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Role of biodestruction by microscopic fungi in change of elastic-strength properties of polymers

100%

Smirnov V. F. , Yemelyanov D. N. , Chernorukova Z. G.

2003

tom Vol. 8, no spec.

313-318

The growth of microscopic fungi on polymer materials leads to the change in physico-mechanical properties of the latter. The extent and character of the property variation are determined by qualitative and quantitative compositions of fungi metabolites taking part in the process of biodegradation. In the present work, it was ascertained that the change of mechanical and dielectric properties of polyamides, polycaproamide fibers, silicate glass threads and rubber occurs in the process of their biodestruction and under the action of individual fungi metabolites. The change in the physico-imechanical characteristics of the polymer materials takes place before the growth of microorganisms on them becomes visible. The authors offer to regard the variation of the physico-mechanical properties as a principle criterion of the resistance of various polymer materials to biodamages induced by microscopic fungi.

PTA-GMA hybrid welding of UHSS steel in structures of large-scale

100%

Nowacki J. , Krajewski S. , Matkowski P.

Archives of Materials Science and Engineering

2015

tom Vol. 71, nr 2

53--62

Purpose: An analysis of application possibilities for PTA-GMA hybrid welding in large-sized high- strength steel structures that require using particularly effective and high-performance technologies as related to quality and costs. Design/methodology/approach: Welded joints were made of S960QL steel by employing plasma and GMA hybrid welding by using various welding parameters. The tests were designed so that interrelations between particular welding technologies can be demonstrated. Macroscopic and microscopic examinations as well as hardness and tensile strength tests for welded joints were carried out. Findings: It has been shown that traditional welding methods SAW and GTA can be replaced by PTA-GMA hybrid welding. The obtained welded joints show different geometric features and hardness depending on welding technology used. Research limitations/implications: The description of welded joint structure and mechanical properties was based on welding toughened steels by using an innovative welding method and a filler that has been proposed. Practical implications: The parameters of plasma and GMA hybrid welding for industrial uses were established at the company Teleskop Sp. z o.o. The selected best welding technologies will be subject to welding procedure approval according to PN-EN 15614-1 and implemented into mass production. The information gained from toughened steel welding is an important basis for future research on metallurgical walkability by using high-performance methods of hybrid welding of large-sized structures. Originality/value: The problems associated with welding S960Q steels by using various welding technologies, including the use of an innovative GMA plasma hybrid welding method that is still at the initial stage of research work and there are no original references regarding the suitability of the a/m welding method for large-sized structures made of high-strength toughened steels were established. It has been shown that PTA-GMA hybrid welding has a significant effect on base metal structural changes resulting from a unique nature of combined heat sources of plasma and electric arc.

Welding of MART steel with the use of matching fillers

80%

Matkowski P. , Nowacki J. , Sajek A.

2014

tom Vol. 70, nr 2

77-86

Purpose: This paper attempts to determine the influence of using fillers of various kinds on strength of a welded joint of MART steel depending on the amount of heat supplied. Design/methodology/approach: Test welded joints were made of S1100QL steel with GMAW method, and using different fillers as well as different values of supplied heat. The tests were designed in such a way so as to demonstrate the prospected interdependencies as clearly as possible. Macroscopic examination was carried out, Vickers hardness, impact strength and tensile strength were measured, and technological bend test was conducted on the joint. Findings: Significant differences between the joints obtained resulting from the fillers used and welding parameters applied were noticed. The strength of a joint is lower than that of welded steel, it concentrates in the weld and is similar to the strength of parent material. Research limitations/implications: Conducting research concentrating on welding using particular filler in a wider range of heat supplied would make it possible to obtain more precise results. By delineating the interdependencies between strength parameters, it would be possible to optimise the mechanical properties of welded joints made of MART steels. It would require the employment of automated welding that allows for unrestricted and stable control of parameters. Practical implications: The conditions for making a proper joint of S1100QL steel were determined. Reasons were given for the choice of joint testing methodology and the purposefulness of comprehensive tests of joint parameters. The need for changing test procedures in order to eliminate the causes of inappropriate evaluation was manifested. The influence of automation as an important factor that determines the fulfilment of strict parameter regime of joint formation was emphasised. Determination of the interrelations between mechanical properties of a joint and welding parameters applied would allow to conduct a welding process in such a way so as to obtain a joint of desired usefulness in given technological conditions. Originality/value: Problems associated with welding of S1100QL steel with the use of filler metals of matching materials were defined and possible solutions for these problems were presented. The mechanism of welding thermal cycle influencing structural changes in the joint that result from the complex cycle of hardening and tempering was demonstrated.