This paper addresses the tensile and flexural strength of HPC (high performance concrete). The aim of the paper is to analyse the efficiency of models proposed in different codes. In particular, three design procedures from: the ACI 318 [1], Eurocode 2 [2] and the Model Code 2010 [3] are considered. The associations between design tensile strength of concrete obtained from these three codes and compressive strength are compared with experimental results of tensile strength and flexural strength by statistical tools. Experimental results of tensile strength were obtained in the splitting test. Based on this comparison, conclusions are drawn according to the fit between the design methods and the test data. The comparison shows that tensile strength and flexural strength of HPC depend on more influential factors and not only compressive strength.
To improve mechanical properties and increasing useful life of metal pieces, different methods of welding are used for repairing surface
crack of metal pieces. In this research, performance of flame welding method by spraying pure iron powder evaluated for repairing surface
grooves of structural steel. First, four specimens including one control specimen and other three specimens grooved specimens in depth of
1mm and in length of 12.5mm and groove width in the sizes of 0.5, 0.75 and 1mm.were prepared then, powder melted using oxyacetylene
reducing flame and spraying iron powder in the flame path and attached to the inner surface of the groove and finally, the specimen
repaired. Results showed that after repairing surface groove, tensile strength of the repaired specimens were reached to the tensile strength
of control specimen with the margin of 2.5%.
Light-weight Self-Compacting Concrete (LWSCC) might be the answer to the increasing construction requirements of slenderer and more heavily reinforced structural elements. However there are limited studies to prove its ability in real construction projects. In conjunction with the traditional methods, artificial intelligent based modeling methods have been applied to simulate the non-linear and complex behavior of concrete in the recent years. Twenty one laboratory experimental investigations on the mechanical properties of LWSCC; published in recent 12 years have been analyzed in this study. The collected information is used to investigate the relationship between compressive strength, elasticity modulus and splitting tensile strength in LWSCC. Analytically proposed model in ANFIS is verified by multi factor linear regression analysis. Comparing the estimated results, ANFIS analysis gives more compatible results and is preferred to estimate the properties of LWSCC.
Mechanical and technological properties of castings made from 3xx.x alloys depend mainly on properly performed process of melting and
casting, structure of a casting and mould, as well as possible heat treatment. Precipitation processes occurring during the heat treatment of
the silumins containing additives of Cu and/or Mg have effect on improvement of mechanical properties of the material, while choice of
parameters of solutioning and ageing treatments belongs to objectives of research work performed by a number of authors. Shortened heat
treatment, which is presented in the paper assures suitable mechanical properties (Rm), and simultaneously doesn’t cause any increase of
production costs of a given component due to long lasting operations of the solutioning and ageing. Results of the research concern effects
of the solutioning and ageing parameters on the Rm tensile strength presented in form of the second degree polynomial and illustrated in
spatial diagrams. Performed shortened heat treatment results in considerable increase of the Rm tensile strength of the 320.0 alloy as early
as after 1 hour of the solutioning and 2 hours of the ageing performed in suitable.
Metal pieces wear out due to variable loading, because cracks formed on their surface of them. In order to increase useful life of metal
pieces with the help of different methods of welding, surface cracks are repaired. In this research, performance of the diffusion welding of
pure iron powder through magnetic induction evaluated for repairing structural steel surface cracks. First, four specimens prepared
including one control specimen and other three specimens grooved specimens in length of 6.25mm and in depth of 1mm and groove
width in the sizes of 0.5, 0.75 and 1mm. Then by a coil, the induced current created in the piece surface. After crossing the current, the
powder melted and the groove repaired due to diffusion welding. To prevent oxidation, the atmosphere inside the coil filled with argon
gas. The results show that after repairing surface groove, tensile strength of the repaired specimens reached to the tensile strength of
control specimen with the margin of 7.5%.
In this study, high performance magnesium-yttria nanocomposite’s room temperature, strength and ductility were significantly enhanced by the dispersion of nano-sized nickel particles using powder blending and a microwave sintering process. The strengthening effect of the dispersed nano-sized nickel particles was consistent up to 100°C and then it gradually diminished with further increases in the test temperature. The ductility of the magnesium-yttria nanocomposite remained unaffected by the dispersed nano-sized nickel particles up to 100°C. Impressively, it was enhanced at 150°C and above, leading to the possibility of the near net shape fabrication of the nanocomposite at a significantly low temperature.
Heat treatment processes, due to qualitative requirements for the cast machinery components and restrictions on energy consumption resulting on the one hand from environmental concerns, and on the other hand from a requirements coming from minimization of manufacturing costs, are resulting in searching after a technologies enabling obtainment of satisfactory results, in form of improved mechanical properties mainly, while minimizing (limiting) parameters of successive operations of the heat treatment. Heat treatment of the T6 type presented in this paper consists in operations of heating of investigated alloys to suitably selected temperature (range of this temperature was evaluated on the base of the ATD method), holding at such temperature for a short time, and next rapid cooling in water (20 oC) followed by artificial ageing, could be such technology in term s of above mentioned understanding of this issue. Performed T6 heat treatment with limited parameters of solutioning operation resulted in visible increase in tensile strength Rm of AlSi7Mg, AlSi7Cu3Mg and AlSi9Cu3(Fe) alloys.
