Cold spray, which was originally introduced as a coating deposition technology, is rapidly evolving into an additive manufacturing process. The uniqueness of this technology is that, as opposed to other additive manufacturing technologies, it is a solid-state process that does not involve material melting or sintering. Therefore, cold spray additive manufacturing (CSAM) retains the original properties of the feedstock powder and avoids the typical drawbacks of high-temperature processes. Hence, CSAM is arousing great interest in both industrial and scientific communities. CSAM has the potential to become a widespread, high production rate additive manufacturing process, but its capabilities are still limited by low accuracy and lack in precise geometrical control. To recognize CSAM as an additive manufacturing technique, substantial developments are required regarding digitalization and automation. To move a step towards an effective geometrical control of the process, this thesis reports the development of a 3D simulation of the cold spray deposit profile. The basic physical principle of the model is represented by a partial differential equation which describes the deposit profile evolution, the variables of which are time and the three spatial coordinates. Substrate and deposit are represented by a STL file which dynamically evolves by changing its geometry and refining its mesh as the thickness of the deposit increases. The simulation directly works on the STL file by calculating the increment of thickness of each of its faces and applying the corresponding change in geometry to the mesh. This process unbinds the model from any coordinates system, allowing total freedom in the choice of nozzle trajectory, substrate geometry and jet particle’s distribution profile. The model is thus able to effectively simulate the effect of the main parameters relevant for the process, namely number of scanning passes, spray angle, scanning speed and spray distance. Moreover, complex conditions like superimposed tracks with different spray angles, curved substrates, shadow effect and non-Gaussian profiles can be effectively simulated. The developed model has been validated with experiments, demonstrating a high accuracy and notable potential towards digitalization of the CSAM process. CSAM has the potential to become a widespread, high production rate additive manufacturing process, but its capabilities are still limited by low accuracy and lack in precise geometrical control. To recognized CSAM as an additive manufacturing technique, substantial developments are required regarding automization and digitalization. To move a step towards an effective geometrical control of the process, this thesis reports the development of a 3D simulation of the cold spray deposit profile. Basic physical principle of the model is represented by a partial differential equation which describes the deposit profile evolution, the variables of which are time and the three spatial coordinates. Substrate and deposit are represented by a STL file which dynamically evolves by changing its geometry and refining its mesh as the thickness of the deposit increases. The simulation directly works on the STL file by calculating the increment of thickness of each of its faces and applying the corresponding change in geometry of the mesh. This process unbinds the model from any coordinates system, allowing total freedom in the choice of nozzle trajectory, substrate geometry and jet particle’s distribution profile. The model is thus able to effectively simulate the effect of all the main parameters relevant for the process, namely number of scanning passes, spray angle, scanning speed and spray distance. Also, complex conditions like curved substrates, shadow effect and non-Gaussian profiles can be effectively simulated. The developed model has been validated with experiments, showing a high accuracy and notable potential towards digitalization of the CSAM process.
Il cold spray, nato originariamente come una tecnologia per il rivestimento di materiali, si sta rapidamente evolvendo in un processo di produzione additiva. L’unicità di questa tecnologia consiste nel fatto che, al contrario di altre tecnologie di produzione additiva, è un processo allo stato solido, che non comporta la fusione o sinterizzazione del materiale. Pertanto, il processo di cold spray additive manufacturing (CSAM), mantiene le proprietà originali della polvere, evitando i tipici svantaggi dei processi ad alta temperatura. Per questo, CSAM sta suscitando grande interesse sia nella comunità industriale che in quella scientifica. CSAM ha il potenziale per diffondersi come processo di produzione additiva con un elevato tasso di produzione, ma le sue capacità sono ancora limitate dalla bassa accuratezza e dalla mancanza di un preciso controllo geometrico. Per annoverare il processo di CSAM tra le tecnologie di produzione additiva, sviluppi sostanziali sono necessari per quanto riguarda la digitalizzazione e l’automazione. Allo scopo di muovere un passo nella direzione di un efficace controllo geometrico del processo, questa tesi presenta lo sviluppo di una simulazione 3D del profilo del deposito ottenibile tramite cold spray. Il principio alla base del modello è rappresentato da un’equazione differenziale alle derivate parziali la quale descrive l’evoluzione del profilo del deposito e le cui variabili sono il tempo e le tre coordinate spaziali. Il substrato ed il deposito sono rappresentati da un file STL che evolve dinamicamente modificando la propria geometria ed infittendo la propria mesh. La simulazione opera direttamente sul file STL, calcolando l’incremento dello spessore di ogni sua faccia e la corrispondente modifica nella geometria della mesh. Questo processo slega il modello da qualsiasi sistema di riferimento, permettendo libertà assoluta nella scelta della traiettoria dell’ugello, la geometria del substrato ed il profilo di distribuzione delle particelle all’interno del jet. Il modello ha la capacità di simulare l’effetto di tutti i parametri caratterizzanti del processo, cioè numero di passate, angolo di spruzzo, velocità dell’ugello a distanza di spruzzo. Inoltre, condizioni complesse come substrati curvi, effetto ombra e profili non