Showing 16 results for Mechanical Properties
M. Kalantar and G. Fantozzi,
Volume 22, Issue 1 (7-2003)
Abstract
Dense Silicon nitride was investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties and thermal stress resistance to fracture initiation during a hot or cold mechanical and thermal shock testing. The different materials and microstructures were obtained by changing the parameters such as the type of the powder, additive, forming process and sintering condition. Maximum crack growth and thermal shock resistance of dense Si3N4 are achieved after complete conversion of the aàB transformation, and after the change in grain morphology towards elongated
grain and the relative crystallization of the second phases have been obtained. The characteristics are obtained by a high a phase content of the starting powder, high Y2O3, and sintering condition of higher temperature (2000ْC), longer soaking times (1h) and load application at the beginning of the thermal cycle.
Keywords: Silicon nitride, Thermo- mechanical properties, Thermal shock resistance, Crack propagation resistance
M. Bahrami, M.h. Fathi, M. Ahmadian,
Volume 32, Issue 1 (6-2013)
Abstract
Short life of current total hip replacement metallic implants is generally dependent on the aseptic loosening of the implant, which occurs due to mismatch of elastic modulus between bone and metallic implant materials. Decreasing in elasticmodulus of implant could be successful. Forsterite is biocompatible and bioactive ceramic which has suitable mechanical properties. In presented research the composite materials based on Co-Cr-Mo alloy with 10, 15 and 20wt% of forsteritenanopowder as reinforcement were fabricated and mechanical behavior of the composites were evaluated. Composites were fabricated by ball milling, cold pressing and sintering. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization and evaluation phase composition and microstructure of the composites. Density, microhardness, compressive strength and elastic modulus of fabricated composites were evaluated. Obtained results showed elastic modulus of composite materials based on Co-Cr-Mo alloy reinforced with 10, 15 and 20wt% of forsteritenanopowder decreased significantly. Results also showed that the compressive strength of Co-base alloy composites reinforced with 10, 15 and 20 wt% forsterite were lower than cast Co-Cr-Mo alloy. With increasing in the content of reinforcement, compressive strength of the composites were decreased. Microhardness of prepared composites were higher than cast Co-Cr-Mo alloy. With increasing in content of bioceramic reinforcement, microhardness of the composites were increased.
M. Esmaeeli, A.mirhabibi ,
Volume 33, Issue 1 (7-2014)
Abstract
An important parameter in composite materials is mechanical behavior and matrix-reinforcement interface interaction under applied stresses. In this investigation, bending strength of carbon-carbon composites synthesized from wood was analyzed as a measure of the composite mechanical properties. Also, densification efficiency of the products was determined by measuring the bulk density and open porosity percentage. Using scanning electron microscopy, optical microscopy, X-Ray diffraction, and Raman spectroscopy, the final product was examined to evaluate and interpret the morphology and internal texture and results of mechanical test. The results showed that we are able to use an ordinary material such as wood for production of a unique product with great properties called two-dimensional carbon-carbon composites.
M. Talebian, M. Alizadeh, M. Ehteshamzadeh,
Volume 33, Issue 2 (3-2015)
Abstract
In this study, Al/Steel multilayer composite was produced by accumulative roll bonding (ARB) process using Al-1100 and St-12 strips. Microstructure, mechanical properties and corrosion behavior of the composite were studied by scanning electron microscopy (SEM), tensile test, Vickers microhardness tests, cyclic polarization and electrochemical impedance spectroscopy (EIS) measurement in 3.5 wt% NaCl solution. After one ARB cycle (2 roll-bonding cycles), the multilayer composite of 4 layers of Al and 2 layers of steel was produced. The tensile strength of the Al/steel multilayer composite reached 390.57 MPa after the first ARB cycle, which was 1.29 times larger than that of the starting steel while composite density was almost half the density of the steel. Corrosion behavior of the composite revealed a considerable improvement in the main electrochemical parameters, as a result of enhancing influence of cold rolling. The results indicated that strength and corrosion resistance of Al/steel composite generally decreases and elongation increases after annealing.
F.s. Sayyedan, M.h. Fathi, H. Edris, A. Doostmohamadi, V.s., Mortazavi, F. Shirani,
Volume 33, Issue 3 (3-2015)
Abstract
The objective of this study was to synthesize glass ionomer–forsterite nanocomposite and study the effect of
incorporating forsterite nanoparticles to the ceramic part of glass ionomer cement in order to improve mechanical properties and
bioactivity. So, Forsterite nanoparticles were made by the sol-gel process using different weight percentages added to the ceramic
part of commercial GIC (Fuji II GC). X-ray diffraction (XRD) was used in order to characterize and determine grain size of the
produced forsterite nanopowder. In order to study the mechanical properties of the produced glass ionomer cement-forsterite
nanocomposite, the compressive strength (CS), three-point flexural strength (FS) and diametral tensile strength (DTS) of
specimens were measured. Statistical analysis was done by one Way ANOVA and differences were considered significant if
P‹0.05. The morphology of fracture surface of specimens was studied using scanning electron microscopy (SEM) technique.
Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electron microscopy
(SEM), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results of XRD analysis confirmed the
nanocrystalline and pure forsterite synthesis. According to the mechanical properties measurements, the optimum weight
percentages of forsterite nanoparticles for enhancement of CS, FS, and DTS were obtained equal to 3, 1 and 1 wt.%, respectively.
Statistical analysis showed that the differences between all the groups were significant (P<0.05). SEM images and results of the
ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Glass ionomer-forsterite nanocomposite containing 1 to
3 wt.%-forsterite nanoparticles can be a suitable candidate for dentistry and orthopedic applications due to the improvement of
mechanical properties and bioactivity.
M.r. Dehnavi, B. Niroumand, F. Ashrafizadeh,
Volume 34, Issue 1 (5-2015)
Abstract
Effects of discontinuous ultrasonic treatment on the microstructure, nanoparticle distribution, and mechanical properties of cast Al413-SiCnp nanocomposites were studied. The results showed that discontinuous ultrasonic treatment was more effective in improving the mechanical properties of the cast nanocomposites than the equally timed continuous treatment. The yield and ultimate tensile strengths of Al413-2%SiCnp nanocomposites discontinuously treated for two 20 minute periods increased by about 126% and 100% compared to those of the monolithic sample, respectively. These improvements were about 107% and 94% for the nanocomposites continuously treated for a single 40 minute period. The improvement in the mechanical properties was associated with severe refinement of the microstructure, removal of the remaining gas layers on the particles surfaces, more effective fragmentation of the remaining agglomerates as well as improved wettability and distribution of the reinforcing particles during the first stage of solidification.
M. Jafarian, M. Paidar, M. Jafarian,
Volume 35, Issue 1 (6-2016)
Abstract
In this study, microstructure and mechanical properties of diffusion joints between 5754, 6061 and 7039 aluminum alloys and AZ31 magnesium alloy were investigated. Diffusion joints were done between the alloys at 440 °C, for duration of 60minutes, at 29 MPa pressure and under 1×10-4 torr vacuum. The interface of joints was studied using optical (OM) and scanning electron microscopy (SEM) equipped with EDS analysis and the line scan. According to the results of EDS analysis, the presence of intermetallic compounds including Al12Mg17, Al3Mg2 and their mixture was observed at the diffusion zone. Also, according to the results of the line scan, the hardness value of aluminum alloys has a considerable effect on diffusion of the magnesium atoms toward aluminum alloy and the greatest diffusion of magnesium was observed when 6061 aluminum alloy was used. More diffusion resulted in a stronger bond between atoms of magnesium and aluminum, and maximum strength of approximately 42 MPa was obtained when 6061 aluminum alloy was used.
M. Rezazadeh, M.r. Saeri, F. Tirgir Malkhlifeh, A. Doostmohammdi,
Volume 35, Issue 2 (9-2016)
Abstract
The aim of the present study is to study the effects of adding diopside (CaMgSi2O6) as well as silica sulfuric acid nanoparticles to ceramic part of glass ionomer cement (GIC) in order to improve its mechanical properties. To do this, firstly, diopside (DIO) nanoparticles with chemical formula of CaMgSi2O6 were synthesized using sol-gel process and then, the structural and morphological properties of synthesized diopside nanoparticles were investigated. The results of scanning electron microscopy (SEM) and particle size analyzing (PSA) confirmed that synthesized diopside are nanoparticles and agglomerated. Besides, the result of X-ray diffraction (XRD) analyses approved the purity of diopside nanoparticles compounds. Silica sulfuric acid (SSA) nanoparticles are also prepared by chemical modification of silica nanoparticles by means of chlorosulfonic acid. Fourier transform infrared spectroscopy (FTIR) technique was used to find about the presence of the (SO3H) groups on the surface of silica sulfuric acid nanoparticles. Furthermore, various amounts (0.1, 3 and 5 wt.%) of diopside and silica sulfuric acid nanoparticles were added to the ceramic part of GIC (Fuji II GIC commercial type) to produce glass ionomer cement nanocomposites. The mechanical properties of the produced nanocomposites were measured using the compressive strength, three-point flexural strength and diametral tensile strength methods. Fourier transform infrared spectroscopy technique confirmed the presence of the (SO3H) groups on the surface of silica nanoparticles. The compressive strength, three-point flexural strength and diametral tensile strength were 42.5, 15.4 and 6 MPa, respectively, without addition. Although adding 1% silica solfonic acid improved nanocomposite mchanical properties by almost 122%, but maximum increase in nanocomposite mechanical properties was observed in the nanocomposites with 3% diposid, in which 160% increase was seen in the mechanical properties.