Activated tungsten inert gas (ATIG) welding has a good depth of penetration (DOP) as compared to the conventional tungsten inert gas (TIG) welding. This paper is mainly focused on ATIG characterization and mechanical behavior of aluminum alloy (AA) 6063-T6 using SiO2 flux. The characterization of the base material (BM), fusion zone (FZ), heat affected zone (HAZ) and, partially melted zone is carried out using the suitable characterization methods. The weld quality is characterized using ultrasonic-assisted non-destructive evaluation. A-scan result confirms that the ATIG welded samples have more DOP and less bead width as compared to conventional TIG. The recorded tensile strength of ATIG with SiO2 is better than the conventional TIG welding. The failure mode is ductile for ATIG welding with larger fracture edges and is brittle in the case of conventional TIG welding.
Plastic obtained from the discarded computers, televisions, refrigerators, and other electronic devices is termed as e-plastic waste. E-plastic waste is non-biodegradable waste. This paper focuses to investigate the replacement of fine aggregate with plastic aggregate obtained from e-plastic. The paper presents a detailed comparison of concrete properties (i.e.: compressive strength, tensile strength, flexural strength, density and workability) for normal concrete and concrete containing e-plastic fine aggregates. The testing was conducted according to the ASTM standards. 28-day Compressive, Flexural and Split tensile strengths were determined. In addition to the effect of e-plastic fine aggregate, silica fume is added as an admixture to find the effect on strengths. Authors have performed a compressive, flexural and tensile test of concrete mix with various percentages of e-plastic aggregates (i.e., 0, 5, 10, 15 and 20%) and silica fume (i.e.: 0, 5 and 10%) and concrete densities are also considered. It has been concluded that an increase in the e-plastic fine aggregate results in reduction in densities, compressive, flexural and tensile strength values. However, when we add silica fume to the concrete mixture it leads to strength values similar to the control mixture. The optimum obtained concrete blend contained 5% e-plastic fine aggregates and 10% silica fume. The addition of silica fume in concrete mixtures increases the 28-day compressive, flexural and tensile strengths. Moreover, the density of concrete decreases with the increase in the e-plastic aggregates.
In this paper an attempt to determine the relationship between the electrical resistivity and the tensile strength and hardness of cast iron of
carbon equivalent in the range from 3.93% to 4.48%. Tests were performed on the gray cast iron for 12 different melts with different
chemical composition. From one melt poured 6 samples. Based on the study of mechanical and electro-resistive determined variation
characteristics of tensile strength, hardness and resistivity as a function of the carbon equivalent. Then, regression equations were
developed as power functions describing the relationship between the resistivity of castings and their tensile strength and hardness. It was
found a high level of regression equations to measuring points, particularly with regard to the relationship Rm=f(ρ). The obtained
preliminary results indicate the possibility of application of the method of the resistance to rapid diagnostic casts on the production line,
when we are dealing with repeatable production, in this case non variable geometry of the product for which it has been determinated
before a regression equation.
Very well-known advantages of aluminum alloys, such as low mass, good mechanical properties, corrosion resistance, machining-ability,
high recycling potential and low cost are considered as a driving force for their development, i.e. implementation in new applications as
early as in stage of structural design, as well as in development of new technological solutions. Mechanical and technological properties of
the castings made from the 3xx.x group of alloys depend mainly on correctly performed processes of melting and casting, design of a
mould and cast element, and a possible heat treatment.
The subject-matter of this paper is elaboration of a diagrams and dependencies between parameters of dispersion hardening (temperatures
and times of solutioning and ageing treatments) and mechanical properties obtained after heat treatment of the 356.0 (EN AC AlSi7Mg)
alloy, enabling full control of dispersion hardening process to programming and obtaining a certain technological quality of the alloy in
terms of its mechanical properties after performed heat treatments. Obtained results of the investigations have enabled obtainment of a
dependencies depicting effect of parameters of the solutioning and ageing treatments on the mechanical properties (Rm, A5 and KC impact
strength) of the investigated alloy. Spatial diagrams elaborated on the basis of these dependencies enable us to determine tendencies of
changes of the mechanical properties of the 356.0 alloy in complete analyzed range of temperature and duration of the solutioning and
ageing operations.
