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1
Content available remote Computer simulation of mechanical properties of quenched and tempered steel specimen
Smoljan B., Iljkić D., Tomašić N.
Journal of Achievements in Materials and Manufacturing Engineering
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2010
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Vol. 40, nr 2
155-159
EN
Purpose: The computer simulation of mechanical properties of quenched and tempered steel was investigated. The established method of computer simulation was applied in prediction of mechanical properties of workpiece with complex form. Design/methodology/approach: The method of computer simulation of mechanical properties of quenched and tempered steel was established by theoretical analysis of relevant properties which have influence on hardness of quenched and tempered steel, and by regression analysis based on experimental results. Findings: The new method of prediction of mechanical properties of quenched and tempered steel was established. Proposed method of computer simulation of mechanical properties of quenched and tempered steel is based on predicted steel hardness. Hardness distribution of quenched and tempered workpiece of complex form was predicted by computer simulation of steel quenching using a finite volume method. It was found out that mechanical properties of quenched and tempered steel can be successfully predicted by proposed method. Research limitations/implications: The investigation was done on carbon and low alloyed steel. The further experimental investigations are needed for final verification of established model. Practical implications: The established method could be applied in industrial practice. Originality/value: As-quenched hardness distribution is predicted by involving the results of simple Jominy-test in numerical modelling of steel quenching. Estimation of hardness distribution is based on time, relevant for structure transforma- tion, i.e., time of cooling from 800 to 500°C (t8/5). The distribution of mechanical properties in quenched and tempered steel workpiece is estimated based on as-quenched steel hardness, tempering temperature and Jominy-test results.
2
Content available remote Mechanical properties dependency of the pearlite content of ductile irons
Gonzaga R. A., Martinez Landa P., Perez A., Villaneuva P.
Journal of Achievements in Materials and Manufacturing Engineering
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2009
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Vol. 33, nr 2
150-158
EN
Purpose: In this work, it is pretended to make a comparison of different pearlite contents in pieces with similar shape and dimensions and to analyze the variation of mechanical properties as pearlite content increases. The three pieces used had form of stair made of ductile cast iron. Design/methodology/approach: The present study was based on an adequate balance of alloying elements. None heat treatment was used to obtain different pearlite contents in the microstructures. Many specimens taken from the cast were mechanized to be polished and swabbed with nital to analyze the microstructure. To study the mechanical properties these casts present many tests were done such as Charpy impact test, done at different temperatures. Fracture toughness and tensile strength tests were done, as well. Findings: This study gave evidences that heat treatments are not necessary to obtain different pearlite content in the microstructure. Good mechanical properties are obtained by an appropriate balance of alloying elements. Research limitations/implications: They are that of natural sources. Besides, high and precision technology must be applied to get the present results better. Practical implications: Cast iron productions are focussed straight on machine building and automotive industries and constructions. The low cost production of ductile cast iron, its mechanical properties and low cost transformations are the tempting for application. Originality/value: The whole experimental work and the appropriate results obtained as consequences of the analysis carried out are novel, although applied methods are well known. Values presented in tables are given as new results of our experiments. This work is of great importance for the development of new economical methods for ductile iron production. This study is directed to researchers and metallurgy centres.
3
Content available remote Experimental investigation of effects of external loads on erosive wear
Imrek H., Bagci M., Khalfan O. M.
Journal of Achievements in Materials and Manufacturing Engineering
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2009
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Vol. 32, nr 1
18-22
EN
Purpose: The purpose of the paper is to investigate effects of external loads on erosive wear. Design/methodology/approach: In this experimental study, specimens were placed on specially designed a specimen holder and then, external tensile loads corresponding to 0%, 20%, 40% and 60% of the specimen’s yield strength were applied on the specimens. For every load step, the specimens were subjected to 15ş, 30ş, 45ş, 60ş, 75ş and 90ş of erodent impact angles. At the end of the tests, effects of external loads and impingement angles on erosive wear were studied. In the experimental set, dry and compressed air was used to impinge erodents onto the test specimens and subsequent wear was investigated. During the tests, the impingement angles were adjusted by turning the specimen holder around its axis. Erodent particles used were SAE G40 having internal uniform martensitic structure and angular geometry. Determination of erodents speed was achieved with the help of the Rotating Double Disc Method. The speed used in the tests was 30 m/s. Findings: At the end of the tests, erosive wear rates were obtained as functions of stresses and impingement angles. Graphs showing variations of erosive wear rates for load values obtained against every impingement angle and yield stress were drawn. Critical impingement angle and load values at which maximum erosion rate was obtained were determined. Research limitations/implications: In researches made on erosive wears so far; there are only few studies dealing with the effects of external loads on the specimens subjected to erosive wear. By considering that stresses may affect the erosive wear, the stress state around contact area as well as material properties, this experimental study has thus, investigated likely effects of stresses on the erosive wear. With the help of the designed special specimen holder, the specimens were subjected to tensile stresses that are lower than the yield strength of the material and then the erosive wear was investigated. Originality/value: The investigations of effects of external loads on erosive wear.
