Use of composite materials has seen significant growth, especially in the manufacture of lightweight structures and biomedical applications. One type of composite material is made up of polymer materials reinforced with glass fibres. PA6-GF reinforced with 25 % chopped glass fibres is a representative of this composite material group. The manufacturer recommends annealing as a heat treatment process after production. However, annealing requires additional equipment and time. This paper seeks to investigate the effect of non-annealed PA6 GF on the Charpy impact properties. Samples for Charpy impact property tests are defined according to BAS EN ISO 179-2:2021. The test specimens were printed on the FlashForge Creator 3 PRO printer, and the testing was performed on the AMSLER RPK300 device.

The application of conventional electric arc welding in argon protection (TIG welding process) has limited possibilities. These limitations are primarily related to the thickness of the welded material and the need to prepare the groove for their welding. Overcoming these limitations in TIG welding was done by using activating flux, so the procedure was named ATIG (A-TIG) welding. The paper presents the results of research into the application of activating fluxes in welding austenitic stainless steel 316L with a thickness of 6 mm. By using the BC-31 and QuickTIG melters of different chemical bases, we compare the mechanical properties of the welded joints, as well as with the welded joints of the same material obtained using the conventional TIG procedure. The results show that the best mechanical properties are possessed by welded joints realized by the ATIG process using a mixture of activating fluxes BC - 31 (50%) and QuickTIG (50%) (green + white flux).

Polymers and polymer composite materials, due to their properties, are becoming increasingly important materials in industry. They are used in a wide range of applications in space and aerospace, aviation, marine and automotive industry, as well as in production of sports equipment, household appliances, medical equipment, etc. They are expected to withstand loads during their lifetime, which requires predicting the reliability of structural elements, i.e. knowledge of material properties. To achieve better properties, polymer materials are reinforced with different percentages of fibre-reinforced materials, including glass fibres. The paper presents the results of experimental determination of the mechanical properties of injection moulded PA6 polymer reinforced with 30% glass fibres, determined by tensile and impact tests.

Welded structures place increasing demands on the level of increased resistance to fracture. A large number of fractures of welded structures, which occur during exploitation at a stress level below of the allowable, indicates the danger of brittle fracture. The assessment of brittle fracture susceptibility was analyzed by testing Sharpy specimens, and the total impact energy, components of total impact energy (crack energy initiation and crack energy propagation) were used as parameters in the analysis.

A very important segment, which occurs as a result of welding, is the occurrence of residual stresses in welded structures. The effects of residual stresses can be beneficial or harmful to the structure, depending on their size, sign, and stress distribution in relation to the stresses caused by the external load itself. Therefore, the examination of residual stresses is very important because they significantly affect the formation and growth of cracks, the appearance of brittle fractures, material fatigue, etc. The paper presents the test procedure for measuring residual stresses by the method of "hole drilling" and the possibility of practical application of knowledge about residual stresses in order to improve the quality of machine parts and the structure itself.

The largest number of welded structures in operating conditions is exposed to variable loads, which is why the share of fatigue fracture in the failure of welded structures is higher than others. The essence of construction with fracture safety is that the structure can withstand the designed load in the designed time. If a crack is detected during operation, it is possible to predict the development of damage during the service life as well as the load-bearing capacity of the structure depending on the development of damage. The paper describes a new system for monitoring fatigue crack growth, which is based on the change in the resistance of the measuring foil during crack growth. The system is compatible with the basic settings of the ASTM E647–86 standard, which refers to the determination of the fatigue crack growth rate.

A large number of cracking the conveyor belt, which occurs during exploitation at stress level lower than the permitted, indicates a risk of damage and breakage. Therefore in designing it is necessary to define criteria by which one can achieve safety of exploitation conveyors with rubber belt from damage and breakage. In this analysis it is very important to treat the rubber conveyor belt as a classical composite material, which consists of a rubber as a matrix and a polyesterpolyamide canvas as reinforcements. Rating of mechanical and exploitation properties, i.e. the emergence and development of damage in composite materials due to the static and dynamic loads is complex phenomenon’s which consist: micro cracks in the rubber, a breakage of fiber of polyester-polyamide canvas, weakening of connection rubber-canvas and delamination. In this paper is presented the results of experimental studies of composite materials the rubber conveyor belt with cartridges made of polyester and polyamide. It is also presented the results of a new and exploited rubber conveyor belts in the direction of the load action, as follows: tensile strength, modulus of elasticity, Poisson's coefficient and strain.

ABSTRACT: In this paper will be showed process planning using web design. All elements will represent participation in forming knowledge base for process planning of class rotational parts. CAPP system will show method for representation knowledge using object-oriented programming. Web technolgy will be used for connection between CAPP system and users of technologies. Proposed methodology will use an object-oriented method for the generative process planning in order to shorten the time.

The in-service behaviour of alloyed steel A-387 Gr. 11 Class 1, for pressure vessels, used for high temperature applications, depends on the properties of its welded joint, with parent metal (BM), heat-affected-zone (HAZ) and weld metal (WM) as constituents. Charpy testing of BM, WM and HAZ, together with determination of the parameters of fatigue-crack growth and fatigue threshold Delta_Kth was used, in order to understand, how heterogeneity of structure and different mechanical properties of welded joint constituents affects on crack initiation and propagation.

The effect of glass fibre orientation in an epoxy matrix composite on impact load and fracture toughness is experimentally analysed by testing Charpy V notched specimens, and notched CT specimens. Specimens are produced from samples with glass fibre orientation 454s, and 0/904s. Specimens with V notch have been tested on instrumented Charpy machine, enabling to separate energies for crack initiation and crack propagation. The stress intensity factor Kc is selected as the fracture toughness parameter. Ključne reči • kompozit • staklena vlakna • epoksi smola • orijentacija vlakna • ispitivanje udarom • faktor intenziteta napona

The effect of vibration on the variation of residual stresses in butt-welded steel plates and on the impact energy in characteristic zones of a welded joint is analysed in this paper. An important segment occurring as a result of welding is the phenomenon of residual stresses in the welded joint zone. Residual stress measurements are conducted both on butt-welded plates that were not vibrated during welding and on plates simultaneously welded and vibrated. It is concluded that the vibration process noticeably decreases the level of stresses in the zone of the butt weld, i.e. the result is relaxation and plane stress state. Impact energy tests have shown that vibration favourably affects the total impact energy by increasing it both in specimens notched in the weld metal (WM) and in the heat-affected zone (HAZ). It is also concluded that the correlation between the distribution of crack initiationand crack propagation energy, as vital components in the assessment of welded joint ductility, is improved. Ključne reči • zavarivanje • zaostali naponi • vibracije • energija udara

An investigation has been carried out into the behaviour of type IV cracks region in heat affected zone (HAZ) of P91 steel at 600°C. Microstructure zones where type IV failures may occur have been studied in details. Results are reported on the simulated specimens 11x11x70 mm tested at operating temperature. The results of comparison of mechanical characteristics and microstructure have been analysed using two types of specimens: with postweld heat treatment (PWHT) and without PWHT. It has been found the presence of precipitates at the grain boundaries in simulated type IV zone of HAZ exposed to subsequent PWHT.