Active Damage Mechanisms Research Articles

Three-dimensional characterisation of deformation-induced damage in dual phase steel using deep learning

High performance sheet metals with a multi-phase microstructure suffer from deformation induced damage formation during forming in the constituent phases but importantly also where these intersect. To capture damage in terms of the physical processes in three dimensions (3D) and its stochastic nature during deformation, two challenges remain to be tackled: First, bridging high resolution analysis towards large scales to consider statistical data and, second, characterising in 3D with a resolution appropriate for sub-micron sized voids at a large scale. Here, we present how this can be achieved using panoramic scanning electron microscopy (SEM), metallographic serial sectioning, and deep-learning assisted automatic image analysis. This brings together the 3D evolution of active damage mechanisms with volumetric and environmental information for thousands of individual damage sites. We also assess potential surface preparation artefacts in 2D analyses. Overall, we find that for the material considered here, a dual phase (DP800) steel, martensite cracking is the dominant but not sole origin of deformation induced damage and that for a quantitative comparison of damage density, metallographic preparation can induce additional surface damage density far exceeding what is commonly induced between uniaxial straining steps.

Frost damage evaluation of concrete irrigation structure by X-ray CT and AE energy release trend at the initial loading stage

Deterioration of concrete infrastructures occurs for several reasons, leading to operational problems and further collapse. Freezing-thawing processes are one of the active damage mechanisms in cold regions causing defect accumulation in the inner structure of the material and reduction of the mechanical properties. The optimal way to evaluate the damage degree is by applying non-destructive testing (NDT) methods which allow detailed and integrated results. In this research, a relationship between Acoustic Emission (AE) release energy trend and X-ray Computed Tomography (CT) parameters was investigated for damage quantification. Visualization and extraction of the internal concrete components were conducted by X-ray CT. The ultrasonic pulse velocity (UPV) and resonant frequency methods were employed for the determination of the dynamic modulus of elasticity. After utilizing AE on the compression test, the damage characterization was evaluated. The extensive description of structural members in in-service structure was acquired using principal component analysis (PCA). The X-ray CT results show that all specimens have initial damage degrees in form of cracks and voids unevenly distributed within the concrete matrix. Regarding the irrigation structure, all concrete specimens have unique particle characteristics depending on which structural members they were drilled out from. Moreover, it is observed that the accumulated damage in the form of voids positively correlates with the initial AE energy release rate. In concrete specimens with low damage degrees, the AE energy release has an upward trend of low amplitude (≤50 dB) with a silent stage at the initial loading and sudden release only near the final failure. In contrast, heavily damaged concrete shows continuous AE energy release of high amplitude (≥60 dB) and with a high initial AE energy release rate corresponding to the uninterrupted crack propagation and coalescence in the early stage of fracture and throughout the loading due to the high weak zones ratio. These results indicate that frost damage can be evaluated by the comprehensive analysis of the fracture process of concrete based on X-ray CT and AE results to characterize the damage degree.

Application of innovative methodology for risk assessment and inspection methods on example of small experimental biomass gasification unit

Application of Innovative methodology for risk assessment and inspection methods is the result of a long-term work in the field of Risk-Based Inspection. As such, it was successfully applied on oil and gas facilities in the Middle East. As an example of its versatility, application will be shown on small experimental biomass gasification plant utilized for the purpose of combined heat and power generation, built in Serbia in the middle of the past decade. Throughout the analysis both active and passive damage mechanisms will be identified as well as barriers thus enabling the creation of a system that documents the dynamics of the damage mechanisms and installed barriers.

Damage Mechanisms and Anisotropy of an AA7010-T7452 Open-Die Forged Alloy: Fatigue Crack Propagation.

