Partner: T. Sadowski

Lublin University of Technology (PL)

Ostatnie publikacje
1.Postek E., Sadowski T., Cracks in Interfaces and Around Their Junctions in WC/Co Composite, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, Vol.64, No.4, pp.589-596, 2016

Streszczenie:

WC/Co ceramic metal-matrix composites are characterized by very high mechanical properties that allow for application of the composites mostly in production of different types of cutting tools. By combining in a composite structure a phase of brittle hard wolfram carbide (WC) grains with a metallic interface of cobalt (Co) that exhibits plastic properties, a geometrically complex microstructure with significantly different mechanical properties of the combined phases is created, see Fig. 1a. The presence of the elastic-plastic interface material, i.e. Co binder, in the composite structure is the reason for initiation of technological defects – mainly material porosity. During material loading pores start to coalesce and finally one can observe creation of microcracks system distributed along interfaces. The aim of the paper is to show the previously formulated model [1, 2] of the polycrystalline composite to be extended towards cracks development around the junctions of the interfaces. The obtained numerical results indicate that in the junctions high stress concentrations were observed, which leads to crack initiation and its further unstable propagation, and finally the composite failure. Results indicate that the first crack appears close to the junction and that the load carrying capacity of the sample is overestimated if a crack model in the interfaces is not assumed.

Słowa kluczowe:

metal-ceramic composite, interface elements, crack propagation at composite junctions

Afiliacje autorów:

Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
15p.
2.Postek E.W., Sadowski T., Assessing the influence of porosity in the deformation of metal-ceramic composites, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1163/092764410X554049, Vol.18, No.1, pp.57-76, 2011

Streszczenie:

The aim of the paper is to develop the previously formulated model [19, 20] of the polycrystalline composite to include porosity growth at metallic interfaces of metal-ceramic composites (MCCs). Examples of this kind of MCCs are: (1) a two-phase material composed of brittle grains WC joined by the plastic binder Co, which can contain a small degree of porosity introduced during the cooling process [31], (2) TiC-Mo2C hard phase grains surrounded by tough binder phase Ni [12]. This work focuses on the description of the deformation of the MCC material including the modelling of a real material internal structure taking into account porosity growth during the loading. Experimental observations of the WC/Co composite [10] indicate that the majority of the fracture energy of MCC is expended through ductile failure of the plastic binder Co (dimple rupture across the binder or in the binder near the binder/carbide interface). This process is preceded by porosity growth at metallic interfaces and finally leads to inter-granular cracks propagation.

This paper presents micromechanical modelling of the MCC response in the case of uniaxial tension of 3-D Representative Volume Element (RVE) with the application of the Finite Element Analysis (FEA). The MCC material includes: elastic grains and inter-granular metallic layers containing technological pores that create its real complex internal structure. The quasi-static deformation process of the material comprises elastic deformation of brittle grains, elasto-plastic deformation of inter-granular layers (of different thickness: 2-4 mu m) and additional deformation due to micro-porosity development in the layers. A micro-sample analysis leads to the conclusion that a small amount of technological porosity changes the qualitative behaviour of the MCC including deformation, rotation of grains, roughness, and level of plastic strains. (C) Koninklijke Brill NV, Leiden, 2011

Słowa kluczowe:

Interface porosity, Gurson-Tvergaard model, polycrystalline ceramic composites, INTER-GRANULAR LAYERS, POLYCRYSTALLINE CERAMICS, FRACTURE, GROWTH, PREDICTION, STRENGTH, BEHAVIOR, TENSION, CERMETS, MODEL

Afiliacje autorów:

