# Stress and Fatigue Analysis of Picking Device Gears for a 2.6 kW Automatic Pepper Transplanter
## 1 Introduction  
Peppers (_Capsicum annuum_ L.) are the most commonly consumed type of spicy vegetable and the second most commonly traded vegetable worldwide [1, 2]. Although pepper production is increasing globally, decreased rates were recorded in some countries (e.g., Korea and Japan) over the last few decades due to farm labor shortages, small agricultural and areas, and the aging of farmers [3]. Therefore, to reduce the labor requirement and the difficulty of operation of the pepper transplanting operation, mechanical transplanters have increased in popularity [4]. Furthermore, to achieve an easier and more farmer-friendly mechanical pepper transplanting technique, researchers have focused on designing fullyautomated transplanting operations. A picking device is an essential part of an automatic transplanter as it reduces the difficulty of operation by carrying out a repetitive task in a precise and consistent manner [3]. For favorable structural durability and manufacturing costs, the assessment of stress and fatigue damage is a crucial stage before operation at the agricultural field level [5]. The structural durability requirements of a machine can be satisfied if the machine parts are designed to have an adequate fatigue strength based on the service life [6; 7]. The most critical design conditions for the machine are the material and dimension requirements, since some components may experience excessive loads [8; 9]. Among the major components of a machine, critical loading conditions occur in the transmission system, such as gears and gear shafts [10]. Generally, in the gear mechanism, immediate load variation occurs in relation to the mechanical transmission, particularly at teeth contact points [11; 12]. Researchers have suggested various approaches, including a simulation-based finite element analysis (FEA), for calculating the load distribution and stress of the gear set [13; 14; 15; 16; 17]. Based on these studies, the contact stress analysis of the gear mechanism could estimate the necessary gear dimension and material properties and play a significant role in evaluating the damage to the machine in the development and performance evaluation stages. [PERSON] et al. [16] investigated the gear contact stress during rotation at various contact positions. The roll angle was used to measure the contact positions and evaluated the FEA results for the specific position. [PERSON] et al. [17] classified different types of gear faults by analyzing the ensemble empirical mode decomposition to the transmission error and found the criteria of maximum gear fault by applying the FEA method. For a single pair of teeth, the stress was determined at the contact surface between two spheres at different loads and speed, based on the theoretical analysis [12]. In the simulation-based study, several strengths were used in terms of management time and costs, but if the real working environmental conditions were not reflected, it was challenging to ensure the consistency of the results [18]. Load measurement experiments were required to validate the simulation-based study by determining the damage level for the selected gear dimensions and material properties. Load analysis and fatigue life prediction based on the designated gear dimension and material are important for safety, preventing damage, and ensuring the structural reliability of the picking operation. Several methods have been examined to enhance the fatigue life prediction accuracy for different types of machinery [19]. In 1936, [PERSON] and [PERSON] [20] formulated a structural durability test for agricultural machinery (binding mower), analyzing the applied load in a real field. The structural durability under field conditions for a rotary cultivator was examined by [PERSON] [21]. Previously, research on load analysis through field investigations has mainly focused on fundamental statistical analyses [18].