bluuebunny/crossref_metadata_2025 huggingface dataset:
Groove Angles Influence on Mechanical and Microstructural Properties of P460N Steel in SMAW
Authors: Pezeshkian Rouhollah Mohsen , Shayanfar Peyman , Shafaiepour Saiedeh
Published: March 2014

This study investigates mechanical and microstructural properties of P460N steel after Shielded Metal Arc Welding (SMAW). Three specimens with groove angles of 45 °, 60 ° and 75° were prepared and welded for this purpose. Tensile strength test, impact test, grain size test, macro and micro hardness test and metallographic test were performed on weld metal (WM), Heat Affected Zone (HAZ) and Base Metal (BM) and the results were compared. In the specimen with groove angle of 60°, yield strength was more than the base metal. Impact energy results in HAZ were different, so that HAZ areas in the specimens with 45° and 60° groove angles have less impact energy compared to the base metal but in the specimen with 75° groove angle, impact energy was more than the base metal. This increase can be due to formation of intermetallic compounds. After checking mechanical and microstructural properties of all the specimens, the groove angle of 60° was confirmed to be used at designing and construction of a reservoir with thickness of 14mm and working pressure of 40 bars.
A Review of Damage Tolerant Design, Certification and Repair in Metals Compared to Composite Materials
Authors: Chowdhury Nabil , Chiu Wing Kong , Wang John
Published: March 2014

A review of some of the various fatigue models introduced over the years for both metallic materials, in particular aluminium alloys followed by fatigue and durability concerns associated with composite materials. The move towards light weight and high stiffness structures that have good fatigue durability and corrosion resistance has led to the rapid move from metal structures to composite structures. With this brings the added concern of certifying new components as the damage mechanisms and failure modes in metals differ significantly than composite materials such as carbon fiber reinforced polymers (CFRP). The certification philosophy for composites must meet the same structural integrity, safety and durability requirements as that of metals. Hence this is where the challenge now lies. Substantial work has been conducted in the reparability of composite structures through bonding using various adherend thicknesses and joint types and has been shown to have higher durability than mechanically fastened repairs for thin adherends however these are currently unacceptable repair methods as they cannot be certified. Repairs are designed on the basis that the repair efficiency can be predicted and should be designed conservatively with respect to the various failure modes and include the surrounding structure.
Stiffness Based Fatigue Characterisation of CFRP
Authors: Brunbauer Julia , Arbeiter Florian , Stelzer Steffen , Pinter Gerald
Published: March 2014

This paper investigates the possibility of determining damage under fatigue loading in carbon fibre reinforced plastics (CFRP) by using mechanical stiffness. Therefore, stress-strain-hysteresis recorded in fatigue tests under sinusoidal loads are used for moduli calculation. Additionally, a new method for stiffness evaluation called cyclic tensile tests is presented. Its results are compared to results from hysteresis analysis and to actual damage mechanisms monitored non-destructively with thermography analysis.
Fatigue Crack Growth Rate in Mode I of a Carbon Fiber 5HS Weave Composite Laminate Processed via RTM
Authors: Shiino Marcos Yutaka , Alderliesten Rene C. , Pitanga Midori Yoshikawa , Cioffi Maria Odila Hilário
Published: March 2014

Delamination or crack propagation between plies is a critical issue for structural composites. In viewing this issue and the large application of woven fabrics in structural applications, especially the ones that requires high drapeability to be preformed in a RTM mold cavity such as the asymmetric ones, e.g HS series, this research aimed in dynamically testing the carbon fiber 5HS/RTM6 epoxy composites under opening mode using DCB set up in order to investigate the crack growth rate behavior in an irregular surface produced by the fabric waviness. The evaluation of the energy involved in each crack increment was based on the Irwin-Kies equation using compliance beam theory. The tests were conducted at constant stress ratio of R=0.1 with displacement control, frequency of 10 Hz, in accordance to ASTM E647-00 for measurement of crack growth rate. The results showed large scatter when compared to unidirectional carbon fiber composites due to damage accumulation at the fill tows.
Fatigue Behavior of Weld Repaired AISI 4130 Aeronautic Steel Used in Critical Flight Safety Structures
Authors: do Nascimento Marcelino Pereira , Batista Carolina Cordeiro , Pereira Celso Pinto Morais , Voorwald Herman Jacobus Cornelis
Published: March 2014

Since the 1950s, fatigue is the most important project and operational consideration for both civil and military aircrafts. For some aircraft models the most loaded component is one that supports the motor: the "Motor Cradle". Because they are considered critical to the flight safety the aeronautic standards are extremely rigorous in manufacturing them by imposing a "zero index of defects" on the final weld quality (Safe Life), which is 100% inspected by Non-Destructive Testing/NDT. This study has as objective to evaluate the effects of up to four successive TIG welding repairs on the axial fatigue strength of an AISI 4130 steel. Tests were conducted on hot-rolled steel plate specimens, 0.89 mm thick, with load ratio R = 0.1, constant amplitude, at 20 Hz frequency and in room temperature, in accordance with ASTM E466 Standard. The results were related to microhardness and microstructural and geometric changes resulting fromwelding cycles.
High Cycle Fatigue Behavior and Microstructural Characterization of 6013-T4 Aluminum Alloy Laser Welded Joints
Authors: de Siqueira Rafael Humberto Mota , de Oliveira Aline C. , Riva Rudimar , Abdalla Antonio Jorge , Reis Pereira Baptista Carlos Antonio , de Lima Milton Sergio Fernandes
Published: March 2014

