JP2720463B2 - Jig for testing high-temperature bending strength of ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a jig used for a high-temperature bending strength test of ceramics.

(Prior Art) In recent years, research and development of ceramic materials for high temperatures have been actively conducted, and the necessity of evaluating the mechanical properties of materials at high temperatures has increased.

In response to such requirements, jigs for strength tests at high temperatures have also been developed. For example, jigs made of silicon carbide ceramics are currently used, and jigs made of mullite ceramics have also been proposed (Japanese Patent Application Laid-Open No. 62-291539). No. 14), atmospheric 14
Testing at 00 ° C or higher is also possible. Along with the possibility of evaluating the mechanical properties of materials at such high temperatures, JIS R 1604 "Test Method for High Temperature Flexural Strength of Fine Ceramics" was enacted in 1987.

In the test specified in JIS R 1604, an elongated plate-like test piece is placed on a fulcrum placed at a fixed distance in a state of a simple support beam, and the fulcrum is used in a three-point bending strength test. A load is applied to one point at the center between the two points to calculate the maximum bending stress at the time of breaking. For the four-point bending strength, the load is divided into two points at the same distance to the left and right from the center between the two fulcrums. In addition, the maximum bending stress at the time of breaking is calculated.

By the way, in order to study the practical application of such ceramic materials with excellent mechanical properties, for example, to realize the application to gas turbine engines, etc., the reliability of characteristic values such as material strength required as test data must be considered. In order to satisfy such requirements, for example, a test piece must be dimensioned as specified in JIS R 1604 (width 4.0 ± 0.1 mm, thickness 3.0 ± 0.1 mm, length 36 mm or more). Note: It is conceivable that the test is performed with a size larger than about 40 mm that is usually used. At the actual test site, a test for such a large test piece is actually being attempted. .

When testing with such large specimens,
Naturally, it is necessary to use a jig to be used which is large enough to be used for the test. Usually, a structure known for the same type of test at normal temperature is used by analogy. If such a test jig is specifically described, for example, a jig for a four-point bending strength test is described with reference to FIG. This is a rectangular parallelepiped base block 41 having a plurality of arms 42, 43, and 44 erected along both sides of the long groove to form a long groove for inserting the test piece 50, and this arm. It is configured as a combination of a plurality of anvils 45, 46 that are used by being inserted into the provided lateral grooves, and pressurizers 47, 48 for carrying a load. Therefore, the conventional jig has, as a whole, a structure in which two rows of intermittent standing arms 42, 43, 44 are provided on the upper surface of a rectangular parallelepiped base block 41 along the longitudinal direction thereof. Has become. This jig is placed on an appropriate frame 49 and subjected to a test.

(Problems to be Solved by the Invention) Here, looking at the actual operation of the high-temperature bending strength test, this operation is performed by heating and heating a high-temperature heating furnace for the purpose of responding to a general request to shorten the test time. Cooling 200 ~ 1500 ℃ /
Although it is often performed at a high speed such as hr, it has been pointed out in this high-temperature bending strength test that the jig used often breaks. This is because when the furnace is rapidly heated and cooled as described above, the temperature distribution width inside the jig increases in the process, and it is inevitable that the thermal stress increases, so this is larger than the strength of the jig. It is thought that this could cause destruction. This problem becomes more serious as the dimension of the jig becomes larger, the width of the temperature distribution in the rapid heating / quenching process increases, and the thermal stress also increases.

Needless to say, in order to avoid such destruction, the time schedule of rapid heating and rapid cooling may be extended, but if the temperature distribution inside the jig is large, it takes a long time for the entire jig to reach a constant temperature, Such measures inevitably increase the test time. By the way, in the test using the large-sized conventional high-temperature bending strength test jig described above, the life is extremely short due to the destruction due to this thermal stress, and the problem of unavoidable prolonged test time becomes an issue. ing.

An object of the present invention is to solve these problems, structurally, the width of the temperature distribution inside the jig is small, so that it can resist the destruction due to the accumulation of thermal stress, prolong the life, shorten the test time. It is an object of the present invention to provide a ceramic jig for a high-temperature bending strength test that is effective in forming a ceramic.

