A failure criterion based on material instability

Cold spraying is a solid-state powder deposition process with several unique characteristics, allowing production of coatings or bulk components from a wide range of materials. The process has attracted much attention from academia and industry over the past two decades.The technical interest in cold spraying is twofold: first as a coating process for applications in surface technology, and second as a solid-state additive manufacturing process, offering an alternative to selective laser melting or electron beam melting methods. Moreover, cold spraying can be used to study materials behaviour under extremely high strain rates, high pressures and high cooling rates. The cold spraying process is thus considered to be relevant for various industrial applications, as well as for fundamental studies in materials science.This article aims to provide an overview of the cold spray process, the current understanding of the deposition mechanisms, and the related models and experiments, from a materials science perspective. IntroductionCold spraying (CS) is a solid-state material deposition technique, where micron-sized particles of a powder bond to a substrate as a result of high-velocity impact and the associated severe plastic deformation. Acceleration of particles to high velocities is obtained via expansion of a pressurised and (ironically) 'hot' gas through a diverging-converging nozzle.Despite heating the process gas -which is to provide higher acceleration of the gas and also to facilitate particle deformation through thermal softening -the feedstock remains in the solid state throughout the entire process; hence the name 'cold' spraying. This is to underline the contrast to conventional thermal spraying where particles are completely or partially molten upon impact onto the substrate. Alternative terminology includes cold gas spray, micro cold spray, cold gas dynamic spray, kinetic spray, supersonic particle deposition and metal powder application (MPA), all of which refer to the same principle of solid-state powder deposition as described above. CS is used for coating and repair. It is also used for additive manufacturing (AM) at relatively high deposition rates as compared to the methods based on selective laser or electron beam melting. The main advantage of CS is that it alleviates the problems associated with high temperature processing of materials, such as oxidation and unfavourable structural changes. It is possibly the only continuous method to produce bulk components of metastable materials that are available only in the powder form, e.g. as obtained from mechanical attrition or gas atomisation. The aim of the present paper is to provide an overview of CS from a materials perspective, particularly for a broader audience in materials research, e.g. with interest in dynamic phenomena, plasticity and phase transformations. In terms of application and properties, CS is perhaps best to be compared to thermal spraying processes, as in [24,25]. In view of relevant physical phenomena, however, CS is mos...

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“…Figure 3. Schematics of stress-strain variation for a typical bulk metallic material during torsion experiment [47].…”

Section: Underlying Physics and Materials Modelsmentioning

confidence: 99%

Cold spraying – A materials perspective

et al. 2016

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“…Fressengeas and Molinari (1987) introduced a relative perturbation method for adiabatic shear instability. In a series of works, Wright and co-workers (Wright and Ockendon, 1996;Wright, 2003;Schoenfeld and Wright, 2003) developed scaling laws for adiabatic shear banding.…”

Section: Introductionmentioning

confidence: 99%

Formation of adiabatic shear band in metal matrix composites

Dai

Liu

Bai

2004

International Journal of Solids and Structures

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“…As a first step to reduce guesswork, a failure criterion by Schoenfeld and Wright (2003), based on earlier work by Wright (1992Wright ( , 1994, is implemented into CTH to eliminate two of the nucleation criteria, namely user-specified thresholds for minimum strain and strain rate for nucleation. The criterion emphasizes homogenous behavior as defined by the material's constitutive response and does not require determination of any additional parameters experimentally.…”

Section: Implementation Of Schoenfeld-wright Failure Criterion Into Cthmentioning

confidence: 99%

“…The implementation of a failure criterion recently published by Schoenfeld and Wright (2003) to replace previously user-specified plastic strain and strain rate criteria for shear band nucleation in CTH is discussed in section 3. The criterion is based on ideas developed by Wright (1992Wright ( , 1994 and uses material response and scaling laws to estimate the plastic strain at which stress collapse due to adiabatic shear should occur for rate-dependent, workhardening, thermally softening materials.…”

Section: Introductionmentioning

confidence: 99%

“…A comprehensive summary of the theory is provided by Wright (2002). Details of the development of the failure criterion will not be repeated in this report since it was provided in the aforementioned paper (Schoenfeld and Wright, 2003), where they also discussed its implementation into a Lagrangian wave propagation code EPIC, implications of the model for material failure simulations, and its employment to analyze boundary value problems dominated by shear failure. Their examples included uniaxial compression, a strong velocity discontinuity that simulates edge impact by the edge of a cutting tool or a projectile, and the fragment impact problem, which is also used as an example in this report.…”

Section: Introductionmentioning

confidence: 99%

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Implementation of Schoenfield-Wright Failure Criterion into a Three-Dimensional Adiabatic Shear Band Model in CTH

Fermen-Coker¹

2004

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A failure criterion based on material instability

Cited by 63 publications

References 28 publications

Cold spraying – A materials perspective

Cold spraying – A materials perspective

Formation of adiabatic shear band in metal matrix composites

Implementation of Schoenfield-Wright Failure Criterion into a Three-Dimensional Adiabatic Shear Band Model in CTH

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