Sadayuki Ujihashi

Neck Injury Mechanisms During Direct Face Impact

Study Design. Digitized measurements of the intervertebral motions using cervical cineradiographs of 10 volunteers during direct impacts applied to their faces. Objectives. To clarify the cervical spine motion during direct face impact and postulate some mechanisms of neck injuries. Summary of Background Data. Neck injury occurs mostly in traffic or falling accidents. Hyperextension of the neck is considered the most common mechanism of the injury because most victims have lacerations or contusions on their faces. Methods. A low-level backward impact load was applied to 10 healthy male volunteers’ faces at the forehead and maxilla via a strap using a free-falling small mass. Cervical vertebral motion was recorded by radiograph cineradiography during the impact. Results. The upper cervical spine showed a flexion motion for both conditions. Consequently, the cervical spine had an S-shaped curvature similar to that in cervical retraction. Intervertebral motions of the cervical spine were evaluated using an radiograph frame taken at the maximum cervical retraction. For the forehead load, intervertebral motion at C1–C2 was flexion, and motions of the lower cervical spine were extension. For the maxilla load, intervertebral motions from occiput-C1 through C4–C5 were flexion. The inflection point of the curvature was influenced by the impact location. Conclusion. We detected a flexion motion of the upper or middle cervical spine during direct face impact. In an actual accident, if the cervical spine is forced into similar motion, we speculate that neck injury would occur in this retraction-like curvature of the cervical spine.

Cervical Vertebral Motions and Biomechanical Responses to Direct Loading of Human Head

There is little known data characterizing the biomechanical responses of the human head and neck under direct head loading conditions. However, the evaluation of the appropriateness of current crash test dummy head-neck systems is easily accomplished. Such an effort, using experimental means, generates and provides characterizations of human head-neck response to several direct head loading conditions. Low-level impact loads were applied to the head and face of volunteers and dummies. The resultant forces and moments at the occipital condyle were calculated. For the volunteers, activation of the neck musculature was determined using electromyography (EMG). In addition, cervical vertebral motions of the volunteers have been taken by means of X-ray cineradiography. The Ethics Committee of Tsukuba University approved the protocol of the experiments in advance. External force of about 210 N was applied to the head and face of five volunteers with an average age of 25 for the duration of 100 msec or so, via a strap at one of four locations in various directions: (1) an upward load applied to the chin, (2) a rearward load applied to the chin without facial mask, (3) a rearward load applied to the chin with the facial mask, and (4) a rearward load applied to the forehead. The same impact force as those for the human volunteers was also applied to HY-III, THOR, and BioRID. We found that cervical vertebral motions differ markedly according to the difference in impact loading condition. Some particular characteristics are also found, such as the flexion or extension of the upper cervical vertebrae (C0, C1, and C2) or middle cervical vertebrae (C3-C4), showing that the modes of cervical vertebral motions are markedly different among the different loading conditions. We also found that the biofidelity of dummies to neck response characteristics of the volunteers at the low-level impact loads is in the order of BioRID, THOR, and HY-III. It is relevant in this regard that the BioRID dummy was designed for a low-severity impact environment, whereas THOR and HY-III were optimized for higher-severity impacts.

An intelligent method to determine the mechanical properties of composites under impact loading

Abstract This paper describes an alternative estimating method for the current drop weight impact test used to determine the mechanical properties of fibre reinforced composites. The method proposed here measures the strain variations in time of the drop weight and uses the one-dimensional wave theory to convert the measurements into the load and displacement variations in time without any filtering technique. As a result, it is shown that the measurements with high accuracy can contribute to determine the real mechanical properties and to obtain further information on the composites under drop weight impact.

Finite element modelling and simulations for golf impact

The objective of this study was to construct a finite element model of a golf ball and an impact simulation model between the ball and a club, and to devise a method for the construction of simulation models by investigating the factors affecting the behaviour of the ball during and after impact. A ball model with hyperelasticity and viscoelasticity was constructed using solid elements, and the relationship between the material properties and the ball behaviour at impact was revealed by varying several material constants of the ball model. A finite element model of a club with elasticity was created from a computer-aided design surface model of a commercially available driver. The club head and shaft were modelled using solid and shell elements, respectively. The effects of initial conditions at impact on the rebound behaviour of the ball, that is, the velocity, angle and spin rate, were investigated from impact simulations by varying the impact points of the ball and the postures of the club. Then, methods for the construction of simulation models were proposed based on these relationships. Impact experiments were also conducted to obtain the ball behaviour. The results simulated using the models, constructed by the proposed methods, closely matched the experimental results.