(Means for Solving the Problems) A feature of the jig for testing the high-temperature bending strength of ceramics according to the present invention, which has been made to achieve the above object, is that the test piece is placed on the upper surface via an anvil. A base block that is supported and placed in contact with the base on the lower surface, and the groove is formed so as to stand upward from the upper surface of the base block to form an elongated groove into which a strip-shaped test piece can be inserted from above. A lower symmetrical anvil for supporting a lower surface of a test piece over two vertically symmetrical arm blocks provided on both sides sandwiched between the arm blocks. A jig made of ceramics for performing a high-temperature bending strength test of the ceramics in a high-temperature heating furnace, which is provided with a lateral groove for insertion and positioning of the base block,
An upper base block main body having a rectangular cross section, and lower legs extending downward from the main body from a position separated along a longitudinal direction of a test piece placed on the main body, The lower surface of the leg in contact with the gantry has a total area of 2/3 or less of the cross-sectional area of the base block main body, and a surface pressure per unit area of 1/5 or less of the compressive strength. It is where the composition is made.

When the jig of the present invention is configured to be used for a four-point bending strength test, in addition to the above configuration, a lateral groove for inserting an upper anvil for forming a load application point on the arm block may be formed. I just need.

That the horizontal section of the leg having the above structure can satisfy the compressive strength under load is defined as being within a dimensional range given in accordance with a design standard that does not cause compression failure in consideration of a predetermined safety factor and the like. Say.

Examples of the material of the jig of the present invention include silicon carbide ceramics, mullite ceramics, mullite ceramics reinforced with whiskers such as silicon carbide and zirconia, fibers, particles, and the like.

(Operation) The object of the present invention is achieved by the above configuration for the following reason.

In other words, the test jig is generally used by being placed on an appropriate base made of the same material as the test jig. Since the gantry is a large structure, it has a large heat capacity.Thus, during heating, the heat of the jig is taken away by the gantry due to heat conduction, and the temperature rise slows down. When heat is applied, the temperature drop slows down, and due to these effects, a large temperature difference is likely to occur between the portion that is in contact with the gantry and the upper portion of the base block that is not in contact with the gantry, and inside the base block, This tends to increase the width of the temperature distribution.

On the other hand, the jig of the present invention restricts the contact area of the jig to the gantry to reduce the effect of heat conduction between the gantry and the gantry. The effect of the problem described above is reduced, and the risk of breakage due to thermal stress is reduced.

The leg shape of the base block in the jig of the present invention is preferably such that bending stress is not generated in the base block when a load is applied during a test. Therefore, the position of the leg of the base block forms the fulcrum of the test piece. It is preferred that the lower anvil be located just below the insertion position.

The legs are intended to limit the heat conduction between the jig and the gantry on which it is mounted, so as to avoid a large temperature difference inside the jig, especially inside the base block. Is affected by the height of the leg. However, even if the leg height is too large, a significant improvement in the effect cannot be expected, and generally, the heating / cooling speed is 200 to 1500 ° C / hr,
Assuming that the test temperature is about 1500 ° C, the length of the leg is about twice the thickness of the part from the bottom of the groove where the lower anvil is set to the upper end of the leg (hereinafter this part is called the base block body). It is often appropriate to use

In addition, the size of the area of the bottom of the leg, that is, the size of the contact area between the base block and the gantry affects the effect of the present invention, and the smaller the area, the better the effect of the present invention. If it is too small, the surface pressure during load application may increase, which may cause a problem such as breakage of the leg due to compressive stress. Therefore, generally, the jig and the gantry are made of silicon carbide ceramics or mullite ceramics, and the heating / cooling speed is 200 to 1500.
° C / hr, when the test temperature is set to about 1500 ° C, the total area of the lower surface of the legs is set to 2/3 or less, preferably 1/2 or less, with respect to the area of the horizontal section of the base block body of the jig, In consideration of its compressive strength, it is desirable in design that the surface pressure per unit area of the lower surface of the leg be 400 kgf / cm ² or less (the safety factor is 5 times, that is, 1/5 or less of the compressive strength). .

The jig of the present invention can be applied to either a three-point bending test or a four-point bending test.

The jig of the present invention satisfies the above conditions, and the horizontal cross section of the base block main body may be any of a circle and a square (usually a rectangle), and the shape of the lower surface of the leg is also particularly limited. Not a thing, for example, circular, square (rectangular)
Other donut shape or the like, or may be divided into a plurality.

(Examples) The present invention will be described below based on examples shown in the drawings.

