Design and Simulation of Banana Pseudo-stem Fibre Extracting Raspador (Cylinder) Using FEA Technique

ABSTRACT

Development of mechanical fiber extractors without considering engineering knowledge can cause failures of the machine’s components during operations. Therefore, the present study was conducted to examine the structural strength of the banana pseudo-stem fiber-extracting raspador using finite element analysis. For measuring the force required to extract the fibers, a measuring setup along with an embedded system was developed using the ATmega328P microcontroller, DYMH-103 load cell, and 24-Bit ATD converter, and it was found that an average of 99.09 N force was required to scratch the fibers from single pseudo-stem sheath. Three computer-aided design (CAD) models of raspador having tip angles of blades of 25°, 35°, and 45° were developed in the Creo-Parametric software and simulated in the Ansys® software using three material properties, i.e. high-carbon steel, medium-carbon steel, and low-carbon steel. The results of both static structural analysis and explicit dynamics simulation analysis suggested that the CAD model with 45° tip angle of blade having low-carbon steel has a higher value of total deformation and maximum principal stress and a comparatively lower value of equivalent elastic strain than other models and under the yield limit of the parent material. Hence, it may be used for the development of a prototype of a banana pseudo-stem fiber-extracting machine.

摘要

在不考虑工程知识的情况下开发机械纤维提取器可能会导致机器部件在操作过程中出现故障. 因此，本研究采用有限元分析方法对香蕉假茎纤维提取覆盆子的结构强度进行了检测. 为了测量提取纤维所需的力，使用ATmega328P微控制器、DYMH-103称重传感器和24位ATD转换器开发了一个测量装置和嵌入式系统，发现从单个伪茎鞘上刮取纤维平均需要99.09 N的力. 在Creo-参数化软件中开发了叶片尖端角度为25°、35°和45°的raspador的三个CAD模型，并在Ansys®软件中使用三种材料财产进行了模拟，即高碳钢、中碳钢和低碳钢. 静态结构分析和显式动力学仿真分析结果表明，在母材屈服极限下，低碳钢叶片45°顶角CAD模型的总变形和最大主应力值高于其他模型，等效弹性应变值相对较低. 因此，它可以用于开发香蕉假茎纤维提取机的原型

KEYWORDS:

• CAD
• total deformation
• maximum principal stress
• banana pseudo-stem
• static structural analysis
• explicit dynamics structural analysis

关键词:

• 总变形
• 最大主应力
• 香蕉假茎
• 静态结构分析
• 显式动力学结构分析

Introduction

Banana (Musa paradisiaca) is a perennial monocotyledonous annual plant mainly cultivated for its fruits (Sango et al. 2018). It is a native crop of Southeast Asia’s Malaysian–Indonesian region and is widely cultivated in the tropical and subtropical regions of the world (Aziz et al. 2011). Presently, it is cultivated in 129 countries throughout the globe and is the fourth-largest steady food crop in the world (Patel and Patel 2022). In India, banana is grown in approximately 0.87 million hectares of an area which shares 15.5% of the global cultivated area under the crop. In 2020–21, the production of bananas is approximately 31.5 million tonnes with a productivity of 35.185 tonnes/ha (FAOSTAT 2021).

Banana has not only been exploited for their fruits but also for peels, leaves, pseudo-stem, and inflorescence for various food and nonfood applications (Padam et al. 2014). Besides that, Ahmad and Danish (2018) studied that approximately 220 tonnes of banana waste (pseudo-stems) produced from 1 hectare of the farm is usually left by the farmers in plantation soil to be used as organic material or dumped into rivers and lakes or burnt down. If these wastes are not correctly handled, environmental issues may occur, as these wastes may emit hazardous greenhouse gases that may harm the environment (Padam et al. 2014). To address the issue, various researchers have worked on the possible application of banana pseudo-stem and reported that they can be effectively utilized for the production of fibers for textiles (Cecci et al. 2020; Monzón et al. 2019; Ortega et al. 2016), pulp and paper (Díaz et al. 2021), cellulose (Cherian et al. 2008), and structural reinforcements in composites (Ortega et al. 2010, 2013) due to their high heat resistance, water resistance, fire resistance, and greaseproof properties (Ortega et al. 2020; Vigneswaran et al. 2015). These fibers also have good tensile strength and can be blended with other natural fibers for diversified product development. In addition to this, the increasing cost of synthetic fibers like glass, carbon, plastics, asbestos, etc., in the international market and the health risks caused during their manufacturing and processing (Diarsa and Gupte 2021) can make the banana fiber a flattering and appealing option for synthetic fibers because of their renewability, recyclability, economic effectiveness, and environmental friendliness.

