This paper presents the results of an experimental program on precast reinforced concrete wall pa... more This paper presents the results of an experimental program on precast reinforced concrete wall panels (PRCWP). These panels were damaged under cyclic lateral loads and thereafter retrofitted or rehabilitated and retested. The experimental program was conceived to analyse the possibilities of using FRP materials for strengthening the PRCWP affected by seismic action. The fibre reinforced polymer (FRP) composites are frequently used in strengthening structural elements because of their superior characteristics and simple technology. The existing literature lacks information concerning reinforced concrete walls (RC) retrofitted by FRP composites compared to other structural members. This paper presents various effective strengthening solutions that can be applied to damaged elements. The retrofitting solutions consist in use of EBR-CFRP strips, combined EBR-CFRP strips with NSM-CFRP plates, textile reinforced mortar (TRM) using glass fibre grid, and TRM using carbon fibre grid. The solutions were proposed with the aim of restoring the wall shear resistance and to provide the confinement effect at the ends. The experimental results indicate that the performance of the elements, repaired and strengthened, were almost equal to or higher than the reference elements in terms of load bearing capacity, stiffness and energy dissipation capacity. A more ductile behaviour compared to the reference elements was recorded for the rehabilitated and retrofitted elements.
Combined Parameter and Function Estimation With Applications to Thermal Conductivity and Surface Heat Flux
HAL (Le Centre pour la Communication Scientifique Directe), 2007
This is a numerical and experimental study on the combined parameter and function estimation. The... more This is a numerical and experimental study on the combined parameter and function estimation. The determination of thermal conductivity and the surface heat flux is an illustration of combined estimation of one parameter and one function by means of the conjugate gradient method with vectorial descent parameter. The experimental example developed herein uses one set of good data obtained by Beck and Arnold (1977, Parameter Estimation in Engineering and Science, Wiley, New York). For this case, two measured temperatures in the solid are used to illustrate combined estimation. The unknown boundary condition and thermal conductivity of this solid were satisfactorily reconstructed and a good enough comparison is demonstrated between the known and estimated unknowns. The temperature data of Beck and Arnold are found to be excellent. Also, it is shown that the developed approach is general, stable, powerful, and able to process a wide variety of heat transfer problems where a simultaneous estimation is unavoidable.
Experimental Validation of an Inverse Heat Transfer Algorithm forOptimizing a Hyperthermia Treatment
HAL (Le Centre pour la Communication Scientifique Directe), 2006
Hyperthermia is a cancer treatment modality in which body tissue is exposed to elevated temperatu... more Hyperthermia is a cancer treatment modality in which body tissue is exposed to elevated temperatures to destroy cancerous cells. Hyperthermia treatment planning refers to the use of computational models to optimize the heating protocol with the goal of isolating thermal damage to predetermined treatment areas. This paper presents an algorithm to optimize a hyperthermia treatment protocol using the conjugate gradient method with the adjoint problem. The output of the minimization algorithm is a heating protocol that will cause a desired amount of thermal damage. The transient temperature distribution in a cylindrical region is simulated using the bioheat transfer equation. Temperature and time are integrated to calculate the extent of thermal damage in the region via a first-order rate process based on the Arrhenius equation. Several validation experiments are carried out by applying the results of the minimization algorithm to an albumen tissue phantom. Comparisons of metrics describing the damage region (the height and radius of the volume of thermally ablated phantom) show good agreement between the desired extent of damage and the measured extent of damage. The sensitivity of the bioheat transfer model and the Arrhenius damage model to their constituent parameters is calculated to create a tolerable range of error between the desired and measured extent of damage. The measured height and radius of the ablated region fit well within the tolerable range of error found in the sensitivity analysis.
