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Mechanical and Microstructural Characterization of Aluminium Alloy, EN AC-Al Si12CuNiMg

Sirata Gotfila G., Wacławiak K., Dyzia Maciej

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 3

34--40

EN

the manufacture of mechanical structures where low weight is critical. However, when these alloys are subjected to elevated temperatures, their mechanical properties deteriorate significantly. The aim of this study is to investigate the effect of temperature on the mechanical properties of aluminium alloy, EN AC-Al Si12CuNiMg. For this purpose, an experimental investigation was performed at ambient and elevated temperatures on aluminium alloy samples prepared by casting. Tensile and hardness tests were carried out to characterize the mechanical properties of this material. Additionally, an optical microscope was used to examine the microstructures of this alloy. Finally, a scanning electron microscope was used to analyze the fracture modes of this material. The results show that the mechanical properties such as tensile strength, yield strength, and Young's modulus of this alloy dramatically decrease when the temperature exceeds 250oC. The microstructural investigation reveals several factors that are detrimental to the mechanical properties of this alloy. This includes coarse-grained structures, micro-pores, and several intermetallic compounds. Furthermore, fractography reveals a minor cleavage-like pattern and micro-cracks on the fracture surface of all failed samples under various temperatures, indicating semi-brittle fracture mode.

2

Stimulated autogenous-healing capacity of fiber-reinforced mortar incorporating healing agents for recovery against fracture and mechanical properties

Buller Abdul Salam, Abro Fahad-ul-Rehman, Ali Tariq, Jakhrani Sadam Hussain, Buller Abdul Hafeez, Ul-Abdin Zain

Materials Science Poland

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2021

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Vol. 39, No. 1

33--48

EN

This study aimed to investigate the effect of autogenous healing capacity with the addition of expansive and crystalline agents on mechanical and fracture behaviors of fiber-reinforced (FR) mortar specimens with crack mouth opening displacement (CMOD) controlled test set-up. The experimental results of a self-healing approach of FR mortar were analyzed in terms of first cracking peak load (FCPL) increase, index of fracture toughness recovery (IFTR), and index of fracture energy recovery (IFER). Initially, the specimens were pre-cracked at different crack widths ranging from 30 μm to 200 μm after 28-days of curing. After pre-cracking, the specimens were kept in water for 56- and 120-day healing. A controlled three-point bending test (PBT) was applied on prism specimen having a central notch of 40 mm depth for pre-cracking as well as the post-conditioning stage for determining the FCPL. However, the crack surfaces were monitored by a high-range digital microscope and scanning electron microscope (SEM) to examine the nature of healed products near the damaged area. Test results revealed that a significant recovery of small cracks (≤50 μm) could be achieved for self-healing specimens by using healing agents (HA), while for large cracks (≥100 μm) partial recovery could be achieved after the 120-day healing period.

3

Thermal fracture characteristics of an interface crack subjected to temperature variations

Kalinović Saša M., Djoković Jelena M., Nikolić Ružica R., Hadzima Branislav

Production Engineering Archives

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2020

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Vol. 26, Iss. 2

54--59

EN

Thermal fracture characteristics - the thermal energy release rate and thermal stress intensity factor of a semi-infinite crack at an interface between the two elastic isotropic materials, subjected to the temperature variations, are considered in this paper. Those characteristics are determined based on application of the linear elastic fracture mechanics (LEFM) concept. Expressions for obtained theoretical solutions are compared to solutions from literature and they are found to be more concise. Influence of the materials change on these two thermal fracture properties were observed, as well as the influence of the thickness ratio of the two layers constituting the interface.

4

Perforation test as an accuracy evaluation tool for a constitutive model of austenitic steel

Moćko W., Kowalewski Z. L.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 4

1105--1110

EN

In this paper, a new method for assessing the accuracy of a constitutive model is proposed. The method uses perforation test done by drop weight tower. The assessment is carried out by comparison of striker velocity curve obtained using experiment and FEM simulation. In order to validate proposed method the various constitutive equations were applied i.e. Johnson-Cook, Zerilli-Armstrong and the extended Rusinek-Klepaczko to model mechanical behaviour of X4CrMnN16-12 austenitic steel. The steel was characterized at wide range of strain and strain rates using servo-hydraulic testing machine and split Hopkinson pressure bar. The relative error calculated as a difference between measured and constitutive model based stress-strain curve was applied as a reference data (classic approach). Subsequently, it was compared with relative error determined on the basis of experimental and FEM calculated striker velocity (new approach). A good correlation between classic and a new method was found. Moreover, a new method of error assessment enables to validate constitutive equation in a wide range of strain rates and temperatures on the basis of a single experiment.

