JP2007118060A - Life evaluation method for insert die of casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a life evaluation method for water jacket insert die of an engine cylinder block casting mold, which can estimate a reliable fatigue life, by obtaining a stress value close to the stress condition incurred in the real insert die of water jacket using a low cost testing method. <P>SOLUTION: A test piece 20 is prepared which comprises a part of the water jacket insert die 10, including neighboring two arc sections 12, 12 forming an outer periphery of water jacket insert die and at least one connection point 11 joining the arc sections 12, 12 each other. Strain gages 23 are attached to both inner periphery side and outer periphery side respectively on the arc section 12 of the test piece 20 in the proximity of connection point 11. Then, cyclic loading tests are performed to detect either one or both of the stress incurred in the test piece or a crack incurred in the test piece, by imposing such a load on the test piece 20 that the connecting angle of the arc sections 12, 12 increases or decreases. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating the life of a water jacket insert of a cylinder block of an engine provided in a casting mold.

  When casting a cylinder block of an engine made of an aluminum alloy, a casting mold composed of a main mold, an insert, a core and the like is used. A water jacket (water cooling part) for cooling is formed in the cylinder block. The insert for forming the water jacket (water jacket insert) is one of cast mold parts that are prone to cracking and have a short life.

The occurrence of cracks in the water jacket insert is greatly influenced by the local shape factor of the water jacket insert.
As shown in FIG. 1, a water jacket insert of an engine cylinder block generally has a shape in which a plurality of cylinders are arranged in a partially overlapped state so that their axial directions are substantially parallel. It is. It is recognized that cracks Cr are particularly likely to occur in the water jacket insert 10 in the vicinity of a portion (connecting portion 11) connecting the circular arc portion 12 of the cylindrical body. A portion where the crack Cr is likely to occur and is located in the vicinity of the connecting portion 11 in the arc portion 12 is referred to as “crack frequent occurrence range 13”. For example, in the water jacket insert 10 shown in FIG. 1, there are two crack frequent occurrence regions 13 and 13 on both sides of the connecting portion 11 of the arc portions 12 and 12.

Nesting shape of casting mold is designed based on the shape of the cast product to be produced. To improve durability under severe usage conditions where high temperature heating and cooling are repeated, change the shape of the details and reinforce it. With regard to, design changes are repeated.
When preparing for production of a new product, the shape of the casting mold is the first item to be determined, and it is difficult to change the design after production has started. It is necessary to decide.

  Conventionally, in order to determine the shape of the insert, the entire casting mold is designed and prototyped depending on the past product and the designer's experience, and the actual life of the main mold and insert is increased by actually casting. Since this evaluation was made and this evaluation was reflected in the design, many trials and errors were repeated at the design stage, which required a lot of man-hours and a large amount of money.

  On the other hand, in recent years, computer systems (CAE systems) that support industrial product design and development processes are known. In the CAE system, it is possible to perform product design support, analysis to calculate characteristics such as strength and heat resistance using the model of the designed product, simulation to confirm the function and performance of the product, etc. This is expected to improve development speed and reduce costs.

It is known to use the CAE system in the design of casting molds. For example, the technique described in Patent Document 1 creates a numerical analysis model such as a main mold and a core of a casting mold based on a completed design drawing of a casting, and performs strain analysis or stress analysis by numerical analysis. A casting mold is prepared after evaluating cracks based on the analysis results.
Thereby, compared with the case where manufacture of a casting mold is actually repeated, the production cost and production time of a casting mold, and the waste of the manufacturing mold which is wasted can be reduced.
JP 2004-174512 A

  As described above, in the CAE system, it is possible to estimate the stress, but in order to perform the calculation after conditioning various factors, the calculated stress value and the stress value generated in the actual casting mold There may be errors in between.

