APPLICATION EXPERIENCE FOR DETERMINING THE AGEING OF IN-SERVICE NPP DETERMINING THE INSTRUMENTED INDENTATION HARDNESS TEST EVALUATION Bakirova G.M Bakirov M.B., Pakhomov S.S., Frolov I.V., Krutko Е.S.,
Introduction High pressure At the present time in the world about 450 reactor units are in operation. Most of them are very old and have already fulfilled their design life of 30 years and now is an issue of ensuring their safe operation for at least another 30 years. Radiation High temperature Environment
Destructive technology We get mechanical properties by use traditional test Damage of equipment. Necessity of expensive repair. Loss of metal from inspection area for the future. Loosing of controlled zone for next testing. E,σ T,σ B,n Parameters required for numerical stressstrain analysis 3
Non-destructive technology Hardness measurement H B =F/πDH ISO/TR 10108 D No destruction. Cheap. Easy to automate. Representative statistics. Indirect information. No universal methodology. Inappropriate for NPP equipment. σ T,σ B f( HB) 4
Standard hardness measurements Brinell Vickers Rockwell Unfortunately standard methods of hardness measurements check only one point of stress-strain level of elasto-plastic deformation. It would be much better to get series of different loading levels. It can be done by use indentation diagram. 5
The history of kinetic indentation Adolf Martens has recorded the first-ever indentation diagram (1898) This experience was fixed in the international standard ISO- 14577 Instrumented indentation test for hardness and materials parameters [2002]. On the basis of this standard we have developed method of rebuilding indentation diagram to tensile diagram. 6
In 1951 D. Tabor fixed the connection between stress-strain diagram (tensile diagram) and Meyer diagram similarity of coefficient by tensile n and penetration m n=m-2. ε = 0. 2 d D Also, it was fixed the connection between deformation and stress elastic deformation First relationships between hardness and tensile properties 1 c 3 HM fully plastic deformation P π ( d / D) = 2 = c σ y 7
RUSSIAN WAY In USSR scientists began to attend to kinetic indentation method in the seventies of XX century in scientific school of Moscow Power Engineering Institute, Chair of Process Metallurgy, teacher of Dr Bakirov, Professor Michail Markovetz. 8
Kinetic indentation methodic Well defined with FEM No procedure During indentation process material under indenter pass all stages of elasto-plastic deformation as in standard tension testing. Therefore tension diagram is coded in indentation diagram. But here is a problem: how to decode it? 9
Decode approaches 10
Neural networks Work of artificial neuron can be described by the formula : x 1 W 1 x 2 W 2 Σ s= f n W i x i b x 3 W 3 i=1 x 4 W 4 b Specific neural network output signal -this is a recursive calculation of the activation function of the weighted sum of output signals of previous layers. x i signal in i input synapsis, W i weight ofi input synapsis, b neuron bias, f activation function, s neuron input value.
Example neural network implementing the task XOR ( exclusive or ) Name X1 X2 Outp ut A1 0 0 0 B1 0 1 1 A2 1 0 1 B2 1 1 0 The numbers above the arrows show the values of the weights. As the function is activated, the unit applies the jump function with a threshold of 0.5. Name X1 X2 Target OUT1 OUT2 OUT3 A1 0 0 0 0 0 0 B1 0 1 1 1 0 1 A2 1 0 1 0 1 1 B2 1 1 0 0 0 0
Neural network approach Multilayer perceptron Specimens for learning Indentation diagrams Tension diagrams 13
Elaboration of database of test pieces Material State Steel 20 (DIN 1.0402, C22) 08kH18N10T (DIN 1.4541) 1 Initial 2 Normalization 3 Annealing 4 Quenching 5 Quenching+ tempering 1 Initial 1 2 Initial 2 2 Heat treatment + work-hardening1 3 Heat treatment + work-hardening2 4 Heat treatment + work-hardening3 - Carbon steels -Low alloy steels - Alloy steels - Corrosion-resistant steels Estimation of necessary quantity and purchase of an initial material For verification of the method, a database of results of different materials testing was elaborated 15kH2NMFA (SAE 9310 H) wire 09kHGHMTA VI 16GS DIN 1.0445 1 Quenching+ tempering, 1 2 Quenching+ tempering, 2 3 Annealing 4 weld, 1 5 weld, 2 6 weld, 3 1 Initial 2 Quenching+ tempering 3 Heat treatment + work-hardening Manufacturing of welded connection plates Electrodes UONI- 13/55 10GN2MFA 4 Weld 1 5 Weld 2 1 Initial 2 Quenching+ tempering 3 Cycling Modeling of ageing by thermal treatment with the purpose of variability of mechanical properties 4 Heat treatment + work-hardening 14
Work of Neural Network Ultimate strength F 4 F 3 F 2 F 1 Stress H 1 H 2 H 3 H 4 Yield point Strain 1. Process diagram of indentation 2. Applied to the input data into network 3. Delta calculation error for the output layer by the formula: δ i (N) = (y i (N) d i ) dy i ds 4. Calculate the change in the balance of the output layer N w (n) ij = η*δ (n) (n 1) j *y i 5. Calculate errors and changes in the balance of all the other layers
The results of network training 45 40 Yield strength Ultimate strength Number of diagrams in error range 35 30 25 20 15 10 5 0 14 12 10 8 6 4 2 0 2 4 6 8 10 12 14 Percantage of errors relative to target value Mistake is less than 10%.
Checking the operation of the neural network in the samples outside the training set Mistake is less than 10%
Universal Portable Indentation System MUBATEC HU-1 Universal device for measurement of mechanical properties. Hardness tester Mubatec-HU-1 is designed to perform instrumental indentation tests of materials according to ISO 14577-1 in micro and macro range from 10 N up to 2500 N. Patented in Germany, Russia and USA
New hardness tester MUBATEC HU-1 Hardness tester Electronic block Software Microscope Chain fastened Lab frame Magnetic fastened
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