Total Energy Release Rate Research Articles

Numerical study on the blast mitigation effect of an inner-grooved straight tube

A series of numerical simulations were conducted to clarify the shock–structure interaction inside an inner-grooved straight tube and the mitigation effect of the groove structure on the expansion of the blast wave at the exit. The results showed that the periodic grooves of the groove structure generate multiple reflected shock waves. Each time a shock wave reaches a groove, some of the shock wave and gas flow behind it propagates directly through the downstream groove, and the rest is reflected to the upstream groove. This splitting decreases the shock wave strength inside the tube. To clarify the blast mitigation effect of the configuration of the groove structure, parametric studies were conducted that changed the height and interval of the periodic grooves. The flow characteristics inside the tube were analyzed to understand the blast mitigation efficiency of the groove structure. The groove height had a significant impact on the blast mitigation efficiency, and the optimal interval for maximum blast mitigation efficiency depended on the groove height. The total energy release rate from the tube exit is a characteristic value of the blast wave strength at the exit, and it can be used to scale the blast wave strength outside.

Characterisation of fatigue delamination growth in plain woven hybrid laminated composites subjected to Mode-I loading

Effect of similar and dissimilar crack plane interface configuration on fatigue delamination growth in plain woven hybrid composite laminates under Mode-I has been investigated. Constant displacement amplitude fatigue testing with displacement ratio of 0.1 was carried out on 3 configurations of plain woven glass/carbon epoxy composite laminates. A power law like fit between recorded delamination length and corresponding cycle was used to predict crack length for each of the cycle. Delamination growth rate,da/dN is computed by differentiating the expression of power-law like fit.The obtained crack growth rate for each of the specimens were plotted with respect to two normalised functions, G^Imax=GImax(a)/GIR(a) where GImax is maximum mode-I energy release rate and GIR(a) is the interlaminar fracture toughness resistance and ΔG^Ieff=G^Imax-G^Imin2 as crack driving parameters computed on the basis of Modified Beam Theory (MBT) and Valvo’s mode partition method (MPV) are used in Paris relation to quantify delamination propagation. It is observed that the exponent values predicted by MBT method for G^Imax is lower as compared to ΔG^Ieff. Whereas, exponent values predicted for G^Imax is higher as compared to ΔG^Ieff predicted by MPV method. The higher the exponent value, the higher is the sensitivity of the model leading to uncertainties in the crack growth prediction. Also, it is to be noted that cyclic loading effect is when both GImax and GImin is considered, the use of ΔG^Ieff as crack driving parameter to quantify delamination propagation is justified. Secondly, MBT method does not account for the mode-mixity arising due to hybrid material configuration as in the case of Local Symmetry Fatigue (LSF) and Asymmetry Fatigue (ASF) specimens. Hence, results in higher exponent as compared to MPV method. On the other side, the G^Imax and ΔG^Ieff computed on the basis of MPV method is the pure Mode-I component deduced from the total energy release rate of mode-mixity.The equations of curve fitting is very much the same for Simple Symmetry Fatigue (SSF) specimens indicating that MBT and MPV methods predict pure Mode-I behaviour for symmetric configuration for delamination growth under fatigue Mode-I loading. From the composite laminate configuration point of view, LSF specimens have higher exponents as compared to ASF and SSF specimens indicating, local symmetry configuration laminates are highly sensitive to the small uncertainties and results in unstable crack growth.Comparison of results of all hybrid composite laminates shows that the normalised functions of G^Imax and ΔG^Ieff as crack driving parameters computed on the basis of MPV method is able to capture the effect of interlayers and stacking effect on the delamination growth in hybrid plain woven composites in fatigue loading and MPV method is found to be not sensitive to G^Imax and ΔG^Ieff for displacement ratio of 0.1.