In particular, in water jacket inserts, the places where fatigue failure occurs are almost limited, and if this characteristic is used, stress can be reduced more effectively and more effectively than when the prototype of the entire water jacket insert is repeated. You should be able to know the condition.
Therefore, in the present invention, a water jacket of a casting mold that can obtain a stress value closer to the stress state generated in an actual water jacket insert and can reliably estimate the fatigue life of the water jacket insert based on this stress value. We propose a life evaluation method for nesting.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, in claim 1, there is provided a life jacket nesting life evaluation method provided in a casting mold of a cylinder block of an engine, two adjacent arc portions forming the outer peripheral shape of the water jacket nesting, A test piece that forms a part of the water jacket nest including at least one connection part that connects the arc parts to each other. A strain gauge on each of the outer peripheral side, a load is applied to the test piece, and either a stress generated in the test piece or a crack generated in the test piece from the distortion of the arc portion measured by the strain gauge. A repeated load test is performed to detect either or both.

  According to a second aspect of the present invention, when a load is applied to the test piece, a load that increases, decreases, or increases or decreases the connection angle of the arc portion is applied to the front connection portion.

  According to a third aspect of the present invention, when applying a load to the test piece, a load is applied to the connecting portion from the inner peripheral side to the outer peripheral side of the connecting portion.

  In Claim 4, as said test piece, at least any one of the thickness of an arc part, the thickness of a connection part, the outer periphery side curvature of a connection part, the inner periphery side curvature of a connection part, and the curvature of an arc part A plurality of test pieces having different values are prepared, and the repeated load test is performed on them.

  In Claim 5, in the said test piece, the some test piece which changed at least any one among mold material, hardness, and surface treatment is created, and the said repeated load test is performed about these. Is.

  As effects of the present invention, the following effects can be obtained.

In claim 1, a repeated load test can be performed using a test piece that is a partial shape of a water jacket insert, so that the insert shape and material can be determined. The actual machine test only needs to be performed once. Therefore, costs and resources required for the test can be reduced as compared with the case where the test is performed with the entire shape of the water jacket insert and the insert life is evaluated.
Also, obtain a stress value closer to the stress state that occurs in the actual water jacket insert compared to when calculating with a CAE system, etc., and reliably estimate the fatigue life of the water jacket insert based on this. Can also be reflected in the design.

  According to the second aspect, since a load closer to the load applied during casting is applied to the water jacket insert, the life of the water jacket insert can be more accurately evaluated.

  In the third aspect, when a load is applied to one place, the relationship between the crack generated in the test piece and the load can be clarified most efficiently, and a simple test can be performed.

  In claim 4, the optimum value can be obtained for the shape factor that affects the life of the water jacket insert, and the insert shape can be determined based on this.

  According to the fifth aspect, the optimum material can be obtained for the material factor that affects the life of the water jacket nesting, and the nesting material can be determined based on this.

Next, embodiments of the invention will be described.
1 is a perspective view of a water jacket insert according to an embodiment of the present invention, FIG. 2 is a plan view of the water jacket insert, and FIG. 3 is a plan view of a test piece. FIG. 4 is an apparatus configuration diagram for a repeated load test.

  As shown in FIGS. 1 and 2, the water jacket insert 10 of the cylinder block of the engine is arranged in a row with a plurality of cylinders partially overlapped so that the axial directions thereof are substantially parallel. The shape is common. That is, the water jacket insert 10 is formed by connecting a plurality of arc portions 12, 12. In the water jacket insert 10, the thickness of the connecting portion 11 connecting the arc portions 12 and 12 is thicker than that of the arc portions 12 and 12. In the arc portion 12 of the water jacket insert 10, there are many cases in which crack Cr occurs in the portion immediately before the thickness changes from the arc portion 12 to the connection portion 11, and this is designated as “crack occurrence range 13”. .

  In the present invention, a portion of the water jacket insert 10 including the crack frequent occurrence region 13 that is located in the vicinity of the connection portion 11 in the arc portion 12 and is a portion in which the wall thickness changes is created as a test piece 20. The test piece 20 is used to perform a repeated load test, and the life of the water jacket insert 10 is evaluated from the test result.

