CN104535410A - Temperature compensation method used for compact tension sample high temperature crack expansion test - Google Patents

Abstract

The present invention relates to a temperature compensation method used for compact tension sample high temperature crack expansion tests, sample width surfaces (2) on both sides of notches (1) of a test sample (12) and a reference sample (11) are respectively marked with current input solder joint positions (3), sample thickness surfaces (4) on both sides of opening ends of the notches (1) of the test sample (12) and the reference sample (11) are respectively marked with voltage output solder joint positions (5), four connection wires (7) at the current input solder joint positions (3) of the test sample (12) and the reference sample (11) are connected in series and connected with a DC power supply (8), every two wires (7) at the voltage output solder joint positions (5) of the test sample (12) and the reference sample (11) are connected with a signal amplifier (9), the signal amplifier (9) is connected with a computer (10), the test sample (12) and the reference sample (11) are put into a furnace and heated to test temperature, voltage time-varying curve are respectively drawn by use of voltage values during the test process of the test sample (12) and the reference sample (11), and finally a corresponding crack length a can be calculated by a voltage value.

Description

A kind of temperature compensation for compact tensile specimen heat cracking expanding test

Technical field

The present invention is a kind of temperature compensation for compact tensile specimen heat cracking expanding test, belongs to field of measuring technique.

Background technology

In crack Propagation research, the measurement of crack length is the gordian technique obtaining Crack Extension performance data.Observing crack length at low temperatures is at present directly pass through microscope.And materials for aeroengines main, a large amount of tests carries out under the high temperature conditions, at high temperature, specimen surface oxidation, blackening, crack length cannot use visual method to observe.Specimen surface oxidation, blackening crack length measure current in standard test method (as Unite States Standard (USS) ASTM E647-08, air standard HB 7680-2000), the automatic test approach of regulation Crack Extension has dc-bit method, and obtain application in reality test, the method has good stability.The method can converse into crack length based on the magnitude of voltage measured, and computation process completes by the order of formula (1) ~ (3):

$X=\ln [\left(\frac{e^{\frac{\mathrm{\πY}}{4W}}+e^{-\frac{\mathrm{\πY}}{4W}}}{2\cos \left(\frac{\mathrm{\π}{a}_0}{2W}\right)}\right)+\sqrt{{\left(\frac{e^{\frac{\mathrm{\πY}}{4W}}+e^{-\frac{\mathrm{\πY}}{2W}}}{2\cos \left(\frac{\mathrm{\π}{a}_0}{2W}\right)}\right)}^2-1}]...\left(1\right)$

$Z=\frac{e^{\frac{\mathrm{\πY}}{e^{4W}}}+e^{-\frac{\mathrm{\πY}}{4W}}}{e^{(u-X)}+e^{-(u-X)}}...\left(2\right)$

In formula: W specimen width, a0 initial crack length, a _{potential method}crack length, Y voltage measurement end distance, U magnitude of voltage.

But under hot conditions, be subject to the impact of measurement mechanism and measured material high temperature deformation, the accuracy of these methods decreases compared with room temperature, the high-strength material that particularly those resistivity are lower.

In the case of a high temperature, the change of sample material self may cause surveyed crack tip voltage to change.Specimen temperature change makes materials conductive rate change, and causes current potential pressure on sample also to change.And dc-bit method in the past does not consider the impact of temperature on measurement result, the magnitude of voltage measured on sample comprises the magnitude of voltage of crack length generation and the magnitude of voltage of temperature variation generation, and measurement result is inaccurate.

Summary of the invention

The present invention designs for above-mentioned the deficiencies in the prior art just and provides a kind of temperature compensation for compact tensile specimen heat cracking expanding test, its objective is Measurement accuracy nickel-base high-temperature alloy material crack length at high temperature, the method use reference coupon (11), under itself and test sample (12) are placed on same environment temperature, eliminate the impact of temperature on test sample (12) measurement result according to the magnitude of voltage of witness mark sample (11).

