Development of TiB and nanocrystalline Ti-reinforced novel hybrid Ti nanocomposite produced by powder metallurgy

Titanium monoboride (TiB) whisker-reinforced titanium (Ti) matrix composites were produced by powder metallurgy, through vacuum sintering. TiB is formed by thermal decomposition of TiB2 precursor. In addition, a new hybrid composite was developed by admixing nanograined and nanocrystalline (more important) Ti to enhance the transformation mechanism of TiB2 to TiB phase. The morphology and particle size of the initial powders, mixtures and the microstructure of the composites have been studied by scanning electron microscopy (SEM). The phase analysis and transformation monitoring were performed by X-ray diffraction (XRD). The sintered composites were also subjected to compressive strength and hardness measurements. According to XRD results, through the addition of nanocrystalline Ti, a probable enhancement of the TiB2 → TiB transformation occurred producing more TiB whiskers in the hybrid composites. All samples of the hybrid composites exhibited improved yield strength (1365 MPa) and hardness (358 HV) compared to the non-hybrid ones 927 MPa and 254 HV, respectively. Graphical abstract

Bionic design and analysis of a multi-posture wheelchair

Posture transformation is an essential function for multi-posture wheelchairs. To improve the natural motion in posture transformation that is a popular problem in the design of multi-posture wheelchairs because the current wheelchair's posture transformation mechanism cannot remain consistent between the rotation center of the wheelchair and the rotation center of the human body joints. This paper proposes a sitting–standing–lying three-posture bionic transformation mechanism for a smart wheelchair. A human–wheelchair coupling model is described and analyzed according to the biomechanical characteristics of the posture transformation of human beings and their functional requirements. The configuration of the transformation mechanism is chosen by comparing the trails of the wheelchair rotation centers and the corresponding human joint rotation centers. The kinematics of the optimized configuration are discussed in detail to obtain the most bionic motion performance using the multivariable nonlinear constraint optimization algorithm. Finally, the mechanism is designed, and its posture transformation performance is simulated and verified using Adams (Automatic Dynamic Analysis of Mechanical Systems) software.