Tensile Strength, Elongation and Flow Stress of Aluminum-Magnesium Alloys under Dynamic Loading

A multifactor mathematical model of the welding process of products from aluminum-magnesium alloys, consisting of 71 indicators that assess the quality of the weld, the welding process, costs, equipment operation and quality of the welded material. The model can be used to control and optimize the welding process of products from aluminum-magnesium alloys. Keywords welding, products, aluminum-magnesium alloy, indicators, process parameters, welding equipment, welding materials, electrode sharpening, lining [email protected]

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Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽

10.3390/ma14040722 ◽

2021 ◽

Vol 14 (4) ◽

pp. 722

Author(s):

Enrico Wölfel ◽

Harald Brünig ◽

Iurie Curosu ◽

Viktor Mechtcherine ◽

Christina Scheffler

Keyword(s):

Tensile Strength ◽

Dynamic Loading ◽

Melt Spinning ◽

Structural Changes ◽

High Surface ◽

Single Fiber ◽

Scanning Calorimetry ◽

Matrix Interaction ◽

Pull Out ◽

Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

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Rejuvenation Mechanism of Asphalt Mixtures Modified with Crumb Rubber

CivilEng ◽

10.3390/civileng2020020 ◽

2021 ◽

Vol 2 (2) ◽

pp. 370-384

Author(s):

Hossein Noorvand ◽

Kamil Kaloush ◽

Jose Medina ◽

Shane Underwood

Keyword(s):

Tensile Strength ◽

Dynamic Loading ◽

Creep Compliance ◽

Asphalt Mixture ◽

Crumb Rubber ◽

Indirect Tensile Strength ◽

Laboratory Evaluation ◽

Strength Testing ◽

Noise Mitigation ◽

Indirect Tensile

Asphalt aging is one of the main factors causing asphalt pavements deterioration. Previous studies reported on some aging benefits of asphalt rubber mixtures through laboratory evaluation. A field observation of various pavement sections of crumb rubber modified asphalt friction courses (ARFC) in the Phoenix, Arizona area indicated an interesting pattern of transverse/reflective cracking. These ARFC courses were placed several years ago on existing jointed plain concrete pavements for highway noise mitigation. Over the years, the shoulders had very noticeable and extensive cracking over the joints; however, the driving lanes of the pavement showed less cracking formation in severity and extent. The issue with this phenomenon is that widely adopted theories that stem from continuum mechanics of materials and layered mechanics of pavement systems cannot directly explain this phenomenon. One hypothesis could be that traffic loads continually manipulate the pavement over time, which causes some maltenes (oils and resins) compounds absorbed in the crumb rubber particles to migrate out leading to rejuvenation of the mastic in the asphalt mixture. To investigate the validity of such a hypothesis, an experimental laboratory testing was undertaken to condition samples with and without dynamic loads at high temperatures. This was followed by creep compliance and indirect tensile strength testing. The results showed the higher creep for samples aged with dynamic loading compared to those aged without loading. Higher creep compliance was attributed to higher flexibility of samples due to the rejuvenation of the maltenes. This was also supported by the higher fracture energy results obtained for samples conditioned with dynamic loading from indirect tensile strength testing.

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Microstructure and Mechanical Properties of Dissimilar Friction Welding Ti-6Al-4V Alloy to Nitinol

Metals ◽

10.3390/met11010109 ◽

2021 ◽

Vol 11 (1) ◽

pp. 109

Author(s):

Ateekh Ur Rehman ◽

Nagumothu Kishore Babu ◽

Mahesh Kumar Talari ◽

Yusuf Siraj Usmani ◽

Hisham Al-Khalefah

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Flow Stress ◽

Intermetallic Compound ◽

Ultimate Tensile Strength ◽

Friction Welding ◽

Welding Process ◽

Weld Interface ◽

Dissimilar Joints ◽

Dissimilar Alloys

In the present study, a friction welding process was adopted to join dissimilar alloys of Ti-Al-4V to Nitinol. The effect of friction welding on the evolution of welded macro and microstructures and their hardnesses and tensile properties were studied and discussed in detail. The macrostructure of Ti-6Al-4V and Nitinol dissimilar joints revealed flash formation on the Ti-6Al-4V side due to a reduction in flow stress at high temperatures during friction welding. The optical microstructures revealed fine grains near the Ti-6Al-4V interface due to dynamic recrystallization and strain hardening effects. In contrast, the area nearer to the nitinol interface did not show any grain refinement. This study reveals that the formation of an intermetallic compound (Ti2Ni) at the weld interface resulted in poor ultimate tensile strength (UTS) and elongation values. All tensile specimens failed at the weld interface due to the formation of intermetallic compounds.

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