Stress Simulation on Four-Bar Link-Type Transplanting Device of Semiautomatic Vegetable Transplanter

Abstract

The aim of this study is to analyze the stress exerted on a four-bar link-type transplanting device using two distinct methods: stress measurement performed during a field test and stress simulation. A field test is conducted to measure stress using a strain gauge positioned at 15 specific points on the transplanting device. Subsequently, the measured strain data are converted into calculated stress data. In another method, stress is simulated using specialized multibody dynamic simulation software. The simulation results are compared with the stress measured during field tests to verify the simulation model. Based on the results, the maximum stress derived from the simulation correlates with the measured results, although notable discrepancies are shown, particularly at strain gauge positions 11 and 13. The maximum stress derived from the simulation is used to calculate the static safety factor of the transplanting device. The peak stress derived from the simulation aligns with the measured results, although significant discrepancies are observed at positions corresponding to strain gauges 4 and 10. The maximum stress (150.82 MPa) is observed on the link of the transplanting device, and the static safety factor determined via the simulation is 1.39.

1. Introduction

In modern agriculture, the development of efficient and reliable mechanized equipment is pivotal in enhancing productivity and reducing labor-intensive processes [1,2,3]. The vegetable transplanter is a prime example of this innovation which facilitates the transplantation of seedlings with high precision and speed. The classification of vegetable transplanters into semiautomatic and fully automatic types depends on how the seedlings are extracted and positioned within the seedling cylinder. In a fully automatic vegetable transplanter, the seedlings are supplied and loaded into the seedling cylinder automatically. On the other hand, in a semiautomatic vegetable transplanter, the operator manually provides and positions the seedlings within the seedling cylinder, requiring human involvement in the seedling handling process [4,5]. The transplanting device is the main part of a vegetable transplanter, tasked with planting seedlings into the soil. Various types of vegetable transplanters have been created, distinguished by their transplanting device design, including wheel, rotary, four-bar link, and cam types [6,7]. Among these, the four-bar link mechanism is notably prevalent and widely employed. This is attributed to the simpler structure of the four-bar link-type transplanting device relative to other types, the low manufacturing cost, and greater user-friendliness. Therefore, four-bar link-type transplanters are widely used on farms.

When a vegetable transplanter is operating, the transplanting device receives large and repeated stresses. This stress may result in material breakdown, diminished efficiency, and the emergence of safety risks [8]. However, to ensure the seamless functionality and safe operation of vegetable transplanters, a comprehensive load and safety analysis is imperative. Such analyses are equally essential for understanding the behavior of transplanting devices under different operating conditions and for identifying potential design improvements [9,10]. Sri et al. [11] conducted a study on four-bar link vegetable transplanters, analyzing loads and safety. Strain gauges were placed on the device to measure strains, which were converted to stress data for static safety factor and fatigue life estimation. The experiments covered four engine speeds and ten planting distances, revealing that increased speed and distance heightened stresses. The results showed a reduced static safety factor and fatigue life with higher engine speed and extended planting distance. Despite consistently exceeding 1.0, the static safety factor decreased. The shortest fatigue life (49,153.3 h) occurred at link A (S_14), with 750 rpm engine rotational speed and 0.35 m planting distance.

The first step in assessing the load and safety of a machine component is to evaluate stress levels. The prevalent approach for gauging the stress on machine components involves the utilization of sensors, such as strain gauges or load cells, which are validated through field trials [12]. The selection of sensors is contingent upon the intricacy of the apparatus and the precision necessary to precisely capture the stress distribution. Nevertheless, sensors can only appraise stress at specific installation sites. A multitude of sensors must be deployed to ascertain stress distribution across multiple points. Consequently, stress assessments via field experiments can be time-consuming and incur substantial expenses [13,14].

