Main Damage Mechanisms Research Articles

Running condition and material response fretting maps of incoloy 800 steam generator tubes against AISI 304L pads in air and room temperature

Abstract Running Condition and Material Response Fretting Maps of Incoloy 800 steam generator tubes against AISI 304 L were determined in air at room temperature. Tests were performed up to 106 cycles using displacement amplitudes between 5 and 50 μm and normal contact loads in the range 5–20 N. The regimes identified were Partial Slip (PSR), Gross Slip (GSR) and Mixed Fretting (MFR). In PSR only slight surface damage corresponding to a false brinelling effect of the contacting surfaces was detected. In MFR, fretting wear associated with particle detachment was identified as the main damage mechanism, while the formation of cracks was not detected. In GSR, fretting wear was predominant. Detached debris in GSR were agglomerates of (Ni,Fe)(Fe,Cr)2O4 with sizes between 5 and 20 nm.

Computational framework for analysis of contact-induced damage in brittle rocks

This paper presents a numerical approach for predicting damage in rock materials caused by contact loading. The rock material is modelled using a constitutive description that combines pressure dependent plasticity, for capturing shear deformation under high confining pressure, with an anisotropic damage model for capturing mode I cracking in tension. Material parameters for the model are taken from a recently performed investigation on a granite material. The model has been used to simulate two types of contact loading experiments from the literature, cyclic loading and monotonic loading up to fracture. In order to achieve accurate predictions, the model has been extended to account for small loaded volumes which occur at contact loading. The results show that the main damage mechanism at cyclic loading is crack propagation due to Hertzian stresses whereas in the monotonic experiments sub-surface cracks could initiate. All features measured in the contact loading experiments are captured by the model and hence, the modelling framework is judged to be able to capture contact damage if real stone geometries are studied in FEM.

Work hardening behaviour and damage mechanisms in carbide-free bainitic steel during uni-axial tensile deformation

The study has examined the work hardening characteristics and damage mechanisms of a newly developed carbide-free bainitic steel. These are correlated with the microstructural constituents using the established empirical equations and the experimental findings. Carbide-free bainitic steel has shown primarily three stages of deformation in modified Crussard-Jaoul analysis, which best describes the work hardening behaviour. Plastic deformation of retained austenite precedes the deformation of bainitic ferrite. The blocks of retained austenite transform to strain induced martensite at lower strain levels than the films of retained austenite. With increasing strain, cross slip assisted dynamic recovery, and sub-grain formation become predominant in bainitic ferrite. Although early void initiation occurs at the non-metallic inclusions, these do not play a significant role in the final fracture. Void initiation and splitting of phase boundaries due to strain incompatibility, decohesion of prior austenite grain boundaries and cracking of martensitic-austenitic constituents are the main damaging mechanisms.

Micromechanics based FEM study on the mechanical properties and damage of epoxy reinforced with graphene based nanoplatelets

A numerical micromechanics study is performed to investigate the effect of using graphene nanoplatelets (Gnp) with theoretical maximum properties and reduced graphene oxide (rGOnp) on the mechanical properties and damage mechanism of graphene based nanocomposites. Here we consider brittle matrix cracking and interface debonding as the main damage mechanisms. The results showed that the competition between both mechanisms is affected by nanoplatelets/matrix modulus-mismatch, volume fraction, interface strength and orientation. Gnp showed improved modulus, however, with inferior strength and fracture strain compared to rGOnp. This is due to the large modulus-mismatch of Gnp, which resulted in increasing the stress concentration, matrix cracking and coalescing at lower loads. On the other side, the lower stress concentration of rGOnp allowed for higher load accumulation and increased interface debonding. Applying stronger interface properties was found to suppress the interface debonding, improving strength and fracture strain. Further, aligned nanoplatelets lead to a simultaneous improvement in modulus, strength and fracture strain. This is due to the improved load transfer and activation of toughening mechanisms observed for bioinspired nacre like structures.

