Effect of WC-10%Co-4%Cr coating on the Ti-6Al-4V alloy fatigue strength

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of several TIG weld repairs on the axial fatigue strength of AISI 4130 aeronautical steel-welded joints

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Flexural Strength of Glass-Infiltrated Zirconia/Alumina-Based Ceramics and Feldspathic Veneering Porcelains

Purpose: To compare the flexural strength of two glass-infiltrated high-strength ceramics and two veneering glass-ceramics.Materials and Methods: Four ceramic materials were tested: two glass-infiltrated high-strength ceramics used as framework in metal-free restorations [In-Ceram Zirconia IZ (Gr1) and In-Ceram Alumina IA (Gr2)], and two glass-ceramics used as veneering material in metal-free restorations [Vita VM7 (Gr3) and Vitadur-alpha (Gr4)]. Bar specimens (25 x 5 x 2 mm(3)) made from core ceramics, alumina, and zirconia/alumina composites were prepared and applied to a silicone mold, which rested on a base from a gypsum die material. The IZ and IA specimens were partially sintered in an In-Ceram furnace according to the firing cycle of each material, and then were infiltrated with a low-viscosity glass to yield bar specimens of high density and strength. The Vita VM7 and Vitadur-alpha specimens were made from veneering materials, by vibration of slurry porcelain powder and condensation into a two-part brass Teflon matrix (25 x 5 x 2 mm(3)). Excess water was removed with absorbent paper. The veneering ceramic specimens were then removed from the matrix and were fired as recommended by the manufacturer. Another ceramic application and sintering were performed to compensate the contraction of the feldspar ceramic. The bar specimens were then tested in a three-point bending test.Results: The core materials (Gr1: 436.1 +/- 54.8; Gr2: 419.4 +/- 83.8) presented significantly higher flexural strength (MPa) than the veneer ceramics (Gr3: 63.5 +/- 9.9; Gr4: 57.8 +/- 12.7).Conclusion: In-Ceram Alumina and Zirconia were similar statistically and more resistant than VM7 and Vitadur-alpha.

Multivariate analysis in the maximum strength performance

This study performed an exploratory analysis of the anthropometrical and morphological muscle variables related to the one-repetition maximum (1RM) performance. In addition, the capacity of these variables to predict the force production was analyzed. 50 active males were submitted to the experimental procedures: vastus lateralis muscle biopsy, quadriceps magnetic resonance imaging, body mass assessment and 1RM test in the leg-press exercise. K-means cluster analysis was performed after obtaining the body mass, sum of the left and right quadriceps muscle cross-sectional area (Sigma CSA), percentage of the type II fibers and the 1RM performance. The number of clusters was defined a priori and then were labeled as high strength performance (HSP1RM) group and low strength performance (LSP1RM) group. Stepwise multiple regressions were performed by means of body mass, Sigma CSA, percentage of the type II fibers and clusters as predictors' variables and 1RM performance as response variable. The clusters mean +/- SD were: 292.8 +/- 52.1 kg, 84.7 +/- 17.9 kg, 19249.7 +/- 1645.5 mm(2) and 50.8 +/- 7.2% for the HSP1RM and 254.0 +/- 51.1 kg, 69.2 +/- 8.1 kg, 15483.1 +/- 1 104.8 mm(2) and 51.7 +/- 6.2 %, for the LSP1RM in the 1RM, body mass, Sigma CSA and muscle fiber type II percentage, respectively. The most important variable in the clusters division was the Sigma CSA. In addition, the Sigma CSA and muscle fiber type II percentage explained the variance in the 1RM performance (Adj R-2 = 0.35, p = 0.0001) for all participants and for the LSP1RM (Adj R-2 = 0.25, p = 0.002). For the HSP1RM, only the Sigma CSA was entered in the model and showed the highest capacity to explain the variance in the 1RM performance (Adj R-2 = 0.38, p = 0.01). As a conclusion, the muscle CSA was the most relevant variable to predict force production in individuals with no strength training background.

