CN110736577A - method for measuring surface stress distribution rule of marine diesel engine body - Google Patents
method for measuring surface stress distribution rule of marine diesel engine body Download PDFInfo
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- CN110736577A CN110736577A CN201911015033.2A CN201911015033A CN110736577A CN 110736577 A CN110736577 A CN 110736577A CN 201911015033 A CN201911015033 A CN 201911015033A CN 110736577 A CN110736577 A CN 110736577A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/0047—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes measuring forces due to residual stresses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/16—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force
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Abstract
The invention discloses a method for measuring the distribution law of surface stress of a marine diesel engine body, which comprises the steps of 1, adhering a special foil type strain flower on the surface of a workpiece to be measured, 2, connecting each strain sheet of the strain flower to a stress measuring instrument and adjusting zero, 3, installing and fixing a drilling tool on the workpiece to align with the center of the strain flower, 4, drilling a hole to be measured on the surface of the diesel engine body, 5, reading the strain released by the hole, 6, calculating residual stress, 7, measuring three groups of experimental data of the diesel engine body, 8, obtaining the distribution situations of the residual stress of three different parts according to the three groups of measured experimental data, 9, comparing simulation data results obtained by using finite element software Abaqus, and 10, obtaining the distribution law of the stress of the diesel engine body.
Description
Technical Field
The invention relates to the technical processing field, in particular to methods for measuring the surface stress distribution law of a marine diesel engine body.
Background
The marine diesel engine body is which is a key part of a diesel engine, belongs to a frame thin-wall part, has large size and complex structure, and is easy to deform during and after processing, various marine diesel engine bodies generate macroscopic residual stress during casting, and are continuously developed into a complex distribution state in a subsequent heat treatment link, common heat treatment process is used for reducing and homogenizing the internal stress of a workpiece blank, but the internal stress can not be completely eliminated, in the actual production, the thermal stress can be introduced due to the imperfect heat treatment process condition, and the subsequent processing deformation is caused by the influence of the step on the blank state, so that the distribution state of the residual stress of the engine body after heat treatment is very important to be completely cleared, and the failure of the engine body part due to the processing deformation caused by the redistribution of the residual stress in period after processing can be effectively controlled.
Disclosure of Invention
The invention aims to provide methods for measuring the surface stress distribution law of a marine diesel engine body, which can effectively measure the stress distribution law of the diesel engine body after annealing, effectively obtain the residual stress distribution law of the diesel engine body to provide reference for the processing of the following key procedures, and reduce the processing deformation of the diesel engine body caused by residual stress induced release.
The technical scheme is as follows: in order to achieve the purpose, the method for measuring the surface stress distribution law of the marine diesel engine body comprises the following steps:
step , taking the body of the diesel engine as a measuring object, and sticking the special foil type strain flower on the surface of the measured workpiece;
connecting each strain gauge of the strain gage to a stress measuring instrument and zeroing;
step three, mounting and fixing the drilling tool on the workpiece to align with the center of the strain rosette;
drilling a hole to be measured on the surface of the diesel engine body;
reading the strain of the three units released by the holes;
sixthly, calculating the residual stress of the surface of the machine body;
step seven, solving the maximum and minimum main stresses of the measured position, and measuring three groups of experimental data reflecting the stress state of the diesel engine body;
step eight, obtaining the residual stress distribution conditions of three different parts according to the three groups of measured experimental data;
step nine, comparing the experimental data obtained by measurement in the step eight with the simulation data result obtained by applying finite element software Abaqus;
step ten, obtaining the stress distribution rule of the diesel engine body.
, in the step , the strain rosette is adhered at the same position of a cylinder and a second cylinder, a fifth cylinder and a sixth cylinder, and a ninth cylinder and a tenth cylinder, wherein nine points are selected to be respectively adhered with the strain rosette and are respectively distributed on the surface of the cylinder cover, the side edge, the vicinity of the crank hole and the bottom surface.
And , polishing the measurement surface adhered with the strain rosette by using sand paper or abrasive cloth to remove rust, wherein the surface roughness reaches Ra3.2-6.4, and the area is not less than four times of the area of the strain rosette, dripping glue solution on the adhering surface of the strain rosette, aligning a No. strain gage to a reference shaft, and placing the strain rosette on the polished surface of the machine body.
, the step two is a concrete method:
, pulling up 6 leads of the strain rosette, and adhering an insulating tape at the bottom of the strain rosette to be connected with a strain rosette substrate;
and secondly, pasting an insulating tape on the wire grid part, and connecting a lead led out by the measuring strain gauge to a corresponding wiring end of the strain measuring instrument.