Mechanical Behavior of a PBX Substitute Material under Static and Dynamic Loading

Abstract A polymer-bonded explosive substitute material (PBX) composed of sugar granules and polymer binder was fabricated with a weight proportion of 90:10. Static Brazilian tests accompanied by high-speed photography, digital image correlation (DIC) technology, and dynamic mechanical analysis (DMA) were carried out. The tensile stress-strain relation is quasi-linear until failure with a tensile strength of about 0.89 MPa, elastic modulus of 35 MPa, and Poisson’s ratio of 0.392. Microscopically, interfacial debonding and intergranular fractures are the main mechanisms of damage. By DMA, the storage modulus and tan δ show a strong dependence on temperature and less dependence on frequency; the glass transition temperature is found to be about 50°C. These results are helpful for understanding the behavior of PBX under tensile and dynamic loading.

Swing-torsion composite friction behavior of CoCrMo/UHMWPE contact interface of artificial knee joint prosthesis implantation materials

Artificial knee replacement has been widely used in clinical medicine, but the motion of the artificial knee prosthesis is very complicated in the human body. The prosthesis suffers wear which further lead to osteolysis and aseptic loosening. Therefore, the artificial knee joint prosthesis material CoCrMo and UHMWPE were studied in this paper, and the swing-torsion composite friction behavior between CoCrMo/UHMWPE contact interfaces is carried out on the artificial knee joint simulator. The tribological behavior and damage mechanism of the CoCrMo/UHMWPE contact interface were studied during the swing-torsion composite motion friction experiment. The changed trend of swing and torsion component friction coefficients in the swing-torsion composite motion are the same as that in the single swing and torsion. UHMWPE is worn more seriously in the swing-torsion composite motion. The main damage mechanism of CoCrMo in the swing-torsion composite motion is abrasive wear and the main damage mechanisms of UHMWPE is abrasive wear and fatigue wear.

Fretting Wear Behavior and Damage Mechanisms of Inconel X-750 Alloy in Dry Contact Condition.

Frictional and fretting wear behaviors of Inconel X-750 alloy against GCr15 steel ball were investigated in dry contact condition with ∼60% air humidity. Fretting tests were run at the high frequency tribosystem SRV 4 in room temperature and ball-on-flat contact configuration were adopted with the relative oscillatory motion of small displacement amplitude (40 μm). Sliding regimes, wear volumes, frictional properties, and material damage mechanisms were studied with regard to different normal loading and test durations. After the tests, the worn surface morphologies were analyzed by three-dimensional (3D) optical surface profiler, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to distinguish fretting running conditions and material responses for different test cases. It was found that the material removals by abrasive and adhesive wear, debris formation and oxidization, and wear delamination were the main damage mechanisms under the lower normal load where the full slide or gross slip regime (GSR) was dominant between the contact surfaces. On the other hand, fretting regime was found to be a stick-slip or a partial slip at greater loads where damage mechanisms were correlated with deformed asperities, fatigue cracks, and thick layer removal due to highly concentrated cyclic stresses. Time dependence was crucial during GSR where the wear volume increased substantially; however, the wear volumes and scars sizes were consistent over time because of stick-slip effects under the higher normal load.

Investigation of Formation Damage Induced During Drill-In Process of Ultradeep Fractured Tight Sandstone Gas Reservoirs

Ultradeep fractured tight sandstone gas reservoir is easy to suffer from severe formation damage during the drill-in process, yet few papers have been published on the corresponding formation damage mechanisms. This paper focuses on a typical ultradeep fractured tight sandstone reservoir in the Tarim Basin, China. Fluid sensitivity damage, phase trapping damage, and the formation damage induced by oil-based drill-in fluids were evaluated by a serious of modified experimental methods. As a supplement, the rock physics and surface property were analyzed deeply. Results showed that severe fluid sensitivity damage occurred with a decrease in fluid salinity (critical value: 3/4 formation water salinity (FWS)) and an increase in fluid pH value (critical value: pH = 7.5). The change in water film thickness, the enhancement of hydrophilia, particle detachment, and dissolution of quartz/albite under high formation temperature are the main damage mechanisms. Abnormal low water saturation, mixed wettability, abundant clay minerals, and complex pore structures are contributing to the severe phase trapping damage. The dynamic damage rate of oil-based drill-in fluids is 60.01%, and inadequate loading capacity is the main trigger of lost circulation. Finally, a formation damage control strategy was proposed, and a field test proved its feasibility.

