WO2018011092A1

WO2018011092A1 - Material sample, method for establishing a sample geometry, method for determining a material behaviour and/or material characteristic values, stress-strain curve of a material and product

Info

Publication number: WO2018011092A1
Application number: PCT/EP2017/067174
Authority: WO
Inventors: Xiangfan Fang; Robert Grams
Original assignee: Universität Siegen
Priority date: 2016-07-11
Filing date: 2017-07-07
Publication date: 2018-01-18
Also published as: CN109716100A; CN109716100B; DE102016112654B3

Abstract

The invention relates to: a material sample (100) for determining a material behaviour and/or material characteristic values in a load test, characterised in that the material sample (100) has a plastically deformable main deformation section (108), an elastically deformable deformation section (112) and a plastically deformable auxiliary deformation section (114), wherein the main deformation section (108), the elastically deformable deformation section (112) and the auxiliary deformation section (114) are coordinated with one another taking into consideration a sample material, a material dimension, a measuring method and/or a load speed, in order to permit a vibration-reduced determining of deformation forces even with high strain rates; a method for establishing a sample geometry of a material sample (100) of this type; a method for determining a material behaviour and/or material characteristic values in a load test using a material sample (100) of this type; a stress-strain curve of a material, wherein the stress-strain curve is determined using a material sample of this type; and a product, wherein the product is designed using material characteristic values, which were determined using a material sample of this type.

Description

Material sample, method for determining a sample geometry, method for determining a material behavior and / or material properties, stress-strain curve of a material and

product

description

The invention relates to a material sample for determining a

Material behavior and / or material characteristics in one

Load test. Moreover, the invention relates to a method for determining a sample geometry of a material sample. Moreover, the invention relates to a method for determining a material behavior and / or of

Evaluate material in a load test using a material sample. Moreover, the invention relates to a stress-strain curve of a

Material. Moreover, the invention relates to a product. In product development such as e.g. in vehicle or aircraft construction

Materials are regularly used to the limit of load capacity. The assessment of the load-bearing capacity of components under crash loads requires a reliable, reproducible measurement of material characteristics and sufficiently accurate material models that take account of the high strain rate or strain rate up to more than 1000 1 / s.

Usually, the material data, particularly stress-strain curves are, in quasi-static range from about lO ^"4! / ^ To about 10 ^_1 1 / by quasi- static tension-compression testing machines with slower crosshead speed measured. At higher speed servo-hydraulic

Testing machines used, the crosshead can reach a speed of up to 20 m / s. With this, strain rates of up to more than 1000 1 / s can be achieved with correctly designed sample geometry.

The servo-hydraulic machines are easy to handle

Experimental Technique and Evaluation. The high speed of

Machine crosshead is transferred to the samples. This creates shock-like stresses: shock or voltage waves propagate through the sample and periphery and are reflected at impedance and transitions. This results in vibrations of the entire machine sample holder sample system, which are also referred to as system vibrations. The disadvantage of conventional sample geometry is that the measured force signals transmitted via the load cells of the machines or other measuring devices, such as

Strain gauges (DMS), thereby strongly oscillating, so that a separation of the system vibration and the real forces on the samples from certain speeds of about 2.5 m / s

Machine speed, which corresponds to approximately 100 1 / s strain rate at an ISO sample DIN EN ISO 26203-2, 2012-01, is no longer possible. Solutions were developed in which the force is not applied to the sample holder through the load cell of the machine, but directly via strain gauges on the machine

undeformed region of the samples is measured. This results in improved force signals in the average strain rate range up to about 200 1 / s with reasonably usable quality. From a strain rate of 200 1 / s, however, occurring vibrations again reduce the quality of information.

Usually round or flat tensile specimens are used whose geometry (length, width and shape) are standardized. They consist essentially of a narrower or thinner area where plastic deformations are to take place, and a sample shoulder area where no plastic Deformations may take place and what the sample on the sample holder can be clamped.

