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Dimitris C Lagoudas - One of the best experts on this subject based on the ideXlab platform.
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Actuation-Induced Stable Crack Growth in near-equiatomic nickel-titanium shape memory alloys: Experimental and numerical analysis
International Journal of Solids and Structures, 2020Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C Lagoudas, Behrouz Haghgouyan, C. Hayrettin, B. Young, Ibrahim KaramanAbstract:Abstract Shape Memory Alloy (SMA) actuation technology requires a thorough understanding of the failure response of these alloys under loading that involves thermal variations, termed “actuation” loading. In this paper, the experimental observation of Stable Crack Growth in SMA compact tension specimens during temperature changes under constant bias loads is reported for the first time. The intrinsic damage mechanisms that promote Crack advance are those reported in literature for nominally isothermal overload fracture, i.e., cleavage assisted by ductile void Growth. Moreover, a numerical analysis is employed, and the resulting simulations are compared with the experimental data with the purpose of building confidence in the insight provided on the role of extrinsic mechanisms that further promote or impede Crack advance. It is concluded that phase transformation plays a dual role on the Crack Growth kinetics by promoting Crack Growth when occurring in a fan in front of the Crack tip and providing the toughness enhancement that results in Stable Crack Growth when left in the wake of the advancing Crack. While the latter is well known as transformation-induced toughness enhancement, the former has just been recently observed experimentally and is characteristic of SMAs subjected to actuation loading conditions.
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Experimental and numerical investigation of the Stable Crack Growth regime under pseudoelastic loading in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites XII, 2018Co-Authors: Behrouz Haghgouyan, Theocharis Baxevanis, S. Jape, C. Hayrettin, Ibrahim Karaman, Dimitris C LagoudasAbstract:A combined experimental and numerical analysis of fracture and Crack Growth in SMAs is presented. Crack extension is investigated under mode-I, isothermal, monotonic, mechanical loading in near-equiatomic nickel- titanium (NiTi) SMA compact tension (CT) specimens. Stable Crack Growth is observed and the associated J-R curve is evaluated along with the Crack initiation toughness. Finite element analysis (FEA) with an energetics based fracture toughness criterion is also carried out and Crack is assumed to extend when Crack-tip energy release rate reaches the material specific critical value. Fracture toughening behavior is observed during Crack Growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving Crack tip. A comparison between the experimental and numerical results is presented.
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On the fracture toughness and Stable Crack Growth in shape memory alloy actuators in the presence of transformation-induced plasticity
International Journal of Fracture, 2018Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:The effect of transformation-induced plasticity (TRIP) on the fracture response of polycrystalline shape memory alloys is analyzed in the prototype infinite center-Cracked plate subjected to thermal cycling under constant mechanical loading in plain strain. Finite element calculations are carried out to determine the mechanical fields and the Crack-tip energy release rate using the virtual Crack closure technique. Similar to phase transformation, TRIP is found to affect both the driving force for Crack Growth and the Crack Growth kinetics by promoting Crack advance when occurring in a fan in front of the Crack tip and providing a “shielding” effect when occurring behind that fan. Accumulation of TRIP strains over the cycles results in higher energy release rates from one cycle to another and may result in Crack Growth if the Crack-tip energy release rate reaches a material “specific” critical value after a sufficient number of cycles. During Crack advance, the shielding effect of the TRIP strains left in the wake of the growing Crack dominates and therefore TRIP is found to both promote the initiation of Crack Growth and extend the Stable Crack Growth regime.
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Stable Crack Growth During Thermal Actuation of Shape Memory Alloys
Shape Memory and Superelasticity, 2016Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in shape memory alloys subjected to thermal variations under plane strain, mode I, constant applied loading. The Crack is assumed to propagate at a critical level of the Crack-tip energy release rate which is modeled using the virtual Crack closure technique. The load level, applied at a high temperature at which the austenite phase is Stable, is assumed sufficiently low so that the resulting Crack-tip energy release rate is smaller than the critical value but sufficiently high so that the critical value is reached during cooling, initiating Crack Growth (Baxevanis and Lagoudas in Int J Fract 191:191–213, 2015 ). Stable Crack Growth is observed, mainly associated with the shielding effect of the transformed material left in the wake of the advancing Crack. Results pertaining to the near-tip mechanical fields and fracture toughness are presented and their sensitivity to phase transformation metrics and bias load levels is investigated.