Basic principles for structural integrity and lifetime assessment of BN-type fast reactors components with regard for material degradation

The present paper overviews the basic principles of Russian Standard elaborated by authors for justification of lifetime prolongation of BN-600 fast reactor (FR) and for justification of design lifetime of BN-800 and BN-1200 FR. These principles are based on the analysis of the main mechanisms of material embrittlement and damage under service and formulation of the limit conditions for different components of FR of BN type.

Model development of permeability impairment due to clay swelling in porous media using micromodels

Swelling and displacement of clay minerals during drilling and production of oil and gas reservoirs are among the main mechanisms of formation damage. Most reservoirs contain clay minerals, either originally deposited during sedimentation phase, or precipitated from fluids flowing through matrix. Owing to the large specific surface area of clay particles, their swelling, detachment, and migrationmay lead to permeability impairment in porous media.Therefore, an accurate interpretation of the behaviour of clay particles in the porous media may enable us to prevent and possibly reverse the respective damage mechanisms. In this work, the pore-scale swelling behaviour of clays are studied using glass micro models as porous medium and Sodium bentonite as swelling clay. By image processing technique, effective porosity of model during low salinity water (LSW) flooding are estimated. The effect of different parameters such as porous medium aspect ratio and clay concentration on permeability impairment is studied. According to this study, besides higher clay concentrations, the permeability is also affected adversely by larger aspect ratio of pore bodies. Based on our experiments, a model is developed to estimate permeability impairment by clay swelling as a function of pore geometry and clay concentration.

Effects of Cr and Nb Additions on Sliding Wear Behaviors of the FePSiB Coatings

The tribological properties of the FePSiB amorphous/nanocrystalline coatings with Cr and Nb additions were investigated in reciprocating mode against tungsten carbide friction coupling with different dry sliding conditions. The wear rates of the FePSiB-based coatings increase linearly with the normal load and sliding speed. The coatings with Cr and Nb promote the formation of successive and compact oxide film on friction surface, which decreases significantly wear rate of the coating. Nano-mechanical characterization done to map the correlation between the elastic properties and wear resistance. The main damage mechanisms of the FePSiB-based coatings under dry friction conditions are abrasion wear, delamination failure and oxidation wear.

Characterization of compressive behavior of PVC foam infilled composite sandwich panels with different corrugated core shapes

Increasing the development in industrial technology and need for energy absorption, lightweight and cost effective composite materials such as composite sandwich panels have been in the center of attention. In this paper energy absorption properties of proposed composite sandwich panels with different corrugated core geometries under quasi static out of plane loading conditions is experimentally investigated. Three different corrugated shapes, i.e. rectangular, trapezoidal and triangular fabricated with the same thickness are used. The specimens were subjected to three different quasi-static compression loading condition i.e. concentrated, linear and planar. The effect of the number of unit cells and corrugated core geometries in determining the overall deformation and local collapse behavior of the panels also investigated. Based on the comparative results, it is found that three unit cell rectangular corrugated geometry possessed the best performance than other types of corrugated core geometries. Moreover, through visual observation the damage mechanisms under loading conditions and subsequent failure modes are inspected. Plastic buckling of cell walls and foam densification identified as the initial failure modes and by continuing the loading, fiber breakage, localized delamination as well as debonding between the skins and the core were the main damage mechanisms in these corrugated systems.

Micro-Magnetic and Microstructural Characterization of Wear Progress on Case-Hardened 16MnCr5 Gear Wheels.

The evaluation of wear progress of gear tooth flanks made of 16MnCr5 was performed using non-destructive micro-magnetic testing, specifically Barkhausen noise (BN) and incremental permeability (IP). Based on the physical interaction of the microstructure with the magnetic field, the micro-magnetic characterization allowed the analysis of changes of microstructure caused by wear, including phase transformation and development of residual stresses. Due to wide parameter variation and application of bandpass filter frequencies of micro-magnetic signals, it was possible to indicate and separate the main damage mechanisms considering the wear development. It could be shown that the maximum amplitude of BN correlates directly with the profile form deviation and increases with the progress of wear. Surface investigations via optical and scanning electron microscopy indicated strong surface fatigue wear with micro-pitting and micro-cracks, evident in cross-section after 3 × 105 cycles. The result of fatigue on the surface layer was the decrease of residual compression stresses, which was indicated by means of coercivity by BN-analysis. The different topographies of the surfaces, characterized via confocal white light microscopy, were also reflected in maximum BN-amplitude. Using complementary microscopic characterization in the cross-section, a strong correlation between micro-magnetic parameters and microstructure was confirmed and wear progress was characterized in dependence of depth under the wear surface. The phase transformation of retained austenite into martensite according to wear development, measured by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) was also detected by micro-magnetic testing by IP-analysis.

