Using the Equivalent Static Pressure Method to Assess Free Fall Damage of the Korla Fragrant Pear

: In order to explore the equivalent static condition of the impact damage of the Korla fragrant pear under free fall, the Korla fragrant pear was chosen as the research object in this paper, and the height of free fall and rebound were recorded by a high-speed camera to obtain the impact damage energy of the fragrant pear. In addition, a mechanical compression test was conducted on the fragrant pear to obtain its static deformation energy, and the equivalent static condition of the impact damage was calculated based on the mechanical energy conservation formula using the damage volume of the fragrant pear as the evaluation standard. The test veriﬁcation was carried out on the damaged fragrant pear using a scanning electron microscope test. This study showed that the falling and rebound height of the fragrant pear within the range of the test parameters and under the free fall test conditions conform to linear ﬁtting. The coefﬁcient of determination (R 2 ) was 0.9951, and the impact damage occurred when the corresponding energy reached 205.89 × 10 − 3 J. When the damage energy was within 203.4 × 10 − 3 J and 498.23 × 10 − 3 J, the static damage volume of the fragrant pear was linearly correlated to the impact damage volume, R 2 was 0.9944, and the maximum deviation between the predicted damage volume and the actual damage volume of the fragrant pear in the veriﬁcation test was 4.4%. These data can provide a reference for research on the equivalent method of impact damage of the Korla fragrant pear, and provide theoretical guidance to the fruit industry to reduce damage and increase efﬁciency.


Introduction
The Korla fragrant pear is a unique fruit in China, with a sweet and smooth taste, thin skin, and fine pulp, often being called a "treasure among the pears" [1][2][3][4]. It is prone to mechanical damage in the process of harvesting, resulting in more than 30% of stored fragrant pear being discarded each year, which greatly reduces its yield [5,6]. Decreasing the amount of postharvest mechanical damage can improve profits for fruit growers and assist in food security [7]. The impact damage of the Korla fragrant pear requires comprehensive consideration of the form and timing of load action. Impact damage analyses require much time and energy, have low efficiency [8,9], and the calculation results are influenced by many parameters; in addition, the calculation process is not stable enough, and the repeatability of test results is poor. On the other hand, the static pressure damage measurement method of the Korla fragrant pear is simple and reliable [10][11][12], and the calculation analysis and test verification are relatively mature. Meanwhile, the measurement damage volume can be selected for both static pressure and impact damage evaluation methods. Therefore, the static pressure damage test is applied to represent the impact damage of the Korla fragrant pear, and the equivalent static pressure method for impact damage in the Korla fragrant pear is studied according to the damage energy and damage volume. The study of impact damage of fragrant pear will be simplified and a feasible equivalent method will be proposed. By equating the free fall damage of the Korla fragrant pear to static pressure damage, the damage degree of the Korla fragrant pear can be studied more accurately.
With regard to the mechanical damage of fruits, relevant scholars have performed much work. In terms of the static pressure damage, Yang et al. studied static pressure damage on different maturities of the Korla fragrant pear, and established a model of the relationship between static pressure damage and deformation to predict damage [13]. Wang et al. combined the traditional static pressure test with a finite element method simulation to predict grape damage [14]. In order to more accurately predict and evaluate the static pressure damage degree of the Korla fragrant pear, Wu et al. used the Prescale induction tablet to study and analyse the contact stress size and stress distribution of the fragrant pear under different degrees of pressure and carried out finite element numerical calculations [15]. In terms of impact damage, Ebrahim Ahmadi et al. simulated the impact of dynamic impact on apples using the finite element method, and evaluated the impact damage of fruit under different impact speeds [16]. Van Zeebroeck et al. conducted impact tests with a pendulum test device, and established multiple linear and nonlinear regression damage prediction models using varieties of the "tradro" tomato [17]. Xu et al. also studied the impact damage of different varieties of blueberries from different heights, and concluded that the degree of fall damage was related to the fall height and buffer materials [18]. In addition, Lewis et al. showed that different structural parameters of the apple itself had different effects on the collision damage area [19]. These studies on fruit damage regarding static pressure and impact provided important technical references for this study. However, the action forms and times of static pressure and impact loads occurred randomly during the damage process of the Korla fragrant pear, highlighting that there was still room for improvement in the mechanical damage guidance for fragrant pears based on limited loads and specific action forms.
In order to make fruit damage research better guide the actual production, researchers evaluated the damage degree of lychees [20], strawberries [21], and peaches [22] in terms of fruit static pressure damage research, and obtained the relationship between the damage degree, damage energy, compressive deformation amount, and drop height. The damage energy usually decreases with storage time and fruit maturity, indicating that energy is a suitable and easy measurable parameter to evaluate the degree of damage. In terms of fruit impact damage, researchers evaluated the damage degree of apples [23,24], palm fruit [25], yellow peaches [26], and pears [27], and revealed a relationship between impact height, contact material, impact damage volume, and impact energy, and obtained the surface pressure distribution of fruit under different energy free loads, as well as the critical energy value of pulp tissue damage. The damage resistance characteristics of fruit under the impact load of free fall were clarified. The above research indicated that the damage energy can effectively represent the damage degree of fruit in the study of static pressure and impact damage. The static pressure damage of fruit has been widely used by researchers due to its simple usage, high precision, and good reproducibility. However, the application of methods of fruit static pressure damage for the characterisation of impact damage degree still warrants further investigation. Within a certain range of parameters, the impact damage is equivalent to the static pressure damage by damage energy, which can shorten the detection time and improve the efficiency and accuracy of damage detection, thereby providing theoretical guidance to the fruit industry to improve damage detection and quality.
This paper takes the Korla fragrant pear as the test material, and uses the fragrant pear impact test bench and universal testing machine to carry out the impact and static pressure test on the Korla fragrant pear. The impact deformation energy, compression deformation energy, and damage volume of the Korla fragrant pear were calculated, the equivalent height of impact damage of the Korla fragrant pear was determined, the damage volume of the Korla fragrant pear was measured, and tissues of the Korla fragrant pear samples were examined using a scanning electron microscope. This leads to a new method to investigate mechanical damage of the Korla fragrant pears from the perspective of damage energy evaluation, and provides a basis to reduce damage in the fragrant pear industry.