It was also reported that approximately 400 kg fibers per hectare can be extracted from the banana pseudo-stem waste and can help to create Rs. 3000–4000 crores of the market in the Indian fiber sector (Paramasivam et al. 2022). However, due to a lack of awareness about the extraction of fiber and post-harvesting technology, only 10% or less of the banana waste (pseudo-stems) is extracted for fiber (Elayaperumal 2016).

The fiber from banana pseudo-stem can be extracted either by manual or by mechanical methods. The manual method entails scraping the upper layer with a blunt edge, followed by washing it with water and drying it. Although it produces high-quality fiber, it is laborious, tedious, time-consuming, and has less fiber yield (500 grams per person per day) method. To avoid fiber loss, the fiber should be extracted within 24 hours of harvesting. This could be averted by a mechanical method of extraction as it is a highly efficient technique that can produce a large quantity of high-quality fiber in a short time. The plant-based natural fibers are extracted from different parts of the plant, i.e., banana fiber from pseudo-stem, pineapple leaf fiber from leaf, and flax/jute from stalks. Therefore, these plant-based fiber requires different principles for extraction also, i.e., banana by scratching and beating, pineapple leaf fiber by scraping, and flax/jute by scutching. In addition to this, banana pseudo-stem contains a moisture content in the range of 88–96% which is the highest among various natural fibers (Balakrishnan, Wickramasinghe, and Wijayapala 2021; Li et al. 2010); hence, it is very difficult to extract the banana pseudo-stem fiber with existing bast fiber extractors. Therefore, there is a need to develop a specially designed extractor that can solve the purpose of fiber extraction from banana pseudo-stem.

Generally, mechanical fiber extractors work under a high level of compressive, shear, and impact force conditions. Also, these machines have potentially dangerous moving parts, which can cause serious or fatal injuries to the operator. Insufficient or lack of engineering and technical knowledge can cause breakdowns and failures of the machine’s components during field operations. Hence, the constituent elements of such machines must be reliable and durable enough that can sustain the extreme external forces during operations. Therefore, it is very important for the designers and agricultural machinery manufacturers to predict deformation and structural stress distributions on the machine elements during operations, which will allow them to optimize the manufacturing parameters by using predicted knowledge (Topakci et al. 2010). As a result of technological advancement in the field of computers and software, the solution of complicated design problems using computer-aided design (CAD) technology and numerical methods in a virtual way is possible without developing the physical models for assisting the possible usage or material failure. Although some engineering problems can be solved using analytical methods and/or experimental methods, some problems are too complicated or too large to be solved. Hence, engineers refer to numerical methods to obtain approximate solutions for their large-scale and complicated problems. One of these most powerful numerical techniques is the Finite Element Analysis (FEA) or Finite Element Method (FEM), which has huge usage in the area of mechanical design and in the manufacturing industry. It is a numerical computation approach that estimates the differential or integral equation that is too hard to solve analytically. FEM divides the complex problem into smaller elements to solve its simplified equations and then partial solutions are summarized to obtain approximates (Salarikia et al. 2017).

