Failure Front Research Articles

Compressive failure and fragmentation of fused silica glass under quasi-static loading

This paper investigates the failure and post-failure fragmentation processes of fused silica glass cylinders under quasi-static compression, addressing the effects of surface finish on apparent strength. The compressive strengths of cylinders with side-polished sides under dry friction conditions (PSG-D) or lubricated conditions (PSG-L) were 2.52 GPa and 2.32 GPa, respectively. In situ observations showed that these specimens fractured from either the top or bottom contact surfaces, and that friction between the specimen and the loading anvil delayed the development of surface cracks. The unpolished rough side specimens (RSG-D) under dry friction conditions failed at a much lower level of 1.54 GPa, initiated by defects in the side surfaces. Specimens "explosively" fragmented upon failure. The propagation speed of the failure front ranged from 1800 to 2800 m/s. The average sizes and distributions of the fragments were determined through statistical analysis, with results showing reasonably close agreement with theoretical estimations.

Experimental investigation of failure diffusion in brittle materials subjected to low-speed impact

The generalized driving force and local shear resistance are introduced to reveal the intrinsic mechanism of failure diffusion in brittle materials subjected to low-speed impact. Two experiment techniques (i.e. the Split Hopkinson pressure bar (SHPB) test and sphere penetration test), four specimen configurations (i.e. cuboid, trapezoid, sphere, and plate specimens), and three transparent brittle materials (i.e. polymethyl methacrylate (PMMA), glass, and transparent ceramics ALON) are employed in the present study. The generation and propagation of the failure front in the specimens are traced and analyzed based on the high-speed photography and the DIC method. The calculated equivalent strain fields vary greatly with configurations of specimens. The generalized driving force (e.g. calculated based on the strain field) and the shearing diffusion resistance (e.g. calculated based on the strain field and the transmission stress profile) are then proposed to illustrate respectively the deformation-gradient induced driving force and the local shear in the shear-activated process of failure diffusion. The results show that they both increase rapidly in the formation process of the failure front and decrease to almost zero after the specimen is failed; while the velocity of the failure front increases exponentially with the increase of the driving force, and decreases with the increase of local shearing resistance. The relations of the two generalized forces to the geometric structures are obtained, and the local dynamic strength is firstly revealed by the evolution of the shearing resistance. The results are helpful for the profound understanding of the failure mechanism of brittle material subjected to impact loading.

Deformation evolution and diffusion characteristics of polymethyl methacrylate under impact loading

Dynamic compression experiments on cubic polymethyl methacrylate (PMMA) specimens and two kinds of trapezoid PMMA specimens are carried by changing the transmission bars into steel bar and aluminum bar on the experimental device of split Hopkinson pressure bar (SHPB). The compression processes of PMMA specimens are recorded by high-speed photography, and the breakage processes of PMMA specimens are analyzed based on the force displacement curves and high-speed images. The evolutions of deformation and diffusion resistances of PMMA specimens under impact loading are discussed. The results show that the failure of the sample is caused mainly by the partial failure front at the contact end, and then the failure front propagates to the inside of the sample, leading the sample to break. The failure front of cubic sample is generated preferentially at the transmission end under low speed impact and at the incident end under the higher speed impact. After changing the shape of the specimen and the material of the transmission bar, the relaxation phenomenon is prominent, and the failure front occurs only at the incident end. The compressive deformation of the trapezoid sample before breakage is non-uniform, and the stress and strain in the sample gradually decrease with the increase of the cross section, and show a linear diffusion distribution. The strain distribution and shear activation diffusion equation are used to obtain the generalized diffusion resistance distribution of the failure front. The generalized diffusion resistance increases first in front of the failure front and decreases after the failure front, and the amplitude of the generalized diffusion resistance is related to the release of local strain energy.

Study on deformation evolution and diffusion characteristics of PMMA under impact loading

Dynamic compression experiments were carried out on cubic PMMA specimens and two kinds of trapezoid PMMA specimens by changing the transmission bars to steel and aluminum bar with the Loading device of split Hopkinson pressure bar (SHPB). The compression process of PMMA specimens was recorded by high-speed photography, and the breakage process of PMMA specimens was analyzed based on the force displacement curves and high-speed images. The evolution of deformation and diffusion resistance of PMMA specimens under impact loading was discussed. The results show that the failure of the sample is mainly caused by the partial failure front at the contact end, and then the failure front propagates to the inside of the sample and leads to the breakage of the sample. The failure front of cubic samples is preferentially generated at the transmission end under low speed impact and generated at the incident end under the higher speed impact. After changing the shape of the specimen and material of the transmission bar, the relaxation phenomenon is obvious, and the failure front only occurs at the incident end. The compressive deformation of the trapezoid sample before breakage is non-uniform, and the stress and strain in the sample gradually decrease with the increase of the cross section, and show a linear diffusion distribution. The strain distribution and shear activation diffusion equation were used to obtain the generalized diffusion resistance distribution of the failure front. The generalized diffusion resistance increases first in front of the failure front and decreases after the failure front and the amplitude of the generalized diffusion resistance is related to the release of local strain energy.

