Research (4)
19
Mar
Amateur football pitches: Mechanical properties of the natural ground and of different artificial turf infills and their biomechanical implications.
In
Research
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Written by Zanetti Elisabetta
Artificial turf is being used more and more often. It is more available than natural turf for use, requires much less maintenance and new products are able to comply with sport performance and athletes' safety. The purpose of this researchis to compare the mechanical and biomechanical responses of two different artificial turf infills (styrene butadiene rubber, from granulated vehicle tires, and thermoplastic rubber granules) and to compare them to the performance of natural fields where amateurs play (beaten earth, substantially). Three mechanical parameters have been calculated from laboratory tests: energy storage, energy losses and surface traction coefficient; results have been correlated with peak accelerations recorded on an instrumented athlete, on the field. The natural ground proved to be stiffer (-15% penetration depth for a given load), and to have a lower dynamic traction coefficient (-48%); the different kinds of infill showed significantly different stiffnesses (varying by more than 23%) and damping behaviour (varying by more than 31%). In running, peak vertical accelerations were lowest in the artificial ground with thermoplastic rubber granules, while, in slalom, both artificial grounds produced higher horizontal peak accelerations compared to the natural ground. Results are discussed in terms of their implications for athletic performance and injury risk.
19
Mar
This work analyses blunt abdominal trauma produced by driver-handlebar collision, in low speed two-wheel accidents. A simplified dynamic model is introduced, whose parameters have been estimated on the basis of cadaver tests. This model allows calculating the peak impact force and the abdominal penetration depth; therefore the likelihood of occurrence of serious injuries can be estimated for different masses of contacting bodies and different speeds. Results have been checked against literature data and true-accident reports. Numerical simulations demonstrate that serious injuries (AIS>3) can occur even at low speeds (<20km/h), therefore the design of protective clothing is recommendable. The model can allow both the analysis of true accident data and the virtual testing of protective equipment in the conceptual design phase.
19
Mar
Recent advances in dental optics – Part II: Experimental tests for a new intraoral scanner
In
Research
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Written by Zanetti Elisabetta
A new device for 3D oral scanning has been designed and tested: it is a two channel PTOF (pulsed time-of-flight) laser scanner, designed for dental and industrial applications in the measurement range of zero to a few centimetres. The application on short distances (0–10 cm) has entailed the improvement of performance parameters such as single shot precision, average precision and walk error up to mm-level and to µm-level respectively.
The single-shot precision (σ-value) has resulted to range from 43 to 63 ps (9–10 mm), having considered the measurement range (6.5–10 mm) corresponding to 1–2 V signal; this result agrees well with estimates made from simulations. The average precision has resulted to be dependent on the number of measurements and can reach a value equal to ±25 µm, whenever the measurements frequency is sufficiently high. For example, if the required scanning speed is 1000 points/s and the required average precision is ±25 µm, then a pulses frequency of 30–50 MHz is needed, considering signal amplitude varying between 1–2 V.
On the whole, the performance of this new device, based on PTOF has proven to be adequate to its employment in the field of restorative dentistry.
19
Mar
by
Set up of a prescreening tool for vehicle front-end design, allowing numerically forecasting of the results of EC directive tests, with reference to pedestrian lower leg impact.
A numerical legform model has been developed and certified according to EC directive. The frontal end of the vehicle has been simulated through a lumped-parameters model, having considered the predesign stage when the target overall behavior is being established. The stiffness behaviors of the bumper and of the spoiler have been estimated by means of more detailed numerical models.
A parametric analysis has been performed to outline the effects of bumper and spoiler stiffness, bumper vertical height, and the longitudinal distance between the spoiler and the bumper.
An analytical model has been introduced to predict tibial acceleration, knee shear displacement, and knee lateral bending, given the bumper and spoiler characteristics as input
Set up of a prescreening tool for vehicle front-end design, allowing numerically forecasting of the results of EC directive tests, with reference to pedestrian lower leg impact.
A numerical legform model has been developed and certified according to EC directive. The frontal end of the vehicle has been simulated through a lumped-parameters model, having considered the predesign stage when the target overall behavior is being established. The stiffness behaviors of the bumper and of the spoiler have been estimated by means of more detailed numerical models.
A parametric analysis has been performed to outline the effects of bumper and spoiler stiffness, bumper vertical height, and the longitudinal distance between the spoiler and the bumper.
An analytical model has been introduced to predict tibial acceleration, knee shear displacement, and knee lateral bending, given the bumper and spoiler characteristics as input
