The contact process of stator and slider described by the Coulomb friction model is basically in a pure sliding friction state, and a mechanical model based on the Dahl friction theory was proposed to describe the contact process between stator and slider of V-shape linear ultrasonic motor. With consideration for the tangential compliance of stator and slider, the dynamic contact and friction processes of stator and slider were addressed in stages. The simulation results show that the ratio of the friction positive work decreases with the increase of the preload, and the vibration amplitude of the stator increases the proportion of positive work of the friction force. Improving the contact stiffness of the stator and slider is conducive to improving the output performance of the ultrasonic motor. The asymmetry of the left and right performance of the V-shaped vibrator will cause a difference in the left and right running speeds of the ultrasonic motor. The improved Dahl friction-driving model makes up for the discontinuity of tangential contact force calculated by the Coulomb friction model. This study demonstrates that the friction-driving model based on the Dahl theory is reliable and reasonable for linear ultrasonic motors according to the experimental results.

Pre-stress shot peen forming is an effective plastic forming method for integral panels with stiffeners used in aeronautical industry. 7050 aluminum alloy panels with stiffeners were pre-stress peen formed in an orthogonal experiment. The deformation rule of those workpieces whose exterior surfaces were convex bending was investigated. The results show that the contribution of peening parameters on workpiece deformation is in following order: air pressure, pre-load stress and moving velocity of workpiece. The deformation of workpiece whose merely exterior surface is peened is much lower than that whose two side-faces of stiffener are also peened. The decreasing rate is changed from 13% to 39% by means of parameters variation. Moreover, the regression formulas about the quantitative relationships between radius of curvature and peening parameters have been established. The results could offer some basic reference to peen forming aluminum alloy panels of future aircrafts.

This paper investigates the effect of retrogression time on the fatigue crack growth of a modified AA7475 aluminum alloy. Tests including tensile strength, fracture toughness, and fatigue limits were performed to understand the changes in properties with different retrogression procedures at 180 °C. The microstructure was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The findings indicated that as the retrogression time increased, the yield strength decreased from 508 MPa to 461 MPa, whereas the fracture toughness increased from 48 MPa√m to 63.5 MPa√m. The highest fracture toughness of 63.5 MPa√m was seen after 5 h of retrogression. The measured diameter of η’ precipitates increased from 6.13 nm at the retrogression 1 h condition to 6.50 nm at the retrogression 5 h condition. Prolonged retrogression also increased the chance of crack initiation, with slower crack growth rate in the long transverse direction compared to the longitudinal direction. An empirical relationship was established between fracture toughness and the volume fraction of age-hardening precipitates, with increasing number density of precipitates seen with increasing retrogression time.

In this study, a series of optically transparent metallized acrylics containing Gd and Pb were synthesized by the bulk polymerization of Gd(MAA)₃, Pb(MAA)₂ and AM according to different polymerization procedures. The variation of their optic transmittance and mechanical performance with Gd contents was investigated. Then, quasi-static uniaxial tensile tests under different strain rates and temperatures were performed to study the influence of strain rate and temperature on the mechanical properties of radiation-shielding metallized acrylic containing both Gd and Pb. The tensile responses of this material distinctly exhibit nonlinear characteristics and strongly depend on both temperature and strain rate. Based on the experimental results, a modified Zhu–Wang–Tang (ZWT) constitutive model, in which the standard elastic component was replaced by the Mooney–Rivlin hyperelastic model, was implemented to characterize the observed both hyperelastic and viscoelastic behaviors. The constitutive parameters were expressed as functions of temperature and determined by experimental data. The model fitting results indicate that the selected constitutive model can accurately describe the nonlinear tensile stress–strain responses of metallized acrylic containing Gd and Pb. Furthermore, the great difference in constitutive parameters implies that the viscoelastic behavior of the as-prepared metallized acrylic affects the response to quasi-static tensile loading the most.

Titanium alloy profiles are widely applied as airframe parts due to its excellent mechanical properties and high compatibility of electrical potential with resin composite material. The electrical assisted forming is recognized as the effective approach to improve plasticity of titanium alloy profile. In this work, the electo-thermal uniaxial tension was performed to investigate the mechanical properties. The experiment results show that, the stress-strain curves increases sharply to the peak and declines quickly, exhibiting no stable deformation occurring. On basis of the obtained curves, a constitutive equation was established with consideration of the characteristic of self resistance heating, and the microstructure evolution was predicted. A comparison of the calculated stress-strain curves with the experimental ones was conducted, showing a reasonable agreement.

Various heat treatments were applied to reduce quench-induced residual stresses while improving the mechanical properties of particle-reinforced aluminum composite. The residual stress distribution of samples quenched in water with different cooling media was measured. The results showed that quenching with the 30% polyethylene glycol quenchant (PAG) yields up to an 86.8% reduction in residual stress magnitude compared with cold-water quenching (CWQ). Still, the tensile properties of samples quenched in 30% polyethylene glycol quenchant were low, with a 12.5% reduction in yield strength. The experimental results show that the uphill quench (UQ) method is an effective means of reducing residual stresses induced by quenching. At the same time, the effect on tensile properties is negligible. Moreover, the study found that combining uphill quenching with short-aging treatment can further improve the residual stress, strength, and fracture toughness of SiCp/Al-Cu-Mg composites.