Papers by Keyword: Hertzian Indentation

Abstract: The recovery resistance, energy dissipation, and other mechanical properties of cement materials are evaluated based on the Hertzian indentation method in this work. It is significant and efficient for engineering application. In results, the calculated energy dissipation of clinker is higher than that of limestone, which can partially be used to explain why the grinding of clinker consumes a lot of energy in cement industry. The recovery resistance for limestone under the peak load of 100N is almost higher than of clinker. However, in contrast to that of 200N, the recovery resistance for limestone is almost identical to that of clinker. It is indicated that the clinker exhibits better plasticity. and greater energy absorption capacity.

Abstract: Initiation and propagation of Hertz crack in glass was investigated by combining sphere indentation test and optical microscope under a transparent testing platform. Thus, the process of the crack growth in glass and the critical indentation load and contact crack radius could be determined conveniently. Indentation fatigue tests were carried out to understand the contact damage resistance, the fatigue cycle number for cracking increase with decrease of the fatigue load. This simple testing method is demonstrated convenient and available for calculating the surface local strength of glass in situ via measurements of the critical load and contact crack size.

Abstract: In this work, Hertz indentation method was proposed to investigate the hardness, local strength and cyclic contact fatigue of brittle ceramic coating at high temperatures. The testing fixture for high temperature tests is designed, which is made of SiC. A Si3N4 ball with a diameter of 5 mm is used as the indenter and the CVD SiC/SiC composite is used as testing samples. The applied loads are ranged from 300 N to 700 N and the temperatures are among of room temperature to 1100 oC. The critical load and indent size are used to calculate the Brinell hardness and local strength of CVD SiC coating at room temperature and high temperatures. The contact damage under different loading number and period are analyzed. The mechanisms for the improved local strength and contact fatigue lifetime are discussed.

Abstract: The Hertzian indentation technique has been evaluated as a possible means of assessing the surface fracture behaviour of a set of qualitatively similar liquid phase sintered polycrystalline aluminas with systematically varied composition, and a range of grain sizes. The method provides a better correlation between microstructure characteristics and surface fracture behaviour than does Vickers indentation. The fracture toughness determined from Hertzian indentations was found to be a function of grain size, irrespective of the composition of the material. The cumulative probabilities of formation of ring cracks at specific loads during indentation with a spherical indenter were determined for each material from the set of 25 measurements, and the parameters of distribution of the probability of fracture were calculated. A statistical correlation between the failure probability distribution and the size distribution of alumina grains was detected.

Abstract: In this work, the study of the contact fatigue of an alumina-based laminated composite with compressive residual stress in the surface is presented, together with monolithic alumina as a reference material. Hertzian indentation techniques were employed, which better represent the inservice actual contact loading. Different tests were performed under static and cyclic loading. The evolution of damage and the different types of fracture produced were examined, and an improvement in contact resistance of the composite, due to compressive residual stress, was highlighted. A better resistance of the laminated composite was observed for every test in comparison with the monolithic reference material.

Abstract: The contact fracture behaviors of fine-grained Ti3SiC2 and coarse-grained high purity Ti3SiC2 are examined by the Hertzian indentation and Vickers indentation technique. The Vickers hardness of bulk Ti3SiC2 is as low as 5.3~6.3 Gpa, and the Hertzian contact stress-strain curves for Ti3SiC2 deviate much from linearity, which resembles the fracture behavior of a ductile metal rather than a brittle ceramic. The contact damages by both Vickers indentation and Hertzian indentation reveal a fairly good plastic deformation nature of Ti3SiC2. Un-reacted TiCx in fine-grained Ti3SiC2 may impede the plastic deformation by slip along basal plan inside Ti3SiC2 grain, making Ti3SiC2 less plastic under loading.