The effects of the spiral line for pick arrangement on the cutting load of a boom type roadheader's cutting head were investigated. For this purpose, cutting heads with equal and unequal pitch angle and various numbers of spiral lines were designed for the same cutting head body. The cutting head with unequal pitch angle of spiral lines was specifically designed to avoid tool-holder overlap at the top section without adjustments and reduce the manufacturing difficulties. The cutting process of different cutting heads were simulated by finite element method using ANSYS/LS-DYNA and the time history curve of the traversing force, vertical force, axial force, and resultant force on the cutting head were obtained. The results indicate that the load stability of the cutting head with unequal pitch angle was worse than the equal pitch angle cutting head. For cutting heads with various numbers of spiral lines, the head with 3 spiral lines shows the best performance, considering the force values and fluctuations of the cutting head. The analysis provides a reliable basis for optimization of the design of boom type roadheader cutting heads.

The spur gear mechanism with the standard involute profile may generate noise and shock because of tooth structure and transmission principle, resulting in substantial transmission errors. These limitations can be effectively resolved through tooth profile modification. To address the defects and deficiencies of existing tooth profile modification methods in terms of the modification principle and effect assessment, this study proposes an adaptive method of tooth profile modification with alterable tooth profile for spur gear mechanism. A corresponding simulation method for evaluating the modification performance of the gear transmission was introduced in detail. The final shape parameters of the modification profile were determined by orthogonal experiments. Simulation results show that tooth profile modification for involute spur gear does not affect bending and contact stresses. The process can also effectively improve the stability of transmission. The impact and noise of gear pair with tooth profile modification significantly decreased during meshing. The proposed method exhibits stronger adaptability compared with other existing methods of tooth profile modification. Moreover, the proposed method can adaptively determine the optimal modification parameters based on different conditions and obtain the ideal modification effect.

The material in the carburized layer of a carburized gear is nonlinear. However, no systematic theory and method is available to analyse the strength of nonlinear materials; thus, calculating the exact strength of carburized gears is difficult. The traditional method of calculating the strength of carburized gears considered the material as uniform, which is susceptible to make errors. To address this problem, a hierarchical simulation method was proposed to calculate the strength of carburized gears. The strength calculation principle of carburized gears was first analysed. Then, a solid modelling method of carburized gears was presented based on the extraction technology of the layered homogeneous material. Finally, the meshing process of carburized gears was simulated, and the distribution and variation laws of the root, contact, and shear stresses during the meshing process were determined accurately. Results show that the shear stress of carburized gears initially increases and then decreases along with depth direction, and the maximum value appears in the surface below. However, the shear stress of non-carburized gears decreases linearly. The equivalent stress of the two kinds of gears decreases linearly with depth direction, whereas the decreasing amplitude of the carburized gears is larger than that of the non-carburized gears. A significant error in the calculation of the strength of carburized gears can be clearly observed using the traditional method. By selecting the appropriate parameters, the method proposed in this study can be used to simulate the meshing process of the carburized gear pair and calculate its strength accurately.

An improved expanding ring experimental technique has been described to determine dynamic material properties under conditions approximating uniform one-dimensional tensile loading. There are mainly explosive expanding ring technique and electromagnetic expanding ring technique currently, for which exist many limitations in practical applications. The work reported herein is an attempt to overcome this difficulty by lateral efficiency loading produced by projectile, made of low-density material, impacting the same material filling. The lateral efficiency loading is a convenient and effective method, which allows materials to be in uniform uniaxial stress conditions at a high stress rate. The procedure is illustrated by experiments performed on 1100-0 aluminum rings.