During residual film recovery operations, the mixing of residual film with soil and the absence of accurate interaction parameters significantly hinder the optimization of key machinery components. To tackle this issue, this study develops a discrete element simulation model based on the Hertz–Mindlin with JKR (Johnson-Kendall-Roberts) contact model, using the residual film-soil mixture as the simulated material. The contact parameters were calibrated through a combination of physical experiments and EDEM simulations. Using Design-Expert software, angle of repose tests and Plackett–Burman experiments were carried out to identify the parameters that have a significant influence on the angle of repose. The optimal set of parameters was determined through steepest ascent and Box–Behnken design (BBD) experiments: residual film–soil rolling friction coefficient 0.61, soil–soil rolling friction coefficient 0.60, soil–steel static friction coefficient 0.68, and soil JKR surface energy 0.46 J/m². Validation results indicate relative errors of 4.58% for the angle of repose and 2.58% for the uniaxial compressive strength between simulated and measured values. These outcomes offer a useful reference for optimizing residual film recovery equipment and for modeling soil–residual film composite materials.

In order to solve the problems of unclear film separation in traditional topsoil residual film recovery machine and secondary broken film caused by the toot-shaped structure, a film-soil conveying and vibration separation device was designed. It mainly consists of a first-level vibration conveying chain, roller extrusion and crushing mechanism and secondary conveyor chain, which can complete the functions of conveying, vibration separation, and crushing separation of film-soil composite. Firstly, the mechanical model of the transport process of the film-soil composite was established, and the transport stability of the film-soil composite was analyzed. The vibration characteristics of the vibration mechanism were analyzed by analytical method, and the vibration model of the vibration mechanism was established. The distribution state of residual film-soil mixture was observed and measured by high-speed camera, and the influence of vibration wheel speed and installation distance on the distribution height of residual film-soil mixture was found out. The crushing mechanism of the residual film-soil composite was proved by studying the roller extrusion and crushing mechanism. The Box-Behnken response surface test method was used to carry out field tests on the transport and vibration separation device of film-soil with soil content rate and film leakage rate as evaluation indices. The results indicated that the influencing factors on the soil content rate in a descending order are conveyor chain speed, vibration wheel speed, and installation distance. In contrast, the factors affecting the film leakage rate, also ranked from largest to smallest, are conveyor chain speed, installation distance, and vibration wheel speed. The combination of film-soil separation parameters is as follows: conveying chain speed is 1.6 km/h, vibration wheel speed is 189.7 r/min, installation distance is 769.7 mm, at this time the soil content rate is 18.31%, and the film leakage rate is 9.49%, which meet the requirements of the recovery of residual film in the plough layer. The conveying and vibration model established in this study can provide a theoretical basis and technical reference for elucidating the soil-film separation process.

During the harvesting process, rigid materials are prone to causing damage to the cotton stalks, which will increase the risk of stalk breakage. A cotton stalk pulling component that blends stiff and flexible materials was devised to lower the breaking rate. The cotton stalk pulling component was made up of rollers and flexible belts that pull the stalks using clamping force and the forward speed of the tractor. The influence of various factors in the equipment on the harvesting effect of cotton stalks were analyzed through response surface experiments, and a multiple quadratic regression response surface model with missing pulling rate and breakage rate as response values was established. The significant of influencing factors on the breaking rate of cotton stalks are in a descending order as: the angle of cotton stalk pulling, tractor’s forward speed, and the clamping speed of the cotton stalk component. The working parameters of the wheel-belt type cotton stalk pulling machine have been optimized using the response surface combination experimental method, and the optimal parameter combination was obtained as: tractor forward speed of 4.5 km/h, cotton stalk pulling angle of 60°, and clamping speed of the cotton stalk pulling component of 349 r/min. The results of validation experiments showed that the missing pulling rate of cotton stalks was 5.06% and the breakage rate was 13.12%, indicating a good harvesting effect of the cotton stalks. The model was reasonable and the performance parameters could meet the relevant inspection requirements. The results can provide a reference for further research on the technology of flexible cotton stalk pulling.