AU8859398A

AU8859398A - Apparatus for determining specific properties of a discontinuous product to be straightened

Info

Publication number: AU8859398A
Application number: AU88593/98A
Authority: AU
Inventors: Marcus Paech
Original assignee: WITELS APP MASCH ALBERT GmbH
Current assignee: Witels Apparate-Maschinen Albert & Co KG GmbH
Priority date: 1997-07-09
Filing date: 1998-07-08
Publication date: 1999-02-08
Anticipated expiration: 2018-07-08
Also published as: DE59803557D1; BR9811500A; EP1027588A1; JP2001509592A; ATE215225T1; NO20000056D0; AU729381B2; CA2295837A1; EP1027588B1; DE19729438A1; DE19729438C2; NZ501840A; NO20000056L; WO1999002962A1

Abstract

The invention relates to a device for discontinued determination of the E module and/or the yield resistance or yield strength during non-proportional elongation and/or the strain hardening module and/or the parameters of the alternating loads and/or a predetermined curvature of a final straightened product (7), such as metal sheets, strips, profiles, tubes and chiefly straightened products in the form of one or several wires. The inventive device has two receiving members (1, 2) with a respective drive mechanism for applying defined torque on the ends of the straightened product (7) on which a defined torque can be applied. The inventive device also comprises a measuring device (8) for determining curvature of said straightened products (7), wherein one receiving member (1) is stationary and the other receiving member (2) can move horizontally on the clamping plane of the straightened product. According to the invention, the receiving elements (1, 2) are pivotably mounted in opposite directions so that the clamped straightened product (7) can be deformed in an alternating convex or concave manner and the measuring device (8) contains a sensor for the angle of rotation of at least one of the receiving members (1, 2) and a distance sensor to measure the distance between both receiving members (1 and 2).