Inverse Problems in Science and Engineering, Sep 28, 2007
This paper is concerned with the estimation of a heat source applied in the electron beam welding... more This paper is concerned with the estimation of a heat source applied in the electron beam welding process by using temperature measurements in solid phase. The aim is to identify the energy distribution which is applied in the liquid and vapor zones. This identification is realized each time in a transversal plan perpendicularly to the welding axis. For this work, the goals are, first, to analyze the feasibility of the estimation and, second, to estimate the energy distribution in a real case. The thermometallurgical model does not take into account the convective phenomena in the fused zone. Finally, the iterative regularization method is used for the two-dimensional metallurgical inverse heat transfer problem.
The diffusion coefficient (D) of gases in heavy oils is an important mass transfer parameter to m... more The diffusion coefficient (D) of gases in heavy oils is an important mass transfer parameter to model and design gas injection processes for oil recovery. The pressure-decay technique (PDT) is one of the widely used experimental methods available to infer this coefficient. PDT records the declining gas phase pressure resulting from the diffusion of gas into heavy oil inside a pressure/volume/temperature (PVT) cell. Commonly, the gas phase pressure decay is modelled by use of Fick's second law along with gas-phase mass balance equations and assuming a constant diffusion coefficient. In this work, we evaluate two concentration-dependent diffusion coefficient functions, power-law and exponential. A simple history matching technique is used to estimate the apparent diffusion coefficient (D o) and concentration dependency factor (m a) from pressure-decay data. Extensive application of our method to experimental pressure-decay tests shows that in addition to constant diffusion coefficients, both power-law and exponential functions are capable of predicting the experimental data. This implies that other experimental techniques are required to extract the functionality of diffusion coefficients with gas concentrations in heavy oil.
Heat treatment of 34CrNiMo6 steel used for mooring shackles
The International Journal of Advanced Manufacturing Technology, Jan 4, 2017
This study presents an experimental investigation of the heat treatment of 34CrNiMo6 steel used f... more This study presents an experimental investigation of the heat treatment of 34CrNiMo6 steel used for shackles. Indeed, industrial requirements impose specific mechanical properties to the materials which constitute shackles. The aim of this work is to propose a method to relate heat treatment parameters and the resulting mechanical properties. Instrumented cylindrical specimen are submitted to successive heat treatments under conditions representative of the industrial process. Core and surface temperatures are recorded during cooling. Metallographic observations and hardness measurements are performed after each heat treatment, in order to characterise the final phase distribution and mechanical properties. A model based on the one-dimensional heat conduction equation in cylindrical coordinates is developed within an implicit scheme, taking into account the temperature-dependent phase transformations. The results firstly provide a validation of the input data using specific dilatometric experiments, which then leads to a comparison between the experimental and numerical evolution of the core temperature under each cooling condition, as well as the prediction of the phase volume fractions and the resulting hardness. It is shown that the proposed approach yields a very good representation of the material properties.
HAL (Le Centre pour la Communication Scientifique Directe), May 9, 2011
-L'étude porte sur le rôle des conditions interfaciales dans le développement du noyau lors du so... more -L'étude porte sur le rôle des conditions interfaciales dans le développement du noyau lors du soudage par point. Des essais de soudage interrompus, à chaque période, sont réalisés sur des assemblages symétriques de deux tôles en acier revêtues avec des jeux d'électrodes neuves à face active rayonnée d'une part, et usagées à face active plate d'autre part. Deux modèles numériques, un pour chaque configuration d'électrode, intégrant les couplages entre les principaux phénomènes physiques dans la matière et aux interfaces sont mis au point et validés. Mots clefs-Soudage par point, tôles revêtues, simulation numérique, interface, contact électrothermo-mécanique.
