Introduction

The brake pad is the most far-reaching research and development in an automobile, from classic to modern electric vehicles. The brake pad or friction lining material is the safety and security part of any vehicle. The brake pad contains binder, reinforcement, filler, abrasives, and lubricants to fabricate the friction material. These are very helpful in making the friction material more efficient, high thermal distribution, and enhancing the tribological property [1,2,3]. Generally, non-asbestos composites are widely used as brake pad material, because it does not contain any carcinogenic substance. This composite has good mechanical, thermal and tribological properties [4, 5]. On the other hand, the disc is also the most crucial part of the braking system. The disc's primary property is the good load-bearing capability and quick temperature distribution to the surroundings [6, 7]. The contact region between the brake pad and disc material produces higher heat during braking because of friction. Due to that, it affects the braking performance [8, 9]. The higher temperature at the contact interface region causes thermoelastic instability, known as thermal distortion [10]. Engineers are still developing and modifying the brake pad geometries, disc profiles and material properties to enhance the thermal distribution [11, 12]. The heat generation between the contact interface region increases the wear rate of the brake pad material; measuring the brake pad temperature at the sliding area is difficult [13, 14]. The pin-on-disc tribometer is one of the standard methods to test the brake pad and disc material [15, 16]. It is important to note that the "temperature" has a unique status when discussing friction-induced temperature fields. However, in real-world applications, determining the temperature at the friction-induced zone is difficult and time-consuming [17]. Researchers found a solution to measure the friction zone's temperature by using the finite element analysis method.

The thermal–mechanical approach through the finite element method is to investigate the thermal behaviour of the brake pad during the sliding test. The researchers simulate the steel pin and friction disc to test this thermomechanical approach using ANSYS. The sliding region between the brake pad and disc has a surface-to-surface contact. This contact type has covered large sliding areas and allows the two contact bodies to measure the temperature at each nodal point. The temperature results agree with experimental temperature results [18]. The transient temperature analysis has another approach to measure the temperature distribution of the disc and pad material using ANSYS. There is a higher temperature distribution variation in the radial direction due to the loss of heat through convection. The circumferential surface is always hot at all nodal points because of the repeated sliding of the brake pad over the disc [19]. The temperature distribution of the organic friction material against ceramic disc material was investigated by the finite element method using ABAQUS. The input conditions, viz., friction coefficient, thermal conductivity, heat flux, and heat flow, play a significant role in this numerical approach [20]. A three-dimensional brake pad and disc model was analysed using the ABAQUS numerical approach to predict the hot-spot (high thermal points) mechanism under severe braking conditions [21]. The temperature distribution of the brake pad was measured by applying the analytical frictional heat generation function using numerical analysis. [22]. The temperature distribution of the brake pad against the disc is analysed with the help of the COMSOL Multiphysics software. In order to simulate the model using this software, the material properties and processing parameters are given as input [23].

Experimental measurements of temperature at the friction-induced zones and the temperature distribution are difficult [24, 25]. ANSYS and COMSOL software were successfully used to predict the temperature at the interface and the temperature distribution [26, 27].

Various parameter variation used in the current studies are as follows: Disc temperature varied from 25°, 170°, 200°, 250° and 300 °C. The following two materials are used: ceramic (zirconia) composite and non-asbestos organic material.

In the literature reviewed, the interface contact region temperature and thermal distribution of the brake pad (Pin) material have not been carried out by the transient thermal analysis numerical approach. The work differences between the simulation work done by literature and current work are as follows:

  1. (i)

    The pin-on-disc test using ANSYS is conducted to predict the interface temperature and temperature distribution of the brake pad material at the end of sliding test.

  2. (ii)

    The thermal distribution of the pin material up to a distance of 4 mm and 6 mm away from the disc surface is measured.

  3. (iii)

    The simulation results are compared with the experimental results collected from the literature.

  4. (iv)

    A non-asbestos material is tested in this simulation.

