# Experiment and Analysis on Friction Damage and Energy Loss Characteristics of Potatoes
## 1 Introduction  
The mechanized potato harvesting industry has experienced rapid development since China launched the strategy to process potatoes as a staple food in 2015 [1]. The harvest efficiency of potatoes has greatly improved due to research and development as well as the popularization of potato harvesting machinery [2; 3; 4]. However, the problem of epidermal damage due to potato soil separation and transport during harvest has also become increasingly prominent [5]. Epidermal damage directly affects the appearance and quality of potatoes, and their economic value is also reduced [6; 7; 8]. In addition, potatoes with a damaged epidermis are not resistant to storage as they are highly susceptible to bacterial infection, causing softening and decay [9; 10]. At present, there are many reports on potato damage in China and in other countries, most of which are based on tests by potato drop collision and impact test rigs. Different researchers have selected different test factors and evaluation indicators. Some research teams have established the relationship among impact acceleration, drop height and damage severity, and obtained the influence of tuber size and temperature on potato damage [11]. Other research teams also determined linear regression models for a comprehensive potato damage index through single factor tests [12]. The research of [PERSON] shows that the order of importance for the factors affecting the severity of potato collision damage is falling height, impact materials, impact times and potato mass [13]. Similarly, it wasalso found by [PERSON] that the significant factors affecting the comprehensive index of potato damage are impact materials and potential energy [14]. Different from others, [PERSON] adopted an acceleration acquisition system and concluded that the primary and secondary order of factors affecting the volume of potato collision damage was initial height, potato mass, potato temperature and collision material, and the variation in the relationship between collision acceleration and damage area under different factors was determined [15]. In addition, some researchers obtained the critical damage value of potato under different conditions through response surface analysis in an orthogonal experiment of potato combinations [16]. Apart from these studies, other scholars have studied the friction characteristics of some agricultural materials. Most of these studies focus on the determination of the static friction coefficient and dynamic friction coefficient of materials, including the determination of the friction coefficient of apples with plexiglass and kraft paper, respectively [17]. Some studies have also been carried out on potato skins and different varieties, and the friction coefficient of potatoes has also been acquired [18; 19; 20]. Through the analysis of existing studies, it can be seen that the relevant studies focus on the damage caused by potato collision. The research on friction paid close attention to the measurement of the friction coefficient between potato and different materials, and systematic research on the characteristics of potato friction damage was rarely reported. Meanwhile, the effects of different experimental factors on friction damage and related characteristic parameters of potatoes have not been reported. Based on the above analysis, this paper uses a single pendulum friction test rig to select the significant factors affecting potato friction damage through a factorial test. It then explores the effect of significant factors on potato friction damage and energy loss characteristics through a single factor test. The regression equation and correlation coefficients between significant factors and evaluation indicators as well as between evaluation indicators were obtained, taking the proportion of epidermal damage and the ratio of energy consumption loss as evaluation indicators.