For the determination of material data at a very high loading speed with strain rate> 500 1 / s to 1000 1 / s mainly the split Hopkinson Bar (SHPB) are used. Very small samples are used. The advantages of the SHPB are the achievable high strain rates of well over 1000 1 / s without the system oscillations disturbing the measurement. The measured force values are therefore free of oscillations and very well usable for the calculation of the stress-strain curves. The disadvantage, however, is that due to the

Measuring technique only smaller strains of about 0.2 to about 0.3 can be measured. An even more serious disadvantage is the very strong different measurement results from one and the same material. Investigations of the influences of the sample geometry on the associated stress and strain

Strain distributions in the deformation range using FEM analyzes have shown that many of the SHPB tests are used for the evaluation of the

Experimental results are fundamental assumptions in reality are not valid: The stress and strain in the very small samples are by no means homogeneous as assumed and the achievement of a quasi-static equilibrium is not always given. The basic requirement for a valid evaluation with this technique is thereby violated. This leads u.a. to overestimate the deformations and deviations of the determined stresses. This o.g.

Phenomena do not occur in a tensile test during the tensile test on a servo-hydraulic tensile testing machine.

For this reason, the measured "apparent" material behavior changes significantly when changing the experimental technique of the servo-hydraulic

Testing machine for SHPB. The results are inconsistent. These serious differences are not physically substantiated. The determination of material data on the three experimental techniques, quasi-static testing machine for the lower, servo-hydraulic testing machine for the middle and SHPB for the high strain rate, therefore does not work. It has not yet been possible, with a uniform sample geometry, to measure oscillation-free, consistent material data under the same conditions from quasi-static 10 ^ 1 / s to high-dynamic 10 * 1 / s strain rates or beyond. Experimental techniques and conditions include the measurement of the force, the deformations, the sample geometry and size, as well as the installation of the samples. The main problem lies in the strong

Vibrations of the force signals, which are indicated on s.g. System vibrations in the sample and the Zugdruckprüfmaschine is due.

The FAT guideline is for the reliable determination of crash relevant, strain rate dependent material characteristics for crash simulations in the

Automotive has been developed and validated by crash tests with demonstrator components and crash simulations. The provisions of this directive allow it to be used in different laboratories

High-speed train trials to identify mission-related, material model-oriented crash characteristics as input data for crash simulations and for the construction of material databases in a consistent, standardized manner and to create a secure database for automotive materials. The developed guideline thus contributes to increasing the predictive accuracy of future ones

Crash simulations and so too road safety. It will be on the

Publication Böhme, W .: FAT guideline "Dynamic Material Characteristics for Crash Simulation", in: MaterialsTesting, Vol. 50 (4), pp. 199-205, 2008.

From the document DE 10 2010 023 727 A1 a method is known for optical force measurement, wherein an elastically deformable and / or an elastically deforming region of a solid is subjected to a change in its geometry by the action of a force

The force of the change in the geometry of the region is detected optically, and wherein the force causing the change of the geometry is determined on the basis of a predetermined, preferably one-to-one force-change of geometry. Context is calculated from the optically detected change in geometry.

From the document DE 102 01 861 A1 a method is known for force measurement in dynamic tensile tests on material samples, in which with a

Force measuring cell, in which at least one force measuring sensor is integrated, a force acting on the material sample force is measured, wherein before, during and after the measurement, the load cell is directly connected to the material sample.

The invention has for its object to improve a material sample mentioned above structurally and / or functionally. In addition, the invention is the

The object of the invention is to improve an initially mentioned method. In addition, the invention has for its object to improve an initially mentioned stress-strain curve. In addition, the invention has the object to improve a product mentioned at the outset structurally and / or functionally.

