Failure Mechanism

Nonvolatile RAM using resistance contrast in phase-change materials [or phase-change RAM (PCRAM)] is a promising technology for future storage-class memory. However, such a technology can succeed only if it can scale smaller in size, given the increasingly tiny memory cells that are projected for future technology nodes (i.e., generations). We first discuss the critical aspects that may affect the scaling of PCRAM, including materials properties, power consumption during programming and read operations, thermal cross-talk between memory cells, and failure mechanisms. We then discuss experiments that directly address the scaling properties of the phase-change materials themselves, including studies of phase transitions in both nanoparticles and ultrathin films as a function of particle size and film thickness. This work in materials directly motivated the successful creation of a series of prototype PCRAM devices, which have been fabricated and tested at phase-change material cross-sections with extremely small dimensions as low as 3 nm • 20 nm. These device measurements provide a clear demonstration of the excellent scaling potential offered by this technology, and they are also consistent with the scaling behavior predicted by extensive device simulations. Finally, we discuss issues of device integration and cell design, manufacturability, and reliability.

Long-term cyclic loading is observed in a wide range of human activities, as well as in nature, such as in the case of ocean waves. Cyclic loading can lead to ratcheting which is defined as progressive accumulation of plastic deformation in a material. Long-term cyclic loading causes a time effect (creep), which is a secondary compression effect. In this article, we conducted 15 triaxial tests on four types of cohesive materials in undrained conditions to evaluate the damage and failure mechanism. To characterize the strain and pore pressure development, we modified the Yanbu resistance concept. On the basis of the static creep tests, we concluded that the stress paths for undrained creep behavior have to take into account the pore pressure developed during long-term cyclic loading. Pore pressure build-up and plastic strain accumulation during long-term cyclic loading are dependent on the number of loading cycles. Finally, we proposed the failure criterion, which was based on the Modified Cam-Clay constitutive model.

Preheating can be defined as heating the base metal(s) to a certain temperature before welding. Preheating serves four major purposes: (a) to decrease cooling rate, which produces ductile microstructure that increases resistance to cracking and helps in diffusion of hydrogen, (b) to reduce shrinkage stress between the weld zone and base metal, (c) to prevent chilling effect ('cold start') and ensure proper fusion, and (d) to eliminate moisture from the sample surface [1, 2]. However, excessive preheating is expensive and yields defects such as thermal distortion in the welded component . On the other hand, inadequate preheating results in different types of cracking, insufficient fusion, and penetration . Carbon equivalent (CE) is used as a tool for approximating proper preheats . Besides CE, optimum preheating temperature also depends on section thickness, restraint, ambient temperature, filler metal hydrogen content, and previous cracking problems .

Landslides can be trigged by external mechanisms including undercutting of a slope by stream erosion, wave action, glaciers, or human activities as building intense or prolonged rainfall, rapid snow melt, or sharp fluctuations in ground-water levels. Shocks or vibrations caused by earthquakes or construction activity. Jordan is one of the countries of the world suffering from the landslides at different cities due to the swelling of the clay materials in some subsurface geological formations as Fuhais-Hummar-shu'yeb formation from the Cenomanian age. The locations of the landslides and deformations along Na'ur -Dead Sea road, the water surfaces flow directions and the slope of the geological layers of the study area, the drainage pattern of the eastern region of the Dead Sea, the locations and magnitudes of the recent landslides were determined in this study. The main landslides were found at the coordinates E 768598.508 and N 3530685.801. The magnate of the deformation at this point is 7.8 cm. The reason of the landslide of the study area was determined. The main reason of the landslides is the heavy rain the happened in the last three days before the last measurements. These precipitations infiltrate into the subsurface layer reaching the clayey layers. These clayey layers get swelling due to absorb the water. The main type of drainage pattern in the study area was determined by using the aerialphotos and satellite images by using the ARC-Hydro extension of GIS. The main type of the drainages is high-density dentratic drainage pattern. As well the satellite images were used to determine the surface water flow direction by using the GIS. The surfacewater flow direction was found toward the Na'ur-Dead Sea highway. As well the slope aspect of the study area was carried out by using the GIS software. The slope of the layers was determined toward the southwest direction.