An alternative approach for ascertaining the stress affecting a machine component is simulation. The initial stage of stress simulation entails the construction of a precise virtual prototype model. Using this model, simulations can be conducted to acquire stress-related data across all sections of the machine component, as opposed to solely specific locations, as demonstrated in stress measurements performed experimentally [15,16]. Diverse commercially available dynamic simulation software programs are promising for predicting stress dispersion within intricate structures and highlighting regions with high stress concentrations. Simulation results can provide insights into the behavior of an apparatus under varying loads and operational circumstances, thereby facilitating the recognition of potential design enhancements to improve performance and safety [17,18].

Numerous studies have explored stress simulations in various agricultural machinery. Plouffe et al. [19] examined the impact of different components and adjustments on a moldboard plow’s performance in clay soil. They combined modeling using the finite element method (FEM) with experimental observations. Makange et al. [20] conducted a FEM analysis on a nine-tine cultivator to identify potential weaknesses in the shovel element under varying loads and speeds in medium-black soil. Their findings revealed maximum and minimum principal stresses of 5.1726 and 0.20944 megapascals (MPa), respectively, with a total deformation of 0.076953 mm. Importantly, the highest stress remained below the yield point, indicating no tine failure due to deformation. Similarly, Yurdem et al. [14] investigated stresses in a three-bottom moldboard plough using strain gauges on different parts of the moldboard frame. They compared these measurements with outcomes from finite element simulations. The study concluded that reducing the moldboard frame thickness did not lead to excessive stresses, and the observed strains closely matched the simulated data. Kesner et al. [15] developed a computational model for a tillage machine to analyze these loads. The results showed good agreement between experimental stress measurements and simulation data from the model. Therefore, the methods used in this study can be applied in designing and improving tillage machinery. In a separate study, Islam et al. [21] analyzed the stress resistance of the gear mechanism in the picking device of an automatic pepper transplanter. They aimed to determine optimal materials and dimensions and predict fatigue life based on damage assessment. To the best of our knowledge, there has not been a specific virtual stress simulation model tailored for four-bar link-type transplanting devices, despite extensive research in this area.

The aim of this study is to investigate the stress distribution and analyze the safety of four-bar link-type transplanting devices of semiautomatic vegetable transplanters through simulation. The specific objectives are (1) to develop a three-dimensional (3D) model of the transplanting device using a commercial dynamic simulation program; (2) to perform an analysis through simulation; and (3) to validate the precision of the created virtual model by contrasting simulation data with experimental data. The results of this study offer valuable insights to the manufacturers and designers of transplanting devices for improving the safety, performance, and reliability of these devices. In addition, the results of this study can be used as basic data to establish the design process or design guidelines for four-bar link-type planting devices.

2. Materials and Methods

2.1. Vegetable Transplanter Used in Current Study [17]

A four-bar link-type vegetable transplanter was used in this study. The shapes and specifications of the vegetable transplanter are shown in Figure 1 and

Table 1. Specifications of the four-bar link-type vegetable transplanter used in this study.

Item	Specification
model/manufacturer/nation	KTP-30/TONGYANGMOOLSAN, Seoul, South Korea
length/width/height (mm)	2125/1180/1510
weight (kg)	199
engine: rated power (kw)/rated sped (rpm)	3.4/1800
planting distance (mm)	300–500
maximum working speed (m/s)	0.4
working efficiency (h/10a)	1.5–2.0
length/width/height (mm)	2125/1180/1510
weight (kg)	199

, respectively. It comprises an engine to supply power, a transmission to transfer power to both the wheel and transplanting device, seedling cylinders to place seedlings, and transplanting devices to plant seedlings supplied from the seedling cylinder into the soil.

