The mechanism governing cutting of hard materials with hybrid Laser/Waterjet system through controlled fracture

Wu, Zhuoru

doi:10.31274/etd-180810-4274

Cited by 2 publications

(2 citation statements)

References 29 publications

(8 reference statements)

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“…During laser processing materials undergo thermal expansion, it expands during heating phases and contracts during cooling/resolidi cation stages [8]. If this is in an uncontrolled manner, a phenomenon known as thermal shock occurs; this is particularly of concern with composite materials like WC [9]. If there is a signi cant difference in the expansion rates, one material will expand while the other expands to a smaller extent.…”

Section: Introductionmentioning

confidence: 99%

Understanding The Surface Integrity of Laser Surface Engineered Tungsten Carbide

Hazzan

Pacella

See

2021

Preprint

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The study investigated the effect of fibre laser processing (1060 nm, 240 ns pulse duration) on tungsten carbide (WC). Fluence, frequency, and the interaction effect of these were the most influential factors on the surface integrity and crack formation. In this paper, a crack classification system was developed, and a crack density variable was introduced to estimate the number of cracks and crack type within a 1 mm2 area size. ANOVA was used to analyse how fluence (0.05–0.20 J/cm2) and frequency (5–100 kHz) altered the crack density. The crack density increased between 0.050–0.099 J/cm2 across all frequency settings then decreased as the fluence increased to 0.20 J/cm2. Superficial cracks were present in all frequency settings but particularly with lower fluence settings. Micro-cracks were more likely to form between 0.050–0.135 J/cm2. Deep cracks did not present until 40 kHz or above 0.099 J/cm2 across the frequency settings and were situated around balling and splatter defects. The crack density was minimised at 0.149 J/cm2 fluence and 52.5 kHz. To the author’s knowledge for the first time a quantitative analysis of the crack formation mechanism for brittle materials is proposed (post laser processing). In addition, a linear model generated to predict surface roughness performed best at moderate to medium level of processing (fluences in the region of 0.050–0.099 J/cm2) with an error between 1 % to 10 %. The model failed to predict the material response as accurately at higher fluences with percentage errors between 15 % to 36 %.

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Section: Introductionmentioning

confidence: 99%

Understanding The Surface Integrity of Laser Surface Engineered Tungsten Carbide

Hazzan

Pacella

See

2021

Preprint

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“…If there is a significant difference in the expansion rates, a thermal mismatch will occur leading to micro-cracks [7]. If this occurs in an uncontrolled manner across the microstructure, this leads to thermal shock, this is particularly of concern with composite materials like WC with a cobalt binder ( [8,9]). The characteristics of cracks are also defined by their specific location within a microstructure.…”

Section: Introductionmentioning

confidence: 99%

Understanding the surface integrity of laser surface engineered tungsten carbide

Hazzan

Pacella

See

2021

Int J Adv Manuf Technol

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The study investigated the effect of fibre laser processing (1060 nm, 240-ns pulse duration) on the surface integrity of tungsten carbide (WC). The induced surface damage ranged from crack formation, porosity, balling, to spherical pores; the severity and presence of each were dependent on the laser parameters selected. The influence of fluence (0.05–0.20 J/cm2), frequency (5–100 kHz), feed speed (250–2500 mm/s) and hatch distance (0.02–0.06 mm) on 2D and 3D surface roughness were analysed using the Taguchi technique. Fluence, frequency, and the interaction effect of these were the most influential factors on the surface integrity; from this a linear model was generated to predict the surface roughness. The model performed best at moderate to medium level of processing with an error between 1 and 10 %. The model failed to predict the material response as accurately at higher fluences with percentage errors between 15 and 36 %. In this study, a crack classification system and crack density variable were introduced to estimate the number of cracks and crack type within a 1-mm2 area size. Statistical analysis of variance (ANOVA) found that fluence (63.49%) and frequency (29.38%) had a significant effect on the crack density independently but not the interaction of both. The crack density was minimised at 0.149 J/cm2 and 52.5 kHz. To the author’s knowledge, for the first time, a quantitative analysis of the crack formation mechanism for brittle materials is proposed (post laser processing).

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The mechanism governing cutting of hard materials with hybrid Laser/Waterjet system through controlled fracture

Abstract: Fracture energy calculation of spalling cracks and a possible solution to reduce spalling .

Cited by 2 publications

References 29 publications

Understanding The Surface Integrity of Laser Surface Engineered Tungsten Carbide

Understanding The Surface Integrity of Laser Surface Engineered Tungsten Carbide

Understanding the surface integrity of laser surface engineered tungsten carbide

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