Equivalent Damage Research Articles

An anisotropic damage model of elasticity based on a series coupling method

This paper presents the study on an equivalent anisotropic elastic damage model, i.e. the series model, which is constructed by coupling the truss microstructure in series with an isotropic volumetric elastic element. This model can simulate the material with any thermodynamically admissible values of Poisson’s ratio as well as inherit the simplicity of the truss microstructure model. Further discussion indicates that at least two independent scalars are needed to characterize the isotropic damage. This coupling method presented in this work provides a new way to research anisotropic damage of materials. DOI: http://dx.doi.org/10.5755/j01.mech.22.1.12352

Comparison of ablation mechanisms at low fluence for ultrashort and short-pulse laser exposure of very thin molybdenum films on glass.

Complete removal of a loosely adhered very thin molybdenum film from a glass substrate is investigated for both femtosecond and nanosecond lasers at different wavelengths. Atomic force microscopy and scanning electron microscopy confirm that ablation of the molybdenum film by femtosecond pulses occurs close to the damage threshold fluence, creating minimal damage to the substrate. This is in contrast to nanosecond laser processing where significant substrate damage at the equivalent damage threshold fluence is observed. Simulations predict a two-stage mechanical buckling mechanism in the femtosecond case. Out-of-plane thermal expansion first results in a tensile expansion of molybdenum film from the glass substrate; this locally delaminated film is then buckled by a subsequent compressive stress, leading to thin film spallation. Ablation by nanosecond laser pulses behaves differently. The appreciable heat diffusion length (∼700 nm) in molybdenum, observed for the nanosecond case, results in an increased thermal expansion of the glass. The thermally induced stress generated by the molten glass creates a delaminated area, which "pushes" the compressed film away from the substrate. These findings are relevant to future selective laser patterning of very thin molybdenum layers.

Probabilistic Properties of Fatigue Damage and an Equivalent Damage Simplification Model for Multi-Level Load Spectra

An equivalent fatigue damage simplification model for multi-level load spectrum is proposed. On the basis of the probabilistic fatigue damage model which takes load sequence effect into account and the constant amplitude fatigue tests, probabilistic properties of damage accumulated in one loading block are achieved quantitatively by statistical methods. The new simplification model can ensure that, for the original spectrum and simplified spectrum, the probabilistic properties of fatigue damage are almost the same. Fatigue tests for Al-alloy straight plates are performed to test the validity of the model. The test results are in good agreement with predicted results.

An evaluation of performance measures for hotspot identification

ABSTRACTAn important step in highway safety analysis is the identification of high-crash locations or “hotspots.” Various performance measures are currently used for hotspot identification (HSID). Current measures are mostly based on crash frequency. This article proposes a performance measure based on crash severity, namely, the crash factor measure (CFM). In this article, the performance measures are classified broadly by crash frequency and crash severity. The crash severity measures, the CFM, the equivalent property damage only (EPDO), and the Empirical Bayes supplemented with crash severity (EBCS), and the crash frequency measures, the crash rate (CR) and the Empirical Bayes (EB) are evaluated using eight tests based on empirical and simulated data. To ensure detailed assessment, the evaluation was carried out for three entire highway routes (an Interstate, a US, and a State highway), that is, beyond the top 1% to 10% of hotspots commonly examined. The results from the evaluation demonstrate that the EB and CFM measures performed consistently and are recommended for use. Based on inconsistent results, the CR measure is not recommended for HSID. Based on the overall results, it is also recommended that, for any proposed performance measure, the evaluation should be carried beyond 1% to 10% of the hotspots.

Internal Attack Identification and Inhibition System using Cosine Similarity for Abnormal User Detection

Network security plays a vital role in the prevention of data transmission network from the unauthorized access and illegal activities performed by the malicious users. Various security mechanisms include encryption and decryption, password protection, firewalls, anti-malware applications, Intrusion Detection Systems etc. Even though, these mechanisms prevents the network from security attacks, they fail to identify the internal attackers. The internal attackers causes equivalent damage as the external attackers. As the internal attackers imitate the authorized users, it is tedious to identify those attackers. In order to address the abovementioned issues, this paper proposes an Internal Attack Identification and Inhibition System (IAIIS) by combining the data mining and forensic techniques. The System Call (SC) of the users at the kernel are analyzed in the proposed IDS. The Cosine Similarity (CS) is applied to compare the profiles of the users to find, whether the user is a normal user or an abnormal user. The experimental results evaluate the proposed system in terms of detection accuracy, decisive rate threshold, response time, abnormal user count, and false alarm rate.