Glass Fibre Reinforcement Polymer (GFRP) reinforcements are currently used as internal reinforcements for all flexural members due to their resistance to corrosion, high strength to weight ratios, the ability to handle easily and better fatigue performance under repeated loading conditions. Further, these GFRP reinforcements prove to be the better alternative to conventional reinforcements. The design methodology for flexural components has already come in the form of codal specifications. But the design code has not been specified for beam-column joints reinforced internally with GFRP reinforcements. The present study is aimed to assess the behaviour of exterior beam-column joint reinforced internally with GFRP reinforcements numerically using the ABAQUS software for different properties of materials, loading and support conditions. The mechanical properties of these reinforcements are well documented and are utilized for modelling analysis. Although plenty of literature is available for predicting the joint shear strength of beam-column joints reinforced with conventional reinforcements numerically, but no such study is carried for GFRP reinforced beam-columns joints. As an attempt, modelling of beam-column joint with steel and with GFRP rebars is carried out using ABAQUS software. The behaviour of joints under monotonically increasing static and cyclic load conditions. Interpretation of all analytical findings with results obtained from experiments. The analysis and design of beam-column joints reinforced with GFRP reinforcements are carried out by strut and tie model. Strut and Tie models are based on the models for the steel reinforced beam-column joints. The resulting strut and tie model developed for the GFRP reinforced beam-column joints predicts joint shear strength. Joint shear strength values obtained from the experiments are compared with the analytical results for both the beam-column joints reinforced with steel and GFRP reinforcements. The joint shear strength predicted by the analytical tool ABAQUS is also validated with experimental results.

The dry-wet cycle and high temperature exposure are important factors affecting the normal use and durability of concrete structures. The objective of this work is to investigate the mechanical properties of cement mortar specimens after combinations of dry-wet cycles and high temperature exposures, uniaxial compressive tests on cement mortar specimens were carried out under the following two sets of conditions: (1) high temperature treatment followed by a drywet cycle and (2) a dry-wet cycle followed by high temperature treatment. The results show that the compressive strength of specimens increases with the number of dry-wet cycles. After a dry-wet cycle and then a high temperature treatment procedure, the compressive strength of a specimen will first decrease and then increase with the number of dry-wet cycles. The strain at the peak stress of cement mortar decreases as the number of dry-wet cycles increases. At present, there are few research results about the mechanical properties of concrete first after combinations of dry-wet cycles and high temperature exposures. The work in this paper can enrich the results in this area.

With the existence of a high groundwater level, the head difference between the inside and outside of an excavation may lead to the loss of stability of the excavation's surface. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In some cases, the failure mechanism cannot be predicted exactly because of its mechanical complexity as well as a major lack of protection systems and not adopting effective countermeasures against this phenomenon. The article took a tranche from an 80 km long open sewer located in the Ruhr area, Germany as an example to establish a hydro-geological model and analyse the instability of the excavation base surface caused by the groundwater flow at 45m deep and to present the effectivity of an adopted drainage system inside the excavation pit as 39 columns of sand to relax the pore water pressure. By using the Finite Element Method (FEM) analysis, the failure mechanism was investigated before applying any countermeasures, and the total length of the adopted countermeasure system was minimised. Also, various position tests were performed on the adopted drainage system to confirm the optimised position. The results of this numerical study allowed the deduction of the importance of the used drainage system by achieving 44% more in the excavating process. After achieving the required excavation depth, a further increase of the sand columns' penetration may be considered non-economic because, after adding extra depth, all the situations have the same safety factor. In addition, this can provide a reference for the optimised position of the sand columns where they must be applied right by the wall and limited by a critical distance, D/2, half of the embedded depth of the wall.

Dike construction has been widely used because of its potential to protect people and properties from overtopping flows. Water levels may exceed a dike crest and cause overtopping flow during high river discharge. This phenomenon has caused serious damage to the dike body due to the reduction of soil shear strength. The increase of water content within particles and its relationship with the development of breach channel failure in downstream and upstream slopes are affected by a series of geotechnical and hydraulic aspects. Transient seepage and slope stability analyses (FOS) were performed in this study using 2D finite element methods and time-history measurements under the effect of sandy and very silty sand soils. The numerical model of SLIDE 2018 was limited by its inability to incorporate all physical processes governing an overtopping breach failure. Numerical analyses were performed to simulate the development of pore pressures and water content at six positions in the dike's upstream and downstream slopes in physical experimental tests using the van Genuchten Equation and the limit equilibrium method. The numerical results revealed that fine particles increase the pore water pressure and reduce the FOS. Appropriate dike design and maintenance are dependent on surrounding hydraulic conditions, dimensions, and soil types. Non-cohesive materials with fine particles were preferable.

Piled raft foundations are a common type of foundation for high-rise buildings. Unlike shallow foundations, deep foundations (piles) pass through weak or soft soil deposits and can reach stiff soil or bedrock to support the weight of the structure. In this paper, the performance of a medium embedment depth piled raft foundation in soft soil is presented. A numerical model was developed and a parametric study was conducted in order to simulate the case of such a foundation system and to investigate its performance in soft clay. This parametric study investigated the effect of the geometry of a piled raft foundation and the stiffness ratio between the pile material and clay on the performance of the foundation system in soft soil. Additionally, the failure mechanism of such a foundation system under load was examined. An analytical model was developed to predict the ultimate carrying capacity based on the observed failure mechanism. A semi-empirical model is proposed for determining the Improvement Factor (IF) of a given soil, pile, and geometric condition. Findings of the study indicate that the performance of piled raft foundations on soft soils is significantly affected by the piles' spacing. As the ratio S/D increases, the ultimate carrying capacity of a piled raft foundation decreases. However, when this ratio exceeds 10 (S/D > 10), piles have little or no effect on the ultimate carrying capacity of this foundation system. A piled raft foundation system fails by bearing at the base of the piles and also by shear at the side of the pile group on hyperbolic plans.

