Study of Mechanical Properties of Recycled Polyethylene of High and Low Density

High and low density polyethylene materials constitute about 48% of total weight of plastics waste in Europe, that depends on the frequent use of these materials in packaging applications. This paper analyze the recycling effect on the mechanical properties of high and low density polyethylene (HDPE and LDPE). A mechanical recycling process was tested for the plastics waste of high and low density polyethylene, then a tensile and impact tests were performed on different mixing ratios for each of the both materials ranging from 100% of the virgin material and up to 100% of the recycled material with a difference of 10% of the sample to the other. This paper discusses the tensile properties of tensile stress at the fracture, elongation and modulus of elasticity and the impact test results for HDPE and LDPE were compared with each other.

Enhanced Mechanical Properties and Isotropy of Mg-2Al-0.8Sn Alloy through Ca Addition

Calcium (Ca), with abundant and cheap reserves, is a potential element to facilitate the further application of Mg-Al-Sn based alloys. Here, effects of Ca content on the microstructure and tensile properties of Mg-2.0Al-0.8Sn (wt.%) alloys were systematically studied. The experimental results illustrated that the strength, ductility and isotropy of the alloys improved simultaneously with the increase of Ca content. The better ductility and isotropy could be contributed to the weakened texture via particle stimulation nucleation mechanism. The higher strength benefited from the combination of finer grains, more precipitates and residual dislocation density. Eventually, the Mg-2.0Al-0.8Sn-0.5Ca (wt.%) alloy showed the best room-temperature balance of strength and ductility with a yield strength of ∼226.0 MPa, an ultimate tensile strength of ∼282.4 MPa and a fracture elongation of ∼20.2%, which has huge potential as an applicable low-cost high-performance magnesium alloy.

Development of Fe-11Al-xMN alloy steel on cryogenic temperatures

This research is focused on increasing the reliability of Fe-11Al-Mn by combining the properties of Mn and the superiority of Fe-Al-C under cryogenic temperature. Three Fe-11Al-Mn alloys with compositions of 15 wt % Mn (F15), 20 wt % Mn (F20), and 25 wt % Mn (F25) were investigated. The cryogenic process uses liquid nitrogen in a temperature range of 0–196 °C. Hardness testing using the Vickers method and SEM was used to analyze the microstructure. X-ray diffraction (XRD) testing was conducted to ensure the Fe-11Al-Mn alloy phase and corrosion testing was carried out using the three-electrode cell polarization method. With the addition of Mn, the Vickers hardness of the Fe-11Al-Mn alloy decreased from 331.50 VHN at 15 wt % to 297.91 VHN at 25 wt %. The value of tensile strength and fracture elongation values were 742.21 MPa, 35.3 % EI; 789.03 MPa, 41.2 % EI; and 894.42 MPa, 50.2 % EI, for F15, F20, and F25, respectively. An important factor for improving the performance of cryogenic materials is the impact mechanism. The resulting impact toughness increased by 2.85 J/mm2 to 3.30 J/mm2 for F.15 and F25, respectively. The addition of the element Mn increases the corrosion resistance of the Fe-11Al-Mn alloy. The lowest corrosion rate occurs at 25 % wt Mn to 0.016 mm/year. Based on the results, the F25 alloy has the highest mechanical and corrosion resistance of the three types of alloys equivalent to SS 304 stainless steel. The microstructure of Fe-11Al-Mn alloy was similar between before and after cryogenic temperature treatment, this condition showed that the microstructure did not change during the process. From the overall results, the Fa-11Al-Mn alloy is a promising candidate for material applications working at cryogenic temperatures by optimizing the Mn content

Effect of cold rolling and ageing treatment on the interface morphology and mechanical properties of maraging steel/medium-entropy alloy multilayer composite

