The growth of poultry meat production is increasing industrial waste quantities every year. Feathers represent a huge part of the waste, and international directives and restrictions prevent landfilling of such biodegradable materials with high burning values. Furthermore, with their unique properties, poultry waste feathers are already a reliable resource for many byproducts, such as keratin extraction, fibres, hydrogel production, etc., all trying to achieve a high-added value. However, mass reduction of waste feathers into useful applications, such as development of alternative building materials, is also an important aspect. To take advantage of feathers’ thermal insulation capabilities, sound damping, and biodegradability, we worked towards mixing waste feathers with wood residues (wood shavings, dust, and mixed residues) for production of composite fibreboards, comparable to the market’s medium density fibreboards. The emphasis was to evaluate waste poultry feathers as the component of natural insulation composites, along with mixed waste wood residues, to improve their mechanical properties. Various composite fibreboards with different shares of wood and feathers were produced and tested for mechanical, thermal, and acoustic properties, and biodegradability, with comparison to typical particle boards on the market. The addition of waste feather fibres into the fibreboards’ structure improved thermal insulation properties, and the biodegradability of fibreboards, but decreased their bending strength. The sound transition acoustic loss results of the presented combination fibreboards with added feathers improved at mid and high frequencies. Finally, production costs are estimated based on small scale laboratory experiments of feather processing (cleaning and drying), with the assumption of cost reduction in cases of large industrial application.

In the field of long-life fatigue, predicting fatigue lives and limits for mechanical components is crucial for ensuring reliability and safety. Fracture mechanics tools have enabled the estimation of fatigue lives for components with small cracks or defects. However, when dealing with defects larger than the microstructural characteristic size, estimating the fatigue resistance of a material requires determining the cyclic resistance curve for the defect-free matrix, which depends on knowledge of the material’s intrinsic fatigue limit. This study focuses on the experimental evidence regarding the intrinsic fatigue limit and its correlation with naturally nucleated non-propagating cracks. Fracture mechanics models for small crack propagation are introduced, and their disparities and limitations are analyzed. The concept of intrinsic fatigue limit is then introduced and applied to reanalyze a recent publication. Methods for estimating the intrinsic fatigue limit are explored and applied to experimental results reported in the literature. The need to clarify and accurately predict the intrinsic fatigue limit is highlighted in alloys where the processing generates defects larger than the microstructural size of the matrix, as often observed in materials and components produced using additive manufacturing.

Porous tantalum has been extensively used in orthopaedic surgery, including uncemented total knee arthroplasty (TKA). Favourable results were reported with earlier monobloc tibial components and the design evolved to modular implants. We aimed to analyse possible causes for extensive medial tibia bone loss, resulting in modular porous tantalum tibia baseplate fracture after primary TKA. Retrieved tissue samples were scanned with 3 MeV focused proton beam for Proton-Induced X-ray Emission (micro-PIXE) elemental analysis. Fractographic and microstructural analysis were performed by stereomicroscopy. A full 3D finite-element model was made for numerical analysis of stress–strain conditions of the tibial baseplate. Histological examination of tissue underneath the broken part of the tibial baseplate revealed dark-stained metal debris, which was confirmed by micro-PIXE to consist of tantalum and titanium. Fractographic analysis and tensile testing showed that the failure of the tibial baseplate fulfilled the criteria of a typical fatigue fracture. Microstructural analysis of the contact surface revealed signs of bone ingrowth in 22.5% of the surface only and was even less pronounced in the medial half of the tibial baseplate. Further studies are needed to confirm the responsibility of metal debris for an increased bone absorption leading to catastrophic tibial tray failure.

In this study, a numerical simulation of a single pass welding of two thick-walled pipes with the buried-arc method was performed in order to determine the residual stresses caused by welding. The numerical simulation procedure in the thermal analysis was performed by the element birth and death method while the structural analysis was performed simultaneously, without the application of the element birth and death technique in order to reduce the duration of the numerical simulation. The simulation results were validated by experimental residual stress measurements on the outside surfaces of the welded model using the X-ray diffraction technique. A good agreement between the results of the numerical simulation and experimental measurements was confirmed.