Laser beam welding (LBW) may be used in the place of the traditional riveting process for the welding of the stringers to the skin in aircrafts. This work intends to investigate the mechanical behavior of laser welded aluminum AA6013, subjected to post-welding heating treatments (PWHT). A fiber laser with an average power of 1.5 kW was used to weld two 1.6mm thick sheets in T-joint configuration. After welding, the samples were separated in three groups: the first just welded, the second subjected to a PWHT during 4 hours at 190°C and the third during 2 hours at 205°C. Hoop tensile tests showed that the thermal treatment at 190 oC for four hours increased the tensile strength in 76 MPa, but the strain had decreased 4%; the thermal treatment at 205 oC for two hours increased maximum strength in 65MPa, with a decrease in strain of 5%. In T-pull tensile tests, the tensile properties of as-welded and PWHT samples remained the same. Standard S-N curve showed that the welding reduce the number of cycles to failure for the tested stairs. PWHT did not affect fatigue properties.
Enhancement of Rolling Contact Wear and Fatigue Resistance of Wheel Steel by Laser Dispersed Treatment
Authors: Zeng Dong Fang , Lu Lian Tao
Published: March 2014

Ferrite-pearlite steel is the most widely used material for railway wheel. However, such wheel steel can not meet the strict demands for rolling contact wear and fatigue resistance with the rising speed and weight of traffic. The aim of this paper is to improve the rolling contact wear and fatigue resistance of wheel steel by laser dispersed treatment. Such treatment creates isolated glazed regions on the surface layer of wheel steel, which are composed of fine martensite and retained autensite and have an avera0ge hardness of 762HV0.3. Compared with the conventional laser surface treatment technologies, such as laser hardening, laser melting, or laser cladding, which have been applied for improving rolling contact wear and fatigue resistance of wheel/rail, the multiple overlapping laser tracks that cause the premature failure are avoided by laser dispersed treatment. The wear rate and rolling contact fatigue life of treated and untreated wheel steel were evaluated and compared by Amsler twin-disc testing machines in dry and lubricated condition, respectively. The test results show that laser dispersed treatment improves the rolling contact wear and fatigue resistance of wheel steel. The stable wear rate of the laser treated wheel steel is about 0.3 times that of untreated wheel disc and the average rolling contact life of treated wheel steel is about double that of the untreated steel. Further investigations show that the glazed regions suppress the plastic deformation of wheel steel. This inhibits the treated wheel steel from delamination wear and delays the formation of fatigue crack initiation.
Corrosion Fatigue Behaviour of a Common AZ91D Magnesium Alloy in Modified Simulated Body Fluid
Authors: Jafari Sajjad , Singh Raman R.K.
Published: March 2014

Use of Magnesium alloys as body implants are breaking into a new paradigm of biomedical engineering as they are biocompatible, biodegradable and have mechanical properties close to that of bone. Even though corrosion fatigue (CF) and stress corrosion cracking (SCC) failures are among the most common concerns for metallic implants, CF behaviour of magnesium alloys in physiological environments has received little attention. This article reports the CF results of a common cast magnesium alloy (AZ91D) in modified simulated body fluid (m-SBF). Results showed that there was a remarkable difference in fatigue strength of Mg alloys when tests were performed in m-SBF.
3D Numerical Study on how the Local Effective Stress Intensity Factor Range Can Explain the Fatigue Crack Front Shape
Authors: Gardin Catherine , Fiordalisi Saverio , Sarrazin-Baudoux Christine , Petit Jean
Published: March 2014

The plasticity-induced crack closure of through-thickness cracks, artificially obtained from short cracks grown in CT specimens of 304L austenitic stainless steel, is numerically simulated using finite elements. Crack advance is incremented step by step, by applying constant ΔK amplitude so as to limit the loading history influence to that of crack length and crack wake. The calculation of the effective stress intensity factor range, ΔKeff, along curved shaped crack fronts simulating real crack fronts, are compared to calculation previously performed for through-thickness straight cracks. The results for the curved crack fronts support that the front curvature is associated to constant ΔKeff amplitude, thus assumed to be the propagation driving force of the crack all along its front.
Molecular Dynamics Investigation on Shearing between Osteopontin and Hydroxyapatite in Biological Materials
Authors: Lai Zheng Bo , Yan Cheng , Oloyede Adekunle
Published: March 2014