Test Materials
The test materials were collected from the fragrant pear orchard under regular management by the Shituan in Alaer City, the First Division of Xinjiang Production and Construction Corps, which is a high-quality Korla fragrant pear producing area in South Xinjiang. The trees were 15 years old. The fragrant pears were collected from 120 pear trees. The details of management regulation are as follows: 1. Soil management: this is the use of a base fertiliser in autumn for deep turning, before the winter for flood irrigation. 2. Water supplement: reasonable irrigation according to the need of fruit trees and soil conditions. 3. Flower and fruit management: fine pruning, artificial pollination, and bee release in pear orchard; flower and fruit thinning to control the load of single plant; when there are few flowers and fruits, pay attention to protecting the flowers and fruits. 4. Pest control: pay attention to the protection and utilisation of natural enemies, maintain the ecological balance of farmland, and reduce environmental pollution ( Table 1). The harvesting occurred on 15 September 2022 using artificial cultivation and consisted of Korla fragrant pears with similar shapes, uniform colours, no damage, or pests, with a single fruit mass of 110 ± 5 g. The Korla fragrant pear colour was yellow-green at this moment, as shown in Figure 1. The harvesting personnel wore gloves throughout the picking process to prevent human factors from causing damage to the Korla fragrant pear. The impact test was conducted immediately after harvesting. A total of 250 pear samples were collected for the test.

Types of Management Management Methods
Soil management This is the use of a base fertiliser in autumn for deep turning, before the winter for flood irrigation.

Water supplement
Reasonable irrigation according to the need of fruit trees and soil conditions.

Flower and fruit management
Fine pruning, artificial pollination, and bee release in pear orchard; flower and fruit thinning to control the load of single plant; when there are few flowers and fruits, pay attention to protecting the flowers and fruits.
Pest control Pay attention to the protection and utilisation of natural enemies, maintain the ecological balance of farmland, and reduce environmental pollution.