  The test piece 20 includes at least two adjacent arc portions 12 and 12 that form the outer peripheral shape of the water jacket insert 10 and one connection portion 11 that connects the arc portions 12 and 12 to each other. A part of the insert 10 is divided.

  In the present embodiment, as shown in FIG. 3, the test piece 20 has approximately one-quarter yen from the connecting portion 11 to the left and right, with the one connecting portion 11 of the water jacket insert 10 being substantially centered in the left-right direction. The shape is cut so as to include only the arc portions 12 and 12. Accordingly, the test piece 20 has a cross-sectional shape in which two circular arcs are connected in a mountain shape, and the test piece 20 includes two crack frequent occurrence areas 13 and 13 on both the left and right sides of the connection portion 11.

In order to evaluate the life of the water jacket insert 10, a repeated load test of the test piece 20 is performed.
In the repeated load test, as shown in FIG. 4, a load applying device 22 for applying a load to the test piece 20, a strain gauge 23, an amplifier 24 to which the strain gauge 23 is connected, the amplifier 24 and the load An arithmetic processing device 25 to which the additional device 22 is electrically connected is used.

The load applying device 22 repeats addition and release of the load to the test piece 20, and information regarding the added load and the number of times is acquired by the arithmetic processing device 25.
In the repeated load test, a load is applied to the test piece 20 to increase or decrease the connection angle (θ ₁ shown in FIG. 3) of the arc portions 12 and 12 connected at the connection portion 11. This is because the life of the water jacket insert 10 is more accurately evaluated by applying a load closer to the load applied during casting to the water jacket insert 10.

  In the present embodiment, the test piece 20 is placed so that the arc portions 12 and 12 are in contact with the test table 27, and the load applied by the load applying device 22 is applied from the inner peripheral side to the outer peripheral side. Added directly. When applying a load to the test piece 20 in this manner, it is known that a reliable result can be obtained without applying a load from the outer peripheral side from past test results, etc. Since it is possible to obtain a result whose influence is most easily understood by applying a load to one place, it is efficient and preferable.

However, depending on the shape of the water jacket insert 10, how to apply the load and the influence thereof are different. Therefore, it is desirable to apply the load in a plurality of modes and make a comprehensive determination in order to improve accuracy.
For example, an aspect of adding a load from the inner peripheral side of the connecting part 11 to the outer peripheral side to the connecting part 11, an aspect of applying a load from the outer peripheral side of the connecting part 11 to the inner peripheral side of the connecting part 11, In one or a combination of a mode in which a load for compressing the test piece 20 from both ends of the arc portion 12 and a mode in which a load for pulling the test piece 20 from both ends of the arc portion 12 is added. A load can be applied to the test piece 20.

The strain gauge 23 is attached to each of the outer peripheral side and the inner peripheral side of the arc portions 12 and 12 in the crack occurrence regions 13 and 13 of the arc portions 12 and 12 of the test piece 20. 13 distortions are detected.
The detection signal of the strain gauge 23 is amplified by the amplifier 24 and transmitted to the arithmetic processing unit 25.

  The arithmetic processing unit 25 can be configured by a general-purpose computer including a monitor 26 and the like. The arithmetic processing unit 25 functions as strain calculation means, stress calculation means, and crack detection means. In the present embodiment, the single function processing device 25 is configured to perform the above functions, but each function may be configured to be executed by a separate and independent device.

The strain calculation means receives the detection signals detected by the strain gauges 23, 23,... And calculates the strain of the crack frequent occurrence range 13, 13 of the test piece 20.
The stress calculation means calculates the stress generated in the crack frequent occurrence areas 13 and 13 in response to the strain value of the crack frequent occurrence areas 13 and 13 calculated as described above.
The crack detection means is a means for detecting the occurrence of cracks in the crack frequent occurrence areas 13 and 13 of the test piece 20 in response to the strain value of the crack frequent occurrence areas 13 and 13 calculated as described above. The fatigue life of the test piece 20 is the number of times that the load is applied by the load applying device 22 before the crack is generated.