Bone, a hard biological material, possesses a combination of high stiffness and toughness, even though the main basic building blocks of bone are simply mineral platelets and protein molecules. Bone has a very complex microstructure with at least seven hierachical levels. This unique material characteristic attracts great attention, but the deformation mechanisms in bone have not been well understood. Simulation at nanolength scale such as molecular dynamics (MD) is proven to be a powerful tool to investigate bone nanomechanics for developing new artificial biological materials. This study focuses on the ultra large and thin layer of extrafibrillar protein matrix (thickness = ~ 1 nm) located between mineralized collagen fibrils (MCF). Non-collagenous proteins such as osteopontin (OPN) can be found in this protein matrix, while MCF consists mainly of hydroxyapatite (HA) nanoplatelets (thickness = 1.5 4.5 nm). By using molecular dynamics method, an OPN peptide was pulled between two HA mineral platelets with water in presence. Periodic boundary condition (PBC) was applied. The results indicate that the mechanical response of OPN peptide greatly depends on the attractive electrostatics interaction between the acidic residues in OPN peptide and HA mineral surfaces. These bonds restrict the movement of OPN peptide, leading to a high energy dissipation under shear loading.
Experimental and Numerical Simulation Study of Plasticity-Induced and Roughness-Induced Fatigue Crack Closure
Authors: Masuda Kenichi , Ishihara Sotomi , Sugai Yuya , McEvily A.J.
Published: March 2014

In this study, fatigue crack closure behavior was investigated in the aluminum alloy 6061-T6 and the carbon steel JIS. S25C. It was found that crack closure in the aluminum alloy 6061-T6 showed the characteristics of plasticity-induced fatigue crack closure (PIFCC), whereas the carbon steel JIS. S25C showed the characteristics of roughness-induced fatigue crack closure (RIFCC). The experiments included the determination of the crack-opening levels Kop as a function of stress intensity factor range ΔK and the effect of surface removal on the crack-opening level. In order to simulate the behaviors of the plasticity-and the roughness-induced fatigue crack closure, the finite element method was adopted. The results of FEM were in good agreement with the experimental results. It was cconcluded that at a given yield strength level , a low Youngs modulus and a low work-hardening coefficient will favor PIFCC, whereas a high Youngs modulus and a high work-hardening coefficient will favor RIFCC.
Investigations on the Fatigue Crack Propagation Threshold in Very High Cycle Fatigue
Authors: Wang Chong , Wagner Danièle , Bathias Claude
Published: March 2014

Pariss law of fatigue crack propagation rate is well applied in the defect-tolerance fatigue approach. When carry out same approach in the very high cycle fatigue domain, the understanding of mechanism about fatigue crack propagation threshold which is obviously important, is helped. In the present work here, the fatigue crack propagation threshold of a surface crack for an Armco iron loaded in the VHCF regime was investigated by a new approach which combines the fracture surface analysis and the temperature recording on the surface during the test by an infra-red camera. The experiments were carried out on a sheet specimen under a 20 kHz ultrasonic frequency loading with IR images registration. Three stages of fatigue crack were identified with different mechanisms. It is found that the transition between initiation and crack propagation corresponds to the intrinsic fatigue threshold. It takes more than 99% of the gigacycle fatigue life to achieve this transition size.
Low-Cycle Fatigue Behaviour of a Ni-Based Single-Crystal Superalloy
Authors: Segersäll Mikael , Moverare Johan , Leidermark Daniel , Simonsson Kjell
Published: March 2014

In this study, low-cycle fatigue (LCF) tests at 500 °C in the <001>, <011> and <111> directions have been performed for the Ni-based single-crystal superalloy MD2. All tests were carried out in strain control with Rε=-1. The <001> direction has the lowest stiffness of the three directions and also shows the best fatigue properties in this study followed by the <011> and <111> directions, respectively. It is well recognised that Ni-based single-crystal superalloys show a tension/compression asymmetry in yield strength and this study shows that a tension/compression asymmetry also is prevalent during LCF conditions. At mid-life, the <001> direction generally has a higher stress in tension than in compression, while the opposite is true for the <011> direction. For the <111> direction the asymmetry is found to be strain range dependent. The <011> and <111> directions show a cyclic hardening behaviour when comparing cyclic stress-strain curves with monotonic stress-strain curves. In addition, the <011> and <111> directions show a serrated yielding behaviour for a number of cycles while the yielding of the <001> direction is more stable.
Mutual Interaction between Fatigue Crack Initiation/Propagation and Microstructural Features in Cast Aluminum Alloys
Authors: Krupp Ulrich , Giertler Alexander , Siegfanz Stephanie , Michels Wilhelm
Published: March 2014

The correlation between the microstructure, the mechanical properties and the fatigue life of the common aluminum cast alloy Al-7Si-0.3Mg (A356) was investigated. By variation the solution heat treatment temperatures and times the precipitation strengthening effect in the dendritic aluminum solid solution phase and the spheroidization of the eutectic silicon were modified. The results of fully reversed fatigues tests revealed an increase in the fatigue life of specimens that were heat treated at higher temperatures. This observation was supported by analyzing the fatigue crack propagation behavior using the direct current potential drop technique (DCPD). With (i) increasing heat treatment temperature, i.e., increasing dendritic α-Al strength and (ii) roundness of the eutectic silicon particles the resistance to technical fatigue crack initiation, expressed by the threshold value of the stress intensity range Kth, was shifted to higher values.
Unifying Monotonic and Hysteresis Material Properties for Notch Plasticity Analysis under Variable Amplitude Loads
Authors: Yu Xiao Bo , Liu Qian Chu , Wallbrink Chris
Published: March 2014