Processing of lithium aluminium silicate glass-ceramics and investigations of fracture behaviour and its correlation with the microstructural features

Lithium Aluminium Silicate (LAS) samples were fabricated through a melt casting process using Lithium carbonate, Aluminium hydroxide, Silica and other additives as raw materials. The melt was drain casted at 1300 °C in a pre-heated mould followed by annealing and ceramization at 850 °C. Ceramized samples were subjected to X-ray diffraction. The density of the samples was found to be in the range of 2.53–2.54 g/cm3. The sample was found free from bubbles and inclusions after optically polishing. Mechanical properties including hardness, flexural strength, fracture toughness and compressive strength of LAS samples were evaluated. Knoop hardness of the LAS samples was found to be 597–669 kg/mm2. LAS sample exhibited a peak flexural strength of 110–114 MPa and compressive strength of 221 MPa before fracture. Additionally, the total fracture energy release rate (Jc) of LAS samples along with R-curve and fractography were also studied. R-curve exhibited an increasing trend of Jc with respect to normalised displacement without any sign of saturation indicating the scope for optimisation of quantification of crystals fraction in the glass matrix to obtain the predominant toughening behaviour. Finally, the physico-chemical, microstructural and optical properties were measured and correlated with the mechanical properties observed. Near to theoretical density, high crystallinity and superior mechanical properties of processed LAS glass-ceramic can be used in strategic and civilian applications.

Melting of N-eicosane-based composite phase change materials for thermal energy storage application: A computational analysis in a square cavity

The present numerical study examines the thermal performance of composite n-eicosane phase change material (CPCM) with the addition of different nanoparticles such as Al2O3, Cu, Cuo, and GnP, identifying them as CPCM 1, CPCM 2, CPCM 3, and CPCM 4. This study focuses on the melting behavior of CPCMs with concentration ranges of 2, 5, 8, and 10 wt% in a square encapsulated (SE) geometry aimed at designing an energy-efficient CPCM-based thermal energy storage (TES) system for solar photovoltaic (SPV) applications. Mass fraction contours showed that heat flux at higher concentrations (8 and 10 wt%) contributed to a strong solid-liquid interface, which makes the melt front too wide at all CPCMs. Altogether, the addition of GnP in CPCM (CPCM 4) caused enhancement in thermal conductivity and buoyancy effect, leading to earlier completion of the melting than other CPCMs, irrespective of the concentrations. In addition, the 20–30 % reduction in total time with CPCM 4 over the other three CPCMs at high concentrations of 10 wt% With the influence of nanoparticles, the energy storage capacity (ESC) of CPCMs increased by about 10 %, with concentrations ranging from 2 to 10 wt%. In addition, the variation in total energy release rate between CPCM 2 and CPCM 3 was found to be less significant. However, the ESC of CPCM 4 is 8.5 %, 11 %, and 13 % higher than that of CPCM 1, CPCM 2, and CPCM 3, respectively. With the influence of the inherent thermal properties of GnP, the better thermal performance achieved by CPCM 4 confirms its suitability for SPV system designs. Study provides insights into the design of energy-efficient CPCM-based TES systems for SPV applications.

On the Interaction of Damage Evolution and Thermal Buckling in Stepped Circular Bilaminates

Abstract The behavior and evolution of stepped circular bi-laminates with edge damage are studied for structures subjected to uniform thermal load. The problem is formulated as a moving intermediate boundaries problem in the calculus of variations, where the boundary of an evolving region of damage emanating from the edge of the smaller substructure, as well as the boundary of a progressing/regressing region of sliding contact adjacent to the intact region of the composite structure are each allowed to vary along with the displacements. This yields the associated transversality conditions that define the locations of the propagating boundaries that correspond to equilibrium configurations of the evolving composite structure, as well as the equations of equilibrium and the associated interior and exterior boundary conditions. Various configurations of contact of the detached segments of the composite structure and the associated behavior are considered, and the influence and progression of contact on the overall evolution of the composite structure are assessed. Closed-form analytical solutions to the geometrically nonlinear problem are obtained, and expressions for the critical buckling load are developed. The explicit forms of the total energy release rate along the delamination front, as well as of the conditions for propagation of the contact zone boundary, are obtained from the analytical solutions and the corresponding transversality conditions. Results of numerical simulations based on the analytical solutions are presented and are seen to unveil a rich evolution process involving contact progression/recession and metamorphosis, buckling, and detachment progression during the prebuckling phase, during sling-shot buckling, and during the postbuckling phase, depending on the material properties of the sublaminates, the geometry of the sublaminates, the initial size of the damage, and the strength of the interfacial bond. Characteristic behavior of damage propagation is found to be quite robust and is seen to include stable propagation, stable followed by unstable progression, arrest, and catastrophic propagation.

