IMPROVEMENT OF THE MECHANICAL PROPERTIES OF MOBILE PLATFORM STAINLESS CONSTRUCTION ELEMENTS

Stainless steel could be treated as the main material used to construct various means of transport, including mobile platforms and tank trucks. An austenitic steel known as 316L steel (1.4401) has high resistance to atmospheric corrosion, natural waters, water vapor, alkaline solutions, and acids, even at elevated temperatures. This steel is weldable, although it is also prone to various types of welding cracks. Many factors influence the quality and mechanical properties of a joint. The most significant of these is the appropriate selection of welding parameters, which should be determined precisely and separately for each type of sheet, depending on its thickness and geometric features. The aim of the present article is to study the influence of main TIG (Tungsten inert gas) welding parameters on the creation of proper joints used in the construction of mobile truck platforms or tank trucks. The proper selection of parameters enables the production of welds with good functional properties. A novelty of this article is the proposal to weld each layer of a thick joint with different parameters, which has an important influence on the mechanical properties of the joint. It is expected that the new material and technological solution will yield a joint with good corrosion resistance and increased mechanical properties. This is important in the responsible construction of means of transport, using the example of mobile platforms and tank trucks. Different tests verifying the properties of joints, including non-destructive testing, tensile strength tests, and fatigue tests, as well as a hardness probe, were applied

IMPACT ANALYSIS OF MICRO-JET COOLING FOR STRESS CONCENTRATION IN A CRANE BUMPER DURING A COLLISION

In the structure of crane bumpers, there is a need to join various types of steel. Usually, low-alloy steel structures are used for this purpose, which can be represented by S355J2 steel. The tensile strength of S355J2 low-alloy steel is slightly below 600 MPa, and the tensile strength of S355J2 steel is at the high level of 200 J at ambient temperature. The impact strength of this steel in negative temperatures is also good at over 47 J at -60 °C, so it meets the 6th class of impact toughness. Welding structures, after classic gas metal arc welding (GMAW) processes, meet only the second impact toughness class. An improved GMAW process was used by micro-jet cooling application to raise the mechanical properties of the joints. The microstructure and main properties of the joints were carefully analyzed. The influence of using the new suggested welding process on the various properties of the welds is presented (UTS – ultimate tensile strength, YS – yield strength, Poisson ratio, elongation, Young’s modulus). Then, the effects of tests for use in crane bumper construction were checked by using a hybrid finite element method (FEM) analysis

Manufacturing and characterization of epoxy resin with Fe3O4 and SiO2 particles

Thermosetting polymers are very popular in the automotive and aeronautic industry, in particular epoxy resin is widely used as matrix thermoset in carbon and glass  fibre reinforced composites. The properties of these epoxy-based polymers can be improved with the addition of particulate or small fibre materials in order to construct a lightweight material with enhanced mechanical and structural response. This work aimed to manufacture and characterize epoxy resin reinforced composites with iron (II, III) oxide (magnetite, Fe3O4) in amounts of 0.25, 0.5 and 1 wt%, and 2 and 4 wt% of fumed silicon dioxide (silica, SiO2). Mechanical properties were investigated by three-point bending flexural test, fracture toughness, flexural stress relaxation. In addition, apparent porosity, apparent density and Differential Scanning Calorimetry tests were performed. The results showed that the addition of Fe3O4 does not contribute significantly to the improvement of mechanical properties. However, fumed SiO2 promotes a considerable improvement in the mechanical properties.   Keywords: Composite, epoxy resin, Fe3O4, SiO2, mechanical propertie

ABRASIVE WEAR RESISTANCE OF FE3AL AND STELLITE 6 COATINGS FOR THE PROTECTION OF VALVE SEATS SURFACES

The development of a technology that increases the service life of valve seats in CNG/LNG-powered vehicles requires the appropriate selection of material and the technology of its application. Commercially used valve seat materials show accelerated wear under operating conditions, especially in natural gas vehicle engines. The authors developed a new material concept and a new technological concept for the protection of the valve seat in CNG/LNG-powered vehicles. This article aims to present the first stage of tribological research. Two materials were used in the research: Stellite 6 alloy and Fe3Al intermetal. A commonly used material for valve seats of combustion engines is Stellite 6. The Fe3Al is the new proposed material coating for the protection of the valve seats of internal combustion engines. This article compares the abrasive wear resistance of these materials. The abrasion tests were performed on a T-11 pin-on-disc tester, and the counter-sample was steel S235JR. The test conditions were similar to those prevailing during the operation of the valves in the head of the internal combustion engine, without the influence of temperature. The obtained results indicate that the Fe3Al intermetal is characterized by a lower coefficient of friction and lower wear intensity than Stellite 6. The results confirm that the Fe3Al phase is a prospective material to be used as a protective material on the valve seat of vehicles

Steel Weld Metal Deposit Measured Properties after Immediate Micro-Jet Cooling

The aim of this paper is to present a welding process connected with micro-jet cooling. This method allowed us to guide the metallographic structure, and furthermore, the properties of the weld metal deposit. The main conclusion of this paper was that after welding with micro-jet cooling, it was possible to achieve beneficial metallographic structures that are impossible to obtain in any other way. These structures corresponded to very good mechanical properties of the welds. The research results described the influence of an artificially enhanced amount of acicular ferrite in the weld metal deposit (WMD) even above 65% when using micro-jet cooling. The results of this process were very positive due to the very high impact toughness of welds at negative temperature. The main parameters of micro-jet cooling are: cooling stream diameter (about 60 µm), gas pressure (about 0.6 MPa), the use of various gases and gas mixtures (main micro-jet gases: argon, helium, nitrogen, carbon dioxide, oxygen, air)