The transplanter with the four-bar link-type transplanting device operates as follows. A user determines the transplanting speed and supplies the seedlings to the seedling cylinders manually. The transplanter operates in the forward direction and plants the seedlings into the ground one by one due to the motion of the transplanting device. That motion makes the transplanting hopper of the four-bar link-type transplanting device move up and down in a certain trajectory. When the hopper is at the top, it is located just below one of the seedling cylinders. Then, the seedling is dropped into the transplanting hopper by the opening of the seedling cylinder. When the transplanting hopper is at the bottom and it is located at a certain depth in the ground, the transplanting hopper is opened and the seedlings are planted into the ground. The transplanting work is completed after covering the planted seedlings with soil. During the transplanting process, the transplanter places a load on the transplanting device. The range of transplanting frequency is between 0.5 and 1 Hz, depending on the planting distance. This value was obtained based on the results of measurements from previous research [17]. In addition, the transplanter establishes contact with the soil, and a relatively higher load is exerted on the transplanting device than on other components. The main components of the transplanting device are the links, the crank, and the transplanting hopper. Due to the kinematic design, the movement of the link affects the operation cycle and trajectory of the transplanting hopper. The crank supplies the power transmitted from the engine and transmission to the transplanting device. The material properties of the four-bar link-type transplanting device are listed in

Table 2. Mechanical properties of the four-bar link-type transplanting device (steel alloy 1020).

Item	Specification
density, ρ (kg/m3)	7.85 × 103
modulus of elasticity, E (GPa)	207
Poisson’s ratio, ν	0.3
yield strength, Sy (MPa)	210
yield strength in shear, Ssy (MPa)	105
ultimate strength, Sut (MPa)	380
fatigue strength of 106 cycles, Sn (MPa)	190

.

2.2. Stress Measurement

2.2.1. Stress Measurement System

A stress measurement system was designed to measure the stress exerted on the transplanting device, as shown in Figure 2. The stress measurement system comprised strain gauges, a data acquisition system (TG009E, HBK, Darmstadt, Germany), and a laptop. The strain data measured using the strain gauges were transmitted to a data acquisition unit and recorded on a laptop. Two types of strain gauges were used to obtain strain data for the transplanting device links. The uniaxial strain gauge is suitable for measuring the strain in a singular direction, thus rendering it appropriate for scenarios in which a primary loading direction is evident, such as axial bars or links (KFGS-5-350-C1-11 L10M3R, KYOWA, Tokyo, Japan). Additionally, a rosette strain gauge comprising three strain gauges positioned at 45° intervals was used (KFGS-1-350-D17-11 L5M3S; KYOWA, Tokyo, Japan). The rosette strain gauge is optimal for measuring areas where the main loading direction is uncertain because it encompasses three strain gauges positioned at distinct angles. The transplanting device of the four-bar link type comprises hopper and link components. The primary loading direction on the link is well-defined; therefore, a uniaxial strain gauge is selected and affixed to the link. In contrast, the hopper section has an area with an unclear main loading direction. Consequently, a rosette-type strain gauge is chosen as the strain measurement tool for the hopper.

Figure 3 shows the locations at which 13 uniaxial strain gauges (S1–S2 and S5–S15) and two rosette-strain gauges (S3 and S4) were installed for this study. Strain gauges were strategically positioned in different sections of the transplanting device, such as on a link, where they were installed both in the middle and at the ends. This placement was implemented to enable the measurement of strains across various components of the transplanting device. The two uniaxial strain gauges (S1 and S2) were attached to the end of the transplanting hopper. The rosette strain gauges (S3 and S4) were attached to the curved upper part on both sides of the transplanting hopper, respectively. The uniaxial strain gauges of S5, S6, and S7 were attached to the left, middle left, and middle right sides of the sub-link F, respectively. The strain gauges S6 and S7 were both situated in the middle of sub-link F, with S6 positioned closer to the left end and S7 closer to the right end. This placement was selected to capture a more comprehensive measurement of stress in sub-link F. The uniaxial strain gauges of S8, S9, and S10 were attached to the left, middle, and right sides of link B, respectively. Two strain gauges (S11 and S12) were installed on the left and right sides of link A. The uniaxial strain gauge S13 was placed at the right side of sub-link F, the strain gauge S14 was placed at middle side link D, and the strain gauge S15 was attached to middle side link C. The effect of the measurement system on the stress exerted on the transplanting device was ignored.