gaussiani possono essere efficacemente simulate. Il modello sviluppato è stato validato con risultati sperimentali, mostrando elevata accuratezza ed un considerevole potenziale per la digitalizzazione del processo di CSAM. CSAM ha il potenziale per diffondersi come processo di produzione additiva con un elevato tasso di produzione, ma le sue capacità sono ancora limitate dalla bassa accuratezza e la mancanza di un preciso controllo geometrico. Per annoverare il processo di CSAM tra le tecnologie di produzione additiva, sviluppi sostanziali sono necessari per quanto riguarda l’automatizzazione e la digitalizzazione. Allo scopo di muovere un passo nella direzione di un efficace controllo geometrico del processo, questa tesi presenta lo sviluppo di una simulazione 3D del profilo del deposito ottenibile tramite cold spray. Il principio alla base del modello è rappresentato da un’equazione differenziale alle derivate parziali la quale descrive l’evoluzione del profilo del deposito e le cui variabili sono il tempo e le tre coordinate spaziali. Il substrato ed il deposito sono rappresentati da un file STL che evolve dinamicamente modificando la propria geometria ed infittendo la propria mesh. La simulazione opera direttamente sul file STL, calcolando l’incremento dello spessore di ogni sua faccia e la corrispondente modifica nella geometria della mesh. Questo processo slega il modello da qualsiasi sistema di riferimento, permettendo libertà assoluta nella scelta della traiettoria dell’ugello, la geometria del substrato ed il profilo di distribuzione delle particelle all’interno del jet. Il modello ha la capacità di simulare l’effetto di tutti i parametri caratterizzanti del processo, cioè numero di passate, angolo di spruzzo, velocità dell’ugello a distanza di spruzzo. Inoltre, condizioni complesse come substrati curvi, effetto ombra e profili non gaussiani possono essere efficacemente simulate. Il modello sviluppato è stato validato con risultati sperimentali, mostrando elevata accuratezza ed un considerevole potenziale per la digitalizzazione del processo di CSAM.
3D simulation of cold spray deposit profile : towards digitalization of cold spray additive manufacturing
Vanerio, Daniele
2019/2020
Abstract
Cold spray, which was originally introduced as a coating deposition technology, is rapidly evolving into an additive manufacturing process. The uniqueness of this technology is that, as opposed to other additive manufacturing technologies, it is a solid-state process that does not involve material melting or sintering. Therefore, cold spray additive manufacturing (CSAM) retains the original properties of the feedstock powder and avoids the typical drawbacks of high-temperature processes. Hence, CSAM is arousing great interest in both industrial and scientific communities. CSAM has the potential to become a widespread, high production rate additive manufacturing process, but its capabilities are still limited by low accuracy and lack in precise geometrical control. To recognize CSAM as an additive manufacturing technique, substantial developments are required regarding digitalization and automation. To move a step towards an effective geometrical control of the process, this thesis reports the development of a 3D simulation of the cold spray deposit profile. The basic physical principle of the model is represented by a partial differential equation which describes the deposit profile evolution, the variables of which are time and the three spatial coordinates. Substrate and deposit are represented by a STL file which dynamically evolves by changing its geometry and refining its mesh as the thickness of the deposit increases. The simulation directly works on the STL file by calculating the increment of thickness of each of its faces and applying the corresponding change in geometry to the mesh. This process unbinds the model from any coordinates system, allowing total freedom in the choice of nozzle trajectory, substrate geometry and jet particle’s distribution profile. The model is thus able to effectively simulate the effect of the main parameters relevant for the process, namely number of scanning passes, spray angle, scanning speed and spray distance. Moreover, complex conditions like superimposed tracks with different spray angles, curved substrates, shadow effect and non-Gaussian profiles can be effectively simulated. The developed model has been validated with experiments, demonstrating a high accuracy and notable potential towards digitalization of the CSAM process. CSAM has the potential to become a widespread, high production rate additive manufacturing process, but its capabilities are still limited by low accuracy and lack in precise geometrical control. To recognized CSAM as an additive manufacturing technique, substantial developments are required regarding automization and digitalization. To move a step towards an effective geometrical control of the process, this thesis reports the development of a 3D simulation of the cold spray deposit profile. Basic physical principle of the model is represented by a partial differential equation which describes the deposit profile evolution, the variables of which are time and the three spatial coordinates. Substrate and deposit are represented by a STL file which dynamically evolves by changing its geometry and refining its mesh as the thickness of the deposit increases. The simulation directly works on the STL file by calculating the increment of thickness of each of its faces and applying the corresponding change in geometry of the mesh. This process unbinds the model from any coordinates system, allowing total freedom in the choice of nozzle trajectory, substrate geometry and jet particle’s distribution profile. The model is thus able to effectively simulate the effect of all the main parameters relevant for the process, namely number of scanning passes, spray angle, scanning speed and spray distance. Also, complex conditions like curved substrates, shadow effect and non-Gaussian profiles can be effectively simulated. The developed model has been validated with experiments, showing a high accuracy and notable potential towards digitalization of the CSAM process.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/166496