In the past, various researchers employed the FEA technique to simulate or analyze the mechanical behavior of agricultural machines. Recently, some researchers also employed this technique in the field of natural fibers. Olan et al. (2020) used the FEA/FEM for constructive optimization of hemp fiber processing equipment, and Karim et al. (2021) used it for analyzing the strength of extracting rollers of jute fiber extraction machine. Oreko et al. (2018) designed and developed a prototype of a plantain (pseudo-stem) fiber extraction machine using FEA. In this study, they simulated the rolling drum (raspador) of the prototype for selecting the material for fabrication. Shinde, Magade, and Magade (2022) also designed and simulated the frame of a banana fiber extraction machine using static structural analysis under FEA in Ansys software. Sri and Ankitha (2020) also conducted a structural analysis of various components of a conceptualized model of a banana fiber extraction machine to check the feasibility of the material for the fabrication. But no work was found on the design and simulation of banana pseudo-stem fiber extracting raspador using dynamic structural analysis. Hence, the present study was undertaken with the objectives of design and simulation of banana fiber extracting raspador (cylinder) using Finite Element Analysis for both static and dynamic optimization of the design parameter and material of fabrication for the development of a prototype. The present study was conducted with the aim to assist the design engineers and machine manufacturers in upscaling machine production with less input cost through FEA technique. The study will also help the machine manufacturers to optimize the force acting between the machine and banana pseudo-stem for producing a good quality of fiber for textile uses.

Materials and methods

For developing the banana pseudo-stem fiber extractor, knowledge about the various design and simulation parameters is required, but the force required to extract the fibers from the banana pseudo-stem sheath is most important. It helps in optimizing the various mechanical parameters of the raspador, i.e. diameter and length of the raspador, the number of blades on the periphery, material for construction, power required to operate the raspador, etc. Due to a lack of information devoted to the force required to extract the fibers from the banana pseudo-stem, this research was conducted in two steps: (1) development of a laboratory setup for measurement of the force required to scrap banana pseudo-stem sheath and (2) design and both static and dynamic simulation of the prototype using FEA.

Measurement of force required to extract the fibers from banana pseudo-stem sheath

A laboratory setup (Figure 1(a,b)) has been developed for measuring the force required to extract the fibers from the banana pseudo-stem sheaths. The developed setup consists of the frame, conveyor roller, conveyor trolley, scratching knife/blade, load cell, embedded data logging and displaying system, 12 Volt DC motor with power supply, and banana pseudo-stem sheath. There were two 12 Volt DC motors employed in the setup for the forward and rearward motion of the conveyor trolley. In the conveyor trolley, the scratching knife/blade and load cell were mounted with the help of a support arm whereas the sheath of the banana pseudo-stem of 1500 mm long was placed in the horizontal position with the help of two mounting clamps, as shown in Figure 1b.

Figure 1a. Isometric view of laboratory setup for the measurement of the force required to extract the fibers from banana pseudo-stem.

Figure 1b. Side view of laboratory setup for the measurement of the force required to extract the fibers from banana pseudo-stem.

For logging and displaying the force required to scratch the banana pseudo-stem, an embedded system was developed. For this purpose, an electrical circuit of the embedded system was designed and simulated in the Proteus 8 professional software (Figure 2). The developed system consists of the ATmega328P microcontroller board (Arduino UNO), a DYMH-103 Load Cell (100 kg load carrying capacity), a 24-Bit Analog-to-Digital Converter (HX711), 2N2905 PNP transistor, 16 × 2 LCD display, and 12 Volt power supply. For logging and displaying the readings, an algorithm was written in C⁺⁺ and uploaded on the microcontroller.

Figure 2. Circuit diagram for the measurement of the force required to extract the fibers from banana pseudo-stem.

After initializing the microcontroller and calibration of the load cell (Figure 3(a,b)), conveyor trolley was moved forward with the help of a 12-Volt DC motor and power supply. As the sharp edge of the scratching knife/blade comes in contact with the banana pseudo-stem and starts the scratching of fibers, some amount of force was experienced by the load cell mounted in a series with the scratching knife/blade. This force experienced by the load cell in terms of analog readings was converted into digital readings with the help of an algorithm uploaded on the microcontroller through A-D Converter. Finally, the digital output was retrieved with the help of RS232 software and displayed on the LCD screen. The various physical properties of the selected banana pseudo-stem and parameter for testing the measuring setup are presented in Table 1.

Figure 3a. Calibration curve for load cell.

Figure 3b. Calibration curve for load cell.

Table 1. Physical properties of the selected banana pseudo-stem and parameter for testing the measuring setup.