The process–microstructure–property relationship of high-strength 7000 series aluminum alloys during fatigue crack propagation (FCP) is highly relevant for safety during the design and service of aircraft structural components. It is scientifically evident that many metallurgical factors affect FCP properties, but partly contradictory or inconclusive results show that the quantitative description of the relationships is still a major challenge among researchers and engineers. Most research focuses on sheet or plate products and investigations lack quantitative information on the process–property relationship between open-die forged thick products and FCP. The present study contributes to this field by investigating the fatigue crack growth behavior of an open-die forged AA7010-T7452 aluminum alloy. Four different forging conditions comprising different characteristic microstructures are comparatively analyzed. The influence of grain size, grain shape, specimen orientation, crystallographic texture, and primary phase particles is investigated. Fractographic analysis reveals different active damage mechanisms during fatigue crack growth. Based on that, the microstructure features relevant to fatigue damage areidentified in each regime of crack growth.

Integrated Use of Measurements for the Structural Diagnosis in Historical Vaulted Buildings.

The process of the structural diagnosis of historical buildings is analyzed. The correlation of different data is a fundamental issue, related to the multidisciplinary nature of the study of built heritage. Quantitative data are collected by sensors, these being environmental data (temperature and humidity) or cracks (displacements). Another important source being qualitative data, derived from historic investigation, diagnostic investigations, etc. However sometimes the results may be difficult to correlate due to the different nature of the data, being quantitative and qualitative, as well as spread over the long life of the construction. In particular, the here proposed methodology suggests the use of light detection and ranging (LiDAR) scanning for the geometric and structural deformation survey, damage survey, historic evolution, monitoring of the crack pattern and environmental data. The integrated use of the collected data with digital and finite element models is investigated in two case studies. The combined use of the set of collected data is shown to be fundamental to the interpretation of the active damage mechanisms in the system, and for making appropriate decisions related to their safety. Finally, a guideline is proposed to allow for a more general use of the herein proposed structural diagnosis procedure.

Innovative approach of damage mechanism identification for energy equipment – A case study of oil refinery

ABSTRACT The purpose of this paper is to show the results of Risk-Based Inspection (RBI) analysis conducted in a refinery plant in the Middle East by applying slightly modified methodology for an RBI. Due to the complexity of the refinery, a summary of identified damage mechanisms and discussion regarding barriers are shown in chosen representative units. Application of the Innovative approach in the implementation of RBI process will be presented by defining active and passive damage mechanisms, with the emphasis on damage mechanism identification for energy equipment. Finally, the main result of application of Innovative approach lies in the fact that one can setup the system that can be more useful than the traditional approach to an RBI analysis in a way that specific time frame for triggering an RBI review can be better defined. This approach was developed and successfully applied for an RBI study covering six units where over 1100 pieces of major equipment and more than 15000 pieces of piping systems were analyzed.

Hip implant performance prediction by acoustic emission techniques: a review.

Nowadays, acoustic emission (AE) has its applications in various areas, including mechanical, civil, underwater acoustics, and biomedical engineering. It is a non-destructive evaluation (NDE) and a non-intrusive method to detect active damage mechanisms such as crack growth, delamination, and processes such as friction, continuous wear, etc. The application of AE in orthopedics, especially in hip implant monitoring, is an emerging research field. This article presents a thorough literature review associated with the implementation of acoustic emission as a diagnostic tool for total hip replacement (THR) implants. Structural health monitoring of an implant via acoustic emission and vibration analysis is an evolving research area in the field of biomedical engineering. A review of the literature reveals a lack of reliable, non-invasive, and non-traumatic early warning methods to evaluate implant loosening that can help to identify patients at risk for osteolysis prior to implant failure. Developing an intelligent acoustic emission technique with excellent condition monitoring capabilities will be an achievement of great importance that fills the gaps or drawbacks associated with osteolysis/implant failure. Graphical abstract.

