This paper aims to evaluate the potential use of closed-cell aluminium alloy integral-skin foams as stiffening elements for aluminium alloy thin-walled structures that are main basic components in the concept and design of automotive body parts. Foam specimens were prepared using the powder metallurgical route, inserted into empty thin-walled tubes and subjected to quasi-static and dynamic bending loading conditions. The effect of introducing foam into tubes was evaluated using the infrared thermography during the three-point bending tests. The foam-filled tubes, empty tubes and foams are compared in terms of the maximum load carrying capacity, crash energy absorption, specific energy absorption and deformation modes. Results showed that the foam filling leads due to interaction between the tube wall and foam filler, causing an increased bending response of the filled tubes which exceeds the sum of the bending response for the individual components. Their deformation mode is a combination between the modes of the individual components.
COBISS.SI-ID: 17349398
Needle-punched webs for wet cleaning wipes were produced using a dry-laid method of web- forming. Fibrous webs with a different content of hydrophilic viscose and hydrophobic polyester fibers, as well as webs made from 100 % polyester fibers, were utilized during this study. The webs were compared in terms of their water absorption capacity on the basis of their basic construction parameters, such as fiber fineness, raw material (e.g. fiber density), and web density. The higher water absorption capacity of the viscose/polyester-blended needle-punched webs was achieved at higher content of viscose fibers which coincide with the higher fiber density, finer fibers, and lower web density. A prediction model regarding water absorption capacity of viscose/polyester needle-punched webs was developed on the basis of the mentioned construction parameters and a non-deterministic modelling method, e.g. genetic algorithms, and could provide a guideline for the engineering of nonwoven webs in order to fit the desired water absorption capacity.
COBISS.SI-ID: 18035734
A computational model for determination of the fatigue life of sintered gears in regard to bending fatigue in a gear tooth root is presented. The proposed model is based on the stress-life approach in which the multi-axial state of stress, the mean stress effect, the influence of surface roughness, and the notch effect are studied when determining the fatigue life of a treated gear pair. The required material parameters (the fatigue strength coefficient and the fatigue strength exponent b) are determined experimentally on a uni-axial tension/compression test machine with a load ratio of R = 0.
COBISS.SI-ID: 13722907
Huge areas of work are still done manually and require the usages of different powered and non-powered hand tools. In order to increase the user performance, satisfaction, and lower the risk of acute and cumulative trauma disorders, several researchers have investigated the sizes and shapes of tool-handles. However, only a few authors have investigated tool-handles' materials for further optimising them. Therefore, as presented in this paper, we have utilised a finite-element method for simulating human fingertip whilst grasping tool-handles. We modelled and simulated steel and ethylene propylene diene monomer (EPDM) rubber as homogeneous tool-handle materials andt wo composites consisting of EPDM rubber and EPDM foam, and also EPDM rubber and PU foam. The simulated finger force was set to obtain characteristic contact pressures of 20 kPa, 40 kPa, 80 kPa, and 100 kPa. Numerical tests have shown that EPDM rubber lowers the contact pressure just slightly. On the other hand, both composites showed significant reduction in contact pressure that could lower the risks of acute and cumulative trauma disorders which are pressure-dependent. Based on the results, it is also evident that a composite containing PU foam with a more evident and flat plateau deformed less at lower strain rates and deformed more when the plateau was reached, in comparison to the composite with EPDM foam. It was shown that hyper-elastic foam materials, which take into account the non-linear behaviour of fingertip soft tissue, can lower the contact pressure whilst maintaining low deformation rate of the tool-handle material for maintaining sufficient rate of stability of the hand tool in the hands. Lower contact pressure also lowers the risk of acute and cumulative trauma disorders, and increases comfort whilst maintaining performance.
COBISS.SI-ID: 17081110
A new method to fabricate uni-directional porous (UniPore) metal employing the explosive compaction process of cylindrical pipe assembly is proposed. The proposed fabrication method enables production of long rods with uniform longitudinal pores along the whole rod length, exhibiting typical porous material behavior in the transverse direction while retaining solid material behavior in the longitudinal direction under compressive mechanical loading. Micro structural analysis of the fabricated samples demonstrates strong interface bonding between pipe walls. Many practical applications of UniPore porous metal are to be expected due to its unique properties and some preliminary investigations show very high efficiency of such structure for heat exchangers or heat sink applications.
COBISS.SI-ID: 18113814