scholarly journals Ductility and Seismic Suitability of Locally Sourced High Yield Rebars in Benin City

2020 ◽  
Vol 4 (2) ◽  
pp. 458-462
Author(s):  
E. Nwankwo ◽  
E. Attama
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Tensile Force ◽  
Tensile Tests ◽  
High Yield ◽  
Damping Capacity ◽  
Eurocode 8 ◽  
Deformation Capacity ◽  
Benin City ◽  
Energy Absorbing

Ductility is the ability of a system to sustain large deformations beyond its yield point without breaking or failing. Eurocode 8 makes allowance for receipt of seismic forces using the damping capacity of ductile members. This allows for the absorption of energy and helps increase the amount of energy absorbed by ductile structures before failure. This paper investigates the maximum ductility locally sourced steel rebars in Benin City structure can sustain without damage by establishing parameters that influence ductility. Tensile tests were conducted for rebar sizes of 10 mm, 12 mm, and 16 mm diameters, which were sourced from three different vendors within Benin City, Nigeria. The strain-hardening ratio Stu/Sty, i.e. the ratio of tensile strength Stu to yield strength Sty, and the elongation at maximum tensile force Agt were investigated in order to determine plastic deformation capacity and the degree of ductility of these rebars. A numerical model – the modified Ramberg- Osgood and Rasmussen equations – was modified in order to predict the experimentally obtained ductility parameters of these locally sourced rebars. The model collaborates well with experiments and could be used to establish ductility parameters of local rebars. Also, ductility test results showed that strain hardening ratios and elongation were relatively low (Recommended strain hardening ratio of rebar for seismic design is 1.15) and this could result in reinforced concrete structures made with these rebar exhibiting moderate ductility, i.e. a moderate plastic deformation capacity which might not have sufficient energy absorbing capacity in events of large earthquakes.

scholarly journals Chemical and physical interactions of regenerated cellulose yarns and isocyanate-based matrix systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bernhard Ungerer ◽  
Ulrich Müller ◽  
Antje Potthast ◽  
Enrique Herrero Acero ◽  
Stefan Veigel
Keyword(s):  
Mechanical Performance ◽  
Tensile Force ◽  
Tensile Modulus ◽  
Tensile Tests ◽  
Size Exclusion ◽  
Regenerated Cellulose ◽  
Hydrolytic Cleavage ◽  
Yarn Twist ◽  
Exclusion Chromatography ◽  
Physical And Chemical

AbstractIn the development of structural composites based on regenerated cellulose filaments, the physical and chemical interactions at the fibre-matrix interphase need to be fully understood. In the present study, continuous yarns and filaments of viscose (rayon) were treated with either polymeric diphenylmethane diisocyanate (pMDI) or a pMDI-based hardener for polyurethane resins. The effect of isocyanate treatment on mechanical yarn properties was evaluated in tensile tests. A significant decrease in tensile modulus, tensile force and elongation at break was found for treated samples. As revealed by size exclusion chromatography, isocyanate treatment resulted in a significantly reduced molecular weight of cellulose, presumably owing to hydrolytic cleavage caused by hydrochloric acid occurring as an impurity in pMDI. Yarn twist, fibre moisture content and, most significantly, the chemical composition of the isocyanate matrix were identified as critical process parameters strongly affecting the extent of reduction in mechanical performance. To cope with the problem of degradative reactions an additional step using calcium carbonate to trap hydrogen ions is proposed.

scholarly journals Influence of Hydrostatic Extrusion on the Mechanical Properties of the Model Al-Mg Alloys

2021 ◽  
Author(s):  
Aleksandra Towarek ◽  
Wojciech Jurczak ◽  
Joanna Zdunek ◽  
Mariusz Kulczyk ◽  
Jarosław Mizera
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Tensile Strength ◽  
Microstructural Analysis ◽  
Tensile Tests ◽  
Hydrostatic Extrusion ◽  
Microstructure Formation ◽  
Initial State ◽  
Degree Of Deformation ◽  
Al Mg Alloys

AbstractTwo model aluminium-magnesium alloys, containing 3 and 7.5 wt.% of Mg, were subjected to plastic deformation by means of hydrostatic extrusion (HE). Two degrees of deformation were imposed by two subsequent reductions of the diameter. Microstructural analysis and tensile tests of the materials in the initial state and after deformation were performed. For both materials, HE extrusion resulted in the deformation of the microstructure—formation of the un-equilibrium grain boundaries and partition of the grains. What is more, HE resulted in a significant increase of tensile strength and decrease of the elongation, mostly after the first degree of deformation.

Behavior Factor of Dual Systems with BRBs and Semi-Rigid Connections

2018 ◽  
Vol 763 ◽  
pp. 949-956 ◽  
Author(s):  
Francesca Barbagallo ◽  
Melina Bosco ◽  
Edoardo Michele Marino ◽  
Pier Paolo Rossi
Keyword(s):  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Design Procedure ◽  
Eurocode 8 ◽  
Deformation Capacity ◽  
Structural System ◽  
Dual Systems ◽  
Behavior Factor ◽  
Soft Story ◽  
Collapse Mechanisms

The use of BRBs into a typical European building with braced structure, whereby all the beam-to-column connections are perfectly pinned, may be low effective. In fact, these structures are low-redundant and prone to develop soft story collapse mechanisms. The concentration of drift demand in few stories precludes the full exploitation of the deformation capacity of all the BRBs inserted into the frame, and it partially reduces the benefit they can provide. A more effective structural system may be obtained by coupling frames with BRBs with frames with semi-rigid connections. This paper proposes a design procedure for this dual system and presents the calibration of the behavior factor. To this end, a set of frames is designed considering several values of behavior factor and the response of the obtained frames is determined by nonlinear dynamic analysis. Hence, the behavior factor that allows the frames to meet the performance objective requirement of EuroCode 8 is determined.