Proton Irradiation as a Screen for Displacement-Damage Sensitivity in Bipolar Junction Transistors

NPN and PNP bipolar junction transistors of varying sizes are irradiated with 4-MeV protons and 10-keV X-rays to determine the amount of ionization-related degradation caused by protons and calculate an improved estimate of displacement-related degradation due to protons. While different ratios of degradation produced by displacement damage and ionization effects will occur for different device technologies, this general approach, with suitable margin, can be used as a screen for sensitivity to neutron-induced displacement damage. Further calculations are performed to estimate the amount of degradation produced by 1-MeV equivalent neutron displacement damage compared to that produced by the displacement damage due to protons. The results are compared to previous work.

Cryogenic etching processes applied to porous low-k materials using SF6/C4F8 plasmas

Cryogenic etching processes in SF6 and SF6/C4F8 plasmas were successfully applied to porous organosilicate glasses. Such materials are low-k candidates for advanced interconnects. Their integration is very challenging because of plasma induced damage. These two chemistries (SF6 and SF6/C4F8) have demonstrated a promising capability of significantly reducing the damage caused by plasma etching. Desorbed species were analyzed during the wafer warm-up from cryogenic to room temperature by in situ mass spectrometry. An equivalent damage layer (EDL) was evaluated by ex situ Fourier transform infrared (FTIR) spectroscopy and in situ ellipsometry. An anneal step at 350 °C seems efficient to completely desorb the remaining CFx species. Anisotropic profiles were obtained using both chemistries. The selectivity is enhanced using SF6/C4F8 process at low temperature.

Coupled fluid flow and elasto-plastic damage analysis for fractured porous chalk with induced wormhole

Acid injection in a carbonate oil reservoir can increase oil recovery by etching a part of the fractured porous reservoir and generating conductive channels (“wormholes”), which creates an easier path for oil production. However, it is crucial to predict the wormhole and reservoir strength and their failure for a successful acid treatment. For this purpose, a continuum-based computational method is developed. The model includes flow in the porous chalk reservoir, flow in the wormhole and reversible and irreversible deformation of chalk and fractures, which are modeled with an equivalent elasto-plastic damage constitutive model. The coupling between the reservoir flow and the fractured chalk deformation is done by explicit coupling method. The results found that the risk of the wormhole's walls failure is higher if the natural fractures are oriented along the wormhole; however, natural fractures with larger dip angles and higher inclinations in respect to the wormhole increase the risk of the rock failure. Results shows that increased fluid production from the wormhole, which can be the result of the further acid treatments, developing irreversible behaviors of the rock and reduces the natural fracture asperity at the wormhole's tip, in addition to increasing the wormhole's wall deformation, eventually leading to the wormhole's occlusion.

Test simulation of neutron damage to electronic components using accelerator facilities

The purpose of this work is to demonstrate equivalent bipolar transistor damage response to neutrons and silicon ions. We report on irradiation tests performed at the White Sands Missile Range Fast Burst Reactor, the Sandia National Laboratories (SNL) Annular Core Research Reactor, the SNL SPHINX accelerator, and the SNL Ion Beam Laboratory using commercial silicon npn bipolar junction transistors (BJTs) and III–V Npn heterojunction bipolar transistors (HBTs). Late time and early time gain metrics as well as defect spectra measurements are reported.

