共查询到18条相似文献，搜索用时 0 毫秒
1.
Tânia A. F. Rodrigues Filipe J. P. Chaves Lucas F. M. da Silva Marcelo Costa Ana Q. Barbosa 《Materialwissenschaft und Werkstofftechnik》2017,48(11):1181-1190
Adhesive joints in the transportation industry may be exposed to aggressive environments such as humidity during their service life, which may influence their reliability. This research aims to determine the fracture toughness of aluminium bonded joints under pure mode I, pure mode II and mixed mode I and II loadings in dry and wet condition, with the main purpose to predict the influence of humidity in the toughness properties of an adhesive. It was found that water does influence the fracture mechanics properties, increasing mode I fracture toughness and decreasing mode II fracture toughness. 相似文献
2.
The perovskite material La0.58Sr0.4Co0.8Fe0.2O3‐δ, offers high oxygen permeability at elevated temperature and is considered as a potential material for oxygen separation membranes. It can enhance the efficiency of oxy‐fuel combustion at high temperatures (> 800 °C) and hence due to the high reliability demands, required by the long term operation at elevated temperatures, it requires a thorough investigation from the view point of structural stability. Aiming towards long term stability, the present work is a detailed and systematic study on the effect of annealing on the mechanical behavior of dense La0.58Sr0.4Co0.8Fe0.2O3‐δ. The study reveals that the indentation fracture toughness of the material increases with increase in annealing temperature. In most of the indentation loads, the subsurface crack profile was Palmqvist in nature with low value of the ratio of crack length versus indentation size (c/a). A consistent pattern of variation of c/a and indentation fracture toughness (KIC) at all indentation loads was observed. Systematic drop in c/a and subsequent increase in fracture toughness in the as prepared test pieces has been attributed to residual stress accumulation during preparation. 相似文献
3.
M. Masimov 《Materialwissenschaft und Werkstofftechnik》2008,39(8):571-578
Hot dip galvanizing induced strength decrease in wire steels Wire steels C80D and C80D Nb obtained by hot dip galvanizing procedure were investigated by optical and electron microscopy as well as by X‐ray analysis. The investigations were carried out at different stages of production of wires. The results of the investigations were checked by micro‐hardness measurements. Arising of cracks in wires surface during hot dip galvanizing as a reason for decrease in tensile strength was established. Influences of technological parameter such as galvanizing velocity, type of cooling and residual stresses and strength of wires before galvanizing on cracking of wire was taken in consideration. 相似文献
4.
The impact of various heat treatment procedures on microstructure, dislocation density, hardness, tensile characteristics, and impact toughness of P92 steel was examined in the current experiment. The martensitic microstructure and average microhardness of 463 HV 0.2±8 HV 0.2 of the normalized steel were prevalent. A tempering procedure was carried out at 760 °C for a range of 2 hours to 6 hours. Additionally, an X-ray diffraction examination was carried out, and the results were used to determine the dislocation density. The normalized sample was characterized by a high dislocation density. The dislocation density was decreased by tempering of normalized samples. With an increase in tempering time, the effect of the treatment coarsened the grains, precipitates, and decreased the area fraction of precipitates. After tempering, MX, M23C6, and M7C3 types precipitates were found to have precipitated, according to energy dispersive spectroscopy and x-ray diffraction research. The ideal tempering period was determined to be 4 hours at a tempering temperature of 760 °C based on the microstructure and mechanical characteristics. Steel that was tempered at 760 °C for 4 hours had a yield strength of 472 MPa, an ultimate tensile strength of 668.02 MPa, and an elongation of 26.05 %, respectively. 相似文献
5.
In this work the fracture toughness and responsible microstructural characteristics of AlSiCu casting alloys were investigated. A conventional A226 alloy and an alloy which is adapted for high temperature use were analyzed. A strong relationship between the cooling speed and the mechanical properties was found as well as the phases responsible for failure were identified. 相似文献
6.