From the problems listed in the prior art, the results

Problem for the invention presented here. The aim is to develop a method which, by combining all the necessary measures for machines, sample holders, sample geometry and measuring method, for the entire strain rate ranges from quasi-static 10 l / s to dynamic 10 ⁴ l / y and beyond can be. The sample geometry should be used in the entire strain rate range to avoid deviations of the

Material behavior due to changes in Prüfgeometire excluded. The measurement of the force and deformations on the sample must also be comparable.

The object is achieved with a material sample having the features of claim 1. The material sample may be for use in a testing device. The test device may be an electro-mechanical universal testing machine or a servohydraulic testing machine.

The material sample may be made of a metal, a metallic alloy, a steel, a steel alloy, a light metal, a light metal alloy, a non-metal, an organic material, a plastic, a

inorganic material and / or a composite material. The main deformation portion, the elastically deformable deformation portion and the sub deformation portion may be made of the same material. Such a material sample can be described as homogeneous. The main deformation portion, the elastically deformable deformation portion and the sub deformation portion may be made of different materials. Such a material sample can be referred to as inhomogeneous. The material sample may have a longitudinal axis. Of the

Main deformation portion, the elastically deformable deformation portion and the secondary deformation portion may be arranged along the longitudinal axis. The elastically deformable deformation portion may be disposed between the main deformation portion and the sub deformation portion. The material sample can in addition to the main deformation section, the elastically deformable deformation section and the

Sub-deformation portion have a first end portion and a second end portion. The end portions may be sample shoulders. The end portions may be arranged on the material sample in the extension direction of the longitudinal axis at opposite ends of the material sample. The end sections are used for clamping the material sample in a tester. The material sample may have a first transition portion between the first end portion and the main deformation portion. The material sample may have a second one between the main deformation portion and the elastically deformable deformation portion Have transition section. The elastically deformable

Deformation section and the secondary deformation section can connect directly to each other. The minor deformation portion may be locally deformable. The material sample can have a different width or different diameters transversely to the longitudinal axis in sections. The

Material sample can at the secondary deformation section a feeder

exhibit.

The first end portion may be disposed at the first transition portion and at the main deformation portion, respectively. The second end portion may be disposed on the minor deformation portion. The second end portion may serve to firmly clamp the material sample. The first end portion may serve to initiate a loading force or loading movement.

Under a load of the material sample, the main deformation portion is mainly and plastically deformed under the action of a loading force. When a load of the material sample is a plastic deformation

predominantly in the main deformation section. At a load of

Material sample, the elastically deformable deformation section is elastically deformed under the action of a loading force. When a load of the material sample of the secondary deformation section is slightly plastically deformed under the action of a loading force. When a load of the material sample, the secondary deformation portion can be easily deformed locally under the action of a loading force. A plastic deformability of the

The main deformation portion, the elastic deformability of the elastically deformable deformation portion, and the plastic deformability of the minor deformation portion can be deformed

Deformationsabschnitt qualitatively and / or quantitatively relative to each other

describe. Upon loading of the material sample, failure occurs under the action of a loading force in the main deformation section.

The sample material, the material dimension, the measuring method and / or the loading speed may be a vote of the Main deformation section, of elastically deformable

Deformation section and the secondary deformation section influence. The sample material, the material dimension, the measuring method and / or the

Loading speed can be parameter for geometric and

be mechanical design of the material sample. Of the

The main deformation portion, the elastically deformable deformation portion, and the minor deformation portion may be matched with each other so that vibrations are reduced or avoided when the load test is performed on the elastically deformable deformation portion. The material sample may have a smallest at the main deformation section

Have cross-section. The material sample may have a larger cross-section at the elastically deformable deformation portion than at the

Have main deformation section. This can apply in particular to a homogeneous material sample. In an inhomogeneous material sample may also be deviating cross-sectional ratios may be present.

The material sample can at the secondary deformation section a

Have cross-sectional weakening. The cross-sectional weakening can be designed as a recess and / or as a feeder. The cross-sectional weakening can be carried out by means of a sectionally reduced material thickness.