The specifications of the strain gauges and data acquisition module are shown in

Table 3. Specifications of strain gauges used.

Gauge	Item	Specification
uniaxial strain gauge	model/manufacture/nation	KYOWA KFGS-5-350-C1-11 L10M3R/KYOWA/Tokyo, Japan
	gauge factor (%)	2.12 ± 1.0
	gauge length (mm)	5
	gauge resistance (%)	351.2 Ω ± 0.4
rosette strain gauge	model/manufacture/nation	KYOWA KFGS-1-350-D17-11 L5M3S/KYOWA/Tokyo, Japan
	gauge factor (%)	2.11 ± 1.0
	gauge length (mm)	1
	gauge resistance (%)	350.0 Ω ± 0.7

and

Table 4. The specifications of the data acquisition module used.

Item	Specification
model/manufacture/nation	TG009E/HBK/Darmstadt, Germany
length/width/height (mm)	177/161/386
weight (kg)	5
number of channels	16
sampling rate (Hz)	Up to 320

, respectively.

2.2.2. Operating Condition

The field test took place in a field featuring consistent soil conditions, situated at coordinates 37°56′24.0″ N and 127°46′59.1″ E. The location has an elevation of 111.00 m above sea level and is in Sinbuk-eup, Chuncheon, within Gangwon Province, South Korea. The test bed was measured as 45 m (length) × 0.6 m (width) × 0.3 m (height). Before the experiments, the soil was tilled using a plow and a rotavator to account for the actual operating conditions of the vegetable transplanter. The vegetable transplanter was operated at an engine rotational speed of 750 rpm at a planting distance of 0.35 m and a planting depth of 0.07 m. The test was performed in triplicate and the data were analyzed using the average as a representative value.

2.2.3. Analysis of Measured Data

The strain data acquired during field tests were converted to stress values. This conversion was contingent upon the specific type of strain gauge used, thus resulting in two distinct categories of strain data. The stress was calculated by multiplying the strain data derived from the uniaxial strain gauge by the modulus of elasticity, as shown in Equation (1). By contrast, the rosette strain gauge was used to measure strains along three different axes. By utilizing the strain values recorded for each direction, significant stress values such as the maximum and minimum principal stresses and von Mises stress can be calculated using Equations (2)–(5) [11].

$$\mathsf{\sigma }=\mathrm{E}\times \mathsf{\epsilon },$$

(1)

$${\mathsf{\sigma }}_1=\frac{\mathrm{E}}{2(1-{\mathrm{v}}^2)}\left[\left(1+\mathrm{v}\right)\left({\mathsf{\epsilon }}_{\mathrm{a}}+{\mathsf{\epsilon }}_{\mathrm{c}}\right)+\left(1-\mathrm{v}\right)\times \sqrt{2\left\{{({\mathsf{\epsilon }}_{\mathrm{a}}-{\mathsf{\epsilon }}_{\mathrm{b}})}^2+{({\mathsf{\epsilon }}_{\mathrm{b}}-{\mathsf{\epsilon }}_{\mathrm{c}})}^2\right\}}\right],$$

(2)

$${\mathsf{\sigma }}_2=\frac{\mathrm{E}}{2(1-{\mathrm{v}}^2)}\left[\left(1+\mathrm{v}\right)\left({\mathsf{\epsilon }}_{\mathrm{a}}+{\mathsf{\epsilon }}_{\mathrm{c}}\right)-\left(1-\mathrm{v}\right)\times \sqrt{2\left\{{({\mathsf{\epsilon }}_{\mathrm{a}}-{\mathsf{\epsilon }}_{\mathrm{b}})}^2+{({\mathsf{\epsilon }}_{\mathrm{b}}-{\mathsf{\epsilon }}_{\mathrm{c}})}^2\right\}}\right],$$