Flexural strengthening of reinforced concrete beams with carbon fibers reinforced polymer (CFRP) sheet bonded to a transition layer of high performance cement-based composite

Resistance to corrosion, high tensile strength, low weight, easiness and rapidity of application, are characteristics that have contributed to the spread of the strengthening technique characterized by bonding of carbon fibers reinforced polymer (CFRP). This research aimed to develop an innovate strengthening method for RC beams, based on a high performance cement-based composite of steel fibers (macro + microfibers) to be applied as a transition layer. The purpose of this transition layer is better control the cracking of concrete and detain or even avoid premature debonding of strengthening. A preliminary study in short beams molded with steel fibers and strengthened with CFRP sheet, was carried out where was verified that the conception of the transition layer is valid. Tests were developed to get a cement-based composite with adequate characteristics to constitute the layer transition. Results showed the possibility to develop a high performance material with a pseudo strain-hardening behavior, high strength and fracture toughness. The application of the strengthening on the transition layer surface had significantly to improve the performance levels of the strengthened beam. It summary, it was proven the efficiency of the new strengthening technique, and much information can be used as criteria of projects for repaired and strengthened structures.

On loader productivity, rock strength and explosive energy in metal mining

Twenty production blasts in two open pit mines were monitored, in rocks with medium to very high strength. Three different blasting agents (ANFO, watergel and emulsion blend) were used, with powder factors ranging between 0.88 and 1.45 kg/m3. Excavators were front loaders and rope shovels. Mechanical properties of the rock, blasting characteristics and mucking rates were carefully measured. A model for the calculation of the productivity of excavators is developed thereof, in which the production rate results as a product of an ideal, maximum, productivity rate times an operating efficiency. The maximum rate is a function of the dipper capacity and the efficiency is a function of rock density, strength, and explosive energy concentration in the rock. The model is statistically significant and explains up to 92 % of the variance of the production rate measurements.

High temperature nanoindentation behavior of Al/SiC multilayers

Nanoscale Al/SiC composite laminates have unique properties, such as high strength, high toughness, and damage tolerance. In this article, the high-temperature nanoindentation response of Al/SiC nanolaminates is explored from room temperature up to 300_C. Selected nanoindentations were analyzed postmortem using focused ion beam and transmission electron microscopy to ascertain the microstructural changes and the deformation mechanisms operating at high temperature.

Compilation and evaluation of results from high-performance concrete bridge projects /

"HRDI-06/10-06(1M)E"--p. [4] of cover.

Nitrogen balance for an agroforestry system irrigated with saline, high nitrogen effluent

Land disposal is commonly used for urban and industrial wastewater, largely due to the high costs involved in alternative treatments or disposal systems. However, the viability of such systems depends on many factors, including the composition of the effluent water, soil type, the plant species grown, growth rate, and planting density. The objective of this study is to establish whether land disposal of nitrogen (N) rich effluent using an agroforestry system is sustainable, and determine the effect of irrigation rate and tree planting density on the N cycle and subsequent N removal. We examined systems for the sustainable disposal of a high strength industrial effluent. The challenge was to leach the salt, by using a sufficiently high rate of irrigation, while simultaneously ensuring that N did not leach from the soil profile. We describe the N balance for two plant systems irrigated with effluent, one comprising Eucalyptus tereticornis and Eucalyptus moluccana and a Rhodes grass (Chloris gayana) pasture, and the other, Rhodes grass pasture alone. Nitrogen balance was assessed from N inputs in effluent and rainfall, accumulation of N in the plant biomass, changes in soil N storage, N loss in run-off water, denitrification and N loss to the groundwater by deep-drainage. Biomass production was estimated from allometric relationships derived from yearly destructive harvesting of selected trees. The N content of that biomass was then calculated from measured N content of the various plant parts, and their mass. Approximately 300 kg N/ha/yr was assimilated into tree biomass at a planting density of 2500 tree/ha of E. moluccana. In addition to tree assimilation, pasture growth between the tree rows, which was regularly harvested, contributed substantially to N uptake. If the trees were harvested after two years of growth and grass harvested regularly, biomass removal of N by the mixed system would be about 700 kg N/ha/yr. The results of this study show that the current system of effluent disposal is not sustainable as the nitrate leaching from the soil profile far exceeds standards set out by the ANZECC guidelines. Hence additional means of N removal will need to be implemented. Biological N removal is an area that warrants further studies as it is aimed at reducing N levels in the effluent before irrigation. This will complement the current agroforestry system.