New Insights into the Failure Front Phenomenon and the Equation of State of Soda-Lime Glass Under Planar Plate Impact

A systematic study has been performed to gather more detailed experimental information on the equation of state and the Hugoniot elastic limit (HEL) of soda-lime glass as well as the failure front phenomenon. The key innovations of this study comprise experimental as well as analytical aspects. On the one hand, an extensive planar plate impact (PPI) test series has been carried out over a wide range of shock loading stress levels instrumented with two high-speed cameras and laser interferometers (PDV and VISAR). On the other hand, a systematic analysis concept has been developed and evaluated, including a combination of Lagrange diagrams with velocity profile data and a derivation of the equation of state together with an error estimation. Impact velocities ranged from 500 to 3000 m/s resulting in loadings of the soda-lime glass targets between 3.5 and 20.8 GPa. For stress levels between 3.5 and 6.7 GPa two high-speed cameras with 5 Mfps, positioned at the side and rear of the specimens, enabled the observation of shock waves and two different kinds of failure fronts. Therefore, visual information could be gathered not only in the purely elastic regime, but also in the transition region above 4 GPa and at stress levels beyond the HEL. The HEL of the soda-lime glass is determined to left(5.0 pm 0.2right) mathrm{GPa}. For the onset of an internal failure front a minimum longitudinal stress between 3.8 and 3.9 GPa is identified. The evaluated failure front velocities range from 800 to 2100 m/s. From the observed release response a minimum spall strength of 6.7 GPa and release wave velocities between 5740 and 9500 m/s are deduced.

Numerical modeling and prediction of adhesion failure of adhesively bonded composite T-Joint structure

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

Long Term Nomacopan Administration Results in Complete Transfusion Independence in Previously Transfusion-Dependent PNH Patients

BACKGROUND Nomacopan, a small protein biologic previously known as Coversin (AK576), is in Phase III clinical development for PNH. Patients completing COBALT, a three-month Phase II trial in complement inhibitor naïve PNH patients, were eligible to move into CONSERVE, a long-term safety and efficacy surveillance study. Seven of 8 patients completed COBALT and all moved into the long-term safety study and received treatment with nomacopan for between 20 and 28 months. Six of the patients were transfusion dependent prior to treatment with nomacopan. METHODS The haematological, clinical and safety results of patients in CONSERVE have been analysed. RESULTS: All patients showed reduction of intravascular haemolysis as evidenced by significant fall of lactate dehydrogenase (LDH) levels and stabilisation of haemoglobin between 1 to 19 months. Of 6 patients who were transfusion dependent prior to entry to COBALT 3 (50%) became transfusion independent during the 12 week trial and 1 became transfusion independent in the 6 months following the trial. All 4 of these patients have remained transfusion independent. Since January 2019 both of the last two transfusion-dependent patients have been transfusion independent for more than 6 months. Patients in COBALT and CONSERVE have had no drug related serious adverse events, no major adverse vascular events, complete inhibition of terminal complement activity at all time points and the drug has been well tolerated. SUMMARY AND CONCLUSIONS: Long term complement inhibition with eculizumab is known to result in reduction of transfusion requirements in patients with PNH. In a 66-month long-term study of PNH patients treated with eculizumab, 64 of 78 (82.1%) previously transfusion dependent patients achieved transfusion independence. [i] In this, much smaller study, 6 of 6 previously transfusion dependent patients stabilised their haemoglobin and became transfusion independent (defined here as no transfusion for 6 or more months), two of these finally reaching this point between 18 and 21 months after starting treatment. The data indicate that nomacopan is safe and well tolerated for long term treatment of PNH by patient self-administration and offers significant therapeutic benefit to patients in terms of transfusion independence, an outcome of key importance to clinicians. It is possible that nomacopan may assist in improving bone marrow activity through its inhibition of LTB4 and the effect on the innate immune system which has been linked to bone marrow failure and clonal deletion and recovery. [ii] [iii] [i] Hillmen P et al. Long-term safety and efficacy of sustained eculizumab treatment in patients with paroxysmal nocturnal haemoglobinuria. Br J Haematol 2013 162(1) 62-73 [ii] Bagby GC. The Role of Innate Immune Dysfunction in Inherited Bone Marrow Failure. Blood 2014 124:SCI-19; [iii] Trompouki E et al. Inflammatory signaling in bone marrow failure and hematopoietic malignancy (Editorial) Front. Immunol. 2017: 8(660). Disclosures Kulasekararaj: Alnylam: Membership on an entity's Board of Directors or advisory committees; Ra Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Achillion: Consultancy; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Akari: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Weston-Davies:Akari Therapeutics Plc: Employment, Equity Ownership. Robak:Acerta: Research Funding; Morphosys AG: Research Funding; Takeda: Consultancy, Research Funding; UCB: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel grant, Research Funding; Amgen: Consultancy, Other: Travel grant; Roche: Consultancy, Other: Travel grant, Research Funding; Abbvie: Consultancy, Honoraria, Other: Travel grant, Research Funding; Gilead: Consultancy, Research Funding; BeiGene: Consultancy, Research Funding. Nunn:Akari Therapeutics Plc: Employment, Equity Ownership. Szmigielska-Kaplon:Novartis: Consultancy, Honoraria; Alexion: Honoraria; Sanofi: Consultancy, Honoraria. Hill:Apellis: Honoraria; Alexion: Honoraria; Akari: Honoraria; Ra Pharma: Honoraria; Bioverativ: Honoraria; Roche: Honoraria; Regeneron: Honoraria; Novartis: Honoraria.