Heat transfer at the casting/die interface in high pressure die casting : experimental results and contribution to modelling
HAL (Le Centre pour la Communication Scientifique Directe), May 28, 2006
The present paper deals with a new measurement method to determine the heat transfer coefficient ... more The present paper deals with a new measurement method to determine the heat transfer coefficient and the heat flux density at the interface between a casting and its die. This method and the related "Heat Transfer Gauge" were developed together as a cooperative project between CAST (Australia) and CROMeP (France). The device enables the determination of the heat transfer coefficient in an industrial casting machine. Several campaigns with High Pressure Die Casting machines and Gravity Die Casting machine have already taken place in Australia and in Europe, both in research laboratories and on commercially-run casting machines. In this paper we present results from a measurement campaign with a thoroughly instrumented HPDC die machine located at CSIRO in Melbourne. The influence of piston velocity, intensification pressure and various other process parameters on the heat transfer are studied. A model is being developed to explain the evolution of thermal resistance at the casting/die interface, before the formation of a complete air gap. Its first stages are explained here.
This paper is concerned with the estimation of a heat source applied in the electron beam welding... more This paper is concerned with the estimation of a heat source applied in the electron beam welding process by using the micrographic information (hardness, optical micrograph...) and temperature measurements in solid phase. The aim is to identify the energy distribution which is applied in the liquid and vapor zones. This identification is realized at each time in a transversal plan perpendicularly to the welding axis. For this work, the goal is to analyze the feasibility of the estimation. So we don't use noise with the theoretical measurements. At last, the iterative regularization method will be used for this two-dimensional metallurgical inverse heat transfer problem.
One-dimensional model for heat and mass transfer within a cake during a one-sided baking process ... more One-dimensional model for heat and mass transfer within a cake during a one-sided baking process is presented. Thermophysical properties from literature do not simulate temperature and mean moisture content trends close enough to experimental measurements. This makes reliable estimation of these properties extremely important. Hence, thermophysical properties are approximated as effective constant parameters using an inverse procedure. To ease parameter estimation, a coupled mathematical model is derived in nondimensional form showing up the key parameters driving the baking process. Complex step differentiation method is utilized to compute sensitivities in order to improve their precision. Optimal location and minimum number of temperature sensors are picked from D-optimality criterion. Effect of deformation is neglected in this study. Sensitivity analysis shows that the parameter derived from Darcy law representing a ratio of permeability to dynamic viscosity of gas seems to perturb the temperature and mean moisture content minutely. Weighted least square method with significant weight given to temperature measurements results in better approximation than ordinary and scaled least square objective functions. Inverse procedure is unable to estimate temperature profile with expected precision at boundary where heat flux enters above 100 • C as the model fails to address dough transformation.
ICTEA: International Conference on Thermal Engineering, Mar 15, 2017
This study deals with the estimation of thermophysical properties of concretes containing a phase... more This study deals with the estimation of thermophysical properties of concretes containing a phase change material (PCM) from a single well designed experiment. This building material is obtained by the inclusion of micro encapsulated phase change materials, up to a specific volumetric percentage, in concretes. Three thermocouples and two heat flux sensors were carefully imbedded inside a solid flat plate of PCM and then submitted to specific heating cycle. Thermal properties are obtained by the solution of an appropriate inverse heat conduction problem that's uses measured temperatures and/or heat flux taken inside the plate. Specific heat model is used to take into account the solid/liquid phase occurring inside the wall. First results, show the estimation feasibility by using temperatures or heat flux as additional information in the inverse problem. Thus thermal conductivity and specific heat of the material were estimated with a high accuracy. Preliminary computations show a good estimation of the specific heat as temperature function. The objective of this study to show that estimation of thermophysical properties in real-use conditions is better than the conventional methods such as differential scanning, thermal differential scanning, … when available measurement are of high quality, is reached.