S.N.	Parameter	Value
Physical properties of the selected banana pseudo-stem
1	Average length of whole stem	2670 mm
2	Average weight of whole stem	37.5 kg
3	Average diameter of whole stem (basal end)	213 mm
4	Average diameter of whole stem (top end)	153 mm
5	Average number of sheaths on the whole stem	22
6	Moisture content (wet basis)	91%
Parameter for testing
1	Test duration	20 s
2	Test speed	0.07 m/s
3	Number of tests	3

Design consideration of banana fibre extracting raspador (cylinder)

The main principle of operation of banana fiber extracting raspador is shown in Figure 4. The scratching knives/blades mounted on the periphery of the raspador applies the impact force on the sheath of the banana pseudo-stem to scrap the pulpy material for extracting the fibers. When a banana pseudo-stem sheath is inserted between the raspador blades, the scratching knife/blade progressively scratches the sheath at closely spaced intervals and chips it off against the base plate by beating principle. This beating cum scratching action continues as the sheath is still inside the raspador. Due to the impact force of blades, the parenchyma cells and vascular tissues of the sheath are softened and pulpy material is scrapped away and finally the fibrous material is revealed.

Figure 4. Working principle of banana pseudo-stem fiber-extracting raspador (cylinder).

In order to obtain effective fiber-extracting performance, the raspador (cylinder) should have some standard rotational speed which generates angular momentum at the tip of blade to scrap the pulpy material from sheath of banana pseudo-stem. Ahmad et al. (2017) suggested Equation 1 to determine the angular momentum developed at the tip of the blade.

(1) ${\mathrm{\Delta }}_{\mathit{\omega }}={\mathit{M}}_{\mathit{r}}{\mathit{v}}_{\mathit{t}}\left({\mathit{D}}_{\mathit{r}}/2\right)$(1)

where ${\mathrm{\Delta }}_{\omega }$ = angular momentum (kg · m²/s), $M_r$ = mass of raspador (kg), $v_t$ = linear velocity of the blade tip (m/s), and $D_r$ = diameter of the raspador from origin to blade tip (m).

The assessment of quantity of material extracted from banana pseudo-stem is another important parameter for designing the raspador. The length of the raspador and pitch of the scratching blade are used to represent the quantity of material scratched off at every cycle. For this purpose, Equations 2 and 3, as suggested by Snyder et al. (2006) and Ahmad et al. (2017), were used.

(2) ${\mathit{L}}_{\mathit{c}}=\hspace{0.17em}\frac{\mathit{q}}{\mathit{\mu }\mathit{\eta }\mathit{\rho }\mathit{\alpha }}$(2)

where $L_c$= length of cylinder, (m), $q$ = material feed rate; (kg/s), $\mu$= thickness of the plant mass layer at the entrance in meter, $\eta$ = coefficient of cylinder length utilization (0.7–0.8), $\rho$ = bulk density of banana pseudo-stem, and $\alpha$ = velocity of plant mass entering (1–2 m/s assumed).

(3) ${\mathit{L}}_{\mathit{p}}=\hspace{0.17em}\frac{2\mathit{\pi }{\mathit{v}}_{\mathit{f}}\hspace{0.17em}}{{\mathrm{\Delta }}_{\mathit{\omega }}\mathit{N}}$(3)

where $L_p$ = pitch of the blade for extraction of fiber (m), $v_f$ = feed velocity of leaf (m/s), ${\mathrm{\Delta }}_{\mathit{\omega }}$ = angular speed of raspador (rad/s), and $N$ = number of blades on the periphery of raspador.

Finally, the power required to operate the raspador for extracting process was determined using Equation 4 (Ahmad et al. 2017; Snyder et al. 2006).

(4) ${\mathit{P}}_{\mathit{e}}=\hspace{0.17em}\frac{\mathit{\pi }{\mathit{D}}_{\mathit{r}}\mathit{N}{\mathit{F}}_{\mathit{s}}\mathit{S}\mathit{i}\mathit{n}\varphi }{60}$(4)

where $P_e$ = power required for extraction (kW), $D_r$ = diameter of the raspador from origin to blade tip (m), $N$ = revolution per minute of the raspador (rpm), $F_s$ = force required to scratch the fibrous material from banana pseudo-stem, and $\varphi$ = angle between the scratching blade force and banana pseudo-stem while extraction process is in progress (N). As scratching blade and banana pseudo-stem were kept at right angle position during the laboratory testing (Figure 1), $Sin{90}^{\circ }=1$was taken as the assumption for computing the power requirement.