F. A. Costa Oliveira H. Reboredo J. Cruz Fernandes 《Materialwissenschaft und Werkstofftechnik》2016,47(9):797-807
Dynamic fatigue of a low dielectric loss steatite was investigated. To this end, the values of n and B, the so‐called subcritical crack growth (SCG) parameters were experimentally determined. The steatite exhibited the expected dynamic fatigue behaviour, so that the stress corrosion susceptibility parameter, n, of 24 was obtained. In addition, the material/environment parameter B, which is a constant for a given test environment, was also attained. These parameters are instrumental in predicting the lifetime of components under stress. When the applied load is such that the resulting strength equals half of the inert strength (σi), defined as the strength of a sample tested in an inert environment or at a fast stress rate, i.e. where no subcritical crack growth occurs, the time to failure (tf) of the material was found to be ～140 h. Measurement of the fracture toughness of steatite is also of upmost importance and so it was determined using three test methods. A value of KIc = 1.91 ± 0.29 MPa m1/2 was attained by the indentation fracture method through measurement of the cracks emanating from the Vickers indentation. This value is in good agreement with those determined using the KIsc (surface crack in flexure) test method (2.21 ± 0.07 MPa m1/2) and fractography analysis test method (2.00 ± 0.44 MPa m1/2). Differences in test procedure and analysis causing the values from each test method to be different are discussed. 相似文献
7.
V. Bolbut I. Bogomol C. Bauer M. Krüger 《Materialwissenschaft und Werkstofftechnik》2017,48(11):1113-1124
Two high temperature alloys, namely Mo‐13Zr‐25.9B and Mo‐17.4Zr‐34.8B (in at. %), which were specified as eutectic compositions according to the literature were produced with a zone melting (ZM) method [1, 2]. Investigations with a scanning electron microscope demonstrated that the microstructures of both alloys are not completely eutectic. The alloy Mo‐13Zr‐25.9B shows well‐aligned arrangements of their microstructural constituents along the crystallization direction. X‐ray diffraction analysis revealed the phases molybdenum solid solution and zirconium monoboride (ZrB) in each alloy and, additionally, in alloy Mo‐13Zr‐25.9B the phases Mo2Zr and dimolybdenum boride (Mo2B) and in alloy Mo‐17.4Zr‐34.8B the phase zirconium diboride (ZrB2). Moreover, the microhardness of the individual phases was measured. The fracture toughness of both materials was determined using the SEVNB method according to DIN EN ISO 23146. Finally, the creep resistance of the alloys was tested at 1100 °C under compressive loading and compared with other molybdenum alloys and a single‐crystalline nickel based superalloy. 相似文献
8.
The work‐hardening response and mechanical properties of dual phase steels originated from different initial microstructures under low and high martensite volume fractions were investigated using a typical carbon‐manganese steel. The modified Crussard‐Jaoul analysis was used for studying the work‐hardening stages and the deformation behavior of ferrite and martensite. It was revealed that the initial martensitic microstructure before intercritical annealing is much better than the full annealed banded ferritic‐pearlitic and spheroidized microstructures in terms of work‐hardening capacity and strength‐ductility trade off. By increasing the amount of martensite, via intercritical annealing at higher temperatures, the ductility decreased but the tensile toughness of dual phase steels increased toward reaching the domain of extra‐advanced high‐strength steels due to the enhancement of work‐hardening rate. 相似文献
9.
In the present work, an indigenously developed low cost modified stir casting technique is developed for the processing of 6061 Al‐B4C composites containing high‐volume fraction of boron carbide particles (up to 20 vol. %). The influence of varying reinforcement content on the spatial distribution of boron carbide in the aluminum matrix is qualitatively characterized using scanning electron microscope. At a lower volume fraction of reinforcement, wide particle free zone and large interparticle spacing were observed in the matrix while the composite with high reinforcement content displayed relatively homogeneous and discrete particle distribution. X‐ray diffraction analysis confirms the presence of only aluminum and boron carbide diffraction peaks, indicating that no significant reaction occurs during composite processing. The tensile behavior of composites revealed that strength and ductility are influenced by varying particulate content. The quantitative analysis of strengthening mechanism in the casted composites showed that higher volume fraction of boron carbide lead to larger values of thermal dislocation strengthening, grain size and strain gradient strengthening. The morphology of fracture surfaces reveals the presence of dimple network and the average size of dimples gradually decreases with the increase in particulate content, which indicates the co‐existence of ductile and brittle fracture. 相似文献
10.