Three-dimensional adhesion failure analysis of the single lap joint having pre-embedded circular defects

The present research aims to study the growth of the circular adhesion failure pre-existing at the interfaces of the strap adherend and the adhesive in a single lap joint. Three-dimensional nonlinear finite element analysis of adhesively bonded single lap joints made with high strength steel adherends under uniformly applied extension have been carried out. The interfacial stresses and strain energy release rate values, being indicative parameters, in the growth of the adhesion failures are computed in the vicinity of the pre-existing circular adhesion failure fronts when the load on single lap joint increases till failure. The magnitudes of the strain energy release rate are computed using the virtual crack closure technique. The results show that the sizes of the adhesion failure significantly influence the magnitudes of the interfacial stresses, the three modes of strain energy release rates and the load-bearing capacity of the single lap joint. The finite element analysis predicts that pre-embedded circular adhesion failures will not have grown from the pre-embedded circular adhesion failure front, instead the failure will be initiated from the overlap ends upon loading for the adhesive bonded single lap joint made with strong adherends and AV119 adhesive. The finite element analysis also proposes a method to calculate the strength of this type of joint configurations using the global shear strength of the adhesive and the intact bonded area. The finite element analysis predicted failure strength of the single lap joint is in good agreement with the experimentally obtained strength for the single lap joint containing pre-existing circular adhesion failure.

Effect of the aspect ratio of the pre-existing rectangular adhesion failure on the structural integrity of the adhesively bonded single lap joint

Non-linear three dimensional (3-D) finite element analyses (FEA) of the single lap joints (SLJs) having pre-existing rectangular adhesion failure in the interface of the strap adherend and the adhesive have been carried out. The effect of the size, the shape and the aspect ratio of the pre-existing rectangular adhesion failure on (i) the strength, (ii) the interfacial stresses and (iii) the strain energy release rates (SERRs) in the vicinity of the adhesion failure front have been presented in this research work. The SLJ is subjected to uniformly applied tensile load. The adherends are made with very high strength steels and the adhesive is a commercially available AV119. The analyses of the adhesion failure propagation have been carried out by sequentially releasing the constraints of the nodes ahead of the pre-existing adhesion failure front in finite element model. The SERR values in the vicinity of the adhesion failure fronts are computed using the virtual crack closure technique (VCCT) for assessment of the structural integrity of the SLJ. The strength of the SLJ, the interfacial stresses, and the three modes of strain energy release rates (SERRs) have been found to be significantly affected by the shape and size of adhesion failures. The SERRs and interfacial stresses along the rectangular adhesion failure front are compared with the corresponding values around the circular adhesion failure front of same area, pre-existing in the SLJ. It is observed that the circular and rectangular adhesion failures of the same area will have dissimilar growth rate and the mode II is the dominant failure mode. The total strain energy release rate and the failure strength, computed from the 3-D FEA of the SLJ is in good agreement with the experimental fracture toughness of the AV119 adhesive and the experimentally obtained failure loads, respectively.