Experimental Study of a Friction Material

An experimental approach investigated a polymer matrix composite (pin material) brake pad against a pearlitic–bainitic grey cast iron disc to determine the friction coefficient and temperature distribution [28]. The constituent of the brake pad material and weight percentages are listed in Table 1.

Table 1 Elemental Composition and weight percentage of the brake pad composite material [28]
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The dimension of disc material is 63 mm in diameter and 6 mm thick, while the cylindrical pin material (brake pad) is 5.5 mm in diameter and 7.7 mm in height. The cast iron disc was mounted to the disc adaptor, which was coated in black to increase heat conduction. The brake pad material has a density of 2.27 g/cm3. When conducting the sliding test, the temperatures of the cast iron discs are maintained at 25 °C, 170 °C, 200 °C, 250 °C, and 300 °C. The literature data suggest the following sliding test conditions: contact pressure 2 MPa, sliding speed 1.31 m/s, total sliding distance 4000 m, and test duration 50 min. The disc temperatures are chosen based on the thermogravimetric analysis of the brake pad material. According to the TGA results, the friction material experiences a significant amount of mass loss between 170 and 375 °C, as indicated by the appearance of a broader exothermic peak in this temperature range. The tribometer result reveals that the friction coefficient of the pin material varied at different temperatures of 25 °C, 170 °C, 200 °C, 250 °C and 300 °C, as shown in Table 2. At a disc temperature of 300 °C, a friction coefficient in the range of 0.47–0.59 was reported. This is because a higher temperature increases the friction coefficient during sliding. In addition, the sliding test continued even after 300 °C, but the brake pad material had degraded significantly, and the wear rate increased.

Table 2 Range of friction coefficient values after the run-in stage [28]
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Figure 1a and b show the temperature of the pin material that was measured using a thermocouple placed at 4 mm and 6 mm away from the contact region between the pin and disc. The disc was heated to 25 °C, 170 °C, 200 °C, 250 °C, and 300 °C before the sliding test. The temperature results reveal that the pin temperature at the initial condition was 25 °C at T1(25 °C), 60 °C at T1(170 °C), 60 °C at T1(200 °C), 90 °C at T1(250 °C) and 105 °C at T1(300 °C) disc temperature. It was typically higher than the ambient condition because the heat was transferred from the disc material to the pin material before the sliding test began. After the sliding test of 4000 m, the pin temperature increases significantly up to 30 °C, 65 °C, 75 °C, 100 °C and 130 °C, as seen in Fig. 1a. Likewise, the disc temperatures of T2(25 °C), T2(170 °C), T2(200 °C), T2(300 °C) and T2(300 °C) have increased pin temperature at 6 mm to 30 °C, 65 °C, 75 °C, 100 °C and 135 °C compared to the initial pin temperature of 25 °C, 60 °C, 65 °C, 95 °C and 110 °C, as seen in Fig. 1b. However, the pin temperature at 6 mm shows less temperature variation than the temperature at 4 mm before and after the sliding test.

Fig. 1
figure 1

The temperature of the friction material at 4 mm (a) and 6 mm (b) away from the disc surface [28]

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Finite Element Modelling and Simulation

Density and Thermal Properties

The pin specimen of the friction material and grey cast iron disc is modelled by the Creo Parametric 7.0 academic version design software. The density and thermal properties of the friction and disc material are shown in Table 3. The specific heat and thermal conductivity of the friction material are calculated mathematically. The pin-on-disc Creo model is imported to ANSYS 2022 R2 academic version software to simulate the pin and disc temperature distribution by the transient thermal analysis method. The simulation procedure is adopted from work done by literature [29].

Table 3 The density and thermal properties of the pin and disc components
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Mesh

In the finite element solver, the mesh is the crucial step for getting accurate results. The pin-on-disc model meshed into elements and nodes, as shown in Fig. 2. In the mesh model, the element order is linear, and the element types used are SOLID70, CONTA174, and SURF152. The element sizes of the pin and disc are 0.5 mm and 1 mm. The element quality of the fine mesh for the pin and disc is 0.99 max. The mesh model consists of 52,249 nodes and 54,147 elements.

