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Materials
Published in Ansel C. Ugural, Mechanical Engineering Design, 2022
Hardness testing is one of the principal methods for ascertaining the suitability of a material for its intended purpose. It is also a valuable inspection tool for maintaining uniformity of quality in heat-treated parts. Indentation hardness tests most often involve one of these three methods: Brinell, Rockwell, or Vickers [5]. The shore scleroscope hardness testing is sometimes employed as well. These nondestructive tests yield a relative numerical measure or scale of hardness, showing how well a material resists indentation.
Materials
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
Hardness testing is one of the principal methods for ascertaining the suitability of a material for its intended purpose. It is also a valuable inspection tool for maintaining uniformity of quality in heat-treated parts. Indentation hardness tests most often involve one of these three methods: Brinell, Rockwell, or Vickers [5]. The shore scleroscope hardness testing is sometimes employed as well. These nondestructive tests yield a relative numerical measure or scale of hardness, showing how well a material resists indentation.
Nanomechanical Properties of Solid Surfaces and Thin Films
Published in Bharat Bhushan, Handbook of Micro/Nano Tribology, 2020
The methods most widely used in determining the hardness of materials are (quasi) static indentation methods. Indentation hardness is essentially a measure of their plastic deformation properties and only to a secondary extent with their elastic properties. There is a large hydrostatic component of stress around the indentation, and since this plays no part in plastic flow the indentation pressure is appreciably higher than the uniaxial flow stress of the materials. For many materials, it is about three times as large, but if the material shows appreciable elasticity, the yielding of the elastic hinderland imposes less constraint on plastic flow and the factor of proportionality may be considered less than 3. Indentation hardness depends on the time of loading and on the temperature and other operating environmental conditions. In the indentation methods, a spherical, conical, or pyramidal indenter is forced into the surface of the material which forms a permanent (plastic) indentation in the surface of the material to be examined. The hardness number (GPa or kg/mm2), equivalent to the average pressure under the indenter, is calculated as the applied normal load divided by either the curved (surface) area (Brinell, Rockwell, and Vickers hardness numbers) or the projected area (Knoop and Berkovich hardness numbers) of the contact between the indenter and the material being tested, under load (Lysaght, 1949; Berkovich, 1951; Tabor, 1951, 1970; Mott, 1957; O’Neill, 1967; Westbrook and Conrad, 1973; Anonymous, 1979; Johnson, 1985; Blau and Lawn, 1986; Bhushan and Gupta, 1997).
Investigation of the adhesive contact between a diamond indenter and single-Crystal copper substrate at low temperatures
Published in The Journal of Adhesion, 2022
Qiyin Lin, Yuhan Zhang, Ting Yue, Shaoke Wan, Jun Hong
The contact stiffness values calculated by equation (8) and the indentation hardness values of the single-crystal copper calculated by equation (9) are presented in Table 3. It can be seen that the greater the residual depth , the lower the indentation hardness and the greater the contact stiffness . This shows that the contact stiffness of the material is related to the elastic energy. The contact stiffness is an index that reflects the ability of a material to resist indentation elastic deformation, and elastic energy measures the amount of energy stored by the substrate due to elastic deformation. The greater the elastic energy, the greater the degree of elastic deformation, and the lower the contact stiffness. The indentation hardness is a plastic index that reflects the ability of a material to resist local plastic deformation. From the essence of plastic deformation, the generation of dislocations and their slip are the main reasons for plastic deformation. The plastic energy represents the sum of the energy of all the distortions caused by the distortion of the lattice under the external load and the movement of the sliding system. The larger the energy, the greater the plastic deformation of the substrate, and the lower the indentation hardness of the material.
Closed-form functions of cross-scale indentation scaling relationships based on a strain gradient plasticity theory
Published in Philosophical Magazine, 2021
Zhijie Yu, Zhongya Lin, Yueguang Wei
When materials are at considerable small size-scales, the indentation hardness is dependent with the indentation depth. Therefore, the indentation hardness is taken value by its average during the indentation process from to . Figure 2 shows the influence of the chosen deformation modes on the dimensionless hardness. When (Figure 2(a)), namely , the dimensionless hardness is apparently not only related to the dimensionless modulus. When the representative stress is properly chosen (Figure 2(d)), the dimensionless hardness is uniquely determined by the ratio of the reduced modulus and representative stress in the form of .
Biopolymer composites: a review
Published in International Journal of Biobased Plastics, 2021
Basheer Aaliya, Kappat Valiyapeediyekkal Sunooj, Maximilian Lackner
The toughness and hardness properties depend upon the strength and ductility of a biopolymer composite. The ability to absorb energy and plastically deform without fracturing is regarded as toughness of a material. Whereas, the fracture toughness is the property of a material to resist fracturing by getting a crack [128]. The toughness of a biopolymer composite can be measured by impact tests, while the fracture toughness is analyzed by varied techniques like Kahn test and plane strain fracture toughness. Hardness of a biopolymer composite is its ability to resist the permanent plastic deformation when a compression force is applied [128]. It is mostly determined by Rockwell hardness tester, besides others like indentation, rebound and scratch. The usual indentation hardness scales are Vickers, Rockwell, Brinell and Shore. Several factors like stiffness, toughness, ductility, plasticity and visco-elasticity affect the hardness of a biopolymer composite [128].