Mechanoluminescent studies of failure line on double cantilever beam (DCB) and tapered-DCB (TDCB) test with similar and dissimilar material joints

Mechanoluminescent (ML) studies were investigated for double cantilever beam (DCB) and tapered-DCB (TDCB) tests, and the following information was recorded. (1) The ML behavior on the top surface of the adherend perfectly synchronizes the shape of the failure front at the bond line. Thus, ML sensing can be utilized as a monitoring indicator of the behavior and fracture toughness at a crack frontline from outside the adherend. (2) The failure front of a DCB specimen under dissimilar material bonding, consisting of CFRP and CFRTP in particular, can be visualized and considered as a winding line. (3) The failure process zone (FPZ) on the bond line for DCB and TDCB specimens was successfully visualized based on the mechanoluminescence, and the area of the TDCB specimen was determined to be much longer than that of the DCB specimen.

Adhesion failure propagation analyses of Spar Wingskin Joints made with curved laminated FRP composite and FGM panels

Spar Wingskin Joint (SWJ) comprises of a thin spar which overlaps and is co-cured to a thick wingskin by suitable adhesive materials. These joints are mostly used in integral modular fabrication of aircraft and fuselage wing structures usually made with curved laminated Fibre Reinforced Polymeric (FRP) composite panels. This paper deals with the analyses of initiation of adhesion failure and its propagation in SWJs subjected to transverse loadings using Finite Element Analyses (FEA) and fracture mechanics approach. Normal and shear stress distributions at different interfacial locations between the adherends and the adhesive have been evaluated. Tsai-Wu coupled stress failure criteria have been used to identify the location of onset of adhesion failure. The critical location for onset of adhesion failure has been found to be at the toe-end of the spar wingskin overlap region. Pre-embedded adhesion failure has been simulated at this location and Strain Energy Release Rate (SERR) components corresponding to Mode I, Mode II and Mode III of adhesion failure have been determined using the principle of Virtual Crack Closure Technique (VCCT). Rate of propagation of adhesion failure has been evaluated by sequential release of Multi-Point Constraint (MPC) and contact finite elements provided at the pre-embedded failure front. It has been observed that Mode I component of SERR primarily governs the process of adhesion failure propagation. The appropriate spar overlap length on the wingskin has been determined in order to prevent adhesion failure. Further, an attempt has been made to improve the structural integrity of the SWJ by reducing the stress concentration at the ends of spar and wingskin overlap. This has been achieved by obtaining a favourable stress distribution over the entire joint structure by using Functionally Graded Materials (FGM) in the spar and wingskin adherend instead of FRP composite panels. Exponential gradation indices have been used for material grading of the spar and wingskin adherends. It has been seen that peel and shear stresses and values of SERR components as well as total SERR reduce significantly by use of FGMs with suitable exponential material grading index.

Supershear damage propagation and sub-Rayleigh crack growth from edge-on impact: A peridynamic analysis

Edge-on impact experiments on AlON, a transparent ceramic with superior ballistic performance, show combined intergranular and transgranular fracture. An initial fast-propagating damage front transitions into slower-propagating localized cracks. We develop a peridynamic model for polycrystalline AlON to investigate the failure evolution observed in experiments. We use a computational polycrystalline structure with the same average grain size as the samples used in experiments. The peridynamic model helps explain the reasons behind the observed failure front supershear propagation speed (higher than 2 times the shear wave speed), and the subsequent transition to sub-Rayleigh propagating localized cracks. The computed propagation speeds for the damage front, and the cracks that emanate from it, match very well those measured in experiments. Elastic anisotropy, material microstructure, and brittle failure are the only ingredients used here to determine damage evolution in edge-on impact on brittle polycrystalline materials, under no confinement. Other possible dissipation mechanisms, like twinning, plasticity, friction, are not included in the model. These are likely second-order effects in the evolution of damage and failure for this material and at these impact speeds.

