THE POSSIBILITY OF APPLYING Ni-Zn FERRITES AS SENSORS FOR MEASURING COMPRESSIVE STRESSES

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THE POSSIBILITY OF APPLYING Ni-Zn FERRITES AS SENSORS FOR MEASURING COMPRESSIVE

STRESSES

A. Bieńkowski

To cite this version:

A. Bieńkowski. THE POSSIBILITY OF APPLYING Ni-Zn FERRITES AS SENSORS FOR MEA- SURING COMPRESSIVE STRESSES. Journal de Physique Colloques, 1985, 46 (C6), pp.C6-433-C6- 436. �10.1051/jphyscol:1985683�. �jpa-00224945�

THE POSSIBILITY OF APPLYING Ni-Zn FERRITES AS SENSORS FOR MEASURING COMPRESSIVE STRESSES

A. Biefikowski

Center of Metrology and Measuring Systems, Warsaw Teohnieal University, Chodkiewiaza str. 8, 02-525 Warsaw, Poland

Résumé - Des senseurs pour mesurer des contraintes de compression, jusqu'à 100 MPa, ont été construits et testés. Ces senseurs étaient construits à partir de quatre sortes de ferrites Ni-Zn. Les carac- téristiques de sortie, le domaine d'utilisation et la sensibilité sont présentés.

Abstract - The sensors for measuring compressive stresses, with- in the range of stresses up to 100 MPa, have been constructed and tested. The sensors were made from four types of Ni-Zn ferrites.

The output characteristics, operational range and sensitivity of the sensors are presented.

I - INTRODUCTION

The magnetoelastic effect, known as the Villari effect, is thermodyna- mically inverse to the magnetostrictive effect. It can be observed, for instance, as changes of magnetic flux density B at a given magne- tic field H when an external mechanical stresses 6 .within the elasti- city limits,are applied.The point of an extremum in the B(s)g relation at which "bBjb&=0, is known as the Villari point. The magnet oelas tic properties of ferrites are interesting subjects for investigations to determine the possibilities of their use in the construction of measuring sensors /1,2/. The effect of the change of flux density B

in a ferrite which is magnetized "by a field from -3^ to +H^m, when an external stresses 6" are applied, can he used in the construction of magnetoelastic sensors for measuring stresses and forces. Ferrites, because of advantages such as high electric resistivity and the variety of magnetoelastic characteristics /^,4-/ make useful material for magnetoelastic sensor cores. Below, are presented some experi- mental results of inquiries into the magnetoelastic properties of Ni-Zn ferrite cores with a view to developing transducers" for measuring

compressive stresses and forces. Experiments have been carried out on different ferrite cores in order to optimise the performance of the transducer.

II - EXPERIMENTAL METHODS

Experiments have been carried out on a wound ferrite frame cores, which provides a closed magnetic circuit and enable compressive force to be applied (Pig.1). The dimensions of the ferrites cores are

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985683

C6-434 JOURNAL DE _PHYSIQUE

6 5 x 30 x 15 ^mm and t h e width of t h e wind ow i s 1 0 mm. The compressive s t r e s s e s 6 i n t h e c o r e columns has been a p p l i e d i n t h e range up t o 100 W a .

The chemical compositions, b u l k d e n s i t y , m a g n e t o s t r i c t i o n and c o e r c i v e f o r c e Hc

of f e r r i t e c o r e s under i n v e s t i g a t i o n a r e g i v e n i n t a b l e I . The i n v e s t i g a t i o n s of t h e o u t p u t c h a r a c t e r i s t i c s of s e n s o r s , w i t h t h e s i n u s o i d a l c u r r e n t s u p p l y , have been c a r r i e d out a s i n Fig. 2.

The o u t p u t v o l t a g e U from secondary win- d i n g i s dependent on t h e s t r e s s e s 6 a p p l i e d t o t h e c o r e columns. The i n v e s t i - g a t i o n s of t h e o u t p u t c h a r a c t e r i s t i c s of t h e s e n s o r s , w i t h t h e s i n u s o i d a l v o l t a g e s u p p l y , were performed a s shown in Fig. 3.

The output characteristics determine the dependence of the current I flowing

through the sensor winding as the function of stresses 6'

.

Fig.?

-

Fig.2

-

T a b l e 1. The chemical compositions of c o r e s

Fig.3

-

I11

-

Hc A ,-I 45 'lo

95 45

The o u t p u t v o l t a g e U a g a i n s t a p p l i e d s t r e s s e s c h a r a c t e r i s t i c f o r c o r e A 3 is shown i n Fig.4 and f o r c o r e A 2 i n Pig.5. The c h a r a c t e r i s t i c s of t h e c o r e A 4 and of t h e c o r e A? w i t h t h e s i n u s o i d a l v o l t a g e supply a r e . shown i n Fig .6. and i n Fig.? r e s p e c t i v e l y . From %he o u t p u t charac- t e r i s t l c s t h e s e n s l t l v i t y of s e n s o r s have been c a l c u l a t e d a c c o r d i n g t o t h e r e l a t i o n s h i p :

A U O U t 1

% F

-

gout

A 6

Magneto- s t r i c t i o n x f o r H=lOHr?

