The paper investigates an experimental analysis of crack extension in steel DIN 42CrMo4V. This improved material has a high strength and toughness. It is used for statically and dynamically stressed ...components, in particular for larger cross-sections under high stress. The aim of the paper is to find possibility for more accurate and precise experimental determination of crack characteristics in three-dimensional problems of fracture mechanics. Notched test specimens with an initiated defect as a crack were made to determine impact properties and parameters of fracture mechanics. These investigations allow establishing the dependence of geometry of the movable crack and conditions of stress for its further extension. Therefore, it is possible to determine the characteristic quantity describing material behaviour, both in linearly elastic and in elasto-plastic fracture mechanics.
Diabetes is a group of metabolic diseases causing a system disorder, i.e.; it cannot be explained or understood by phenomena
on single material scale. The diabetic foot is studied as flexible ...multibody structure by nonlinear finite element
method. The physical and geometrical multiscale heterogeneity is solved by multilevel finite element approach. The diabetic
tissue is described by internal coordinate’s formalism, as complex multiscale process in tissue. The accompanying
problem of the axisymetric wound healing is solved numerically. Some results related to foot deformity, stress and strain
concentration and wound healing are presented.
The subjective investigation, that is focused on the sensations of a person, is a good tool for the evaluation of an environment
that group of people consider comfortable. In the experiment reported ...here, participants were dressed into 1-
-layer and 2-layer clothing systems. They performed physical activity and rated the subjective perception of comfort, as
well as the thermal and moisture sensation. The aim of this investigation is to compare the subjective human perception
during the physical activity wearing different clothing systems to the objective results of sweat absorption.
Poznato je da je ultraljubičasto zračenje opasno za ljudske oči, kožu i imunološki sustav. Na tržištu postoji mnogo proizvoda za zaštitu od ultraljubičastog zračenja, poput naočala za zaštitu očiju i ...odjeća ili kreme za zaštitu kože. Faktor za zaštitu od vanjskog ultraljubičastog zračenja je ultraljubičasti indeks. Međutim, postoji i izlaganje unutarnjem zračenju zbog umjetne svjetlosti koje također može biti opasno. U ovome radu dane su pronađene ultraljubičaste komponente u uobičajenim izvorima umjetne svjetlosti. Također se predlažu neke mjere za zaštitu od ultraljubičastog zračenja, poglavito u radnim prostorijama.
U svrhu određivanja toplinskog opterećenja čovjeka provedena su fiziološka mjerenja devet ispitanika, tvrtke za osiguranje osobne sigurnosti, odjevenih u dvije radne odore, prilikom obavljanja ...fizičke aktivnosti prema protokolu. Na temelju izmjerenih podataka u fazi pripreme (tjelesna masa, visina, sistolički tlak, dijastolički tlak i otkucaji srca), te tijekom same fizičke aktivnosti (promjene tjelesne temperature na različitim mjestima tijela) ukazano je na razliku u toplinskom opterećenju zbog temperaturnih razlika i tjelesnoj masi ispitanika. Toplinsko opterećenje je poveznica između praćene temperature na tijelu ispitanika, njegovog ponašanja tijekom aktivnosti te odore koju nosi.
This paper presents the analysis of stresses and deformations occurring when surfaces of two elastic bodies come into contact. Finite element method has been used as a numeric technique in order to ...obtain contact stresses between two elastic bodies. The mapped meshing method has been used for model meshing. When two bodies come into contact they touch initially in one point or along the line. Under the influence of loading they get deformed in the vicinity of the point of the first contact so that they touch along the surface whose size is small in relation to the body dimension. The contact problems are usually nonlinear and require computers of higher capacity. In a contact between two elements it is difficult to determine the contact area. This depends on loading, material, boundary conditions etc. Both combinations, i.e. when friction is taken into account and when it is not taken into account on contact surface have been observed. Normal and gliding stresses on the contact surface which have been caused by contact have been presented by reaction forces on nodes on contact surfaces. According to sizes of reaction forces
and friction coefficient, conditions on nodes of contact surfaces have been classified as gliding or sticking. Contact stresses have been calculated in the paper for cases when cylinders and rectangular plates for materials with different elasticity moduli come into contact. A symmetrical contact model has been used in the numeric analysis.