This study was performed in support of accurate notch plasticity analysis under variable amplitude loads. Monotonic and cyclic strain-controlled tests were performed on flat dog-bone coupons machined from 6.35mm thick 7075-T651 aluminium alloy plates. The tests with low-high-low strain amplitude transitions revealed both an instant softening following the high strain amplitude cycle and a gradual recovery during the subsequent low strain amplitude cycles. The transition from monotonic-like to hysteresis-like material behaviour was found to be consistent with an overload induced softening and recovery process. A conceptual consideration is thus proposed to unify the characterisation of monotonic and hysteresis material properties. The implications of the present finding on notch plasticity analysis are also discussed.
Simulation of Surface Crack Initiation Induced by Slip Localization and Point Defect Kinetics
Authors: Sauzay Maxime , Liu Jia
Published: March 2014

Crack initiation along surface persistent slip bands (PSBs) has been widely observed and modelled. Nevertheless, from our knowledge, no physically-based fracture modelling has been proposed and validated with respect to the numerous recent experimental data showing the strong relationship between extrusion and microcrack initiation.
Effect of Stress Ratio and Loading Mode on High Cycle Fatigue Properties of Extruded Magnesium Alloys
Authors: Shiozawa Kazuaki , Ikeda Atsushi , Fukumori Tsuyoshi
Published: March 2014

The aim of this study is to discuss an effect of stress ratio and loading mode on high cycle fatigue performances of extruded magnesium alloys. Axial loading fatigue tests under three conditions of stress ratio, R, of 0, -1 and-1.5, and also rotating bending fatigue tests have been performed in laboratory air at room temperature using hourglass shaped specimens of AZ31, AZ61, AZ80 and T5-treated AZ80 alloy. From the experimental results, some materials showed a specific stepwise S-N curve on which two knees appear. The shape of S-N diagram depended on a kind of tested materials, applied stress ratio and loading mode. It was suggested from the detail observation of fracture surface that fatigue crack initiation mechanism changed from a twin-induced failure mode at high stress amplitude level to a slip-induced one at low stress amplitude level. This transition was determined with the relation between the minimum stress during a fatigue cycle and the compressive yield stress at which deformation twin occurs.
Titanium Alloy Developments For Future Fan Disc Applications – The Fatigue Response of “Alloy 104”
Authors: Hewitt Jon S. , Thomas Matthew J. , Garratt Paul , Bache Martin R.
Published: March 2014

Alloy 104 is a novel high strength, α+β titanium alloy primarily aimed at aero-engine fan disc applications. Two microstructural variants of Alloy 104 have been assessed. Room temperature tensile strength and elongation have been investigated alongside a more detailed study of low and high cycle fatigue behaviour. The alloy clearly demonstrated an improved fatigue resistance in both microstructural conditions, whilst maintaining forgeability and a comparable density to Ti-6Al-4V. Furthermore, the alloy has been subjected to a load regime with a hold period at peak loads and proven to be insensitive to dwell fatigue.
Fatigue of Cold Expanded Open Hole Coupons with Pre-Existing Cracks
Authors: Baburamani Pud S. , Ogden Rob , Liu Qian Chu , Sharp P. Khan
Published: March 2014

Fastener holes have a high stress concentration at the edge of the hole and are primary sources of fatigue crack initiation, resulting in widespread fatigue damage leading to fatigue failures in airframe structures. The split-sleeve cold expansion (SsCx) technology is a simple and cost-effective way to improve the fatigue resistance of fastener holes by the introduction of compressive residual stresses around the holes. An investigation was carried out by DSTO to quantify the effectiveness of this technology, in terms of fatigue life improvement factors on a typical airframe aluminium alloy. Open hole (zero load transfer) coupons were tested to failure in non-cold expanded and cold expanded conditions. Coupons were also pre-cracked to specified crack lengths at the open hole, and cold expanded or left non-cold expanded, and tested to failure. This paper will present the results of the initial phases of the experimental program, involving constant amplitude fatigue loading of open hole coupons with and without cracks. The fatigue life improvement achieved by the use of hole cold expansion technology will be presented.
Helicopter Airframe Fatigue Spectra Truncation and Verification
Authors: Vine John , Krake Luther , Krieg Beau
Published: March 2014

Helicopter airframe fatigue cracking is a cause of significant and growing cost of ownership and operational readiness concerns for the operators of (primarily) metallic airframe helicopters. Airframe fatigue has often had relatively low priority for helicopters, with research and design concentrated on the fatigue of flight critical rotating structural components such as rotor blades and pitch links. The Australian Defence Science and Technology Organisation (DSTO) and Naval Air Systems Command (NAVAIR) of the US Navy are collaborating to develop improved methods and technologies that can be used to assess the fatigue damage accrued by ageing helicopter airframes. The flight load sequences, or fatigue spectra, experienced by a helicopter airframe in its lifetime contain many billions of load cycles due to rotor revolutions. The application of spectra containing such vast numbers of load cycles is often impractical for reasons of test duration and cost, therefore spectra simplification techniques must be employed. To this end, truncation is a technique that is used to eliminate non-or lesser-damaging load cycles, producing spectra equivalent in terms of theoretical fatigue damage but with substantially fewer load cycles. This paper describes several truncation techniques that have recently been developed at DSTO specifically to deal with the very large numbers of load cycles that are characteristic of helicopter airframe fatigue spectra. These techniques, which include both sequence and frequency based approaches, feature tunable levels of truncation and allow for large reductions in numbers of turning points while maintaining high-fidelity and realistic fatigue spectra. Also detailed are preliminary results from a comprehensive coupon test program, which DSTO is using to experimentally verify that truncated and un-truncated spectra are approximately equivalent in terms of the fatigue damage that they produce.
Influence of HVOF Coating on the Fatigue Strength of 15-5 PH Stainless Steel
Authors: Voorwald Herman Jacobus Cornelis , Cioffi Maria Odila Hilário , Júnior Gilson Silva
Published: March 2014