And , grinding the surface of the selected test point, and reaming by using a twist drill with the diameter of 1.5mm, wherein the depth of the small hole is equal to or slightly larger than the diameter of the small hole and is 1.2 times of the diameter of the small hole.
, testing the strain release coefficients epsilon in three directions by using a strain gauge after the strain release is complete1、ε2、ε3Substituting into the residual stress calculation formula to obtain the maximum and minimum principal stress sigma of the detected position1、σ2And a principal stress angle theta.
, comparing the 3 groups of residual stress experimental data with simulation data obtained by finite element software Abaqus according to the 3 groups of experimental data of the residual stress of the surface of the fuselage obtained in the step six, and obtaining the distribution state of the residual stress of the surface of the fuselage.
The method for measuring the surface stress distribution rule of the marine diesel engine body has the advantages that the method for measuring the surface stress distribution rule of the marine diesel engine body can effectively measure the stress distribution rule of the body of the diesel engine body after annealing, can avoid the problem that the subsequent processing is influenced by the existence of the residual stress on the surface of the body after the diesel engine is subjected to a heat treatment process in the prior art, effectively obtains the residual stress distribution rule of the body to provide reference for the processing of the following key process, and reduces the processing deformation failure of the diesel engine body caused by the induced release of the residual stress.
Drawings
FIG. 1(1) is a trend chart of test point experimental data among cylinder holes of a machine body (1-2);
FIG. 1(2) is a data trend chart of simulation results between cylinder holes of the machine body (1-2);
FIG. 2(1) is a trend chart of test point experimental data among cylinder holes of the machine body (5-6);
FIG. 2(2) is a data trend chart of simulation results between cylinder holes of the machine body (5-6);
FIG. 3(1) is a trend chart of test point experimental data between cylinder holes of the machine body (9-10);
FIG. 3(2) is a data trend chart of simulation results between cylinder holes of the machine body (9-10);
FIG. 4 is a schematic view of a three-dimensional model of a fuselage;
FIG. 5 is a diagram of the distribution of the cylinder bore surface and side test points of the fuselage;
FIG. 6 is a profile of a test point for the bottom surface of the fuselage and a crankshaft hole;
FIG. 7 is a flow chart of a measurement method of the present invention.
Detailed Description
The technical solution of the present invention is further explained in with reference to the drawings.
In this embodiment, the method for measuring the surface stress distribution law of the body of the marine diesel engine includes the following steps:
step , taking the body of the diesel engine as a measuring object, and sticking the special foil type strain flower on the surface of the measured workpiece, wherein the method comprises the following steps:
, selecting a MTU diesel engine body as a selected test object, wherein the MTU diesel engine body is made of QT500-7, selecting 3 groups of 27 test points on the surface of the diesel engine body, wherein the 27 test points comprise the upper surface of a cylinder hole, the vicinity of the side edge of the diesel engine body, a crankshaft hole accessory and the bottom of the diesel engine body, and the selected test points are respectively located at the parts closing position of the diesel engine body;
secondly, grinding the selected test points by using a grinding wheel or abrasive cloth with the granularity of 60 meshes to ensure that the surface roughness Ra3.26.4 and the area are not less than four times of the area of the strain flower, and wiping the adhered surface by using cotton balls or gauze for multiple times until no stain exists;
and step two, connecting each strain gage of the strain gage to a stress measuring instrument and zeroing, wherein the specific method comprises the following steps:
, lightly pulling up 6 leads of the strain rosette, adhering a polyester insulating tape at the bottom of the strain rosette to be connected with the strain rosette substrate to prevent the strain rosette lead from contacting the metal surface, covering a wire grid part, small insulating tapes, covering a leading-out wire on a part, preventing scrap iron from damaging the strain rosette wire grid or causing short circuit when drilling holes, reinforcing the leading-out wire from being pulled apart on the aspect of , adhering a wiring terminal to a strain rosette accessory by 502 glue, welding the strain rosette lead with a terminal by using a 20-30W electric iron, and welding the terminal with a lead;
secondly, connecting a lead led out by the strain gauge to a corresponding binding post of the stress measuring instrument, and connecting a lead led out by the compensation gauge to the binding post;
step three, the drilling tool is installed and fixed on the workpiece and is aligned with the center of the strain rosette, and the specific method comprises the following steps:
, adjusting the height of the drilling tool in advance, keeping the drill rod vertical to the surface of the machine body to be measured, enabling the drilling tool to be more stable as the height is lower, coating a little 502 glue at the gap between the fixed foot of the drilling tool and the contact surface of the workpiece, waiting for about 3 minutes, and blowing hot air by using a blower to accelerate curing;