Fracture toughness of some high density PM steels

Tensile strengths, impact energies, and fracture toughness data are presented for pure Fe-0.5 C, Astaloy A with 0.2 and 0.6%C, and for Distaloy AB-0.6%C at relative densities of about 0.9, achieved by conventional pressing and sintering, and at close to 1.0, achieved by powder forging. At low relative density, properties are controlled by sizes of sinter necks; it is postulated that toughness scales as (x/a)4, x/a being the ratio of neck diameter to particle diameter. At high relative density, microvoid coalescence and good toughness is observed for low strength microstructures whereas cleavage and poor toughness is a concomitant of high strength.

The effects of material variations in high value manufacturing industries

It has never been easy for manufacturing companies to understand their confidence level in terms of how accurate and to what degree of flexibility parts can be made. This brings uncertainty in finding the most suitable manufacturing method as well as in controlling their product and process verification systems. The aim of this research is to develop a system for capturing the company’s knowledge and expertise and then reflect it into an MRP (Manufacturing Resource Planning) system. A key activity here is measuring manufacturing and machining capabilities to a reasonable confidence level. For this purpose an in-line control measurement system is introduced to the company. Using SPC (Statistical Process Control) not only helps to predict the trend in manufacturing of parts but also minimises the human error in measurement. Gauge R&R (Repeatability and Reproducibility) study identifies problems in measurement systems. Measurement is like any other process in terms of variability. Reducing this variation via an automated machine probing system helps to avoid defects in future products.Developments in aerospace, nuclear, oil and gas industries demand materials with high performance and high temperature resistance under corrosive and oxidising environments. Superalloys were developed in the latter half of the 20th century as high strength materials for such purposes. For the same characteristics superalloys are considered as difficult-to-cut alloys when it comes to formation and machining. Furthermore due to the sensitivity of superalloy applications, in many cases they should be manufactured with tight tolerances. In addition superalloys, specifically Nickel based, have unique features such as low thermal conductivity due to having a high amount of Nickel in their material composition. This causes a high surface temperature on the work-piece at the machining stage which leads to deformation in the final product.Like every process, the material variations have a significant impact on machining quality. The main cause of variations can originate from chemical composition and mechanical hardness. The non-uniform distribution of metal elements is a major source of variation in metallurgical structures. Different heat treatment standards are designed for processing the material to the desired hardness levels based on application. In order to take corrective actions, a study on the material aspects of superalloys has been conducted. In this study samples from different batches of material have been analysed. This involved material preparation for microscopy analysis, and the effect of chemical compositions on hardness (before and after heat treatment). Some of the results are discussed and presented in this paper.

Evaluation of applying retaining shield rotor for high-speed interior permanent magnet motors

This paper proposes a novel rotor structure for high-speed interior permanent magnet motors to overcome huge centrifugal forces under high-speed operation. Instead of the conventional axial stacking of silicon-steel laminations, the retaining shield rotor is inter-stacked by high-strength stainless-steel plates to enhance the rotor strength against the huge centrifugal force. Both mechanical characteristics and electromagnetic behaviors of the retaining shield rotor are analyzed using finite-element method in this paper. Prototypes and experimental results are demonstrated to evaluate the performance. The analysis and test results show that the proposed retaining shield rotor could effectively enhance the rotor strength without a significant impact on the electromagnetic performance, while some design constraints should be compromised.

