Influence of Grinding Direction on Fracture Strength of Silicon Nitride

Strakna, T. J.; Jahanmir, Said; Allor, R. L.; Kumar, Krishna Dev

doi:10.1115/1.2806815

Cited by 29 publications

(24 citation statements)

References 16 publications

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“…Different ceramics have various equations applicable to calculate their K 1c . Preparation of the samples involves polishing in order to create a reflective surface plane (this would mean that the surface has been well polished) [9,10,32,33] prior to the Vickers indentation process. There are still constraints with the Vickers indentation techniques, as reported by Gong [34], compared with the more conventional techniques applied, such as the SENB and double-torsion (DT) methods, as mentioned elsewhere [17,[35][36][37].…”

Section: Vickers Indentation Techniquementioning

confidence: 99%

Fracture Toughness of a Zirconia Engineering Ceramic and the Effects Thereon of Surface Processing with Fibre Laser Radiation

Shukla

Lawrence

2010

Proceedings of the Institution of Mechanical Engineers, Part B:

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Vickers hardness indentation tests were employed to investigate the near-surface changes in the hardness of a fibre laser-treated and an as-received ZrO 2 engineering ceramic. Indents were created using 5, 20, and 30 kg loads to obtain the hardness. Optical microscopy, white-light interferometry, and a coordinate measuring machine were then used to observe the crack lengths and crack geometry. Palmqvist and half-penny median crack profiles were found, which dictated the selection of the group of equations used herein. Computational and analytical approaches were then adapted to determine the K 1c of ZrO 2 . It was found that the best applicable equation was:1/2 (P/c 3/2 ), which was confirmed to be 42 per cent accurate in producing K 1c values within the range of 8 to 12 MPa m 1/2 for ZrO 2 . Fibre laser surface treatment reduced the surface hardness and produced smaller crack lengths in comparison with the as-received surface. The surface crack lengths, hardness, and indentation loads were found to be important, particularly the crack length, which significantly influenced the end K 1c value when K 1c ¼ 0.016 (E/H) 1/2 (P/c 3/2 ) was used. This is because, the longer the crack lengths, the lower the ceramic's resistance to indentation. This, in turn, increased the end K 1c value. Also, the hardness influences the K 1c , and a softer surface was produced by the fibre laser treatment; this resulted in higher resistance to crack propagation and enhanced the ceramic's K 1c . Increasing the indentation load also varied the end K 1c value, as higher indentation loads resulted in a bigger diamond footprint, and the ceramic exhibited longer crack lengths.

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Section: Vickers Indentation Techniquementioning

confidence: 99%

Fracture Toughness of a Zirconia Engineering Ceramic and the Effects Thereon of Surface Processing with Fibre Laser Radiation

Shukla

Lawrence

2010

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…No entanto, devido à sua alta fragilidade, os componentes invariavelmente sofrem danos, como trincas superficiais durante o processo de usinagem, resultando em perda de resistência mecânica [6,7]. Estes danos dependem do mecanismo de remoção de material, podendo ser classificados em duas categorias: modo frágil (lascamento) e modo dúctil (deformação plástica -cisalhamento).…”

Section: Introductionunclassified

Análise do acabamento superficial e força de corte no torneamento de alumina a verde

et al. 2015

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RESUMOOs esforços de corte durante o torneamento de tarugos de alumina à verde e sua correlação com aspectos superficiais da peça foram estudados em condições experimentais. A correlação entre a força de usinagem e a taxa de remoção de material é um parâmetro importante na definição do projeto de produtos cerâmicos, já que, parâmetros inadequados produzem danos superficiais inaceitáveis na peça. O presente estudo analisou os esforços de corte obtidos durante o torneamento de peças de alumina com 99,8% de pureza no seu estado verde e monitorou a influência da profundidade de corte nestes; utilizando-se ferramentas de corte de cermet sob condições constantes de usinagem. Os esforços de corte foram relacionados com os acabamentos superficiais, desgastes nas ferramentas e temperaturas das ferramentas durante a usinagem. Verificou-se que a profundidade de corte não afetou consideravelmente a qualidade das superfícies. Entretanto, ensaios preliminares para seleção das condições de corte, mostraram que velocidades de corte e avanços inadequados geram danos à superfície da peça. Assim, a melhor condição de corte foi a de maior profundidade de corte, 1,0 mm, uma vez que, com profundidades de corte menores aumenta-se o número de passes necessários para remoção do sobre material da peça, o que inevitavelmente leva a maior desgaste da ferramenta, maior força de usinagem e pior acabamento superficial. Destaca-se que a alumina em seu estado verde apresentou elevado efeito abrasivo sobre a ferramenta durante o torneamento. A sinterização da peça produzida na melhor condição de corte indicou que a qualidade do acabamento na superfície verde foi mantida. Palavra-chave: cerâmica verde, usinagem, forças de corte. ABSTRACTIn experimental conditions, cutting forces were studied during turning of green alumina billets, including their correlation with surface aspects of the workpiece. The correlation between cutting power and the removal rate are important parameters for defining the design of ceramic products, since inadequate parameters can produce excessive surface damage to the workpiece. This study examined the forces obtained during turning of alumina workpieces with 99.8% purity in their green state, by means of a three-point dynamometer, evaluating the cutting, feed and depth forces, using a cermet tool under constant machining conditions. Variables were compared with the forces, including surface finish, tool wear and temperature during machining. In the study, it was found that the depth of cut had no significant effect on the surface quality, and the cutting speed and feed influencing the finish. However, preliminary tests for selecting the cutting conditions showed that unsuitables cutting speeds and feeds generate severe damage to the workpiece surface. The best condition was 1.00 mm depth of cut, and the forces increasedfor with each pass performed, with the feed force the variable with greatest increases in relation to the cutting and depth forces, and wear of the cutting tool directly influenced the surface finish, ge...

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“…All cylindrical rods were 6.0 mm in diameter by 100 mm long and were transversely-or longitudinally ground as described below. Rods were tested on a four-point flexure fixture specifically designed for cylindrical rod specimens ( Figure 6).…”

Section: Experimental Procedures Flexural Strength Testsmentioning

confidence: 99%

“…The surface crack in flexure (SCF) and singleedged precracked beams (SEPB) methods gave values of 5.4 MPaVm ± 0.4 MPaVm and 5.6 MPaVm ± 0.2 MPaVm, respectively [41].^Chevron notch (CN) testing [42] Although these three methods produce converging results for a very broad range of crack sizes (50 fim -2 mm), there is evidence that the material does have a rising R-curve. [43,44,45] Figure 6 The four-point fixtures used for the rod flexural strength tests. Cradles on the top (arrows) and bottom apply the load evenly to the specimens on the top and bottom.…”

Section: Introductionmentioning

confidence: 99%