FIG. 1 shows an example of a jig for a high-temperature four-point bending strength test of ceramics according to the present invention. The jig in this example has a base block body 1 having a rectangular cross section, Further, legs 2, 2 extending downward from the lower surface of the base block main body 1 are roughly divided into two in the longitudinal direction of the main body 1, and the cross section thereof gradually increases in area from above to below. Has a structural feature that it has a gradually decreasing rectangular shape.

Arm blocks 3, 4, and 5 are erected in two rows along both sides of the base block body 1 in the longitudinal direction. In this example, the arm blocks 3, 4, and 5 in each row are A low-height first arm 3 located at the end, a high third arm 5 located at the center in the longitudinal direction, and between the center third arm 5 and the first arms 3 at both ends. The second arm 4 is located at the same height as the third arm 5 and is set such that there is a gap between the arms so that the anvils 21 and 22 can be inserted from above. In the following description, a gap located between the first arm 3 and the second arm 4 is referred to as a lower anvil fitting groove 8 and is located between the second arm 4 and the third arm 5. The gap is referred to as an upper anvil fitting groove 9, and a long continuous gap in the longitudinal direction between two left and right arm blocks is referred to as a test piece fitting groove 10.

Reference numeral 11 denotes an opening which is circularly cut from the upper position to a certain height from the center of the arm blocks 3, 4, and 5, and the pressurizing element 23 is inserted and moved downward, and is inserted into the upper anvil insertion groove 9. The upper anvil 22 (see FIG. 2) that has been inserted is engaged.

FIG. 2 shows a state in which a high-temperature bending strength test is being performed using the jig. The jig is placed on a gantry 20 in an electric furnace 31 and a pair of lower anvil fitting grooves is provided. 8 and the lower anvils 21, 21 are fitted into the lower anvils 21, 21.
As shown in the figure, a test piece 30 is erected, and the upper anvils 22 and 22 are positioned by being inserted into the pair of upper anvil fitting grooves 9 so as to rest on the test piece 30. , 22 and a disc-shaped pressurizing element 23 having a size that can be substantially inserted into the opening 11 is placed thereon, and each of the pressure rods 24 is
Is applied. At the center of the upper surface of the disc-shaped pressurizer 23, pressurization is applied to a pair of upper anvils 22,2.
A hemispherical projection 23a is formed to act evenly on 2. Reference numeral 32 denotes a heating element of the electric furnace 31.

Preferred dimensions of each part of the jig having such a shape are as follows.

 The symbols shown in FIG. 1 indicate the following dimensions.

(Dimensions of test piece and anvil, etc.) a: Length of test piece b: Width of test piece c: Thickness of test piece d: Span between a pair of lower anvils (distance between groove center positions of grooves 8, 8) e: Span between a pair of upper anvils (distance between groove center positions of grooves 9, 9) w: Anvil diameter (4 mm ≦ w ≦ 6 mm; compliant with JIS R 1604) (Jig dimensions) f: Jig Long dimension (left / right direction in FIG. 1 (a)) d + w <f ≦ 1.5ag: lateral dimension of the jig (vertical direction in FIG. 1 (a)) 2b ≦ g ≦ 10b h: length of bottom of leg Shaft direction (same as above) Dimensions 1/20 ・ f ≦ h ≦ 1/2 ・ fi i: Lateral (same as above) dimension of leg bottom 1/10 ・ g ≦ i ≦ g It is provided so as to be located immediately below the grooves 8, 8 where the anvil is set, and the product of h and i is determined so that the load applied during the test falls within the above-mentioned surface pressure condition range.) J: Base block body thickness 2mm ≦ j ≦ 8c−2mm It does not directly affect the strength of the jig at the time of the test, but it is preferable to set it to 2 mm or more because it affects the strength of the groove holding the anvil.) K: Leg height 2c-2mm ≦ k ≦ 8c-2mm ( The value of k + j greatly affects the strength of the jig during the test.
If this value is set to 2 to 8 times the thickness c of the test piece, there is no problem in strength. As described above, k / j is preferably about twice. N: width of groove into which anvil is inserted and set w <n ≦ w + 0.2 mm p: height of second arm 4 and third arm 5 c + 2w <p ≦ 100 mm q: depth of groove 8 0.5 w <Q ≦ p (it is sufficient if the lower anvil does not move.) R: width of the groove 10 b ≦ r ≦ 1.1bs: height from the bottom of the groove 10 to the top of the jig p−w <s ≦ pt : Height from the bottom of the groove 9 to the upper end of the jig p− (w + c) <t ≦ pu: diameter of the opening where the pressurizer 24 is set u> e, but usually u = about 1.5ev : Depth of the opening in which the pressurizing element 24 is set p- (2w + c) <v ≦ p Example 1 The cure of the shape of FIG. A tool was produced.