This paper presents the results of an experimental program on precast reinforced concrete wall pa... more This paper presents the results of an experimental program on precast reinforced concrete wall panels (PRCWP). These panels were damaged under cyclic lateral loads and thereafter retrofitted or rehabilitated and retested. The experimental program was conceived to analyse the possibilities of using FRP materials for strengthening the PRCWP affected by seismic action. The fibre reinforced polymer (FRP) composites are frequently used in strengthening structural elements because of their superior characteristics and simple technology. The existing literature lacks information concerning reinforced concrete walls (RC) retrofitted by FRP composites compared to other structural members. This paper presents various effective strengthening solutions that can be applied to damaged elements. The retrofitting solutions consist in use of EBR-CFRP strips, combined EBR-CFRP strips with NSM-CFRP plates, textile reinforced mortar (TRM) using glass fibre grid, and TRM using carbon fibre grid. The solutions were proposed with the aim of restoring the wall shear resistance and to provide the confinement effect at the ends. The experimental results indicate that the performance of the elements, repaired and strengthened, were almost equal to or higher than the reference elements in terms of load bearing capacity, stiffness and energy dissipation capacity. A more ductile behaviour compared to the reference elements was recorded for the rehabilitated and retrofitted elements.
Boundary Condition Estimation of Ablating Material Using Modified Sequential Function Specification Method
Journal of Thermophysics and Heat Transfer, 2018
An inverse analysis is applied in a one-dimensional ablation problem for simultaneous estimation ... more An inverse analysis is applied in a one-dimensional ablation problem for simultaneous estimation of unknown time-dependent boundary conditions including the applied heat flux and the Biot number at the two end surfaces of the ablating material. The sequential function specification method is employed to minimize the least-square objective function. Due to the ablation process, a moving boundary is created at the heated surface. The estimated boundary conditions along with the direct equations are used to calculate the front position of the moving surface. To deal with the high nonlinearity caused by the moving boundary and to treat the ill posedness associated with deeply embedded sensors of the current inverse problem, a small number of future time steps are used as the regularizing parameters to stabilize the inverse problem. Furthermore, to fasten the solution of the inverse problem, a new adaptive overrelaxation factor is developed that increases the speed of convergence significantly. The simulated temperature measurements at specific sensor positions inside the ablating materials are used to evaluate the objective function. The accuracy of an applied inverse analysis is examined by the step and triangular boundary condition profiles containing discontinuities and sharp corners, respectively. In spite of high nonlinearity, an appropriate consistency between the estimated values and the exact ones are obtained.
This paper presents the results of an experimental program on precast reinforced concrete wall pa... more This paper presents the results of an experimental program on precast reinforced concrete wall panels (PRCWP). These panels were damaged under cyclic lateral loads and thereafter retrofitted or rehabilitated and retested. The experimental program was conceived to analyse the possibilities of using FRP materials for strengthening the PRCWP affected by seismic action. The fibre reinforced polymer (FRP) composites are frequently used in strengthening structural elements because of their superior characteristics and simple technology. The existing literature lacks information concerning reinforced concrete walls (RC) retrofitted by FRP composites compared to other structural members. This paper presents various effective strengthening solutions that can be applied to damaged elements. The retrofitting solutions consist in use of EBR-CFRP strips, combined EBR-CFRP strips with NSM-CFRP plates, textile reinforced mortar (TRM) using glass fibre grid, and TRM using carbon fibre grid. The solutions were proposed with the aim of restoring the wall shear resistance and to provide the confinement effect at the ends. The experimental results indicate that the performance of the elements, repaired and strengthened, were almost equal to or higher than the reference elements in terms of load bearing capacity, stiffness and energy dissipation capacity. A more ductile behaviour compared to the reference elements was recorded for the rehabilitated and retrofitted elements.
Combined Parameter and Function Estimation With Applications to Thermal Conductivity and Surface Heat Flux
HAL (Le Centre pour la Communication Scientifique Directe), 2007
This is a numerical and experimental study on the combined parameter and function estimation. The... more This is a numerical and experimental study on the combined parameter and function estimation. The determination of thermal conductivity and the surface heat flux is an illustration of combined estimation of one parameter and one function by means of the conjugate gradient method with vectorial descent parameter. The experimental example developed herein uses one set of good data obtained by Beck and Arnold (1977, Parameter Estimation in Engineering and Science, Wiley, New York). For this case, two measured temperatures in the solid are used to illustrate combined estimation. The unknown boundary condition and thermal conductivity of this solid were satisfactorily reconstructed and a good enough comparison is demonstrated between the known and estimated unknowns. The temperature data of Beck and Arnold are found to be excellent. Also, it is shown that the developed approach is general, stable, powerful, and able to process a wide variety of heat transfer problems where a simultaneous estimation is unavoidable.