The superior mechanical properties of sandwich composites made them to favored materials, in particular in the aviation industry. However, environmental influences along the manufacturing process and during usage can reduce the strength and the life expectation of the composite parts. This contribution presents an experimental investigation on the effect of accelerated ageing on the mechanical properties of perpendicular honeycomb sandwich connections. Static tensile tests have been carried out on sets of new and 25 days artificially aged specimens and the load carrying capacity of the T‐joints has been measured. In parallel to the experimental part, a three dimensional finite element analysis has been performed. This combined approach allows quantifying the reduction of the fracture toughness of the connections. The obtained results will help to fulfill design requirements and to predict the long‐term structural behavior of sandwich composite constructions. 相似文献
11.
S. Moakhar H. Hentati M. Barkallah J. Louati M. Haddar C. Bonk B.A. Behrens 《Materialwissenschaft und Werkstofftechnik》2019,50(11):1353-1363
12.
C. Held J. Dadrich R. Denninger R. Schleich K. A. Weidenmann M. Liewald 《Materialwissenschaft und Werkstofftechnik》2009,40(11):831-835
Semi‐empirical calculation method for prediction of Forming Limit Curves based on mechanical properties For characterisation purposes of sheet metal forming processes concerning feasibility of material mainly the Forming Limit Curve (FLC) is commonly used. This failure model can either be measured experimentally or can be predicted by using semi‐empirical approaches. These mathematical approaches mainly are validated for Mild Steels. However, prediction of FLCs for modern High Strength Steels or Aluminium sheet alloys is not possible with acceptable accuracy today. This is why this contribution deals with a new semi‐empirical approach for FLC prediction, which is valid for all sheet metal materials used in car body production. This approach uses a correlation of mechanical properties of uniaxial tensile test an experimentally determined limit strains. 相似文献
13.
《Mauerwerk》2017,21(2):82-89
The buckling of masonry wall depends on the deformation behaviour and can be described with the modulus of elasticity depending on masonry strength. The reduction factor solution considering buckling is described by the Gaussian bell‐shaped curve in Eurocode 6, Part 1‐1 Annex G and was calibrated for masonry with a modulus of elasticity between 700 and 1000 fk, which describes the masonry currently used in most European countries. In case of historic masonry or where deformability is needed in new construction, the modulus of elasticity can actually be lower. In those cases the approximation procedure according to Annex G of the Eurocode 6 delivers results which do not represent the real behaviour and leads to uneconomical results. The present paper proposes a new empirical method, which can be applied over the whole practical range of the elastic modulus of masonry. The new proposed method has been verified with experimental data and shows a very good fit. 相似文献
14.
《Materials and Manufacturing Processes》2012,27(6):768-772
‘Torayca’ T800H/3900-2 is the first material qualified on Boeing Material Specification (BMS 8-276) which utilizes the thermoplastic-particulate interlayer toughening technology. Two manufacturing processes, the autoclave process and the fast heating rated Quickstep™ process, were employed to cure this material. The Quickstep process is a unique composite production technology which utilizes the fast heat transfer rate of fluid to heat and cure polymer composite components. The manufacturing influence on the mode I delamination fracture toughness of laminates was investigated by performing double cantilever beam tests. The composite specimens fabricated by two processes exhibited dissimilar delamination resistance curves (R-curves) under mode I loading. The initial value of fracture toughness G IC–INIT was 564 J/m2 for the autoclave specimens and 527 J/m2 for the Quickstep specimens. However, the average propagation fracture toughness G IC–PROP was 783 J/m2 for the Quickstep specimens, which was 2.6 times of that for the autoclave specimens. The mechanism of fracture occurred during delamination was studied under scanning electron microscope (SEM). Three types of fracture were observed: the interlayer fracture, the interface fracture, and the intralaminar fracture. These three types of fracture played different roles in affecting the delamination resistance curves during the crack growth. More fiber bridging was found in the process of delamination for the Quickstep specimens. Better fiber/matrix adhesion was found in the Quickstep specimens by conducting indentation-debond tests. 相似文献
15.