The cold rolling and subsequent ageing treatment of hot-rolled 18Ni300/CoCrNi multilayer composites were carried out to analyse the high work hardening ability of medium-entropy alloy (CoCrNi alloy) and the ageing precipitate strengthening effect of maraging steel (18Ni300). The results show that with the rise of cold rolling reduction, the ratio constitute layer and interface transition layer thicknesses are gradually decreased, and the interface shape changes from a flat to a wavy state, which is mainly due to the serious work hardening of the CoCrNi layer. Meanwhile, the tensile strength continuously increased. When the multilayer composite is cold-rolled to 0.5 mm, its tensile strength reaches more than 2 GPa, and the fracture elongation remains at approximately 7%. After ageing, the superior tensile strength is as high as 2825 MPa, which is attributed to the synergistic effect of work hardening, precipitation strengthening and strong interface bonding strengthening.

The Interfacial Structure and Adhesion Mechanism of N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane and Epoxy Modified Silicone Tie-Coating to Epoxy Primer

The matching application of silicone antifouling coating and epoxy primer is a major problem in engineering. Novel epoxy-modified silicone tie-coating was prepared to tie epoxy primer and silicone antifouling coating. Firstly, N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane was mechanically mixed with bisphenol A epoxy resin to form silylated epoxy resin, then the silylated epoxy resin was uniformly mixed with hydroxy-terminated polydimethylsiloxane and a curing agent and catalyst for coating. An infrared spectrometer, differential scanning calorimeter and tensile tests were used to investigate the chemical structure, phase transition temperature and mechanical properties of the tie-coatings. The interlaminar adhesion of the matching coating system was tested and analyzed by a peel-off test and a shear test. Fracture morphology was observed by scanning using an electron microscope. The results showed that crosslinking density of the tie-coating, the elastic modulus and the tensile strength of the coating increased with an increasing epoxy content, but fracture elongation decreased. The shear strength of the matching coating system is 0.37 MPa, and it shows a good tie performance. The maximum anti-peeling rate of the tie-coating on the epoxy primer reaches 100%.

Microstructure Evolution and Mechanical Properties of Mg-10.37Gd-3.66Y-2.27Zn-0.52Zr Alloy during Reciprocating Upsetting-Extrusion

The homogenized Mg-10.37Gd-3.66Y-2.27Zn-0.52Zr alloy was subjected to multi-passes reciprocating upsetting extrusion (RUE) deformation with variable temperature. The microstructure evolution and mechanical properties of as-homogenized and RUEed samples were investigated. The results showed that the area fraction of DRX grains gradually increased via the continuous consumption of coarse grains containing lamellar LPSO, and the content of the bulk LPSO phases gradually decreased due to continuous fragmentation. After three passes deformation, the microstructure was almost composed of completely DRXed grains. The LPSO phases with different morphologies were coordinated deformation by kinking, tearing, etc during RUE process. It is worth noting that after four passes, the lamellar LPSO phase did not disappear, but mixed with the fine DRXed grains together. In addition, a mass of particles were produced after each low temperature deformation, indicating that reducing the deformation temperature is beneficial to the dynamic precipitation. The yield tensile strength (TYS), Ultimate tensile strength (UTS) and fracture elongation (FE) of four passes deformed alloy reached 372.6 MPa, 320.8 MPa, 8.1%, respectively. The improvement of mechanical properties is attributed to the two main strengthening mechanisms: grain refinement and LPSO strengthening.

Failure Modes and Rules Related to the Yield-to-Tensile Strength Ratio in Steel Structures

Upper limits on the ratio of the yield strength to the tensile strength (σy/σu ratio) and lower limits on the fracture elongation εf are present in various offshore, maritime and civil engineering rules, standards and specifications for steel structures as a provision for the minimum material ductility and toughness which ensures sufficient structural ductility. In other instances, the design yield stress to be adopted in strength calculations is reduced from its nominal value if the σy/σu ratio exceeds a certain limit. Such requirements deter the use of high strength steels (nominal σy higher than 690 MPa), which inherently have a high σy/σu ratio. To guide subsequent efforts towards optimised and scientifically grounded σy/σu limits and wider application of high strength steels, this paper first presents an overview of the current provisions in engineering practice relating to the σy/σu ratio and structural ductility, and it then discusses the key underlying failure mechanisms to which these ductility requirements are relevant: tensile strain localization, yielding and localization precipitated by stress concentrations, localization of plastic bending hinges and ductile fracture. The reasoning behind the current provisions, the findings of previous research concerning the requirements, and the key potential areas for future research are highlighted.