Finite element analysis of the raspador

The FEA was set up to simulate the deformation behavior and equivalent stress distribution on the raspador (cylinder) under uniformly distributed load conditions. For this purpose, static structural (SS) and explicit dynamics (ED) simulation functions were selected and performed under the FEM analysis in Ansys_® Workbench software. To select the appropriate material and tip angle of the scratching blade with the highest structural strength, three materials and three CAD models with different tip angles of the scratching blade were optimized for simulation, as presented in Table 2.

Table 2. Selection of material and CAD models for simulation.

Material	CAD models with tip angle
M1 – high-carbon steel	CAD-α1 – CAD models with 25° tip angle of scratching blade
M2 – medium-carbon steel	CAD-α2 – CAD models with 35° tip angle of scratching blade
M3 – low-carbon steel	CAD-α3 – CAD models with 45° tip angle of scratching blade

CAD models of raspador

On the basis of theoretical design, three CAD models of raspador were developed in the Creo Parametric 7.0 software (Figure 6). The raspador mainly consists the scratching blade, flange, and axle, as shown in Figure 5. The two flanges were fixed at a distance of 366.5 mm to support the eight blades on its periphery.

Figure 5. Isometric and plan view of the banana pseudo-stem fiber extracting raspador.

Figure 6. 3D-CAD models of the raspador with different tip angles of scratching knife/blade.

Mechanical properties of the materials used for simulations

The libraries of selected materials (Table 3) were created in the Ansys_® workbench software for applying the material on the raspador model, as these kinds of materials are normally used by the agricultural and fiber extracting machine manufacturers; therefore, these materials were chosen for the simulations.

Table 3. Physical and mechanical properties of different materials used for simulation.

S. N.	Material	Properties
		Young’s modulus (E), GPa	Poisson’s ratio (ν)	Density (ρ), kg/m^3	Tensile yield strength, MPa	Tensile ultimate strength, MPa	Reference
1	Banana Pseudo-stem	3.49	0.25	1350	54	20	Venkateshwaran, Elayaperumal, and Sathiya (2012) and Masrol, Sudin, and Ibrahim (2013)
2	Low-carbon steel	210	0.3	7850	320	400	Norton (2006) and Chapman (1972)
3	High-carbon steel	200	0.3	7850	525	685	Norton (2006) and Chapman (1972)
4	Medium-carbon steel	210	0.3	7850	345	550	Norton (2006) and Chapman (1972)

Static structural analysis (SSA)

Mesh convergence

After creating the materials library, the developed 3D geometry of the raspador was defined using the parametric geometry modeler feature. The main advantage of this feature is that existing geometry that was created in any other format can be easily modified. After that, mesh convergence was performed using the default meshing option (20-noded hexahedral element geometry) to verify the numerical analysis reliability of the raspador, as shown in Figure 7a. For mesh convergence analysis, the following three steps were performed: (i) generation of the mesh by using the least number of elements, (ii) re-meshing of models by considering the elements’ refinement, and also re-analyze and compare the results with previous meshes, and (iii) re-analyzing of models by changing the mesh density until results are satisfactorily converged. The total number of nodes and elements analyzed by the default meshing option for describing the raspador were 12,726 and 6138, respectively.

Figure 7. (a) Mesh convergence using static structural analysis; (b) mesh convergence using explicit dynamic structural analysis in the Ansys_®.

Boundary conditions and load application

In order to appropriately analyze the structural strength and the effect of tip angle of scratching blade on raspador, boundary condition was applied in simulation models to apply the load. Both flanges of the raspador were fixed as boundary and uniformly distributed load (UDL) was applied on the periphery of the raspador, and results were drawn for analyzing the total deformation, maximum principal stress, and equivalent elastic strain.

Explicit dynamics structural analysis (EDSA)

The explicit dynamic structural analysis was performed to assess the raspador (cylinder) behavior for short-duration loading or impact of force. The material of construction, support structure, force acting, and boundary conditions are alike as in static structural analysis. However, the number of steps of force acting was different. Analysis was conducted by considering three numbers of steps and an end time of 5.0 seconds. Further, the explicit time integration method (central difference method) was selected as the load step type following boundary conditions. The pattern of behavior was analyzed by the simulation results of total deformation, equivalent elastic stain, and maximum principal test.

