Numerična analiza vpliva podtlaka na mehanski odziv človeškega stegna

Drame, Miha (author), Urevc, Janez (mentor), Halilovič, Miroslav (comentor)

Ena izmed težav pri izpostavljenosti mikrogravitacijskim pogojem je premik centra krvi proti zgornjemu delu telesa. Ta privede do vrste fizioloških sprememb, ki negativno vplivajo na telo, kot so povečan tlak v lobanji in motnje vida. Najobetavnejši protiukrep predstavlja uporabo negativnega tlaka v spodnjem delu telesa (ang. \emph{Lower Body Negative Pressure - LBNP}), ki razširi izpostavljena tkiva, kar povzroči premik centra krvi nazaj proti spodnjemu delu telesa. Za dosego pozitivnih učinkov bi morali biti astronatvni LBNP-ju izpostavljeni dlje časa, česar trenutne toge podporne rešitve, ki ločijo podtlak od okolice, ne omogočajo. V okviru študije smo raziskali vpliv podtlaka na odziv mehkega tkiva in izdelali numerični model spodnjega dela telesa v stegenskem področju, s katerim smo analizirali vpliv podtlaka. Za določitev materialnih lastnosti modela smo razvili metodo inverzne identifikacije, ki temelji na posnetkih prenosne ultrazvočne naprave. Odziv tkiva smo analizirali v povezavi z razvito valovito podporno strukturo, rezultate pa ovrednotili na osnovi spremembe volumna tkiva, ki ga določena geometrijska različica podporne strukture povzroči. Uporabo slednje smo ovrednotili na osnovi kontaktnih tlakov, ki predstavljajo mejo varne uporabe.

• Language: Slovenian
• Keywords: CAD model človeškega stegna, uporaba podtlaka, numerično modeliranje LBNP, valovita podporna struktura, ultrazvok, inverzna materialna identifikacija, metoda končnih elementov
• Work type: Master's thesis/paper
• Organization: FS - Faculty of Mechanical Engineering
• Year: 2024
• PID: 20.500.12556/RUL-164433
• Publication date in RUL: 25.10.2024

Secondary language

• Language: English
• Title: Numerical analysis of the influence of negative pressure on the mechanical response of human thigh

Abstract

One of the problems with exposure to microgravity is the shift of the blood centre towards the upper part of the body. This leads to a series of physiological changes that have a negative impact on the body, such as increased pressure in the skull and visual disturbances. The most promising countermeasure is the application of lower body negative pressure (LBNP), which expands the exposed tissues, causing the blood centre to shift back towards the lower body. To achieve positive effects, astronauts would need to be exposed to LBNP for a prolonged period of time, which is not possible with current rigid support solutions that separate the negative pressure from the surrounding environment. In this study, we investigate the effect of negative pressure on the soft tissue response and develop a numerical model of the lower body in the thigh region to analyse the effect of negative pressure. To determine the material properties of the model, we develop an inverse identification method based on recordings from a portable ultrasound device. The tissue response is analysed in relation to the developed wavy substructure, and the results are evaluated on the basis of the change in tissue volume induced by a given geometric variation of the support structure. The use of the latter is evaluated on the basis of contact pressures, which represent the limit of safe use.

• Keywords: human thigh CAD model, use of negative pressure, LBNP numerical modelling, wavy substructure, ultrasound, inverse material identification, finite element method