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The article presents a detailed analysis of the degradation phenomena and mechanisms of selected forging punches made of UNIMAX tool steel. Analyzed punches are used in the manufacture of a constant velocity joint boot forging (CVJB) applied in motorcars with front axle drive. The thorough analysis concerned the punches used in the fourth forging operation after a multi-operational process of forging at elevated temperatures, due to the lowest durability equaling only 4000 forgings. A comparison was made of 5 variants of surface thermo-chemical treatment including 2 types of nitriding (with a low and high potential) and 2 different coatings: CrN and AlCrTiN as well as a punch with and without additional thermo-chemical treatment. The performed complex analysis included a macroscopic analysis combined with scanning of the working surfaces, numerical modeling, microstructural tests, SEM microscopic tests, and microhardness measurements. The obtained results make it possible to select of the optimal variant of thermo-chemical surface treatment which improves the durability of these tools. In particular, the analysis included the manner and areas of wear of the punches as well as their resistance to the particular degradation mechanisms. [ABSTRACT FROM AUTHOR]

This paper presents a numerical methodology based on Euler-Bernoulli theory to simulate the steel, reinforced concrete and composite structures 2D nonlinear behavior. The displacement-based numerical formulation uses the principles of the Refined Plastic Hinge Method (RPHM) to simulate the concentrated plasticity at the corotational finite element nodal points. In order to present a more realistic simulation of the axial and flexural stiffness degradation, the RPHM is coupled with the Strain Compatibility Method (SCM), where the materials constitutive relations are used explicitly. The SCM is also applied in determining the structural elements’ bearing capacity. Moreover, the present approach is not limited to a specific cross-sectional typology. Also addressed are residual stress models; these are introduced explicitly in subareas of steel profiles generated by a two-dimensional cross-sectional discretization. It should be emphasized that this study considers full interaction between the materials. Finally, the results obtained are compared with numerical and experimental findings available in the literature. [ABSTRACT FROM AUTHOR]

The fiber coating is the key part of the solid-phase microextraction (SPME) technique, and it determines the sensitivity, selectivity, and repeatability of the analytical method. In this work, amine (NH)-functionalized material of Institute Lavoisier (MIL)-53(Al) nanoparticles were successfully synthesized, characterized, and applied as the SPME fiber coating for efficient sample pretreatment owing to their unique structures and excellent adsorption properties. Under optimized conditions, the NH-MIL-53(Al)-coated fiber showed good precision, low limits of detection (LODs) [0.025-0.83 ng L for synthetic musks (SMs) and 0.051-0.97 ng L for organochlorine pesticides (OCPs)], and good linearity. Experimental results showed that the NH-MIL-53(Al) SPME coating was solvent resistant and thermostable. In addition, the extraction efficiencies of the NH-MIL-53(Al) coating for SMs and OCPs were higher than those of commercially available SPME fiber coatings such as polydimethylsiloxane, polydimethylsiloxane-divinylbenzene, and polyacrylate. The reasons may be that the analytes are adsorbed on NH-MIL-53(Al) primarily through π- π interactions, electron donor-electron acceptor interactions, and hydrogen bonds between the analytes and organic linkers of the material. Direct immersion (DI) SPME-gas chromatography-mass spectrometry methods based on NH-MIL-53(Al) were successfully applied for the analysis of tap and river water samples. The recoveries were 80.3-115% for SMs and 77.4-117% for OCPs. These results indicate that the NH-MIL-53(Al) coating may be a promising alternative to SPME coatings for the enrichment of SMs and OCPs. [ABSTRACT FROM AUTHOR]

This work reports the influences of helix angle on tool performances of titanium aluminum nitride (TiAlN)- and diamond-like carbon (DLC)-coated carbide end mills for dry side milling of 304L stainless steel. The study results revealed that the number of axis contact points and effective cutting length increased with increasing helix angle, leading to less tool wear and thinner milled chips but higher workpiece temperature. In addition, DLC-coated tools exhibited relatively high workpiece temperature, rapid chipping wear due to thermally induced graphitization, and chip-built-up on side edge while TiAlN-coated end mills displayed less severe abrasive wear on cutting and side edges. Moreover, the DLC-coated end mill with a high helix angle of 60° gave the lowest surface roughness of 0.26 μm within the cutting length of 20 m while the corresponding TiAlN-coated tools offered longer tool cutting length of more than 50 m with comparable surface finish. Consequently, the TiAlN-coated end mill with a high helix angle of 60° offered high-quality surface finish with long tool life time and would be more useful for dry milling of stainless steels. [ABSTRACT FROM AUTHOR]