Results and discussion

Force to extract the fibers from banana pseudo-stem sheath

The developed laboratory setup (Figure 1) was operated for a duration of 20 seconds in each run for measuring the force required to scratch the fibers from banana pseudo-stem sheath. The real-time graph of measured force is shown in Figure 8. The result shows that the developed embedded system shows the peak of force readings between 2 and 16 seconds, as the scratching blade was properly in contact with the pseudo-stem. During this period, the load cell of the developed embedded system experienced a force in the range of 94.35–100.72 N. Before and after this time period, the load cell provided readings close to zero, as the scratching blade was not in proper contact with the pseudo-stem. The test was conducted on 150 samples of banana pseudo-stem sheath of both outer and inner layers, and an average force of 97.18 N was observed. The test revealed that outer sheaths require a somewhat higher amount of force than inner sheaths for extracting the fiber due to the presence of less moisture content and a stronger surface. The average scratching force experienced by both the inner and outer sheath was observed as 96.27 N and 99.09 N, respectively. The difference between the two observed forces was very less and non-significant. Therefore, from the design safety point of view, the force experienced by the outer pseudo-stem sheath (99.09 N) was considered for simulation purposes as in this force, the inner banana pseudo-stem sheath would not be damaged excessively, affecting the quality of fiber.

Figure 8. Real-time graph of force required to scratch the banana pseudo-stem.

Finite element result

Total deformation

The FEM results of the total deformation of the raspador model of different tip angles of scratching blades with different materials are illustrated in Figures 9 and 10, respectively. For analyzing the total deformation, 300 N UDL (for extracting fiber from three pseudo-stem simultaneously) was applied on the periphery of the raspador and the simulation results of both static structural and explicit dynamic tests are presented in Table 4. Both tests indicated that the deformation was changed with both the material and tip angles of the scratching blade. The results of both static structural and explicit dynamic simulation tests reveal that the low-carbon steel-based models show a higher value of deformation than medium-carbon steel and high-carbon steel-based models due to the difference in mechanical properties of each material. In each material category, deformation was decreasing with an increase in the tip angle due to the reduction in contact area between the point of force and tip of the blade. It was also analyzed that, in each raspador model, maximum deformation occurred at the center portion of the scratching blade but less than the yield limit of their respective materials (Norton 2006). Alemayehu et al. (2017) studied the characteristics of three carbon steels under quasi-static strain using FEM and found that the low-carbon steel has the maximum deformation. In this study, the overall maximum deformation was observed in the M₃-CADα1 (tip angle: 25° and material: low-carbon steel) raspador model in both the tests (SSA test: 3.29 e⁻⁰⁵ m and EDSA test: 7.71 e⁻⁰⁵ m), whereas the minimum value of 1.55 e⁻⁰⁵ m was found in M₁-CADα3 raspador model in SSA test and 6.07 e⁻⁰⁵ m was found in M₃-CADα3 raspador model in EDSA test, but the difference was significantly very less. The comparative results of both tests show that the deformation was under the yield limit of the material and less susceptible for the break or failure of the structure.

Figure 9. Total deformation on the raspador models under static structural analysis test.

Figure 10. Total deformation on the raspador models under explicit dynamic structural analysis test.

Table 4. Comparison of total deformation of raspador models with respect to material and tip angle of the blade in both static structural and explicit dynamic simulation tests.

Material	Total deformation, m
	Static structural test			Explicit dynamic test
	CADα1: CAD models with 25° tip angle	CADα2: CAD models with 35° tip angle	CADα3: CAD models with 45° tip angle	CADα1: CAD models with 25° tip angle	CADα2: CAD models with 35° tip angle	CADα3: CAD models with 45° tip angle
M1 – high-carbon steel	2.59 e^−05	2.07 e^−05	1.55 e^−05	6.99 e^−05	6.36 e^−05	6.18 e^−05
M2 – medium-carbon steel	3.11 e^−05	2.32 e^−05	2.05 e^−05	7.11 e^−05	6.31 e^−05	6.11 e^−05
M3 – low-carbon steel	3.29 e^−05	2.90 e^−05	2.48 e^−05	7.71 e^−05	7.00 e^−05	6.07 e^−05