Microstructure of the laboratory castings made from Fe-40at.%Al-Zr-B alloy was homogenized by the multipass hot rolling in protective capsules and subsequent lannealing. Based on the isothermal hot compression tests and EBSD analysis, the sufficiently accurate model describing the static recrystalization kinetics of the such prepared coarse-grained B2 iron aluminide after strain 0.2 was developed. The independent variables in this model are temperature of deformation as well as annealing time equal to the deformation temperature. Unexpected effect of the previous strain value on the static softening was observed. Static recrystallization begins relatively easy in the studied alloy in the whole range of testing temperatures (900 – 1100 °C), but a very long-term annealing is quite necessary for the complete course of recrystallization.

Helical anchor consist of some steel shafts with a series of helical steel plates welded on a pitch. During installation, helical anchor was screwed into the ground by using a standard truck or trailer mounted augering equipment. The equipment will apply a rotating moment to the steel shafts to screw the anchors into ground. The torque resistance of the anchor will be monitoring along the installation. When the torque resistance achieved its designed values, it verified that capacity of anchor achieved. Behavior of helical anchor under uplift load in cohesionless soil has been studied using previous researches. Based on a few number of laboratory model results many investigators reported the uplift loading of helical anchor embedded in cohesionless soil, a review of related last works shows that not much research has been done to define the uplift capacity in cohesionless soil, a problem that is often encountered in field. The paper observed that the ultimate uplift capacity is dependent on the relative undrained/drained shear strength of cohesionless soil, the depth ratio of embedment and soil thickness ratio.

We report on investigations of the initial drift in DC current gain, or beta (b), during the early stages of reliability testing of MOCVD-grown carbon doped InGaP/GaAs HBTs. The b drift is compared for different HBT structures with varying burn-in percentages. Competing mechanisms are observed in which b can either increase or decrease during the initial stages of reliability testing. This b drift behavior is found to depend upon both the b burn-in percentage and the hydrogen concentration in the base. Hydrogenrelated defect mechanisms are found to adequately explain the observed b decreases, while non-hydrogen related recombination reduction mechanisms must be considered to account for the b increases observed during the initial stages of reliability testing.

In this paper, we present three techniques used to evaluate and monitor the hetero-guard ring (passivation ledge) properties of AlGaAs/GaAs HBTs. The techniques are simple enough that they are suitable for routine monitoring in a manufacturing environment.

Punching capacity is one of the main items in the design of both pre-stressed and non-pre-stressed flat slabs. All international design codes include provisions to prevent this type of failure. Unfortunately, there is no code provision for UHPC yet, and hence, the aim of this research is to experimentally investigate the impact of column dimensions and punching reinforcement on the punching capacity of post-tensioned slabs and compare the results with the international design codes' provisions to evaluate its validity. The test program included five slabs with a compressive strength of 120 MPa: one as a control sample, two to study the effect of column size, and the last two to study the effect of punching reinforcement. Comparing the results with the design codes showed that ACI-318 is more accurate with an average deviation of about 5%, while EC2 is more conservative with an average deviation of about 20%. Besides that, punching reinforcement reduces the size of the punching wedge by increasing the crack angle to 28° instead of 22° for slabs without punching reinforcement. Also, the results assure that both ductility and stiffness are enhanced with the increased column dimensions and punching reinforcement ratio.

This paper presents a fire resistance analysis of two-way reinforced concrete (RC) slabs. The study analyzes the effect of specific parameters-concrete cover thickness, span, and support conditions-on the fire resistance of the slabs. To that end, the slabs were exposed to Standard Fire ISO 834, and the 3D nonlinear numerical analyses were conducted in SAFIR2016. The results of the numerical analyses were evaluated against experimental results reported in the literature. The agreement between the two sets of results was satisfactory throughout the fire test. Nonetheless, to verify the obtained numerical results, all testing-related parameters must comply with the numerical simulation results. This comparison demonstrated the usefulness of numerical simulations in predicting the behavior of structures in fire conditions. In addition to the nonlinear numerical analysis, the fire resistance was calculated using the simplified method and tabulated data described in Eurocode 2 (Part 1.2) to assess the accuracy and reliability of fire safety regulations in the design of two-way slabs and identify significant differences between the design code and numerical analysis. The comparison showed that SAFIR2016 provides more accurate results by considering additional factors, such as tensile membrane forces, which increase the fire resistance of two-way slabs. According to the load-bearing criteria, the two-way slabs have high fire resistance, considerably higher than prescribed in the fire safety regulations, which ignore the positive effect of tensile membrane forces. According to the numerical analysis, the upper reinforcement in the compression areas of the slab's span was considered, which increased the fire resistance of the slabs. In contrast, according to the design codes, the contribution of this reinforcement is neglected. It was indicated that the increased concrete cover improves the fire resistance of the slabs. The vertical displacements increase by increasing the slab span, but according to the load-bearing criteria, all the slabs show fire resistance of over ten hours. In terms of bearing capacity, slabs with various support conditions show fire resistance of longer than ten hours. In terms of deflections, the supporting conditions of the slabs have a significant influence on their behavior. This study provides valuable insights into the fire resistance of two-way RC slabs and highlights the importance of considering specific parameters in the analysis.