The object of the invention is to be achieved through the following technical solutions:

This kind, for the temperature compensation of compact tensile specimen heat cracking expanding test, is characterized in that: the step of the method is:

Step one, with reference to the requirement of navigation mark HB7680-2000, process two identical compact tensile specimen, the material of this sample is nickel base superalloy, one of them sample is reference coupon (11), another sample is test sample (12), the upper each mark in the specimen width face (2) of otch (1) both sides of test sample (12) and reference coupon (11) electric current input bond pad locations (3), this electric current input bond pad locations (3) is in the center of specimen width W and sample thickness B, in the sample thickness face (4) of the openend both sides of the otch (1) of test sample (12) and reference coupon (11), upper each mark voltage exports bond pad locations (5), this voltage export bond pad locations (5) be in sample thickness B center and distance open center line (6) 0.35 times of specimen width W positions on,

Step 2, by the mode of spot welding, wire (7) is connected with above-mentioned solder joint, test sample (12) is connected wire (7) series connection with four on electric current input bond pad locations (3) of reference coupon (11), the two ends of series connection connect direct supply (8), each two wires (7) that the voltage of test sample (12) exports in bond pad locations (5) are connected with signal amplifier (9), equally, each two wires (7) that the voltage of reference coupon (11) exports in bond pad locations (5) are also connected with signal amplifier (9), signal amplifier (9) is connected with computing machine (10),

Step 3, test sample (12) and reference coupon (11) are put into stove, wherein, test sample (12) is connected with test fixture, test sample (12) and reference coupon (11) are warming up to test temperature with stove, test temperature scope is 300 DEG C ~ 900 DEG C, insulation 30min ~ 60min, computing machine (10) records the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11) respectively;

Step 4, draw the voltage change curve in time of test sample (12) and reference coupon (11) respectively with the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11), then magnitude of voltage corresponding on two curves is subtracted each other, obtain the time dependent fair curve of voltage of test sample (12), calculate corresponding crack length a finally by magnitude of voltage.

In high temperature environments, nickel-base high-temperature alloy material demonstrates conductance in time, temperature and the phenomenon changed, such as, test temperature changes 1 DEG C, the change of materials conductive rate can cause the change of a few μ V of voltage signal, in order to eliminate these impacts, technical solution of the present invention has carried out large quantity research and test, the technical scheme wherein can selected comprises being used on sample selects a reference position, using the magnitude of voltage on reference position as reference voltage value, eliminate material and instrument change measures the impact of length to crackle, another sample can also be used in same environment as reference sample (11), the voltage change curve in time of test sample (12) is revised by reference to the magnitude of voltage on sample (11), obtain corresponding crack length accurately.How to select on sample in the process of a reference position in research, due to the magnitude of voltage of this position can not be got rid of not by the impact that crack length increases, so, the Research Thinking of technical solution of the present invention finally determines that the sample use two pieces is identical is placed in same experimental enviroment, wherein one piece of conduct is with reference to sample (11), and another block is test sample (12).

Accompanying drawing explanation

Fig. 1 is shape and the structure three-view diagram of test sample (12) and reference coupon (11) in technical solution of the present invention

Fig. 2 is the test principle figure of technical solution of the present invention

Curve I, II, III in Fig. 3 is respectively test sample (12), the time dependent curve of voltage of reference coupon (11) and the time dependent fair curve of voltage of test sample (12)

Embodiment

Below with reference to drawings and Examples, technical solution of the present invention is further described:

Shown in accompanying drawing 1 ~ 3, the step of the temperature compensation for compact tensile specimen heat cracking expanding test described in technical solution of the present invention is:

Step one, with reference to the requirement of navigation mark HB7680-2000, process two identical compact tensile specimen, the material trademark of this sample is the nickel base superalloy of GH4169G, one of them sample is reference coupon (11), another sample is test sample (12), described specimen width W is 40mm, sample thickness B is 10mm, the upper each mark in the specimen width face (2) of otch (1) both sides of test sample (12) and reference coupon (11) electric current input bond pad locations (3), this electric current input bond pad locations (3) is in the center of specimen width W and sample thickness B, namely this electric current input bond pad locations (3) is respectively 20mm apart from the edge of specimen width face (2), 5mm, in the sample thickness face (4) of the openend both sides of the otch (1) of test sample (12) and reference coupon (11), upper each mark voltage exports bond pad locations (5), this voltage export bond pad locations (5) be in sample thickness B center and distance open center line (6) 0.35 times of specimen width W positions on, namely this voltage output bond pad locations (5) is respectively 7mm apart from the edge of sample thickness face (4), 5mm,