The Effect of Plastic Deformation on the Thermoelastic Constant and the Potential to Evaluate Residual Stress

2011 ◽  
Vol 70 ◽  
pp. 458-463 ◽  
Author(s):  
A. F. Robinson ◽  
Janice M. Dulieu-Barton ◽  
S. Quinn ◽  
R. L. Burguete
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Thermoelastic Stress ◽  
Paint Coating ◽  
Full Field ◽  
Thermoelastic Constant ◽  
Thermoelastic Response ◽  
Measured Change

In some metals it has been shown that the introduction of plastic deformation or strain modifies the thermoelastic constant, K. If it was possible to define the magnitude of the change in thermoelastic constant over a range of plastic strain, then the plastic strain that a material has experienced could be established based on a measured change in the thermoelastic constant. This variation of the thermoelastic constant and the ability to estimate the plastic strain that has been experienced, has potential to form the basis of a novel non-destructive, non-contact, full-field technique for residual stress assessment using thermoelastic stress analysis (TSA). Recent research has suggested that the change in thermoelastic constant is related to the material dislocation that occurs during strain hardening, and thus the change in K for a material that does not strain harden would be significantly less than for a material that does. In the work described in this paper, the change in thermoelastic constant for three materials (316L stainless steel, AA2024 and AA7085) with different strain hardening characteristics is investigated. As the change in thermoelastic response due to plastic strain is small, and metallic specimens require a paint coating for TSA, the effects of the paint coating and other test factors on the thermoelastic response have been considered.

Influence of Severe Plastic Deformation on the PLC Effect and Mechanical Properties in Al 5XXX Alloy

2006 ◽  
Vol 114 ◽  
pp. 171-176 ◽  
Author(s):  
Joanna Zdunek ◽  
Pawel Widlicki ◽  
Halina Garbacz ◽  
Jaroslaw Mizera ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
True Strain ◽  
Tensile Tests ◽  
Size Reduction ◽  
Hydrostatic Extrusion ◽  
Stress Strain ◽  
Chatelier Effect

In this work, Al-Mg-Mn-Si alloy (5483) in the as-received and severe plastically deformed states was used. Plastic deformation was carried out by hydrostatic extrusion, and three different true strain values were applied 1.4, 2.8 and 3.8. All specimens were subjected to tensile tests and microhardness measurements. The investigated material revealed an instability during plastic deformation in the form of serration on the stress-strain curves, the so called Portevin-Le Chatelier effect It was shown that grain size reduction effected the character of the instability.

scholarly journals HYSTERETIC CHARACTERISTICS AND PLASTIC DEFORMATION CAPACITY OF UPLIFT YIELDING BASE-PLATES FOR CONTROLLED ROCKING FRAMES

2010 ◽  
Vol 75 (652) ◽  
pp. 1159-1166 ◽  
Author(s):  
Mitsumasa MIDORIKAWA ◽  
Tatsuya HASEGAWA ◽  
Tadashi ISHIHARA ◽  
Tatsuya AZUHATA ◽  
Tetsuhiro ASARI
Keyword(s):  
Plastic Deformation ◽  
Deformation Capacity ◽  
Hysteretic Characteristics ◽  
Base Plates

Interface Engineering of CNT/Polymer Nanocomposites With Tunable Damping Properties

2018 ◽  
Author(s):  
Michela Talò ◽  
Giulia Lanzara ◽  
Maryam Karimzadeh ◽  
Walter Lacarbonara
Keyword(s):  
Load Transfer ◽  
Mechanical Response ◽  
Material Design ◽  
Tensile Tests ◽  
Nanocomposite Films ◽  
Damping Capacity ◽  
Interfacial Region ◽  
Material Damping ◽  
Stick Slip ◽  
Multi Walled Carbon Nanotubes

In this work, the arising of stick-slip dissipation as well as the global mechanical response of carbon nanotube (CNT) nanocomposite films are tailored by exploiting a three-phase nanocomposite. The three phases are represented by the CNTs, a polymer coating localized on the CNTs surface and a hosting matrix. In particular, a polystyrene (PS) layer coats multi-walled carbon nanotubes (MWNTs) that are randomly dispersed in a polyimide (PI) matrix. The coating phase is strongly bonded to the CNTs outer sidewalls ensuring the effectiveness of the load transfer mechanism and reducing the material damping capacity. The coating phase can be thermally-activated to modify, and in particular, decrease the CNT-matrix interfacial shear strength (ISS) thus facilitating the stick-slip onset in the nanocomposite. The ISS decrease finds its roots in a partial degradation of the coating phase and, in particular, in the formation of voids. By weakening the CNT/polymer interfacial region, a significant enhancement in the material damping capacity is observed. An extensive experimental campaign consisting of monotonic and cyclic tensile tests proved the effectiveness of this novel multi-phase material design.

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