Characteristics of an Accelerated Transverse Mechanical Pulse and Its Implications

In this report, two nontraditional mechanical wave-related issues are addressed. 1) Customary, for practical reasons the characteristics of the sinusoidal pulses progressing at a constant speed only is considered. And 2) the literature search shows that there has been no interest in exploring the characteristics of the pulses in a curvilinear two-dimensional space. By relaxing the first restriction we consider a scenario that which a mechanical pulse progresses with variable speed, specifically at a constant acceleration. We develop its equation of motion conducive to a homogenous linear partial differential equation with variable coefficients then we apply it to a practical problem. To address the 2nd point we depict a circular orbital embodying two Gaussian pulses circulating in opposite directions. Utilizing a Computer Algebra System (CAS), Mathematica, we develop animations visually easing the comprehension of the issues on hand.

Microstructure and Properties of the Cr–Si–N Coatings Deposited by Combining High-Power Impulse Magnetron Sputtering(HiPIMS) and Pulsed DC Magnetron Sputtering

The Cr–Si–N coatings were prepared by combining system of high-power impulse magnetron sputtering and pulsed DC magnetron sputtering. The Si content in the coating was adjusted by changing the sputtering power of the Si target.By virtue of electron-probe microanalysis, X-ray diffraction analysis and scanning electron microscopy, the influence of the Si content on the coating composition, phase constituents, deposition rate, surface morphology and microstructure was investigated systematically. In addition, the change rules of micro-hardness, internal stress, adhesion, friction coefficient and wear rate with increasing Si content were also obtained. In this work, the precipitation of silicon in the coating was found.With increasing Si content, the coating microstructure gradually evolved from continuous columnar to discontinuous columnar and quasi-equiaxed crystals; accordingly, the coating inner stress first declined sharply and then kept almost constant. Both the coating hardness and the friction coefficient have the same change tendency with the increase of the Si content, namely increasing at first and then decreasing. The Cr–Si–N coating presented the highest hardness and average friction coefficient for an Si content of about 9.7 at.%, but the wear resistance decreased slightly due to the high brittleness.The above phenomenon was attributed to a microstructural evolution of the Cr–Si–N coatings induced by the silicon addition.