(3)

$${\mathsf{\sigma }}_{\mathrm{v}}=\sqrt{{\mathsf{\sigma }}_1^2-{\mathsf{\sigma }}_1{\mathsf{\sigma }}_2+{\mathsf{\sigma }}_2^2},$$

(4)

$${\mathsf{\tau }}_{\mathrm{m}\mathrm{a}\mathrm{x}}=\frac{\mathrm{E}}{2(1+\mathrm{v})}\times \sqrt{2\left\{{({\mathsf{\epsilon }}_{\mathrm{a}}-{\mathsf{\epsilon }}_{\mathrm{b}})}^2+{({\mathsf{\epsilon }}_{\mathrm{b}}-{\mathsf{\epsilon }}_{\mathrm{c}})}^2\right\}},$$

(5)

where

σ	= calculated axial stress (Pa)
${\mathsf{\sigma }}_1$	= maximum principal stress (Pa)
${\mathsf{\sigma }}_2$	= minimum principal stress (Pa)
${\sigma }_v$	= von Misses stress (Pa)
$\mathsf{\epsilon }$	= measured strain for the components of transplanting device
E	= modulus of elasticity (Pa)
$\mathrm{v}$	= Poisson’s ratio
τmax	= maximum shear stress (Pa)
εa	= strain measured by rosette strain gauge in horizontal direction
εb	= strain measured by rosette strain gauge in 45° direction
εc	= strain measured by rosette strain gauge in vertical direction

2.3. Stress Simulation

2.3.1. Dynamic Simulation Model

A dynamic simulation to derive the stress exerted on the four-bar link-type transplanting device was performed using commercial software (Recurdyn V9R4, Functionbay, Seongnam, Republic of Korea). This software is typically used in studies for predicting forces or loads within diverse multibody systems comprising rigid and flexible components. Figure 4 illustrates a 3D model of the four-bar link-type transplanting device. A 3D model of the transplanting device was created based on its actual dimensions and material properties.

2.3.2. Simulation Condition

The simulation model for deriving the stress exerted by the contact between the transplanting hopper and ground is shown in Figure 5. The simulation was conducted at an engine rotational speed of 750 rpm and a planting distance of 0.35 m, i.e., the condition at which the highest stress was recorded in the experiment. In the stress simulation, the effect of vibration from the engine, the transmission, etc. was not considered. The gravitational acceleration was set to 9.81 m/s² to act vertically downward. A simulation was set to derive the stress exerted on the links and transplanting hopper when it contacts the soil during the time when the four-bar link-type transplanting device and the transplanter operate together. The conditions of the interaction between the hopper and ground are listed in

Table 5. Material properties used in simulation.

	Item	Value
interaction between hopper and ground	stiffness coefficient	35
	damping coefficient	0.03
	dynamic friction coefficient	1.0

.

2.4. Verification of Stress Simulation

To verify the simulation model, the stress values derived from the field test and simulation were compared and analyzed. The validation process involved a comparison between the maximum stress at 15 specific points on the transplanting device links and the transplanting hopper (Figure 3). The stress data obtained from the experiment, which validated the simulation results, were the averages of the maximum stress values (peak stress) derived from three repeated tests. The root mean square error (RMSE) was calculated to determine the disparity between the maximum stress values derived from the simulation results and those obtained from the field test measurements. As the RMSE decreases, the disparity between the maximum stress in the experiment and the simulation becomes smaller [21]. The RMSE is determined by Equation (6).

$$\mathrm{R}\mathrm{M}\mathrm{S}\mathrm{E}=\sqrt{\frac{1}{\mathrm{n}}\times {\sum }_{\mathrm{i}=1}^{\mathrm{n}}({\mathrm{y}}_{\mathrm{i}}-\widehat{{\mathrm{y}}_{\mathrm{i}}}{)}^2}$$

(6)

where,

$\mathrm{R}\mathrm{M}\mathrm{S}\mathrm{E}$	= root mean square error
${\mathrm{y}}_{\mathrm{i}}$	= measured maximum stress in the experiment
$\widehat{{\mathrm{y}}_{\mathrm{i}}}$	= measured maximum stress in the stress simulation
$\mathrm{n}$	= number of stress measurement locations

2.5. Maximum Stress and Static Safety Factor

The simulation results indicated stress across all regions of the transplanting device. These results can be used to determine the position and magnitude of the highest stress point. The maximum stress from the simulation may differ among the 15 locations where the strain gauges were applied during the field test.