Impact Test on the Korla Fragrant Pear
The Korla fragrant pear impact test system was used to conduct a damage test, as shown in Figure 2. Firstly, the impact height of the Korla fragrant pear was adjusted using

Impact Test on the Korla Fragrant Pear
The Korla fragrant pear impact test system was used to conduct a damage test, as shown in Figure 2. Firstly, the impact height of the Korla fragrant pear was adjusted using the height control handle, and the air compressor was turned on, allowing airflow to pass through the vacuum generator and produce negative pressure, forming a suction force at the suction cup to achieve the adsorption of the fragrant pear. After the fragrant pear was stable, the switch was closed, and the vacuum generator stopped, releasing suction. The fragrant pear was then free to fall by gravity, and a high-speed camera was used to record the height of the free fall and rebound of the fragrant pear. Throughout the impact pre-experiment, it was found that when an individual fragrant pear with high ripeness was impacted by the corrugated board, it had skin damage and lost its value when the impact height was 110 cm. On the other hand, when the impact height was 40 cm, the fragrant pear had no damage. Hence, the impact heights were set to 40 cm, 45 cm, 50 cm, 55 cm, 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, 90 cm, 95 cm, 100 cm, 105 cm, and 110 cm. The test was repeated 10 times at each height and the average was calculated.

Impact Test on the Korla Fragrant Pear
The Korla fragrant pear impact test system was used to conduct a damage test, as shown in Figure 2. Firstly, the impact height of the Korla fragrant pear was adjusted using the height control handle, and the air compressor was turned on, allowing airflow to pass through the vacuum generator and produce negative pressure, forming a suction force at the suction cup to achieve the adsorption of the fragrant pear. After the fragrant pear was stable, the switch was closed, and the vacuum generator stopped, releasing suction. The fragrant pear was then free to fall by gravity, and a high-speed camera was used to record the height of the free fall and rebound of the fragrant pear. Throughout the impact preexperiment, it was found that when an individual fragrant pear with high ripeness was impacted by the corrugated board, it had skin damage and lost its value when the impact height was 110 cm. On the other hand, when the impact height was 40 cm, the fragrant pear had no damage. Hence, the impact heights were set to 40 cm, 45 cm, 50 cm, 55 cm, 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, 90 cm, 95 cm, 100 cm, 105 cm, and 110 cm. The test was repeated 10 times at each height and the average was calculated.

Calculation of Impact Deformation Energy of the Korla Fragrant Pear
Preliminary research found that widely used corrugated boards can significantly reduce the impact damage to Korla fragrant pear, thereby protecting it. Hence, corrugated boards were chosen as the contact material to test impact deformation and deformation

Calculation of Impact Deformation Energy of the Korla Fragrant Pear
Preliminary research found that widely used corrugated boards can significantly reduce the impact damage to Korla fragrant pear, thereby protecting it. Hence, corrugated boards were chosen as the contact material to test impact deformation and deformation energy of the fragrant pear. It was assumed that only the body of the fragrant pear was in positive contact with the corrugated board in the impact process, and that the air resistance during impact and the difference in gravitational acceleration in different regions were ignored.
Using the test, the rebound height (h 2 ) to the highest point after first impact of the Korla fragrant pear to the corrugated board was obtained, and the impact deformation energy test value of the Korla fragrant pear was as follows: where E t -impact deformation energy test value of the Korla fragrant pear, J; m-mass of the Korla fragrant pear, kg; g-gravity acceleration, m/s 2 ; h 1 -falling height of the Korla fragrant pear, m; h 2 -rebound height of the first impact of the Korla fragrant pear to the highest point, m.
In order to determine the effect formula of weight and impact height on the rebound height of the Korla fragrant pear, different impact heights were tested. The fall height h 1 and rebound height h 2 were collected using a high-speed camera, 10 sets of parallel tests were conducted for each group, and the average was calculated.

Compression Test on the Korla Fragrant Pear
First, the picked pears were weighed and 100 pears that met the test requirements were selected as test samples. According to a weight and fruit size analysis of the Korla fragrant pear, clamping could be selected as transverse placement, as shown in Figure 3. The compression test was then conducted, and the compression rate was 5 mm/min. The relationship curve between the compression force and deformation of the Korla fragrant pear fruit was drawn, and the deformation energy of the pear was obtained using integral calculation. During pear compression, amounts of deformation were gradually increased until the pear was obviously deformed. Before the test, the WD-D3-7 universal compression testing machine was preheated for half an hour, and the steel plate indenter was used to compress the Korla fragrant pears placed horizontally on its base. After 100 fragrant pears were tested, the resulting data were averaged.
of the Korla fragrant pear, kg; g -gravity acceleration, m/s 2 ; h -falling height of the Korla fragrant pear, m; h -rebound height of the first impact of the Korla fragrant pear to the highest point, m.
In order to determine the effect formula of weight and impact height on the rebound height of the Korla fragrant pear, different impact heights were tested. The fall height h and rebound height h were collected using a high-speed camera, 10 sets of parallel tests were conducted for each group, and the average was calculated.