Experimental Validation of an Inverse Heat Transfer Algorithm forOptimizing a Hyperthermia Treatment
HAL (Le Centre pour la Communication Scientifique Directe), 2006
Hyperthermia is a cancer treatment modality in which body tissue is exposed to elevated temperatu... more Hyperthermia is a cancer treatment modality in which body tissue is exposed to elevated temperatures to destroy cancerous cells. Hyperthermia treatment planning refers to the use of computational models to optimize the heating protocol with the goal of isolating thermal damage to predetermined treatment areas. This paper presents an algorithm to optimize a hyperthermia treatment protocol using the conjugate gradient method with the adjoint problem. The output of the minimization algorithm is a heating protocol that will cause a desired amount of thermal damage. The transient temperature distribution in a cylindrical region is simulated using the bioheat transfer equation. Temperature and time are integrated to calculate the extent of thermal damage in the region via a first-order rate process based on the Arrhenius equation. Several validation experiments are carried out by applying the results of the minimization algorithm to an albumen tissue phantom. Comparisons of metrics describing the damage region (the height and radius of the volume of thermally ablated phantom) show good agreement between the desired extent of damage and the measured extent of damage. The sensitivity of the bioheat transfer model and the Arrhenius damage model to their constituent parameters is calculated to create a tolerable range of error between the desired and measured extent of damage. The measured height and radius of the ablated region fit well within the tolerable range of error found in the sensitivity analysis.
Inverse Problems in Science and Engineering, Sep 28, 2007
This paper is concerned with the estimation of a heat source applied in the electron beam welding... more This paper is concerned with the estimation of a heat source applied in the electron beam welding process by using temperature measurements in solid phase. The aim is to identify the energy distribution which is applied in the liquid and vapor zones. This identification is realized each time in a transversal plan perpendicularly to the welding axis. For this work, the goals are, first, to analyze the feasibility of the estimation and, second, to estimate the energy distribution in a real case. The thermometallurgical model does not take into account the convective phenomena in the fused zone. Finally, the iterative regularization method is used for the two-dimensional metallurgical inverse heat transfer problem.
The diffusion coefficient (D) of gases in heavy oils is an important mass transfer parameter to m... more The diffusion coefficient (D) of gases in heavy oils is an important mass transfer parameter to model and design gas injection processes for oil recovery. The pressure-decay technique (PDT) is one of the widely used experimental methods available to infer this coefficient. PDT records the declining gas phase pressure resulting from the diffusion of gas into heavy oil inside a pressure/volume/temperature (PVT) cell. Commonly, the gas phase pressure decay is modelled by use of Fick's second law along with gas-phase mass balance equations and assuming a constant diffusion coefficient. In this work, we evaluate two concentration-dependent diffusion coefficient functions, power-law and exponential. A simple history matching technique is used to estimate the apparent diffusion coefficient (D o) and concentration dependency factor (m a) from pressure-decay data. Extensive application of our method to experimental pressure-decay tests shows that in addition to constant diffusion coefficients, both power-law and exponential functions are capable of predicting the experimental data. This implies that other experimental techniques are required to extract the functionality of diffusion coefficients with gas concentrations in heavy oil.