Maximum principal stress

The static and dynamic simulation results for investigating the maximum principal stress are presented in Figures 11 and 12, respectively. Similar to total deformation, in both the test conditions, the highest value of maximum principal stress was also observed in the low-carbon steel-based models, and the lowest value was observed in case of high-carbon steel-based models, whereas in each material category, maximum principal stress was decreasing with an increase in the tip angle of the scratching blade. Table 5 shows that the maximum value of principal stress was found in the M₃-CAD-α1 raspador model (SSA test: 1.72 e⁰⁷ Pa and EDSA test: 8654.1 Pa), whereas minimum was found in M₁-CAD-α3 raspador model (SSA test: 5.46 e⁰⁶ and EDSA test: 5007.7 Pa) but less than the yield limit of the parent material.

Figure 11. Maximum principal stress on the raspador models under static structural analysis test.

Figure 12. Maximum principal stress on the raspador models under explicit dynamic structural analysis test.

Table 5. Comparison of maximum principal stress of raspador models with respect to material and tip angle of the blade in both static structural and explicit dynamic simulation tests.

Material	Maximum principal stress, Pa
	Static structural			Explicit dynamic simulation
	CAD-α1 – CAD models with 25° tip angle	CAD-α2 – CAD models with 35° tip angle	CAD-α3 – CAD models with 45° tip angle	CAD-α1 – CAD models with 25° tip angle	CAD-α2 – CAD models with 35° tip angle	CAD-α3 – CAD models with 45° tip angle
M1 – high-carbon steel	1.21 e^07	6.55 e^06	5.46 e^06	7714.0	6302.8	5007.7
M2 – medium-carbon steel	1.44 e^07	8.96 e^06	8.67 e^06	8057.6	7002.4	5857.7
M3 – low-carbon steel	1.72 e^07	1.44 e^07	9.52 e^07	8654.1	7419.4	6154.6

Equivalent elastic strain

The SSA and EDSA simulation results of the equivalent elastic strain (Figures 13 and14, respectively) show that the higher strain was observed in the high-carbon-steel-based models whereas a lower stain was observed in the low-carbon-steel-based models as it depends on Young’s modulus and percentage of carbon present in the material. Various studies show that the higher percentage of carbon in steel results in the higher value of strength as well as elastic strain and lower value of Young’s modulus of the steel (Karanjule, Bhamare, and Rao 2018; Okayasu, Shin, and Mizuno 2008). The FEM results show (Table 6) that in both the tests the maximum equivalent elastic strain was found in the M1-CAD-α1 raspador model (SSA test: 6.52 e⁻⁰⁵ m/m and ESDA test: 4.89 e⁻⁰⁸ m/m) and the minimum was found in M3-CAD-α3 raspador model (SSA test: 2.94 e⁻⁰⁵ m/m and ESDA test: 3.28 e⁻⁰⁸ m/m). In each material category, the lowest equivalent elastic strain was found in CAD models with 45° tip angle due to the increase in taper angle of contact between the point of force and tip of the blade.

Figure 13. Equivalent elastic strain on the raspador models under static structural analysis test.

Figure 14. Equivalent elastic strain on the raspador models under explicit dynamic structural analysis test.

Table 6. Comparison of equivalent elastic strain of raspador models with respect to material and tip angle of the blade in both static structural and explicit dynamic simulation test.

Material	Equivalent elastic strain, m/m
	Static structural test			Explicit dynamic test
	CAD-α1 – CAD models with 25° tip angle	CAD-α2 – CAD models with 35° tip angle	CAD-α3 – CAD models with 45° tip angle	CAD-α1 – CAD models with 25° tip angle	CAD-α2 – CAD models with 35° tip angle	CAD-α3 – CAD models with 45° tip angle
M1 – high-carbon steel	6.52 e^−05	5.43 e^−05	3.40 e^−05	4.89 e^−08	4.78 e^−08	4.17 e^−08
M2 – medium-carbon steel	4.59 e^−05	4.37 e^−05	3.73 e^−05	4.70 e^−08	4.10 e^−08	3.74 e^−08
M3 – low-carbon steel	3.26 e^−05	3.13 e^−05	2.94 e^−05	4.27 e^−08	3.37 e^−08	3.28 e^−08