Microscopic investigation of damage mechanisms and anisotropic evolution of damage in DP600

Weight reduction and fuel consumption play an important role on material selection in automotive industry. In this respect, ferritic-martensitic dual phase steels are gaining popularity thanks to their versatile combination of strength and formability. In this study, we investigate evolution of damage and active damage mechanisms in a commercial DP600 steel. Interrupted tensile tests are conducted in both rolling (RD) and transverse directions (TD). Subsequently, damage mechanisms and void evolution is characterized by cross-sectional SEM micrographs. The results reveal that, in both RD and TD, damage occurs by three different damage mechanisms. Namely, void formation due to inclusions, cracking of martensite islands and decohesion between ferrite and martensite. From these damage mechanisms, void formation due to large inclusions occur in the early stages of deformation, whereas the other two are both active throughout the complete stretching. The most commonly observed damage mechanism was martensite cracks and seem to be the primary reason of failure. In addition, void evolution studies clearly show that damaged area as well as number of voids increase more rapidly in RD than TD. Furthermore, in both directions, damage concentrates at the mid plane of the specimens, leading to an inhomogeneous distribution of voids in the thickness direction.

Comparative Analysis of Probability of Failure Determination Using Weibull Distribution and Generic Failure Frequencies on Heat Exchanger Tube Bundles Based on API 581

RBI analysis for heat exchanger tube has been explained by API 581. Two types of PoF determination using statistical data is provided to determine the PoF category. Both Weibull parameter and generic failure frequencies are the methods that will be analysis in this present study. PoF determination using Weibull distribution gives the exponential value of PoF in a certain of time. This method only consider failure modes and the failure rate of heat exchanger tube without considering possible active damage mechanisms in the tube. However PoF determination using generic failure frequencies gives more complex consideration. It considers not only failure and possible active damage mechanism, but also the effect of management system facilities of the heat exchanger on the integrity of the plant.

Characterization of fatigue crack growth, damage mechanisms and damage evolution of the nickel-based superalloys MAR-M247 CC (HIP) and CM-247 LC under thermomechanical fatigue loading using in situ optical microscopy

In this paper, the influence of different phase angles, load ratios and dwell times on the thermomechanical fatigue (TMF) crack growth of the nickel-based superalloys MAR-M247 CC (HIP) and CM-247 LC is studied. The thermomechanical fatigue crack growth tests are performed under in-phase (IP) and out-of-phase (OP) TMF loading between 300°C and 950°C. It is shown, that the applied load ratio plays a crucial role for the resulting fatigue crack growth rates and whether IP or OP TMF loading is more detrimental. A digital optical microscope is installed, which allows in situ observation of the fatigue crack growth, the active damage mechanisms and the damage evolution even at high temperatures. The in situ observations are accompanied by fractographic investigations, which confirm, that IP TMF loading preferentially leads to interdentritic fracture. Finally, first steps towards a quantification of the active damage mechanisms are taken using digital image processing.

Comprehensive FE numerical insight into Finale Emilia Castle behavior under 2012 Emilia Romagna seismic sequence: Damage causes and seismic vulnerability mitigation hypothesis

In this paper, a numerical insight on the historical masonry Castle of Finale Emilia, symbol of the consequences occurred after the seismic sequence of 20–29th May 2012 in Emilia Romagna, Italy, is presented.Some different numerical models are critically compared, in order to both have an insight into the causes at the base of the partial collapse of the structure and propose valuable rehabilitation interventions with seismic upgrading to prevent future damage under seismic loads. Two different meshes are utilized, the one very refined and constituted by tetrahedron elements, the other much coarser and mainly constituted by hexahedrons, along with different hypotheses presented for the masonry material (linear and elasto-plastic with damage and softening).The analyses performed include standard modal, nonlinear static (pushover) and nonlinear dynamic analyses, under different hypotheses concerning the material properties of the single walls. Three different configurations are compared, the first is the real one stricken by the earthquake (where only one of the walls had been consolidated), the second is a hypothetical castle without any consolidated wall, the last is the situation that should be encountered after full rehabilitation. At this aim, full three-dimensional (3D) detailed finite element models (FEM) are adopted, starting from the available documentation at disposal (photos and existing drawings).From numerical results, it is found that the insufficient resistance of the constituent materials is mostly responsible for the damages observed and that the partial rehabilitation implemented by the municipality on one wall helped in limiting the damaging effect of the seismic sequence. In all cases, the numerical analyses provide a valuable picture of active damage mechanisms, giving useful hints for the reconstruction and indicating that a limited upgrading of masonry mechanical properties could limit considerably the global seismic vulnerability of the structure, in light of a reconstruction of the collapsed parts of the Castle.