The material sample must have the geometric and mechanical condition at the main deformation section

R ■ A

^I mB3 ^ B3

meet with

R _mBl : tensile strength of the sample material in the main deformation section; A _m : cross-sectional area of the material sample in the

Main deformation portion; R _mB3 'tensile strength of the sample material in the minor deformation section; A _m : cross-sectional area of the material sample in the

In addition to deformation section.

Thus, it can be ensured that the main deformation portion is mainly deformed. In the main deformation section will be

Sample deformations measured to calculate strains. In a homogeneous quasi-isotropic material, such as steel or aluminum, can

assume that R _m is the same in all deformation sections. In the case of an inhomogeneous material, it is necessary to distinguish between the tensile strength of the material in the main deformation section and the tensile strength of the material in

Secondary deformation section. The same applies to the

Yield strength R _P o, 2-

The length of the main deformation section may be, for example, 20 mm to achieve a strain rate of 1000 1 / s at a machine speed of 20 m / s. However, this can be varied depending on the application. The first transition section and the second transition section must be at a

Load the material sample under the action of a loading force together with the main deformation section a homogeneous plane

Maintained state of tension until constriction. The material sample has at least one measuring section on the elastically deformable deformation section. This at least one measuring section may have a defined distance from the main deformation section, from the secondary deformation section and from a sample edge.

The at least one measuring section is to the second transition section and the secondary deformation section a defined distance depending on a material to be tested and a material dimension to be tested

have, so that in the at least one measuring section a homogeneous

Voltage distribution is ensured. To meet this, the at least one measuring section should also have a defined distance depending on one testing material and a material dimension to be tested to free

Have test edges. The exact geometric dimensions, including the mentioned defined distances, may be dependent on the material to be tested as well as the material dimensions.

For the design of the sample contour, the main deformation section, the second transition section, the elastically deformable deformation section and the secondary deformation section for a material should be designed in such a way that a sufficiently large homogeneous stress field propagates in the elastically deformable deformation section over the time of the test duration. The stress field should, based on the area cross-section, be able to represent a true instantaneous test force over the entire duration of the test. Furthermore, the field of tension should be the dimensions of a

are sufficient.

The material sample must have the geometric and mechanical condition on the elastically deformable deformation section

^■ <1 or in other words A _m > - · A _m

^Λ ρΟ, 2Β2 ' ^Λ Β2 ^Λ ρΟ, 2Β2 satisfy, with

R _mm : tensile strength of the sample material in the main deformation section; A _m : cross-sectional area of the material sample in the

Main deformation portion;

R _P Q, 2B2 ^' ■ yield point of the sample material in the elastic

deformable deformation section;

A _B2 : cross-sectional area of the material sample in the elastically deformable

Deformation section.

This ensures that only purely elastic deformations take place there.

At the secondary deformation section, the material sample can determine the geometric and mechanical conditions

or otherwise formulated R _P o, 2B3 _< Λ _{Ι <} RmB3_ _{= 1 for homogeneous} materials

n Λ meet, with

J? _miJ1 : tensile strength of the sample material in the main deformation section; A _m : cross-sectional area of the material sample in the

Main deformation portion;

R _p o, 2B3 ^: yield point of the sample material in the

In addition to deformation section;

B3 ^: cross-sectional area of the material sample in the

In addition to deformation section;

R _mBi . Tensile strength of the sample material in the minor deformation section.

This is to ensure that the minor deformation portion is easily plastically deformed while the main deformation portion still undergoes a major deformation to breakage. This is to ensure that the sample area is slightly plastically deformed around the area of the recess and / or the feeder in the secondary deformation section, and thus the vibration energy is absorbed and converted during the

Main deformation section undergoes major deformation. The design of the main deformation section, the second

Transition portion, the elastically deformable deformation portion and the secondary deformation portion is essential for a low-vibration and accurate measurement of force signals.

The recess and / or the indentation on the secondary deformation section can / at least partially be oval, rectangular or round. A limitation of the recess and / or the indentation on the Sub-deformation section may / may be at least partially oval, rectangular or round.