Background and Purpose: In combination with metabolic heat, the
heat generated by human activities and worn garment produce 6 basic factors (sometimes called 6 basic parameters because they are in ...space and time, but fixed representative values are frequently used in analyses) which define thermal body environments. The aim of this paper is to investigate the impact of one parameter – clothing insulation on the total transfer of heat and water vapor.
Materials and Methods: The measurement was carried out on knitted
fabrics commercially used for the production of underwear or different
types of next-to-skin-wear. The transfer of heat and moisture trough fabrics was observed in two simulated climatic environments (moderate and hot) with the constant parameters metabolic energy and air velocity.
Results: The results indicated that the heat resistance increases by laying a knitted fabric layer or under real conditions when the body is dressed in lightweight knitwear by 25%. The test results of the samples under different environment conditions indicated a reduction in heat resistance under moderate conditions. It also applies to the measurement results of the resistance to water vapor transfer, but the differences within the observed relationships are higher than it was in the case of heat transfer resistance.
Conclusions: The study showed that both heat and moisture transfers are freely movable controlling elements of comfort perception. Therefore, the optimal design of clothing systems is important factor of comfort.
Background and Purpose: This study is related to the design of advanced dermal scaffolds (non-woven fibrous mats) to provide multifunctional properties.
Materials and Methods: The nanofibre fabric ...from poly (ε-caprolactone) (PCL) solutions in acetone were produced by electrospinning. Based on SEM and its stochastic fibre characterization, equivalent fabric was generated by computer. Fibres network was created by random deposition of elastic straight segments within a representative volume element
(RVE).Elastic and permeability properties determined experimentally and numerically.
Results: The fibres diameter produced fibrous structure depends on solution concentration and electric field, what have been identified by surface response methodology. Effective Young’s modules for fibrous network measured and predicted by numerical model depend on fibres density and fibres diameter. Calculated data for permeability and pore distributionwere compared with models for fibrous media with acceptable error level.
Conclusions: Effective elastic and permeability properties are determined by separate computational models. The scaffold multiscale behaviour is commented with multiphysic design procedure.
Rad prikazuje široke mogućnosti primjene infracrvene termografije u različitim područjima ljudske djelatnosti. U eksperimentalnom dijelu rada izvršeno je ispitivanje udobnosti nošenja odjevnog ...predmeta u kojem su ocjenjivači davali ocjene vezane uz vlažnost, toplinu i ukupnu udobnost prije umjerenog rada i nakon njega. Eksperiment je proveden pri ovim temperaturama: 23±1ºC, 26±1ºC, 29±1ºC i 32±1ºC i konstantnoj relativnoj vlažnosti zraka 67± 3%. Za određivanje zona pojačanog znojenja tijela upotrijebljene su fotografije ispitanika snimljene nakon izvršenog rada. Uočene zone uspoređene su s termografskim snimkama.
Iz rezultata subjektivnog ocjenjivanja topline, vlažnosti i udobnosti u tri uvjeta okoline vidljivo je smanjenje osjećaja udobnosti i povećanje osjećaja vlažnosti i topline s porastom temperature. Pri temperaturi 32 ºC apsorpcija znoja u materijalu trostruko je veća od apsorpcije na temperaturi 23 ºC. Uočene su i znatne razlike između intenziteta znojenja muških i ženskih ispitanika, pa je tako pri temperaturi 32 ºC apsorpcija znoja kod muških ispitanika 2,3 puta veća nego kod ženskih. Usporedbom područja na kojima je vidljivo nakupljanje znoja na majici s termografskom snimkom uočava se u tim zonama promjena temperature.
Sweat absorption is investigated using the subjective and objective methods. The subjective investigation analyses the physiological responses of male and female volunteers wearing two kinds of ...textile fabrics (cotton and polyester) during certain physical activity. The subjects were exposed to the different conditions of ambient temperature (23, 26, 29 and 32 °C) and constant relative humidity of 67 ± 3%. In the objective investigation the sweating guarded hotplate (SGHP) system was used that stimulates the processes of sweat transfer between the human skin, textile material and environment. The results of mass absorption obtained from the objective measurement on the sweating guarded hotplate show the similar trend as the results obtained during the subjective measurement.