'Torayca' T800H/3900-2 is the first material qualified on Boeing Material Specification (BMS 8-276) which utilizes the thermoplastic-particulate interlayer toughening technology. Two manufacturing processes, the autoclave process and the fast heating rated Quickstep™ process, were employed to cure this material. The Quickstep process is a unique composite production technology which utilizes the fast heat transfer rate of fluid to heat and cure polymer composite components. The manufacturing influence on the mode I delamination fracture toughness of laminates was investigated by performing double cantilever beam tests. The composite specimens fabricated by two processes exhibited dissimilar delamination resistance curves (R-curves) under mode I loading. The initial value of fracture toughness GIC-INIT was 564 J/m2 for the autoclave specimens and 527 J/m2 for the Quickstep specimens. However, the average propagation fracture toughness GIC-PROP was 783 J/m2 for the Quickstep specimens, which was 2.6 times of that for the autoclave specimens. The mechanism of fracture occurred during delamination was studied under scanning electron microscope (SEM). Three types of fracture were observed: the interlayer fracture, the interface fracture, and the intralaminar fracture. These three types of fracture played different roles in affecting the delamination resistance curves during the crack growth. More fiber bridging was found in the process of delamination for the Quickstep specimens. Better fiber/matrix adhesion was found in the Quickstep specimens by conducting indentation-debond tests. 相似文献
16.
A. Farzadi 《Materialwissenschaft und Werkstofftechnik》2017,48(2):151-162
Microstructural evolution and mechanical properties of friction stir welded AA7075‐T6 aluminum alloy were examined. Grain structure and precipitate evolution in the stir zone and heat‐affected zone were evaluated using optical microscope and differential scanning calorimetry. A significant grain refinement and dissolution of η′ precipitates in the stir zone were found, but chromium‐bearing dispersoids remained nearly unchanged. The main particles in the stir zone and heat‐affected zone were η precipitates as well as Guinier‐Preston zones formed during post‐weld natural aging. The small recrystallized grains were observed in the thermo‐mechanically affected zone next to the stir zone. A W‐shaped hardness distribution where soft region was produced in the heat‐affected zone at a short distance from the stir zone were obtained. Hardness profiles of the welds were explained by precipitate distributions. Friction stir welding resulted in the reversion and coarsening of η′ precipitates. The formation of Guinier‐Preston zones in the stir zone and some parts of the heat‐affected zone during post‐weld natural aging increased the hardness. In transverse tensile specimens, fracture occurred in a location with the minimum hardness at either advancing or retreating side randomly. Further, influences of welding parameters on mechanical properties were investigated. 相似文献
17.
Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties. 相似文献
18.
J. Chen C.S. Li L.Q. Chen L. Fang S.B. Huo 《Materialwissenschaft und Werkstofftechnik》2019,50(1):33-43
The strength and toughness of 1000 MPa grade steel plate for hydropower station treated by different reheated quenching temperatures were investigated. With the increasing of reheated quenching temperature, the yield strength and tensile strength increase sharply, whereas the value of impact toughness decreases slowly. The lath martensite with high density dislocations enhances dislocation strengthening. On the contrary, the acicular or block ferrite (soft phase) produced by intercritical quenching reduces the phase transformation strengthening. Moreover, the ferrite has a low solubility of interstitial carbon due to the body‐centered‐cubic lattice structure. The bar‐shaped precipitates occur during the isothermal holding at the intercritical temperature and it will reduce the precipitation strengthening. The ferrite phase and high misorientation boundaries are the main factors that contribute to the toughening of the experimental steel. The lower the reheated quenching temperature is, the higher proportion of ferrite and high misorientation boundaries becomes. Considering the requirements for mechanical properties of 1000 MPa grade steel plate for hydropower station, the optimal temperature of reheated quenching is ～920 °C. 相似文献