Compression Test on the Korla Fragrant Pear
First, the picked pears were weighed and 100 pears that met the test requirements were selected as test samples. According to a weight and fruit size analysis of the Korla fragrant pear, clamping could be selected as transverse placement, as shown in Figure 3. The compression test was then conducted, and the compression rate was 5 mm/min. The relationship curve between the compression force and deformation of the Korla fragrant pear fruit was drawn, and the deformation energy of the pear was obtained using integral calculation. During pear compression, amounts of deformation were gradually increased until the pear was obviously deformed. Before the test, the WD-D3-7 universal compression testing machine was preheated for half an hour, and the steel plate indenter was used to compress the Korla fragrant pears placed horizontally on its base. After 100 fragrant pears were tested, the resulting data were averaged.

Calculation of Compression Deformation Energy of the Korla Fragrant Pear
The Korla fragrant pear has thin skin, a fine, uniform pulp, and other characteristics which give them elasticity. When suffering from an external impact, it can resist a certain amount of external pressure. Prior experiments found that the body of the Korla fragrant pear is most susceptible to damage. In order to determine the relationship between deformation energy and deformation volume of the Korla fragrant pear, a universal material testing machine was used to conduct compression tests based on methods used by Bao Yudong et al. [28,29], as per Figure 3. The fragrant pear was gently placed on the loading plane of the universal material testing machine, with its body in direct contact with the lower plate indenter, and the stationary machine was started. Using this test, the

Calculation of Compression Deformation Energy of the Korla Fragrant Pear
The Korla fragrant pear has thin skin, a fine, uniform pulp, and other characteristics which give them elasticity. When suffering from an external impact, it can resist a certain amount of external pressure. Prior experiments found that the body of the Korla fragrant pear is most susceptible to damage. In order to determine the relationship between deformation energy and deformation volume of the Korla fragrant pear, a universal material testing machine was used to conduct compression tests based on methods used by Bao Yudong et al. [28,29], as per Figure 3. The fragrant pear was gently placed on the loading plane of the universal material testing machine, with its body in direct contact with the lower plate indenter, and the stationary machine was started. Using this test, the curve of compression force-deformation of the Korla fragrant pear was determined, as shown in Figure 4.
In addition, the equation of deformation energy of the Korla fragrant pear is shown in Equation (3): where: F-compression force, N; -deformation amount of the Korla fragrant pear, mm; -deformation energy of the Korla fragrant pear, J. The indenter of the universal material testing machine applied pressure to the Korla fragrant pear. With the gradual increase in deformation, the pressure applied to the fragrant pear in the direction of force was converted into its deformation energy. When the deformation energy applied to the fragrant pear exceeded the range it could withstand, the fragrant pear suffered mechanical damage. Moreover, with increasing compression force, the deformation energy inside the fragrant pear also gradually increased, and the degree of damage caused increased, as shown in Figure 4. Figure 4 shows that as the deformation of the fragrant pear gradually increased, it changed linearly before point B. However, the internal cell tissue of the fragrant pear at this stage underwent elastic deformation, and the internal cell tissue did not suffer damage. When reaching point B, the change curve of fragrant pears started to decline, and the pressure began to decrease. The beginning of the decline point was defined as the biological yield point where the internal tissue structure of the fragrant pear began to change, and the cell wall broke. The area of the curve enclosed by the horizontal coordinates between points A and B is the deformation energy, which was the maximum energy absorbed by the elastic deformation of the fragrant pear. The fragrant pear entered the plastic deformation stage after point B, which was not recoverable, and the damage increases with the increase in deformation amount and compression force. When the deformation amount increased to point C, the fragrant pear under pressure fell sharply and a rupture point was generated, with the pulp cell tissue suffering serious deformation. The area of the curve enclosed by the horizontal coordinates between points B and C is the damage energy.   (2):