The rainfall warning method for debris flows usually uses rainfall intensity and duration to establish an I-D relationship internationally and determine the rainfall warning threshold for debris flows. This method requires extensive rainfall data from debris flow events in the study area to establish the I-D relationship. However, some areas with occasional debris flows lack sufficient debris flow events to establish I-D relationships to determine rainfall warning thresholds. Therefore, this study uses the infiltration effect of water flow on gravel soil and establishes a rainfall intensity threshold judgment formula for debris flow initiation based on the limit equilibrium method. Taking the Taiqing debris flow that occurred in Laoshan, China, on June 13, 2018, as an example, the rainfall intensity and characteristics of the debris flow are analyzed. The maximum rainfall intensity during this rainfall process far exceeds the rainfall intensity threshold determined by the judgment formula. Using the judgment formula, it can be determined that the rainfall process will cause debris flow. The judgment result is consistent with the actual situation (where a debris flow occurred during the rainfall process). To further verify the accuracy of the judgment formula, the rainfall process of Typhoon Lichma on August 11, 2019, in the study area was analyzed. The rainfall process has a long history. Still, the rainfall intensity is much lower than the threshold of rainfall intensity for the initiation of debris flow, so this rainfall will not cause the occurrence of debris flow. The judgment result is consistent with the actual situation (no debris flow occurred during rains).

devices that produce a significant number of medium voltage and/or current, fast transients as a result of normal switching operations. 2. These fast transients have rise times in the sub-microsecond range with frequencies well into the megahertz region.

This study was carried out to examine the seismic performance of Kancingan house walls and the behavior of their timber frames, brick infill, and anchor nails during cyclic loading tests. Kancingan House, a timber frame building with brick infill walls, is a cost-effective and efficient method of wall construction commonly used in houses in Merauke, Indonesia. The experimental method was used to determine the seismic performance of the walls built using buswood with a module width of 100 cm and a height of 130 cm through cyclic load testing. The result showed a maximum lateral load of 26.43 kN with a displacement of 19.08 mm under compression loading and 28.78 kN under tensile loading with 15.6 mm displacement. The initial stiffness was measured at 5.03 kN and 9.59 kN/mm for compressive and tensile loading, respectively. Furthermore, ultimate load and displacement of 21.14 kN and 23.02 kN were obtained at a displacement of 30.68 mm under compressive loading and 25.23 mm under tensile loading. The ductility values of 10.76 and 9.78 were obtained under compressive and tensile loading. In conclusion, the study found that each wall element supports the seismic performance of the structure. As opposed to the timber frame, the infill walls have not suffered much damage except a hair crack because of the presence of anchor nails that keep the infill wall from collapsing when it loses its bond with the timber frames.

Hydrogen effects on fracture are ruled by its amounts in microstructural features that entrap the species and are actual sites of the embrittlement events. The paper aims to describe hydrogen delivery to diverse concurring microstructural positions basing on comprehensive diffusion-trapping theory that relies on minimal a priori constraints. The operation of multiple type traps near a crack in a model steel system that uptakes hydrogen during loading is elucidated. The calculations validate the postulate of local lattice-trap equilibrium and the dominance of hydrogen transport by only lattice-site diffuser flow. The simulations exhaustively describe the functioning of multifarious microstructural features and reveal their potentiality both to carry out the mechanistic effects of hydrogen and to retard hydrogen accumulation in the fracture nuclei.

In large-scale geologic storage projects, the injected volumes of CO 2 will displace huge volumes of native brine. If the designated storage formation is a closed system, e.g., a geologic unit that is compartmentalized by (almost) impermeable sealing units and/or sealing faults, the native brine cannot (easily) escape from the target reservoir. Thus the amount of supercritical CO 2 that can be stored in such a system depends ultimately on how much pore space can be made available for the added fluid owing to the compressibility of the pore structure and the fluids. To evaluate storage capacity in such closed systems, we have conducted a modeling study simulating CO 2 injection into idealized deep saline aquifers that have no (or limited) interaction with overlying, underlying, and/or adjacent units. Our focus is to evaluate the storage capacity of closed systems as a function of various reservoir parameters, hydraulic properties, compressibilities, depth, boundaries, etc. Accounting for multi-phase flow effects including dissolution of CO 2 in numerical simulations, the goal is to develop simple analytical expressions that provide estimates for storage capacity and pressure buildup in such closed systems.

