**4. Results and discussion**

The frontal impact on the head model predicted the same pressure on coup side as predicted in Nahum's Experiment [42]. This result validates the calibration runs as shown in Figure 16. The model duplicated the experimental response reasonably well, the only minor differences attributable to one or more of the following factors: the mesh fineness, reduced frame time steps, or by the material properties. An autopsy did not reveal any visible injury as a result of the Nahum experimental test and, therefore, based on this observation the brain tolerance thresholds were: compression: 234 kPa, tension: 186 kPa.

108 Injury and Skeletal Biomechanics

**3.2. Validation** 

were applied.

Figure 14.

simulation

**4. Results and discussion** 

*3.2.1. Simulation versus experiment* 

does not influence the kinematic head response [35].

As shown in the fig., boundary conditions were defined at the four points around the headneck junction to restrict all transactional movement. Short duration impacts (<6ms), the neck

Validation of the model with experimental data was carried out while keeping the properties and load applications same. In order to reproduce the impact conditions, ~8000kN load was applied to the frontal side of the head, same as in Nahum's experiment [42]. Figure 15 shows pulse duration was kept 2 ms to reduce the time step cycles. Also, to compare the results for skull fracture with the prior experimental data [34], 8kN-16kN loads

To simulate the lateral impact, except the impact side on the head, all the other parameters were kept same, load was applied on the lateral side (left side) of the head as shown in

**Figure 15.** Comparison of impact force- time curve between Nahum's experiment and current

The frontal impact on the head model predicted the same pressure on coup side as predicted in Nahum's Experiment [42]. This result validates the calibration runs as shown in Figure 16. The model duplicated the experimental response reasonably well, the only minor

Nahum Experiment [42, 2] This simulation

A 16kN load applied to the frontal side of the head while other parameters kept same. Analysis ran 1.1E-3 seconds due to large number of damaged volumes created after that instance. This was consistent with the Yoganandan [19] and Allsop [20] that fracture occurs because of applied force range of 8.8-17 kN. The intracranial pressure reached 200 kPa which was an indicator for brain contusion, oedema, and haematoma, but the pressure exceeded 200 kPa and reached 249 kPa, which was only slightly higher than the threshold limit of brain (234kPa), see Figure 17.

**Figure 16.** Frontal pressure- time curve results for comparison with Nahum's experimental results.

The history output of strain energy of the model also seemed to be at 2.2 J consistent with indications of skull fracture Figure 17. Also, from Newton's second law, the resultant acceleration of head can be calculated as a=16kN/4.5kg (sample of patients were of male adults in the age range of 30-50 and the mass of head was considered nearly ~ 4.5 kg).

A fall resulting in head acceleration of over 200 g and pulse duration of 3.5 ms or less would create conditions necessary for the production of bridging vein ASDH [4, 28]. Also, a= 355.5g is > 150g represents the HIC > 2000 which is non-survival head injury. Thus, these results depict that the model is valid for the further analysis in injury biomechanics.

#### 110 Injury and Skeletal Biomechanics

Comparison of Intracranial Pressure by Lateral and Frontal Impacts – Validation of Computational Model 111

Simulation result shows that the relative risk and severity of TBI in lateral impacts are higher than in the frontal impacts. Figure 18 shows the pressure-time history for coup and countercoup (at and opposite side of the impact, respectively) sides of the model. It shows quite similar pressure-time curve compared to frontal one. However, the lateral impact produces 6.67% more pressure at coup side as compared to frontal impact. The results of countercoup side support the prior analysis predicting only 14% higher tensile stress by

Statistical analysis carried out on 1115 occupants who were the victims of lateral and nonlateral automobile impacts [40-41], TBI occurred from lateral impacts were more severe than

The paper reviewed the head injury mechanisms and criteria. A computational framework was developed to biomechanical parameters to assess the injury, and validate the finite element models of the human head. The comparison of the stress/pressure incurred by lateral and frontal impacts in the coup and countercoup side of the head was presented. The model has been validated against the two sets of experimental results: one obtained in

Although the results obtained from the study involved a degree of inaccurateness (i.e., model had around 6500 distorted elements, 3 layers of skull was assigned as a one layer having the mechanical property (young's modulus, poison's ratio and density) as an average of those 3 layers), they do nonetheless confirm that through proper sets of MRI

It is concluded that the lateral impacts are more severe than the frontal impacts. Therefore, it is imperative that victims of lateral impacts are at more risk for TBI than the frontal impacts. This information may be useful in injury assessment and developing sensors to alleviate

*Department of Biomedical, Industrial and Human Factors Engineering, Wright State University,* 

[1] Marjoux, D., Baumgartner, D., Deck, C., and Willinger, R., Head injury prediction capability of the HIC, HIP, SIMon and ULP criteria –New injury criteria for the head.

frontal impact and the other using head tolerance/skull fracture data.

data, analytical modeling is applicable in injury biomechanics.

Accident Analysis and Prevention 40(3), 1135-1148, 2008.

lateral impacts to prevent traumatic brain injuries.

lateral as compared to frontal impacts.

those resulting from non-lateral impacts.

**5. Conclusion** 

**Author details** 

*Dayton, OH, USA* 

**6. References** 

Corresponding Author

 \*

Aalap Patel and Tarun Goswami\*

**Figure 17.** Frontal pressure- time curve and history output of whole strain model after applying 16kN

**Figure 18.** Comparison of pressure-time curves at coup and countercoup sides between lateral and frontal impact

Simulation result shows that the relative risk and severity of TBI in lateral impacts are higher than in the frontal impacts. Figure 18 shows the pressure-time history for coup and countercoup (at and opposite side of the impact, respectively) sides of the model. It shows quite similar pressure-time curve compared to frontal one. However, the lateral impact produces 6.67% more pressure at coup side as compared to frontal impact. The results of countercoup side support the prior analysis predicting only 14% higher tensile stress by lateral as compared to frontal impacts.

Statistical analysis carried out on 1115 occupants who were the victims of lateral and nonlateral automobile impacts [40-41], TBI occurred from lateral impacts were more severe than those resulting from non-lateral impacts.