The curvilinear equation of compression force and deformation of the Korla fragrant pear is shown in Equation
In addition, the equation of deformation energy of the Korla fragrant pear is shown in Equation (3): where: F-compression force, N; δ-deformation amount of the Korla fragrant pear, mm; E-deformation energy of the Korla fragrant pear, J. The indenter of the universal material testing machine applied pressure to the Korla fragrant pear. With the gradual increase in deformation, the pressure applied to the fragrant pear in the direction of force was converted into its deformation energy. When the deformation energy applied to the fragrant pear exceeded the range it could withstand, the fragrant pear suffered mechanical damage. Moreover, with increasing compression force, the deformation energy inside the fragrant pear also gradually increased, and the degree of damage caused increased, as shown in Figure 4. Figure 4 shows that as the deformation of the fragrant pear gradually increased, it changed linearly before point B. However, the internal cell tissue of the fragrant pear at this stage underwent elastic deformation, and the internal cell tissue did not suffer damage. When reaching point B, the change curve of fragrant pears started to decline, and the pressure began to decrease. The beginning of the decline point was defined as the biological yield point where the internal tissue structure of the fragrant pear began to change, and the cell wall broke. The area of the curve enclosed by the horizontal coordinates between points A and B is the deformation energy, which was the maximum energy absorbed by the elastic deformation of the fragrant pear. The fragrant pear entered the plastic deformation stage after point B, which was not recoverable, and the damage increases with the increase in deformation amount and compression force. When the deformation amount increased to point C, the fragrant pear under pressure fell sharply and a rupture point was generated, with the pulp cell tissue suffering serious deformation. The area of the curve enclosed by the horizontal coordinates between points B and C is the damage energy.

Scanning Electron Microscope Test of the Korla Fragrant Pear
Firstly, samples were prepared: one damaged part of each fragrant pear was selected as the sample, the peel of the Korla fragrant pear was removed using a scalpel, subcutaneous pulp tissue samples with a thickness of 1 mm and a length and width of 1 cm were selected and immersed in glutaraldehyde solution, and they were placed in a 4 • C refrigerator for 24 h. Secondly, samples were dehydrated: samples were dehydrated by a gradient using 40 min sequential immersions in 30%, 50%, 70%, 85%, 95%, 100%, and 100% anhydrous ethanol. Thirdly, samples were dried: the samples were removed from 100% anhydrous ethanol to the equivalent drying instrument for drying, and dried immediately. Fourthly, samples were gold plated: after the drying was completed, the ion sputtering instrument was used to coat the surface of the fragrant pear samples to achieve a consistent coating material and thickness for observation. Fifthly, samples were observed: the scanning electron microscope was opened and the settings for illumination, focus, and angle were adjusted. the sample tissue was observed through the scanning electron microscope, using different magnifications to view the damaged areas of the sample (1000× pixels was used in this paper). During the scanning electron microscope test, the observed data needed to be recorded. After completing the scanning electron microscope test, the scanning electron microscope was turned off and any recorded data were saved. Figure 5 shows that when the mass of the Korla fragrant pear was certain, an increase in impact height within the test range resulted in an increase in the rebound height. Within the test range, there is a linear relationship between the fall height and the rebound height of the fragrant pear, with the rebound height gradually increasing as the fall height increased. The fitting equation R 2 = 0.9951 of the fall and rebound heights of the fragrant pear indicated a good degree of fitting, and the relationship between these heights were accurately characterised. microscope test, the scanning electron m were saved. Figure 5 shows that when the mass in impact height within the test range res the test range, there is a linear relationsh of the fragrant pear, with the rebound increased. The fitting equation R 2 = 0.995 pear indicated a good degree of fitting, accurately characterised. Based on the above results, the reb under different impact heights was clar fall height on the impact deformation en heights and the deformation energy of (1), as shown in Figure 6. Figure 6 shows that there is a li deformation energy of the Korla fragra increasing impact deformation energy w R 2 = 0.9958 of the fall height and deforma degree of fitting, and the relationship b were accurately characterised.

Calculation of the Damage Volume of th
Given that the shape of the fragran  Figure 6 shows that there is a linear relationship between the fall height and deformation energy of the Korla fragrant pear within the test range, with a gradually increasing impact deformation energy with an increased fall height. The fitting equation R 2 = 0.9958 of the fall height and deformation energy of the fragrant pear indicated a good degree of fitting, and the relationship between the fall height and deformation energy were accurately characterised.