Seyed M. Ahl Sarmadi, M. Shamanian, H. Edris, M. Atapoor, A. Behjat, M. Mohtadi Bonab, J. Szpunar,
Volume 36, Issue 1 (6-2017)
Abstract
Super duplex stainless steel is a kind of duplex stainless steel that has pitting resistant equivalent number over than 40. Unified Numbering System (UNS) S32750 is a common super duplex stainless stee, that is mostly applied in oil and gas refinery industries, because of its proper corrosion-resistant properties . Therefore, joining of these steels by welding is very important, but the greatest problem in this regard is the corrosion and decrease in mechanical properties after welding.. In this research, UNS S32750has been joined by friction stir welding method. The tool being used in this research was a WC with 16mm shoulder diameter, 5 mm pin diameter, and 1.9 mm height. X-ray diffraction showed that harmful phases, such as sigma or chi have not been formed. Microstructure study indicated that grain size in the stir zone has decreased. Vickers Hardness Test Method has been applied on welded samples. Moderate microhardness of base metal was 285 Vickers but, the microhardness increased in the stir zone to 360 Vickers, because of decreasing the grain size. The cyclic polarization determined that potential and corrosion current of joint metal by friction stir welding method was similar to base metal. Also, it was revealed that ferrite percentage in the stir zone doesn't decrease very much because the friction stir welding heat input is very low and the colding rate is very high.
M. Poorkabirian, H. Mostaan, M. Rafiei,
Volume 36, Issue 2 (9-2017)
Abstract
In this research, dissimilar welding between 4130 low alloy steel and austenitic stainless steel 316L has been investigated using Gas Tungsten Arc Welding (GTAW). Two types of filler metals, including ERNiCr-3 and ER309L, were used for this purpose. Moreover, the joint microstructures including the weld metals, heat affected zones and interfaces were characterized by optical and Scanning Electron Microscopy (SEM). The mechanical behavior of the joint was tested by impact and tension tests. Observations by SEM showed that in impact test, the fracture is soft. In the tensile test, the welded sample by ER309L filler metal was fractured from 316L base metal, but welded specimen with ERNiCr-3 was fractured from welded zone. Also, the results showed a dendritic structure in the nickel-based weld metal. No crack was found in the cellular-dendritic microstructure of ER309L weld metal due to the existance of delta ferrite between them.
M. Lashani Zand, B. Niroumand, A. Maleki,
Volume 37, Issue 4 (3-2019)
Abstract
Mechanical properties of the alloys are a strong function of the average silicon particles size and the secondary dendrite arm spacing (SDAS). Modified Hall-Petch equation expresses the effects of these two microstructural parameters on the yield strength and ultimate tensile strength of the Al-Si based alloys. These microstructural parameters depen on parameters such as chemical composition, cooling rate and melt treatment. In this study, the effect of cooling rate on the equation constants of the alloy were determined. For this purpose, the alloy was poured at 750 °C in three different molds including a sand mold, a preheated steel mold, and a water cooled steel mold. The Thermal and microstructural analysis showed that the cooling rate in the metal mold was 15.7 times higher than that of the sand mold, which resulted in a decrease of the SDAS from 54 micrometers to 17 micrometers. It was also found that by reducing the SDAS from 45 micrometers to 17 micrometers, the yield strength and tensile strength were increased by 16.5% and 6.5%, respectively. The modified Hall-Petch equation constants and the microstructure-mechanical properties relationships were then established by the microstructural and tensile test studies.
M. Rajabi, M. Shahmiri, M. Ghanbari,
Volume 37, Issue 4 (3-2019)
Abstract
In this study, the effects of boron (B) and zirconium (Zr) on the microstructure and mechanical properties of Fe3Al-based alloys were investigated. Cylindrical samples were produced using a vacuum induction melting furnace (VIM); consequently, the melt was cast into a metallic mold. The microstructure, phase identification, tensile and compressive mechanical properties and fractography of the samples were investigated. Upon microstructural observation, it was found that the alloys microstucture was denderitic and the precipitated phases were mostly present between interdendritic regions. Addition of B and Zr to the alloys resulted in the formation of boride precipitates and Laves phases. The results, therefore, showed that Zr had the most pronounced effect on the mechanical properties because of the formation of Laves phases. Fractographic studies of alloys also revealed that the brittle fracture was dominant between the samples.
