Ultrasonic cutting with a straight blade is an advanced method for cutting Nomex honeycomb cores. However, crushing has generally been observed on the machining surface of the honeycomb core during ultrasonic cutting (UC). In this paper, to avoid crushing, a new blade-inclined ultrasonic cutting (BIUC) method is proposed to decrease the geometric interference between the cutting tool and the honeycomb cores. The cutting geometry systems of UC and BIUC with a straight blade are systematically established to study the effect of the cutting geometry on the machining quality. The crushing degrees caused by the major flank under different tool orientations in UC and BIUC are analyzed. The causes of crushing during the machining of the honeycomb core were revealed from the aspects of machining quality, cutting force, and geometric interference between the major flank and the material. Experiments involving the quantitative analysis of the crushing and cutting forces verify that the BIUC method is able to avoid crushing by controlling the cutting angle. This paper provides a new method for solving the crushing problem in machining honeycomb core with a straight blade.

Abrasive flow machining (AFM) is a nontraditional surface finishing method that finishes complex surface by pushing the abrasive media flow through the workpiece surface. The entrance effect that the material removal increases at the entrance of changing the cross-sectional flow channel is a difficult problem for AFM. In this paper, the effects of media rheological properties on the entrance effect are discussed. To explore the effects of the media's viscoelasticity on the entrance effect, two sets of media with different viscoelasticity properties are adopted to study their rheological and machining performances in the designed flow channel with a contraction area. The rheological properties are tested by frequency sweep and characterized by the Maxwell viscoelastic model and the Carreau viscous model. In the experiment, the variation of the profile height (ΔH) and the variation ratio of the roughness (ΔRa) on the workpiece surface are measured. Moreover, numerical simulation results under different constitutive equations are compared with the experimental results. It shows that the numerical simulation results of a viscoelastic model have a better agreement with the experimental results than the viscous model, and the increase of the viscoelasticity makes the entrance effect be exacerbated, which can be predicted by the viscoelastic numerical simulation.

The aeroengine industry has set strict upper limits for assembly errors in rotor-connecting processes, because assembly errors significantly affect aeroengine stability. Applications of multi-axis mechanisms have the potential to solve the low efficiency of traditional manual connection processes. However, multiple error sources are simultaneously introduced. Thus, an accurate prediction method of rotor assembly error considering multiple error sources is of vital importance, by which the applicability of the new mechanism to rotors can be tested. In this study, a new prediction method for rotor assembly errors is proposed based on the use of a novel multi-axis measuring and connecting mechanism. First, the error propagation among the rotor errors, measurement errors, mechanism errors, and mounting errors is analyzed. Second, reasonable characterization models for these error sources are established using homogeneous transformation matrices. Third, based on the abovementioned error models, a new rotor assembly error prediction algorithm is constructed. It is highly consistent with the actual connection processes. Finally, verification experiments are conducted. The experimental results show that deviation rates of the average values of six types of assembly errors relative to the predictions are all lower than 14%. The proposed prediction method has acceptable accuracy and practical significance.