Calculation of the Damage Volume of the Korla Fragrant Pear
Given that the shape of the fragrant pear damage is three-dimensional, the damage volume was used as an evaluation index to accurately reflect the impact damage [30], and the fragrant pear was ranked. After impact, the fragrant pear was placed at room temperature for 24 h. After removing the peel of the fragrant pear, a brown colour at the damaged area could be observed, while the undamaged area remained unchanged. Hence, the volume of the browning area was measured as the damage volume. The depth (d) of the browning area of the fragrant pear, the long axis (a) of the damaged area, and the short axis (b) of the damaged area were measured with an electronic vernier calliper. The damage volume was calculated using Equation (4), according to a method by Mahdi [31].
where d-depth of the damaged part, mm; a-long axis of the damaged part, mm; b-short axis of the damaged part, mm. The static and impact damage volumes of the fragrant pear were calculated using the above method, and the relationship curve of damage energy and damage volume was drawn, as shown in Figure 7. When the damage energy of the fragrant pear was between 0 and 159.4 × 10 −3 J, the deformation energy generated before the fragrant pear reached static pressure generated a small biological yield point, and the damage volume could not be measured. On the other hand, when the damage energy of fragrant pear was 159.4 × 10 −3 J, the static pressure caused damage and generated the damage volume. Similarly, when the damage energy was between 0 and 205.89 × 10 −3 J, the damage energy at impact was small, and the damage volume could not be measured. On the other hand, when the damage energy was 205.89 × 10 −3 J, the impact caused damage and generated the damage volume. Moreover, when the damage energy was 380.88 × 10 −3 J, the static damage and impact damage volumes were the same; and, when the damage energy was greater than 498.23 × 10 −3 J, the static deformation volume reached the threshold value and rupture occurred. Upon rupture, the compression force dropped sharply, the compression test ended, and the impact damage volume was greater than the static damage volume.
Horticulturae 2023, 9, x FOR PEER REVIEW correlation and indicating that the impact damage predicted using the fitting equation. Hence, the imp be studied using the research method for static dama  The resulting static damage volume was linearly fitted to the impact damage volume over a range of different damage energies. As shown in Figure 8, when the damage energy was 159.4-608.7 × 10 −3 J, the coefficient of determination of the static and impact damage volumes was R 2 = 0.9590, indicating a good correlation. As shown in Figure 9, in order to characterise the correlation between the static damage and impact damage volumes in this damage energy range, the mathematical equation between the two was established, and showed that the damage energy was 203.4-498.23 × 10 −3 J. The coefficient of determination of the static pressure and impact damage volume was R 2 = 0.9944, showing a good correlation and indicating that the impact damage volume of the fragrant pear could be predicted using the fitting equation. Hence, the impact damage of the fragrant pear can be studied using the research method for static damage to simplify the method for impact damage.

Verification of the Damage Volume in the Korla Fragrant Pear Impact Test
Static deformation volumes of 4.5 mm, 5 mm, 5.5 mm, 6 mm, and 6.5 mm were selected to carry out the static damage test of the fragrant pear, as well as static damage energies of 203.4 × 10 −3 J, 255.69 × 10 −3 J, 316.38 × 10 −3 J, 380.88 × 10 −3 J, 458.97 × 10 −3 J, and 498.23 × 10 −3 J using the integral calculation, thereby measuring the static damage volume. The predicted impact damage volume of the fragrant pear was calculated using the fitting equation in Figure 9. The equivalent fall height corresponding to the impact was obtained from the deformation energy, and the impact test was carried out through the corresponding equivalent height to measure the actual volume of impact damage, as shown in Table 2. Table 2 shows that the damage energies were between 203.4 × 10 −3 J and 498.23 × 10 −3 J, and the free fall heights were between 30.58 and 81.07 cm. Moreover, the maximum deviation between the predicted impact damage volume and the actual impact damage volume was 4.4%, and the free fall damage of the fragrant pear was studied using the static damage.

