Helmet Impact Analysis: Material Damage, Head Injury Risk, and Performance, Essays (university) of Mechanical Engineering

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Development of Impact Analysis of Helmets for Sport Activities

MECG-7780-T

IMPACT MECHANICS

submitted by

James T. Adu 7836380 Course Instructor: Dr. Igor Telichev

March, 2018.

ABSTRACT

The use of helmets has greatly reduced penetrating injuries, trauma and concussions caused by collision impacts during sport activities. This has greatly saved the lives of many athletes. The aim of this study is to present a review of work done by authors in the area of impact on helmets so as to quantify the level of risk to the head and brain, material damage and the effect of different parameters during the impact. Generally speaking, the two major ways by which this has been done by quite a number of researchers were the experimental procedures and numerical analysis and simulations. The results were based on strains, acceleration caused and compression as well as GSI number threshold which should not be exceeded. The findings are the use of helmets should be limited to maximum of three years. Then, five different locations were spotted on the helmet. The most and least protective are side and front locations. Considering a situation where the orientation of the impact is categorized based on centre of gravity (C.G.), any impact below C.G and at C.G. will result into compression of the helmet. But, the impact at centre of gravity will result into no compression and there is prevention of head injury. Also, it was confirmed that vintage leather helmets are better in use than the modern day 21st^ century helmets. With the increase in impact velocity, there is greater risk of head injury. Moreso, vinyl nitrile liner offers better protection performance than polypropylene in usage. Lastly, the pattern of layer of 2P5 with two pattern and five piles protects the head against injury than any other layer arrangement. Hence, the stiffness of the helmet and interior cushioning system plays a vital role in overall safety of the athletes.

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 Effect of the Age, Level of Usage and Locations of the Helmet Shell 4.2 Effect of Different Locations on the Helmet Protection Performance. 4.3 Effect of Position of Center of Gravity and Model of the Helmet Shell. 4.4. Effect of Helmet Design for Optimum Protection 4.4.1 Effect of Impact on Configuration, Velocity and Material of the Helmet. 4.4.2 Effect of Number of Layers and Liner Patterns of the Helmet Shell. 4.5 Results of Modelling on the Helmet Shell Protection. CHAPTER FIVE CONCLUSION REFERENCES

LIST OF FIGURES

Figure 1: A model of Helmet. Figure 2: Types of impulse curve Figure 3: Varieties of helmets design Figure 4: NOCSAE test rig for impact test on helmets Figure 5: Front View of Helmet Geometry Figure 6: Side View of Helmet Geometry Figure 7: Outer shell of Baseball Geometry Figure 8: Meshed Baseball Helmet Figure 9: Meshed Baseball Assembly Figure 10: Pinned in Place Baseball Helmet Figure 11: Side of Helmet and Ball Interaction Figure 12: Mesh and Assembly of Job Prior to Simulation Figure 13: Colored Contour Model After Impact Simulation Figure 14: The GSI scores for different velocities and locations Figure 15: The linear accelerations for different velocities and locations Figure 16: The linear acceleration observed over time at velocity impact of 5m/s Figure 17: The model of the head Figure 18: Simulation of results of maximum principal strain for the VN liner (black) and EPP liner (grey) across impacts on ice and boards. Figure 19: Simulation results of CSDM measures for ice impacts for VN and EPP helmet liner Designs Figure 20: Average deceleration shell performance

Table 1: The hardening exponent for each element at different locations on the helmets. Table 2: The GSI scores for models of helmets for football and lacrosse at different locations. Table 3: Peak linear accelerations across the locations Table 4: Energy dissipation characteristics across the locations Table 5: Anova to attest to the result findings Table 6: Impact orientation for the helmet Table 7: Experimental impact kinetic results for two different helmet liners and impact liners anvil Table 8: Lay-up and weight details Table 9: Measure Gaussian and Mean Curvature for the four impact sites of the shell Table 10: Values of the overall deceleration normalized to 2P Table 11: Lay-up and weight details