Fig. 2
figure 2

The mesh model of the pin and disc

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Boundary Conditions

The pin-on-disc model is prepared for further analysis by first applying boundary conditions. The applied conditions are frictional contact between the pin and disc, simulation time, thermal flux, convection and disc temperature. The following five different disc temperatures are used for the simulation: 25 °C, 170 °C, 200 °C, 250 °C, and 300 °C. The temperature below the disc adapter is insulated because of the convection problem. The total sliding test time is set as 3053 s, corresponding to the total sliding distance of 4000 m. The following formula calculated the thermal flux load of the composite material:

$$q_{{{\text{disc}}}} \left( t \right) = \mu \left( t \right)pv\frac{{A_{{{\text{pin}}}} }}{{A_{{{\text{disc}}}} }}$$

where μ(t) is the experimental friction coefficient recorded as a function of time t, p is the nominal contact pressure, v is the sliding speed, Adisc is the nominal contact area of the disc, and Apin is the nominal contact area of the pin.

The thermal flux load of 1.057 × 10–2 W/mm2 is applied to the disc material. The heat convection value of 1.85 × 10–6 W/mm2 °C of the brake pad composite material is determined using the heat convection formula and applied to the cylindrical pin surface, as illustrated in Fig. 3.

Fig. 3
figure 3

The boundary conditions of the pin-on-disc

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Results and Discussion

Results of Transient Thermal Simulation of Ceramic Composite Pin Material

Figures 4a–e show the temperature distribution of the pin and disc at the end of the simulation. Figure 4a shows that the maximum temperature obtained at the end of the simulation is 31.38 °C. During the sliding test, the friction heat is generated between the contacting bodies and the temperature is increased. Figure 4b shows that the maximum temperature is 175.98 °C, which is higher than the applied disc temperature of 170 °C. The reason for the higher temperature is due to the frictional heat caused by the repetitive sliding motion of the pin material over the disc surface. Similarly, the disc temperatures of 200 °C, 250 °C and 300 °C are increased to 205.98 °C, 256.64 °C and 307.85 °C, as seen in Figs. 4(c) to 4(e). The pin material shows minimum temperatures of 25 °C, 36.11 °C, 38.43 C, 41.85 °C and 40.36 °C, respectively. The construction geometry path tool measures the temperature distribution of the pin material and the interface region temperature.

Fig. 4
figure 4

a–e Temperature distribution of the ceramic composite brake pad at the end of the simulation test as a function of disc temperature

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Figures 5a–e show the temperature distribution of the pin material at a distance of 4 mm and 6 mm (thermocouple points) from the disc surface. Signifier 1 indicates the interface temperature between the pin and disc. Signifier 2 indicates the thermocouple positioned at a distance of 4 mm and 6 mm. Figure 5a shows that the temperature distribution of the pin material at an applied disc temperature of 25 °C. After being subjected to a sliding test, the interface temperature is found to be 30.22 °C (Signifier 1). This is because the friction generated between the disc and pin causes the interface region to heat up during the sliding motion. Nonetheless, the temperature of the pin material is lower at a distance of 6 mm which is 25.99 °C and at 4 mm is 26.83 °C (signifier 2), as seen in Fig. 5a, i and a, ii. Figure 5b shows the temperature at the interface region as 174.78 °C, which is indicated as 1. It is higher than the applied disc temperature of 170 °C. The pin temperature is decreased at a distance of 4 mm and 6 mm as 74.068 °C and 76.575 °C (signifier 2), because the heat is rapidly convected, as seen in Fig. 5b, i and b, ii. Likewise, Fig. 5c–e show that the maximum temperature at the interface region is 204.76 °C, 255.26 °C, and 306.23 °C for the disc temperatures of 200 °C, 250 °C, and 300 °C, respectively. Figure 5c, i–e, i show the pin temperature at 6 mm has a temperature of 86.57 °C, 103.42 °C, and 123.89 °C, which has a comparatively significant temperature variation than the pin temperature at 4 mm, as seen in Fig. 5c, ii–e, ii.

