Detect the method for flatness of magnesium alloy section bar after tensile straightening
Technical field
The present invention relates to a kind of detection method of section bar tension straingtening effect, particularly a kind of method that detects flatness of magnesium alloy section bar after tensile straightening.
Background technology
The magnesium alloy extrudate is owing to reasons such as mould state and blank homogeneitys, extrudes the phenomenon that the back exists crooked and kinking usually, also exists profile straight in the time of minority, but section bar internal stress distribution non-uniform phenomenon, thereby influences the situation of its usability.For eliminating these phenomenons, need carry out tension straingtening to the section bar after the extruding.But the temperature-room type plasticity of magnesium alloy is poor, need be heated in 150 ℃~250 ℃ scopes to carry out tension straingtening.Suitable temperature and the stretcher strain rate of the magnesium alloy profiles tension straingtening of the different trades mark is not quite similar, and when the tension straingtening technology of formulating separately, needs to be optimized respectively at the alloy product of the various trades mark.Promptly when certain alloy is carried out the tension straingtening process optimization, need to these alloy profile goods under different temperatures and extension elongation rate, carry out the comparison of flatness.Need set up a kind of judgment criteria thus to flatness after the tension straingtening.
At present, whether the detection of flatness after the tension straingtening generally was that section bar is lain on the straight verifying bench during magnesium alloy profiles was produced, observe section bar and fit tightly with table top, have seamlessly, and the upset section bar is repeatedly observed the situation of its different side profiles and verifying bench surface applying.If between section bar a part and the verifying bench surface slit is arranged, available clearance gauge is accurately measured the slit height, is used to weigh the flatness of section bar.Usually the strict degree that requires according to the product flatness is set ultimate value, and ultimate value is selected between 1 millimeter to 4 millimeters usually.Slit between per 1 meter length of section bar and the table top is qualified to be no more than prescribed limit values.The section bar slit of each position and detection platform is along its length then thought and is aligned successfully all less than prescribed limit values.Otherwise, need carry out tension straingtening again.
Adopt above-mentioned with section bar to be checked and verifying bench table top than the method for leaning on, because the cut lengths of shape product to be checked is generally all more than several meters, when the bending section bar is placed on the horizontal stand, only there is some part of section bar to support its weight, because of being subjected to gravity effect, slit height between section bar and the table top can not reflect truly reverse, crooked degree, influence judgement thus to section bar flatness after the tension straingtening.For reducing the influence of section bar deadweight, must segmentation compare, stipulate that usually the height in slit on per 1 meter distance is no more than certain ultimate value, set at the method for this segmentation comparison.When detecting piecemeal along its length, also compare with the check table top in side that will section bar is different, makes that the checkability of whole section bar flatness is very low.In addition; though adopt profile can detect the position of shape bending than the detection method of leaning on; can not judge but whether section bar exists uneven internal stress to distribute; can't provide comprehensive information for the flatness of magnesium alloy section bar after tensile straightening test and appraisal; usually can make the major parameter extensibility in the magnesium alloy profiles tension straingtening production technology that obtains thus less than normal, and not reach best leveling effect.In addition, verifying bench adopts the cast iron panel more, has strict high-flatness for guaranteeing it, need through " plane processing, annealing and natrual ageing " repeatedly repeatedly, could satisfy request for utilization, thereby the manufacturing cycle is long, cost of manufacture is also high.For this reason, need flatness and the distribution of uneven internal stress that a kind of method that can overcome above-mentioned deficiency detects magnesium alloy profiles.
Summary of the invention
The purpose of this invention is to provide a kind of method that detects flatness of magnesium alloy section bar after tensile straightening, adopt the flatness after the method detects magnesium alloy profiles tension straingtening, can judge exactly that detected section bar twists, the crooked and position that has the internal stress skewness.