The material sample may have a round, oval, polygonal and / or square cross section. The material sample may be made of a flat product. The material sample may have at least one notch.

In addition, the object underlying the invention is achieved with a method having the features of claim 9.

By means of the finite element method (FEM), the required distances of the at least one measuring section from the main deformation section, from the elastically deformable deformation section and from a sample edge can be defined. Using the FEM, the sample contour, in particular the sample contour of the main deformation section, of the second

Transition portion, the elastically deformable deformation portion and the Niedergeformationsabschnitts be determined. The required distances can alternatively or additionally be determined experimentally.

In addition, the object underlying the invention is achieved with a method having the features of claim 10.

The force readings can be recorded using strain gauges (strain gauges). The strain gauges can be pre-calibrated. A measurement is performed on the elastically deformable deformation portion. The sample can preferably be provided on both sides with a respective DMS, which are interconnected as a half bridge. As a result, influences of higher-order modes, such as modes second, third, fourth, etc., which are expressed primarily by structural bending, can be compensated. The force measurement can be done on two sides of the material sample. The force measurement values can also be detected, for example, by means of an optical method. The material sample can be loaded monoaxially, biaxially or multiaxially with tension or pressure. The material sample can be used with a strain rate in a wide Dehnratenbereich of preferably 10 ⁴ to 10 ⁴ 1 / s.

In addition, the object underlying the invention is achieved with a stress-strain curve having the features of claim 13.

In addition, the object underlying the invention is achieved with a product having the features of claim 14. The product may be a workpiece. The product can be an intermediate. The product can be

Be finished product. The product can be automotive product. The product can be an industrial product.

In summary and in other words, the invention thus provides a new method for low-vibration force measurements in dynamic material tests using a new sample geometry.

In addition to two sample shoulders for a sample clamping, a sample can have five deformation sections with different widths or diameters, which are all smaller than those of the sample shoulder. A force application for a tensile or compressive test can be carried out in the first end portion, while in a second end portion, the sample must be firmly clamped and immovable. The main deformation portion may have a smallest dimension in width and thickness direction. In this area, a real plastic deformation should take place until a break. For inhomogeneous materials, the elastically deformable deformation section in width and / or

Thickness direction to be larger than the main deformation section.

In a distance to be defined and determined starting from one end of an outgoing radius of a second transition section, a cutout in the sample and / or at the edge of the sample can be introduced for cross-sectional weakening. This recess can have various shapes, for example oval, rectangular, round, etc., and be arbitrarily complex. Excitations which put the sample in a vibrational state can be found in a secondary deformation section are converted into plastic deformation and displacement. The energetic conditions, such as kinetic energy, internal work, work of the volumetric forces and work of the surface forces, can in the elastically deformable deformation section and in the

Sub-deformation section thereby changed so that a

vibration-free force measurement in elastically deformable

Deformationsabschnitt can be performed.

Both a geometric shape and material properties of

Main deformation portion, the second transition portion, the elastically deformable deformation portion and the minor deformation portion may have a strong influence on test results. The following requirements must be met:

The first transition section, the main deformation section and the second transition section should be designed such that in

Main deformation section a homogeneous plane stress state up to

Constriction can be maintained;

The geometry of the main deformation section, the second

Transition portion, the elastically deformable deformation portion and the secondary deformation portion should be adapted for a material such that a significant vibration reduction at faster

Stress compared to conventional geometries can be seen. In this case, the second transition section and the elastically deformable

Deformation be designed as short as possible without jeopardizing the following requirement. A relationship of the weakest

The cross section of the minor deformation section to the weakest cross section of the main deformation section should be selected as much as possible so that failure does not occur in the minor deformation section;

The geometry of the main deformation section, the second

Transition portion, the elastically deformable deformation portion and the secondary deformation portion is to be designed for a material such that elastically deformable deformation portion, on the Furthermore, it is intended to represent the true instantaneous test force over the entire test duration, based on the area cross section, and, furthermore, it should correspond to the dimensions of the applied test

Sufficient measuring means.

