Influence of anisotropy on overcoring stress determination assuming isotropy

2006 ◽  
pp. 433-440
Author(s):  
K Shin
Keyword(s):  
2018 ◽  
Vol 84 (7) ◽  
pp. 62-66
Author(s):  
K. V. Kurashkin

A method of ultrasonic control of the mechanical stresses which takes into account the heterogeneity of the material structure and does not require unloading of the structure or using reference samples is considered. The procedure is based on echo-method of measuring time of the bulk elastic wave propagation and determination of the relative values ν31 and ν32 related to the material structure and mechanical stresses. It is shown that stresses violate the linearity of the relationship observed between the parameters in the absence of the mechanical stresses in the rolled material. This effect formed a basis for developing a method of the deviator stress determination. The purpose of the study is to demonstrate the main advantages of the developed method against the known ultrasonic techniques used for evaluation of the mechanical stresses, give theoretical grounds to the effect which allows taking into account the heterogeneity of the material structure, and also to exemplify the procedure. An analytical expression is derived using bulk elastic wave velocity in an orthotropic material composed of cubic crystallites and an assumption on the existence of simple proportional relationship between the coefficients of the orientation distribution function in rolled metal. Presented results of the mathematical modeling confirm the experimentally observed linear dependence between the parameters ν31 and ν32 in the absence of mechanical stresses. The results of evaluating residual stresses in a welded steel plate are presented as an example of the applicability of the developed procedure. Data of ultrasonic technique and data of strain gage measurements are compared. The features of the described method of stress determination are marked and the applicability limits are specified.


2004 ◽  
Vol 44 (3) ◽  
pp. 262-269 ◽  
Author(s):  
Saoussen Laribi ◽  
Jean-Marie Fleureau ◽  
Jean-Louis Grossiord ◽  
Nejia Kbir-Ariguib

2009 ◽  
Vol 24 (S1) ◽  
pp. S77-S81 ◽  
Author(s):  
Thorsten Manns ◽  
André Rothkirch ◽  
Berthold Scholtes

This paper deals with the implementation of a theoretically described method to determine residual stresses in real space directly by means of small gauge volumes. For this purpose, beam limiting masks were designed, manufactured, and investigated in first experiments. Image series taken with a position sensitive CCD camera demonstrate the ability to detect interferences from gauge volumes beneath the sample surface by defined slit geometries. The experiments show that due to the highly absorbing masks the amount of detectable photons is poor, and thus long exposure times are necessary to receive suitable data. For increasing measurement depths (altering masks) a decrease in the intensity can be detected which leads to the assumption that the diffracted photons originate from deeper regions in the material. A model was developed to simulate the diffraction conditions with different mask layouts and material properties. Modeling yields consistent results with experimental data, and thus provides a basis for further improvements of the experimental setup and the realization and assessment of residual stress measurements.


2018 ◽  
Vol 165 ◽  
pp. 10003
Author(s):  
Ralf Trieglaff ◽  
Jürgen Rudolph ◽  
Martin Beckert ◽  
Daniel Friers

The European Pressure Vessel Standard EN 13445 provides in its part 3 (Design) a simplified method (Clause 17) and a detailed method for fatigue assessment (Clause 18). Clause 18 “Detailed Assessment of Fatigue Life” is under revision within the framework of the European working group CEN/TC 54/WG 53 – Design methods with the aim of reaching a significant increase in user-friendliness and a clear guideline for the application. This paper is focused on the new informative annex NA ”Instructions for structural stress oriented finite elements analyses using brick and shell elements”. As an essential amendment for the practical user, the determination of structural stress ranges for fatigue assessment of welds is further specified in this new annex. Different application methods for the determination of structural stresses are explained in connection with the requirements for finite element models and analyses. This paper will give a short overview of the proposed approaches of structural stress determination in annex NA of the revised EN 13445-3. It will present the status of the approaches based on the results of fatigue analyses according to EN 13445-3 Clause 18 for different application examples. For verification purposes, the results of the approaches proposed in EN 13445-3 are compared with the results of other pressure vessel design codes for nuclear and non-nuclear application.


Sign in / Sign up

Export Citation Format

Share Document