and secondly, after curing, tightening a locking cap on the fixing foot to fix the drilling tool on the surface of the workpiece, loosening a locking gland, and finely adjusting 4 centering adjusting screws to ensure that the center of the cross line of the magnifier is superposed with the center mark of the strain flower as much as possible. After centering, the gland is locked, and then the stress measuring instrument is zeroed;
drilling a hole to be measured on the surface of the diesel engine body, wherein the specific method comprises the following steps:
, the appearance of the body of the marine diesel engine is Y-shaped, so that the reasonable selection of the test points is carried out according to the appearance characteristics of the diesel engine, and the reasonable selection of the test points is crucial to the accuracy of the stress distribution rule of the body of the diesel engine;
secondly, according to the selected test point, the surface of the selected test point is polished, a twist drill with the diameter of 1.5mm is used for reaming, the depth of the small hole is the same as or slightly larger than the diameter of the small hole, and the depth is 1.2 times of the aperture;
step five, three unit strains epsilon released by reading holes1、ε2、ε3；
Step six, calculating the residual stress of the surface of the fuselage according to a formula, wherein the specific method comprises the following steps:
the sticking strain gauges were 0 °, 90 °, and 225 °, respectively. The sensitivity coefficient of the adhered strain flower is 2.180, and the small hole is released; reading out the strain relief factor epsilon in three different directions displayed on a computer1、ε2、ε3The maximum and minimum principal stress sigma of the detected position can be obtained according to a residual stress calculation formula1、σ2And a principal stress angle θ;
the residual stress formula is:
in the formula:
ε1、ε2、ε3-the strain relief of the strain in three cells, in mu epsilon;
σ1、σ2-maximum residual stress, minimum principal stress, in MPa;
e——σ1and epsilon1Angle of direction, clockwise orientation, if ε3≥ε1，θ＝θ，ε3＜ε1，θ＝θ+90°；
E is the compressive modulus of elasticity 168Gpa of the nodular cast iron, and A, B is the release coefficient (A is-0.0415, B is-0.0778).
Measuring three groups of experimental data by the diesel engine body;
, according to the calculation formulas of the strain release and the residual stress in the three directions measured in the step six, the maximum and minimum principal stresses of the measured position are obtained, and the stress state of the diesel engine body is analyzed, as shown in fig. 1-3, wherein the residual stress of the body test area mainly takes the compressive stress as the principal, the residual stress mainly keeps about 100Mpa, and the tensile stress of the residual stress mainly takes 80 Mpa.
Analyzing the residual stress distribution conditions of three different parts according to the three groups of measured experimental data;
, the nine test points selected in figure 1 are located between the No. 1-2 cylinder holes of the diesel engine, the measured experimental data can show that the surface residual stress of the test points (1, 2, 3) on the cylinder hole surface is small, the surface residual stress of the test points (4, 5, 6) on the side edge of the engine body is maximum, the maximum value of the compressive stress can reach about 150Mpa, the surface residual stress value of the test points (7, 8) on the bottom of the engine body is about 100Mpa, and the surface residual stress of the test point (9) on the crankshaft hole is about 80 Mpa.
And secondly, nine test points selected in the graph 2 are positioned between No. 5-6 cylinder holes of the diesel engine, the measured experimental data can show that the surface residual stress of the test points (1, 2 and 3) on the cylinder hole surface is 50-100 Mpa, the surface residual tensile stress and the surface residual compressive stress of the test points (4, 5 and 6) on the side edge of the engine body have larger difference, the surface residual stress value of the test points (7 and 8) on the bottom of the engine body is smaller, and the surface residual stress of the test point (9) on the crankshaft hole is about 60 Mpa.
Thirdly, nine test points selected in the graph 3 are located between the No. 9-10 cylinder holes of the diesel engine, the measured experimental data can show that the surface residual stress of the test points (1, 2 and 3) on the cylinder hole surface is lower than 50Mpa, the difference between the measured residual tensile stress and the measured residual compressive stress of the 2 points is large, the surface residual of the test points (4, 5 and 6) on the side edge of the engine body is 50-150 Mpa, the surface residual stress value of the test points (7 and 8) on the bottom of the engine body is small, and the surface residual stress of the test point (9) on the crankshaft hole is about 60 Mpa.
Fourthly, the surface residual stress of different positions of the same diesel engine bodies is different from each other, mainly represented by the fact that the residual stress of the side face of the body is larger than the residual stress of the cylinder hole face and the bottom face of the body, the residual stress of the cylinder hole face of the body is larger than the residual stress near the crankshaft hole, the residual stress of the two sides is smaller than the residual stress of the middle of the body when viewed from the whole body, and the residual stress of the middle of the body is larger.