The static safety factor is commonly used in engineering design and analyzed to ensure that structures and materials can withstand the stresses and loads that they will encounter during their expected service life [22]. In order to derive the static safety factor, it is necessary to identify both the yield strength that a material can endure and the maximum stress exerted on the transplanting device during operation [23]. The static safety factor is determined by the ratio of the yield strength and the maximum stress incurred. If the static safety factor exceeds 1.0, it can be judged that a safe design has been achieved. On the other hand, if the static safety factor is less than 1.0, it indicates that the transplanting device of the four-bar link-type vegetable transplanter can be damaged or destroyed by static load. Prior to constructing a machine, specifically during the machine tool design stage, calculation of a static safety factor is performed. If the result of the static safety factor calculated by simulation is less than 1.0, design improvement is necessary. This process aims to optimize the design, ensuring its viability and suitability for production. The static safety factor can be calculated by Equations (7) and (8) [11]. In addition, considering the static safety factors, it is essential to address dynamic loads when designing a machine. This is particularly important when the results of static safety factors are only marginally higher than 1.0, as dynamic loads can pose greater damage.

$$\mathrm{S}\mathrm{F}=\frac{{\mathrm{S}}_{\mathrm{y}}}{{\mathsf{\sigma }}_{\mathrm{m}\mathrm{a}\mathrm{x}}}$$

(7)

$$\mathrm{S}\mathrm{F}=\frac{{\mathrm{S}}_{\mathrm{y}}}{{\mathsf{\sigma }}_{\mathrm{v}\_\mathrm{m}\mathrm{a}\mathrm{x}}}$$

(8)

where

SF	= static safety factor
Sy	= yield strength (Pa)
${\mathsf{\sigma }}_{\mathrm{m}\mathrm{a}\mathrm{x}}$	= maximum axial stress (Pa)
${\mathsf{\sigma }}_{\mathrm{v}\_\mathrm{m}\mathrm{a}\mathrm{x}}$	= maximum von Mises stress (Pa)

3. Results and Discussion

3.1. Verification of Stress Simulation

The maximum stress values obtained from the experimental and simulation results are presented in Figure 6 and

Table 6. Maximum stress values for 15 locations of the four-bar link-type transplanting device.

Strain Gauge Number	Measured Maximum Stress (MPa)	Maximum Stress Derived by Simulation (MPa)	RMSE
S1	−6.30	−6.74	3.3117
S2	−6.97	−8.33
S3	19.11	19.88
S4	23.28	32.35
S5	71.27	72.72
S6	66.67	68.82
S7	58.99	59.47
S8	−20.32	−21.34
S9	−29.81	−29.17
S10	21.10	15.17
S11	21.98	19.12
S12	48.59	46.83
S13	21.94	18.21
S14	81.81	84.71
S15	42.65	44.21

.

When considering the absolute value of the measured maximum stress, the maximum stress of the S14 location was the highest at 81.81 MPa in the experiment and 84.71 MPa in the simulation, respectively. Then, the maximum stress in strain gauge S5 was 71.27 MPa (experiment) and 72.72 MPa (simulation), which was the second, followed by strain gauge S5, S6, S7, S12, and S15. In the case of the location S1, the maximum stress was the lowest at −6.30 MPa in the experiment and −6.74 MPa in the simulation, respectively.

