Wyniki wyszukiwania - BazTech

1

Effect of various temperatures and strain-rates combinations on the thermomechanical behavior of 42CrMo steel

Abdul-Latif A., Abed F., Oucif Ch., Voyiadjis G. Z.

Archives of Mechanics

|

2022

|

Vol. 74, nr 5

345–-372

EN

This paper investigates experimentally the thermomechanical response of 42CrMo steel under several combinations of temperatures and strain-rate. To characterize the flow stress of this highstrength 42CrMo steel, two distinct test configurations were utilized. The first consisted of conventional uniaxial tensile tests conducted at room and elevated temperatures of 523◦K, 723◦K and 923◦K and three quasi-static strain-rates at 0.0015 s−1, 0.015 s−1, and 0.15 s−1. The second test configuration was carried out under dynamic compression using a drop mass bench at room temperature with three different dynamic strain-rates of 300 s−1, 400 s−1, and 500 s−1. Particular attention was paid to key features such as work-hardening (WH), grain size, dynamic strain aging (DSA), formation of microcavities, and their coupling with the influence of temperature/strain-rate combination. The dependence of 42CrMo steels’ flow stress on the quasi-static strain-rate at room temperature was almost insignificant. However, the strain-rate sensitivity increased with increasing temperatures. At high temperatures, different factors contributed to modifying the alloy microstructure which has a significant impact on the alloy’s mechanical properties. Quantification of the micro-cracks density and fractured specimens’ voids was established using scanning electron microscopy (SEM) images. The Voyiadjis–Abed (VA) constitutive model was utilized in describing the flow stress of 42CrMo steels and implemented in the ABAQUS software to develop a robust finite element model capable of accurately simulating variant structural responses of 42CrMo steel alloy.

2

Preparation of a new AAC-concrete sandwich block and its compressive behavior at quasi-static loading

Abed F., Aidan A., Hegazi N., Ibrahim N., Al-Dabagh S.

Engineering Transactions

|

2017

|

Vol. 65, iss. 2

371--389

EN

Autoclaved aerated concrete (AAC) is an environmentally friendly material that has several advantages such as heat insulation, sound insulation, and light weight which reduce the energy consumption of a structure during its construction and when using it. However, the compressive strength of AAC is relatively low in comparison with concrete masonry units that are used as building blocks. This paper provides insight into a newly proposed AAC-concrete sandwich composite. The main aim of this research is to produce a lightweight eco-friendly loadbearing building block. Construction and demolition wastes including the cement and fine powder waste were utilized to generate the AAC-concrete composite. The proposed sandwich composite was tested in a number of stages. Firstly, a preliminary test was conducted to test the proposed sandwiching technique. Three sets of plain sandwich specimens were prepared, each with a different combination of AAC thickness and concrete thickness. It was found that the proposed composite had a higher compressive strength than AAC and a lower density than the normal concrete. Secondly, different concrete and mortar mixes were prepared and studied to identify the mix that would yield the best sandwich composite. This best mix was identified and used throughout the experiment. Thirdly, different sandwiching techniques were applied to enhance bonding at the AAC-concrete interface. The proposed sandwiching techniques were as follows: (1) inserting grooves at the AAC-concrete interface and (2) wrapping the AAC block with wire mesh. Multiple cube specimens with 10 cm side length were prepared and tested for their compressive strength. It was found that the wire mesh provided a more effective bonding. Finally, additional grooved and plain sandwich cube specimens with 20 cm side length were prepared and tested under different quasi-static loading rates. Unlike plain sandwich block, the compressive behavior of grooved sandwich showed a slight increase in its capacity at higher quasi-static rate. Almost all specimens in this study failed in a similar manner that is, by debonding at the AAC-concrete interface, followed by crushing.

3

Experimental and Numerical Investigation on Compression Orthotropic Properties of Spruce Wood in Axial and Transverse Loading Directions

Zhong W, Rusinek A., Jankowiak T., Huang X., Abed F.

Engineering Transactions

|

2014

|

Vol. 62, iss. 4

381–-401

EN

Compression tests on spruce wood in axial, radial and tangential directions have been performed using an INSTRON hydraulic machine. Spruce elastic mechanical properties and plastic deformation behaviour are presented. Experimental results allow to demonstrate different spruce failure modes: fibers buckling and collapsing are noticed under axial compression whereas, fibers slippage and delamination are the main failure modes under compression loading in radial and tangential directions. Spruce energy absorption efficiency and ideality energy absorption efficiency in the three loading directions are also analyzed. Representative volume element (RVE) model is adopted assuming transverse isotropic behavior to simulate wood microstructure in all directions. It was shown that micro-cell arrangement leads to wood macromechanical property spatial anisotropy. Porosity and hole shape effects on simulation results are estimated by RVE models with hexagon, circle, pentagon and square holes.