Morphological and structural effects on tungsten targets produced by fusion plasma pulses from a table top plasma focus

A table top plasma focus device operating at hundreds of joules was used to simulate an equivalent damage factor than the obtained on the divertor in tokamak experiments. Using the ejected plasma produced after the pinch disruptions, the effects on tungsten targets from 50 cumulative plasma shocks with power fluxes per shot between 2.6 and 9200 kW cm−2 and with a duration time in the order of tens of nanoseconds (damage factor in the order of 100–103 (W cm−2)s1/2) were studied. Morphological analysis shows an increasing appearance of cracked surfaces with holes, fissures and defects, suggesting a potential progression of stress effects and a fast heat load that melts the surface, ending in thermal contractions that recrystallize the surface of the target. A structural analysis demonstrates a compressive stress development and suggests that part of the energy is released in the melting of the surface in case of a plasma shock with a power flux of 9.2 MW cm−2, 75 ns duration pulse, 2.5 × 103 (W cm−2)s1/2 damage factor. How to increase the damage factor by one order of magnitude up to the expected value from type I ELMs on the ITER divertor, i.e. 104 (W cm−2)s1/2 is discussed.

A thermodynamic correlation between damage and fracture as applied to concrete fatigue

Fatigue damage in concrete is characterized by the simultaneous presence of micro and macrocracks. The theory of fracture mechanics conveniently handles the propagation of macrocracks, whereas damage mechanics precisely describes the state of microcracking. This paper provides a platform to correlate fracture mechanics and damage mechanics theories through an energy equivalence within a thermodynamic framework by equating the energy dissipated according to each theory. Through this correlation, damage corresponding to a given crack length could be obtained, and alternatively a discrete crack could be transformed into an equivalent damage zone. The results are validated using available experimental data on concrete fatigue including stiffness degradation and acoustic emission.

Investigating mitochondria as a target for treating age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of blindness among older adults in the developed world. Although the pathological mechanisms have not been definitively elucidated, evidence suggests a key role for mitochondrial (mt) dysfunction. The current study used our unique collection of human retinal samples graded for the donor's stage of AMD to address fundamental questions about mtDNA damage in the retina. To evaluate the distribution of mtDNA damage in the diseased retina, damage in the retinal pigment epithelium (RPE) and neural retina from individual donors were compared. To directly test a long-held belief that the macula is selectively damaged with AMD, RPE mtDNA damage was measured in the macula and peripheral sections from individual donors. Small segments of the entire mt genome were examined to determine whether specific regions are preferentially damaged. Our results show that mtDNA damage is limited to the RPE, equivalent mtDNA damage is found in the macular and peripheral RPE, and sites of damage are localized to regions of the mt genome that may impact mt function. These results provide a scientific basis for targeting the RPE mitochondria with therapies that protect and enhance mt function as a strategy for combating AMD.

Plantation forestry and dairy farming land-use impacts on potential wear of rural roads

Productive land-use requires vehicular traffic that may cause wear and damage to rural roads. This is of particular interest to territorial authorities responsible for planning and funding the maintenance of these roads. Debate sometimes ensues over the need for differential rates or road user charges for different land-uses. Rural land-use change is occurring around the world; in some areas moving from agriculture to forestry and vice versa in other areas. Two case study properties in New Zealand were selected to evaluate the effects of dairy farming and plantation forestry land-uses on vehicular traffic and potential road damage. Semi-structured interviews were used to derive expected traffic counts by vehicle type and management activity. Pavement design formulas were used to calculate equivalent standard axle load (ESAL) values and vehicle damage factors (VDF). Dairy farming generated over seven times the amount of traffic compared with plantation forestry, 21.5 versus 2.9 vehicles per hectare per year. Almost three-quarters of the dairy farm traffic and half of the plantation forestry traffic fits into the “light” vehicle class which contributes little to road wear. The calculated VDF for dairy farming was half that of plantation forestry; 0.43 versus 0.85 ESAL per vehicle. The total ESAL value for dairy farming, however, was four times higher than that for plantation forestry. Changing land-use from plantation forestry to dairy farming, or vice versa, could have a significant effect on the rate of wear and damage on rural roads.