An Analytical Solution of the Total Strain Energy Release Rate and Mode Partitioning of a Beam Type Delamination Specimen under High Speed Mixed-Mode Loading

In this work an analytical solution for the calculation of the total Stain Energy Release Rate and mode partitioning of beam type delamination specimen, at crack initiation, under high speed, mixed-mode loading is obtained for the first time. The analytical model is based on the dynamic response of a Mixed-Mode End Load Split type specimen subjected to loading with a constant velocity. The Timoshenko beam theory is used to model the specimen's kinematics and the mode partitioning method used is based on the Virtual Crack Closure Technique. To model the bonded region a method based on Lagrangian multipliers is utilized. The specimen is considered as a waveguide and the waves that are allowed to propagate are analytically obtained. Due to the complexity of the analytical form of the wavenumbers for the bonded region of the specimen, which makes the calculation of eigenfrequencies intractable, a series approximation method is used. The results of the proposed analytical solution are verified using a 2D Finite Element Model. The results show the dependency of the Strain Energy Release Rate and the mode mixity on the eigenfrequencies and the eigenmodes of the specimen rendering the value of the mode mixity highly inconsistent through time.

The energy release rate of crack growth in an irradiation-induced thermo-diffusion-mechanical (I-TDM) coupling system

The material cracking behavior in the reactor is generated under the irradiation effect accompanied by thermal expansion, fission product diffusion, and mechanical load. In this study, the energy release rate for crack growth under irradiation has been deduced synthetically according to the thermodynamically consistent method and numerically implemented by the finite element method (FEM). Variation in the total energy was obtained based on the principle of minimum potential energy in which the dissipative behavior can be characterized by fission energy, irreversible heat flow, and diffusion of fission products. Through calculating the variation in the total energy with respect to crack length, the energy release rate for crack propagation was analytically represented. Additionally, the total energy release rate for deflective cracks was also derived to predict the crack kinking. Furthermore, the numerical implementation of the presented model was performed by FEM and the equivalent domain integral method. Effects of irradiation on the physical fields and the energy release rate near the crack tip were investigated and analyzed in such a complex I-TDM coupling system. This study can be developed to investigate fracture problems, assess structural integrity, and evaluate material strength of irradiated materials.

Rockburst and Gas Outburst Forecasting using a Probabilistic Risk Assessment Framework in Longwall Top Coal Caving Faces

A probabilistic risk assessment framework was developed to mathematically represent the complex engineering phenomena of rock bursts and gas outbursts for a heterogeneous coal seam. An innovative object-based non-conditional simulation approach was used to distribute lithological heterogeneity present in the coal seam to respect their geological origin. The changing mining conditions during longwall top coal caving mining (LTCC) were extracted from a coupled numerical model to provide statistically sufficient data for probabilistic analysis. The complex interdependencies among abutment stress, pore pressure, the volume of total gas emission and incremental energy release rate, their stochastic variations and uncertainty were realistically implemented in the GoldSim software, and 100,000 equally likely scenarios were simulated using the Monte Carlo method to determine the probability of rock bursts and gas outbursts. The results obtained from the analysis incorporate the variability in mechanical, elastic and reservoir properties of coal due to lithological heterogeneity and result in the probability of the occurrence of rock bursts, coal and gas outbursts, and safe mining conditions. The framework realistically represents the complex mining environment, is resilient and results are reliable. The framework is generic and can be suitably modified to be used in different underground mining scenarios, overcoming the limitations of earlier empirical indices used.

