Fracture behaviour of engineering stone material

Purpose Engineered stone is a material which can be described as an artificial stone. The exemplary application area is sink production. There are very few research projects about this type of material. In fact, most of them are research conducted by the manufacturing company, which are limited to the basic properties of the material. However, knowledge about fracture mechanic of this material may be crucial in terms of usage. The paper aims to discuss this issue. Design/methodology/approach Analysis of the inside structure was made using an optical microscope as well as SEM. In the paper, methods which can be used to obtain data about fracture behaviour of material are presented. Using eXtended Finite Element Method and experimental data from three-point bending of notched specimens stress intensity factors (SIFs) for I and II load modes were obtained. Finally, a comparison between the fracture initiation angle in the function of the ration of SIFs for I/II load modes and maximum tangential stress hypothesis prediction was presented. Findings Analysis of the inside structure proves that this type of material has an uneven distribution of particle size. This can follow to void and micronotches formation and, later, to the failure of the material. A method of obtaining stress intensity factors for the discussed type of material and specimens can be successfully applied to other similar material, as proposed in this work. Standard crack angle propagation criteria are not sufficient for this type of material. Originality/value There are very few research papers about this type of material. The subject of fracture mechanic is not properly discovered, despite the fact that IT is important in terms of the application area of these materials.

New Needs of Fracture Mechanic Analysis at Design and Operation Level: Status of French Nuclear Mechanical Codes

Based on ASME Boilers and Pressure Vessels Code the major fracture mechanic analysis is limited to protection of class 1 components to brittle fracture. All the Operators of future plants have to enlarge the scope of these analyses to different concepts, at design or operation stage: - brittle and ductile analysis of hypothetical large flaw - leak before break approach - break exclusion concept - incredibility of failure of high integrity components - end of fabrication acceptable defect - in-service inspection performance - acceptable standards in operation - Long Term Operation (LTO) All these requirements needs a procedure, an analysis method with material properties and criteria. After a short overview of each topic, the paper will present how RCC-M, RSE-M French Codes and ASME III and XI take care of all these new modern regulatory requirements.

Undercut tolerances in industry from a fracture mechanic perspective

Fatigue is an important damage mechanism that particularly affects welded components, since they are likely to present residual stresses, inhomogeneities and stress raisers. Assessment of cyclic load effects on welds has concerned both industries and scientist for decades; unexpected failure must be prevented and at the same time, structures must withstand design loads with minimum requirements of material. All these facts together with economic issues have lead to the creation of normative that rule designing and construction of welded components. Particularly, toe undercuts are generally found in large structures, and large scatter and disagreement exists towards their significance and effects. Documents usually limit only their depth without considering radius, width or length, and there is currently no explanation to that fact. Understanding the damaging process will also help to set less conservative tolerances, with consequent cost reduction due to less demanding inspection. The present paper deals with a fracture mechanic approach that uses the Resistance Curve concept to predict fatigue limit of welded components with undercuts. Results revealed that depth is the most influencing variable, and it can be used as the limiting parameter in design regulations. Moreover, good correlation was obtained with FAT values normally assigned to this kind of defect.

Stress Intensity Factor Handbook: Comparison of RSEM and ASME XI Codes

For fracture mechanic applications at design level or during operation the basic parameter used is the elastic stress intensity factor K. This stress intensity factor can be evaluated through different methods: formulas, influence or weight functions or direct elastic finite element analysis of the cracked structure. After a brief review of available methods to develop elastic analysis of the fracture mechanic parameter K (stress intensity factor), this paper will compare French RSE-M Appendix 5 handbook and corresponding ASME-XI draft Appendix A-3000 handbook under development for cylindrical cracked structures (pipes or vessels) in a first step. In a future step, other structures (elbows, thickness variation…) and other crack types or locations will be considered. The cross reference validations and the technical white papers will be discussed in the paper. A short overview of plasticity corrections proposed by these 2 different Codes will be presented, compared and discussed in accordance with the validation analysis available. Finally, some differences between these 2 handbooks can have important safety consequences in their practical applications, some over-conservatism have to be better understand and will be discussed in term of consequences on different practical applications, like fatigue or corrosion crack growth, or critical crack size in brittle or ductile regime of nuclear components.