Predictions of the head of the head injury for road users in need of protection on the basis of Chinese male head data for adults

Head of FE model in China

Currently, the most frequently used human Fe models in China, such as the Thums and Global Human Body Model Consortium (GHBMC) models, were developed based on human data in the USA. The dynamic reaction features of human finite elements models under collision loads are also determined on the basis of the American corpse test data. However, there are big differences between the Chinese and the American human body in terms of external physical signs (e.g. size, weight, muscle density, mass distribution) and internal properties (dynamic reaction, biomechanics). For example, the corresponding male dummies in China must be 3.48% shorter and 11.89% lighter compared to medium -sized men in the USA. The Upper Army Chinese medium -sized men are 4.14% shorter than that of medium -sized men in the United States, and the knee height is 12% shorter in the seating position^23.24. The difference in the biomechanical properties is also highly significant and directly influences the human tolerance limit as well as the evaluation index and the limit of the test. Therefore, some Chinese researchers have proposed various methods for the development of Fe models that correspond more to the characteristics of the Chinese human body. In this study, we focus on methods for the construction of Chinese human head models.

The Scaling methodThis means that the scaling of the existing mature Fe dummy models, as shown in Fig. 1, is one of the main methods for the development of FE models. This approach not only reduces the development cycle and the costs of the Dummy model, but also ensures the biodetry realism of the dummy. When dealing with the scaling factor of adults, it is often assumed that the density and stiffness of biological tissues and materials of adults are the same; The geometric scaling factor is therefore an important parameter when you get the Chinese dummy model using the scaling method.

Two scaling methods are usually used for the Dummy head model. The first is the uniform scaling method; That means λ_XPresent λ_yPresent λ_Z are the same in the local coordinate system of the dummy head, as shown in 1b. The specific coefficient of headscalization is given as follows:

Where C Is the scope of the head W is the width of the head (y direction); L is the head length (x direction); λ_M is the scaling factor for the mass of the head; Index 1 shows Chinese human body parameters; And Index 0 shows American human body parameters.

The second scaling method is the uneven scaling method, as shown in Fig. 1c, for which the scaling coefficients are given by:

The width of the human head in China is basically the same as in the USA, while the difference between Chinese and American head lengths is great. If the scaling method of the uniform coefficient is applied, the contour line of the dummy head model obtained differs significantly from the geometric parameters of the Chinese human body in the Sagittal Plain and the coronal level. Therefore, it is believed that the uneven scaling method should be used to obtain the Chinese dummy head model.

In addition to the geometric size, there are also differences between Chinese and western population. Compared to the western population, the Chinese population in the temporal lobe and in the Cingulat gyrus as well as smaller features in the frontal lobe and in the parietal lobe set larger structural features. Since most Business -Fe models only provide the synthetic acceleration of the mass center for synthesis, the investigations of the injury level of the Chinese population based only on these FE models are not over.

Therefore, there is still a need for the generation of human head models with high biofidelity to comprehensively understand injury mechanisms. In this study we created a Fe Human Head model based on the basis of computer tomography (CT) and the magnetic resonance imaging (MRI) of Chinese adult men. This model can give an insight into the extent of the violation of different brain problems.

Construction of the FE head model

We developed a FE head model of a male male male Chinese Chinese Male Chinese volunteers and weight of 169.25 cm or 64.5 kg. Figure 2a, B shows the head data from the CT or MRI scans.

We have imported the CT and MRI data into the MIMICs (software and the contrast values ​​(ie gray value threshold values, as shown in Table 1). Then geometric models were generated the skull, the scalp and the brain tissue, as shown in 2C -E.

The Ansa software (www.beta-cae.com) was used to transform the head geometry model to generate the FE head model. Table 2 shows the material properties and the constitutive model of the FE head model. It is believed that the material properties of the brain tissue (i.e. the brain, the brain stem and the cerebellum) and the cerebrospinal fluid (CSF) are linear, isotropic and viscoelastic. The shear characteristic characteristic of viscoelastic behavior is expressed as follows:

Where \ (G_0 \) And \ (G_ \ Inty \) designate the short -term and long -term shear module, each β Is a decay constant and T is the time.

As a result, the FE head model is shown in Fig. 2F. It included the skull (cortical bones and spongus bones), lateral ventricles, brain stem, scalp, pia mater, brain, cerebellar, tentorium, third ventricle and CSF, as shown in Table 3. The total mass of the FE head model is approximately 4.95 kg.

Checking the FE head model via the Nahum experiment

That of Nahum et al.²⁵ (Experiment 37) was often used to validate the biofidelity of the FE head model. In this study we also compared the simulation results of the FE head model with the experimental curves of the Nahum experiment 37. In order to coordinate with nearby experiment 37, a rigid cylinder efficiency with a mass of 5.59 kg was used in the simulation test to influence the frontal bone of the head after 9.49 m/s, as in Fig. 3a shown. The horizontal level was geared towards the Frankfort level at 45 degrees. The simulation time was set to 8 ms and the head was restricted to prevent rotation acceleration.

3b shows the contact power comparison between the results of the simulation and the experiment. We observed that the experimental Peak 6953 N and the simulated peak value 6941 N fraud. The difference in the top value appearance (PVTO) was – 0.6 ms and the top percentage (PPD) was 0.17%. Therefore, the simulation and experiment's contact force curves agree.

Figure 3c -F shows the extracted experimental and simulation curves for the impact side printing, the offset side printing, the parietal bone printing or the occipital bone printing.

Figure 4a shows the PPD and the difference in PVTO between the curves of the simulation test and the Nahum experiment. We observed that the difference in PVTOS was less than 0.6 ms. The PVTO of the experimental and simulated curves was similar. On the other hand, the PPDs of the impact side printing and parietal bone printing match those of the Nahum experiment. Although the PPD values ​​of the offset side printing and the rear head pressure are slightly higher than the experimental values, the error range does not exceed 20%, which is acceptable²⁶. Therefore, the results of the simulation test and the consistents given in the nearby experiment are. Based on the analysis above, we determine that the FE head model is reliable and can be used in subsequent studies.

Validation Experimental data from Yoganandan's experiment

Yoganandan's experiment is used to examine the dynamic biomechanical reaction and violation of a person under the condition of the head-to-floor collision²⁷. We conducted a simulation test according to yoganandan's experimental description, as shown in Fig. 5. In the simulation, the head finite element model was placed on the side, and the buffer gasket was fixed horizontally, so that that the head model fur at speed of 3.5, 4.9 and s collided Buffer Gasket, and the Corresponding Contact Force Curves Were Obained, which Were Compared to The Yoganandan's Experimental Curves and analyzes. The simulation time was set to 10 ms.

The contact power between the side area of ​​the head and the plate was measured. Figure 6 shows the experimental and simulated results of the contact power of the head model when it falls at different speeds.

Figure 6 shows that the simulation results match the experimental curve for both the top value and for the trend of the curve. If the head -finish element model falls at different speeds, the top contact increases at increasing speed, and the PVTOs at speeds of 3.5, 4.9 and 6 m/s are 0.1, 0.2 and 0.3 ms. The PPDs at speed of 3.5, 4.9 and 6 m/s are – 7.86%, – 0.13%or. – 6.9%. The contact power peak and PVTO are close and all PPDs are within 10%, which checks the effectiveness of the model.