d: 60mm j: 3mm s: 20mm e: 20mm k: 17mm t: 19mm f: 120mm n: 6.05 mm u: 30.5mm g: 40mm p: 20mm v: 10mm h: 32mm q: 6mm i: 25mm r: 8.2 mm The jig is placed on a gantry in the electric furnace 31 shown in FIG. 2 and the lower anvil 21 and the upper anvil 22 (each having a diameter of 6 m)
m), pressurizer 23 (diameter 30.5 mm), and test piece (width 8 mm,
Set the thickness 6mm, length 100mm) in place and set the test temperature 1
300 ° C, crosshead speed 0.5 to push down the pressure rod 24
A four-point bending test at mm / min was performed. Heating rate is 650
° C / hr and the cooling rate was 300 ° C / hr. Under these conditions, 150 tests, that is, heating and cooling 150 times, did not cause any damage to the jig. The load applied to the pressurizer was 150 kgf minimum and 450 kgf maximum.

Comparative Example A jig having the same material and dimensions as in Example 1 was prepared, except that the thickness of the rectangular parallelepiped base block was set to 20 mm from the bottom of the groove in which the lower anvil was set without providing the jig with legs. The test was performed under the same conditions.

 As a result, the jig split in the 16th test.

(Effects of the Invention) According to the present invention, the width of the temperature distribution is made as small as possible inside a jig in which rapid heating / cooling is frequently performed at the time of use. Therefore, the usefulness of the jig as a high-temperature bending strength test jig is extremely large because it is possible to extend the life of the jig or shorten the test time.

The present invention has a jig having a long dimension of 50 mm or more and a width dimension of 20 mm.
As described above, the present invention shows particularly excellent usefulness in the case of a large jig having a base block body thickness (height from the lower anvil to the lower surface of the leg) of 10 mm or more. This is particularly effective when silicon ceramics, mullite ceramics, or mullite ceramics reinforced with whiskers, fibers, particles, or the like such as silicon carbide and zirconia are used.

[Brief description of the drawings]

1 (a) to 1 (d) are views schematically showing the construction of an example of a jig for testing a high-temperature bending strength of ceramics according to the present invention. FIG. 1 (a) is a front view, FIG. 1 (b) is a side view, FIG. 1 (c) is a plan view, and FIG. 1 (d) is a bottom view. FIG. 2 is a view for explaining a use state of the jig. FIGS. 3 (a) and 3 (b) are views for explaining the use state of an example of a conventional jig for bending strength test, and FIG.
FIG. 3A is a front view thereof, and FIG. 3B is a side view thereof. DESCRIPTION OF SYMBOLS 1 ... Base block, 2 ... Leg 3 ... 1st arm, 4 ... Second arm 5 ... 3rd arm 8 ... Lower anvil fitting groove 9 ... Upper anvil fitting groove 10 ... groove for inserting test piece, 11 ... opening 21 ... lower anvil, 22 ... upper anvil 23 ... pressurizer, 24 ... pressurizing rod 30 ... test piece, 31 ... electric furnace 32 ...... Heating element

Claims (2)

(57) [Claims] 1. A base block that supports a test piece on an upper surface via an anvil and is placed and placed on a gantry on a lower surface, and a strip-shaped test piece that stands upright from the upper surface of the base block. Two rows of substantially symmetrical arm blocks provided on both sides of the groove so as to form an elongated groove that can be inserted from above, and these two rows of vertically arranged arms are further provided. A ceramic jig for performing a high-temperature bending strength test of ceramics in a high-temperature heating furnace, provided with a lateral groove for inserting and positioning a lower anvil for a fulcrum supporting the lower surface of the test piece over the block. Wherein the base block extends downward from the main base block main body having a rectangular cross section and a position separated along a longitudinal direction of a test piece placed on the main body. And a lower leg, The lower surface in contact with, and the total area to the area of the cross section of the base block body and 2/3 or less,
A jig for testing a high-temperature bending strength of ceramics, wherein a surface pressure per unit area is set to 1/5 or less of a compressive strength. 2. A jig for testing a high-temperature bending strength of ceramic according to claim 1, wherein the legs of the base block are located immediately below the lower anvil.