The object of the present invention is achieved like this: have the section configuration after the tension straingtening symmetric, or section configuration is local horizontal being clamped on the platform of asymmetrical magnesium alloy profiles, allowing an end of section bar stretch out platform is cantilever-shaped formation natural bow and keeps stationary state, if one horizontal linear be positioned at the section bar cantilever segment above or below, equidistant on horizontal linear some calibration points are set, distance≤300mm between its two adjacent calibration points, with each calibration points on the horizontal linear is that intersection point is drawn vertical line respectively and the section bar cantilever segment intersects, intersection point with each vertical line and section bar cantilever segment is a coordinate points, measure the distance of each coordinate points intersection point to the horizontal linear successively, according to the data that record, on coordinate diagram, draw the position of each coordinate points, and with these coordinate points smooth connection successively, an actual measurement simulation curve when drawing section bar and being in the natural bow state; Again this section bar is rotated an angle around the centre of form, local horizontal being clamped on the platform, its cantilever segment that stretches out platform still forms natural bow and keeps stationary state, measure the distance of each coordinate points successively to the horizontal linear intersection point, according to the data that record, on coordinate diagram, draw the position of each coordinate points, and with these coordinate points smooth connection successively, section bar is in another actual measurement simulation curve under the natural bow state when being depicted in another angle;
Then, the actual measurement simulation curve that section configuration is had at least two different angles that symmetric magnesium alloy profiles records compares, the originating point that the curve of different angles can not coincide mutually is section bar and position crooked, that reverse or exist the internal stress inequality occurs; It perhaps is the actual measurement simulation curve of two different angles recording of asymmetrical magnesium alloy profiles with section configuration, the theoretical curve that is calculated according to specific centre of form equatorial moment of inertia that has with angle position separately compares respectively respectively, and the originating point that two curves that contrasted can not coincide mutually is section bar and position crooked, that reverse or exist the internal stress skewness occurs; The curve that is contrasted coincide mutually and judges that then the flatness of section bar tension straingtening meets the requirements.
Owing to adopted such scheme, compare by the actual measurement simulation curve that the magnesium alloy profiles behind the drawn straightening process is under the natural bow state when the different angles, perhaps compare with the simulation curve of actual measurement and the theoretical curve that is calculated according to specific centre of form equatorial moment of inertia respectively, position crooked, that reverse occurs except detecting section bar, can also detect the position that there is the internal stress skewness in section bar.Its principle is, after detected section bar local horizontal was fixed on the platform, the cantilever segment that stretches out platform can produce crooked under the effect of gravity, and gravity is evenly distributed on the section bar, direction vertically downward, the load of unit length is q.By the mechanics of materials as can be known, the deflection equation of straight section bar is:
In the formula (1), v is an amount of deflection, and q is a gravimetric density, E be elastic modulus (for most of magnesium alloys, E=45GPa), I is a centre of form equatorial moment of inertia, and l is the length of cantilever segment, x be on the sample cantilever segment any point to the distance of fixed endpoint.
q=ρgπD
2/4 (2)
D is the diameter of bar in the formula (2), and the density of magnesium alloy is got ρ=1.8 * 10
3Kg/m
3, g is an acceleration of gravity.
By above-mentioned deflection equation as can be known, the q of same section bar, E and l are just the same, have only centre of form equatorial moment of inertia I to be subjected to the influence of section bar rotational angle.
For section configuration has symmetric magnesium alloy profiles, its centre of form equatorial moment of inertia I that rotates after the different angles is identical, under the identical situation of centre of form equatorial moment of inertia I, density evenly, straight shape, do not have flexion torsion and internal stress free section bar pockety, the natural torsion curve that forms around centre of form different rotation angle of actual measurement should fit like a glove; Otherwise, if the natural torsion curve around the formation of centre of form different rotation angle of actual measurement is misfitted, illustrate that promptly this section bar exists Density Distribution inhomogeneous, internal stress phenomenon pockety bending has taken place, reversed or has existed.Usually extrudate Density Distribution in the longitudinal direction is uniform, so by the method for natural torsion curve contrast can judge section bar whether taken place crooked, reverse or have the internal stress skewness, and can judge at length direction from where beginning to have taken place above-mentioned defective.
For the asymmetrical magnesium alloy profiles of section configuration, under the identical situation of centre of form equatorial moment of inertia I, density is even, straight shape, there is not flexion torsion and internal stress free section bar pockety, the natural torsion curve of actual measurement should be identical substantially with the theoretical curve that is calculated according to specific centre of form equatorial moment of inertia I that this angle has, if the natural torsion curve of actual measurement begins to misfit with the theoretical curve somewhere in the longitudinal direction of being calculated according to specific centre of form equatorial moment of inertia I, illustrate that then section bar at this place bending has taken place, reverse or have an internal stress phenomenon pockety.
