A Comparative Study on the Temperature Effect of Solid Birch Wood and Solid Beech Wood under Impact Loading

In order to use wood for structural and load-bearing purposes in mechanical engineering, basic information on the impact behaviour of the material over a wide temperature range is needed. Diffuse porous hardwoods such as solid birch wood (Betula pendula) and solid beech wood (Fagus sylvatica) are particularly suited for the production of engineered wood products (EWPs) such as laminated veneer lumber (LVL) or plywood due to their processability in a veneer peeling process. In the frame of this study, solid birch wood and solid beech wood samples (300 × 20 × 20 mm3) were characterised by means of an impact pendulum test setup (working capacity of 150 J) at five temperature levels, ranging from −30 °C to +90 °C. The pendulum hammer (mass = 15 kg) was equipped with an acceleration sensor in order to obtain the acceleration pulse and deceleration force besides the impact bending energy. In both solid birch wood and solid beech wood, the deceleration forces were highest at temperatures at and below zero. While the average impact bending energy for solid birch wood remained almost constant over the whole considered temperature range, it was far less stable and prone to higher scattering for solid beech wood.

Structure heterogeneity and mechanical properties studied in thickness up to 100 mm of low-alloyed shipbuilding steel sheets with a yield strength not less than 420 MPa

This paper presents a study of changes in the structure and properties in thickness of rolled sheets up to 100 mm of low-alloyed shipbuilding steel with a yield point not less than 420 MPa. The fracture surface of samples after impact bending tests at low temperatures was investigated. It was found that the combination of the parameters of lath morphology bainite (fraction, areas average size and length) and the size of structural elements at given tolerance angles of 5 and 15° (indicating the presence or absence of a developed subgrain structure of deformation origin) determine the level of impact work at low temperatures testing.

Effect of Hostile Solutions on the Residual Fatigue Life of Kevlar/Epoxy Composites after Impact Loading

Due to the enormous benefits inherent to composite materials, they have been widely used in the most diverse fields of engineering. Therefore, it is not surprising that in many of these applications they can be exposed to hostile environments, which can affect the mechanical performance of such materials. Therefore, the main goal of this work was to study the effect of immersion into different hostile solutions on the impact strength and, subsequently, to evaluate the residual fatigue life. For this purpose, the specimens were initially immersed into solutions of hydrochloric acid (HCl), sodium hydroxide (NaOH), sulphuric acid (H2SO4), diesel, distilled water, and seawater. Subsequently, the specimens were subjected to impact loads with an energy of 12 J and, finally, subjected to fatigue loads to assess the residual fatigue life. Seawater and NaOH solution provided the lowest impact strength. This was confirmed by the lower energy restored and impact bending stiffness (IBS), a parameter that allows evaluating the damage resistance of a composite. In terms of restored energy, for example, the seawater promoted a decrease around 30.4% in relation to the value obtained with non-immersed samples, while this value was 27.6% for the alkaline solution (NaOH). In terms of IBS, the lowest values were also obtained with these solutions (437.4 and 444.9 N/mm, respectively). Finally, the lowest residual fatigue life was also observed for these two solutions, and it was noticed that there was a direct relationship between the IBS and the residual fatigue life.

Effect of span length on the impact bending strength of poplar and pine woods

Solid wood is an important engineering material. Solid wood has superior properties, such as being renewable, easily processed, relatively inexpensive, and having higher mechanical properties relative to its density than any other engineering materials. Density, moisture content, tree species, knots, cracks, and some other variables influence the mechanical properties of wood. In this study, the effect of span length on the impact bending strength (IBS) of wood was investigated. Poplar and pine wood samples were used as test materials in the experiments. The IBS measurements were carried out following TS 2477 (1976) using a pendulum impact bending machine. Tests were conducted for various span lengths of 10, 15, 20, 25, 30, and 35 cm. The results indicated that there is a relationship between IBS and span length. The highest impact bending strength was obtained with a span length of 10 cm for poplar and pine wood. The relationship between IBS and span length was parabolic. The coefficients of determination were 0.94 and 0.99 for poplar and pine wood, respectively.

Structural Analysis of Motorcycle Alloy Wheel

Alloy wheels in the motor cycle play major role to carry the load over the spoke wheels. The shape and orientation of the spokes are responsible for withstand the loads which are acting on the alloy wheel rim and hub bearing surface. These alloy wheel spokes are subjected to different types of loads i.e., radial loads, impact load, bending load, torsion load and maximum deflection load. So it is necessary to study the response of the wheel under these types of loads before the product going into the market. In the present article 4 models of motor cycle alloy wheel are modeled based on the dimensions in the reference article. The material chosen for the analysis of the alloy wheel is aluminum alloy which is homogenous in nature having isotropic properties. The magnitude of the five different loading conditions and boundary conditions are taken from the Automotive Industry Standards (AIS). The four models of alloy wheels are analyzed under radial, impact, bending, torsion and maximum deflection loads cases by using by using ANSYS workbench. The results show that all four models are having enough fatigue life, strength and stiffness against the different loading conditions.

Physical, mechanical, and decay resistance properties of heat-treated wood by Besson® process of three European hardwood species

Description of the subject. In Europe, the heat treatment of native wood species is gradually becoming an industrial reality. It provides a promising alternative to both the use of naturally durable, essentially tropical woods and the use of chemical preservative treatments based on biocides. Objectives. The aim of this study is to quantify the effect of heat treatment on the physico-mechanical and decay resistance properties of three native hardwood species (oak, ash, beech + steamed beech). Method. The wood was heat-treated in accordance with the Besson® process. The standard physical and mechanical tests including hardness, modulus of elasticity in static bending, static bending, axial compression, splitting and impact bending strengths, have been performed on 15 treated and 15 control associated samples for each species. The standard durability test on fungi exposed 60 treated and 60 control samples to each fungus. Results. The results show a decrease in the equilibrium moisture content and an increase in dimensional stability of heat-treated wood for the three species studied. The modulus of elasticity, hardness and axial compression strength increase slightly after the heat treatment, while static and impact bending strength and splitting strength may considerably decrease. The fungal durability of oak heartwood and ash increased until class 1, beech and steamed beech until class 3. Conclusions. The global approach of this study allows a complete and precise characterization of the technological properties of three native hardwood species after heat treatment. New uses of these native species can thus be explored.

Biological Resistance of Elm (Ulmus carpinifolia var. Umbelifera) Trees against Fungal Endophytes and White Rot Decay Fungi

Urban trees are one of the valuable storage in metropolitan areas. Nowadays, a particular attention is paid to the trees and spends million dollars per year to their maintenance. Trees are often subjected to abiotic factors, such as fungi, bacteria, and insects, which lead to decline mechanical strength and wood properties. The objective of this study was to determine the potential degradation of Elm tree wood by Phellinus pomaceus fungi, and Biscogniauxia mediteranae endophyte. Biological decay tests were done according to EN 113 standard and impact bending test in accordance with ASTM-D256-04 standard. The results indicated that with longer incubation time, weight loss increased for both sapwood and heartwood. Fungal deterioration leads to changes in the impact bending. In order to manage street trees, knowing tree characteristics is very important and should be regularly monitored and evaluated in order to identify defects in the trees.