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Stable Crack Growth during actuation in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites 2014, 2014Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in an in nite center-Cracked shape memory alloy plate subjected to thermal variations under plane strain mode I constant applied loading. Crack is assumed to propagate when the energy release rate reaches a material specific critical value. The virtual Crack Growth technique is employed to calculate the energy release rate, which was shown to increase an order of magnitude at constant applied loading as a result of phase transformation induced by thermal variations. 1 A fracture toughening is observed associated with the energy dissipated by the transformed material in the wake of the growing Crack and its sensitivity over key thermomechanical parameters is presented.
Sunil Saigal - One of the best experts on this subject based on the ideXlab platform.
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interfacial failures in a compressive shear strength test of glass polymer laminates
International Journal of Solids and Structures, 2000Co-Authors: P Rahulkumar, Anand Jagota, Stephen J Bennison, Sunil SaigalAbstract:Abstract A computational method for interfacial failure modeling in composite material systems using cohesive elements is developed. This method is based on phenomenological cohesive zone models implemented within an implicit finite element framework as cohesive elements. Dynamic 2D and 3D cohesive elements have been developed and are used to simulate a compressive shear strength (CSS) test. The CSS test is employed in the polymer industry to measure polymer/substrate adhesion. The computational framework is first verified against existing analytical solutions for dynamic Crack Growth in double cantilever beam specimens. The phenomenon of Stable Crack Growth followed by unStable Crack Growth observed in the CSS experiment is simulated. Various Crack Growth behaviors, obtained for different sizes of the initial pre-flaw along the interface, are studied. The phenomenon of dynamic Crack “pop-in”, consisting of dynamic Crack Growth followed by Crack arrest and Stable Crack Growth, is investigated. The influence of the cohesive zone model parameters on Crack “pop-in” as well as stability of Crack Growth are studied. A 3D dynamic simulation of a square plan form of CSS test is performed. The 3D analyses reveal the mixed-mode behavior in Crack front Growth along the interface and local “pop-through” of the Crack front near the free edge of the CSS test specimen.
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an element free galerkin formulation for Stable Crack Growth in an elastic solid
Computer Methods in Applied Mechanics and Engineering, 1998Co-Authors: Sunil SaigalAbstract:Abstract The discrete formulation for Stable Crack Growth in an elastic solid using the Element Free Galerkin (EFG) method based on the moving least-squares approximations has been established. The EFG method provides the ability to successfully model steep gradients, such as those that exist at a Crack tip, through the introduction of an additional distribution of nodal points. In this formulation, the inertia force term in the momentum equation is converted into a spatial gradient term by employing the steady state conditions. A convective domain is employed to account for the analysis domain moving at the same speed as the Crack front. A number of Stable Crack Growth problems are examined and comparisons between the numerical predictions and analytical solutions are made for the near-tip fields, the Crack opening profiles, as well as the global control parameters such as stress intensity factor K and energy release rate G .
S. Jape - One of the best experts on this subject based on the ideXlab platform.
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Actuation-Induced Stable Crack Growth in near-equiatomic nickel-titanium shape memory alloys: Experimental and numerical analysis
International Journal of Solids and Structures, 2020Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C Lagoudas, Behrouz Haghgouyan, C. Hayrettin, B. Young, Ibrahim KaramanAbstract:Abstract Shape Memory Alloy (SMA) actuation technology requires a thorough understanding of the failure response of these alloys under loading that involves thermal variations, termed “actuation” loading. In this paper, the experimental observation of Stable Crack Growth in SMA compact tension specimens during temperature changes under constant bias loads is reported for the first time. The intrinsic damage mechanisms that promote Crack advance are those reported in literature for nominally isothermal overload fracture, i.e., cleavage assisted by ductile void Growth. Moreover, a numerical analysis is employed, and the resulting simulations are compared with the experimental data with the purpose of building confidence in the insight provided on the role of extrinsic mechanisms that further promote or impede Crack advance. It is concluded that phase transformation plays a dual role on the Crack Growth kinetics by promoting Crack Growth when occurring in a fan in front of the Crack tip and providing the toughness enhancement that results in Stable Crack Growth when left in the wake of the advancing Crack. While the latter is well known as transformation-induced toughness enhancement, the former has just been recently observed experimentally and is characteristic of SMAs subjected to actuation loading conditions.