Description

APPARATUS FOR DETERMINING SPECIFIC PROPERTIES OF A DISCONTINUOUS PRODUCT TO BE STRAIGHTENED The invention relates to an apparatus for the discontinuous determination of the E modulus and/or the apparent yielding point and/or the elongation limit for non proportional extension and/or the hardening modulur and/or parameters of alternating stress applications and/or a predetermined bending of a discontinuous product to be straightened such as metal sheets, strip metal, profiles, pipes and in particular of wire or multiple strand wire products to be straightened comprising two receiving devices each comprising a drive means for the application of defined torques for the ends of the product to be straightened, adapted for a defined bending moment to be applied thereto and including a measuring device for the determining curvatures in the product to be straightened, wherein the one receiving device is stationary and the other is movable horizontally in the clamping plane of the product to be straightened. Such an apparatus is known from DE-Z: Materialprufung 36 (1994) 3, page 61 - 64, it serves for determining non-defined elasticity parameters. For this purpose a bending line of the piece of wire having the configuration of a segment of a circle is to be used. For this purpose, in order to measure the bending moment by means of a sensor, elastic deformations of the spokes of a torque sensor are required. The spoke deformation which correlates with the torque gives rise to a specific tortional rigidity of the torque sensor for which reason the pivotting or bending angle derived 1 from the stepwise information does not correspond to the bending angle of the receiving device. Accordingly, the use of this incorrect bending angle resulting from the motor position results in incorrect commands for the adjustment distance of the movable receiving device. The result is that a bending line of circular segmental configuration of the piece of wire is not attained and accordingly high quality results are not attained. Moreover only straight but not curved pieces of wire can be measured. It is an object of the invention to so improve an apparatus of the aforesaid kind so that it will be possible also to measure and evaluate stresses in alternating directions and of optional frequency even where the material to be straightened is curved. This object is attained by an apparatus having the characteristics of claim 1. The subsidiary claim represents an advantageous further development of this apparatus. In the following the invention will be further elucidated by way of a working example with reference to a drawing Figure 1 and to diagrams Figures 2 to 6. There is shown in: Fig. I a working example of the invention in a diagrammatic view, Fig. 2 a bending moment curvature graph of the first application of stress, 2 Fig. 3 an idealised stress-stretch graph, Fig. 4 a relative bending moment-curvature graph of the first stress application, Fig. 5 a deformation pattern where a first stress is applied and a first alternating stress is applied in the opposite direction, Fig. 6 a bending moment deflection curve for the first stress application and the alternate stress application. The apparatus according to the invention comprises two receiving devices 1,2 each mounted pivotally about a pivotting axis 3 or 4 respectively. The pivotting axis 3 is stationary whereas the pivotting axis 4 is displaceable horizontally, (viz the double arrow) in the plane wherein the pivotting axes 3 and 4 are accommodated. Between the pivotting axes 3 and 4 a distance measuring device - not shown - is provided and at least one receiving device 1,2 is coupled to an angular displacement measuring device - not illustrated. Each receiving device 1, 2 comprises a holder 5 or 6 respectively, facing one another and serving for the fixed accommodation of the end of a product 7 to be straightened. Each receiving device 1,2 is coupled to a not illustrated drive means for turning it in opposite directions (viz the double arrow) about the pivotting axes 3, 4. For this purpose the driving of both receiving devices 1, 2 can proceed by way of a single reversible motor, although each receiving device 1, 2 may alternatively be fitted with 3 its own motor in which case synchronisation of the applied torque and/or of the direction of pivotting can be ensured by appropriate coupling and/or transmission means. Approximately centrally between the two receiving means 1 and 2 a measuring device 8 for determining the curvatures of the product 7 to be straightened is fitted, the respective curvature being calculable from the distances between the product 7 to be straightened and the measuring device 8, these being measured at at least three or even more points. Alternatively the prevailing curvature may be determined from the correlation between the measured pivotting angle of at least one of the receiving means 1, 2 and the measured distance between the receiving devices 1 and 2. The apparatus comprises preferably a storage device 9 and/or a computation unit 10 to be supplied not only with data derived from the measuring device 8 but also by the drive means of the receiving devices 1 and 2. The data concerning the bending moment having been applied and/or the pivotal direction and/or the pivotting angle and/or where appropriate the frequency of the alternating stresses are sensed by the receiving devices 1, 2 and are associated with the determined curvature data. In the case of a first stress application the clamped material 7 to be straightened is subjected to pure bending moments Ma and Mb, wherein M = Ma = Mb. The direction of rotation of such stressing may on the one hand be such that the material I ,to be straightened is subjected to convex deformation or on the other hand 4 concavely in the opposite direction. Due to the horizontally movable arrangement of the axes 4 of the receiving means 2 a tensile loading of the material 7 to be straightened is prevented. The torques about the axes 3, 4 can be applied using non-illustrated factors, sensors and control circuits, timed in a synchronous manner according to predetermined stressing schedules and be measured, and the product to be straightened may also be subjected alternatingly to concave and convex deformation. In this context a first stressing, resulting for example in a convex deformation of the material 7 to be straightened may be followed by a deformation in the opposite direction with a concave result. By alternating deformations the material characteristics of the first stress application, of the first alternating stress application as well as of subsequent further alternating stress applications may be determined. Parameters of the first stress application are the elasticity modulus, the hardening modulus and the apparent yielding points. Bauschinger extensions, Bauschinger stresses and the Bauschinger modulus are parameters of alternating stress applications. For determining the parameters stressing schedules and evaluation procedures have to be set up and bending moments defined in accordance with a stressing plan are applied to the product 7 to be straightened and the resulting curvatures are determined in each case. From a constant bending moment applied over the effective length of the product 7 to be straightened a constant curvature will result over the effective length. As a result of the setting up of different bending moments, initially for example in a convex direction and the determination of the resulting curvatures of the product to be straightened there will follow a correlation between bending moments and curvature applicable to the specific material of the products to 5 be straightened and for the cross-section of the product to be straightened. If an adequate number of data pairs are available a bending moment - curvature graph for the direction of stress application may be established. Functional interrelationships between the bending moment and the curvature may be determined by way of regression analyses. By the employment of analytical and numerical calculating procedures which may be installed in the computation unit 10 the aforesaid parameters of the material of the product to be straightened can be determined. From the informations of the bending moment-curvature graph relevant to the first stress application, the apparent yielding point, the elasticity modulus and the hardening modulus can be calculated. From a bending moment-curvature graph produced as illustrated e.g. in Fig. 2 the parameters: M, Moment at maximum elastic deformation as well as K. Curvature at maximum elastic deformation can be derived. When using the cross-sectional dimensions of the product to be straightened the particular section modulus Wb can be calculated, using the equation applicable to the cross-section. For example for the circular cross-section having a diameter d, there applies Tr x d' Wb = Equation 1 32 The stretching limit a, of the product to be straightened is obtained from Equation 2 6 Mj = Equation 2 Wb Using the value of the curvature at maximum elastic deformation K., of the apparent yielding point o, according to Equation 2 as well as the thickness of the cross section (in the case of a circular cross-section this will amount to the diameter d), the elasticity modulus E may be calculated in accordance with Equation 3. 2 x a, E = Equation 3 d X Ks In order to determine the hardening module V which corresponds to the slope of the compensatory straight line in the plastic deformation range of the stress-stretching graph as illustrated by way of example in Fig. 3, use is made of an equation which is applicable to the respective cross-sectional configuration and which expresses the relationship between the specific bending moment M* and the specific curvature K* for the plastic deformation. The bending moment-curvature graph for first stress application is to be transformed (Fig. 4) by way of M, and K, into its derived presentation M* = f(K*) or alternatively the data pairs (M*, K*) are to be compiled for the contribution of plastic deformation. If it is assumed that the product to be straightened has a circular cross-section the hardening modulus V may be calculated by way of Equation 4. In addition, the elasticity modulus E enters into the equation. For different cross-sectional configurations the correspondingly applicable equations must be used. 7 ±SUL msl-USCTUnXUneCUnun.uoC 2K - K -1 K' 1 2 K'-1'K'1 3 xK'x arccos -- 6x --- x K*+11x x K'- 8 K* K K*K+ The modelling of processes involving elastic-plastic deformation in alternating directions presupposes that the mass laws of the particular materials of which the product to be straightened is composed are adequately well-known. In this context, both the hardening as well as the softening phenomena play a role. A new mass law or material model utilises for the description of softening phenomena the parameters Bauschinger tension, Bauschinger stress and Bauschinger module. The Equations 5 and 6 apply to the first stress application. a = E x E for e Es Equation 5 0 = US + (E - Es) X V for E > Es Equation 6 For the alternating stress application, following after the first stress application in the opposite direction the Equations 7 to 9 apply. GF denotes the yielding point for the alternating stress application. EF denotes the amount of stretching at the yielding point, Ebu the Bauschinger extension, abau the Bauschinger tension and B the Bauschinger modulus. The Bauschinger modulus B denotes the slope of the stress strain graph in the range EF < E Ebau.