Step 2, by the mode of spot welding, wire (7) is connected with above-mentioned solder joint, test sample (12) is connected wire (7) series connection with four on electric current input bond pad locations (3) of reference coupon (11), the two ends of series connection connect direct supply (8), the constant current source of this direct supply (8) to be electric current setting range be 1A ~ 50A, each two wires (7) that the voltage of test sample (12) exports in bond pad locations (5) are connected with signal amplifier (9), equally, each two wires (7) that the voltage of reference coupon (11) exports in bond pad locations (5) are also connected with signal amplifier (9), signal amplifier (9) is connected with computing machine (10),

Above-mentioned wire (7) and solder joint adopt spot welding to be connected, the mode of spot welding is compared with the mode of melting welding, and bond pad locations is more accurate, can not produce high temperature during welding, avoid the impact on material behavior, because whether accurate bond pad locations is very large on test findings impact;

Described signal amplifier (9) is simple two-way signal amplifier, and for the voltage signal on scale-up sample (12) and reference coupon (11), and give send this signal transmission into computing machine, computing machine carries out data processing;

Step 3, test sample (12) and reference coupon (11) are put into stove, wherein, test sample (12) is connected with test fixture, test sample (12) and reference coupon (11) are warming up to test temperature with stove, test temperature is 650 DEG C, insulation 30min ~ 60min, computing machine (10) records the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11) respectively;

Step 4, draw the voltage change curve in time of test sample (12) and reference coupon (11) respectively with the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11), then magnitude of voltage corresponding on two curves is subtracted each other, obtain the time dependent fair curve of voltage of test sample (12), calculate corresponding crack length a finally by magnitude of voltage.

Technical solution of the present invention compared with prior art have employed the method for temperature compensation, overcomes measurement result fluctuation and the low shortcoming of the measuring accuracy that causes.

Claims (1)

1. for a temperature compensation for compact tensile specimen heat cracking expanding test, it is characterized in that: the step of the method is:

Step one, with reference to the requirement of navigation mark HB7680-2000, process two identical compact tensile specimen, the material of this sample is nickel base superalloy, one of them sample is reference coupon (11), another sample is test sample (12), the upper each mark in the specimen width face (2) of otch (1) both sides of test sample (12) and reference coupon (11) electric current input bond pad locations (3), this electric current input bond pad locations (3) is in the center of specimen width W and sample thickness B, in the sample thickness face (4) of the openend both sides of the otch (1) of test sample (12) and reference coupon (11), upper each mark voltage exports bond pad locations (5), this voltage export bond pad locations (5) be in sample thickness B center and distance open center line (6) 0.35 times of specimen width W positions on,

Step 2, by the mode of spot welding, wire (7) is connected with above-mentioned solder joint, test sample (12) is connected wire (7) series connection with four on electric current input bond pad locations (3) of reference coupon (11), the two ends of series connection connect direct supply (8), each two wires (7) that the voltage of test sample (12) exports in bond pad locations (5) are connected with signal amplifier (9), equally, each two wires (7) that the voltage of reference coupon (11) exports in bond pad locations (5) are also connected with signal amplifier (9), signal amplifier (9) is connected with computing machine (10),

Step 3, test sample (12) and reference coupon (11) are put into stove, wherein, test sample (12) is connected with test fixture, test sample (12) and reference coupon (11) are warming up to test temperature with stove, test temperature scope is 300 DEG C ~ 900 DEG C, insulation 30min ~ 60min, computing machine (10) records the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11) respectively;

Step 4, draw the voltage change curve in time of test sample (12) and reference coupon (11) respectively with the magnitude of voltage in the process of the test of test sample (12) and reference coupon (11), then magnitude of voltage corresponding on two curves is subtracted each other, obtain the time dependent fair curve of voltage of test sample (12), calculate corresponding crack length a finally by magnitude of voltage.