Nicola Bonora

University of Cassino and Southern Latium, DiCEM - Department of Civil and Mechanical Engineering, Faculty Member

University of Cassino and Southern Latium, DiMSAT - Dep. of Mechanics, Structures,Environment, Faculty Member

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Ph.D. in Aerospace Engineering
Master with thesis in Aeronautical Engineering
Past expereriences:
Research Associate, Wayne State University, Detroit, MI, USA
Int. Researcher, Battelle Memorial Institute, Columbus, OH, USA

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Papers by Nicola Bonora

A new constitutive bulk material model to predict the uniaxial tensile nonlinear behavior of fiber metal laminates

The Journal of Strain Analysis for Engineering Design, 2017

In this investigation, a constitutive material model to predict elastic–plastic behavior of fiber... more In this investigation, a constitutive material model to predict elastic–plastic behavior of fiber metal laminates is introduced. The constants of the model can be obtained from the geometry and mechanical properties of the sublayers. This model can significantly reduce the computational efforts and central processing unit time by ignoring the contact between the fiber metal laminate layers. The ability of the model to predict plastic behavior of material makes it applicable to different metallic layers. Mechanical properties of each sublayer are obtained from tensile tests. The results of finite element analysis of the fiber metal laminate specimens using layered and bulk models revealed that the influence of glue was ignorable. The proposed model was validated by performing tensile tests on fiber metal laminate grades I and II and also on low and high metal volume fraction.

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Advanced CDM strain-based modeling for ii+iii creep under multiaxial state of stress

Constitutive response and failure modeling in ductile cast iron using damage unit cell approach

Validating Material Modelling of OFHC Copper Using Dynamic Tensile Extrusion (DTE) Test at Different Impact Velocity

Bulletin of the American Physical Society, 2015

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Failure Mode of Pipes Containing Circumferential Cracks Under Bending and Its Consequence on the Application of NSCM Criterion

Computer Technology and Applications, 2003

... steel, carrying circumferential through-wall cracks of various size under four point bending ... more

Experimental measure and model validation of COD of cracked pipes under bending

In order to apply the “Leak Before Break” (LBB) Analysis is very important to know the cracks are... more In order to apply the “Leak Before Break” (LBB) Analysis is very important to know the cracks area. Particularly for pipes under bending the area depends from crack position related to the bending plane. Considering symmetrical cracks respect to the flexural plane cannot be a conservative assumption. In this work has been carried out an experimental investigation in order to evaluate COD distribution for off-axis cracks on pipes under bending. Have been tested pipes with different thickness and different cracks lengths and orientations. COD distribution has been monitored by digital image correlation (DIC). Experimental data have been used to validate an analytical model (HCM Hodograph Cone Method) previously proposed by the authors.

Damage Development in High Purity Copper Under Varying Dynamic Conditions and Microstructural States Using Continuum Damage Mechanics

AIP Conference Proceedings, 2009

In the framework of CDM, the evolution of the plastic strain, at which damage processes initiates... more

A Novel Procedure for Measuring the Dynamic Fracture Toughness Using Direct Tension Hopkinson Bar

Volume 5: High-Pressure Technology; ASME NDE Division; Rudy Scavuzzo Student Paper Symposium, 2013

ABSTRACT

The Role of Weld Processing on the Integrity Assessment of Bimetallic Girth Welds

Volume 3: Design and Analysis, 2014

Current design standards and codes do not provide specific guidance how to perform engineering cr... more Current design standards and codes do not provide specific guidance how to perform engineering criticality assessment with bi-metallic girth weld in lined or clad pipe. Recently, Bonora et al. (Proc. ASME 2013 32 nd OMAE conf.) proposed the equivalent material method (EMM) which allows one to still use current design assessment routes. The method consists in considering instead of three materials in the weld joint, a single “equivalent” material with a flow curve defined as the interpolated lower bound of the three weld joint material flow curves. In this work, the applicability of the EMM was verified considering the effect associated to weld residual stresses. To this purpose, two flaw geometry configurations have been investigated. Particular relevance was given to the multi-pass weld process simulation. Numerical results indicate that the EMM always provides reasonable results in terms of applied J with respect to those obtained considering the effective multimaterials configuration in the weld joint.