Structural component failures due to cyclic loading are associated to surface damage of materials and its interaction with environment. Fatigue failure occurs with stresses below the yield strength of each material and is a result of crack initiation and propagation. In aeronautical components is an important parameter to be considered in project, as well as the corrosion and wear resistance. Thermally sprayed HVOF coatings have been considered to replace galvanic chromium deposits with comparable performance for wear and corrosion resistance. The aim of present study is to study the influence of WC-13Co-4Cr applied by HVOF, on the axial fatigue strength of 15-5 PH stainless steel. The shot peening treatment was used to restore fatigue performance.
Effect of Thermal Barrier Coating on Low Cycle Fatigue Behavior of Cast Inconel 713LC at 900 °C
Authors: Obrtlík Karel , Hutařová Simona , Čelko Ladislav , Juliš Martin , Podrábský Tomáš , Šulák Ivo
Published: March 2014

The effect of thermal barrier coating (TBC) on low cycle fatigue behavior of cast superalloy Inconel 713 LC has been studied at 900 °C. The TBC consisting of a CoNiCrAlY bond coat and a zirconia (ZrO2) top coat stabilized by 8% yttria (Y2O3) was deposited on the gauge section of cylindrical specimens using the atmospheric plasma spray technique. Cylindrical specimens of Inconel 713LC in as-received condition and with surface treatment were cyclically strained under strain control with constant total strain amplitude in symmetrical cycle at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of coated and uncoated material were obtained. The stress response of the TBC coated specimens is lower in comparison with the uncoated specimens. Detrimental effect of surface treatment on the Basquin curve is documented. Specimen sectioning and fracture surface observations revealed fatigue damage mechanisms and help to discuss differences in fatigue behavior of the coated and uncoated superalloy.
Reduction in Fretting Fatigue Strength of Austenitic Stainless Steels due to Internal Hydrogen
Authors: Komoda Ryosuke , Yoshigai Naoto , Kubota Masanobu , Furtado Jader
Published: March 2014

Fretting fatigue is one of the major factors in the design of hydrogen equipment. The effect of internal hydrogen on the fretting fatigue strength of austenitic stainless steels was studied. The internal hydrogen reduced the fretting fatigue strength. The reduction in the fretting fatigue strength became more significant with an increase in the hydrogen content. The reason for this reduction is that the internal hydrogen assisted the crack initiation. When the fretting fatigue test of the hydrogen-charged material was carried out in hydrogen gas, the fretting fatigue strength was the lowest. Internal hydrogen and gaseous hydrogen synergistically induced the reduction in the fretting fatigue strength of the austenitic stainless steels. In the gaseous hydrogen, fretting creates adhesion between contacting surfaces where severe plastic deformation occurs. The internal hydrogen is activated at the adhered part by the plastic deformation which results in further reduction of the crack initiation limit.
Fatigue Crack Propagation Behavior of AZ61 Magnesium Alloy under Controlled Cathodic Potential
Authors: Taniguchi Tomonori , Uematsu Yoshihiko , Hatano Yuji , Kakiuchi Toshifumi , Nakajima Masaki , Nakamura Yuki
Published: March 2014

In the present study, fatigue crack propagation (FCP) tests on Mg alloy, AZ61, were performed in 3% NaCl solution. The cathodic potential was controlled to achieve the hydrogen charged condition without anodic dissolution to figure out the effect of hydrogen on FCP behavior. The cathodic potential was set to be-3.0V, which corresponds to the immunity region without corrosion reaction based on Pourbaix diagram of Mg. The FCP rates were accelerated under hydrogen charged condition compared to those in dry air. Magnesium hydrides, MgH2, were not detected along the crack wake in the measurement by X-ray Diffraction (XRD) method, suggesting that the acceleration could be attributed to the diffusion of hydrogen atoms.
The Effect of Crack Growth Retardation when Comparing Constant Amplitude to Variable Amplitude Loading in an Aluminium Alloy
Authors: Burchill Madeleine , Barter Simon A. , Jones Michael
Published: March 2014

