Applied Mechanics and Materials Vol. 827

Abstract: This paper reports the results of measurements during hardening and drying of specimens made of alkali activated slag mortars. The aim of this paper is introduce the effect of curing method and time on the microstructure of alkali activated slag mortars. An understanding of microstructure−performance relationships is the key to true understanding of material behaviour. The results obtained in the laboratory are useful to understand the various stages of micro-cracking activity during the hardening process in quasi-brittle materials such as alkali activated slag mortars and extend them for field applications.

Abstract: The paper deals with the experimental analysis focused on the determination of strain in wooden building structures using optical fibers with FBG sensors. Firstly, optical fibers were used to measure displacements of layers and surface strain of the lower surface of the ceiling panels made from mechanically jointed cross laminated timber (CLT). The measured displacement values of the optical fibers were compared with the results obtained from the inductive displacement sensors. Secondly, optical fibers were used for long-term monitoring of the roof structure of the sports hall. The fibers were mounted on chords of timber trusses and their correct function was verified by a load test.

Abstract: Gypsum, as well as cementitious materials, attains after hardening relatively high compressive strength, however its tensile (or flexural) strength is low. Therefore, it is often necessary to improve the tensile properties, such as strength and ductility, via suitable modifications or by adding reinforcement. Dispersed reinforcement appears to be quite suitable for most of the application, allowing to utilize waste products such as recycled wires from automobile tires or metal textiles etc. The presented study was focused on the influence of such reinforcement on the behavior of gypsum specimens, in particular on the flexural strength and ductility of the reinforced material.

Abstract: The methodology, used for determining the structure material elastic constants, is based on mechanical tests, being mostly tensile ones, applied on partially loaded specimens. There be can glass materials used as different alloy elements, therefore the glass elastic constants can vary considerably. However, using classic glass tensile specimens for tensile tests can be problematic, due to their production and implementation of tensile tests. Experimental methods for identifying the glass Young's modulus of elasticity and Poisson's ratio are based on a comparison of the displacement measurements applied on the glass beam, or curved rod, samples, combined with their displacements calculation.

Abstract: This article represents a multidisciplinary approach to biomechanics (engineering + medicine) in the field of distal tibia fractures. The objective of the present study was to carry out a strength and reliability assessment of a medial plate for the treatment of distal tibia fractures. This was performed via numerical modelling (FEM) and experimental methods (compression test and Electronic Speckle Pattern Interferometry – ESPI method). The plate is used for internal fixation in orthopaedics and traumatology. Analyses were performed for non-fused bone with comminuted fracture in the distal metaphysis (i.e. unsuccessful treatment, where all loads in the metaphysis are carried by the plate). An anatomical tibia model (based on CT images in Mimics software) was used for FE analysis. In the experiments, the bone was replaced with a shaped piece of spruce wood (based on Mimics software) and the plate was loaded until its failure (major plastic deformation). Numerical and experimental results were evaluated and compared.

Abstract: The submitted experimental analysis identifies, defines and compares the micromechanical properties of peripheral and supporting layers of intraosseous parts of dental implants through a nanoindentation method. The aim of the micromechanical tests is determination of elastic modulus and hardness. Investigated implants are characterized by the cylindrical shanks with surface plasma modification by hydroxyapatit. From the evaluated results it is evident that elastic modulus of peripheral layers of the compared samples ranges from 17 GPa to 157 GPa. The submitted work also includes a detailed microscopic analysis of surface morphology and chemical composition.

Abstract: The presented paper is mainly focused on nanoindentation of damaged human teeth, which have been treated with amalgam filling and describing the micromechanical properties (reduced elastic modulus Er and hardness H). The analysis was carried out on two samples of tooth no. 37, the first from a woman (48 years old) and the second from a man (26 years old). For both teeth was the main cause of the extraction an advanced stage of periodontitis chronica. The provided treatment of the tooth decay has been realized using amalgam filling with a different depth of cavity drilling. Within the analysis, we have made a series of indentation experiments in the transversal sections of the teeth. In these sections, we have measured the mechanical properties in individual dental materials for the sake of determining the influence of the degradation of dentin damaged by tooth decay. The differences of micomechanical parameters occur in the dentin area (Er ≈ 7.6 GPa in the dentin-amalgam interface and Er ≈ 30.2 GPa in the center of the dentin wall). Lesser variance of values is present in the enamel area, where the difference is less than 11 % in the enamel-amalgam interface.

Abstract: Research of the correlation of the biomechanical characteristic of a sitting human and car seat is based on measurements of several basic parameters, such as value of the area contact pressure, map of contact temperature, contact humidity, etc. So obtained map of surface each parameter which we can compare at a same time and so we can identify correlations between these parameters and biomechanical properties of human, e.g. human anatomy, the body forms, age, sex physique etc. Based on these analyzes is possible to optimize the levels of this parameters for obtaining the ideal seating comfort. The correlation between fatigue for the driver and sitting comfort is described in many publications dealing with this theme. However, a repeatability real experiment in a car is questionable [1]. It is therefore preferable to perform these measurements in the laboratory and simulate the same conditions as in moving car at a constant ambient temperature and humidity, with the same test persons. The most suitable is the use in the measurement of different types of car seats and various human.

Abstract: The collision of standing passenger with floor is solved during rail vehicle emergency braking. The fall is serious type of passenger accident. For this purpose the model of rail vehicles interiors floor is created. The simulated behavior of passenger impact can predict useful information for experimental validation of floor properties.

Abstract: The inflation-extension tests were performed with developed hybrid composite manufactured from biological collagenous matrix and reinforced with polyester mesh. One sample was made without the mesh. This control specimen showed compliant and almost linear behavior. Tests of samples with integrated mesh in the matrix demonstrated that mechanical properties of final composite could be modulated by placing of its reinforced component in the matrix. It was shown that we can obtain response from stiff and linear to nonlinear and very compliant depending on the position of the mesh within biological matter.