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Experimental and numerical investigation of the Stable Crack Growth regime under pseudoelastic loading in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites XII, 2018Co-Authors: Behrouz Haghgouyan, Theocharis Baxevanis, S. Jape, C. Hayrettin, Ibrahim Karaman, Dimitris C LagoudasAbstract:A combined experimental and numerical analysis of fracture and Crack Growth in SMAs is presented. Crack extension is investigated under mode-I, isothermal, monotonic, mechanical loading in near-equiatomic nickel- titanium (NiTi) SMA compact tension (CT) specimens. Stable Crack Growth is observed and the associated J-R curve is evaluated along with the Crack initiation toughness. Finite element analysis (FEA) with an energetics based fracture toughness criterion is also carried out and Crack is assumed to extend when Crack-tip energy release rate reaches the material specific critical value. Fracture toughening behavior is observed during Crack Growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving Crack tip. A comparison between the experimental and numerical results is presented.
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On the fracture toughness and Stable Crack Growth in shape memory alloy actuators in the presence of transformation-induced plasticity
International Journal of Fracture, 2018Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:The effect of transformation-induced plasticity (TRIP) on the fracture response of polycrystalline shape memory alloys is analyzed in the prototype infinite center-Cracked plate subjected to thermal cycling under constant mechanical loading in plain strain. Finite element calculations are carried out to determine the mechanical fields and the Crack-tip energy release rate using the virtual Crack closure technique. Similar to phase transformation, TRIP is found to affect both the driving force for Crack Growth and the Crack Growth kinetics by promoting Crack advance when occurring in a fan in front of the Crack tip and providing a “shielding” effect when occurring behind that fan. Accumulation of TRIP strains over the cycles results in higher energy release rates from one cycle to another and may result in Crack Growth if the Crack-tip energy release rate reaches a material “specific” critical value after a sufficient number of cycles. During Crack advance, the shielding effect of the TRIP strains left in the wake of the growing Crack dominates and therefore TRIP is found to both promote the initiation of Crack Growth and extend the Stable Crack Growth regime.
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Stable Crack Growth During Thermal Actuation of Shape Memory Alloys
Shape Memory and Superelasticity, 2016Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in shape memory alloys subjected to thermal variations under plane strain, mode I, constant applied loading. The Crack is assumed to propagate at a critical level of the Crack-tip energy release rate which is modeled using the virtual Crack closure technique. The load level, applied at a high temperature at which the austenite phase is Stable, is assumed sufficiently low so that the resulting Crack-tip energy release rate is smaller than the critical value but sufficiently high so that the critical value is reached during cooling, initiating Crack Growth (Baxevanis and Lagoudas in Int J Fract 191:191–213, 2015 ). Stable Crack Growth is observed, mainly associated with the shielding effect of the transformed material left in the wake of the advancing Crack. Results pertaining to the near-tip mechanical fields and fracture toughness are presented and their sensitivity to phase transformation metrics and bias load levels is investigated.
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Stable Crack Growth during actuation in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites 2014, 2014Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in an in nite center-Cracked shape memory alloy plate subjected to thermal variations under plane strain mode I constant applied loading. Crack is assumed to propagate when the energy release rate reaches a material specific critical value. The virtual Crack Growth technique is employed to calculate the energy release rate, which was shown to increase an order of magnitude at constant applied loading as a result of phase transformation induced by thermal variations. 1 A fracture toughening is observed associated with the energy dissipated by the transformed material in the wake of the growing Crack and its sensitivity over key thermomechanical parameters is presented.
Abdelhamid I Mourad - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on ductile Stable Crack Growth emanating from wire cut notch in aisi 4340 steel
Nuclear Engineering and Design, 2005Co-Authors: Abdelhamid I Mourad, M J Alghafri, O Abu A Zeid, S K MaitiAbstract:Abstract An experimental investigation on the Stable Crack Growth (SCG) behaviour in AISI 4340 using CT type specimen with a sharp slit (0.05 mm) under mode I and mixed modes (I and II) loading is presented. The slit was made in the specimen through wire cutting technique. Different combinations of loading angle ϕ and ratio of original Crack length to specimen width ( a 0 / W ) are examined. Data concerned with direction of initial Crack extension, load–load line displacement (L–LLD) diagrams, initiation and maximum loads, range of Stable Crack Growth, Crack tip blunting, Crack front geometry, fracture surfaces and their scanning electron micrographs are obtained. A noticeable blunting effect is observed prior to Crack initiation. Although the Crack initiates from a straight front, a considerable front tunnelling effect occurs as the Crack extends. Under mixed mode, the Crack extension takes place initially almost along a straight path, inclined with the main Crack. The loading angle and initial Crack length affect the initiation ( P i ) and maximum ( P max ) loads significantly, but the ratio between P max and P i remains almost constant. The direction of initial Stable Crack extension due to mixed mode loading is determined throughout an elastic finite element analysis. There is a good agreement between the experimental and predicted results.