The 9Cr-1Mo steel (ASTM P91) was hot-dip aluminized, and its microstructural changes during oxidation were studied. Before oxidation, the coating consisted of (Al-rich topcoat containing a small amount of Al5Fe2 and Al13Fe4)/(Al13Fe4-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer containing a small amount of Al9Cr4precipitates), from the surface. During oxidation at 700-900 ±C for 20-100 h, Al diffused inward and the substrate elements migrated outward to broaden and soften the coating, and also to transform (high Al)-Fe intermetallics to (low Al)-Fe intermetallics. The phases in the coating progressively transformed during oxidation as follows; (Al-rich topcoat)/(Al5Fe2-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer)→(α-Al2O3 scale)/(Al13Fe4-rich, Al5Fe2-containing layer)/(Al5Fe2 layer)/(AlFe interlayer)→(α-Al2O3 scale)/(AlFe-rich, Al5Fe2-containing layer)/(AlFe layer)/(AlFe3 layer))→((α-Al2O3, Fe2O3)-mixed scale)/(AlFe3 layer)/(Fe(Al) layer) from the surface. As the oxidation progressed, the scale changed from α-Al2O3 to the (α-Al2O3, Fe2O3)-mixture, which provided the necessary oxidation resistance. [ABSTRACT FROM AUTHOR]

Empty hat sections, single and double, made of steel are frequently encountered in automotive body structural components such as front rails, B-Pillar, and rockers of unitized-body cars. These closed-section thin-walled components can play a significant role in terms of impact energy absorption during collisions thereby protecting occupants of vehicles from potential or severe injury. With the need for higher fuel economy and due to stringent emission norms, auto manufacturers are aggressively looking for means to reduce a vehicle's weight either by employing materials lighter than steel (such as aluminum, fiber-reinforced composites, etc.) or by substituting traditional mild steel-based body parts with those made with high strength steel of lower gages, or through a combination of both the strategies mentioned. Reducing gages, however, may lead to structural instability due to early inelastic buckling. This phenomenon of instability provides an opportunity for using polyurethane (PU) foam in structural members. Once a hollow structural member is filled with PU foam, it delays the local buckling mechanism and leads to higher strength of the structure. The current study explores the effect of PU foam-based reinforcement of tubular structures. Here, both empty and PU foam-filled single-hat and double-hat components are tested under quasi-static axial loading in a UTM. The resulting load-displacement responses are compared. Higher energy absorption as well as mean load is observed for foam-filled hat sections. Moreover, for a given total folded length, more folds are observed in foam-filled hat sections as compared to empty hat sections. Experimentally obtained half fold lengths for double-hat sections are compared with analytical predictions of the same for square tubes. Furthermore, quasi-static axial crush behaviors of single- and double-hat section components are predicted through finite element modeling and analysis using the explicit non-linear LS-DYNA code. [ABSTRACT FROM AUTHOR]

Ballistic impact of typical armour steel plate of medium thickness by ogive-nosed projectiles travelling with ordnance velocities has been investigated through numerical simulations. Johnson-Cook material and failure models have been used to simulate the behavior and failure of the material under impact conditions. The model constants have been derived from an experimental work done by the authors published previously. Simulation has been done in Altair-HyperWorks FE package. The stages of penetration have been predicted. The residual velocities, ballistic limit velocity andperforation times have been determined from the simulation results and found to match with experimental data. [ABSTRACT FROM AUTHOR]

The majority of multistory steel framed buildings in the UK are designed such that the connections between the frame elements can be classified as ‘simple’ or ‘semi-rigid’. Current UK design provisions relating to structural integrity and robustness for these types of connections do not currently incorporate dynamic effects such as inertia or strain rate sensitivity. A numerical study has been carried out on a typical UK beam-column simple connection, in which the supported beam connects into the web of the supporting column. The connection has been subjected to a rapid rotation using the finite element software package LS-DYNA. Results and discussion of the numerical study are presented herein; experimental validation of these results is currently being carried out. [ABSTRACT FROM AUTHOR]

This work presents the results of a numerical and theoretical study on the cold-formed steel built-up sections under axial compression, to explore the buckling Behavior and ultimate capacity of built-up sections. The built-up sections have been formed by two identical lipped channels placed back to back connect by using spacers. The Finite element model is developed by using the ABAQUS software. The developed numerical model is verified against the experimental results published in the literature. After validation, the parametric study is conducted by varying the overall slenderness, depth, and number of spacers. The column strength obtained from numerical analysis are compared with the strength predicted by using the Direct Strength Method (DSM) and Effective Width Method (EWM) as per North American Specifications (AISI-S100:2007) for cold-formed steel members. [ABSTRACT FROM AUTHOR]