Diagnosis of stator current has been presented by several authors for identifying various bearing and rotor faults in an induction motor. However, there is very limited literature covering the effect of interturn faults on the stator current pattern. This is due to the reason that the effect of motor interturn insulation faults in the initial stages being not discernable and any changes in the capacitive current components are negligibly very small and of very high frequency content. This paper deals with a simple technique, utilizing the effect of the interturn fault in modifying the high frequency components of the applied pulse width modulated (PWM) voltage. Insulation Resistance (IR) and Polarization Index (PI) are two universally accepted diagnostic tests for insulation tests. The change in insulation strength between the turns affects the capacitive component of the stator line current. Resulting changes in wave shapes of applied voltage have been studied with respect to both the distance of interturn faults from line end and reduction in the insulation strength; and hence in the insulation resistance value. The studies have been made by computer simulation and validated by experiments. There is ample evidence that an impending and progressing interturn fault can be identified in Adjustable Speed Drives driven by frequency converters by studying line end coil voltage waveforms.

The feasibility and efficiency of a low-invasive seismic retrofit solution for existing reinforced concrete frame systems, designed before the introduction of modern seismic-oriented design codes in the mid 1970s are herein experimentally investigated. A diagonal metallic haunch system is introduced at the beam-column connections to protect the joint panel zone from extensive damage and brittle shear mechanism while inverting the hierarchy of strength within the beam-column subassemblies and forming a plastic hinge in the beam. The experimental results from cyclic quasistatic tests on 2/3 scaled beam-column subassemblies in as-built and retrofitted configurations provided validated the conceptual design and practical implementation of the overall retrofit strategy.

The feasibility and efficiency of a low-invasive seismic retrofit solution for existing reinforced concrete frame systems, designed before the introduction of modern seismic-oriented design codes in the mid 1970s are herein experimentally investigated. A diagonal metallic haunch system is introduced at the beam-column connections to protect the joint panel zone from extensive damage and brittle shear mechanism while inverting the hierarchy of strength within the beam-column subassemblies and forming a plastic hinge in the beam. The experimental results from cyclic quasistatic tests on 2/3 scaled beam-column subassemblies in as-built and retrofitted configurations provided validated the conceptual design and practical implementation of the overall retrofit strategy.

In this combined experimental (deep ultraviolet resonance Raman (DUVRR) spectroscopy and atomic force microscopy (AFM)) and theoretical (molecular dynamics (MD) simulations and stress-strain (SS)) study, the structural and mechanical properties of amyloid beta (Aβ40) fibrils have been investigated. The DUVRR spectroscopy and AFM experiments confirmed the formation of linear, unbranched and β-sheet rich fibrils. The fibrils (Aβ40) n , formed using n monomers, were equilibrated using all-atom MD simulations. The structural properties such as β-sheet character, twist, interstrand distance, and periodicity of these fibrils were found to be in agreement with experimental measurements. Furthermore, Young's modulus (Y) = 4.2 GPa computed using SS calculations was supported by measured values of 1.79 ± 0.41 and 3.2 ± 0.8 GPa provided by two separate AFM experiments. These results revealed size dependence of structural and material properties of amyloid fibrils and show the utility of such combined experimental and theoretical studies in the design of precisely engineered biomaterials.

Chile is one of the main copper producers in the world. It is located in a geographical area where mega-earthquakes occur and this fact, together with the development of larger and higher sand tailings dams (with some facilities currently under development having final heights in excess of 250 m), requires that careful attention be paid to the safety and security of these facilities. In this paper, the main failure mechanisms of these sand tailings dams that have generated incidents of different magnitude involving loss of human life, significant environmental damage, and economic losses are described. Some key characteristics of reported incidents in Chile are presented, including failures resulting from the mega-earthquake that occurred on 27 February 2010 (Maule Region, Chile). Finally, the engineering practice and present Chilean regulatory framework, which have allowed progressive improvements in the construction, operation, and closure of such deposits, are described.

Process of failure of landslide dam can be classified into three types; overtopping, instantaneous slip failure and progressive failure. For similar hydraulic conditions peak discharge produced by failure of landslide dam depends on failure modes. Potential disaster in the downstream largely depends on magnitude of peak discharge so this study attempted to derive graphical relationships to predict failure mode by laboratory experiments in the flume. Critical channel slope for sediments, Mix 1-6 and Mix 1-7 are derived from flume experiments. Morevere, experimental data shows peak discharge produced by progressive failure is higher compare with peak discharge produced by instantaneous slip failure and overtopping. The concept of physically based integrated model is essential which can detect failure mode based on initial and boundary conditions and predict outflow hydrograph based on predicted failure mode for downstream hazard management.