Cohesive fracture measurement technique for free-hanging thin films using highly stressed superlayer

• Development of thin film cohesive fracture test method using highly stressed superlayer. • Test method does not require expensive test equipment or external fixtures or loads. • Test method uses standard fabrication processes that create representative films. • Cohesive fracture toughness of thin film silicon dioxide measured to be 8.9-14 J/m 2 . The cohesive fracture of thin films is a concern for the reliability of many devices in microelectronics, nano-electromechanical systems/micro-electromechanical systems, photovoltaics, and other applications. In microelectronics, cohesive fracture toughness has become a concern with new dielectric materials currently being used. To design against such cohesive cracking, it is necessary to experimentally measure the cohesive fracture properties of these thin films. Many of the current tests to measure the cohesive fracture toughness of thin films are based on methods developed for larger scale specimens. Here, a fixtureless method to measure the critical total energy release rate of thin films has been developed that utilizes photolithography fabrication processes and a thin film superlayer. The superlayer has a high intrinsic stress and is used to drive cohesive fracture in the test material that it is deposited on top of. This test method has been used here to measure the cohesive critical total energy release rate of a dielectric thin film of silicon dioxide with experimental samples of thicknesses ranging from ∼100 to 400 nm to be between 8.9 and 14 J/m 2 .

Mixed-mode I+II fatigue/fracture characterisation of bi-material Aluminium/CFRP bonded joints

The fatigue/fracture behaviour of bi-material Aluminium/CFRP (Carbon-Fibre Reinforced Polymer) bonded joints was addressed in this work using the modified Paris law. Five types of tests were employed to cover appropriately the entire mode I – mode II range. Data reduction schemes based on equivalent crack length concept were developed for all types of tests. Following this methodology, the compliance versus number of cycles relation becomes sufficient to perform post-processing fatigue data analysis. The coefficients of the modified Paris law for each type of test were obtained by fitting a power law to the crack growth rate versus the ratio of total strain energy release rate and its critical value. The objective was to obtain relations representative of the evolution of those coefficients as function of mode ratio. These relations were subsequently input in a cohesive zone model at the local level, i.e., at each integration point. It was verified that the compliance versus number of cycles curves and the fatigue lives predicted numerically are in agreement with the experimental values.

A mixed mode elasto-plastic damage model for prediction of failure in single lap joint

In this paper, a pressure-dependent elasto-plastic continuum damage model is derived to account for the elasto-plastic behaviour as well as the gradual damage evolution in the single lap joint (SLJ) using thermodynamic principals. The damage onset is activated by the pressure-dependent loading criterion similar to the yield condition. The total energy release rate is equal to the critical energy release rate as in CZM. This means that the proposed model belongs to a continuum damage model adapting to CZM. However, the present model is different in that it applies the actual pressure-dependent continuum elasto-plastic constitutive relation before the damage onset. Both examples (a symmetric and an asymmetric SLJ) validate that the current model depicts not only the plastic behavior but also damage evolution. An example for the asymmetric SLJ shows that the asymmetric damage evolution and asymmetric crack propagation path in the adhesive layer may be captured using the current model. User material subroutine UMAT in ABAQUS/Standard is used to implement the current model.

Determining adhesion of critical interfaces in microelectronics – A reverse Finite Element Modelling approach based on nanoindentation