In particular, optional features of the invention are referred to as "may." Accordingly, there is an embodiment of the invention each having the respective feature or features.

With the invention, an information quality of measured values is improved. By this invention, system vibrations in a measuring field are largely avoided, so that there the force signals without the superimposed

Vibrations can be measured. This sample can be used in the strain rate range between preferably 10 ^"4 1 / s to 10 ⁴ 1 / s and beyond, using all common existing machines, sample holders, and / or measuring methods The same sample geometry can be used throughout the strain rate range. This will cause deviations of one

Material behavior, due to changes in the test geometry excluded. Measurements of force and deformations on the sample are comparable.

Force signals with, for example, max. 1% Delta F can be measured with an effective strain rate of well over 1000 1 / s, almost free of oscillation.

Hereinafter, embodiments of the invention become homogeneous

Materials with reference to figures described in more detail. Homogeneous materials are materials whose mechanical properties are largely independent of location, which is the case with metallic materials with good production conditions. For composites and plastics, i.a. Fiber-reinforced plastics, the properties in the workpiece are often location-dependent. From this description, further features and

Advantages. Concrete features of these embodiments may represent general features of the invention. Associated with other characteristics Features of these embodiments may also constitute individual features of the invention.

They show schematically and by way of example:

1 shows a sample of material with a main deformation section, a

elastically deformable deformation portion and a

Secondary deformation section in overall view and a detailed view of the elastically deformable deformation section and the

In addition to deformation section,

FIG. 2 shows a comparison of force measurements on material samples, and FIG. 3 shows a stress-strain curve and associated changes in a strain rate during a constant tensile test

Machine speed.

Fig. 1 shows a material sample 100. The material sample 100 is used to determine material characteristics in a load test. The material sample 100 has a longitudinal axis 102. The material sample 100 is symmetrical to the longitudinal axis 102. The material sample 100 has a first end portion 104, a first transition portion 106, a

Hauptdeformationsabschnitt 108, a second transition section 1 10, an elastically deformable deformation portion 1 12, a

Second deformation section 1 14 and a second end portion 1 16 on.

The end sections 104, 16 serve for clamping the material sample 100 into a test device. It serves the end portion 1 16 for fixed clamping and the end portion 104 to initiate a test force or test movement of the test apparatus. At the end portions 104, 16, the material sample 100 has the greatest width. At the main deformation portion 108, the

Material sample 100 the smallest width. The first transition section 106 is one of the first end section 104 to the main deformation section 1 08 running without sudden decreasing width. At the first

Transition section 1 06 is a radius available.

On the elastically deformable deformation portion 1 12, the

Material sample 100 has a greater width than at the main deformation section 108. The second transition portion 1 10 is connected to one of the

Main deformation portion 108 to the elastically deformable

Deformationsabschnitt 1 1 2 executed jumpless increasing width. At the second transition section 1 10 a radius is present. At the second deformation section 12 1, the material sample 100 has a measuring field 1 18. The measuring field 118 is preferably rectangular with a length I and a width b. The measuring field 1 18 has to the second transition section 1 10 a distance Ii, to the secondary deformation section 1 14 a distance l ₂ and to a

Outer edge 120 of the material sample 100 distances bi and b2 on. This o.g.

Distances and radii were determined as described by FEM or experiments

At the secondary deformation section 1 14, the material sample 1 00 has a recess 122 and a feeder 126. The recess 122 has a circumferential inner edge 124.

The secondary deformation portion 1 14 is the side of the recess 122 and the feeder 126 locally deformable.