H. R. Shahverdi, R. Alipour Mogadam,
Volume 38, Issue 2 (9-2019)
Abstract
Creep age forming (CAF) process is a novel metal forming method with major benefits including improved mechanical properties and cost reduction for aviation industry applications. CAF happens due to creep phenomenon and stress-release during the artificial aging of heat-treatable aluminum alloys. In this work, the creep age forming of 7075 Aluminum alloy at 120, 150 and 180 °C for 6, 24 and 48 h was done; tensile and hardness tests were used to characterize the samples. Results on spring-back revealed that it was influenced by time and temperature; by increasing the time and temperature, it was reduced from 54.1 to 39.51. Mechanical property evaluation also showed that by increasing the time, the strength and hardness could be enhanced due to microstructural evolution and precipitation during the CAF process. According to the mechanical and CAF results, two samples were selected as the optimum ones and their work hardening behavior and fracture surfaces were investigated
S. Torabi, S. Khorshidi, A. Karkhaneh,
Volume 39, Issue 2 (8-2020)
Abstract
For many years, dexamethasone has been used as an anti-inflammatory drug and is still one of the safest glucocorticoids for treating various diseases. Due to the wide range of the side effects of this drug, it is essential to find a suitable delivering system for reduction in dosage with increased effectiveness. Electrospinning is one of the fiber fabrication methods which is widely used to develop drug carriers due to its ability to load various drugs and biological components and control their release. In this research, neat poly (lactic acid) electrospun fibers and dexamethasone loaded fibers were prepared. To evaluate the effect of polymer concentration on morphology, mechanical properties and drug release profile of the resulting fibers, three polymer concentrations of 10%, 14% and 18% w/v were processed. Thereafter, 5% w/v dexamethasone was added to solutions. The scanning electron microscopy images were investigated to obtain the average diameter of fibers and the average area of pores in each sample. In neat samples, by moving from 10% to 18% composition, the average diameter of the fibers increased by 63.21%. However, in drug loaded samples this increased by 51/19%. After evaluating mechanical properties, an increase of 81/34% in Elastic modulus by moving from 10% to 18% composition was observed. Moreover, the ultimate strength increased by 68/021% when increasing the polymer concentration from 10 to 18%. Drug release from the electrospun samples was continued up to 7 days. Linear release was observed in 10% and 14% compositions. The drug release pattern of these samples was of zero order. Considering the importance of zero order release in different applications of dexamethasone, these delivering systems could be useful. The maximum drug release rate belonged to 14% composition (0.044 1/h).
S. Asghari, A. M. Eslami, A. Taheri Zadeh, N. Saeidi,
Volume 39, Issue 3 (12-2020)
Abstract
In this study, the effect of welding heat input on microstructure and mechanical properties of dissimilar joints of API-X42 and API-B pipeline steels was investigated. Evaluation of the microstructures showed that increasing the welding heat input decreased acicular ferrite in weld metal microstructure, while amount of Widmanstatten ferrite, polygonal ferrite and grain boundary ferrite increased. Also, results of microhardness test showed that by increasing the heat input, hardness of weld metal and the heat affected zone decreased. Tensile test results showed that as the heat input increased, fracture transferred from base metal of API-B to the heat affected zone. Impact test results also showed that increasing the welding heat input could sharply drop the impact energy of the heat affected zone for both base metals due to extensive grain growth.
F. Rafati, N. Johari, F. Zohari,
Volume 40, Issue 4 (3-2022)
Abstract
In the present study, PCL/ZnO nanocomposite scaffolds containing 0, 5, and 15 wt.% of ZnO nanoparticles were prepared via the salt leaching/solvent casting method. The influence of ZnO nanoparticles on the morphology of prepared PCL/ZnO scaffolds was investigated using SEM images. The compressive strength test evaluated the effect of scaffolds’ morphology on mechanical properties. The XRD technique confirmed the desired phases in the scaffold composition. The results showed that the compressive strength and structural integrity of the scaffolds increased by increasing ZnO nanoparticles content as the reinforcement. However, the compressive strength and structural integrity decreased by increasing the amount of ZnO nanoparticles up to more than 5 wt.%. In summary, PCL/ZnO nanocomposite scaffold containing 5 wt.% of ZnO nanoparticles revealed the highest strength, compressive modulus, and structural integrity.