Projectiles Impact Assessment of Aircraft Wing Structures with Real Dynamic Load

This paper presents an analysis to achieve the impact damage of the wing structure under real dynamic load. MPCCI tools are utilized to convert wing aerodynamic load into structural Finite Element Method (FEM) node load. The ANSYS/LS-DYNA code is also used to simulate the dynamic loading effects of the wing structure hit by several projectiles, including both active damage mechanism and common damage mechanism. In addition, structural node force on the leading edge and the midline is compared to the aerodynamic load separately. Furthermore, the statistical analysis of the penetrating size and the stress concentration around the damage holes indicates that under the same load situation, the structural damage efficiency of active damage mechanism is significantly higher than the one of common damage mechanism.

Analysis of damage mechanisms in drilling of composite materials by acoustic emission

Conventional methods for analysis of drilling of composite materials usually study the amount of damaged area and effective parameters. However, these methods do not provide investigators with sufficient information regarding drilling-induced damage. In this paper, a procedure for discrimination and identification of different damage mechanisms based on the analysis of acoustical signals emitted during the process is presented. Using principle component analysis for data reduction and unsupervised pattern recognition analysis, the drilling process was divided into three main stages, i.e. entry stage, cutting stage and exit stage. Different methods of signal processing were then used to identify and discriminate the most active damage mechanisms in each stage. As a result, matrix cracking, delamination, fiber pull out and friction were discriminated and the frequency distribution of each one was identified.

Vulnerability of welded joints and active damage mechanisms in petrochemical plants and processes: reliability through programming of risk-based inspection – Part I‡

The special process of welding still plays a key role in the fabrication of pressurized equipment for the energy processing and generation industry. Similarly, welding is extensively used in repair, modification and overlay/cladding procedures and during the maintenance operations for large plants. However, the harsh statistics relating to faults shows welded joints to be among the most ‘at-risk’ areas with regard to various active damage mechanisms. Within the framework of the management of plant risk and equipment integrity, the risk-based inspection method, with the aim of prioritizing and optimizing the inspection strategy, focuses attention on the criticality of welded joints with the framework of problems related to both simple mechanical vulnerability and physicochemical aspects such as corrosion and/or stress corrosion. The aim of this paper is to offer an overview of the interactions existing between the various active damage mechanisms in plants and welded joints in addition to indicating the criticality associated with these interactions, with the purpose of optimizing the management of plant risk and inspection strategies for resolving them.

DOCUMENTATION PROTOCOLS TO GENERATE RISK INDICATORS REGARDING DEGRADATION PROCESSES FOR CULTURAL HERITAGE RISK EVALUATION