a = E x E for E 5 EF Equation 7 0 = OF + (E - EF) x B forEF < E bau Equation 8 a = ou + (E - EU) x V for > 5 bau Equation 9 Fig. 5 shows a schematic illustration of the calculated deformation characteristics (equations 5 to 9) on repeated loading or stressing. In order to be able to calculate the Bauschinger extension Esb and the Bauschinger module B for a stress application subsequent to the first stress application it is necessary to determine (Fig. 6) the parameters K,,U Curvature at the end of the Bauschinger range K Curvature at maximum elastic stressing from the bending moment-curvature graph for an alternating stress application determined metrologically by means of the instrument. The Bauschinger extension es can be calculated for products to be straightened having circular cross-sections (diameter d), where the curvature at the end of the Bauschinger range Kb, in accordance with Equation 10. d x Kau Sbau = Equation 10 2 After determining the maximum elastic extension for alternating stress application EF according to Equation 11 and the yield stress ar according to Equation 12 the Bauschinger modulus B may be calculated by way of Equation 13. d x KF EF = Equation 11 2 CF= E x EF Equation 12 9 Obau - CFF B = Equation 13 Ebau -Er As regards the Bauschinger stress acu Equation 14 applies wherein os represents the apparent yielding point for the first stress application. au = as Equation 14 The Equations 4 to 14 apply to the first quadrant of a local co-ordinate system which corresponds to the first quadrant of the global system illustrated in Fig. 5. In order to determine the material properties during alternating stressing by means of Equations 5 to 14 in accordance with Fig. 5 it is necessary to perform a co-ordinate transformation and a co-ordinate retransformation taking into account change of sign conventions. 10

Claims

1. Apparatus for the discontinuous determination of the E modulus and/or the apparent yielding point and/or a permanent elongation limit for non-proportional elongation and/or the hardening modulus and/or of parameters of alternating stress applications and/or a predetermined bending of a discontinuous product to be straightened (7) such as metal sheets, strips, profiles, tubes and in particular of wire and multi-stranded wire products to be straightened including two receiving devices (1, 2) each comprising a drive means for the application of defined torques for the ends of the product to be straightened (7) adopted for a defined bending moment to be applied thereto and including a measuring device (8) for determining curvatures in the product to be straightened (7), wherein the one receiving device (1) is stationary and the other (2) is movable horizontally in the clamping plane of the product to be straightened (7), characterised in that the receiving devices (1, 2) are mounted to be pivotal in opposite directions in such a manner that the clamped product to be straightened (7) may be deformed convexly or concavely alternatingly and that the measuring device (8) comprises a pivotting angle measuring device for at least one of the receiving devices (1, 2) and a distance measuring device for measuring the distance between the two receiving devices (1 and 2).

2. Apparatus according to claim 1, characterised in that all data of deformation and of applied torques including their directions are fed into a storage unit (9) and/or a computing unit (10). 11 WO 99/02962 PCT/EP98/04254 1/6 oo WO 99/02962 PCTIEP98/04254 2/6 M A *MeBwerte -Ausgleichsgmrade im Bereich der elastischen Verformung mS- - - - - KI Fi. WO 99/02962 PCTIEP98/04254 3/6 Y= (S -F,,)-V + G, G s . .- .- .- -. . . . - . . sI Fi.I WO 99/02962 PCT/EP98/04254 4/6 M* M*s=1 Fig. 4 WO 99/02962 PCT/IEP98/04254 5/6 a = (s - ,) -V + as es E Fi g-B+ F Fig. 5 WO 99/02962 PCT/IEP98/04254 6/6 M Erstbeanspruchung Wechselbeanspruchung Fig. 6