Combat Helmet Design Incorporating Multiple Ballistic Threats, Brain Functional Areas and Injury Considerations

Combat helmet protection zone parametric design is presented for small arms and explosive device ballistic threat notional spatial distributions. The analysis is conducted using a computer aided design software application developed to evaluate ballistic threats, helmet design parameters, and a standard set of common brain injuries associated with head impacts. The analysis helps to define the helmet trade space, facilitates prototyping, and supports helmet design optimization. Direct head impacts and helmet impacts, with and without helmet back face contact to the head, are tabulated. Head strikes are assumed to produce critical or fatal penetrating injuries. Helmet back face deflections and impact generated projectile-helmet-head motions are determined. Helmet impact obliquity is accounted for by attenuating back face deflection. Head injury estimates for ten common focal and diffuse head injuries are determined from the back face deflections and the head injury criteria. These, in turn, are related to the abbreviated injury score and associated radiographic dimensional diagnostic criteria and loss of consciousness diagnostic criteria from the trauma literature.

Characterization of Tissue Thermal Conductivity During a Tissue Joining Process

Electrosurgical vessel sealing, a tissue joining process, has been widely used in surgical procedures, such as prostatectomies for bleeding control. The heat generated during the process may cause thermal damages to the surrounding tissues which can lead to detrimental postoperative problems. Having better understanding about the thermal spread helps to minimize these undesired thermal damages. The purpose of this study is to investigate the changes of tissue thermal conductivity during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Instead of self-heating the tissue by the thermistor, we apply an external cold boundary on the other side of the tissue sample to stimulate a higher temperature gradient without denaturing the tissue in comparison to the heated method. The inverse heat transfer technique was then applied to determine the tissue thermal conductivity. Tissue thermal conductivity at different levels (0%, 25%, 50%, 75%, and 100%) of the joining process was measured. The results show a decreasing trend in tissue thermal conductivity with increasing joining level. When the tissue is fully joined, an average of 60% reduction in tissue thermal conductivity was found.

Stability and Collapsing Mechanism of Cavitation-Induced Nanobubbles in Simulated Extra-Cellular Matrix (ECM) Near Neuron

In blast-induced traumatic brain injury, shock waves (SW) play an important role along with cavitation phenomena. Due to the lack of reliable and reproducible experimental investigations, we have a limited understanding of the role of cavitation in brain damage. The present study aims to develop an atomistic simulation model to determine the role of shock-induced impulse and different constituents of the brain’s extra-cellular matrix (ECM) on the formation mechanism, stability and collapsing mechanism of nanobubbles in the ECM. The ECM in the brain can be divided into three major types depending on their location behind the blood-brain barrier, namely (a) the basement membrane (basal lamina), (b) the perineuronal nets and (3) the neural interstitial matrix. In this paper, we have studied the interaction of nanobubbles with bio-molecules of the perineuronal nets. We have chosen this zone of the ECM because we are interested to obtain the role of cavitation bubble collapse in neuron damage. Most biomolecules of perineuronal nets are slender in shape and flexible which is believed to induce special solid-fluid interaction between the fluid domain and the solid domain within the ECM. In addition, perineuronal nets contain a significant number of sodium ions. The relationship between sodium ion and solid-like constituents of perineuronal nets on the stability and the collapsing mechanism of nanobubbles will be discussed.

Behavior Evaluation of Deformation, Damage and Fracture of Biological Soft Tissue by Using Indentation Test

In this study, two types of indentation tests were used for the observation of deformation behavior of biological soft tissue, because indentation testing is an easy method to manage observation and control of the condition of complex tissue specimens. First, a fundamental indentation test was used to evaluate quasi-static deformation behavior of soft tissue. In the evaluation of the quasi-static behavior, elasticity, damage, and fracture of the tissue were analyzed from the profile of reaction force during the indentation. Ball-impact testing with subsonic indentation velocity was used for the evaluation of dynamic behaviors of soft tissue. In the impact test, the viscoelastic characteristics of specimens were evaluated by analyzing stress response, using extended Hertzian contact theory and wave equations, at the moment when a simple ball bullet shot from an airsoft gun strikes the specimen. In the experimental results of the test, an obvious relationship between quasi-static and impact responses of the specimen were observed subjectively. The results are evaluated to analyze the damage and the fracture of the soft tissue for the objective formulation of tissue mechanics. The plateau behavior of reaction force in relation to stress response was also reviewed, in order to quantify the beginning of tissue fracture.