Energy-absorption abilities of CFRP cylinders during impact crushing

Abstract This paper describes the energy-absorption abilities of thin-walled circular cylinders made from carbon-fibre-reinforced plastic (CFRP) during crushing under impact loading. The tests are carried out with an impact testing machine, the crosshead mass of which is 21.5 kg, at a velocity of 8 m s −1 under the temperature range 20 to 130°C. The ply angles of the specimens are 15 and 75°, their dimensions are 1.2 mm in thickness, 30 mm in inner diameter and 100 mm in length. Load-time and displacement-time profiles are acquired precisely by using a newly designed load cell and an optical displacement transducer. The acquired force and displacement profiles are converted to the force and deformation relationship, which manifests the energy-absorption abilities. The specimens produce two different types of crushing mode and definite constant load levels which keep their energy-absorption ability high. The energy-absorption abilities and the crushing modes of the specimens change at temperatures above 60°C.

Construction of a finite element model for collisions of a golf ball with a club during swing

The objective of this study was to construct a finite element model for simulating the mechanical behaviour of a golf club and ball from swing to impact. An experiment using a golf robot was conducted to obtain the motion of the shaft grip during the swing, and the behaviour of the club and ball during the swing and impact. The swing model was developed by inputting the positional coordinate data of the grip, which was obtained from an experiment, into the grip model. The simulation results generally matched the experimental results for the swing motion, the behaviour of the shaft during the swing and the clubhead velocity and orientation at impact. The modelling of the grip contributed to the accuracy of the simulation results by precisely representing swing motion and suppressing the generation of vibration in the shaft grip. This indicates that the components of the proposed modelling method may also be suitable for representing the swing using data obtained from the robot test, and that the model and the approach for modelling may have potential to be used as a predictable tool to supplement robot tests, reducing the dependency on prototypes.

Influence of the head shape variation on brain damage under impact

The influence of the head shape on intracranial responses under impact was investigated by using Finite Element Method. Head shape models of 52 young adult male Japanese were analyzed by Multi Dimensional Scaling (MDS), and a 2 dimensional distribution map of head shapes was obtained. Five finite element models of the Japanese head were constructed by a transformed finite element model of an average European adult male (H-Head model) using Free Form Deformation (FFD) technique. The constructed models represent the 5 th and 95 th percentile of the first 2 scales obtained by MDS. The same acceleration pulse was applied to the H-Head model and the five finite element models. The cause of the difference was considered to be differences in pressure distribution in the brain caused by the differences in the head shape. Variation in the head shape should be taken into account in simulating the effects of impact using a finite element model.

The moment lever arm is a predictor of the pronation in running

The over-pronation of foot in the running stance phase is a major factor of running injury. Therefore, running shoes need feature to prevent over–pronation in stance phase. Many earlier studies about foot pronation focused on kinematic parameters such as pronation angles (Nigg 1999). Going through biomechanical predictor is necessary in designing pronation control shoes. Basically pronation is occurred as the results of such forces acting at foot caused by the ground reaction force (GRF) etc. Therefore, in this study, the moment produced by GRF around the ankle joint center is calculated from experimental results and it is discussed how the factors of the moment can affect.

Analysis of Intervertebral Strain Response during Rear Impact Using Head-Neck Finite Element Model

Minor neck injuries in rear collision accidents have become a huge problem in many countries. Therefore, it is urgent to develop a suitable criterion for assessing neck injury risk. In this study, a detailed head-neck finite element (FE) model was developed. Skull and vertebrae models were created based on CT images of a typical Japanese male. Models of intervertebral discs, ligaments and muscles were also created according to literatures. Furthermore, material properties were taken from the published data. In order to evaluate intervertebral soft tissue strain due to translational rotational coupled motion of vertebrae, a 2D strain analysis method was also proposed. The method was applied to cervical vertebral motion data obtained from previous rear impact tests using human volunteers and from test reconstruction using the head-neck model. A potential correlation between intervertebral strain and neck injury was clarified from the comparison between the intervertebral strain level and existence of neck discomforts. The model’s response is also in good agreement with the volunteers’ response, indicating that the head-neck model is suitable for minor neck injury analysis and that it is possible to analyze the intervertebral strain with a head-neck model.

Self-Organization of Topological Structures by a Cellular Automaton

We proposed the cellular automaton model based on remodeling of living systems. The computational results showed that the model has an ability to generate various biomimetic topological structures. The initial distribution of Young’s modulus greatly affects the topological formation. The formation is uniquely determined once the mechanical conditions are given. However, it is difficult to predict the final topological structure. These features suggest to us that a distributed mechanical system has potentiality to generate various topological structures and the potentiality is related with diversity of life.