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SINTAP – STRUCTURAL INTEGRITY ASSESSMENT PROCEDURE

Nenad Gubeljak, Faculty of Mechanical Engineering, Maribor, Slovenia

Uwe Zerbst, GKSS Research Centre, Institute of Materials Research, Geesthacht, Germany

INTRODUCTION

The SINTAP procedure is used in the interdisciplinary Brite-Euram project aimed to

examine and unify the fracture mechanics based flaw assessment and has been propose as

a procedure which should form the basis of future European standard [1]. Among many

other publications a special issue of the journal

Engineering Fracture Mechanics

67, 2000,

pp. 479-668, contains a number of papers, which describe the main features of the SINTAP

procedure. In the SINTAP procedure the implicit background assumption is that the com-

ponent is defect-free. In this case, when assumed crack or crack-like flaw affects the load

carrying capacity, the fracture mechanics principles have to be applied. Then the com-

parison between external effects and the material capacity has to be carried out on the

basis of crack tip parameters such as the linear elastic stress intensity factor,

, the

inte-

gral or the crack tip opening displacement (CTOD). As a result, the fracture behaviour of

the component can be predicted in terms of a critical applied load or a critical crack size.

Standard solutions for the crack tip parameters are available for specimens for measur-

ing the material’s resistance to fracture. As long as the deformation behaviour of the

structural component is linear elastic, the relevant parameter in the component,

, is

available in comprehensive compendia of

factor solutions [2,3,4,5]. If the component

behaves in an elastic-plastic manner the situation is much more complex because the

crack tip loading is additionally influenced by the deformation pattern of the material as

given by its stress-strain curve. This makes the generation of handbook solutions an

expensive task. To a limited extent this task has been accomplished for a few component

configurations, [6]. SINTAP procedure also includes solutions for cracked plates, bars,

and pipes of different loading configurations and crack positions. The overall structure of

SINTAP is shown in Fig. 1. For more details see Refs. [7,8]. The aim of this lecture is to

give a basic principle of SINTAP procedure, applied to a fractured forklift as an example.

1. SINTAP PROCEDURE

The SINTAP procedure is based on fracture mechanics principles, as shown in Fig. 2.

If two of the input parameters are known, the third can be determined theoretically. This

principle allows for different tasks of a fracture mechanics analysis:

•

A crack is detected in a component during service. The question to be answered is

whether this crack will lead to component failure or not. In certain circumstances the

critical state can be avoided by reducing the load.

•

In the design stage a component can be set-off with respect of a hypothetical crack, the

dimensions and position of which have to be chosen such that the crack will be detected

by non-destructive testing (NDT) in the final quality control, or in-service.

•

Vice-versa, critical crack dimensions for subsequent NDT testing can be determined.