On the basis of FEA results of both static structural and explicit dynamic simulation tests, it was evident that the low-carbon-steel-based models have relatively higher deformation and maximum principal stress than the high- and medium-carbon-steel-based models, because of the low tensile strength of the material (Serajzadeh and Mohammadzadeh 2007), but under the yield limit of the material to sustain the failure of the structure. Fan and Huang (2006) conducted a study to examine the deformation and fracture behavior of low-carbon, medium-carbon, and high-carbon steel in various in-situ tensile tests. They reported that the microstructure of carbon steel is mainly responsible for its deformation and fracture behavior. They concluded that an increase in the carbon content of steel results in an increase in strength and a decrease in deformation and fractures. Similarly, Gupta et al. (2004) also conducted a study to evaluate the performance of a duck foot sweep equipped with agricultural soil manipulating implement. They also reported that maximum weight loss in terms of abrasion was observed in the mild steel (low-carbon steel)-made duck foot sweep. In addition to this, it was also studied and surveyed from the market that low-carbon steel is cheaper and easy to form as compared to medium- and high-carbon steel. In each material category, lowest value of total deformation, maximum principal stress, and the equivalent elastic strain were found in the CAD models with 45° tip angle (CAD-α3). Therefore, the design of raspador with 45° tip angle of scratching blade and low-carbon steel may be used for the development.

Conclusion

In this study, FEM was used to conduct the structural analysis for the design and simulation of the banana fiber-extracting raspador. For this purpose, three CAD models of raspador having tip angles of blades of 25°, 35°, and 45° were developed in the Creo Parametric (Version 7) software and simulated in the Ansys_® software using three material properties, i.e. high-carbon steel, medium-carbon steel, and low-carbon steel. For measuring the force required to scrap the fiber from banana pseudo-stem for FEM simulation of the raspador, an embedded system and laboratory setup were developed. The measurements taken by the developed embedded system show that approximately 99.09 N force was required to scratch the fibers from single pseudo-stem sheath and finally this was used for the simulation purpose. The maximum value of total deformation and maximum principal stress was found in the low-carbon-steel-based models, whereas maximum value of equivalent elastic strain was found in the high-carbon-steel-based models. In this study, the overall maximum deformation was observed in the M₃-CADα1 (tip angle: 25° and material: low-carbon steel) raspador model in both the tests (SSA test: 3.29 e⁻⁰⁵ m and EDSA test: 7.71 e⁻⁰⁵ m), whereas the minimum value of 1.55 e⁻⁰⁵ m was found in M₁-CADα3 raspador model in SSA test and 6.07 e⁻⁰⁵ m was found in M₃-CADα3 raspador model in EDSA test, but the difference was significantly very less and under the yield limit of the parent material. In both static structural and explicit dynamic simulation tests, the CAD model M₃-CADα3 (material: low-carbon steel and tip angle of blade: 45°) has the higher value of total deformation and maximum principal stress and comparatively lower value of elastic strain but under the yield limit of the material to sustain the failure of the structure.

The results of this work could be used for the development of the prototype of the entire banana pseudo-stem fiber extractor machine. The biggest benefit of this work is that the proposed technology (FEA simulation technique) will help the design engineers of small- and medium-scale agricultural machine manufacturing industries, who have very limited resources in simulating and analyzing the mechanical behavior of material and design concepts without developing and testing the physical model of a machine. This technique will ultimately help them to save the investment cost and time, and provide more profit.

Highlights

• Development of laboratory setup for measuring the force required to extract the fibers from the banana pseudo-stem.

• Development of CAD models of banana pseudo-stem fibre-extracting raspador using Creo Parametric software.

• Finite element analysis of the banana pseudo-stem fibre-extracting raspador using three material properties.

Ethical approval

We would like to inform you that we took the approval from the competent authority for submitting the research paper to the journal.

Acknowledgements

The authors are thankful to the Director, ICAR-Natural Fibre Engineering and Technology, Kolkata, for providing the necessary resources for executing the research work.

Disclosure statement

No potential conflict of interest was reported by the authors.