Corrosion damages of flow regulation valves for water injection in oil fields

Abstract The flow regulation valves are devices commonly manufactured in AISI 316 or AISI 410 stainless steels, which are applied for water injection in petroleum exploitation. These valves have shown a significant failure rate in oil fields on shore at Sergipe, Brazil. The aim of the present study is to explain the main damage mechanisms ocurring on these valves. Therefore, a set of experiments was carried out including valves in field monitoring, water characterization, corrosion and erosion tests of the alloys under some different heat treatments. Chemical analysis, metallography and microhardness provided the alloy's characterization. Failure rate of 100% due to generalized corrosion before 60 days in test was perceived for the AISI 410 valves. Otherwise, the AISI 316 valves presented localized corrosion and failure rate of 32% before 142 days in test. Changes in the injection water content and alloy's selection alternatives are the ways to reduce the failure rate of the valves.

DUSST: Development of a new stress sweep fatigue test for asphalt mixtures

Fatigue cracking is one of the main damage mechanisms that take place in asphalt pavements. However, its evaluation during the design asphalt mixtures is not usually considered due to the complexity of the tests required, their high costs and the long time required to perform them. As a consequence, several research teams are working on developing new test procedures to reduce the time related to fatigue characterization of asphalt mixtures. In this context, this paper presents the development of a new test procedure consisting of a cyclic uniaxial tension-compression test in which the stress applied increases every 5000 cycles. In this manner, it is possible to evaluate a mixture’s response under cyclic loading at different stress levels in one test. Also, failure of the mixture takes place in a shorter time period than that required by classical time sweep fatigue tests. This paper presents results obtained in the application of this new methodology to a mixture frequently used in Chilean pavement structures (type IV-A-12 by Chilean standards) with three different asphalt binders: a conventional binder (CA-24), a high modulus binder (CA-HM) and a polymer-modified binder (CA-PM). We evaluated three different types of aggregates obtained through two different shredding processes. Results achieved in the development of our Direct Uniaxial Stress Sweep Test (DUSST) show that it is an experimental method with great potential. This test can characterize fatigue behaviors of asphalt mixtures in a shorter time by using important parameters such as initial strain, failure strain, complex modulus and dissipated energy. In addition, we obtained a good sensitivity of the DUSST main parameters to variables evaluated.

Formation damage mechanisms associated with drilling and completion fluids for deepwater reservoirs

Immense oil and gas reserves exist in the deepwater of the South China Sea, and the first priority for implementing successful drilling and completion operations without reservoir damage is to understand the damaging mechanisms to the reservoir formation. With the use of deepwater reservoir cores from the western South China Sea, the mineral composition, microstructure, porosity, and permeability characteristics of the reservoir formation were analyzed. With the use of core flow tests, potential fluid sensitivity was analyzed to determine how and which fluids can damage the reservoir formation during drilling and completion. The results show that the reservoir formation is composed of unconsolidated siltstone with a clay mineral content of 6–19%, and has high porosity and permeability with large pore throats. Sensitivity damage due to the increasing flow rate is strong, and an unusual salinity sensitivity exists with a critical salinity at 40,000–45,000 mg/L. Moderate alkali fluids sensitivity damage exists, with water sensitivity being weak. The main mechanisms of formation damage by drilling and completion fluids were analyzed as following: plugging of pore throats by solid invasion occurs because the sizes of the solid materials in the drilling fluids are just ideal for the formation of an external filter. Rock-fluid incompatibilities occur due to the increasing flow rate and salinity of the fluids because the formation rock is unconsolidated and the fines will easily detach and migrate, plugging the pore throats. Therefore, effective temporary plugging of the pore throats with a large diameter is important for protecting the reservoir. This study provides basic data for the design and implementation of reservoir protection measures in deepwater oil and gas exploration.