An Investigation on Circumferentially Cracked Bar Geometry for Critical CTOD Determination

Volume 6A: Pipeline and Riser Technology, 2014

Codes and standards for oil&gas industry, as OS-DNV-F101, recommend the use of single edge cr... more Codes and standards for oil&gas industry, as OS-DNV-F101, recommend the use of single edge cracked plate in tension (SEN(T)) for the experimental determination of the material critical CTOD. For clad pipe welds, this specimen geometry is difficult to be obtained for the weld material or clad corrosion resistance alloy due to the specimen shape and minimum dimensions. Alternatively, circumferential cracked bar geometry, CCB(T) could be used. This geometry configuration can be machined when limited material quantity is available and used for both quasi-static and dynamic fracture characterization. In this paper, an extensive elastic-plastic finite element investigation has been carried out on both SEN(T) and CCB(T) geometries in order to select equivalent configurations in the JQ space. Ductile crack initiation and growth has been simulated using continuum damage mechanics model. Numerical simulation results indicate that CCB(T) with a crack depth ratio r/a=0.2 realizes constraint loss similar to that of SEN(T) with a crack depth ratio a/W=0.5. Similar crack resistance curves have been obtained for these two configurations confirming the equivalence of the selected sample geometries.

Integrity Assessment of Clad Pipe Girth Welds

Volume 6A: Pipeline and Riser Technology, 2014

Current design standards and codes do not provide specific guidance how to perform engineering cr... more Current design standards and codes do not provide specific guidance how to perform engineering criticality assessment with bi-metallic girth weld in lined or clad pipe. Recently, Bonora et al. (Proc. ASME 2013 32nd OMAE conf.) proposed the equivalent material method (EMM) which allows one still to use current design assessment routes. The method consists in considering instead of three materials in the weld joint, a single “equivalent” material with a flow curve defined as the interpolated lower bound of the three weld joint material flow curves. In this work, the applicability of the EMM was verified considering the effect associated with inner pressure loading and weld residual stresses. To this purpose, two flaw geometry configurations have been investigated. Particular relevance was given to the multi-pass weld process simulation. Numerical results indicate that the EMM always provides conservative results in terms of applied J with respect to those estimated considering the effective multi-materials configuration in the weld joint.© 2014 ASME

Simplified Approach for Fracture Integrity Assessment of Bimetallic Girth Weld Joint

Volume 2B: Structures, Safety and Reliability, 2013

Recent extensive use of Corrosion Resistance Alloy (CRA) as internal protection layer of standard... more Recent extensive use of Corrosion Resistance Alloy (CRA) as internal protection layer of standard carbon-steel pipes (clad and lined pipe) in the oil and gas industry requires an intensive use of bimetallic welds. Since some degree of defects in welds is inevitable, and in codes and standards (such as BS7910) the case of bi-metallic joint is usually not considered, some R&D’s activities are ongoing to define specific design guidance for an Engineering Critical Assessment (ECA) aimed at determining flaw acceptance criteria for fabrication of bimetallic joints. Based on the limited guidance in the literature, proposed procedures for ECA on CRA welds seem not cover the root/hot pass weld region, for which the requirement of “zero defect” became mandatory. As direct consequence, it penalizes the weld fabrication rate, particularly if “J-lay” or “S-Lay” methods are adopted. Furthermore, they are investigating on cases where weld material is overmatching the base metal or for a limited pa...

$Research paper thumbnail of High strain rate fracture behaviour of fused silica$

High strain rate fracture behaviour of fused silica

Journal of Physics: Conference Series, 2014

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Assessment of an engineering approach to the evaluation of the cod of off-centered crack in pipes under bending for LBB design

Engineering Fracture Mechanics, 2012

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Strain Based Local Approach to Cleavage Fracture

Stress triaxiality effect on void nucleation in ductile metals

Fatigue & Fracture of Engineering Materials & Structures, 2020

The stress triaxiality effect on the strain required for void nucleation by particle‐matrix debon... more The stress triaxiality effect on the strain required for void nucleation by particle‐matrix debonding has been investigated by means of micromechanical modelling. A unit‐cell model considering an elastic spherical particle embedded in an elastic‐plastic matrix was developed to the purpose. Particle‐matrix decohesion was simulated through the progressive failure of a cohesive interface. It has been shown that the parameters of matrix‐particle cohesive interface are correlated with macroscopic material properties. Here, a simple relationship for the maximum cohesive opening at interface failure as a function of material fracture toughness and yield stress has been derived. Results seem to confirm that, increasing stress triaxiality, the strain at which void nucleation is predicted to occur decreases exponentially in a similar way as for fracture strain. This result has substantial implications in modelling of ductile damage because it indicates that if the stress triaxiality is high e...