The paper presents the results of research of impact strength of aluminum alloy EN AC-44200 based composite materials reinforced with
alumina particles. The research was carried out applying the materials produced by the pressure infiltration method of ceramic preforms
made of Al2O3 particles of 3-6m with the liquid EN AC-44200 Al alloy. The research was aimed at determining the composite resistance
to dynamic loads, taking into account the volume of reinforcing particles (from 10 to 40% by volume) at an ambient of 23°C and at
elevated temperatures to a maximum of 300°C. The results of this study were referred to the unreinforced matrix EN AC-44200 and to its
hardness and tensile strength. Based on microscopic studies, an analysis and description of crack mechanics of the tested materials were
performed. Structural analysis of a fracture surface, material structures under the crack surfaces of the matrix and cracking of the
reinforcing particles were performed.
In the knock-out process, as well as in the preliminary phase of moulding sand reclamation, the issue of energy demand for the process of crushing used sand agglutinations, preferably to single grains, is particularly important. At present, numerical values of moulding sand impact resistance, which would allow energy-related aspects of this process to be forecast, are not known, as such research has not been carried out. It seems that impact resistance tested on very small cross-section samples, which allows us to very precisely reveal some unique features of a moulding sand with organic and inorganic binders, is an important parameter, which so far has not been taken into account for evaluation of mechanical properties of moulding sands. Preliminary attempts to determine impact resistance of moulding sands have been carried out as part of own research of the author. The conducted investigations aimed at determining the relationships between the obtained values of tensile strength and impact resistance of moulding sands. In addition, the effect of holding samples at temperatures of 100oC, 200oC, 300oC on the value of impact resistance was determined, both for sands made with fresh and with reclaimed sand grains.
Heat treatment of a casting elements poured from silumins belongs to technological processes aimed mainly at change of their mechanical
properties in solid state, inducing predetermined structural changes, which are based on precipitation processes (structural strengthening of
the material), being a derivative of temperature and duration of solutioning and ageing operations. The subject-matter of this paper is the
issue concerning implementation of a heat treatment process, basing on selection of dispersion hardening parameters to assure
improvement of technological quality in terms of mechanical properties of a clamping element of energy network suspension, poured from
hypoeutectic silumin of the LM25 brand; performed on the basis of experimental research program with use of the ATD method, serving
to determination of temperature range of solutioning and ageing treatments. The heat treatment performed in laboratory conditions on a
component of energy network suspension has enabled increase of the tensile strength Rm and the hardness HB with about 60-70%
comparing to the casting without the heat treatment, when the casting was solutioned at temperature 520 o
C for 1 hour and aged at
temperature 165 o
C during 3 hours.
In this study, ODS ferritic stainless steels were fabricated using a commercial alloy powder, and their microstructures and mechanical properties were studied to develop the advanced structural materials for high temperature service applications. Mechanical alloying and uniaxial hot pressing processes were employed to produce the ODS ferritic stainless steels. It was revealed that oxide particles in the ODS stainless steels were composed of Y-Si-O, Y-Ti-Si-O, and Y-Hf-Si-O complex oxides were observed depending on minor alloying elements, Ti and Hf. The ODS ferritic stainless steel with a Hf addition presented ultra-fine grains with uniform distributions of fine complex oxide particles which located in grains and on the grain boundaries. These favorable microstructures led to superior tensile properties than commercial stainless steel and ODS ferritic steel with Ti addition at elevated temperature.
The paper deals with the accuracy of measurements of strains (elongation and necking) and stresses (tensile strength) in static room-temperature tensile strength tests. We present methods for calculating measurement errors and uncertainties, and discuss the determination of the limiting errors of the quantities measured for circular and rectangular specimens, which is illustrated with examples.
This paper presents a new welding quality evaluation approach depending on the analysis
by the fuzzy logic and controlling the process capability of the friction stir welding of
pipes (FSWoP). This technique has been applied in an experimental work developed by
alternating the FSW of pipes process major parameters: rotation speed, pipe wall thickness
and travel speed. variable samples were friction stir welded of pipes using from 485 to 1800
rpm, 4–10 mm/min and 2–4 mm for the rotation speed, the travel speed, and the pipe wall
thickness respectively. DMAIC methodology (Defining, Measuring, Analyzing, Improving,
Control) has been used as an approach to analyze the FSW of pipes, it depends on the
attachment potency and technical commonplace demand of the FSW of pipes process.
The analysis controlled the Al 6061 friction stir welded joints’ tensile strength. To obtain
the best tensile strength, the study determined the optimum values for the parameters from
the corresponding range.
The article presents the results of research concerning the effect of anthracite dust with 10%, 20%, 30%, 40% and 50% content in composites with a polypropylene matrix on selected properties. Hardness was examined with the Shore’s D method; stiffness, tensile strength as well as (MFR) Melt Flow Rate and (MVR) Melt Volume Rate of the investigated material were evaluated; wettability of the obtained material was also determined. Surface and volume resistivity were also investigated; the thermal properties of the filler were determined by thermogravimetric analysis (TGA). It was found that the investigated polypropylene composites filled with anthracite dust are hydrophobic materials and the composite hardness and stiffness are growing along with the volumetric increase of anthracite. It was noted that anthracite reinforces the material to a limited extent.