Heat treatment of 34CrNiMo6 steel used for mooring shackles
The International Journal of Advanced Manufacturing Technology, Jan 4, 2017
This study presents an experimental investigation of the heat treatment of 34CrNiMo6 steel used f... more This study presents an experimental investigation of the heat treatment of 34CrNiMo6 steel used for shackles. Indeed, industrial requirements impose specific mechanical properties to the materials which constitute shackles. The aim of this work is to propose a method to relate heat treatment parameters and the resulting mechanical properties. Instrumented cylindrical specimen are submitted to successive heat treatments under conditions representative of the industrial process. Core and surface temperatures are recorded during cooling. Metallographic observations and hardness measurements are performed after each heat treatment, in order to characterise the final phase distribution and mechanical properties. A model based on the one-dimensional heat conduction equation in cylindrical coordinates is developed within an implicit scheme, taking into account the temperature-dependent phase transformations. The results firstly provide a validation of the input data using specific dilatometric experiments, which then leads to a comparison between the experimental and numerical evolution of the core temperature under each cooling condition, as well as the prediction of the phase volume fractions and the resulting hardness. It is shown that the proposed approach yields a very good representation of the material properties.
HAL (Le Centre pour la Communication Scientifique Directe), May 9, 2011
-L'étude porte sur le rôle des conditions interfaciales dans le développement du noyau lors du so... more -L'étude porte sur le rôle des conditions interfaciales dans le développement du noyau lors du soudage par point. Des essais de soudage interrompus, à chaque période, sont réalisés sur des assemblages symétriques de deux tôles en acier revêtues avec des jeux d'électrodes neuves à face active rayonnée d'une part, et usagées à face active plate d'autre part. Deux modèles numériques, un pour chaque configuration d'électrode, intégrant les couplages entre les principaux phénomènes physiques dans la matière et aux interfaces sont mis au point et validés. Mots clefs-Soudage par point, tôles revêtues, simulation numérique, interface, contact électrothermo-mécanique.
Heat transfer at the casting/die interface in high pressure die casting : experimental results and contribution to modelling
HAL (Le Centre pour la Communication Scientifique Directe), May 28, 2006
The present paper deals with a new measurement method to determine the heat transfer coefficient ... more The present paper deals with a new measurement method to determine the heat transfer coefficient and the heat flux density at the interface between a casting and its die. This method and the related "Heat Transfer Gauge" were developed together as a cooperative project between CAST (Australia) and CROMeP (France). The device enables the determination of the heat transfer coefficient in an industrial casting machine. Several campaigns with High Pressure Die Casting machines and Gravity Die Casting machine have already taken place in Australia and in Europe, both in research laboratories and on commercially-run casting machines. In this paper we present results from a measurement campaign with a thoroughly instrumented HPDC die machine located at CSIRO in Melbourne. The influence of piston velocity, intensification pressure and various other process parameters on the heat transfer are studied. A model is being developed to explain the evolution of thermal resistance at the casting/die interface, before the formation of a complete air gap. Its first stages are explained here.
This paper is concerned with the estimation of a heat source applied in the electron beam welding... more This paper is concerned with the estimation of a heat source applied in the electron beam welding process by using the micrographic information (hardness, optical micrograph...) and temperature measurements in solid phase. The aim is to identify the energy distribution which is applied in the liquid and vapor zones. This identification is realized at each time in a transversal plan perpendicularly to the welding axis. For this work, the goal is to analyze the feasibility of the estimation. So we don't use noise with the theoretical measurements. At last, the iterative regularization method will be used for this two-dimensional metallurgical inverse heat transfer problem.
One-dimensional model for heat and mass transfer within a cake during a one-sided baking process ... more One-dimensional model for heat and mass transfer within a cake during a one-sided baking process is presented. Thermophysical properties from literature do not simulate temperature and mean moisture content trends close enough to experimental measurements. This makes reliable estimation of these properties extremely important. Hence, thermophysical properties are approximated as effective constant parameters using an inverse procedure. To ease parameter estimation, a coupled mathematical model is derived in nondimensional form showing up the key parameters driving the baking process. Complex step differentiation method is utilized to compute sensitivities in order to improve their precision. Optimal location and minimum number of temperature sensors are picked from D-optimality criterion. Effect of deformation is neglected in this study. Sensitivity analysis shows that the parameter derived from Darcy law representing a ratio of permeability to dynamic viscosity of gas seems to perturb the temperature and mean moisture content minutely. Weighted least square method with significant weight given to temperature measurements results in better approximation than ordinary and scaled least square objective functions. Inverse procedure is unable to estimate temperature profile with expected precision at boundary where heat flux enters above 100 • C as the model fails to address dough transformation.