Postek E.W.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)
25p.
3.Sadowski T., Postek E., Denis Ch., Stress distribution due to discontinuities in polycrystalline ceramics containing metallic inter-granular layers, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, Vol.39, pp.230-236, 2007
4.Sadowski T., Hardy S., Postek E., A new model for the time-dependent behaviour of polycrystalline ceramic materials with metallic inter-granular layers under tension, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, Vol.424, pp.230-238, 2006
5.Sadowski T., Hardy S.J., Postek E.W., Prediction of the mechanical response of polycrystalline ceramics containing metallic intergranular layers under uniaxial tension, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, Vol.34, pp.46-63, 2005
6.Sadowski T., Propozycja prostego modelu konstytutywnego dla polikrystalicznej ceramiki osłabionej układem pęknięć międzyziarnowych, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.36, pp.1-25, 1989

Lista rozdziałów w ostatnich monografiach
1.
526
Sadowski T., Samborski S., Mróz Z., IUTAM Symposium on Analytical and Computational Fracture Mechanics of Non-Homogeneous Materials, rozdział: Gradual Degradation of Initially Porous Polycrystalline Ceramics Subjected to Quasi-Static Tension, Springer, Dordrecht, series Solid Mechanics and its Applications, 97, pp.401-405, 2002

Prace konferencyjne
1.Sadowski T., Postek E., An influence of the elastic properties of composite components on the mechanical response of polycrystalline structures at yield level, IUTAM Symposium on Scaling in Solid Mechanics, 2007-06-25/06-29, Cardiff (GB), DOI: 10.1007/978-1-4020-9033-2_19, pp.199-208, 2009

Streszczenie:

The aim of this paper is to present a constitutive model in the case of an uniaxial tension of the polycrystalline materials including the inter-granular metallic layers, creating its internal structure. The paper is focused on the discussion of the elastic properties of a composite components influence on the overall material response. The effective continuum model was applied to get the constitutive relations. Representative Volume Element (RVE) was analysed taking into consideration an initial internal structure of the material obtained from SME photographs. Owing to a high complexity of the internal structure of the composite material, FEA technique was used to get macroscopic stress-strain correlations. They include gradual changes of the internal structure of the material due to porosity and cracks development under tension.

Słowa kluczowe:

Polycrystalline ceramics, inter-granular layers, different elastic properties of components

Afiliacje autorów:

Sadowski T.-Lublin University of Technology (PL)
Postek E.-IPPT PAN
2.Postek E., Sadowski T., Description of the Behaviour of Cellular Composite with Weak Filling Material, IUTAM Symposium on Mechanical Properties of Cellular Materials, 2007-09-17/09-20, Cachan (FR), pp.181-188, 2009
3.Postek E., Sadowski T., Denis C., Modelling of metallic inter-granular layers in polycrystalline ceramics, BMC 8, 8th International Symposium on Brittle Matrix Composites, 2005-10-23/10-25, Warszawa (PL), pp.495-506, 2006
4.Postek E., Sadowski T., Hardy S., Numerical modelling of mechanical response of a two-phase composite, IUTAM Symposium on Multiscale Modelling of Damage and Fracture Processes in Composite Materials, Lublin University of Technology, 2005-05-23/05-27, Kazimierz Dolny (PL), pp.193-200, 2006
5.Postek E.W., Hardy S.J., Sadowski T., Finite strain behaviour of a polycrystalline ceramic composite with intergranular layers, Plasticity 2006, 12th International Symposium on Plasticity and Its Current Applications, 2006-07-17/07-22, Halifax (CA), pp.205-207, 2006

Abstrakty konferencyjne
1.Postek E., Sadowski T., Impact Models of WC-Co Composite, CERMODEL 2017Modelling and Simulation Meet Innovation in Ceramics Technology, 2017-07-26/07-28, Trento (IT), pp.1, 2017
2.Postek E., Sadowski T., A Crack Model Around Junctions in WC/Co Composite, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), pp.1, 2016

Słowa kluczowe:

Metal-Ceramic Composite, Interface Elements, Crack Propagation at Composite Junctions

Afiliacje autorów:

Postek E.-IPPT PAN
Sadowski T.-Lublin University of Technology (PL)