Bio-/environment-friendly cationic gemini surfactant, ethane-1,2-diyl bis( N, N-dimethyl- N-hexadecylammoniumacetoxy)dichloride, referred to as 16- E2-16, was synthesized and characterized. Corrosion inhibition effects of 16- E2-16 on mild steel (MS) surface in 1 M HCl solution at 30, 40, 50 and 60 °C were evaluated using gravimetric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT-IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor-Fe] on the surface of MS was confirmed by UV-visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corrosion inhibition effects of 16- E2-16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the efficiency of the compound with its intrinsic molecular parameters. [ABSTRACT FROM AUTHOR]

Though the mechanical properties of shape-memory alloys (SMAs) make them a promising material for reinforcement in concrete structures, their electrochemical behavior in concrete environments has not previously been studied. This study investigated the influence of galvanic coupling between a nickel-titanium (Ni-Ti)–based SMA and a low-carbon steel on their corrosion performance in simulated concrete pore solution. Three measurement cells were considered: SMA alone, low-carbon steel alone, and one with the coupled SMA and carbon steel. The specimens were immersed in the chloride-free pore solution for 20 days and then 3% by weight of NaCl was added to the solution. The specimens were then kept in the chloride-contaminated solution for 70 days. The corrosion resistances of the specimens were assessed by different electrochemical measurement techniques. The results of the electrochemical experiments showed a significant increase in corrosion activity of the coupled specimens compared with that for other measurement cells. [ABSTRACT FROM AUTHOR]

Given that the modern world cannot be conceived without the existence of the steel and its use, the crude steel consumption may be considered as an indicator characterizing the economic development of a country. The purpose of this paper is to establish the evolution of the world, regional and state consumption of crude steel, both per total, as well as per inhabitant, but also the impact of the economic and financial crisis it had on the evolving evolution of using the crude steel. Data subject to the study are related to the period 2004 - 2014 and concern nine regions of development and ten countries. [ABSTRACT FROM AUTHOR]

The paper describes experimental aspects for composite steel-concrete columns, with steel encased profile. In composite columns with HSC case, even if elastic displacement vy decreases, the value of the lateral force Hy corresponding to the vy displacement and the maximum lateral loading Hmax indicates a significant increase. Failure modes were different, characterized by sudden and violent concessions due to cracking developments through aggregate in columns with HSC, while columns with NSC shows a "slow" failure mode characterized by gradual decline of bearing capacity with the growth of the displacements. It is well known that the high strength concrete is more susceptible to fragile failure than the normal concrete, so it is, in a way, the presumed result. On the other hand, from the graphics and parameters analysis we can conclude that the columns with HSC have a higher energy absorption capacity, which can recommend this solution to the construction in seismic areas, even the failure mode was brittle. In structural terms, composite columns with concrete class C70/85 provide obvious better performances to structures, having significant increases to almost all analyzed parameters. The solution of fully encased composite column is a competitive solution for seismic and non-seismic zones, due to the excellent seismic performances (resulted from the presented experimental tests) and also because of improved fire protection. The results obtained on the columns made with high strength concrete showed improved performances, especially resistance. Due to the brittle fracture of the high strength concrete more experimental and numerical research must still be made. [ABSTRACT FROM AUTHOR]

Superaustenitic stainless steel 654SMO was used as the experimental material to investigate the effect of heating temperatures and holding times on grain growth behavior in the temperature range of 1150-1250 °C and holding time ranging from 15 to 60 min. The contour maps of grain size and grain growth rate as a function of temperatures and times were plotted. The results of this study suggest that grains grow with parabolic trend. Grain size and its growth rate increase with increasing heating temperature, the former also increases with holding time, while the latter decreases with holding time. Both grain size and grain growth rate are more sensitive to holding time than solution temperature at temperatures below 1200 °C, which is contrary to that of at temperatures above 1200 °C. The growth behavior of grains in the tested steel is illustrated by a modified mathematical model deduced on the basis of previous empirical models, and this modified grain growth model can fit well with the experimental grain growth data obtained during solution treatment. [ABSTRACT FROM AUTHOR]

On the basis of hot rolling practice, the effects of thermomechanical control process parameters on the evolution of austenite grain size before the deformation at non-recrystallization zone were investigated in detail. The inflections in the strain hardening rate versus true stress curves show that the dynamic recrystallization (DRX) has initiated for different deformation conditions studied in the present work. But the volume fractions of the equiaxed grains in the specimens which were immediately water quenched to room temperature after deformation are different from each other. Moreover, the main refinement mechanisms for different deformation conditions have been differentiated. It is interesting to note that the austenite grain size can be refined significantly with increasing the strain from 0.0 to 0.5 for different deformation temperatures. However, when the strain increases to 0.8, the austenite grain size cannot be further refined for the higher deformation temperature range, while the austenite grain size can be further refined for the lower deformation temperature range. In addition, the effect of strain rate on the austenite grain refinement is vigorous for the higher deformation temperatures. Moreover, the empirical equation to estimate the austenite grain size for different deformation parameters was established. [ABSTRACT FROM AUTHOR]

