|
|
Pore Size Distribution of Human Trabecular Bone - Comparison of Intrusion Measurements with Image Analysis
Doktor, Tomáš ; Valach, Jaroslav ; Kytýř, Daniel ; Jiroušek, Ondřej
This paper deals with pore size distribution assessment of trabecular structure of human proximal femur. Two distinct methods for estimation of the pore size distribution histograms are tested, mercury intrusion porosimetry and image analysis. For the image analysis two-dimensional images of crosssections of the specimens were used and the pore size distribution was estimated using a stereological calculation method based on the geometrical properties of an idealized pore. Comparison of the results of both methods is presented. Suitability of both methods for biological materials is discussed regarding to mechanical properties of these materials, characteristics of pores and range of pore sizes present in the structure.
|
|
|
Assessment of C/PPS composites degradation indicators using acoustic measurement
Kytýř, Daniel ; Valach, Jaroslav ; Doktor, Tomáš ; Jiroušek, Ondřej
Changes of mechanical properties, namely of modulus of elasticity, often play a role of damage accumulation indicators in the framework of fatigue behaviour of composite materials. In order to improve the reliability of these indicators for identification of material degradation process it is necessary to eliminate the influence of external loading and volume forces associated with thermal expansion of heterogeneous material at various temperatures. Therefore the paper deals with description of experimental assessment of relation between external load and material stiffness and also studies the dependency of material stiffness on temperature. For the monitoring of degradation process ultrasonic measurement was used. Obtained results are discussed with respect to fatigue testing of material and also interpreted from the micromechanical point of view.
|
|
| |
|
| |
|
|
Historic Mortars - HMC 2010 and RILEM TC 203-RHM final workshop
Válek, Jan ; Groot, C. ; Hughes, J.
The HMC2010 conference and TC 203-RHM final workshop took place in Prague 22-24 September 2011. The event was organised by the Institute of Theoretical and Applied Mechanics of the Academy of Sciences of the Czech Republic (ITAM AV ČR) in cooperation with RILEM. The conference was chaired by J. Válek of ITAM. The final workshop was chaired the TC 203-RHM chairman and its secretary C. Groot of TÚ Delft and J. Hughes of University of the West of Scotland. Members of the TC 203-RHM were acting also as the International Scientific Committee members of the conference. The HMC2010 Organising Committee was composed of the staff members of ITAM AV ČR. The event was attended by 190 participants from 30 countries. Such a number of participants was regarded as a great success considering its rather narrow and specific scope and also the fact that it was only the 2nd conference in this future to be regular series.
|
|
|
Study of historic mortars - Inspiration for the lime industry?
Válek, Jan
Study of historic mortars is motivated by the desire of understanding of these materials and also by the contemporary approach towards repair of architectural heritage. Detailed study contributes to new scientific findings for example about durability of materials and their degradation agents. Results of study of historic mortars can be an inspiration for production of modern lime based mortars. The focus on authenticity and understanding of historic materials leads to a reintroduction of production of some binders for repair of historic buildings. The 2nd Historic mortars conference joined with the RILEM TC 203-RHM - Repair mortars for historic masonry -was held in Prague earlier this year. This paper refers about selected contributions of this conference.
|
|
|
Impact of Non-Uniform Distribution of Temperature on the State of Stress of Masonry
Beran, Pavel
Deterioration of masonry is caused by inordinate loading and by climatic actions. Climatic cyclic thermal stress in a structure is incurred by unequal temperature gradient across the thickness of homogenous or heterogeneous masonry. Thermal gradient also causes significant stress close to the interface between stone and mortar in masonry made of components with different thermal expansion properties. The values of thermal stress increase with higher thermal gradient. Impact of insolation, absorption of solar radiation, air temperature around the structure, heat transfer coefficient, coefficient of heat conduction, and heat capacity to the temperature gradient in the wall exposed to the exterior weather conditions were investigated with a numerical model. All of these effects or material properties affect the maximal surface temperatures in masonry during summer.
|
|
| |
|
| |
|
| |
guest ::