It has often been observed that the growth of short fatigue cracks under variable amplitude (VA) cyclic loading is not well predicted when utilising standard constant amplitude (CA) crack growth rate/stress intensity data (da/dN v DK). This paper outlines a coupon fatigue test program and analyses, investigating a possible cause of crack growth retardation from CA-only testing. Various test loading spectra were developed with sub-blocks of VA and CA cycles, then using quantitative fractography (QF) the sub-block crack growth increments were measured. Comparison of these results found that, after establishing a consistent uniform crack front using a VA load sequence, the average crack growth rate then progressively slowed down with the number of subsequent CA load cycles applied. Further fractographic investigation of the fracture surface at the end of each CA and VA sub-block crack growth, identified significant crack front morphology differences. Thus it is postulated that a variation or deviation from an efficient crack path is a driver of local retardation in short crack growth during CA loading. This may be a source of error in analytical predictions of crack growth under VA spectra loading that may need to be considered in addition to other potential effects such as less closure whilst cracks are small. For aircraft designers, using solely CA data for fatigue life predictions this may result in non-conservative estimates of total crack fatigue life, producing unexpected failures or an increased maintenance burden.
Fatigue Crack Growth in a Precipitation-Hardened Martensitic Stainless Steel: Influence of Ageing, Temperature and Loading History
Authors: Aboumou Loic Dimithe , Hénaff Gilbert , Arzaghi Mandana , Pommier Sylvie
Published: March 2014

The 15-5PH (precipitation-hardened) martensitic stainless steel is prone to embrittlement following ageing during service at temperatures between 300°C and 350°C. This results in an increase in strength and a decrease in elongation and fracture toughness. However little information is available on the consequences of long term ageing on fatigue crack growth resistance. In the present study this issue is precisely addressed at room temperature and 300°C, with different load ratio under constant amplitude loading and under variable amplitude loading.At room temperature, the results indicate a marginal effect of the load ratio, regardless of ageing conditions and temperature. While the Paris regime is not affected by ageing, a significant drop in the critical stress intensity value before unstable fracture is observed, reflecting a decrease in fracture toughness of the material with ageing. At 300°C, the FCGRs are higher than at room temperature for all ageing conditions. Variable amplitude loading tests carried out on differently-aged materials showed the same retardation effect.
Laser Shock Peening on a 6056-T4 Aluminium Alloy for Airframe Applications
Authors: Glaser Daniel , Polese Claudia , Bedekar Rachana D. , Plaisier Jasper , Pityana Sisa , Masina Bathusile , Mathebula Tebogo , Troiani Enrico
Published: March 2014

Laser Shock Peening (LSP) is a material enhancement process used to introduce compressive residual stresses in metallic components. This investigation explored the effects of different combinations of LSP parameters, such as irradiance (GW/cm2) and laser pulse density (spots/mm2), on 3.2 mm thick AA6056-T4 samples, for integral airframe applications. The most significant effects that are introduced by LSP without a protective coating include residual stress and surface roughness, since each laser pulse vaporizes the surface layer of the target. Each of these effects was quantified, whereby residual stress analysis was performed using X-ray diffraction with synchrotron radiation. A series of fully reversed bending fatigue tests was conducted, in order to evaluate fatigue performance enhancements with the aim of identifying LSP parameter influence. Improvement in fatigue life was demonstrated, and failure of samples at the boundary of the LSP treatment was attributed to a balancing tensile residual stress.
Analysis of the Fiber Density in Bamboo Guadua angustifolia Kunth by Extended Field Microscopy and High Resolution Images Processing
Authors: Torres Edgar , Plata Arturo , Díaz Germán , Takeuchi Caori
Published: March 2014

The fiber density per cross section of the Bamboo Guadua Angustifolia Kunth (GAK) was calculated by digital images processing. Three processes were done in the development of this work: preparation of the samples, digital pre-processing of the images acquired, and digital processing of the images acquired. For the preparation of the samples, the polishing with different abrasive papers and wool were done, and afterwards, it was added revealing ink on surface to make better the contrast between the fiber zones. The digital pre-processing of the images was based on the acquisition of sequences of images, doing a sweeping of the samples using an automatic plate. The digital processing consisted in the generation of panoramas with sequences of images acquired from the sample. The cross section fiber density was obtained by the calculus of the reason between digital measurement of the total area of the fibers and the total area of the sample. Finally, the values obtained for the fiber density were: 0.34, 0.41 and 0.43 for bottom, middle and top part of the culm respectively.
Connection Efficiency of Wood-Concrete Structural Floor System
Authors: Sá Ribeiro Ruy Alexandre , Sá Ribeiro Marilene Gomes
Published: March 2014

The wood-concrete research project uses medium to high density reclaimed tropical hardwoods from the Brazilian Amazon region and steel rods scraps from a construction site. The beams studied are composed of a bottom layer of staggered wood boards and a top layer of concrete. The wood members are laterally nailed together to form a wide beam, and horizontal rebar connectors are installed before the concrete layer is applied on top. Wood-concrete layered beams with horizontal rebar connectors were tested in third-point loading flexural bending. An improvement on the previously conceived connection detail for a composite wood-concrete structural floor system was achieved. The new layout of the horizontal rebar connectors added more strength and higher composite efficiency for the beams tested. Further analysis is suggested to optimize the connection parameters in terms of spacing and number of connectors. Composite wood-concrete decks can attend a large demand for pedestrian and road bridges in rural areas, as well as residential and commercial slabs.
Evaluation of Compatibility between Sugarcane Straw Particles and Portland Cement
Authors: Beraldo Antônio L. , Payá J. , Monzó J.M.
Published: March 2014