The repeated load test is repeatedly performed by changing the thickness and curvature, which are the shape factors affecting the life of the water jacket insert 10 based on the experimental design method. Obtain an optimum value for each of these form factors, which can yield a lifetime that satisfies the specified lifetime.
That is, as shown in FIG. 3, as influencing the shape factor on the life of the water jacket insert 10, the thickness D ₁ of the arcuate portions _12, the thickness D ₂ of the connecting portion _11, connecting portion outer peripheral side curvature R ₁ of The repeated load test is performed by changing the values of the inner peripheral curvature R _{2 of} the connecting portion and the curvature R ₃ of the arc portion 12.

  The above repeated load test is repeatedly performed by changing the mold material, hardness, and surface treatment, which are material factors affecting the life of the water jacket insert 10 based on the experimental design method. The optimum material is obtained in which the insert 10 can obtain a life satisfying a predetermined life set in advance.

  And based on the result of the above repeated load test, the crack life of the water jacket insert is predicted, and the shape factor and material factor affecting the life are optimized. The nesting shape and material are determined so that a life satisfying the life can be obtained.

Conventionally, in a production start test, it is necessary to manufacture an actual mold several times, the optimization accuracy is low, and a large number of man-hours are required to stabilize the life. On the other hand, in the present invention, it is possible to perform a repeated load test using the test piece 20 which is a partial shape of the water jacket insert 10 to determine the insert shape and material, so that the optimum design is performed. The actual machine test to confirm is only once. Therefore, the cost and resources required for the test can be reduced as compared with the case where the entire life of the water jacket insert 10 is tested and the insert lifetime is evaluated.
In addition, compared with the case of calculating with a CAE system or the like, a stress value closer to the stress state generated in the actual water jacket insert 10 is obtained, and based on this, the fatigue life of the water jacket insert 10 is reliably estimated. Can also be reflected in the design.

The perspective view of the water jacket insert which concerns on the Example of this invention. The top view of a water jacket nesting. The top view of a test piece. The apparatus block diagram for a repeated load test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Water jacket insert 11 Connection part 12 Arc part 13 Crack frequent occurrence range 20 Test piece 22 Load application apparatus 23 Strain gauge 25 Arithmetic processing apparatus

Claims (5)

A method for evaluating the life of a water jacket insert for a casting mold of an engine cylinder block,
Create a test piece that forms a part of the water jacket insert, including at least two adjacent arc portions forming the outer peripheral shape of the water jacket insert and one connecting portion connecting the arc portions. And
Distortion of the arc portion measured by the strain gauge by providing a strain gauge on each of the inner circumference side and the outer circumference side in the arc portion of the test piece and in the vicinity of the connection portion, applying a load to the test piece From the above, it is characterized by performing a repeated load test to detect either one or both of the stress generated in the test piece or the crack generated in the test piece,
Casting mold nesting life evaluation method. In applying a load to the test piece,
The front connection part is characterized by giving a load that increases or decreases the connection angle of the arc part, or increases or decreases,
The casting mold casting die nested life evaluation method according to claim 1. In applying a load to the test piece,
A load is applied to the connecting portion from the inner peripheral side to the outer peripheral side of the connecting portion.
The casting mold nested life evaluation method according to claim 1 or 2. As the test piece, the thickness of the arc part, the thickness of the connection part, the outer peripheral side curvature of the connection part, the inner peripheral side curvature of the connection part, the curvature of the arc part was changed, A plurality of test pieces are created, and the repeated load test is performed on them.
The casting mold nested life evaluation method according to any one of claims 1 to 3. In the test piece, a plurality of test pieces in which at least one of mold material, hardness, and surface treatment is changed are created, and the repeated load test is performed on these test pieces,
The casting mold nested life evaluation method according to any one of claims 1 to 3.

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