Applied Mechanics and Materials Vol. 732

Abstract: This paper deals with the mechanical properties of test specimens of commercially available PIM feedstocks based on a stainless steel powder. After injection molding, a part of the polymer binder has been removed in water. This process was followed by thermal removal of residual binder and sintering at 1360 °C in hydrogen atmosphere. For production of the mechanical test bars fresh and recycled feedstocks were employed. The aim is to determine the changes in mechanical performance resulting from injection molding processing stage, especially possible separation of feedstock components – the stainless steel powder and the polymer binder

Abstract: This study builds on experiments with different combinations of tension and torsion pre-stresses which were published in [1]. The results were particularized by new tests for combined pre-stresses in normal and shear components. The ratio between normal and shear pre-stresses was 3:2 in agreement with the coefficient k_c. The same material structural low carbon ČSN 41 1523.1 steel after normalization annealing was used for specimens. The results were compiled and displayed in a three-dimensional Haigh diagram with normalized coordinates and interlaid by corresponding terminal lines.

Abstract: Article presents the results of an experimental program aimed at investigating of the mechanical properties of composites based on aluminous cement with the addition of basalt fibres, which could be used in the manufacture of components resistant to high temperatures, including the retention of mechanical properties. Silica composites based on Portland cement and silica aggregates are not able to resist the effects of high temperatures [1], therefore a heat resistant mixtures in this experiment includes only components that are able to resist the effects of high temperatures.

Abstract: This paper discusses characterization of physical and mechanical properties of tissues of Norway spruce. Cell wall is composed of several layers, which is, due to their small size, difficult to characterize. For this reason, the work uses a combination of methods, atomic force microscopy (AFM) and nanoindentation. AFM is used to determine the topography of samples and nanoindentation to determine micromechanical properties of wood tissues. Prepared samples of glue laminated timber were tested by quasi-static and dynamic nanoindentation (modulus mapping technique) method.

Abstract: Nanofiber textiles became indispensible in medicine and many other industries because of their unique properties. Recently, the pioneering works suggested their use also in a building industry in the form of moisture barriers. For a better chemical stability and resistance to air humidity it is suitable to stabilize the spun textiles. Our study is focused on the influence of the physical-chemical stabilization, also called crosslinking, on the mechanical properties of nanofiber textiles in tension, namely stiffness, strength and ductility. During the process of crosslinking the individual fibers bond in nodes, ensuring a better spatial integrity. However, the presented results indicate that the stabilized nanofiber textiles exhibit significantly lower ductility while their ultimate strength is lower only by about 10 %.

Abstract: Anisotropy is the characteristic which is typical for most materials, especially woven fabrics. Influence of direction of tensile force action on the properties of the fabric is big and frequently tested. The woven fabric can be defined as orthogonal elastomer. The values of elastic modulus of woven fabrics for different angles of extension direction were analyzed. Three types of fabric samples of different weaves (plain, twill, sateen) and the same raw material composition were tested under tensile forces in seven directions oriented with 15° increment with respect to the weft direction. Elastic modulus of woven fabrics was determined experimentally in the laboratory. Based on the experimentally obtained values, theoretically calculated elastic modulus for arbitrarily chosen fabric directions was calculated. A good agreement between experimental results and the calculated obtained values of the elastic modulus was shown, so the theoretical equations can be used with high accuracy to calculate the elastic modulus of the fabric in various directions. Therefore, the measurements need to be implemented when the tensile force acting on the fabric only in the warp (90°), weft (0°) and at angle of 45°.

Abstract: This paper describes an experimental study on the pure shear properties of E-Glass woven fabric by picture frame test. During shear deformation, the fabric yarns experience large angular change between warp and weft yarns. The picture frame test is one of the fundamental methods to characterize the in-plane shear behaviour of woven fabrics and can produce a quite uniform shear deformation state in the fabric sheet. Tests are conducted on two different size of EGlass specimens 40x40 mm and 80x80 mm. For a double increase the specimen size, the values of shear force and axial load are also almost double increase at the maximum displacement and shear angle.

Abstract: Presented paper deals with ratcheting prediction in the field of line rolling contact. The main aim is to simulate the wear process due to the contact fatigue on inductively hardened sample of R7T material. For the stated purposes, the authors have used the wear model based on shear band cracking mechanism and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. Obtained results are subsequently compared with experimental data as well as with metallographic analysis.

Abstract: The paper provides experimental results from tensile and flexural tests of HPL composites. Mechanical properties of HPL laminates from four worldwide producers (Fundermax, Polyrey, Abet and Rexin) are compared. Composites are compared due to their stiffness and strength, both tensile and flexural. The exterior environment effect on mechanical behaviour of composites in service load conditions are presented too.

Abstract: The paper deals with progressive and fatigue damage of long fiber E-glass epoxy composite, its residual stiffness degradation and corresponding transverse matrix crack density induced by load-controlled tension. Constant-amplitude fatigue tests in repeated tension of plain [±60]_S; [±30]_S; [0]₈ and [0/90₂/±45/90]_S samples were performed. Sudden onset of transverse matrix cracking and consequent gradual increase of its density has been observed in off-axis plies. The crack density increases with increasing number of cycles or load. Consequently, residual stiffness of the laminate decreases. It has been concluded that progressive/fatigue damage of the laminate is not a continuous homogenous process but the series of discrete sudden events emerging at ply level.