The stability of natural rockslide dams with respect to sudden breaching is a major safety issue in mountain areas, although unbreached rockslide-dammed lakes such as Lochnagar in Central Otago, New Zealand, may persist in the landscape for millennia. Consequently it is important to attempt to understand the mode and drivers of these failures as they may impact on our expanding populations. The Lochnagar landslide-dam is located within the steep schistose mountains of the Southern Alps of New Zealand. During an extensive study of the site, structural and Schmidt hammer measurements were taken from the immediate area of the failure, as well as samples collected for laboratory analysis. Point load estimates of the uniaxial compressive strength were of 85 MPa perpendicular and 18 MPa parallel to the schistosity. The rock mass quality was estimated using the Geological Strength Index (GSI) with values of 35-45 observed. These results were used in a series of numerical modelling techniqu...

A technical approach for analyzing plant-specific data bases for vulnerabilities to dependent failures has been developed and applied. Since the main purpose of this work, to aid in the formulation of defenses to dependent failures, is different than that for other dependent failure analyses, the approach of this analysis is also critically different. For instance, component failures have been defined to include all types of component function loss (e.g., catastrophic, degraded, incipient). Also, the determination of component failure dependencies has been based upon identical failure mechanisms rather than failure modes. Consequently, in the context of this study, both the definition of component failure and a categorization scheme for component failure mechanisms are used to identify clusters of component failures which are termed common failure mechanism (CFM) events. Motor-operated valves (MOVs) in two nuclear power plant data bases have been analyzed with this approach. The analysis results include seven different failure mechanism categories; identified potential CFM events; an assessment of the risk-significance of the potential CFM events using existing probabilistic risk assessments (PRAs); and postulated defenses to the identified potential CFM events.

Liquefaction of soils is a well documented phenomenon, frequently resulting in catastrophic failures, environmental damage, financial loss and deaths. What seems to be less well appreciated is that liquefaction is simply another constitutive behaviour of soils that can be understood in terms of accepted physics and mechanics. Critical state theory is probably the most widely used mathematical model for the mechanics of soil behaviour since it captures the effect of density (or volume change) on soil behaviour. This paper presents an overview of how the behaviour of tailings (drained, undrained or cyclic resistance) can be quantified within the framework of critical state soil mechanics. It is postulated that paste at the time of deposition is slightly wetter than the critical state, and it is then possible to trace the change of state with the additional of more tailings and consolidation or desiccation. Knowledge of the in situ state allows the material behaviour to be described, and therefore engineering analyses can be carried out.

The evolution of System-on-Chip (SoC) designs involves the development of non-volatile memory technologies like Flash. Embedded flash (eFlash) memories are based on the floating-gate transistor concept and can be subject to complex hard defects creating functional faults. In this paper, we present a complete analysis of a particular failure mechanism, referred as disturb phenomenon. Moreover, we analyze the efficiency of a particular test sequence to detect this disturb phenomenon. Finally we conclude on the interest to develop new test infrastructure well adapted to the eFlash environment.

In the present investigation, laminated composite beams subjected to a bending static loading are studied in order to determine their failure mechanisms and the first ply failure (FPF) load. The FPF analysis is performed using a refined rectangular plate element. The present element is formulated based on the classical lamination theory (CLT) to calculate the in-plane stresses. To achieve this goal, several failure criterions, including Tsai-Wu, Tsai-Hill, Hashin, and Maximum Stress criteria, are used to predict failure mechanisms. These criterions are implemented within the finite element code to predict the different failure damages and responses of laminated beams from the initial loading to the final failure. The numerical results obtained using the present element compare favorably with those given by the analytic approaches. It is observed that the numerical results are very close to the analytical results, which demonstrates the accuracy of the present element. Finally, sever...

The reliability of chip scale package (CSP) components against mechanical shocks has been studied by employing statistical, fractographic, and microstructural research methods. The components having high tin (Sn0.2Ag0.4Cu) solder bumps were reflow soldered with the Sn3.8Ag0.7Cu (wt.%) solder paste on Ni(P)|Au-and organic solderability preservative (OSP)-coated multilayer printed wiring boards (PWBs), and the assemblies were subjected to the standard drop test procedure. The statistically significant difference in the reliability performance was observed: the components soldered on Cu|OSP were more reliable than those soldered on Ni(P)|Au. Solder interconnections on the Cu|OSP boards failed at the component side, where cracks propagated through the (Cu,Ni) 6 Sn 5 reaction layer, whereas interconnections on the Ni(P)|Au boards failed at the PWB side exhibiting the brittle fracture known also as "black pad." In the first failure mode, which is not normally observed in thermally cycled assemblies, cracks propagate along the intermetallic layers due to the strong strain-rate hardening of the solder interconnections in drop tests. Owing to strain-rate hardening, the stresses in the solder interconnections increase very rapidly in the corner regions of the interconnections above the fracture strength of the ternary (Cu,Ni) 6 Sn 5 phase leading to intermetallic fracture. In addition, because of strain-rate hardening, the recrystallization of the as-soldered microstructure is hindered, and therefore the network of grain boundaries is not available in the bulk solder for cracks to propagate, as occurs during thermal cycling. In the black pad failure mode, cracks nucleate and propagate in the porous NiSnP layer between the columnar two-phase (Ni 3 P ϩ Sn) layer and the (Cu,Ni) 6 Sn 5 intermetallic layer. The fact that the Ni(P)|Au interconnections fail at the PWB side, even though higher stresses are generated on the component side, underlines the brittle nature of the reaction layer.