Abstract. Sustainable maintenance and preservation of cultural heritage assets depends highly on its resilience to external or internal alterations and to various hazards. Risk assessment of a heritage asset's can be defined as the identification of all potential hazards affecting it and the evaluation of the asset's vulnerability (building materials and building structure conservation state).Potential hazards for cultural heritage are complex and varying. The risk of decay and damage associated with monuments is not limited to certain long term natural processes, sudden events and human impact (macroscale of the heritage asset) but is also a function of the degradation processes within materials and structural elements due to physical and chemical procedures. Obviously, these factors cover different scales of the problem. The deteriorating processes in materials may be triggered by external influences or caused because of internal chemical and/or physical variations of materials properties and characteristics. Therefore risk evaluation should be dealt in the direction of revealing the specific active decay and damage mechanism both in mesoscale [type of decay and damage] and microscale [decay phenomenon mechanism] level. A prerequisite for risk indicators identification and development is the existence of an organised source of comparable and interoperable data about heritage assets under observation. This unified source of information offers a knowledge based background of the asset's vulnerability through the diagnosis of building materials' and building structure's conservation state, through the identification of all potential hazards affecting these and through mapping of its possible alterations during its entire life-time. In this framework the identification and analysis of risks regarding degradation processes for the development of qualitative and quantitative indicators can be supported by documentation protocols. The data investigated by such protocols help identify the parameters needed for the assessment of the preservation state of a monument and its monitoring through its entire lifetime. The main tool for detecting these indicators is a diagnostic methodology based on appropriate standards that reveals the actual degradation processes responsible of the asset's vulnerability. It is very important that the integration between the material's diagnosis and the overall documentation is taken into consideration in order to identify the required levels of protection and preventive conservation for heritage assets depending on the most frequent local risks. The ranging of risks is therefore necessary according to their importance in each area. Documentation protocols provide with a specific diagnostic tool for materials characterization, decay diagnosis, evaluation process of former conservation materials and interventions, standard procedures for monitoring and control as well as data documentation based on specific guidelines and standards. Implementation and analysis of a "standardised" diagnostic study will reveal the main risks due to degradation processes affecting the heritage asset to be subsequently recorded in order to result into risk indicators. The development of risk indicators regarding degradation processes is the basic step towards uptaking efficient management, preventive conservation and strategic planning for heritage assets against various threats. These risk indicators could be further elaborated according to the activities of inspection, diagnosis and intervention works, offering scientific support to the decision making process for cultural heritage preventive conservation and overall protection.

Vulnerability of welded joints and active damage mechanisms in petrochemical plants and processes: reliability through programming of risk based inspection (RBI) – Part II

The special process of welding still plays a key role in the fabrication of pressurised equipment for the energy processing and generation industry. Similarly, welding is extensively used in repair, modification and overlay/cladding procedures and during the maintenance operations for large plants. However, the harsh statistics relating to faults shows welded joints to be among the most ‘at risk’ areas with regard to various active damage mechanisms. Within the framework of the management of plant risk and equipment integrity, the Risk Based Inspection (RBI) method, with the aim of prioritising and optimising the inspection strategy, focusses attention on the criticality of welded joints with the framework of problems related to both simple mechanical vulnerability and physico-chemical aspects such as corrosion and/or stress corrosion. The aim of this paper is to offer an overview of the interactions existing between the various active damage mechanisms in plants and welded joints in addition to indicating the criticality associated with these interactions, with the purpose of optimising the management of plant risk and inspection strategies for resolving them.

Multifunctional High Precision Pneumatic Loading System (HIPS) for Creep-Fatigue Testing

Abstract The first successful application of the high precision pneumatic loading system for advanced material testing was developed at VTT in 1995. The pneumatic servo-controlled loading system is capable of operating in a range of extreme conditions such as high temperature, pressurised water or steam, Super Critical Water (SCW) and irradiation environments. The main benefit of the pneumatic loading system is that there is no moving parts (loading lead-throughs) required for loading a specimen inside a pressure vessel or otherwise demanding containment (water, gas, radioactive), only pressure lines and electrical feedback connections together with the pneumatic loading unit, bellows are required. Also, the pneumatically powered testing device itself can be far away from the control units and regulating servo valves. The HIPS, previously used for tensile testing, stress corrosion cracking, fatigue, in-pile creep fatigue (copper), and other test variants with combined environmental impact, has now been modified to perform load and strain controlled testing at temperatures in the creep range for steels. For the high temperature applications where creep is an active damage mechanism, the HIPS technology opens new applications for creep and fatigue related testing types such as standard creep-fatigue (with and without hold time), relaxation and slow strain rate tensile testing. The main focus of this paper is to present the current status of the development work of the HIPS technology for high temperature applications, presently conducted in air atmosphere. Also some initial creep-fatigue results and creep-fatigue behavior comparisons are presented for some austenitic stainless steels (316L, 347H, 321).

