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Application of High Energy Absorbing Materials for Blast Protection

Abstract

In the current century, building protection is very important in the face of terrorist attacks. The old buildings in Europe are not sufficiently resilient to the loads produced by blasts. We still do not fully understand the effects of different explosives on buildings and human bodies. [1–3] Computing blast loads are different from that of traditional loads and the material selection rules for this type of impact load are diverse. Historical and old buildings cannot be protected simply by new walls and fences. New ways need to be found to improve a building’s resistance to the effects of a blast. It requires sufficiently thin yet strong retrofitted materials in order to reinforce a building’s walls [4–6].

Open access
Comparative Study of Roman Iron Slags Discovered in the Roman Auxiliary Fort and Settlement of Călugăreni

Abstract

Iron slag samples unearthed at the eastern border of Roman Dacia, in the auxiliary fort and the military settlement of Călugăreni (Mikháza) are investigated by macroscopic inspection, optical microscopy (OM) and FTIR spectroscopy in order to comparatively characterize their macro- and microstructure as well as their mineralogical composition. During the recent archaeological excavations, a large number of iron artefacts were discovered together with a great quantity of iron slag fragments. The present paper focuses on the data obtained from 17 slag samples.

Open access
Corrosion Testing of Additively Manufactured Metals and Biomedical Devices

Abstract

Additive manufacturing (AM) is becoming increasingly important, making it possible to produce a product in a short time, to specific individual requirements, and even in the presence of the customer. This research is related to direct metal laser sintering of additive manufacturing. This new technology is increasingly being used in more sectors, for example in biomedical industry, where a damaged product can potentially endanger human life. Corrosion tests were carried out during our research. Cyclic voltammetry curves and corrosion rates were determined with a potentiostat. Two typical biocompatible implant materials were compared, a cobalt chromium alloy (powder metallurgy) and a titanium alloy (3D printed). The results will help in specifying the corrosion properties of additively manufactured materials.

Open access
The Influence of Heat Treatment on the Mechanical Properties of 3D-Printed Cobalt-Chrome Alloy Used in Dental Laboratory Practice

Abstract

The material used for manufacturing of dental implantation prostheses is cobalt-chromium alloy. The following study presents a new heat treatment technology for dental implantation prostheses. Specimens were created with the innovative technology of 3D printing. The brittleness of specimens subjected to heat treatment with parameters recommended by the manufacturer made it necessary for us to reconsider the heat-treating process. After changing given heat treatment processes, tensile and hardness tests were performed. From these tests, the optimal heat treatment process technology was chosen.

Open access
Investigation of Laser Welding Technology of Diamond Drilling Segments

Abstract

Segments containing diamond particles are fixed to replaceable inserts or to steel tool bodies for cost-effectiveness. The joining technology used should meet both environmental and technical requirements. The joining zone is subjected to high mechanical and significant thermal loads during use. In the event of an improper joint, the segments may detach from the base and fly away causing injury. Nowadays, many methods of welding or brazing are used to fix diamond segments. Among the possible segment fixing technologies, laser beam welding has been investigated. The microstructure of the joints has been examined by optical and scanning electron microscopy and chemical element maps have been recorded. Joints have been subjected to fracture and hardness testing. The mechanical properties and composition changes of the joints with different joining technologies have been evaluated and compared.

Open access
Mechanical Studies of Injection Molded Composites with Polypropilene Matrix

Abstract

The wide use of composite materials is mainly due to their excellent strength / mass ratio, corrosion resistance and relatively low price. Approximately 35-40% of the fibre-reinforced composites are made of thermoplastic polymers in which fibreglass, carbon or natural fibres are most often used as reinforcement, while the remaining 60 – 65% is made up of high-tech carbon or glass fibre-reinforced thermosetting composites. Most of them are used in the transport and electronics industries. New processing technologies not only improve the properties of the products but also contribute to reducing costs.

In this paper, we compare the results of mechanical tests with molded standard specimens with polypropylene matrix and test results from cut-outs from injection molded products.

Open access
The Numerical Investigation of Thin-Walled Beams with Modified C-Sections

Abstract

Demand for thin-walled structures has been increasing for many years. Cold- formed, thin-walled channel beams are the subject of presented research. The local elastic buckling and limit load of these beams subjected to pure bending are investigated. This study includes numerical investigation called the Finite Strip Method (FSM). The presented results give a deep insight into behaviour of such beams and may be used to validate analytical models. The number of works devoted to the theory of thin-walled structures has been steadily growing in recent years. It means that is an increasing interest in practical methods of manufacturing cold-formed thin-walled beams with complicated cross-sections, including also beams with web stiffeners. The ratio of transverse dimensions of beam to its wall-thickness is high, therefore, thin-walled beams are prone to local buckling that may interact with other buckling modes. The stability constraints should be always considered when using cold-formed thin-walled beams.

Open access
The Replacement of Resistance Welding with Laser Beam Welding

Abstract

Resistance welding has long been successfully used in the automotive industry, but nowadays, there are even more advanced technologies, such as laser beam welding, which is a much faster, more economical and flexible technology. During our work, we have mapped the possibility of replacing resistance welding with laser beam welding. Furthermore, we have found a solution to the problems occurring during laser beam welding. The biggest challenge in laser beam technology is that the zinc coating on the steel plates (required to prevent corrosion) evaporates during welding, resulting in pores, and leading to a significant reduction in weld strength. We have solved that by using spacer sheets, which allow the zinc vapour to escape from the keyhole.

Open access
Thermographic Inspection in the Electric Industry

Abstract

The traditional inspection of fittings used in the electrical industry is a cumbersome, dangerous process in terms of safety and operation. However, with the spread of thermography, these tests can be performed simpler, faster, and more safely through electrical connections. This article presents the possibilities, measurement difficulties and the advantages of thermography analysis [1-2].

Open access