Failure modes and mechanisms under mechanical shock loading were studied by employing the statistical and fractographic research methods, and the finite element (FE) analysis. The SnAgCu-bumped components were reflow-soldered with the SnAgCu solder paste on Ni(P) Au-coated and organic solderability preservative-coated multilayer printed wiring boards with and without micro-via structure in the soldering pads. The component boards were designed, fabricated, assembled, and drop tested according to the JESD22-B111 standard for portable electronic products. The test data were analyzed by utilizing the Weibull statistics, and the characteristic lifetimes ( ) and shape parameters ( ) were calculated. Statistically significant differences in the reliability were found between the different coating materials and pad structures. The results on the failed assemblies showed good correlation between the failure modes and the FE calculations. Under high deformation rates the solder material undergoes strong strain-rate hardening, which increases the stresses in the interconnections as compared to those in the thermal cycling tests. Therefore, the failure mechanisms under high deformation rates differed essentially from those observed in thermal cycling tests.

Slope failures are disasters that happen all around the world. Occurrence of slope failures depends on number of factors. To safeguard the safety of the public from slope failure hazards, proper geotechnical input by the engineers with geotechnical experience is very important. The geotechnical input includes four important stages namely, planning, design, construction and maintenance. Whenever failures occur, engineers are responsible to the problems. The paper observed the assessment of slope failures.

The mechanical stability of solder joints with Pd added to Sn-Ag-Cu alloy with different aging conditions was investigated in a high-G level shock environment. A test vehicle with three different strain and shock level conditions in one board was used to identify the joint stability and failure modes. The results revealed that Pd provided stability at the package-side interface with an overall shock performance improvement of over 65% compared with the Sn-Ag-Cu alloy without Pd. A dependency on the pad structure was also identified. However, the strengthening mechanism was only observed in the non-solder mask defined (NSMD) pad design, whereas the solder mask defined (SMD) pad design boards showed no improvement in shock performance with Pd-added solders. The effects of Sn grain orientation on shock performance, interconnect stability, and crack propagation path with and without Pd are discussed. The SAC305 + Pd solder joints showed more grain refinements, recrystallization, and especially mechanical twin deformation during the shock test, which provides a partial explanation for the ability of SAC305 + Pd to absorb more shock-induced energy through active deformation compared with SAC305.

LumenFlow from Zeeland, MI presents Surface Mount Optics (SMO) as solder-ready components designed to populate onto a PCB along with the electronics, using conventional assembly equipment. The assembly passes through the reflow oven to solder everything in place in a single pass. With SMO, there is no need for a post-reflow optical assembly process. We will review the design of the compound optic integrated into one piece as an SMO, for delivery to a contract manufacturer for easy pick-and-place assembly. We will also explain the durable material properties which make silicone preferable for demanding applications-including pick-and-place assembly-without scratching or melting in the process. Surface Mount Optics Simplify Manufacturing and Reduce Costs of Optical Assemblies Surface mount optics (SMO) are a relatively new concept in the lighting industry. This technology utilizes silicone optics placed directly on a PCB and allows for continuation through the solder reflow oven. Because silicone can withstand solder reflow temperatures and maintain its optical performance, there is no need for a post-reflow assembly step. No holders, fasteners, or glue are necessary. Most secondary optical component materials for LEDs are not able to withstand solder reflow temperatures (usually more than 250˚C). They may crack, slump, or melt, causing a degradation of optical and mechanical properties, as well as low transmission or other limitations in optical performance.

Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (-35 K) spectrographic astronomy measurements in the nearinfrared region. Functioning as a focal plane object selection device, the MSA is a 2-D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA are closepacked silicon nitride shutters (cell size of 100 x 200 pm) patterned with a torsion flexure to allow opening to 90 degrees. A layer of magnetic material is deposited onto each shutter to permit magnetic actuation. Two electrodes are deposited, one onto each siiuiier and another onio the support snucmre side-waii, permitting electrostatic latching and 2-D addressing. New techniques were developed to test MSA under mission-similar conditions (8 K 5 T < 300K). The "magnetic rotisserie" has proven to be an excellent tool for rapid characterization of MSA. Tests conducted with the magnetic rotisserie method include accelerated cryogenic lifetesting of unpackaged 128 x 64 MSA and parallel measurement of the magneto-mechanical stiffness of shutters in "pathfinder" test samples containing multiple MSA designs. Lifetest results indicate a logarithmic failure rate out to -10' shutter actuations. These results have increased our understanding of failure mechanisms and provide a means to predict the overall reliability of MSA devices. a To be built by the European Space Agency. Obtained from MEMS Exchange, Reston, VA 20191.