Acoustic emission activities and damage evaluation of reinforced concrete beams strengthened with CFRP sheets

In this study, the applicability of acoustic emission (AE) techniques to monitor damage evolution in reinforced concrete (RC) beams strengthened in flexure with carbon fiber reinforced polymer (CFRP) sheets is investigated. The objective is to initiate the creation of a user-friendly health monitoring system for RC structures strengthened with CFRP sheets using AE techniques. Five beams, 200mm×300mm in cross-section, were tested under three-point bending over a span of 1700mm. One of the beams was tested in its virgin condition to serve as reference; the remaining four beams were tested after being strengthened with CFRP sheets bonded on the tension face. The parameters investigated in this study include both the amount of CFRP sheets and construction imperfections (the CFRP sheets were intentionally bonded without adhesive in the centermost 10% and 20% bonding area). The AE signals were collected and analyzed for all specimens. The AE parameters were analyzed for four levels of damage based on initial crack, propagation, yielding of main bars, and fracture or rip-off of the CFRP sheets. The frequency-peak magnitude distribution of the AE parameters was used to determine the b-value, defined by the Gutenberg–Richter relationship, for evaluating the damage evolution and fracture process of RC beams strengthened in flexure with CFRP sheets. From the results of this study, the signal characteristics – event, amplitude versus frequency, and amplitude versus duration – show clear differences in the different loading stages, depending upon the active damage mechanism. The b-value is correlated to the fracture process of the RC beams bonded with CFRP sheets and the degree of localization of damage. The AE technique is a useful nondestructive technique for monitoring the behavior of RC beams that are externally reinforced in flexure with CFRP sheets.

Thermomechanical fatigue of a directionally-solidified Ni-base superalloy: Smooth and cylindrically-notched specimens

Directionally-solidified (DS) Ni-base superalloys are used in high temperature gas turbines because of their excellent properties in the most aggressive mechanical, thermal, and environmental operating conditions. Fatigue life prediction approaches need to account for the presence of cooling holes and other geometric stress concentrations, time-dependent dwells, thermomechanical cycling, and anisotropic material properties. In working towards such a life model, this paper describes the cyclic deformation response and damage mechanisms resulting from thermomechanical fatigue (TMF) of directionally-solidified CM247LC DS. Linear in-phase (IP) and out-of-phase (OP) TMF cycles were performed on both smooth and cylindrically-notched round-bar specimens in both longitudinal and transverse grain orientations. Results take into consideration anisotropy, time-dependent deformation, and the severity of the notch in addition to the waveform and temperature cycle characteristics. The active damage mechanisms are identified as a function of these parameters. Conclusions are drawn in light of fractography, microscopy, and finite element analysis conducted to evaluate geometric and microstructural influences on the time-dependent deformation and fatigue behavior.

Cyclic Deformation Behaviour and Damage Development on Different Hierarchical Levels in Cortical Bone

Bone is a complex natural composite material built of organic and anorganic components and very well adapted to the in vivo loading conditions. The material exhibits an excellent damage resistance under static and fatigue loading conditions. This is partially due to self-healing processes, but to a great extent also to its hierarchical microstructure. The investigation of the deformation behaviour and the damage mechanisms on different length scales gives valuable insight into which level(s) of hierarchy influence the fatigue resistance in which way. In the present work, cyclic deformation tests have been performed on cortical bone specimens. On one hand, stress-strain-hysteresis measurements in different types of tests, such as constant amplitude tests, load increase tests, and combined static and cyclic tests, give information on the active damage mechanisms. For example, changes in the development of the stiffness, non-elastic strain amplitude and non-elastic mean strain as a result of different loading velocities and stress levels allow the discrimination between time and cycle dependent damage mechanisms. These results were correlated with microstructural investigations of the damage development on different hierarchical levels by light and scanning electron microscopy.