PL

W artykule zaprezentowano nową metodę oceny dokładności modelu konstytutywnego. Oparto ją na wynikach uzyskanych w próbie przebijania z użyciem młota opadowego. Wyznaczenie błędu zostało przeprowadzone na podstawie porównania prędkości penetratora zmierzonej w trakcie ekspery mentu i obliczonej na podstawie symulacji MES. W celu walidacji metody przeanalizowano wybrane równania konstytutywne: Johnsona-Cooka, Zerilli-Armstronga oraz rozszerzony model Rusinka-Klepaczko w odniesieniu do stali austenitycznej X4CrMnN 16-12. Badania właściwości mechanicznych stali zostały przeprowadzone w szerokim zakresie prędkości odkształcania z użyciem maszyny serwo-hydraulicznej oraz pręta Hopkinsona. Błąd względny wyznaczony jako różnica zmierzonej i obliczonej na podstawie równania konstytutywnego krzywej naprężenie-odkształcenie został ustalony jako wartość błędu referencyjnego (metoda klasyczna). Następnie porównano go z błędem względnym wyznaczonym na podstawie zmierzonego i obliczonego za pomocą MES chwilowego przebiegu prędkości penetratora (nowa metoda). Stwierdzono dobrą korelację pomiędzy klasyczną a nową metodą oceny dokładności modela W porównaniu do klastycznej metody możliwa jest walidacja zależności konstytutywnej w szerokim zakresie prędkości odkształcania oraz temperatury w trakcie jednego testu.

5

Fracture properties of an acrylic bone cement

Bialoblocka-Juszczyk E., Baleani M., Cristofolini L., Viceconti M.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 1

21-26

EN

This study investigated experimentally the fracture properties, i.e., the fatigue strength, the resistance to crack propagation and the fracture toughness, of an acrylic bone cement (CemexĆĘ RX). The mean endurance limit was determined following the staircase method. The endurance limit was estimated at 9.2 MPa. The fatigue crack propagation rate was measured according to the ASTM E647 standard. The equation of the line fitting the crack growth per cycle (da/dN) versus the stress-intensity factor range (ŁGK), in a logˇVlog graph, was used to calculate the empirical constants of ParisˇŚ law for the selected bone cement: da/dN (m/cycle) = 3.56ˇP10ˇV7ˇPŁGK (MPaˇPm1/2)5.79. This power-law relationship described well (R2 = 0.96) the growth rate in the stable crack growth region, i.e., in the mid ŁGK range. The fracture toughness KIC of the bone cement was determined according to the ASTM E399 standard. The KIC mean value was 1.38 MPaˇPm.. These experimental results provide the set of necessary inputs for numerical studies aimed to investigate the damage accumulation process in the mantle fixing cemented prostheses.

6

Self reinforced polymer-polymer composites

Bilewicz M., Viana J. C., Dobrzański L. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

43-46

EN

Purpose: Purpose of this paper is the applying of new technology in injection moulding technique and investigation of reinforcement of PC as dispersed phase inside PP matrix. Second aim of work is enrichment of those composites by nanoclay and analyzing mechanical behaviour of nanocomposites. Design/methodology/approach: According to design of experiments (DOE) specimens were injection moulded in the shape of rectangular bars. Additionally advanced technology of melt manipulation inside mold cavity after injection was used. To achieve this purpose Ferromatik Milacron injection moulding machine, equipped with externally controlled mold was used. Findings: Addition of nanoclay clearly presents highly reinforced system, especially for neat matrix. Evenly dispersed PC particles within PP majority show reinforcement as well. Inducement of shear rate in injection moulding radically improved absorption of energy in nanocomposite. Research limitations/implications: Different variation of material composition, such combination with other polymers and use of different reinforcements (flexible or either rigid) is required to be checked in the further work. Practical implications: Reinforcement obtained thanks to dispersed phase and nanofillers creates composites with improved mechanical properties. Originality/value: Morphology development reflects on mechanical behaviour. Its manipulation may affect and improve mechanical properties. Use of advanced technologies opens wide range of possibilities in processing of polymer based systems. At present there is limited number of research of processing-structure-properties relationships of polymer-polymer composites and nanocomposites.

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Influence of two different heat treatment procedures on mechanical and fracture properties of 65 Si 7 steel.

Pustaic D., Cajner F.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

733-736

EN

This paper deals with the results of investigations of two different heat treatment procedures and their influence on some mechanical properties as well as on the magnitude of some fracture mechanics parameters for a particular type of steel. The experimental investigations were performed on the specimens made of 65Si7 steel. The processes occuring by tempering of two different microstructures of the steel, i. e. martensite and lower bainite were investigated. An advantage of austempering over hardening and tempering is in obtaining the bainite microstructure. Steel of bainite microstructure has a greater toughness, ductility, contraction, fatigue strength and better fracture toughness than a tempered martensite of the same type of steel. A bainite microstructure also gives a better resistance to thermal fatigue in comparison with martensite microstructure. The above mentioned improved values of mechanical properties refer to the untempered state of bainite.