Episodic growth of fold-thrust belts: Insights from Finite Element Modelling

The sequential development of a fold-thrust belt was investigated using 2D Finite Element Modelling (FEM). The new model results show that a thrust system is typically composed of three distinct regions: the thrust wedge, pre-wedge, and undeformed region. The thrust wedge involves growth that repeats episodically and cyclically. A cycle of wedge building starts as frontal accretion occurs, which is accompanied by a rapid increase in wedge width reducing the taper angle below critical. In response to this, the wedge interior (tracked here by the 50 m displacement position) rapidly propagates forwards into a region of incipient folding. The taper angle progressively increases until it obtains a constant apparent critical value (∼10°). During this period, the wedge experiences significant shortening after a new thrust initiates at the failure front, leading to a decrease in wedge width. Successive widening of the wedge and subsequent shortening and thrusting maintain a reasonably constant taper angle. The fold-thrust belt evolves cyclically, through a combination of rapid advancement of the wedge and subsequent gradual, slow wedge growth. The new model results also highlights that there is clear, although minor, deformation (0–10 m horizontal displacement) in front of the thrust wedge.

Bimodularity of interface layer and curing stress coupling effects on mixed mode fracture behaviour of functionally graded tee joint

Adhesive bonded tee joints are being used excessively in civil, military aircraft and ship building industries to join light weight Fiber reinforced Polymeric (FRP) laminates to other metal or composite structures. The mismatch of thermo-mechanical properties between adherend and adhesive bond line induces residual curing stresses even during manufacturing stages resulting in unaccounted failure and fracture behaviour of adhesive joints. The present work investigates the influence of bimodulus behaviour of adhesive and curing stresses on interface delamination fracture behaviour of tee joints by conducting a sequential thermal and geometrically non-linear finite element analysis (FEA) iteratively for evaluating strain energy release rate along the delamination front. The stress dependent elasticity problem of interface fracture has been studied based on the concepts of Modified Crack Closure Integral (MCCI) for different numerical specimens with tension compression modulus ratio R varying from 1 to 5 along the bond line for the respective functionally graded bimodular adhesively bonded tee joint. It is illustrated that the variation of bimodularity index has a strong influence on the interface delamination crack propagation characteristics apart from the other aspects of functionally grading and thermo-elastic anisotropy. The influence of bimodularity in comparison to functionally grading is found to be much more significant on mixed-mode fracture behaviour depicting dissimilar variation of GI, GII and GIII along the interface failure front indicating retardation of the interfacial failure propagation rate over certain zones of adherend.

Effects of functionally graded adhesive on failures of socket joint of laminated FRP composite tubes

The effects of functionally graded adhesive on failures in socket joint of laminated FRP composite tubes are analyzed in the present research. Various types of failures in the socket joint have been studied using strength of materials and fracture mechanics approach. The critical location in the socket joint has been identified using strength of material approach. Subsequently, the principle of fracture mechanics has been employed with a presumption that a circumferential failure front pre-exist at the critical location in the socket joint. The failure evolution in the functionally graded adhesively bonded socket joint of laminated FRP composite tubes and fracture behaviour of embedded failures have been discussed with respect to the variation of fracture parameters such as the individual modes of strain energy release rates (SERR) along the failure front. The novelty of functionally graded adhesive is introduced with linear function profile in order to improve the failure growth resistance of the socket joint structure. Based on the failure indices, it has been observed that free edges of the coupling region are more vulnerable zones for interfacial failure initiation as failure indices for all the critical surfaces of bond layer are found to be the highest at those locations. Further, the effects of functionally graded adhesive with varied modulus ratios on failure onset are observed for critical surface. It has been observed that the failure onset and its propagation shall be reduced/delayed due to the use of functionally graded adhesive in the joint. Based on the failure growth studies, it has been noticed that interfacial failure propagation is governed by in-plane shearing mode and, other modes are insignificant in propagation. Efforts have been made to enhance the crack/damage growth resistance properties of the bonding material. Series of FE simulations have been carried out for varied interfacial failure length in tubular socket joint with functionally graded adhesive in order to achieve the significant effect of material gradation on SERR. It has been noticed that the effect of material gradation of adhesive on SERR is more predominant for shorter interfacial failure length which leads to delay the failure growth.

Dissipative processes under the shock compression of glass

New experimental data on the behavior of the K8 and TF1 glasses under shock-wave loading conditions are obtained. It is found that the propagation of shock waves is close to the self-similar one in the maximum compression stress range 4-12 GPa. Deviations from a general deformation diagram, which are related to viscous dissipation, take place when the final state of compression is approached. The parameter region in which failure waves form in glass is found not to be limited to the elastic compression stress range, as was thought earlier. The failure front velocity increases with the shock compression stress. Outside the region covered by a failure wave, the glasses demonstrate a high tensile dynamic strength (6-7 GPa) in the case of elastic compression, and this strength is still very high after transition through the elastic limit in a compression wave.