Microstructure Analysis of Korla Fragrant Pear Samples Using a Scanning Electron Microscope
The tissue samples of the Korla fragrant pear after static and impact damage were scanned using an electron microscope, and microstructures were compared with samples of undamaged fragrant pears, as shown in Figure 10. Figure 10a shows an undamaged fragrant pear, with closely distributed structures of cell space and cell walls of the pulp tissue, regular cell arrangements, and denser stomatal clusters, which differed greatly from the damaged fragrant pear. Figure 10b shows a static damage of 255.69 × 10 −3 J, with the fragrant pear stomata being both open and closed, the cells of the pulp tissue were slightly damaged, and the cells had obvious folds. Figure 10c shows an impact damage of 255.69 × 10 −3 J, with the cells of the pulp tissue being slightly damaged and partially collapsed, and the degree of damage slightly smaller than that in Figure 10b. Figure 10d,e shows a static and impact damage of 380.88 × 10 −3 J, with the cells of fragrant pear tissue being vastly destroyed, and almost no intact cell structures, albeit without obvious differences in the degree of damage. Figure 10f shows a static damage of 540.23 × 10 −3 J, with the whole cell tissue of the fragrant pear showing obvious collapse and folds and disappearance of the cell spaces. Figure 10g shows an impact damage of 540.23 × 10 −3 J, with the whole cell tissue showing obvious collapse and folds, no cell space, and a degree of damage slightly larger than that in Figure 10f. Using the scanning electron microscope test, it was observed that the form of static pressure, impact load, and the fragrant pear damage mechanism were the collapse and folding of cell tissue structures, with no significant differences in the degree of damage under the same damage energy. Horticulturae 2023, 9,

Discussion
During the harvesting, transportation, and storage of the Korla fragrant pear pears, they can be vulnerable to different types of impact damage. For example, there can be impact damage between fruit and fruit, fruit and packaging materials, and fruit and the ground. Although there are various forms of damage, there is a certain relationship between damage energy and damage volume. In this study, it was experimentally concluded that when the damage energy is in the range of 203.4-498.23 × 10 −3 J, if the free fall damage and the static pressure damage have the same energy, the free fall damage can be equated to the static pressure damage. It can shorten the detection time, improve the damage detection efficiency and accuracy, provide a new research method for the impact damage detection of the Korla fragrant pear, and provide a new idea for the unified research of different forms of impact damage. However, the equivalent static pressure damage of the Korla fragrant pear under different damage conditions still needs to be studied according to the actual damage form.
The material that comes into contact with the Korla fragrant pear has a significant impact on its rebound height. The normal load of the Korla fragrant pear varies depending on the contact material, resulting in differing rebound heights. Chen Chun Hao and his team discovered that when the contact material is pearl cotton, fake lawn, silicone rubber,

Discussion
During the harvesting, transportation, and storage of the Korla fragrant pear pears, they can be vulnerable to different types of impact damage. For example, there can be impact damage between fruit and fruit, fruit and packaging materials, and fruit and the ground. Although there are various forms of damage, there is a certain relationship between damage energy and damage volume. In this study, it was experimentally concluded that when the damage energy is in the range of 203.4-498.23 × 10 −3 J, if the free fall damage and the static pressure damage have the same energy, the free fall damage can be equated to the static pressure damage. It can shorten the detection time, improve the damage detection efficiency and accuracy, provide a new research method for the impact damage detection of the Korla fragrant pear, and provide a new idea for the unified research of different forms of impact damage. However, the equivalent static pressure damage of the Korla fragrant pear under different damage conditions still needs to be studied according to the actual damage form.
The material that comes into contact with the Korla fragrant pear has a significant impact on its rebound height. The normal load of the Korla fragrant pear varies depending on the contact material, resulting in differing rebound heights. Chen Chun Hao and his team discovered that when the contact material is pearl cotton, fake lawn, silicone rubber, or bubble film, the damage from dropping apples at different heights differs greatly [32]. This research was conducted under specific contact material conditions and cannot fully characterise the impact damage caused to the Korla fragrant pear in actual production. However, this research method can be referenced for specific research in actual production.

Conclusions
Within the range of test parameters, when the damage energy was 205.89 × 10 −3 J, the impact damage volume of fragrant pears was generated, and when the damage energy was 159.4 × 10 −3 J, the static pressure damage volume of fragrant pears was generated. The damage energy was in the range of 203.4 × 10 −3 J-498.23 × 10 −3 J, the free fall height was in the range of 30.58-81.07 cm, the static pressure damage volume of fragrant pears was linearly correlated with the impact damage volume, and the correlation coefficient R 2 was 0.9944. When the damage energy was 380.88 × 10 −3 J, the static and impact damage volumes were both 2728.54 mm 3 . It was found by scanning electron microscope that there was no significant difference in the damage degree of fragrant pears under static pressures and impact loads using the same damage energy. This study uses static pressure damage to label impact damage and attempts to reveal the relationship between static pressure damage and impact damage. It is an exploration of theoretical methods and can be applied in many aspects, such as the detection and prediction of impact damage in the process of harvesting and storage of the Korla fragrant pear. It can also provide reference for the impact damage research of other fruits and is an attempt to create a new method.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.