The force exerted on a cylindrical intruder as it penetrates a granular medium was analyzed utilizing both experiments and the discrete element method (DEM). In this work, a series of penetration experiments were performed, considering cylindrical intruders with different nose shapes. We found that the drag force of the intruder with a hemispherical nose is close to that of those with conical noses with apex angles of 53° and 90°. The drag force of the blunt-nosed intruder is bigger; the drag force of the conical-nosed intruder with an apex angle of 37° is the smallest. We studied the interplay between the drag force on an intruder with a hemispherical nose and key variables—the penetration velocity (V), penetrator’s diameter ($d_{\mathrm{i}}$), and friction coefficient (μ). From this analysis, two piecewise functions were derived: one for the average drag force versus the penetration velocity, and the other for the scaled drag force versus the friction coefficient. Furthermore, the average drag force per contact point, F_a/P, can be succinctly represented by two linear relationships: F_a/P = 0.232$\mu$ + 0.015(N) for $\mu <0.9$, and F_a/P = 0.225(N) for $\mu \ge 0.9$.

Soil organic cover technology is an effective way to solve agricultural productivity and agro-environmental issues. However, some factors limit the widespread adoption of its application, including unclear soil organic cover effects and the lack of high-performance soil organic cover machinery. Aiming to solve the existing problems, improve soil organic cover quality, and reduce energy consumption, this article reviewed the common and commercial machines by reviewing the existing literature and company products. The current problems and technical difficulties of the machines were expounded. Simultaneously, the method of design and optimization of the device (chopper, spreader, rotary tiller, and plow) and its key parts (blades, discs, and plows) were reviewed. Furthermore, the features and differences of the devices and their key parts were compared, and their advantages and disadvantages were analyzed. In conclusion, the future directions for soil organic cover technology and machinery development were suggested, including clarifying the soil organic cover effect, selecting the suitable soil organic cover patterns, and developing soil organic cover machinery.

In this study, a brass or glass spherical impactor vertically penetrating into a granular bed composed of mono-sized spherical or elongated particles was simulated with three-dimensional (3D) discrete element method (DEM). Good agreement of the particle masses in the cup before and after penetration can be found in the simulations and experiments. The effects of particle length (L_p), friction coefficient, and particle configuration on the penetration depth of the impactor, ejecta mass, and solid volume fraction describing the response of the granular bed are discussed. The penetration depth is negatively correlated with L_p as the corresponding solid volume fraction of the granular bed decreases. A smaller friction coefficient leads to a larger penetration depth of the impactor and more ejection of particles. When the impactor is penetrating the L_p = 10 mm elongated particles, the penetration depth is negatively correlated to the order parameter and solid volume fraction.