CN102269677A - Treatment method for abnormal value of plastic strain ratio r value - Google Patents

Abstract

The invention discloses a treatment method for an abnormal value of a plastic strain ratio r value. A test curve with abnormal value generating is treated by using the following method: 1) establishing a straight line equation for the last linear phase of the test curve with abnormal test results, wherein the straight line equation is y=ax+c; 2) obtaining the intersection of the equation y=ax+c and the equation x=o; 3) adopting the intersection of the two equations as a new origin of the coordinate to calculate the actual sample width after the sample is elongated and deformed, then recalculating the r value, and removing the influence due to the mutation parts of the curve to obtain the relatively accurate r value. According to the present invention, the straight line equation for the last linear phase of the test curve with the abnormal test results is established, and the new origin of the coordinate is established, the actual sample width is calculated after the sample is elongated and deformed, the actual sample width is substituted in the formula of the r value to recalculate the r value, and the influence due to the vertical phase and the broken line phase is removed so as to obtain the exact r value, such that the method is convenient to be performed, the result is exact, the repeated test is not required so as to save manpower, resource and time.

Description

The disposal route of plastic strain ratio r value exceptional value

Technical field

The invention belongs to the mechanical test field, the method for testing of plastic strain ratio r value particularly specifically relates to a kind of disposal route of plastic strain ratio r value exceptional value.

Background technology

Plastic strain ratio r value is one of important parameter of estimating sheet metal deep rolling performance, and it has reflected thin plate in its plane, when bearing pulling force or pressure, and the ability of opposing attenuation or thickening.At present the test method that extensively adopts in iron and steel enterprise be with sheet metal sample uniaxial tension when producing uniform plastic deformation, the logarithmic strain of sample regulation gauge length insied width direction and the logarithmic strain ratio of thickness direction.

Most materials are from homogeneous strain, and in the range of strain of correspondence, the r value remains unchanged substantially during to maximum load, but since the anisotropic of material, sampling direction difference, and the r value that records generally has difference.Generally, the sampling direction is divided into 0 °, 45 °, 90 °, so each test sample quantity is very big.But fast development along with modern automatic test technology, can realize that automatic control, automatic data processing, high-resolution electronic tensile test machine are widely used in field tests, not only improved efficient, and reduced in the process of the test human factor the influence of test findings.Generally speaking, every properties data that testing machine is tested automatically is true, accurate, but under a few cases, (as sample through hot simulation, specimen surface has the subtle oxide film of one deck, if remove oxide film artificially, it is rough and uneven in surface that specimen surface is occurred, and it is unusual that test findings is occurred.) exceptional value can appear, and deviation is very big, differs several times sometimes.Before the disposal route that does not find r value exceptional value, can only pick out exceptional value, thereby influence result's accuracy, because generally be to adopt several sample testing results' mean value to determine the value of the plastic strain ratio of this product; If have only one or two samples, when the result is exceptional value, need great amount of manpower and material resources and time have been wasted, so be necessary to propose a kind of disposal route to r value exceptional value result from new sampling, processing and test.

Also not about adopting electronic tensile test machine test plastic strain ratio r value the report of the disposal route of exceptional value to occur, the error analysis of measuring the r value is arranged about the relevant report of testing plastic strain ratio at present; There is the result who adopts different method of testings to compare, the influence of the selection of analytical test condition to the r value arranged, the influence of the texture of analysis of material to the r value arranged, therefore, find out a kind of disposal route and have practical significance r value exceptional value result.

Summary of the invention

The present invention proposes a kind of about using electronic tensile test machine test r value the disposal route of exceptional value to occur, when exceptional value occurring with solution, needs repeated test, thereby causes the problems such as waste of aspects such as manpower, resource, time.

The technical solution adopted for the present invention to solve the technical problems is: 1.. the last linear stage that the trial curve of exceptional value test findings occurred is set up straight-line equation, is made as y=ax+c; (get test test two point value on the curve) finds the solution a, c value in this equation; 2. ask the intersection point of y=ax+c and x=0 equation; 3. with the intersection point of two equations as new true origin, calculate the actual samples width after the sample stretcher strain, recomputate r value, remove curve sudden change influence partly, draw relatively accurate r value.

The present invention is by setting up straight-line equation y=ax+c to the linear segment of trial curve final stage, and find the solution the intersection point of this equation and x=0 equation, this intersection point as new true origin, is calculated the developed width after the sample drawn is out of shape, the computing formula of substitution r value, the r value is recomputated, remove the vertical stage of curve and the influence in broken line stage, can obtain objective, correct r value, it is accurately convenient, need not repeated test, thus save manpower, resource, time.

Description of drawings

Trial curve under Fig. 1 r value normal condition

The trial curve of Fig. 2 sample of the present invention

The trial curve Width strain figure enlarged drawing of Fig. 3 sample of the present invention

The trial curve Width strain figure partial enlarged drawing of Fig. 4 sample of the present invention

Specific embodiment

Below in conjunction with accompanying drawing specific embodiments of the invention are elaborated

1. the trial curve under the normal condition, the change curve of Width is near linear, shown in Fig. 1 center line 11.Tangible flex point has then appearred in the tension test curve that exceptional value appears in the r value, is vertical uplift stage in short-term during beginning, and the broken line of being made up of a plurality of flex points is near linear straight line, shown in Fig. 2 center line 21 at last then.

2. analyze the trial curve that produces exceptional value.

Produce the trial curve of exceptional value, though the stage of vertical uplift in short-term during beginning is linear, this stage strain occurs in the very small scope, does not reach the strain of testing requirements, therefore can not adopt this linearity range to calculate the r value; The final stage of trial curve is also linear, and has reached 10% strain requirement, and therefore, available this linearity range calculates the r value, this step-by-step test curve is made as linear equation: y=ax+c.