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Prediction of the formability limit using damage mechanics

Journal of physics, Jul 1, 2018

Forming limit diagrams (FLD's) are used to evaluate the workability of metal sheets. These di... more Forming limit diagrams (FLD's) are used to evaluate the workability of metal sheets. These diagrams provide the failure locus at which plastic instability occurs and localized necking develops (commonly designated as the forming limit curve - FLC), and the failure loci at the onset of fracture by tension or by in-plane shear. In this work, the possibility to predict the FLD's using damage mechanics is presented. Following the approach proposed by Lemaitre [1], the fracture forming limit (FFL) for ductile metals is theoretically derived using the extended Bonora damage model (XBDM). The XBDM is used in numerical simulation with FEM of formability tests (Nakazima and Marciniak) to demonstrate the possibility to account correctly for necking development before fracture. The proposed model prediction was validated with available experimental data for high purity copper.

Strain capacity assessment of API X65 steel using damage mechanics

Frattura ed Integrità Strutturale

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Cohesion Laws in Tensile Fracture Composite Laminates With Cracks

The effect of thermo-mechanical processing on damage model parameters in Cu 99.99%

A new constitutive bulk material model to predict the uniaxial tensile nonlinear behavior of fiber metal laminates

The Journal of Strain Analysis for Engineering Design, 2017

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Advanced CDM strain-based modeling for ii+iii creep under multiaxial state of stress

Constitutive response and failure modeling in ductile cast iron using damage unit cell approach

Validating Material Modelling of OFHC Copper Using Dynamic Tensile Extrusion (DTE) Test at Different Impact Velocity

Bulletin of the American Physical Society, 2015

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Failure Mode of Pipes Containing Circumferential Cracks Under Bending and Its Consequence on the Application of NSCM Criterion

Computer Technology and Applications, 2003

... steel, carrying circumferential through-wall cracks of various size under four point bending ... more

Experimental measure and model validation of COD of cracked pipes under bending

Damage Development in High Purity Copper Under Varying Dynamic Conditions and Microstructural States Using Continuum Damage Mechanics

AIP Conference Proceedings, 2009

In the framework of CDM, the evolution of the plastic strain, at which damage processes initiates... more

A Novel Procedure for Measuring the Dynamic Fracture Toughness Using Direct Tension Hopkinson Bar

Volume 5: High-Pressure Technology; ASME NDE Division; Rudy Scavuzzo Student Paper Symposium, 2013

ABSTRACT

The Role of Weld Processing on the Integrity Assessment of Bimetallic Girth Welds

Volume 3: Design and Analysis, 2014

An Investigation on Circumferentially Cracked Bar Geometry for Critical CTOD Determination

Volume 6A: Pipeline and Riser Technology, 2014

Integrity Assessment of Clad Pipe Girth Welds

Volume 6A: Pipeline and Riser Technology, 2014

Current design standards and codes do not provide specific guidance how to perform engineering cr... more Current design standards and codes do not provide specific guidance how to perform engineering criticality assessment with bi-metallic girth weld in lined or clad pipe. Recently, Bonora et al. (Proc. ASME 2013 32nd OMAE conf.) proposed the equivalent material method (EMM) which allows one still to use current design assessment routes. The method consists in considering instead of three materials in the weld joint, a single “equivalent” material with a flow curve defined as the interpolated lower bound of the three weld joint material flow curves. In this work, the applicability of the EMM was verified considering the effect associated with inner pressure loading and weld residual stresses. To this purpose, two flaw geometry configurations have been investigated. Particular relevance was given to the multi-pass weld process simulation. Numerical results indicate that the EMM always provides conservative results in terms of applied J with respect to those estimated considering the effective multi-materials configuration in the weld joint.© 2014 ASME