State-of-the-art microelectronic devices, especially power semiconductors, are usually exposed to harsh environmental conditions on the one hand, for example large temperature hubs, and to challenging application conditions on the other hand, such as pulsed current applications. Mechanical robustness and reliability have become more and more challenging in recent years. Along with a continuous shrinkage of dimensions, thin film materials are stacked and micro-structured for optimized performance of such devices. Major risks for device reliability can result from loss of adhesion at interfaces of these stacked thin films. Therefore, it is crucial for such devices to feature perfect initial adhesion of the said thin film layers, even after exposure to thermal treatment or in presence of intrinsic stress. In order to validate device robustness, the quality of interface adhesion between isolating and metallization layers should be carefully assessed. A particular focus is set on interfaces between the following, widely employed materials: Cu, Al, WTi, BPSG, SiN etc. Robustness by design at critical interfaces has relied more and more on advanced Finite Element Modelling (FEM) methods in recent years. This includes explicit modelling of adhesion and delamination. Accurate parameters that describe interfacial adhesion – critical adhesion energies in tensile and shear mode – need to be extracted by means of suitable experiments on tailored test vehicles. FEM is able in turn to verify the existing theoretical framework about extracting adhesion energies from experiments, given that the analytical models are often phenomenological and based on simplified assumptions. Experimentally, Nanoindentation on designed multi-layer thin film stacks has proven to be a suitable method to investigate inter-layer adhesion strength on test vehicle basis. We focused on layered stacks of tungsten‑titanium (WTi) and Boron-Phosphorous-Silicate Glass (BPSG) on Silicon substrates. The WTi layer exhibits compressive stress tailored by means of deposition. When an axis-symmetric conical or spherical indenter penetrates the WTi film, buckles around the indenter imprint arise upon loading and may propagate during unloading. Buckle geometry is measured by means of focused ion beam and Scanning Electron Microscopy. Afterwards the critical adhesion energies can be determined by existing analytical models. Combining experimental and simulation methods one may follow a Physics-of-Failure approach and assess the failure mechanisms related to thin film delamination and interface fracture. With experimental results on hand, we implemented an FE model of the same multi-layer system. Initiation and propagation of delamination was modeled by means of a Cohesive Zone Model (CZM) based on a cohesive surface contact approach. The model incorporates elastic-plastic deformation as well as intrinsic stresses of all layers, including the substrate. Following an inverse FEM approach, we reproduced the size of the delaminated area and load-displacement curves of the indenter by recursively readjusting Cohesive Zone parameters. The so-obtained adhesion parameters and modelling can be used elsewhere in delamination risk assessments of industrial semiconductor applications. This approach also gives insight into the accuracy of the formulae used for calculating the total energy release rate and extracting the further relevant parameters without the need to rely on phenomenological assumptions.

Extension of the virtual crack closure technique to cracked homogeneous bodies undergoing large deformations

In this work, energy release rates evaluated by means of the virtual crack closure technique (VCCT) are analyzed for structures undergoing large deformations. For this, nonlinear finite element (FE) analyses are carried out on edge notched and pure shear specimens in Abaqus. Two hyperelastic constitutive material models: incompressible Mooney–Rivlin (I-MR) and incompressible Ogden (I-Ogden) were used. For the nonlinear elastic analyses, the relationship between the force and displacement at a node may not be linear. Hence, the nodal point forces need to be integrated over the corresponding displacements to evaluate the energy release rates. The need for transforming the nodal point forces and displacements into a local nodal coordinate system to determine the energy release rates and mode mixity is examined. The relation between the total energy release rates GT evaluated from the nodal point forces and displacements in the global and local nodal coordinate system is derived analytically and analyzed numerically. Finally, GT evaluated by VCCT for the pure shear and edge notched specimens are compared to the J-integral.

On the delamination of polyvinyl butyral laminated glass: Identification of fracture properties from numerical modelling

