Abstract The productivity and efficiency of harvesting forage crops depend on the sharpness and quality of the mower blades. Therefore, studying blade wear during Alfalfa harvesting is crucial to sharpening and maintaining blades. This research aims to create mathematical models to predict the wear of mower blades and assess the wear rate of mower blades, fuel consumption, and CO 2 emissions during the harvesting operation. Blade wear was measured by the weight loss method and examined by scanning electron microscopy (SEM) before and after the field experiment. The results showed that the weight of the mower blade decreased from 103.82 to 98.39 g after 37.5 working hours. Over time, fuel consumption and operating costs increased due to the wear of blades. Also, CO 2 emissions were 17.7 kg h −1 at the beginning of the experiment and increased to 29.5 kg h −1 after 37.5 working hours. Due to wear in the blades, the increase in fuel consumption, cost, and CO 2 emissions reached 67% at the end of the experiment. From the obtained mathematical equations, the sharp part of the blade has worn out after 34 ± 3 working hours. Graphical abstract
MoS2 coating is a newly developed method to prevent bolt corrosion and the seizure of bolts used in equipment in sea areas. It is of great significance to investigate the evolution of the tensile properties and intact coatings for the maintenance of coated bolts. To evaluate the tensile properties of MoS2-coated titanium alloy bolts, titanium alloy bolts coated with MoS2 (TC4+MoS2) and bolts treated with a composite treatment of anodizing oxidation and MoS2 coating (TC4+AO+MoS2) were corroded in salt spray tests for 4300 h. The MoS2 coating significantly enhanced the bolts’ corrosion resistance, demonstrating exceptional protective performance by only experiencing minor peeling due to oxidation-induced cracking of the coating during the extensive 4300 h salt spray test. The tensile strengths of the TC4+MoS2 and TC4+AO+MoS2 bolts both decreased as compared with the original bolts. The bolts pretreated with anodic oxidation revealed lighter coating peeling and maintained a higher tensile strength after corrosion. Therefore, it can be concluded that the coatings provided excellent corrosion resistance, leading to a minor impact on the bolts’ tensile strength and fracture behavior under the synergistic damage of sea water corrosion and preloading.
A series of molecular dynamics simulations are carried out to investigate the plastic deformation in wurtzite GaN. Besides the formation of an amorphous zone under the contact region, plastic slips nucleated on the m plane (10-10), c plane (0001), r plane (10-12), and s plane (10-11) are observed in the indentation. Combined with a close analysis of critical stress that induces a specific slip on different crystalline planes, the defect evolution is discussed in detail. Slip systems of [10-1-1](10-12) and 1/3[2-1-1-3](10-11) on the pyramidal planes are not supposed to nucleate easily since higher stress is required to activate them. However, a significant decrease in the shear stress that induces a pyramidal slip could be expected if the slip evolves gradually following a two-step procedure. The gradual slips on both the r plane (10-12) and s plane (10-11) are observed in our indentation simulation; the mechanism is studied by the calculation of generalized stacking fault energy.
Pin-on-disc experiments are conducted to investigate the tribological performance of untextured and textured brass surfaces with TiN coatings under oil lubrication. The surface texture is designed as a dimple pattern with different diameters and depths for the transverse surfaces of brass pins. After texturing, a TiN coating is deposited through pulsed-bias arc ion plating in a pure N2 atmosphere using a Ti target. Three dimple diameters are used, namely 130 μm, 150 μm, and 170 μm, along with three dimple depths, namely 15 μm, 40 μm, and 60 μm. The TiN coating is around 5 μm thick. Friction tests are conducted under different rotation speeds and loads, and the interfacial adhesion is assessed via a scratch test. Compared to the untextured surface, the textured one offers improved tribological behavior in mixed lubrication because the dimples generate hydrodynamic lift. To reduce friction in the case of higher speed and lower load, the optimum texture parameters are a diameter of 150 μm and a depth of 40 μm.
Limited by the inefficiency of the conventional trial-and-error method and the boundless compositional design space of high-entropy alloys (HEAs), accelerating the discovery of superior-performing high-entropy nitride (HEN) coatings remains a formidable challenge. Herein, the superhard HEN coatings were designed and prepared using the rapidly developing data-driven model machine learning (ML). A database containing hardness and different features of HEN coatings was established and categorized into four subsets covering the information on composition, composition-physical descriptors, composition-technique parameters, and composition-physical descriptors-technique parameters. Feature engineering was employed to reduce dimensionality and interpret the impact of features on the evolution of hardness. Both root mean squared error (RMSE) and decision coefficient (
Understanding the impact of irradiation and temperature on the mechanical properties of GaN single crystals holds significant relevance for rational designs and applications of GaN-based transistors, lasers, and sensors. This study systematically investigates the influence of C-ion irradiation and temperature on pop-in events, hardness, Young's modulus, and fracture behavior of GaN single crystals through nanoindentation experiments. In comparison with unirradiated GaN samples, the pop-in phenomenon for ion-irradiated GaN samples is associated with a larger critical indentation load, which decreases with increasing temperature. Both unirradiated and ion-irradiated GaN samples exhibit a decline in hardness with increasing indentation depth, while Young's moduli do not exhibit a clear size effect. In addition, intrinsic hardness displays an inverse relationship with temperature, and ion-irradiated GaN single crystals exhibit greater intrinsic hardness than their unirradiated counterparts. Our analysis further underscores the significance of Peierls stress during indentation, with this stress decreasing as temperature rises. Examinations of optical micrographs of indentation-induced fractures demonstrate an irradiation embrittlement effect. This work provides valuable insights into the mechanical behavior of GaN single crystals under varying irradiation and temperature conditions.
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