-i,3xl0-g -1 7x1 Oz6 -1 ,ax10 -4,2

%lo-6

whore

nuout -

B u l k d e n s i t y MI3 m -3 5 , 0 8 5 , 2 0 5905

>,o>

Core

A1 A 2

A 3 A4

Chemical com2osition mol 70 Fe203 N i O ZnO COO

5 0 1 8 32

-

50 18 32

-

48,5

> 0 , 3 2 8 , 5 2 0 ¹

0 20 40 60 MPa 100

6- 6-

P i g . 4

-

-

~ = f ( 6 ) of c o r e A3 U=f(6) of c o r e A2

0 10 20 30 40 50 MPa 70 0 20 40 60 Mf'a 100 P i g . 6

-

-

The o u t p u t c h a r a c t e r i s t i c s o b t a i n e d make t h e p o s s i b i l i t y of two t y p e s o f s e n s o r o p e r a t i o n ^: t h e f i r s t o f them-- i n

changes i n s t r e s s e s (below t h e V i l l a r i p o i n t z e r o t o t h t ~ v a l u e l i m i t e d by t h e assumed l i n e a r i t y c r i t e r i o n o

t h i s r a n g e

(

G o s h i f t i n g t h e working p o i n i n t o t h e r a n g e o f changes above t h e V i l l a r i p o i n t

(

.

The m e t r o l o g i c a l p r o p e r t i e s o t h e s e n s o r s b e i n g i n v e s t i g a t e d a r e g i v e n i n t a b l e 2 .

I

C6-436 JOURNAL DE PHYSIQUE

Table 2. The metrological p r o p e r t i e s of sensors unaer i n v e s t i g a t i o n

Uithin t h e range of changes 6 below t h e V i l l a r i p o i n t t h e work i s p o s s i b l e only under conditions of c u r r e n t supply, It i s i n t e r e s t i n g t h a t under such operation the sensor A2 e x h i b i t s consiclerable sen- s i t i v i t y S g

-

The i n i t i z l s t r e s s e s

Go,

c r y s t a l l i n e p r o 2 e r t i e s a s well a s upon i t s microstructure ^/4-8/.

I V

-

r

1. Experiments confirm t h e p o s s i b i l i t y of applying Ni-Zn f e r r i t e c o r e s f o r t h e c o n s t r u c t i o n of a magnetoelastic transducers f o r measuring compressive s t r e s s e s and f o r c e s .

2. The metrological p r o p e r t i e s of t h e magnetoelastic sensor and a type of t h e supply depends on t h e course of ~ ( 6 ) ~ characte- r i s t i c and t h e V i l l a r i p o i n t p o s i t i o n .

3. The value of magnetostriction constant % cannot be accepted a s t h e only c r i t e r i o n of assessment of t h e f e r r i t e f o r magneto- e l a s t i c sensor.

~i 0 rn a

A 1 A2 A3 A 4

The author wishes t o thank 1)r.J.Xulikowski f o r h i s h e l p f u l advice and d i s c u s s i o n of t h e paper and f o r preparing t h e f e r r i t e cores.

REFERENCES

voltage supply above the V i l l a r i point

111 Bierikowski,A., ACTA IMEKO (1979) 591

121 ie6kowski A . and Kulikowski, J . , Prace ITK 97 (1984) 1 0

$ i n ~ o l i s h j

-

131 Biehkowski , A . and Kulikowski,J., J.Magn.Magn.Mat.

141 Biehkowski,A. and Kulikowski, J . , J.Magn.Magn.Mat.

Eindhoven 1959

/5/ Smit, J. and Wijn, H.P.J., Ferrites, Philips Techn. Libr., /6/ Kaczkowski, Z., Electron Technology 7, 314 (1974) 19

/7/ Krupiska, S., Physik der Ferrite, ~ k g d e m i a Verlag, Prag 1973 /8/ Kaczkowski, Z., J.Magn. Magn. Mat.

41

c u r r e n t supply

%

YLa 20 20 30 5

A6

MPa 80 80 70 65 below the V i l l n r i

point

"6 1/MPa I , O ~ O I $ 2,8x10

-

0,4xl0-$

3,7X10- above t h e V i l l a r i

point

A 6

MPa 5 2 , 5 1 0

Go

MPa 20

795 45 5

'6 1/MPa 4,3x10-2 1 0 , 3 ~ 1 0 -

2,3x10-~

nowork

A 6

MPa 40 32 55 1 5

Ss l/MPa -0,8*101$

-1 ,gk?O-2 -0,4W0-2 - 3 , 8 ~ 1 0