This work investigates the delamination behaviour of polyvinyl butyral (PVB) laminated glass under quasi-static loading based on a cohesive zone model (CZM) with an isotropic bilinear traction - separation (T – δ) law. It presents a 2D model of a through-cracked tensile (TCT) test within an implicit finite element framework of the commercial software ANSYS. Test results from literature are used to calibrate the adhesion properties of the PVB-glass interface in a numerical cohesive zone approach. The previous TCT tests were performed at a loading rate of 6 mm/min and a temperature of approx. 22 °C. Three different PVB adhesion grades, i.e., BG R10 (low), BG R15 (medium) and BG R20 (high) are considered. Given the uncertainty in the identification of adhesion parameters, including interfacial fracture energy, cohesive strength and stiffness, a parametric analysis is conducted quantifying the influences of model parameters on the simulation results. The study allows for decoupling of individual parameters in the calibration. Then, interfacial fracture energies and cohesive strengths of the PVB-laminated glass are calibrated by matching the force – displacement curves of the numerical simulations with those from the TCT experiments. One representative case was chosen for each adhesion grade. We obtain interfacial fracture energies of 425 J/m2, 650 J/m2 and 1000 J/m2 for BG R10, BG R15 and BG R20 PVBs, respectively, while the corresponding cohesive strengths are 3 MPa, 5 MPa and 10 MPa, respectively. Moreover, based on numerical simulation results, the conversion of energy during the delamination process is extracted and discussed. The mixed-mode delamination mechanism is investigated by calculating the mode I and mode II energy release rates with respect to different PVB thicknesses and adhesion. The results show that the proportion of the mode I energy release rate is around 30%∼40% of the total energy release rate at the stable delamination stage and increases with PVB thickness. The presented study contributes to the adhesion properties of various types of PVB interlayers reported in open literatures and proposes a methodology for the unique identification of adhesion properties.

Investigating the Role of Energy Density in Thermal Runaway of Lithium-Ion Batteries with Accelerating Rate Calorimetry

This work uses accelerating rate calorimetry to evaluate the impact of cell chemistry, state of charge, cell capacity, and ultimately cell energy density on the total energy release and peak heating rates observed during thermal runaway of Li-ion batteries. While the traditional focus has been using calorimetry to compare different chemistries in cells of similar sizes, this work seeks to better understand how applicable small cell data is to understand the thermal runaway behavior of large cells as well as determine if thermal runaway behaviors can be more generally tied to aspects of lithium-ion cells such as total stored energy and specific energy. We have found a strong linear correlation between the total enthalpy of the thermal runaway process and the stored energy of the cell, apparently independent of cell size and state of charge. We have also shown that peak heating rates and peak temperatures reached during thermal runaway events are more closely tied to specific energy, increasing exponentially in the case of peak heating rates.

(Invited) Calorimetry of Cell Failure in Multiple Formats and Capacity

Accelerating Rate Calorimetry (ARC) has previously been used to evaluate differences observed in various active materials with a typical comparison shown in the figure below. This evaluation is usually performed on small cells of roughly the same capacity (~1 AH) to allow for an easy comparison of active materials as they are developed. However, this and similar calorimetry methods present a means to perform more quantitative measurements of the heat generated and kinetics of thermal runaway. Sandia National Laboratories has performed testing on cells in the 10s of amp hours and analyzed the thermal runaway behavior of these cells.This work uses accelerating rate calorimetry to evaluate the impact of cell chemistry, state of charge, cell capacity, and ultimately cell energy density on the total energy release and peak heating rates observed during thermal runaway of Li-ion batteries. This work seeks to better understand how applicable small cell data is to understand the thermal runaway behavior of large cells as well as determine if thermal runaway behaviors can be more generally tied to aspects of lithium-ion cells such as total stored energy and specific energy. We have found a strong linear correlation between the total enthalpy of the thermal runaway process and the stored energy of the cell, apparently independent of cell size and state of charge. We have also shown that peak heating rates and peak temperatures reached during thermal runaway events are more closely tied to specific energy, increasing exponentially in the case of peak heating rates.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Figure 1

R-curve behavior of adhesively bonded composite joints with highly toughened epoxy adhesive under mixed mode conditions

The fracture toughness of an adhesively bonded carbon fiber reinforced plastic joint under mixed mode (I and II) conditions was determined by means of the Fernlund–Spelt type double cantilever beam (DCB) test, where a rubber-modified epoxy adhesive was used. The R curves were determined by calculating the energy release rates, GI and GII, based on the beam theory, along with a finite element analysis. The total energy release rate GT (= GI + GII) strongly depended on the I–II mixed mode. This means that it remarkably increased with increasing mode-II component; furthermore, it varied with crack growth from GTC (at the onset of cracking) to GTS (at the steady crack-propagation region). The difference between GTC and GTS increased with the increase in the mode II component. Such R-curve characteristics were discussed based on observation of the fracture surfaces with a scanning electron microscope and the corresponding crack propagation-path behavior.