Fig. 5
figure 5

a–e Pin temperature distribution of the ceramic composite i distance of 6 mm ii distance of 4 mm from the disc surface

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Figure 6 shows the temperature distribution of the pin material up to a distance of 4 mm and 6 mm in steps of 1 mm variation for different disc surface temperatures. After the sliding test, the interface region temperature (at 0 mm) between the pin and disc is 30.37 °C, 174.78 °C, 204.76 °C, 255.26 °C, and 306.23 °C, respectively. The interface temperature is gradually distributed to the pin material. At a distance of 4 mm, the thermocouple temperature is 26.83 °C, 76.57 °C, 86.95 °C, 104.13 °C and 123.89 °C, as seen in Fig. 6a. Similarly, the pin temperature at 6 mm is 25.99 °C, 74.06 °C, 86.57 °C, 103.42 °C, and 123.23 °C, as seen in Fig. 6b. There is less variation in pin temperature at 6 mm compared to 4 mm.

Fig. 6
figure 6

The temperature distribution of the pin material from the interface temperature to the thermocouple point of a 4 mm and b 6 mm as a function of disc temperature

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Comparison of Experimental and Simulation Results of Ceramic Composite Pin Material

Figure 7a and b show the comparison between the simulation and experimental temperature of the pin material at 4 mm and 6 mm away from the disc surface for different disc temperatures. Figure 1a and b show the experimental pin temperatures at 4 mm and 6 mm after the sliding test of 4000 m at varying disc temperatures. For the disc temperatures of 25 °C, 250 °C, and 300 °C, it is clear that the simulation temperature is in good agreement with the experimental temperature, as seen in Fig. 7a. Likewise, the simulation pin temperature at 6 mm closely agrees with the experimental temperature, as seen in Fig. 7b.

Fig. 7
figure 7

a The comparison of the simulation and experimental temperature of the pin material at 4 mm. b The comparison of the simulation and experimental temperature of the pin material at 6 mm

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Results of Transient Thermal Simulation of Non-asbestos Composite Pin Material

Figure 8a–e show the results of the temperature of the pin and disc after the simulated sliding test of the non-asbestos brake pad material. Figure 8a and b show that the maximum temperature is 33.38 °C and 178.18 °C. This is because the friction heat is generated between the two contact surfaces during the sliding test. Similarly, the disc temperatures of 200 °C, 250 °C and 300 °C are increased to 208.88 °C, 258.64 °C and 306.44 °C, as seen in Fig. 8c–e. The minimum temperature of the pin is 25 °C, 38.21 °C, 48.44 °C, 81.45 °C and 46.61 °C, respectively. Figure 9a–e show the temperature distribution of the non-asbestos pin material up to the distance of 4 mm and 6 mm (thermocouple points) from the disc surface. Non-asbestos organic pin temperature at 4 mm and 6 mm has higher thermal distribution than the ceramic composite pin material.

Fig. 8
figure 8

a–e Temperature distribution of non-asbestos material at the end of the simulation test as a function of disc temperature

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Fig. 9
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a–e Pin temperature distribution of the non-asbestos material i distance of 6 mm ii distance of 4 mm from the disc surface

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Conclusion

The finite element analysis is performed on a brake pad friction material (Pin) as a function of different disc temperatures of 25 °C, 170 °C, 200 °C, 250 °C and 300 °C using ANSYS software.

  • The transient thermal analysis is successfully performed to predict the interface temperature and temperature distribution of the brake pad (pin) materials.

  • The interface temperature between the pin and disc is significantly higher than the applied disc temperature due to friction heat.

  • The results of the simulated temperature of the pin material are in close agreement with the experimental results of the temperature collected from the literature.

  • The results of transient thermal simulation of non-asbestos composite pin material are presented.

  • The simulation helps researchers to predict the temperature at the interface between the pin and disc, which is difficult to measure experimentally.