technical information. The brake lining shall be type approved after carrying out brake performance tests as per standards. Following tests are conducted to characterize brake friction pad. 4.1. Mechanical testing 4.1.1. Rockwell hardness test The hardness value is determined by using Rockwell hardness testing machine. Rockwell hardness is defined in term of depth of penetration of a spherical indenter in to the specimen
The Rockwell hardness ¼ ð130 eÞ where, e = observe depth of penetration in unit of 0.002 mm. The hardness value for each specimen shall be taken as the arithmetic mean of readings from at least three indentations.
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
3
S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
4.1.2. Shore hardness test This property is applicable for rubber based soft molded linings. The equipment Shore (D) Durometer is used according to ASTM D2240 standard. The hardness values shall be reported as the mean of three readings. One thing is important in a hardness value of brake pad material; it should be lower than disk or drum material hardness. The drum or disc more wear out if hardness of brake material is greater than drum or disk hardness.
%Water absorption ¼
Wf Wi 100 Wi
where Wf = final weight Wi = Initial weight 4.3. Chemical testing
4.1.3. Cross breaking strength This test is carried out to determine the ultimate stress, by bending of specimen with rectangular cross section which is regular throughout. It is computed as follows,
Cross breaking strength ¼
150WL BD2
W = load at failure L = gauge length in mm B = mean width of specimen D = mean thickness of specimen in mm 4.1.4. Shear testing The vertical shear force acts on the brake pads during braking. For safety braking operation, the brake pads must be resistant to shear force. Shear testing is used to determine the resistance of the brake pad and the back plate against the shear force. The shear test is carried out according to ISO 6312. 4.2. Physical testing 4.2.1. Porosity In automotive brake pad application, main function of porosity is to absorb energy and heat. This is important for effectiveness of braking system. The review shows that higher friction coefficient and wear rate because of higher contact areas between mating surfaces because of the lower porosity. Brake pad should have certain amount of porosity to minimize the effect of water and oil on friction coefficient.[12,13].
Theoretical density Experimental density 100 Porosity ¼ Theoretical density 4.2.2. Density test Archimedes’s principle is used to determine the volume of body which is in any shapes. Therefore, the density of an irregularly shaped object is calculated by measuring its mass in air and submerged in water. The density is expressed in equation
Density ¼
Weight in air Volume of water displaced
4.2.3. Specific gravity The specific gravity computed as follows, [5]
Specific gravity ¼
Wa Wa Wb
4.3.1. Acetone extract
The percentage of acetone extract ¼
W3 W2 100 W1
where W1 = weight of specimen in gram, W2 = weight of empty crucible in gram W3 = Weight of crucible + extract in gram 4.4. Thermal analysis Thermal analysis is carried out to study thermal behavior of brake pad at highest temperature. 4.4.1. Heat swell Heat produced when brake applied can make a brake pad in swell and can create performance deterioration problem. Heat swelling of sample is carried out according to SAEJ160. The sample cut in to the 10 mm 10 mm 5 mm size and thickness was measured at six places accurately, then sample was heated at 200 °C in the muffle furnace for two hours. The thickness was measured of heated sample [5].
% of Heat Swelling ¼
Tf Ti 100 Tf
where Tf – Final Thickness. Ti – Initial Thickness. 4.4.2. Thermo Gravimetric analysis Differential Thermo Gravimetric Analyzer is used for checking weight loss with respect to rise in temperature for raw material and finished product. TGA analysis will exactly point out decomposition temperature of individual raw material used in formulation. 4.4.3. Thermal conductivity (TC) Thermal conductivity of a friction material is dependent on various factors, including type and amount of fillers, processing technique, etc. and operating parameters such as temperature, method used for measurement sample size etc. With the increase in temperature TC decreases. No two friction materials can have identical thermo-physical characteristics.
where Wa – weight of specimen in air in gram. Wb – weight of specimen in water in gram. 4.2.4. Water absorption According to ASTM 570-98, the specimen is prepared and weight is done. For 24 h the sample are kept dipping in water. Then percentage of water absorbed is calculated from following relation,
5. Brake performance characteristics testing (Brake inertia dynamometer Test) The performance characteristics will be carried out on a suitable brake performance test rig. As shown in Fig. 1 the performance of brake lining is evaluated using chase dynamometer which gives results about actual behaviour of brake pad by observing parameters such as brake efficiency, stopping distance and brake fade temperature
Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703
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S.P. Jadhav, S.H. Sawant / Materials Today: Proceedings xxx (xxxx) xxx
8. Conclusion
Fig. 1. Schematic representation of the brake pad test rig. Part list - fig a. Brake pedal-1, Brake Booster-2, Brake Fluid Reservior, Thermocouple-4, Brake Caliper Assembly-5, Brake Pad-6, Main Drive Shaft-7, Step Pulley-8, Flywheel Weight-9, Brake Disk-10, Electric Motor-11.
This literature review focuses on bad effect of non exhaust emission on human health and environment. The researchers are also, studied its adverse effect on plants. Review papers shows that brake pads are manufactured by different natural ingredients and compares their results with traditional one. Some of researchers manufacture brake pad by the compression moldings and powder metallurgy method. Wear rate and coefficient of friction are found using Pin on disc apparatus. Performance of brake pad is tested using chase dynamometer. SEM Method is used to study morphology of brake pad specimen. There is wide scope to replace the metals by studying and characterizing natural materials and its ingredients. To minimize health and environment issues, novel material is developed with highest percentage of natural ingredients and the brake pad manufacturer must follow the regulations which are made by different countries in accordance with the percentage of metallic elements while manufacturing brake pad. References
Fig. 2. Schematic diagram of pin on disc apparatus. Part list- fig.b. Input Weight-1, Weight Holder-2, Vertical Adjuster-3, Horizontal Adjuster-4, Disk (Hardened)-5, Bearing-6, Chuck-7, Specimen-8, Shaft-9, Frequency Inveter-10, Rotating Shaft-11, Pulley-12&13, Belt-14, Bearing-15, Motor and Gear-16.
6. Tribological testing This will be done on pin on disc apparatus as shown in Fig. 2. The tribological behaviour of brake lining material is checked using pin on disc apparatus which give result about coefficient friction, wear rate at variable speed, different load condition and different sliding distances. 7. SEM-EDX analysis SEM images can help us to observe distribution of grain structure and surface defects. That is useful to optimize research processes, perform better analysis and save valuable time. The manufacturing defects are also identified and studied by SEM images.
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Please cite this article as: S. P. Jadhav and S. H. Sawant, A review paper: Development of novel friction material for vehicle brake pad application to minimize environmental and health issues, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.06.703