Based on the verification results obtained from the 15 distinct points, one can deduce that the simulation findings aligned with the experimental results. Nevertheless, significant disparities were observed at certain points, particularly at strain gauges 4 and 10. Conversely, strain gauges 5, 6, 7, and 14, which manifested greater stress levels than the other positions, exhibited a substantial level of agreement.

The RMSE between the maximum stress data from the simulation and the maximum stress data from the field test was 3.3117 MPa, which signifies an insignificant variance between the anticipated and recorded values. This result can be regarded as modest, particularly when considering the typical range of maximum stress, i.e., from −29.81 MPa to 81.81 MPa. In addition, the normalized RMSE for the four-bar link arrangement was 0.0297, which approached zero. This figure shows a precise model with a strong correlation between the projected and actual measurements.

The differences between the simulated and measured results can be attributed to various factors, including the omission of frictional forces between joints in the simulation and disparities in the assembly of components when comparing the simulated scenarios to real-world conditions. Additionally, the effects of vibrations generated by the operating engine were not incorporated in the simulation. Moreover, the load input from the main body, which was facilitated by the connection to the machine frame, was not considered in the simulation. Despite the significant deviations at specific points, 12 out of 15 points indicated consistency. Consequently, one can infer that the stress values derived from the simulation aligned adequately with the stress levels measured during the field test.

3.2. Maximum Stress and Static Safety Factor Based on Simulation

Figure 7 shows the stress simulation results for the four-bar link type transplanting device. The maximum stress value was 150.82 MPa, which was recorded within sub-link E and served as a connection among links G, D, and F. The position of sub-link E, i.e., at the structural center of the entire transplanting device, resulted in a high stress owing to forces from the ground and engine, thus resulting in greater stress in this region compared with other regions.

Based on the maximum stress data from the simulation results, the static safety factor for the four-bar link type was 1.39, which was deficient owing to its proximity to 1. Several strategies can be applied to augment the static safety factor of the transplanting equipment. One potential approach involves substituting an existing material with one that possesses a higher yield strength, thereby contributing to an elevated level of safety. Alternatively, employing AISI 1030, which possesses a yield strength of 344.7 MPa, can increase the static safety factor for the four-bar link connection to 2.29 [18].

When selecting a material, one must consider not only the yield strength, but also its specific attributes. Additionally, the economic viability of the material must be prioritized because its price significantly affects the production cost of a machine. This consideration is essential for ensuring that the machine design maintains affordability while satisfying the required criteria.

4. Conclusions

In this study, stress measurements and dynamic simulations were conducted to determine the stress level of the four-bar link-type transplanting devices of a semiautomatic vegetable transplanter.

The main results of this study were as follows. The maximum stress obtained from the simulation results for the four-bar link-type transplanting device correlated with the measurement results, although significant differences were observed for strain gauges numbers 4 and 10. This study’s outcomes demonstrate the feasibility of employing simulation for stress measurement, yielding precise results. Based on the simulation results, the maximum stress of the four-bar link type at the sub-link E was 150.82 MPa. The sub-link E, located at the structural midpoint of the entire transplanting device, experienced elevated stress due to forces originating from both the ground and engine. Consequently, this area exhibited higher stress levels compared to other areas. The static safety factor obtained from the simulation of the four-bar link type was 1.39. The transplanting device design is deemed secure, as indicated by the static safety factor value surpassing 1.0. Even so, this static safety factor is still relatively low so it is still necessary to increase the safety level of four-bar link-type transplanting devices. To heighten safety, various avenues can be explored, including replacing the current material with a stronger alternative or adjusting the design of susceptible components in terms of shape or size. The findings from this study demonstrate that employing simulation techniques for stress assessment in machine components can expedite and economize stress measurements for safety analysis. Furthermore, the findings of this study can serve as foundational data to establish the process and guidelines of design for four-bar link-type transplanting devices. As a future study, based on the results of this study, a kinematic analysis of the four-bar link-type transplanting device will be performed to establish a design process that can improve durability and economic efficiency while satisfying the appropriate planting trajectory.