4
Content available remote Computer simulation of working stress of heat treated steel specimen
Smoljan B., Iljkic D., Smokvina Hanza S.
Journal of Achievements in Materials and Manufacturing Engineering
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2009
|
Vol. 34, nr 2
152-156
EN
Purpose: In this paper, the prediction of working stress of quenched and tempered steel has been done. The working stress was characterized by yield strength and fracture toughness. The method of computer simulation of working stress was applied in workpiece of complex form. Design/methodology/approach: Hardness distribution of quenched and tempered workpiece of complex form was predicted by computer simulation of steel quenching using a finite volume method. The algorithm of estimation of yield strength and fracture toughness was based on steel hardness, HV. Yield strength and fracture toughness distributions have been predicted using the Hahn-Rosenfield approach. Findings:It can be concluded that working stress of quenched and tempered steel can be successfully predicted by proposed method. The further experimental investigations are needed for final verification of established model. Research limitations/implications: For efficient estimation of fracture toughness from hardness, additional data about microstructure are needed. Practical implications: Estimation of hardness distribution can be based on time, relevant for structure transformation, i.e., time of cooling from 800 to 500 şC (t8/5). The prediction of distribution of microstructure composition, yield strength, and fracture toughness, can be based on steel hardness. Originality/value: Hardness distribution is predicted by involving the results of simple experimental test, i.e., Jominy-test in numerical modelling of steel quenching.
5
Hydrogen embrittlement in low carbon steel
Siddiqui R. A., Abdul-Wahab S. A., Pervez T., Qamar S. Z.
Archives of Materials Science
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2007
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Vol. 28, nr 1-4
136-142
EN
Many metals and alloys absorb hydrogen and diffusion of hydrogen under certain conditions can seriously weaken and produces embrittlement in steel. Hydrogen embrittlement is a type of metal deterioration that is related to stress corrosion cracking. Although steels are well known for their susceptibility to hydrogen embrittlement, the mechanism of transportation of hydrogen is not very clear in low carbon steels. Standard tensile steel specimens were hydrogenated from 1 to 5 hours and deformed by cold worked to 50%, 60%, 70% and 80% and were investigated for mechanical properties.
6
The superplstic state in A7475 alloy related to the structure and mechanical properties
Król J., Tałach-Dumańska M.
Archives of Metallurgy
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2002
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Vol. 47, iss. 1
17-26
EN
The superplastic deformation process is interesing not only from scientific point of view but also because of benefits it offers when appied in industry. The generation of superplastic structures in aluminium alloys of the 7XXX type depends on the formation of precipitates in suitable amount, size and dispersion which may be obtained by thermomechanical treatment. The A7475 alloy was continuously cast, extruded and thermomechanically treated. The investigations on creating precipitates and microstructure of the AlZnCuMgCr alloy were performed using optical, scanning and transmission electron microscopy and X-ray phase analysis. The morphology of the alloy after a full thermomechanical treatment showed fine, equiaxial average grain about 12 µm in size. The strain rate sensitivity coefficient m determined from tensile tests was estimated between 0.56-0.70. About 495 pct elongation was obtained in a tension test at the flow stress of 3 MPa, strain rate 8x10-3s-1 and temperature 790K. It demonstrates that material of good superplastic properties was elaborated.
