No abstract

The paper deals with the study of the goose eggs behaviour under compressive loading between two plates using testing device TIRATEST. The influences of the loading orientation as well as the effect of compressive velocity are studied. 226 eggs from Landes geese were chosen for the experiment. Eggs have been loaded between their poles and in the equator plane. Five different compressive velocities (0.0167, 0.167, 0.334, 1.67 and 5 mm.s-1) were used. The increase in rupture force with loading rate was observed for loading in all direction (along main axes). Dependence of the rupture force on loading rate was quantifies and described. The highest rupture force was obtained when the eggs were loaded along their axes of symmetry (X-axis). Compression in the equator plane (along the Z-axis) required the least compressive force to break the eggshells. The eggshell strength was described by the rupture force, specific rupture deformation and by the absorbed energy. The rupture force is highly dependent on compression speeds. The dependence of the rupture force on the compression velocity can be described by a power function. The same is valid for the rate dependence of the energy absorbed by the egg up to the fracture. The rate sensitivity of the Goose's eggshells strength is significantly higher than that reported for the hen's eggs

The rheological behavior of liquid egg products (egg yolk, egg white, and whole liquid egg) was studied using a concentric cylinder viscometer. Eggs of three poultry specimens were used: hen (Isa Brown), Japanese quail (Coturnix japonica), and goose (Anser anser f. domestica). Rheological behavior was pseudoplastic and flow curves fitted by the power law model (Herschel-Bulkley and Ostwald-De Waele). The meaning of rheological parameters on friction factors and velocity profiles during flow of liquid egg products in tube has been shown.

The mechanical behaviour of eggshell membranes under tensile loading has been studied. Samples from diff erent bird species (hen, goose and Japanese quail) have been used. Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The experiments were performed at fi ve loading velocities 1, 10, 100, 400 and 800 mm.min −1 . The main parameters describing the eggshell strength increase with the loading rate. This dependence exhibits the same qualitative features as the rate dependence of the eggshell strength.

In this study, the mechanical behaviour of Japanese quail eggs was determined in terms of average rupture force, deformation, and energy absorbed during fracture. Eggs were characterized by some physical and geometrical properties, such as mass, length, width, eggshell thickness, geometric mean diameter, surface area, sphericity, volume, and eggshell radii of curvature. Egg samples were compressed along the axis of their symmetry (X axis) and perpendicularly to this axis (Z axis). Four different compression rates were used: 0.0166, 0.166, 1.666, and 5 mm/s. The highest rupture force, deformation at the egg's rupture, and energy absorbed up to the fracture were found when Japanese quail eggs were loaded along their X-axis. The rupture force increased with the compression (loading) rate. The rate sensitivity of the eggshell rupture force was close to that observed for the hen's eggs.

NEDOMOVÁ ŠÁRKA, BUCHAR JAROSLAV, STRNKOVÁ JANA: Mechanical behaviour of Ostrich's eggshell at compression. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 3, pp. 729-734 The deformation and fracture behaviour of Ostrich's eggs at the static compression has been investigated. The mechanical properties of egg to compression were determined in terms of average rupture force, specifi c deformation and rupture energy along X and Z axes. Exact description of the eggshell counter shape has been used for the verifi cation of a common accepted theory of the compression of bodies of convex form. The eggshell strength seems to be an unique function of the static stiff ness. The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. The specifi c deformation and rupture energy required for the eggs tested was lower along the X axis than the Z axis. The highest measure of fi rmness in the eggs tested was found to be along their X axis. Young's modulus of the elasticity, E, has been also evaluated. Its value is independent on the direction of the egg compression. The value of E is approximately two times higher that of the chicken eggs. strength, modulus of elasticity, eggshell stiff ness, rupture force

NEDOMOVÁ, ŠÁRKA, STRNKOVÁ, JANA, BUCHAR, JAROSLAV, SÝKORA, VLADIMÍR: The eff ect of temperature and loading rate on the rheology of butter. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 5, pp. 1349-1356 Series of the indentation of the cone (60°) by the constant speed into blocks butter has been conducted. The indentation tests were performed at diff erent speeds (1, 6 and 60 mm.min −1 ), and the corresponding force -displacement responses were fi tted with an analytical solution to obtain the time-dependent constants and the instantaneous force-displacement response. Experiments have been performed on 18 diff erent commercially available butters. A puncture test was performed to investigate the rheological properties of the food materials at 4 °C and at 19 °C. The indentation force decreases with the temperature. It increases with the loading rate. The recently proposed method for the indentation of the cone into viscoelastic solids have been used for our data analysis. This procedure which needs the use of the numeric methods enables to obtain stress relaxation modulus which describes the initial viscoelasticity of the tested materials.butter, cone penetrometry, loading rate, rheology, relaxation modulus

TRNKA JAN, STOKLASOVÁ PAVLA, STRNKOVÁ JANA, NEDOMOVÁ ŠÁRKA, BUCHAR JAROSLAV: Vibration properties of the Ostrich eggshell at impact.