Novel hybrid columns made of ultra-high performance concrete and fiber reinforced polymers

The application of advanced materials in infrastructure has grown rapidly in recent years mainly because of their potential to ease the construction, extend the service life, and improve the performance of structures. Ultra-high performance concrete (UHPC) is one such material considered as a novel alternative to conventional concrete. The material microstructure in UHPC is optimized to significantly improve its material properties including compressive and tensile strength, modulus of elasticity, durability, and damage tolerance. Fiber-reinforced polymer (FRP) composite is another novel construction material with excellent properties such as high strength-to-weight and stiffness-to-weight ratios and good corrosion resistance. Considering the exceptional properties of UHPC and FRP, many advantages can result from the combined application of these two advanced materials, which is the subject of this research. The confinement behavior of UHPC was studied for the first time in this research. The stress-strain behavior of a series of UHPC-filled fiber-reinforced polymer (FRP) tubes with different fiber types and thicknesses were tested under uniaxial compression. The FRP confinement was shown to significantly enhance both the ultimate strength and strain of UHPC. It was also shown that existing confinement models are incapable of predicting the behavior of FRP-confined UHPC. Therefore, new stress-strain models for FRP-confined UHPC were developed through an analytical study. In the other part of this research, a novel steel-free UHPC-filled FRP tube (UHPCFFT) column system was developed and its cyclic behavior was studied. The proposed steel-free UHPCFFT column showed much higher strength and stiffness, with a reasonable ductility, as compared to its conventional reinforced concrete (RC) counterpart. Using the results of the first phase of column tests, a second series of UHPCFFT columns were made and studied under pseudo-static loading to study the effect of column parameters on the cyclic behavior of UHPCFFT columns. Strong correlations were noted between the initial stiffness and the stiffness index, and between the moment capacity and the reinforcement index. Finally, a thorough analytical study was carried out to investigate the seismic response of the proposed steel-free UHPCFFT columns, which showed their superior earthquake resistance, as compared to their RC counterparts.

Effect of heat treatment on reactivity-strength of alkali-activated natural pozzolans

Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment to synthesize high performance cementitious construction materials with low environmental impact. The nature of the starting materials including mineral composition, chemical composition and crystal structure groups affects the formation of the geopolymer gel phase. In this paper, the pozzolanic activities of five natural pozzolans are studied. From XRD and XRF results, most of the raw materials contain zeolite clay minerals and have a high loss on ignition. Therefore, before use, samples were calcined at 700, 800 and 900 °C, respectively. The improvement in pozzolanic properties was studied following heat treatment including calcinations and/or elevated curing temperature by using alkali solubility and compressive strength tests. The results show that pozzolan containing sodium zeolite clinoptilolite can be used to prepare a moderate to high strength binder by heat treatment and calcinations can impart disorder hornblende as a constituent of pozzolan with no amorphous phase to prepare a moderate strength binder.

Improvements to the design of Litesteel Beams undergoing lateral distortional buckling

An Australian manufacturer has recently developed an innovative group of cold-formed steel hollow flange sections, one of them is LiteSteel Beams (LSBs). The LSB sections are produced from thin and high strength steels by a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. They have a unique geometry consisting of rectangular hollow flanges and a relatively slender web. The LSB flexural members are subjected to lateral distortional buckling effects and hence their capacities are reduced for intermediate spans. The current design rules for lateral distortional buckling were developed based on the lower bound of numerical and experimental results. The effect of LSB section geometry was not considered although it could influence the lateral distortional buckling performance. Therefore an accurate finite element model of LSB flexural members was developed and validated using experimental and finite strip analysis results. It was then used to investigate the effect of LSB geometry. The extensive moment capacity data thus developed was used to develop improved design rules for LSBs with one of them considering the LSB geometry effects through a modified slenderness parameter. The use of the new design rules gave higher lateral distortional buckling capacities for LSB sections with intermediate slenderness. The new design rule is also able to accurately predict the lateral distortional buckling moment capacities of other hollow flange beams (HFBs).