Using experimental values, I will find a correlation between the angular velocity of the yarn around the axis and the tension. At the winding point (Up), the yarn begins to slide on the surface of the package. Variation of the tension T0 during unwinding of the yarn from a cylindrical package for different winding angles.
Comparison of the amplitude of the voltage oscillation as a function of the package radius c and the winding angle ϕ for constant unwinding velocity V = 1000 m/min. Comparison of the amplitude of the voltage oscillation as a function of the package radius c and the winding angle ϕ for constant unwinding velocity V = 2000 m/min. Comparison of the amplitude of the voltage oscillation as a function of the package radius c and the winding angle ϕ for constant unwinding velocity V = 1500 m/min.
Comparison of the amplitude of the voltage oscillation as a function of the unwinding velocity V and the package radius c. Comparison of the tension variation during the unwinding of the yarn from conventional cross-wound packages (dashed line) and from new generation packages with alternating layers (solid line). Comparison of the amplitude of the voltage oscillation in packages with alternating layers (lighter) and in conventional cross-wound packages (darker).
With this design, the voltage and the amplitude of the voltage fluctuations can be significantly reduced.
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Introduction
- Material used
Stab-resistant body armor is increasingly being used by law enforcement agencies and prisoners in European and Asian countries, where violent knife crimes are more common due to strict gun ownership restrictions [3]. Although the fatality rate from a knife or other cutting tool has been low, stab-resistant body armor has some practical and commercial experience in current police service [5]. Puncture-resistant body armor can be made of a variety of materials, from traditional solutions that are relatively heavy and offer little resistance to penetration, to modern body armor made of ceramic, polycarbonate or aramid fibers that provide excellent protection against punctures, but are bulky, inflexible and uncomfortable to wear [6].
To mitigate these restrictions, the manufacture of stab-resistant body armor must meet a set of internationally recognized testing standards. In addition, a number of studies have been conducted to reduce the weight of body armor and improve its flexibility. However, one of the alternative manufacturing technologies, additive manufacturing (AM), is increasingly being used in a range of new applications for tailor-made clothing and high-performance textiles [9].
However, this solution remains to be widely explored in an attempt to overcome body armor issues. There are a number of AM techniques available on the market, including stereolithography (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), and fused deposition modeling (FDM). In addition, Johnson [13] attempted to solve the problems that continue to exist with many current body armor protection solutions through AM.
In their study, LS was applied to develop stab-resistant test samples for body armor. Further samples were performed on the selected material with a wider thickness range, namely from 7.0 to 10.0 mm, increasing in 1.0 mm increments, mainly due to the previous thickness range failing to prevent the blade from penetrating the underside of the flat samples. Furthermore, five different design features of the body armor have been generated based on the combined knowledge of various design features found in the natural biological body armor, such as animals and plants.
In the end, one of the designs was chosen to provide the highest protection – with the knife pierced below the patterns, it was the lowest of all designs. All five models were designed mainly based on the inspiration of the hierarchical arrangement of elasmoid scales, which are considered to be able to offer high flexibility and provide multiple levels of protection against penetration [15, 16], as well as integrated with the design geometries of other scales, as summarized in Table 1. The thickness of the D2 scale was reduced from 8.0 to 4.0 mm in an attempt to reduce the total thickness of the armor and the whole assembly. y height of the following sets.
Such a design feature is inspired by combining the designs of both the placoid scales and the osteoderms, to eliminate the weakness between the overlapping shell element while enhancing the protective performance of all grades. Based on the examination of each mounting angle, the mounting angle that does not provide roof-tile mounting with a minimum thickness of 8.0mm or more will not be further considered in the development of the other designs.
Results and discussion
Not all samples were able to withstand knife puncture, as all recorded puncture depths were greater than the maximum allowable 7.0 mm. However, the total number of breakage cases for PC-ABS was much less than for ABS-M30, as only two of the 4.0 mm thick PC-ABS specimens (Figure 6) were fractured and showed unmeasurable knife penetration. The average knife penetration depth of the 6.0 mm thick ABS-M30 samples was significantly lower than that of the PC-ABS samples, by a difference of 5.67 mm, despite the fact that the average knife penetration depths of both the 6.0 mm thick ABS-M30 and PC-ABS samples were higher than the maximum allowable value of 7.0 mm.
In that case, the puncture resistance of the material was further determined by the force/displacement traces of the impact event, and kinetic energy absorbed by the target samples measured 6.0 mm. Impact damage in the FDM fabricated samples is caused by the loss of kinetic energy from the knife blade during penetration, so the energy absorption by the target samples can be analyzed using the formula, E ab = 1_. Knife penetration through the bottom surface of 7.0 mm thick PC-ABS samples was significantly higher than the maximum allowability of 7.0 mm.
In addition, samples with a measured thickness of 9.0 mm were only slightly punctured, resulting in an average knife penetration depth of 2.24 mm. However, in all 10.0 mm thick samples, no knife penetrated the lower surfaces. Based on the puncture test results of five models, most of the puncture tests showed a successful puncture resistance that met the requirement lower than 7.0 mm as defined by the HOSDB KR1-E1 24 Joule impact energy.
The average blade penetration depth resulted in D2 was 7.43mm, which was lower than D3, but D2 did not effectively resist the blade threat because the blade penetration depth that occurred in it exceeded 7.0mm. On the other hand, D1 provided an acceptable level of protection with an average blade penetration of 5.37mm, which was below 7.0mm. In addition, D4 showed a stab resistance relatively lower than D5, as the average knife penetration depth of the D4 samples was 0.87 mm higher than that resulting in the D5 samples.
Furthermore, the resistance between the knife blade and the specimens led to crack formation from the edges of the target scale. Despite one of the adjacent scales being detached from the assembly due to the impact of the knife blade, the design feature of the assembly was able to block the knife blade to resist further penetration into the material structure. In addition, the impact resistance of D5 will be slightly reduced if the knife blade is pierced at the front, which is far from the thickest area since the thickness along the front of the sample is measured to be 8.62 mm (Figure 1).
Conclusion
We are grateful to all those who directly or indirectly helped to complete this study and appreciate the financial support from Universiti Teknikal Malaysia Melaka. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ . by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Occupational health and safety issues of police officers in Canada, the United States and Europe: A review essay' [Online].