The geometry of the material sample 100 is determined using the finite element method taking into account the sample material, the measurement method and / or the loading speed. The main deformation portion 108, the elastically deformable deformation portion 1 12 and the

Subordinate deformation portion 1 14 are coordinated so that when performing a load test, the main deformation portion 1 08 plastically deformed and deformed to failure, the elastically deformable deformation portion 1 12 elastically deformed and the secondary deformation portion 1 14 slightly plastically deformed, wherein at high Strain rates on the elastically deformable deformation portion 1 12, the vibrations are reduced or avoided. Of the

Main deformation portion 108, the elastically deformable

Deformationsabschnitt 1 12 and the secondary deformation section 1 14 are coordinated such that in the elastically deformable

Deformationsabschnitt 1 12, over the time of the test period, a sufficiently large homogeneous stress field in the measuring field 1 18 propagates, based on a cross section in the elastically deformable deformation section 1 12, represents a true instantaneous test force over the entire duration of the test and the dimensions of an applied measuring means , For example, strain gauges, is sufficient.

In the main deformation section 108, sample deformations are measured to calculate strains. The first transition section 106 and the second transition section 110 maintain a homogeneous plane stress state until constriction under load of the material sample 100 under the action of a loading force along with the main deformation section 108. The secondary deformation portion is easily plastically deformed under a load of the material sample 100 under the action of a loading force, while the main deformation portion 108 still undergoes a major deformation to breakage. Due to the slightly plastic deformation of the sample area around the

Recess 122 and the retraction 126 is converted to vibrational energy and vibrations are damped.

Fig. 2 shows a comparison of force measurements on material samples. In a diagram 200, a time is plotted on an x-axis and a force on a y-axis. In a measurement with a load cell results for a material sample according to the prior art in a tensile test under

Exposure of the tensile force a force curve 202 with significant signal fluctuations. In a measurement with strain gauges results for the material sample according to the prior art in a tensile test under the action of tensile force a force curve 204 with somewhat reduced, but still clear Signal fluctuations. In a measurement with strain gauges results for the material sample according to the invention, such as material sample 100 of FIG. 1, in a tensile test under the action of the tensile force a force curve 206 with almost no signal fluctuations. Fig. 3 shows a stress-strain curve with the associated change in the strain rate. In the diagram 300 the true strain is plotted on the x-axis, the true stress on the yi-axis and a true strain rate on the y ₂ -axis. In the case of a force measurement with strain gauges, a stress-strain curve 302 results for the material sample according to the invention, such as material sample 100 according to FIG. 1, and with a strain rate variation from 100 s to 8000 1 / s at a strain rate curve 304.

Reference material sample

longitudinal axis

first end section

first transitional section

Main deformation section

second transitional section

elastically deformable deformation portion secondary deformation portion

second end section

measuring field

outer edge

recess

inner edge

Indentation diagram

force curve

Force curve diagram

Stress-strain curve

Dehnratenverlauf

Claims

claims

1. Material sample (100) for determining a material behavior and / or material properties in a load test, characterized in that the material sample (100) has a plastically deformable

Main deformation portion (108), an elastically deformable

Deformationsabschnitt (1 12) and a plastically deformable

Having secondary deformation portion (1 14), wherein the

Main deformation section (108), the elastically deformable

Deformationsabschnitt (1 12) and the secondary deformation section (1 14) are adjusted to one another taking into account a sample material, a material dimension, a measurement method and / or a loading speed to allow a low-vibration determination of deformation forces even at high strain rates.

2. Material sample (100) according to claim 1, characterized in that the material sample (100) at the main deformation portion (108) has a smallest cross-section, at the elastically deformable deformation portion (1 12) has a larger cross-section than at the main deformation portion (108) and at the secondary deformation section (1 14) a

Cross-sectional weakening, in particular a recess (122) and / or a feeder (126).

3. Material sample (100) according to at least one of the preceding claims, characterized in that the material sample (100) on the

Main deformation section (108) the geometric and mechanical

condition

R ■ A

l mB \ ^Λ Β \ ^ i

R ■ A

^J m £ 3 ^Λ Β3

fulfilled, with R _mBl : tensile strength of the sample material in the main deformation section (108);

A _m : cross-sectional area of the material sample (100) in the

Main deformation section (108);

R _mBi : Tensile strength of the sample material in the minor deformation section

(1 14);

A _m : cross-sectional area of the material sample (100) in the

Secondary deformation section (1 14).