Effect of Water-Based Emulsion Core Microcapsules on Aging Resistance and Self-Repairing Properties of Water-Based Coatings on Linden

The purpose of this paper was to discuss the best coating technology of water-based coatings containing microcapsules, and the anti-aging and self-repairing properties of water-based coatings containing microcapsules. Urea-formaldehyde encapsulated Nippon water-based emulsion microcapsules were prepared, and water-based coatings containing microcapsules were prepared. The optical and mechanical properties of the coatings under different coating technologies were investigated. Under the best coating technology, the aging resistance and self-repairing performance of the coating film were investigated. Experimental results showed that coating technology had no effect on color aberration of the coating film. The coating technology with two coats of primer, three coats of topcoat, addition of microcapsules into primer, had excellent glossiness, shock resistance of 12.0 kg·cm, adhesion of 0 grade, and fracture elongation of 26.3%. Compared with the coating film without microcapsules, the coating with microcapsules had better aging resistance and self-repairing property, and the self-repairing rate was about 20.0%. Compared with the paint film with Dulux water-based emulsion microcapsules, the paint film with Nippon water-based emulsion microcapsules had a higher self-repairing rate. This study provides a technical basis for self-repairing water-based coatings.

Effects of Partitioning Time and Temperature on the Microstructure and Mechanical Properties of a High Strength Microalloyed Steel

In the present study, in a quenching-partitioning (Q-P) process, the effects of partitioning time (Pt) and partitioning temperature (PT) on the mechanical and microstructural properties of a microalloyed Fe-0.21C-1.5Si-2.2Mn-0.054Al-0.08Ti steel were studied. The XRD and SEM results confirmed increases in retained austenite (γR) volume fraction (VγR) and (γR)carbon concentration by increasing Pt and PT. XRD patterns confirmed reduction in (VγR)by further increasing the Pt and PT over 500 sec and 390°C, respectively, due to super-saturation of austenite (γ) with carbon. PT of 390°C and Pt of 500 sec were recorded as the optimum values for PTs and Pts, which allowed the present steel to obtain higher formability and higher fracture strain characteristics, while retaining higher hardness and strength. The highest yield and tensile strength, hardness and fracture elongation were obtained for the sample partitioned at 390°C for about 500 sec, which were about 741MPa, 1366 MPa, 424 HV and 25.2 %, respectively.

Effect of ER5356 Welding Wire on Microstructure and Mechanical Properties of 5083 Aluminum Alloy GTAW Welded Joint

Automatic gas tungsten arc welding experiments of 5083 aluminum alloy were completed, to analyze the weld microstructure and mechanical properties. The influences of welding current, travel speed, frequency, and arc length on weld forming and mechanical properties were studied. When the welding current was 160 A, the travel speed was 380 mm/min, the frequency was 100 Hz, the arc length was 4 mm, and the maximum tensile strength of the welded joint was 296.9 MPa, which was 86.8% of the base metal’s tensile strength. The fracture elongation was 7.8%. No porosity was formed in the weld, but there were poor fusion problems. ER5356 welding wire can improve the problem of poor weld fusion and accommodate Mg element vaporization losses. When the wire feeding speed was 1200 mm/min, the tensile strength of the welded joint can be improved to 315.2 MPa, which was 92.2% of the base material’s tensile strength, and the fracture elongation was 8.5%. The tensile specimens fractured in the heat-affected zone. The fracture surface was characterized as plastic fracture.