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pure shear Stable Crack Growth through compact tension shear specimen in plane state of stress
Strength fracture and complexity, 2004Co-Authors: Abdelhamid I MouradAbstract:In this work the effect of assumption of plane state of stress (plane stress or plane strain) on the predictability of the experimental results observed during the in-plane shearing mode (mode II) Stable Crack Growth (SCG) through 8 mm thick compact tension shear (CTS) specimen of a workhardening aluminium alloy (D16AT) has been studied. Experimental results include load-sliding displacement diagrams, extent of SCG, fracture surface fractographs, scanning electron micrographs, Crack front geometry and variation of plastic zone in the thickness direction. The experimental observations show that the Crack extends in its own plane, the fracture surface is flat, smooth, and free of any shear lip, the Crack front geometry, which is mostly straight initially, remains so throughout the SCG. Furthermore, the plastic zone size is the same along the specimen thickness and the constraint on the plastic zone does not develop near the mid thickness. Numerical simulations based on the assumptions of plane stress and plane strain have been performed using a 2D elastic-plastic finite element scheme and the COA/COD criterion as the criterion governing the Crack Growth. Finite element results on the load sliding displacement diagrams, J-resistance curves, plastic zone sizes and variation of equivalent stress and strain along the Crack-line ahead of the Crack tip are presented. The resistance curve is a straight-line and the magnitudes of equivalent stress and strain show a tendency to increase as the Crack extension proceeds. In general, experimental observations indicate that a plane stress state prevails throughout the thickness and the predictions based on the assumption of state of plane stress are closer to the experimental observations for the examined thickness.
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criterion for mixed mode Stable Crack Growth i three point bend geometry
Engineering Fracture Mechanics, 1995Co-Authors: S K Maiti, Abdelhamid I MouradAbstract:Abstract Stable Crack Growth in mixed mode through three point bend (TPB) specimens of D16AT aluminium alloy has been studied both theoretically and experimentally. Theoretical investigations are based on an elastic-plastic finite element scheme based on the small deformation theory of incremental plasticity. The Crack edge profiles and the plastic wakes have been obtained by the replication method and the chemical etching technique respectively. The finite element results include load-displacement diagrams, plastic zones, Crack edge profiles, J integrals, etc. Comparison with experimental results has been presented in some cases. The agreement is generally good. The Crack Growth at every stage appears to be governed by the Crack opening angle (COA) criterion.
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criterion for mixed mode Stable Crack Growth ii compact tension geometry with and without stiffener
Engineering Fracture Mechanics, 1995Co-Authors: S K Maiti, Abdelhamid I MouradAbstract:Abstract Stable Crack Growth in mixed mode through doubly stiffened and unstiffened compact tension (CT) specimens of D16AT aluminium alloy has been studied theoretically and experimentally. Theoretical study is based on an elastic-plastic finite element scheme based on the small deformation theory of incremental plasticity. The plastic wakes have been obtained by the chemical etching method. The finite element results include load-displacement diagrams, plastic zones, Crack edge profiles, J integrals, etc. Comparisons with experimental results have been presented in some cases. The agreement is generally good. The Crack Growth at every stage appears to be governed by the COA criterion.
Theocharis Baxevanis - One of the best experts on this subject based on the ideXlab platform.
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Actuation-Induced Stable Crack Growth in near-equiatomic nickel-titanium shape memory alloys: Experimental and numerical analysis
International Journal of Solids and Structures, 2020Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C Lagoudas, Behrouz Haghgouyan, C. Hayrettin, B. Young, Ibrahim KaramanAbstract:Abstract Shape Memory Alloy (SMA) actuation technology requires a thorough understanding of the failure response of these alloys under loading that involves thermal variations, termed “actuation” loading. In this paper, the experimental observation of Stable Crack Growth in SMA compact tension specimens during temperature changes under constant bias loads is reported for the first time. The intrinsic damage mechanisms that promote Crack advance are those reported in literature for nominally isothermal overload fracture, i.e., cleavage assisted by ductile void Growth. Moreover, a numerical analysis is employed, and the resulting simulations are compared with the experimental data with the purpose of building confidence in the insight provided on the role of extrinsic mechanisms that further promote or impede Crack advance. It is concluded that phase transformation plays a dual role on the Crack Growth kinetics by promoting Crack Growth when occurring in a fan in front of the Crack tip and providing the toughness enhancement that results in Stable Crack Growth when left in the wake of the advancing Crack. While the latter is well known as transformation-induced toughness enhancement, the former has just been recently observed experimentally and is characteristic of SMAs subjected to actuation loading conditions.