ICTEA: International Conference on Thermal Engineering, Mar 15, 2017
This study deals with the estimation of thermophysical properties of concretes containing a phase... more This study deals with the estimation of thermophysical properties of concretes containing a phase change material (PCM) from a single well designed experiment. This building material is obtained by the inclusion of micro encapsulated phase change materials, up to a specific volumetric percentage, in concretes. Three thermocouples and two heat flux sensors were carefully imbedded inside a solid flat plate of PCM and then submitted to specific heating cycle. Thermal properties are obtained by the solution of an appropriate inverse heat conduction problem that's uses measured temperatures and/or heat flux taken inside the plate. Specific heat model is used to take into account the solid/liquid phase occurring inside the wall. First results, show the estimation feasibility by using temperatures or heat flux as additional information in the inverse problem. Thus thermal conductivity and specific heat of the material were estimated with a high accuracy. Preliminary computations show a good estimation of the specific heat as temperature function. The objective of this study to show that estimation of thermophysical properties in real-use conditions is better than the conventional methods such as differential scanning, thermal differential scanning, … when available measurement are of high quality, is reached.
This paper presents the results of an experimental program on precast reinforced concrete wall pa... more This paper presents the results of an experimental program on precast reinforced concrete wall panels (PRCWP). These panels were damaged under cyclic lateral loads and thereafter retrofitted or rehabilitated and retested. The experimental program was conceived to analyse the possibilities of using FRP materials for strengthening the PRCWP affected by seismic action. The fibre reinforced polymer (FRP) composites are frequently used in strengthening structural elements because of their superior characteristics and simple technology. The existing literature lacks information concerning reinforced concrete walls (RC) retrofitted by FRP composites compared to other structural members. This paper presents various effective strengthening solutions that can be applied to damaged elements. The retrofitting solutions consist in use of EBR-CFRP strips, combined EBR-CFRP strips with NSM-CFRP plates, textile reinforced mortar (TRM) using glass fibre grid, and TRM using carbon fibre grid. The solutions were proposed with the aim of restoring the wall shear resistance and to provide the confinement effect at the ends. The experimental results indicate that the performance of the elements, repaired and strengthened, were almost equal to or higher than the reference elements in terms of load bearing capacity, stiffness and energy dissipation capacity. A more ductile behaviour compared to the reference elements was recorded for the rehabilitated and retrofitted elements.
Boundary Condition Estimation of Ablating Material Using Modified Sequential Function Specification Method
Journal of Thermophysics and Heat Transfer, 2018
An inverse analysis is applied in a one-dimensional ablation problem for simultaneous estimation ... more An inverse analysis is applied in a one-dimensional ablation problem for simultaneous estimation of unknown time-dependent boundary conditions including the applied heat flux and the Biot number at the two end surfaces of the ablating material. The sequential function specification method is employed to minimize the least-square objective function. Due to the ablation process, a moving boundary is created at the heated surface. The estimated boundary conditions along with the direct equations are used to calculate the front position of the moving surface. To deal with the high nonlinearity caused by the moving boundary and to treat the ill posedness associated with deeply embedded sensors of the current inverse problem, a small number of future time steps are used as the regularizing parameters to stabilize the inverse problem. Furthermore, to fasten the solution of the inverse problem, a new adaptive overrelaxation factor is developed that increases the speed of convergence significantly. The simulated temperature measurements at specific sensor positions inside the ablating materials are used to evaluate the objective function. The accuracy of an applied inverse analysis is examined by the step and triangular boundary condition profiles containing discontinuities and sharp corners, respectively. In spite of high nonlinearity, an appropriate consistency between the estimated values and the exact ones are obtained.
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Papers by Tahar Loulou