Experimental investigation to evaluate total energy release rate for unidirectional glass/epoxy composite under Mixed mode-I/II load

In this paper, the total energy release rates for unidirectional glass/epoxy composites were evaluated using Compact Tension Shear (CTS) and Four-Point Bend (FPB) Mixed mode (I/II) fracture specimens. Unidirectional glass fibre laminates were considered for the experimental work. Specimen plates of required thickness were fabricated using hand lay-up technique. The experimental study was conducted for seven loading angles varying from 0° to 90° with an increment of 15° for CTS specimen and 6 crack positions varying from 0 to 1 with an increment of 0.2 for FPB specimen. Load vs. displacement data are plotted to evaluate the peak loads for both the CTS and FPB Mixed mode (I/II) fracture specimens of various loading angles and crack positions, which are utilized to estimate the total energy release rate. It is found that the total energy release rate depends on the loading angle and crack positions for CTS and FPB Mixed mode (I/II) fracture specimens. For a particular load, the total energy release rate is highly dominating in FPB compared with the CTS fracture specimen. Hence, the FPB Mixed mode (I/II) fracture specimen can be preferred over CTS Mixed mode (I/II) fracture specimen to evaluate the total energy release rate.

Simulation of Fire in Super High-Rise Hospitals Using Fire Dynamics Simulator (FDS)

Background: Among various types of disasters, fire constitutes a significant threat to life and property in urban and rural areas. Protection the hospitals against fire is very important due to presence of disable persons, lack of awareness and expensive devices and equipments in the hospitals. The present study was aimed to fire simulation in the super high-rise hospital. Methods: This cross-sectional descriptive study was conducted in a super high-rise hospital (17 floor) in 2018-2019. The project was divided into two steps: 1) Preparation of 3D model of the hospital using 3D CAD Modeling Software; 2) The computational fluid dynamics (CFD) technique is used to predict the fire dynamics (smoke propagation, temperature distribution, heat release rate and total energy) in the hospital using the Fire Dynamic Simulator (FDS). Results: The fire simulation results showed that after 10 seconds from the onset of fire in the third floor of the hospital with the intensity of 1620/79 kW, the temperature, total energy and heat release rate reaches 87 °C, 5640 kW and 937 kW, respectively. According to the simulation results, after 600 seconds, the temperature, total energy and heat release rate were 610 °C, 928 kW and 933 kW, respectively, which the fire had reached to an uncontrollable stage. Conclusion: By correction of staircases and elevator shaft, the spread of fire can be controlled effectively. To improve the level of fire risk and appropriate actions during emergency situation in super high-rise hospital, required measures especially in the area of containment and extinguishment including buildings design for smoke control, fire alarm and extinguisher systems.

Mixed-mode thermo elastic delamination fracture behavior of composite skin stiffener containing interface delamination

This paper presents the thermo-elastic effect on materials having anisotropic behavior and stresses developed due to residual temperature on interlaminar delamination fracture characteristics of composite skin stiffener. For the preexisting interlaminar delaminations subjected to uniaxial loading and three-point bending of three-dimensional coupled field thermo-elastic finite element analyses have been accomplished. The individual mode of strain energy release rate along the delamination front has been evaluated by modified crack-closure integral method based on the concept of mechanics of linear elastic fracture. Qualitative comparison has been illustrated for the individual modes of energy release rate along the delamination front of skin stiffener for both the loadings. The influence of coupled field thermo-elastic material anisotropy of the constituting laminae has been reasoned for the asymmetric variation of total strain energy release rate along delamination front. This was found to be significantly higher for the case of residual thermal stresses compared to mechanical loading.