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Experimental and numerical investigation of the Stable Crack Growth regime under pseudoelastic loading in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites XII, 2018Co-Authors: Behrouz Haghgouyan, Theocharis Baxevanis, S. Jape, C. Hayrettin, Ibrahim Karaman, Dimitris C LagoudasAbstract:A combined experimental and numerical analysis of fracture and Crack Growth in SMAs is presented. Crack extension is investigated under mode-I, isothermal, monotonic, mechanical loading in near-equiatomic nickel- titanium (NiTi) SMA compact tension (CT) specimens. Stable Crack Growth is observed and the associated J-R curve is evaluated along with the Crack initiation toughness. Finite element analysis (FEA) with an energetics based fracture toughness criterion is also carried out and Crack is assumed to extend when Crack-tip energy release rate reaches the material specific critical value. Fracture toughening behavior is observed during Crack Growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving Crack tip. A comparison between the experimental and numerical results is presented.
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On the fracture toughness and Stable Crack Growth in shape memory alloy actuators in the presence of transformation-induced plasticity
International Journal of Fracture, 2018Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:The effect of transformation-induced plasticity (TRIP) on the fracture response of polycrystalline shape memory alloys is analyzed in the prototype infinite center-Cracked plate subjected to thermal cycling under constant mechanical loading in plain strain. Finite element calculations are carried out to determine the mechanical fields and the Crack-tip energy release rate using the virtual Crack closure technique. Similar to phase transformation, TRIP is found to affect both the driving force for Crack Growth and the Crack Growth kinetics by promoting Crack advance when occurring in a fan in front of the Crack tip and providing a “shielding” effect when occurring behind that fan. Accumulation of TRIP strains over the cycles results in higher energy release rates from one cycle to another and may result in Crack Growth if the Crack-tip energy release rate reaches a material “specific” critical value after a sufficient number of cycles. During Crack advance, the shielding effect of the TRIP strains left in the wake of the growing Crack dominates and therefore TRIP is found to both promote the initiation of Crack Growth and extend the Stable Crack Growth regime.
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Stable Crack Growth During Thermal Actuation of Shape Memory Alloys
Shape Memory and Superelasticity, 2016Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in shape memory alloys subjected to thermal variations under plane strain, mode I, constant applied loading. The Crack is assumed to propagate at a critical level of the Crack-tip energy release rate which is modeled using the virtual Crack closure technique. The load level, applied at a high temperature at which the austenite phase is Stable, is assumed sufficiently low so that the resulting Crack-tip energy release rate is smaller than the critical value but sufficiently high so that the critical value is reached during cooling, initiating Crack Growth (Baxevanis and Lagoudas in Int J Fract 191:191–213, 2015 ). Stable Crack Growth is observed, mainly associated with the shielding effect of the transformed material left in the wake of the advancing Crack. Results pertaining to the near-tip mechanical fields and fracture toughness are presented and their sensitivity to phase transformation metrics and bias load levels is investigated.
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Stable Crack Growth during actuation in shape memory alloys
Behavior and Mechanics of Multifunctional Materials and Composites 2014, 2014Co-Authors: S. Jape, Theocharis Baxevanis, Dimitris C LagoudasAbstract:A finite element analysis of Crack Growth is carried out in an in nite center-Cracked shape memory alloy plate subjected to thermal variations under plane strain mode I constant applied loading. Crack is assumed to propagate when the energy release rate reaches a material specific critical value. The virtual Crack Growth technique is employed to calculate the energy release rate, which was shown to increase an order of magnitude at constant applied loading as a result of phase transformation induced by thermal variations. 1 A fracture toughening is observed associated with the energy dissipated by the transformed material in the wake of the growing Crack and its sensitivity over key thermomechanical parameters is presented.