This paper presents pin-ended compression tests on steel equal angles. Three nominal section sizes were tested. Detailed measurements of material properties, residual stresses, and geometrical imperfections were conducted. The pin ended specimens were tested with a minimal eccentricity ofL/1,000 applied about the minor axis to cause compression at the tips of the legs. The test data are compared with the Indian specifications for hot-rolled steel structures. The section capacities obtained from the column tests are found to be between 15 and 40% higher than those calculated according to the specifications. It is concluded that there is no need to include the additional eccentricity specified in the steel structures standards accounting for the shift of the effective centroid, and that the eccentricity ofL/1,000, specified for all section classes, should be applied to slender sections only. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of technological and composition factors on the structure and quality of ordinary and quality steels for processing forged crankshaft. It is known that influencing factors which determine the properties of ordinary steels are the carbon content and the microstructure. Beside the predominant effects due to the carbon content and the microstructure, the properties of ordinary steels can be modified by the effects of the residual elements (in addition to carbon, manganese, silicon, sulfur and phosphorus that are always present). The properties of steel can be influenced by the presence of gas, particularly oxygen, nitrogen and hydrogen, as well as by the reaction products thereof. These secondary elements usually penetrate the steel from the used scrap, deoxidants or furnace environment. The gas content depends largely on the method used to melt, on the deoxidation and casting, so that the final properties of these steels depend largely on the method used in their preparation. Thus, the factors that condition the steel properties are primarily the carbon content and its microstructure, which is largely determined by the chemical composition and the subsequent final processing of forging or by the heat treatment operations. Secondly, these properties depend on the residual elements of the alloy, non-metallic inclusions and gas content of the steel, which in turn depends on the steelmaking method. [ABSTRACT FROM AUTHOR]

For some powertrain components deep penetration laser welding is considered very advantageous and prospective joining technology. Presented article focuses on heterogeneous laser welds of two widely used materials, ductile iron with pearlitic matrix (e.g. differential carrier) and Cr-Mo low alloy steel (e.g. gears). When homogeneous welds without filler wire are done, both materials show poor laser weldability, because unacceptable welding defects, mainly cracks, are created in the weld. In ductile iron, almost under all welding conditions, cracks in WM and HAZ due to brittle phases (cementite and martensite) are created. Low alloy Cr-Mo steel creates under all welding conditions solidification cracks and microcracks, caused by solidification. Even though homogenous welds of both materials are unacceptable, for heterogeneous welds possibility to create sound welds was found. By mixing of materials approximately 1:1 substantial amount of retained austenite is present in the WM, helping to suppress creation of brittle cracks and also partially suppress solidification cracks. To supress solidification cracks completely, full penetration welds and welds with V shape were used. Also use of Ni filler wire proved successful to create sound welds. The weld joint strength for heterogeneous welds for both used solutions was about 450 N/mm², which is less than BM strength, yet acceptable. Occurring phenomena connected with ration of materials mixing and its influence on WM properties, structure and behaviour is explained. [ABSTRACT FROM AUTHOR]

Existence of hollow sections in precast hollow core wall makes it sceptical to resist earthquake loading. However, this wall can resist earthquake loading if it is designed as a hybrid wall system. It is equipped with unbonded tendons and bonded "fuse-bars" to dissipate energy. It rocks steel-on-steel without inducing any structural damages. In-plane lateral cyclic loading is applied on the wall. Experimental results show that the wall is able to resist earthquake loading without any structural damage. Direct displacement based approach is used to validate the experimental results. There are good correlations between them with very a small percentage of discrepancies. [ABSTRACT FROM AUTHOR]

Abstract: Holding yokes made of investment cast 17-4PH stainless steel were too soft (below 20HRC). Optical microscopy of the parts showed that there is a high fraction of retained austenite after oil quench due to high amount of molybdenum found in parts as an impurity. Subzero treatment in liquid nitrogen after solution heat treating was used to convert retained austenite to martensite but parts became too brittle and fractured during post-heat treating machining. Double and triple aging at 538°C (1000°F) after subzero cooling was done on parts. Detailed fractography and tensile testing along with optical microscopy (OM) investigation proved that repeated aging at 538°C (1000°F) led to lower strain microstructure and improved elongation without reduction in tensile strength. Tensile and non-destructive testing after machining proved that problem has been solved. [Copyright &y& Elsevier]