Complication on the spectrum of automotive swing arm due to low-amplitude loads

A program load spectrum compiling method for automotive components was introduced with swing arm as example. Based on pseudo-damage and statistical analyses, combined with structural coaxing property, a spectrum compiling method considering the coaxing effects is put forward. The new method overcomes the deficiency of the traditional methods, in which only the damage effect of low amplitude loads is considered. Meanwhile, referred to the equivalent damage rule between damage loads, the equivalent coaxing rule between coaxing loads is explored. By transferring the coaxing loads to the most effective level, the bench tests show that the total cycling blocks decline sharply under self-made specification. The influence of strengthening loads is proved to be taken into account by deleting the useless loads during the spectrum compiling process. Moreover, the real service condition of automotive components by simulation can be faster and more real, and it is significant to predicate the failure mode of durability tests and to estimate service life of automotive components more accurately.

Interest of Equivalent Damage Methods for Railway Equipment Qualification to Vibrations

Fatigue, induced by vibrations of supporting structures, is one of the major cause of mechanical failures of equipment mounted on vehicles and on machines. Account of vibration excitation should therefore be considered with care when designing new equipment.Equivalent damage methods developed in the 80's for the design of armament equipment are firstly presented in the paper. These methods allow to convert complex time vibration signals representative of in-service vibrations of the supporting structure into simple Gaussian or Sine signals, easy to handle for defining equipment specifications and qualification tests.Then, the interest of these methods for the design of railway equipment is discussed. The IEC 61 373 standard dealing with qualification of railway equipment to train vibrations is assessed in the light of the equivalent damage methods. Some weak points of the standard are pointed out and recommendations for standard updating are given to conclude the paper.

Fretting fatigue failure mechanism of automotive shock absorber valve

Fretting fatigue is a complex mechanical failure phenomenon, in which two contact surfaces undergo a small relative oscillatory motion due to cyclic loading. This study proposes a methodology to analyze the fretting fatigue failure mechanism of automotive shock absorber valve by means of experimental and numerical approaches. A servo hydraulic test set-up is used to simulate fretting fatigue under real working conditions. Moreover, a 3-D finite element model is developed to analyze the contact status and stress distribution at contact interface between connected components, i.e. washer-disc contact. The experimental test results depict that fretting damage appears at contact interface between washer and disc, which causes the initial crack nucleation and advancing the crack up to the final fracture of valve disc. Stress field, obtained by numerical simulation, is used to monitor some fretting fatigue features such as the distribution of relative slip amplitude, contact pressure and different stress fields at contact interfaces. Eventually, the crack initiation site is estimated by monitoring variation of equivalent multiaxial damage stress at contact interface.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part I

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part II

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

Fuzzy Cluster–Based Method of Hotspot Detection with Limited Information

In the absence of geometric design and traffic data, hot-spot identification (HSID) is done primarily with crash data only, based on techniques such as crash frequency (CF), fatal crash frequency (FCF), or equivalent property damage only (EPDO), despite the known limitations of these techniques. In this article, the authors propose an improved HSID technique that may be used with crash data only. Using disaggregate crash history information, this method estimates probabilities of crash severities by the major contributing factors using severity models. These probabilities are used to compute expected numbers of severe and fatal crashes at various locations which are then used to classify the locations into two fuzzy cluster, namely hotspot and non-hotspot using Fuzzy C-Means (FCM) algorithm. The identified hotspots are ranked based on their mean departure from the core of the hotspot cluster. These rankings are compared with rankings done using existing techniques namely CF, FCF, EPDO, and Empirical Bayes’ (EB). The proposed method is found to be a robust method for hotspot detection with performance better than existing methods that use crash data only and comparable to the EB method.

Equivalent damage-healing approach to residual fatigue life prediction for copper film by laser repair

A healing method for fatigue damage was investigated by laser shock peening and laser irradiation with excimer laser for polycrystalline copper film. It is found that the sum of the consumed fatigue ductility and the total fatigue ductility for the damaged specimen after both laser treatments is equal to the total fatigue ductility for the undamaged specimen after both laser treatments. The evolution of the damage healing can be replaced by that for the undamaged specimen after laser treatment. Based on the equivalent fatigue damage evolution, a residual fatigue life prediction method is proposed during the damage-healing process for the copper specimen. The predicted lives by the proposed method agree well with the experimental results.