Printability of co-polyester using fused deposition modelling and related mechanical performance

The aim of this study is to investigate the printability conditions of a copolyester based polymer that has not received yet much attention. This material presents several advantages over PLA and ABS including its food contact compliance and BPA (Bisphenol A) free formulation. The determination of optimal conditions to print copolyester with FDM process was done by quantifying the influence of printing temperature on thermal behavior and tensile properties including Young’s modulus, yield stress, tensile strength, ultimate properties, and fracture toughness. Analysis of damage mechanisms through the observation of fracture surfaces of printed copolyester were also performed using SEM. The results indicate a strong relationship between thermal cycling, tensile properties and printing temperature. It is also shownthat the mechanical behavior of printed copolyester is significantly affected by the filament arrangement within the meso-structure. Particular fracture patterns are revealed, which suggest the simultaneous action of three main damage mechanisms triggered by the inhomogeneous change in the filament morphology at the rupture point.

Fractographic study of damage mechanisms in fiber reinforced polymer composites submitted to uniaxial compression

After the advances of microscopic techniques, the literature shows an increasing number of fractographic studies of fiber reinforced polymer composites. However, the fractographic aspects of compressive failures remain slightly explored and poorly enlightened. In this context, the purpose of this work is to present some of the main mechanisms responsible for the fracture energy absorption in the case of fiber reinforced polymer composites submitted to compressive loads. To do so, this study used an extensive literature review in addition to fractographic studies of textile carbon fiber/epoxy composite laminates, which were manufactured using prepreg scraps from the manufacturing waste of aeronautical industry. It was possible to identify the main damage mechanisms which occur in compressive failures of fiber reinforced polymer composites, namely microcracking, crack bridging, protrusions (not commonly reported in the literature) and fiber microbuckling leading to kink-band formation. Thus, we intend to contribute to a better understanding of the compressive behavior of polymer composites as well as of the resulting fractographic aspects.

Experimental study on quasi-static penetration process of cylindrical indenters with different nose shapes into the hybrid composite panels

The main aim of the present research is to investigate the quasi-static penetration process of cylindrical indenters with different nose shapes into multilayered composite panels made of Dyneema and Glass woven fibers, and aluminum face sheets. For better understanding of the perforation mechanism of the composite panels, effects of indenter geometry, stacking sequences, and boundary conditions are studied and their effects on energy absorption, specific absorbed energy, maximum deformation, peak load, and failure modes are evaluated and discussed. Samples with different layering configurations loaded under quasi-static punch and indentation with loading rate of 5 mm/min using universal testing machine and cylindrical rigid indenters with different nose shapes geometries consist of blunt, hemispherical, conical, and ogival. Regarding the boundary condition effects, two different rigid fixtures are designed and manufactured with the same external square perimeter (250 × 250 mm) and two different internal perimeters of circular and square shapes respectively, with diameter of 15 mm and edge side of 100 mm. Results show that the hybrid composite panels composed of Dyneema sheets, exhibits significantly better load carrying capacity and specific absorbed energy under both loading conditions. Indenter nose shape significantly affects elastic load, peak load, and energy absorption and maximum deformation. Furthermore, from visual observations based on digital microscopic images, fiber breakage, fiber pull out, intralaminar delamination, and debonding between the composite layers within the damage zone were inspected and recognized as the main damage mechanisms of panels. Output data obtained from all the experimental investigation were reported, discussed, and commented upon.

Evaluation of the Residual Strength of a Polyester/E-Glass Composite Tray After Exposure to High Temperatures Due to a Nearby Fire Event

The mechanical behavior of pultruded polyester/E-Glass trays was evaluated as a function of high temperature exposure time at 250°C. This temperature was chosen based on the composite’s thermal behavior, which was determined by thermogravimetric analysis and differential scanning calorimetry. The mechanical behavior of the composite was determined before and after exposure to high temperature by using a three-point bending test and a non-destructive sonic test. The average value of the fracture load increased in the first 90 min of exposure to temperature, and only after longer exposure times, upwards of 120 min, the failure load decreased. This behavior was attributed to a post-curing effect on the composite’s polymeric matrix. However, toughness sharply decreased as a consequence of the exposure to temperature, and large amounts of smoke were generated, even after exposures as short as 30 min. The value of the damping ratio evaluated by the sonic test, decreased during the first 60 min of exposure and then increased, showing a possible competition between post-curing and thermal degradation as a function of exposure time. From a macroscopic point of view, it can be observed that the failure of fiber/matrix interfaces may be the main damage mechanism.