A Sensitivity Study of the Porcine Head Subjected to Bump Impact

Understanding load transfer to the human brain is a complex problem that has been a key subject of recent investigations [4–6]. Because the porcine is a gyrencephalic species, having greater structural and functional similarities to the human brain than other lower species outlined in the literature, it is commonly chosen as a surrogate for human brain studies [7]. Consequently, we have chosen to use a porcine model in this work. To understand stress wave transfer to and through the brain, it is important to fully characterize the nature of the impact (i.e. source, location, and speed) as well as the response of the constituent tissues under such impact. We suspect the material and topology of these tissues play an important role in their response. In this paper, we report on a numerical study assessing the sensitivity of model parameters for a 6-month old Gottingen mini-pig model, under bump loading. In this study, 2D models are used for computational simplicity. While a 3D model is more realistic in nature, a 2D representation is still valuable in that it can provide trends on parameter sensitivity that can help steer the development of the 3D model. In this work, we investigate the variation of skull and skin thickness, evaluate material variability of the skull, and consider the effects of nasal cavities on load transfer. Eighty simulations are computed in LS-DYNA and analyzed in MATLAB. The results of this study will provide useful knowledge on the necessary components and parameters of the porcine model and therefore provide more confidence in the analysis. This is an essential first step as we look toward bridging the gap between correlates of injury in animal and human models.

Numerical Analysis of Texture Tactics on Skin by Using of the Model of Periodic Micro Unit

Various mechanical effects occur in the human skin when it touches the texture which has micrometric scale. Since these mechanical effects in the skin are complicated, their study is necessary. The purpose of this study is to ascertain these mechanical effects by applying numerical analyses for a detailed discussion. In particular, the analysis confirms the differential effects in the skin due to a periodic variation of the texture. By the modeling situation that the texture touches the skin, a stress in the position of skin sensory organs is examined. As a result of the analysis, von Mises stresses at a shallow position of skin showed characteristic effects in the case of a large texture period. It is inferred that these effects occur with a texture period greater than a certain boundary value. Stress values at deep positions of skin are substantially equal without depending on the pressure position of the skin surface. In other words, skin sensory organs of the deep position have a wide receptive field in the numerical analysis of this paper, and this result matches with results of previous researches.

Hierarchical Engineering Model of the Human Body

Engineers and scientists are able to understand and analyze the behavior of complex engineering systems in a wide range of critical technologies through hierarchical modeling followed by simulation of the model operation. This process results in a high fidelity integrated model as each level in the hierarchy is modeled in sufficient detail. The overall objective of this effort is to develop a sophisticated hierarchical model of the human body, followed by simulation of the model operation. In this initial research phase, the feasibility of the concept is explored and a framework for the model is described. A six-level model consisting of the whole body as a system, system of systems, organs, tissues, cells, and molecules is proposed and described. This paper explains that the human body is amenable to such hierarchical modeling and describes the benefits that can be achieved. The systems in the body deal with numerous processes: electrical, chemical, biochemical, energy conversion, transportation, pumping, sensing, communications, and so on. Control volume models for the organs in the body capture the mass and energy balance and chemical reactions. Tissue can be represented similar to structural components made of various biomaterials. Cells can be represented as a manufacturing and maintenance workforce assisted by molecular reactions. Following the representation of a healthy body, simulation runs by inserting faults and/or deficiencies in the operational parameters into the model could reveal the causes for specific diseases and illnesses. Such modeling and simulation will benefit medical, pharmaceutical, nutritional specialists, and engineers in designing, developing, and delivering products and services to enable humans to lead healthy lives.

Temporal Variation Characteristics of Analysis Accuracy in Two-Dimensional Ultrasonic-Measurement-Integrated Blood Flow Analysis

A two-dimensional ultrasonic-measurement-integrated (2D-UMI) blood flow analysis system was developed for easy acquisition of an intravascular hemodynamics, which feeds back Doppler velocity obtained by an ultrasonic measurement to a numerical blood flow simulation for clinical application. In previous study, ultrasonic measurement and 2D-UMI simulation were performed to clarify the analysis accuracy for real flow field. Additionally, spatial variation characteristics of analysis accuracy was clarified by comparison of velocity vectors between 2D-UMI and 3D-CFD analysis results corresponding to an experimental flow. However, temporal variation of analysis accuracy of 2D-UMI analysis result has not been examined in spite of essential information for reduction of experimental measurement error due to speckle noise. The aim of this study was to clarify temporal variation characteristics of analysis accuracy of each velocity component obtained in 2D-UMI blood flow analysis. Comparisons of Doppler velocity V and (u, v) velocity profiles between measurement data, 2D-UMI, and 3D-CFD analysis results were performed, and their time variations were discussed. As a result, it was clarified that temporal variation of Doppler velocity error for measurement data became larger with increasing feedback gain. Temporal variations of u and v velocity component errors for 3D-CFD analysis result showed the same tendency as that of Doppler velocity in feedback gain.

Is the Maturation of Arteriovenous Fistulas a Mechanical or Biological Problem?

During the maturation the high pressure blood from the artery inflows directly to the vein, extends its diameter, and finally the blood flow rate in the vein is even 500-times greater than normal one. The changes of the wall shear stress (WSS) in the vein are thought to play a key role in the remodelling of its wall. However, this process is still not well understood. The aim of this paper is to show an innovative approach for modelling of the vein deformation during the maturation process of a-v fistulas. Dilation of the vein was modelled as two-step complex biomechanical process. The obtained results concerning final diameter of the vein are compared with average diameter obtained for large group of patients. Moreover, this study shows the changes in the flow rate and the WSS that occur after maturation in the patient-specific fistula.