Brazilian agro industries generate several types of crop residues and most of them show interesting properties for cement composite production. Among these residues, actually sugarcane straw particles (SCSP) are available in a great amount as a by-product of the sugarcane industries. However, residual sugar and other chemical products remain in the materials structure. In the most of the cases, these compounds inhibit cement setting. The aim of this research work was to evaluate, by means the hydration curve methodology, the performance of several treatments applied to the SCSP. Results indicated that mineralization was the most effective treatment and allows appropriate cement setting for the composite. SCSP treated by soaking in sodium silicate solution at 4%, followed by a second soaking in aluminum sulfate at 10%, showed an appropriate cement setting. Keywords: cement composite, hydration curve, chemical treatment, mineralization, agricultural waste
Hardened Properties of Lime Based Mortars Produced from Kaolin Wastes
Authors: de Azerêdo Aline Figueirêdo Nóbrega , Carneiro Arnaldo Manoel Pereira , de Azeredo Givanildo Alves , Sardela Mauro
Published: March 2014

Many studies have been developed about the use of wastes as construction materials. The higher volume of waste generated by many types of industries has caused many environmental problems. Most of these wastes have not been placed in adequate sites, or even been reused. In Brazil the industries that produces kaolin generates a lot of wastes. Studies have been carried out on the use of kaolin wastes as replacement material for Portland cement concretes and mortars; and only few ones have studied it in hydraulic mortars for restoration of historical buildings. In this work kaolin wastes were studied as pozzolanic and inert material in lime mortars. Two lime/metakaolin ratios and different proportions of kaolin wastes as replacement of river sand were studied. Hardened properties of these mortars like compressive and tensile strength and water absorbed by capillarity were evaluated up to 180 days of curing. Microstructural characteristics also were assessed using thermal analysis (TG/DTG) and x-rays diffraction (XRD). Some mortars presented the highest strengths at 90 days of curing, and at 180 days their resistances dropped. The major phases found by microstructural analysis were monocarboaluminate (C4ACH11) and calcium carbonate (CaCO3).
Influence of Recycled Aggregate on the Rheological Behavior of Cement Mortar
Authors: Lima Paulo Roberto Lopes , Toledo Filho Romildo Dias , Gomes Otávio da Fonseca Martins
Published: March 2014

In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order to generate more homogeneous fine aggregates. The characterization of the natural and recycled sands was carried out through physical tests, X-ray diffraction, scanning electron microscopy (SEM), and image analysis (shape and texture description parameters). A conventional mortar and three mortars containing recycled sands were produced with a sand/cement ratio of 4 and consistency index of 255±5 mm. The consistency was kept constant by ranging the water-cement ratio from 0.58 to 1.14. The rheological study was performed using a rotating viscometer to obtain torque-rotation ratio and to calculate the yield stress and plastic viscosity. The results indicate that the presence of recycled aggregate causes a lowering of both yield stress and plastic viscosity with respect to the mortar containing natural aggregate.
Introducing Bamboo in the Education of the Building Engineer
Authors: Steenput Gie
Published: March 2014

If we believe there is a crisis regarding global warming, pollution, and social injustice, and if we want to act on it, we need to open our minds, change our attitudes, and start preparing with our young students. Together we need to develop a way of thinking that implies the use of a new set of values that differs from today’s mind-set and values that caused this crisis in the first place.With this in mind we proposed a group of students and professors to consider building structures with an alternative material: bamboo, a material with which neither students nor professors had any experience in. During the course of this exercise the conceived structures developed from simple to complex designs, from required forms to free ones designed by the students, from small 1:100 scaled models to bigger 1:20 ones.Not theory but the practice itself generated a tremendous amount of enthusiasm within the group of students and within the group of professors. Knowledge of the stability of skeletal structures was gained in a playful way; theoretical thinking-errors were immediately tested by the practical execution of the newly developed model. The existence of alternative construction materials, in this case bamboo, the feel for the material and its numerous possibilities for construction purposes were being revealed! For the involved students and professors the practical aspects of this exercise created more awareness and knowledge on the topic than any theoretical lecture could.
The Influence of Fine Sand from Construction-Demolition Wastes (CDW) in the Mortar Properties
Authors: Jochem Lidiane Fernanda , Rocha Janaíde Cavalcante , Cheriaf Malik
Published: March 2014

