Heading occur frequently in soccer games and studies have shown that repetitive heading of the soccer ball could result in degeneration of brain cells and lead to mild traumatic brain injury. This study proposes a two degree-of-freedom linear mathematical model to study the impact of the soccer ball on the brain. The model consists of a mass-spring-damper system, in which the skull, the brain and the soccer ball are modelled as a mass and the neck modelled as a spring-damper system. The proposed model was compared with previous dynamic model for soccer ball-to-head impact. Moreover, it was also validated against drop ball experiment on an instrumented dummy skull and also compared with head acceleration data from previous studies. Comparison shows that our proposed model is capable of describing both the skull and brain accelerations qualitatively and quantitatively. This study shows that a simple linear mathematical model can be useful in giving a preliminary insight on the kinematics of human skull and brain during a ball-to-head impact. The model can be used to investigate the important parameters during soccer heading that affect the brain displacement and acceleration, thus providing better understanding of the mechanics behind it.
In this paper, an experimental study was carried out to evaluate the number of layer effect of abaca fiber composite as natural reinforced polymer (NFRP) material for shear-strengthened reinforced concrete (RC) beams. Two externally bonded shear-strengthened beams with a different number of NFRP layers and a sound beam as a control beam were prepared. The test was conducted by applying two axial loads on the beam. The results showed that the use of one-layer and two-layer of abaca fiber composite as NFRP material for the shear-strengthened beam increased 9.78% and 9.92% of maximum load compared to sound beam respectively. Abaca fiber composite NFRP material contributed 11% and 18.57% of the total maximum shear load for one-layer and two-layer laminates respectively. In addition, externally bonded shear-strengthened beams affected the crack pattern and deflection value. However, debonding failure of NFRP laminates occurred in two-layer of the NFRP shear strengthened beam. It caused the beam did not work optimally.
This research focusses on the effect of vegetable oils, i.e. crude palm oil (CPO) and coconut oil (CO), used as the cutting fluid on the wear of carbide cutting tool insert in a face milling process. The performances of the tool, in term of wear and the surface roughness of the workpiece, were investigated and compared to those resulting from a similar milling process but using conventional cutting fluid, which is a commercial soluble oil emulsion (SOE). The results show that at the spindle speed of 360 rpm and the feed rate of 80 mm/min, the tool wear was smaller in the case of CO than that in the case of CPO cutting fluid, which is 0.16 mm2 compared to 0.40 mm2, respectively. The tool worn area in these cases are still larger than that in the case of SOE, which is 0.09 mm2. However, at higher spindle speed of 490 rpm and feed rate of 80 mm/min, the smallest tool worn area occurred for the case of CO cutting fluid, which is 0.04 mm2, compared to 0.1 mm2 and 0.11 mm2 for the case of CPO and SOE cutting fluids, respectively. As for the workpiece, the achieved surface roughness, Ra, were relatively similar for all the evaluated cases.
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