The present invention adopts the simulation curve of mapping magnesium alloy profiles when the natural bow state, compare by simulation curve different angles, perhaps the simulation curve of same angle and the theoretical curve that is calculated according to specific centre of form equatorial moment of inertia of this angle are compared, can effectively detect the position of the bending after the magnesium alloy profiles tension straingtening and the internal stress skewness position of existence, for the flatness of magnesium alloy section bar after tensile straightening test and appraisal provide comprehensive information, help optimizing section bar tension straingtening technology.
The invention will be further described below by specific embodiment.
Description of drawings
Fig. 1 is the instrumentation plan of profile shapes simulation curve;
Fig. 2 is the comparison diagram of the simulating shape curve before the section bar tension straingtening;
Fig. 3 is the comparison diagram of the simulating shape curve of section bar after with 1% extensibility tension straingtening;
Fig. 4 is the comparison diagram of the simulating shape curve of section bar after with 2% extensibility tension straingtening.
Embodiment
Referring to Fig. 1, with a portion of end office (EO) of the magnesium alloy profiles after the tension straingtening 3 by clamping device 2 horizontal being clamped on the platform 1, described magnesium alloy profiles 3 comprises that section configuration has symmetric or section configuration is asymmetrical magnesium alloy profiles, allowing the other end of section bar stretch out platform is cantilever-shaped formation natural bow and keeps stationary state, its natural bow of cantilever segment termination that stretches out platform is less than podium level, and the cantilever segment that allows section bar stretch out platform can be in a kind of natural torsion state that not influenced by external force.If one horizontal linear 4 is positioned at the below of section bar cantilever segment, this horizontal linear 4 can draw on the level ground, perhaps draws having on the base plate of surface level.Equidistant on horizontal linear 4 some calibration points are set, distance≤300mm between its two adjacent calibration points, with each calibration points on the horizontal linear is that intersection point is drawn vertical line respectively and the section bar cantilever segment intersects, intersection point with each vertical line and section bar cantilever segment is a coordinate points, measure the distance h of each coordinate points intersection point to the horizontal linear successively, according to the data that record, on coordinate diagram, draw the position of each coordinate points, and with these coordinate points smooth connection successively, an actual measurement simulation curve when drawing section bar and being in the natural bow state.
The maximum extended jib-length of detected section bar is subjected to the restriction of the centre of form equatorial moment of inertia I of flat surface height and this section bar.According to deflection formula, the formula of stating of seing before (1), when the long and centre of form equatorial moment of inertia I of the length of stretching out cantilever was enough big, the ground that will hang because amount of deflection is excessive of end made above-mentioned detection method to implement.The shape bending crooked and that action of gravity produces of considering section bar self when detecting operation is superimposed, strengthen the degree that the cantilever termination lets droop and, with the platform level height is that 1.5m is an example, section bar cantilever maximum length should guarantee that the amount of deflection of termination is advisable about 1.2m, can not contacted to earth in section bar cantilever termination.Can find out the section bar of different section shape and size, the termination deflection value of cantilever extension elongation correspondence, and the theoretical maximum extended length when the termination amount of deflection is controlled at 1.2m according to following table.Surpass this maximum extension elongation and, can make the two ends of different directions stretch out platform by the clamping section middle part and detect for length less than the section bar of its twice.External part qualification length saw the following form when common section bar deflection theory value was 1.2 meters:
Here the magnesium alloy pole that with the diameter is 16mm is that example is specifically described: with one as yet not the diameter of tension straingtening be that 16mm, length are that an end of the AZ31 magnesium alloy pole of 5m is clamped on the platform of a high 1.5m with clamping device, it is held fixing 50mm length and partly is the level of state, allow the other end of pole length 4.5m stretch out platform and be cantilever-shaped formation natural bow, and making it keep stationary state, its natural bow that stretches out the cantilever segment termination of platform is about 1.2m.A horizontal linear draws on the level ground below the unsettled end of pole, some calibration points are set on horizontal linear equidistantly, distance between its two adjacent calibration points is 200mm, with each calibration points on the horizontal linear is that intersection point is drawn vertical line respectively and the pole cantilever segment intersects, intersection point with each vertical line and pole cantilever segment is a coordinate points, measure the distance of each coordinate points intersection point to the horizontal linear successively, according to the data that record, on coordinate diagram, draw the position of each coordinate points, and with these coordinate points smooth connection successively, an actual measurement simulation curve when drawing this pole and being in the natural bow state.Again this pole is revolved around the centre of form and turn 90 degrees, it is held fixing 50mm length part and still is the level of state, its cantilever segment that stretches out platform still forms natural bow and keeps stationary state, measure the distance of each coordinate points successively to the horizontal linear intersection point, according to the data that record, on coordinate diagram, draw the position of each coordinate points, and with these coordinate points smooth connection successively, be depicted in 90 poles when spending and be in another actual measurement simulation curve (as shown in Figure 2) under the natural bow state.Then, with this magnesium alloy pole survey and draw the actual measurement simulation curve of two different angles compare, two originating points that curve can not coincide mutually are pole and position crooked, that reverse or exist the internal stress inequality occurs.According to the information that obtains by contrast, illustrate that this pole need correct by tension straingtening.