This paper performs the research on failure mechanism of single-layer steel reticulated domes with the reinforced concrete substructure subjected to sever earthquakes. Based on ABAQUS, this paper built user-defined material subroutines of the steel and the reinforced concrete, which took material non-linearity and the material damage accumulation into consideration. The failure mechanism of reticulated domes with reinforced concrete substructures under severe earthquakes is studied by the nonlinear dynamic response analysis. Three different failure modes of single-layer reticular domes with different sizes of reinforced concrete substructure are illustrated. Failure criterion is put forward to discriminate the failure modes and to estimate the critical load strength for single-layer reticular domes based on the structural damage theory. It has been found that reinforced concrete substructure has significant impact on the failure behaviors and the critical load of reticulated domes under seismic loads. It is essential to consider the influence of the reinforced concrete substructure upon the failure behaviors in the structural analysis and design process of reticular domes.

This paper introduces a method to improve the electrostatic adhesion force of an electrostatic/microstructured (gecko-like) adhesive using a tunable dielectric layer doped with a highly polarizable material, Copper(II) Phthalocyanine. The dopant increases the relative permittivity of the base elastomer by more than two times. Numerical simulations demonstrate that increasing the dielectric's relative permittivity increases the electroadhesion force, and experimental results verify this by showing that adhesion of a flat (non-microstructured) sample can be improved up to four times. Adding microstructured adhesive elements on top of the doped layer yields a 2x improvement on a variety of materials.

The mechanical stability of solder joints with Pd added to Sn-Ag-Cu alloy with different aging conditions was investigated in a high-G level shock environment. A test vehicle with three different strain and shock level conditions in one board was used to identify the joint stability and failure modes. The results revealed that Pd provided stability at the package-side interface with an overall shock performance improvement of over 65% compared with the Sn-Ag-Cu alloy without Pd. A dependency on the pad structure was also identified. However, the strengthening mechanism was only observed in the non-solder mask defined (NSMD) pad design, whereas the solder mask defined (SMD) pad design boards showed no improvement in shock performance with Pd-added solders. The effects of Sn grain orientation on shock performance, interconnect stability, and crack propagation path with and without Pd are discussed. The SAC305 + Pd solder joints showed more grain refinements, recrystallization, and especially mechanical twin deformation during the shock test, which provides a partial explanation for the ability of SAC305 + Pd to absorb more shock-induced energy through active deformation compared with SAC305.

The geomechanical modelling of failure and post-failure stages of rainfall-induced shallow landslides represents a fundamental issue to the proper assessment of failure conditions and recognizes the potential for long travel distances of the failed soil masses. Considering that these phenomena are among the most catastrophic natural hazards, as a contribution to the topic this paper discusses the potential of a hydromechanical coupled finite element model (FEM) to analyze the post-failure stage using an advanced constitutive model. In particular, simple undrained triaxial tests and experimental evidence of centrifuge tests are reproduced first, for both loose and dense soils. Then, two slope scale benchmarks are analyzed in the cases of vertical downward or horizontal water seepage and for both loose and dense soils. Compared with results obtained through standard limit equilibrium analyses, the coupled FEM provides a new comprehensive framework for failure and post-failure scenario...

The response of structural components subjected to blast loads result in deformation strain rates in the range of 10^ s&quot;^ to 10* s&quot;\ Hitherto the effects of temperature dependent material properties for such situations have been excluded in both the experimental and numerical predictions. This phenomenon is extremely difficult to measure for the experimental tests and has only recently been included in the analysis. This paper describes a series of tests in which circular steel plates are subjected to a central localised blast load. The numerical predictions indicate that failure occurs as a result of a thermo-mechanical instability and localised shear banding. Hitherto, the failure criterion for the tearing mechanism has been considered to be one of either a stress based criterion, a strain based criterion, or an energy based criterion. These localised shear bands provide new insights into the subsequent failure and tearing mechanism through the thickness of the plate.

Electrostatic discharge (ESD) plays an important role in the hard or soft failure of electronic products due to its high voltage, strong electric field, instantaneous high current, and a wide spectrum electromagnetic radiation. A field-circuit co-simulation method combining circuit elements and full-wave 3D model is applied to investigate ESD effects on a system including ESD generator, electronic device and IC chips on PCB, which can obtain both the electromagnetic field and the voltage/current information. The signal transmitting can be monitored under ESD-event when different discharge voltage polarity and protective enclosures are applied. Moreover, transient voltage suppressors can be appended to the field-circuit co-simulation model and their effects to ESD protection are investigated. The research on the field-circuit co-simulation of electronic products puts forward a more practical simulation method for electrostatic discharge. INDEX TERMS Electrostatic discharge, field-circuit co-simulation, full-wave 3D model, signal transmitting.