A fine fraction of recycled aggregates from the processing of construction and demolition waste (CDW), have a very effective potential use in mortar as a partial fine aggregate replacement for natural sand, an also contribute to the development of sustainable materials, specifically to produce coating mortar. This paper presents the results of a study using recycled aggregate in mortar as a replacement for natural sand, analyzing the effects of pre-wetting and the performance in mortar composition with a fine sand (1.2/ 0.15 mm). In this study was investigated the behavior of recycled aggregate dry and wet previously until to saturated surface dry condition (reaching this value by capillary absorption test of the granulometric prepared curve). Five different compositions have been defined, varying the quantity of fine and determined the physical properties of recycled aggregate. Then the mortars were prepared and evaluated in the fresh state: specific gravity, water retention and workability, and in the hardened state: hygrothermal and mechanical properties. The results showed that the wetting of the aggregate affects the properties of the mortar, as well the addition of fines. There is an advantage when is realized wetting of the recycled aggregate CDW. The addition of fine in mortars must be controlled, and the fine aggregates improved the almost properties and in excess can reduce the hygrothermals properties.
New Process for Peanut Husks Panels: Incorporation of Castor Oil Polyurethane Adhesive and Different Particle Sizes
Authors: Gatani Mariana , Granero Victoria , Medina Juan Carlos , Fiorelli Juliano , Lerda Josefina , Sipowicz Eugenia , Kreiker Jerónimo
Published: March 2014

New materials are being developed for architectural and design purposes. The recycling of waste is presented as an opportunity for new applications based on increased industrial waste and raw material shortages. Seeking an alternative to wooden panels, regional waste without sustainable disposal is being used as inputs in the production of lignocellulosic panels. We present the results of two experiments. The first one consists in the development of peanut husks ground-treated and untreated panels made in order to determine the influence of different particle sizes, shapes and their combinations, aiming to the physical and mechanical characterization of compact panels properties. In the second experiment, compact panels with whole peanut husks were made with polyurethane resin using castor oil painting. The object of this study was to analyze the influence of this new resin, without formaldehyde emissions, in the resulting panels physical and mechanical properties. It was concluded that the smaller particles had a positive influence in the panels physical-mechanical properties, and that the property characterization of panels made with castor oil resin was satisfactory for use in interior furniture. Peanut husks panels show good prospects for their integration in the field of design and architecture.
Building Components Made from Recycled Plastics
Authors: Gaggino Rosana , Arguello Ricardo Gustavo
Published: March 2014

The problem being investigated was to develop an economical, environmentally friendly, and quality panel made from recycled plastics. The objective of this work was to contribute to decontaminating the environment, and to solving the housing shortage in our country. The developed products were panels for housing and equipment. They were manufactured by recycling plastic materials from food, perfumery or cleaning packaging, waste production from factories due to failures in sheet thickness or ink application. It thus contributes to decontaminating the environment, since most of this waste is buried in municipal land without any use, or accumulated and burned in landfills, causing environmental degradation. The technical properties of these panels were established by laboratory testing. A comparison was made between their main technical properties and other conventional panels made with wood particles, available in the is panel does not swell under water, unlike conventional panels. The percentage of water absorption is lower than that of conventional panels. The flexural resistance is is almost equal to that of an uncoated particle board. The density is higher than that of conventional panels made with wood particles. The components obtained have environmental advantages with regard to other conventional ones, since they reduce plastic waste that causes pollution, instead of using up natural resources.
Mechanical Performance of Asphalt Mixtures with Natural Aggregates and Recycled Aggregates for Surface Course
Authors: Marques Vagner da Costa , de Queiroz Bismak Oliveira , de Lacerda Diego Meira , Gouveia Antônio Marcos de Araújo , de Melo Ricardo Almeida
Published: March 2014

The recycled aggregates of construction and demolition solid waste can be used on pavements to decrease environmental impacts in cities. Thus, this study aimed to compare the mechanical performance of asphaltic mixtures made with natural aggregates and concrete recycled aggregates for surface course of pavements. The materials were collected in an asphalt mixing plant and in a construction and demolition solid waste recycling plant located in João Pessoa/PB, Brazil. The Marshall asphalt mix design was chosen to determine optimum asphalt content and evaluate mechanical performance of asphaltic mixtures. The asphalt mixtures specimens were composed of natural aggregates, and afterwards of recycled aggregates with percent contents of 25, 50 and 100. The optimum asphalt contents were 5.7 and 7.5%, Marshall stability of 1,070 and 790 Kgf, flow of 6.2 and 5.7 mm for natural aggregate asphalt mixtures and asphalt mixtures with 25% recycled aggregates, respectively. Moreover, percent air voids and percent voids filled with asphalt met the Brazilian DNIT: ES 031/2006 specified standard. However, the asphalt mixtures with 50 and 100% recycled aggregates did not meet the specified standard. Therefore, it was concluded that the replacement of natural aggregates with 25% recycled concrete aggregates in asphalt mixtures can be technically viable to build asphalt surface course on pavements, besides lowering pavement costs and decreasing environmental impacts.
Home for Elderly People Built by the Community with Structural Elements of Laminated Bamboo Guadua in a Rural Area of Colombia
Authors: Luna Patricia , Takeuchi Caori
Published: March 2014

In the past four years the research project "Design and construction of housing with structural elements of bamboo guadua laminated" was developed in order to show the potential of industrial use of this material and to increase its demand for housing construction. As a result of the research, in the village of Ibama in the municipality of Yacopi, Department of Cundinamarca, Colombia, a home for elderly people was built using structural elements of laminated bamboo guadua, with the participation of the community under the supervision of the Universidad Nacional de Colombia (National University of Colombia). This paper presents the steps followed: the architectural and structural design based on the experimental results of samples and elements, the manufacture process, the test of a part of the structure and the construction on site.