3. bring the coordinate and the last linear stage of near any point the asking strain point into above-mentioned equation near the coordinate of any point of broken line part, can obtain the value of a, c, bring a, c value into equation y=ax+c, find the solution the intersection point of this equation and x=0 equation then.

With institute's find intersection as new true origin, calculate the actual samples width after the sample stretcher strain, bring the computing formula of r value into, from new calculating r value, the influence in removal vertical stage of curve and broken line stage can obtain objective, correct r value.

Below in conjunction with embodiment the present invention is further described.Referring to Fig. 1 (trial curve under the r value normal condition), Fig. 2 (trial curve of exceptional value appears in the r value), Fig. 3 (trial curve Width strain figure enlarged drawing), Fig. 4 (trial curve Width strain figure partial enlarged drawing), table 1 (test findings that testing machine records automatically), table 2 (treated test findings) and table 3 (test findings that the spare test piece testing machine records automatically).

1. get several groups of samples, process a plurality of tensile samples for every group.The sample of r value exceptional value occurs for test findings, do tension test again with spare test piece, whether correct in order to the comparison correction result.Test findings sees the following form.

The test findings that table 1. sample initial parameter and testing machine are measured automatically

Result after table 2.r value recomputates

The test findings that table 3. spare test piece testing machine records automatically

As can be seen from Table 1, in No. 1 sample, the r value of 1-1 sample is 2.3 times of 1-2 sample r value; In No. 3 samples, the r value of 3-1 sample is 2.7 times of 3-2 sample r value; Table 2 is the test findings that calculate after treatment.

2. as can be seen from Figure 1, under the normal condition, the strain curve of Width has good linearity; From Fig. 2, Fig. 3 (trial curve Width strain figure enlarged drawing) and Fig. 4 (trial curve Width strain figure partial enlarged drawing) as can be seen, when the appearance of r value is unusual, sudden change has appearred in the strain curve of Width, be vertical uplift stage in short-term during beginning, the broken line of forming by a plurality of flex points then, be near linear straight line at last,, cause the r value unusual just because of the existence in vertical uplift stage and broken line stage in short-term.

3. the trial curve Fig. 2 with specimen coding 1-1 is an example, and in its enlarged drawing (Fig. 3 trial curve Width strain figure enlarged drawing), the final stage of curve is linear, this linear segment is set up straight-line equation: y=ax+c.

In the end on the linearity range (Fig. 3) find out near the strain point of asking arbitrarily the coordinate of any as (9.995,0.72), the coordinate of getting any point, close broken line place on the later linearity range of broken line again is as (2.128,0.3267), bring above-mentioned equation into, can obtain the value of a, c, be respectively: (a=0.05, c=0.22), bring a, c value into the y=ax+c equation, ask the intersection point of this equation and x=0 equation, get y=0.22, promptly obtain an intersecting point coordinate: (0,0.22), with this intersection point as new true origin.

5. be reference with new origin, calculate the developed width after the sample drawn is out of shape, the computing formula of substitution r value:

(in the formula: b ₀---sample original width, b ₁--specimen width after the-stretcher strain, L ₀--the original gauge length of-sample, L ₁--sample marking distance after the-stretcher strain).

The specimen width changing value deducts the Y coordinate figure of new coordinate origin after the stretcher strain of representing with former coordinate system, promptly can obtain the real change value of specimen width direction, that is: (0.72-0.22), then sample developed width b after the stretcher strain ₁=12.69-(0.72-0.22); It is 10% strain that sample is asked, sample marking distance L after the stretcher strain ₁=L ₀+ L ₀* 10%=50+50 * 10%; All the other each parameter constants, substitution r value computing formula gets:

$r=\frac{\ln \left(\frac{b_0}{b_1}\right)}{\ln \left(\frac{b_1\×L_1}{b_0\×L_0}\right)}=\frac{\ln \left(\frac{12.69}{12.69-(0.72-0.22)}\right)}{\ln \left(\frac{(12.69-(0.72-0.22))\×(50+50\×10\%)}{12.69\×50}\right)}=0.7294$

This correction result and the normal 1-2 sample of trial curve r value are contrasted, and compare with the result of table 3 spare test piece, this result is objective, correct r value as can be seen.

Employing is recomputated the 3-1 trial curve with quadrat method, and the r value that gets the 3-1 sample is: r=0.5659, compare with the r value of 3-2 sample and the result of table 3 spare test piece r value, and this result is objective, real r value as can be seen.

Claims (2)

1. the disposal route of a plastic strain ratio r value exceptional value is characterized in that, adopts following method to handle for the trial curve that produces exceptional value:

1) the last linear stage that the trial curve of exceptional value is appearred in test findings is set up straight-line equation, is made as y=ax+c; Test by getting and to test two point value on the curve, find the solution a, c value in this equation;

The slope of the last linear stage of curve when a is r value exceptional value, the sudden change value when c is r value exceptional value;

2) ask the intersection point of y=ax+c and x=0 equation;

3) with the intersection point of two equations as new true origin, calculate the actual samples width after the sample stretcher strain, recomputate r value, remove curve sudden change influence partly, draw correct r value.

2. the disposal route of a kind of plastic strain ratio r value exceptional value according to claim 1 is characterized in that, described r value computing formula is:

$r=\frac{\ln \left(\frac{b_0}{b_1}\right)}{\ln \left(\frac{b_1\×L_1}{b_0\×L_0}\right)}$

In the formula: b ₀---sample original width, b ₁--specimen width after the-stretcher strain, L ₀--the original gauge length of-sample, L ₁--sample marking distance after the-stretcher strain.

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