Step nine, carrying out comparative analysis on simulation data results obtained by using finite element software Abaqus, wherein the specific method comprises the following steps:
, analyzing the stress distribution result obtained by applying the finite element simulation Abaqus and the stress data measured by the experiment, thereby obtaining the distribution rule of the test stress result of different parts of the diesel engine body by analysis;
and secondly, taking out unit nodes at corresponding positions from the Abaqus simulation result, and deriving stress values of the unit nodes to compare with results measured by experiments.
Analyzing the stress distribution rule of the diesel engine body, such as data comparison of fig. 1-3;
it can be seen from the data results of the Abaqus simulation analysis and the data results of the experimental measurement that after the detected fuselage is subjected to the retrogradation treatment, the residual stress distribution of the fuselage test area is mainly based on the compressive stress, the residual stress is kept within 150MPa, the stress cloud chart of the whole fuselage and the stress distribution state of the fuselage basically measured by the experiment can be obtained from the Abaqus simulation, and the accuracy of the actual measurement result is verified.
Claims (7)
1, method for measuring the distribution rule of the surface stress of the marine diesel engine body, which is characterized by comprising the following steps:
step , taking the body of the diesel engine as a measuring object, and sticking the special foil type strain flower on the surface of the measured workpiece;
connecting each strain gauge of the strain gage to a stress measuring instrument and zeroing;
step three, mounting and fixing the drilling tool on the workpiece to align with the center of the strain rosette;
drilling a hole to be measured on the surface of the diesel engine body;
reading the strain of the three units released by the holes;
sixthly, calculating the residual stress of the surface of the machine body;
step seven, solving the maximum and minimum main stresses of the measured position, and measuring three groups of experimental data reflecting the stress state of the diesel engine body;
step eight, obtaining the residual stress distribution conditions of three different parts according to the three groups of measured experimental data;
step nine, comparing the experimental data obtained by measurement in the step eight with the simulation data result obtained by applying finite element software Abaqus;
step ten, obtaining the stress distribution rule of the diesel engine body.
2. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 1, wherein in the step , the strain rosette is adhered at the same position of # cylinder and second # cylinder, fifth cylinder and sixth cylinder, and ninth cylinder and tenth cylinder, wherein nine points are selected and respectively adhered with the strain rosette, and the nine points are respectively distributed on the surface of a cylinder cover, the side edge, the vicinity of a crank hole and the bottom surface.
3. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 2 is characterized in that a measuring surface adhered with strain rosettes is polished by sand paper or abrasive cloth to remove rust, the surface roughness reaches Ra3.2-6.4, the area is not less than four times of the area of the strain rosettes, glue is dripped on the adhering surface of the strain rosettes, and the strain rosettes are placed on the polished surface of the marine diesel engine body by aligning a No. strain gauge to a reference shaft.
4. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 1, wherein the method comprises the following steps: the second step is a specific method:
, pulling up 6 leads of the strain rosette, and adhering an insulating tape at the bottom of the strain rosette to be connected with a strain rosette substrate;
and secondly, pasting an insulating tape on the wire grid part, and connecting a lead led out by the measuring strain gauge to a corresponding wiring end of the strain measuring instrument.
5. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 1, wherein the method comprises the following steps: the fourth step is specifically as follows: and (3) polishing the surface of the selected test point, and reaming by using a twist drill with the diameter of 1.5mm, wherein the depth of the small hole is the same as or slightly larger than the diameter of the small hole, and is 1.2 times of the aperture.
6. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 1, wherein the method comprises the following steps: the sixth step is specifically as follows: when the strain is completely released, the strain release coefficients epsilon in three directions are tested by using a strain measuring instrument1、ε2、ε3Substituting into the residual stress calculation formula to obtain the maximum and minimum principal stress sigma of the detected position1、σ2And a principal stress angle theta.
7. The method for measuring the surface stress distribution law of the marine diesel engine body according to claim 1, wherein the method comprises the following steps: the seventh step is specifically as follows:
and comparing the 3 groups of residual stress experimental data with simulation data obtained by finite element software Abaqus according to the 3 groups of experimental data of the residual stress of the surface of the fuselage obtained in the step six to obtain the distribution state of the residual stress of the surface of the fuselage.
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Cited By (3)
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| CN112414936A (en) * | 2020-11-10 | 2021-02-26 | 山东大学 | Tunnel mechanical characteristic detection system and method |
| CN112484892A (en) * | 2020-12-02 | 2021-03-12 | 东莞材料基因高等理工研究院 | Method for improving residual stress precision of blind hole method measurement |
| CN112487715A (en) * | 2020-11-27 | 2021-03-12 | 江苏科技大学 | Method for optimizing reliability of process parameters of key hole system of marine diesel engine body |
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Application publication date: 20200131 |