This pole is heated under 180 ℃, and the extensibility with 1% carries out tension straingtening.After the tension straingtening, adopt said method to survey and draw out pole at rotation 0 degree with revolve two actual measurement simulation curves that are under the natural bow state when turning 90 degrees once more, and these two curves are compared, though it is more approaching to obtain two curves, but also there is the phenomenon that to coincide mutually, the originating point that it can not coincide mutually, be pole crooked through still existing after the current tension straingtening, reverse or the position (as shown in Figure 3) of internal stress inequality, the tension straingtening technology that also need adjust this pole is described.
Again this pole is heated under 180 ℃, carries out tension straingtening with 1% extensibility again, even the pole before the tension straingtening under 180 ℃ of heating-up temperatures, adopts 2% extensibility to carry out tension straingtening.After the tension straingtening, adopt said method to survey and draw out pole at rotation 0 degree with revolve two actual measurement simulation curves that are under the natural bow state when turning 90 degrees once more, and these two curves are compared, this moment, two simulation curves coincide (as shown in Figure 4) substantially, the tension straingtening flatness of assert this magnesium alloy pole thus is better, meet the requirements, align successfully.So just can formulate diameter with 180 ℃ of heating-up temperatures, 2% extensibility is the tension straingtening technology of the AZ31 magnesium alloy pole of 16mm.
The present invention not only is confined to the foregoing description, is after asymmetrical magnesium alloy profiles adopts said method to survey and draw out article one actual measurement simulation curve for section configuration, this section bar is rotated 45~90 ° around the centre of form survey and draw out second actual measurement simulation curve.Be the actual measurement simulation curve of two different angles recording of asymmetrical magnesium alloy profiles then with section configuration, the theoretical curve that is calculated according to specific centre of form equatorial moment of inertia that has with angle position separately compares respectively respectively, the originating point that two curves that contrasted can not coincide mutually is section bar and position crooked, that reverse or exist the internal stress skewness occurs, adjusts tension straingtening technology thus.If the curve that is contrasted coincide mutually then judges that the flatness of section bar tension straingtening meets the requirements.
The set horizontal linear of the present invention also can be set in the top that magnesium alloy profiles stretches out the cantilever segment of platform, draws at support or wallboard near measured section bar.This set generally is used for the detection of short section bar of amount of deflection.
Adopt the flatness after said method is measured magnesium alloy profiles tension straingtening, detected section bar is existed reverse, the phenomenon of bending or internal stress uneven distribution can both reflect completely, the true flatness that can trulyr reflect detected magnesium alloy profiles, the information that detection is obtained is accurate more, comprehensive, and the engineering application facet such as optimization that help extensibility in magnesium alloy profiles tension straingtening technology play a role.The present invention also can detect the shape bending curve by automatic detection system, and draws the simulation curve of actual measurement, to raise the efficiency and accuracy; Also can pass through the computer model recognition technology to curve comparative analysis aspect, and set up various shape bending character shape datas storehouse,, raise the efficiency to obtain abundanter information.