PL
Wytworzenie struktury superplastycznej w stopach aluminium typu 7XXX jest zależne od powstania wydzieleń o odpowiedniej wielkości, dyspersji i ilości, co może zostać uzyskane na drodze obróbki termomechanicznej. Stop A7475 odlewany metodą ciągłą i wyciskany, był następnie obrabiany w procesach termomechanicznych. Badania tworzących się wydzieleń i mikrostrukr\tury w stopieAlZnCuMgCr przeprowadzono metodami mikroskopii optycznej, skanningowej i elektronowej oraz rtg. analizy fazowej. Morfologia stopu po pełnej obróbce termomechanicznej charakteryzowała się drobnymi, równoosiowymi ziarnami o wielkości ok. 12 µm. Współczynnik czułości na szybkość odkształcenia określony w teście rozciągania osiągnł wartość m=0,56-0,70. Maksymalne wydłużenie uzyskane w teście rozciągania przy naprężeniu płynięcia ok. 3 MPa, szybkości odkształcenia 8x10-3s-1 i w temperaturze 790K osiągnęło wartość 495%. Świadczy to o uzyskaniu materiału o dobrych własnościach superplastycznych.
7
Deformation processing map for CuAl8.1Fe2.9 aluminium bronze.
Gronostajski Z.
Inżynieria Materiałowa
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2001
|
R. XXII, nr 4
365-368
PL
Naprężenie uplastyczniające brązu aluminiowego CuAl8.1Fe2.9 wyznaczane w próbie skręcania w szerokim zakresie temperatur i prędkości odkształcania było analizowane przy użyciu dynamicznego modelu materiału. Model ten rozpatruje materiał odkształcany w podwyższonych temperaturach jako dyssypator mocy. Mapa efektywności procesów, reprezentująca dyssypację mocy w funkcji temperatury i prędkości odkształcania, została opracowana i na jej podstawie ustalone zostały obszary w których zachodzą procesy rekrystalizacji dynamicznej i dynamicznego zdrowienia oraz optymalne warunki odksztacania.
EN
The flow stress data obtained in torsion test of CuAl8.1Fe2.9 aluminium bronze at different temperatures and strain rate are analysed using dynamic material's model which considers the workpiece as a power dissipator. A processing map representing the efficiency of power dissipation as a function of temperature and strain rate has been established and areas of dynamic recovery and recrystallization processes as well as optimum processing conditions for the aluminium bronze was determined.
8
Formability modelling of aluminium base PM alloys.
Bagaviev A., Durisin J., Dybiec H., Klein K., Mandziej S., Ziaja G.
Inżynieria Materiałowa
|
1998
|
R. XIX, nr 4
1153-1158
EN
The paper presents the results investigations carried out in the frame of the Project CT 96-0750 MicroAlu of Inco-Copernicus program. The investigated materials are PM aluminium alloys with high contents of silicon. The aim of this part is a comprehensive characterisation of microstructure features and specific parameters at the example of an AlSi27Ni6 alloy. The experiments on the plastic and viscoplastic behaviour of this alloy (compressive and tensile tests) at different temperatures and strain rates were done to identify the material properties. The evolution of the microstructure of the tested specimens due to temperature rise and deformation process was investigated with optical and electron microscopy as well as with X-ray analysis technique. The alloy was compacted by a PM extrusion process to a preform and then forged to a final product -connecting rod. From the performed experiments the constitutive parameters were identified and the connecting rod forging process has been simulated by means of a general purpose FEM program.
9
Application of Garafalo model for description of flow stress of brasses M63 and MO58.
Gronostajski Z.J.
Inżynieria Materiałowa
|
1998
|
R. XIX, nr 4
677-680
EN
In the paper application of the Garafalo model for description of the characteristic values of flow stress of M63, MO58 and MP58A brasses and simple relation determining the boundary between two different shape of flow stress-strain curves is presented.
10
Aluminium base composites for high temperature application.
Gronostajski J., Matuszak A., Marciniak H., Samuel M.
Inżynieria Materiałowa
|
1998
|
R. XIX, nr 4
750-735
EN
In this paper is presented the method of manufacturing of composites characterized by good mechanical properties at high temperature by direct recycling of aluminium chips with ferro-chromium powder as reinforcing phase.
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