Numerical modeling of injection, stress and permeability enhancement during shear stimulation at the Desert Peak Enhanced Geothermal System

Creation of an Enhanced Geothermal System relies on stimulation of fracture permeability through self-propping shear failure that creates a complex fracture network with high surface area for efficient heat transfer. In 2010, shear stimulation was carried out in well 27-15 at Desert Peak geothermal field, Nevada, by injecting cold water at pressure less than the minimum principal stress. An order-of-magnitude improvement in well injectivity was recorded. Here, we describe a numerical model that accounts for injection-induced stress changes and permeability enhancement during this stimulation. We use the coupled thermo-hydrological–mechanical simulator FEHM to (i) construct a wellbore model for non-steady bottom-hole temperature and pressure conditions during the injection, and (ii) apply these pressures and temperatures as a source term in a numerical model of the stimulation. A Mohr–Coulomb failure criterion and empirical fracture permeability is developed to describe permeability evolution of the fractured rock. The numerical model is calibrated using laboratory measurements of material properties on representative core samples and wellhead records of injection pressure and mass flow during the shear stimulation. The model captures both the absence of stimulation at low wellhead pressure (WHP ≤1.7 and ≤2.4MPa) as well as the timing and magnitude of injectivity rise at medium WHP (3.1MPa). Results indicate that thermoelastic effects near the wellbore and the associated non-local stresses further from the well combine to propagate a failure front away from the injection well. Elevated WHP promotes failure, increases the injection rate, and cools the wellbore; however, as the overpressure drops off with distance, thermal and non-local stresses play an ongoing role in promoting shear failure at increasing distance from the well.

Performance Measurement System in Banking Services in India

Increased competition and technological breakthroughs in banking services has sidelined the customer focus and opened new vistas of managing figures of success not only to show past performance rather as a strategy to sustain in business. This has led to many practices in banking as non standardized services. The non- core businesses subsidizing the core businesses on failure fronts also cause this deviation. Performance of any organization is one of the mechanisms to gain people's commitment towards achieving the stated objectives of the organization. This study is an attempt to address the questions, which includes: (a) the different performance measurement systems adopted by Indian companies in banking services; (b) the approaches used to measure the performance of the organization in banking services in India; (c) the different factors distorting the PMS of the organization and (d) the effectiveness of PMS and need for the change in the existing PMS. This study also aims to establish an equation between performance measurement practices and environmental variables in Indian banking services. The primary data as well as secondary data has been used to decipher the trends in performance measurement practices in banking services in India. The empirical study deciphers the trend used to identify the potential of banking services in context of economic and social changes underway in India. Although, banking industry is lagging behind in the level of understanding of performance measurement system, but the sector realizes the importance of effective PMS for the organization. The different banking companies are found to use different approaches to measure the performance. The performance measurement systems adopted by Indian companies are also found to be different than that followed by multinational banks. The role of social, economic and cultural factors is being realized by most of the service providers in India. Therefore, the development of performance measurement practices in this dynamic world is need of banking service business.

A Study of the Effect of Basic Network Characteristics on System-of-System Failure Propagation

Real life examples of large system level failures in complex networked system are fairly common, with national and regional level power grids providing numerous cases where local failures have resulted in broad systemic failures. As large networked systems-of-systems are increasingly common, their susceptibility to large scale failures is of significant interest. This paper presents the results of a study using a simple model to investigate the impacts of basic architecture characteristics on the spread of failures through a system-of-system after an initial failure occurs.The study reported here uses a non-symmetric inter-grid only failure model to investigate the sensitivity of failure progression due to failure in dependent nodes in a system-of-system composed of dependent grid networks to the several basic parameters, including initial failure size, grid node density and grid interdependency radius.Despite the use of only an inter-grid failure mechanism, the study results generally showed a rapid failure propagation to a steady state condition. A possible mechanism for this return to steady state in terms of the expanding failure front and probability that existing dependent nodes lie outside of the failure front is discussed.

Thermodynamic models of phase transformations and failure waves

Dynamics and quasi-statics of heterogeneous systems with sharp interfaces are analyzed. We dwell on two particular problems: dynamics of two-layered liquid incompressible planets with phase interfaces and failure fronts in brittle solids. In the former, the dynamics of the interfaces is controlled by the equality or jump in the scalar chemical potential. Similarly, in the latter example, it is controlled by the asymmetric tensorial chemical potential. We made several simplifying assumptions to reduce the system of partial differential equations to the systems of ordinary differential equations. We briefly touch on still existing obstacles.