Survey of laceration injuries experienced by US adolescent and young adult alpine skier racers during the 2018–2019 ski season

Recently during ski racing competitions, a few high-profile accidents resulted in severe life-threatening laceration injuries. Ski-laceration injuries are caused by metal ski edges cutting through skin/muscles/arteries during falls and range in severity. There is a desire by the racing community to better protect skiers. However, current laceration injury research does not provide detailed information about laceration injuries or focus on adolescent and young adult ski racers. Therefore, the Self-Report Slash Injury Survey (Slash Survey) was conducted to (a) measure the frequency, severity, and body location of laceration injuries during skiing and (b) identify the skiing environment and ski maintenance level during laceration injuries. The Slash Survey was an online survey that asked participants ages 10–24, who are enrolled in US ski race programs, to report whether they experienced a laceration injury and what ski maintenance was used during the 2018–2019 ski season. The Slash Survey results suggest that the laceration injury rate during the 2018–2019 ski season was 6.8% and almost half the lacerations reported were considered slight (i.e. <1 day of absence from the sport). For respondents of the survey, no correlation was found between laceration injuries and (a) slope surface conditions, (b) outside temperature, (c) weather, (d) skiing activity, and (e) ski maintenance (tuning). From the survey, the most common ski tuning method was using a file guide by hand (29%), automated ski tune at a ski shop (20%), stone grind (17%), and cup wheel grinder (17%). Furthermore, open-ended responses suggest that a ski community narrative may be amplifying the awareness of laceration injuries. The aim of this survey was to establish detailed information about ski laceration injuries among adolescent and young adult US ski racers for the development of mitigation strategies.

Grinding of Cermets with Cup-Wheels

Cup-wheels are frequently used to grind cermets, a difficult-to-grind material. An investigation was made into the transient geometry of the cup-wheel rim, grit dulling, wheel loading, and wheel self-sharpening with chip thickness. Tests were performed on a saw-tip grinding machine and specific energies, G-ratios and rim geometries were measured. Results showed that, like grinding of tungsten-carbide, loading is prevalent. However, unlike grinding of tungsten-carbide, grit dulling is also prevalent and wheel conditioning is of limited use. Much better results, particularly with respect to surface finish, can be obtained if the wheel is trued to a predetermined geometry. In addition, grinding parameters must be chosen to induce wheel self-sharpening. Practical recommendations are given.

Dressing scheme and process parameters analysis for bonnet tool in bonnet polishing

Bonnet polishing is widely used in final processing of optical elements, as the bonnet tool has the characteristic of fine surface adaptability and controllable pressure. For the purpose of ensuring the stability and exact controllability of polishing process, it is necessary to make precise dressing of bonnet tool. In this paper, first a dressing scheme using cup diamond wheel is proposed for bonnet tool, and then the feasibility of the dressing scheme is verified by analyzing the trajectory and the envelope of the diamond particles on the cup wheel. After that, the influences of the dressing process parameters on the dressing efficiency and trajectory distribution are defined through theoretical analysis and MATLAB simulation, and by simulation the dressing process parameters are determined. In addition, a trimmed program with variable speed ratio is proposed to homogenize the dressing tracks. Finally, an experiment was conducted to test the simulation result. This paper provides the theoretical basis for actual dressing process of the bonnet tool.

Mathematical Modelling the Process of Cup Wheel Precision Grinding of Rotating Concave Paraboloid

A novel principle of cup wheel grinding of rotating concave quadric surface was proposed. The mathematical model of machining process was established to prove the feasibility of precision grinding of rotating concave paraboloid based on the introduced principle. The conditions of non-interference grinding of concave paraboloid were mathematically derived. The processing range and its influence factors were discussed. The trajectory equation of abrasive particle was concluded. Finally, the math expressions of numerical controlled parameters was put forward in the process of grinding of the concave paraboloid.