Material sample (100) according to at least one of the preceding claims, characterized in that the material sample (100) on the elastically deformable deformation portion (1 12) at least one measuring section (1 18), of the main deformation section (108), of the secondary deformation section (1 14) and from a sample edge (120) has a defined distance depending on a material to be tested and a material dimension to be tested.

Material sample (100) according to at least one of the preceding claims, characterized in that the material sample (100) on the elastically deformable deformation portion (1 12) the geometric and

mechanical condition

R ■ A

l mB \ ^Λ ΒΙ _< i

R ■ A ^~~

¹ ρϋ, 2Β2 ^ B2

fulfilled, with

R _mB1 : tensile strength of the sample material in the

Main deformation section (108);

A _m : cross-sectional area of the material sample (100) in the

Main deformation section (108);

R _{p0 2B} 2 '■ yield point of the sample material in the elastic

deformable deformation section (1 12); A _B2 : cross-sectional area of the material sample (100) in the elastically deformable deformation portion (1 12).

6. Material sample (100) according to at least one of the preceding claims, characterized in that the material sample (100) on the

Second deformation section (1 14) the geometric and mechanical conditions

R ■ A R ■ A

- - ^ ί- ^ L-> \ _{u nc} ("> ^{m B1} <; \

R · A ^~ R ■ A

¹ ρΟ, 2ΒΪ ^l mB3 ^Λ Β3

fulfilled, with

R _mm : tensile strength of the sample material in the

Main deformation section (108);

A _m : cross-sectional area of the material sample (100) in the

Main deformation section (108);

R _p o, 2B yield point of the sample material in the

Secondary deformation section (1 14);

A _B3 : cross-sectional area of the material sample (100) in the

Secondary deformation section (1 14);

R _mB3 : tensile strength of the sample material in the

Secondary deformation section (1 14).

7. Material sample (100) according to at least one of the preceding claims, characterized in that the recess (122) and / or the indentation (126) on the secondary deformation section (1 14) is at least partially oval, rectangular or round.

8. material sample (100) according to at least one of the preceding claims, characterized in that the material sample (100) has a round

Has cross-section, has a quadrangular cross-section, is made of a flat product and / or has at least one notch.

9. A method for determining a sample geometry of a material sample (100) according to at least one of claims 1 to 8, characterized in that the sample geometry at least in sections using the finite element method, taking into account a sample material, a

Material dimension, a measurement method and / or a

Loading speed is determined such that in one

Stress test mechanical stresses on a to the elastically deformable deformation portion (1 2) arranged measuring field (1 18) are homogeneous and represent a true instantaneous test force over a whole test period.

10. Method for determining a material behavior and / or of

Evaluate material in a load test using a

Material sample (100) according to at least one of claims 1 to 8, wherein at least one of the following steps is carried out:

Placing a measuring means on the elastically deformable deformation portion (1 12);

- placing the material sample (100) on a test device;

Loading the material sample (100) and thereby detecting

Power to eat;

characterized in that a force is measured on an elastically deformable deformation portion (1 12) arranged measuring field (1 18) by means of electrical strain sensors and / or an optical method.

1 1. A method according to claim 10, characterized in that the force measurement takes place on two sides of the material sample (100).

12. The method according to at least one of claims 10 to 1 1, characterized

in that the material sample (100) is loaded monoaxially, biaxially or multiaxially with tension or pressure.

13. stress-strain curve of a material, characterized in that the stress-strain curve using a sample of material (100) according to at least one of claims 1 to 8 is determined.

14 product, characterized in that the product is designed using material characteristics, which were determined using a material sample (100) according to at least one of claims 1 to 8.