Method and apparatus for determining static and dynamic characteristics from a viscous-elastic material

Claim 2

Method for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU4## wherein Γ is the common gamma function and j is √-1.

Claim 3

Method as defined in claim 1, in which such a deformation is applied that the total change in the cross-section of the deformed material which lies substantially at right angle to the direction of the applied force F, is to be neglected.

Claim 4

Method as defined in claim 1, in which said force F is applied but to a portion from a determined side of the material, in such a way that the total deformation of said material is to be neglected.

Claim 5

Method as defined in claim 3, in which said force F is applied in the form of a substantially point-like pressure load.

Claim 6

Method as defined in claim 3, in which said deformation is applied by means of a ball-shaped impression body over a depth which is equal at the most to the radius of said body.

Claim 7

Method as defined in claim 5, in which use is made of a ball-shaped impression body with a diameter lying between 0.5 and 10 mm, preferably between 0.5 and 3 mm.

Claim 8

Method as defined in claim 1, in which said deformation is applied to the material in less than 0.5 seconds and preferably less than 0.1 second.

Claim 9

Method as defined in claim 1, in which use is made of a test material sample the thickness of which is at least equal to five times the maximum deformation depth.

Claim 10

Method as defined in claim 1, in which use is made of a test sample with such a size that the ratio of the shortest spacing from the sample edge to the impression body, to the body width is at least four.

Claim 11

Method as defined in claim 1, in which use is made of an automobile tire as test sample.

Claim 12

Method as defined in claim 1, in which said force F is determined as a function of the time by means of periodic measurings or recordings with a frequency which decreases after said constant deformation has been reached.

Claim 13

Method as defined in claim 11, in which the measurings are performed from the moment zero up to before reaching said constant deformation with a frequency in the range from 50 to 200 measurings per second.

Claim 14

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α wit E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU5## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a piezoelectric force transducer which is isolated from temperature changes to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment when said movable component is brought from a rest position to an impression position.

Claim 15

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α wit E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU5## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a piezoelectric force transducer which is isolated from temperature changes to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment when said movable component is brought from a rest position to an impression position.

Claim 16

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU6## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, said component comprising a rod which is slidably mounted inside a fixed guide and is provided at that end thereof removed from the impression body, with a stop member which cooperates on the one hand with a resilient member provided between the guide and the stop member, and on the other hand with a cam which is rotatable about a rotation axis which lies substantially at right angle to the rod axis, with an eccentricity which corresponds substantially to half said constant determined movement distance of the rod and thus can bring said rod together with the impression body, from a rest position in the direction of a test sample to an impression position, whereby in said impression position the stop member is pressed by the cam against the guide in such a way that in said position, a rigid dynamic connection is obtained between the rod, the impression body and the apparatus frame, and whereby detection means are provided for switching on said force transducer at that moment when the rod is moved in the direction of the test sample towards said impression position.

Claim 17

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU6## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, said component comprising a rod which is slidably mounted inside a fixed guide and is provided at that end thereof removed from the impression body, with a stop member which cooperates on the one hand with a resilient member provided between the guide and the stop member, and on the other hand with a cam which is rotatable about a rotation axis which lies substantially at right angle to the rod axis, with an eccentricity which corresponds substantially to half said constant determined movement distance of the rod and thus can bring said rod together with the impression body, from a rest position in the direction of a test sample to an impression position, whereby in said impression position the stop member is pressed by the cam against the guide in such a way that in said position, a rigid dynamic connection is obtained between the rod, the impression body and the apparatus frame, and whereby detection means are provided for switching on said force transducer at that moment when the rod is moved in the direction of the test sample towards said impression position.

Claim 18

Apparatus as defined in claim 14, in which said detection means comprise at least one photocell with an interrupter which is movable in front thereof and is fast relative to said cam.

Claim 19

Apparatus as defined in claim 14, in which said cam is provided with a ball bearing or small wheel arranged eccentrically, the eccentricity thereof corresponding substantially to half said constant movement distance of the rod.

Claim 20

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU7## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment where said movable component is brought from a rest position to an impression position, said detection means and force transducer being connected to an electronic circuit which converts the analog force signal measured by said force transducer into a digital form and couples the digital data to the memory of a computer, and said electronic circuit comprising means causing the converting of the analog force signal into digital form decreases in the frequency thereof after a determined time interval which is longer than the time required to bring said movable component to said impression position.

Claim 21

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU7## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment where said movable component is brought from a rest position to an impression position, said detection means and force transducer being connected to an electronic circuit which converts the analog force signal measured by said force transducer into a digital form and couples the digital data to the memory of a computer, and said electronic circuit comprising means causing the converting of the analog force signal into digital form decreases in the frequency thereof after a determined time interval which is longer than the time required to bring said movable component to said impression position.

Claim 22

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU8## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment where said movable component is brought from a rest position to an impression position, and a height-adjustable table on which said test sample can be arranged against the impression body before pressing same into the sample, said pressure body being mounted at the free end of an arm which forms a substantially rigid unit with a projecting support on which said table is adjustably mounted underneath the pressure body.

Claim 23

Apparatus for determining static and dynamic material characteristics, more particularly the elasticity modulus E' and loss modulus E", from a viscous-elastic material the relaxation modulus E(t) of which fulfills the equation E(t)=A+Bt - α with E(t) being the relaxation modulus, A and B being constants, and t the time in seconds, as a function of the frequency the material is subjected to, in which to that material the above defined characteristics of which are to be measured, there is applied by means of a force F, a constant predetermined deformation by compression or pressing-in and said deformation is retained for at least 10 seconds and preferably at least 15 seconds, whereby the building-up of force from a moment zero which corresponds to that time where said force is applied, and the decrease after said constant deformation has been reached, is measured as a function of the time, and said material characteristics are determined on the basis of the following formulas: E(t)=f[F.sub.1 (a), F.sub.2 (b), F(t)] (I) with a=impression depth; b=size and shape of the impression body or section of test sample E(t)=A+Bt.sup.-α (II) E.sup.x (ω)=E'(ω)+jE"(ω) (III) with ω=2πF wherein f is the frequency; ##EQU8## wherein Γ is the common gamma function and j is √-1, said force F being applied by a pressure body which is made fast together with a force transducer to a component which is movable over a constant determined distance, which force transducer measures the force exerted along the component movement direction on said pressure body as a function of the time, whereby detection means are provided to switch on said force transducer at that moment where said movable component is brought from a rest position to an impression position, and a height-adjustable table on which said test sample can be arranged against the impression body before pressing same into the sample, said pressure body being mounted at the free end of an arm which forms a substantially rigid unit with a projecting support on which said table is adjustably mounted underneath the pressure body.

Claim 24

Apparatus as defined in claim 18, in which the table is swingable outwards away from below said pressure body.