CN201196613Y

CN201196613Y - Material fracture toughness test sample without prefabricated crackle

Info

Publication number: CN201196613Y
Application number: CNU2008200930871U
Authority: CN
Inventors: 吴力航
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-04-07
Filing date: 2008-04-07
Publication date: 2009-02-18
Anticipated expiration: 2018-04-07

Abstract

The utility model provides a fracture toughness testing sample for a material without precrack, which is characterized by comprising a material sample body to be tested with smooth surface and a fragile lamina, wherein the fragile lamina is compounded on the smooth surface of the sample body, has known mechanical performance parameters and higher elasticity modulus and can crack at first during loading procedure. The utility model has a simple structure and easy manufacture, and improves the dependence on the dimension of a testing component in a material fracture toughness test; meanwhile, the material sample can be implemented simply so as to greatly reduce the testing cost. With the sample, the plastic deformation work of a plastic zone on a crack tip can be directly tested. The testing parameter of the plastic work can be conveniently converted into current KIC and JIC parameter values for material fracture toughness according to the prior fracture mechanical theory computing formula.

Description

The material fracture toughness test sample of no precrack

Technical field

The utility model relates to the test sample of the conventional fracture toughness of construction material, especially a kind of material fracture toughness test sample that does not have precrack.

Background technology

According to Theory of Fracture Mechanics, as long as the geometric scale of sample is enough big, just can guarantee that the crackle forward position is in desirable plane strain state, just should be able to test out the fracture toughness K of this material _ICValue.But in fact, for the lower material of those intensity, it is too thick big to ensure that the crackle forward position is in the required sample yardstick of plane strain state, therefore require the power scale of Material Testing Machine also just excessive, be actually the fracture toughness value that on current at present Material Testing Machine, to obtain them.This limitation of current method of testing is because the limitation of method of testing itself is brought.In a sense, the design of current engineering structure is to be based upon on the basis of the too loose anti-fracture safety coefficient of employing just to be supported, and is actually to have paid huge material and power waste.If can be more accurately, measure and be used for the fracture toughness value of manufacturing engineering construction material more widely, just can rationalize engineering structure design greatly so that the Fracture Toughness Parameter of material and their other mechanical performance parameter better fit are got up.

Traditional fracture toughness method of testing and the test sample that derives from can't be done effective district with the characteristic of material mechanics that belongs to internal factor with the sample geometric shape that belongs to external factor and cut, cause the excessive of material test mechanomotive force scale that sample yardstick scale requires, but therefore limited the category of test material greatly.Again on the preparation method of fracture toughness specimen itself.Existing material fracture toughness test is (for obtaining the K of material _ICValue and J _ICThe three-point bending sample and the compact tensile specimen that are worth and adopt), all need at first in sample, to produce a macroscopic cracking.Because the process of precrack is very complicated, the crackle situation of making is very responsive to test result influence subsequently.Therefore, except what speak of above, outside the not testability that causes owing to the reason of sample yardstick to low-intensity material, even for those high-strength materials that can test, also be easy to occur because the dispersion of the test data that causes of unmanageable uncertainty in the crackle manufacturing process, reduced the credibility of data.

The utility model content

The purpose of this utility model is the defective that exists at said sample, and a kind of difficulty that can improve simultaneously from two aspects the present material fracture toughness measuring technology is provided, and also need not the material fracture toughness test sample of precrack on sample simultaneously.The utility model does not have the material fracture toughness test sample of precrack, it is characterized in that: it is to be made of ganoid detected materials sample body and the fragility thin layer known its mechanical performance parameter of one deck, that have the higher elasticity modulus, that can at first ftracture in loading procedure that is compounded on its smooth surface.

Described fragility thin layer is metallic ceramics thin slice or powder metallurgy thin slice.

Described fragility thin slice sticks on detected materials sample body smooth surface by bonding agent.

The cementing agent that is adopted should be able to ensure when sample is loading and causing on brittle layer and in all processes of crackle the slip between the relative matrix of brittle layer can not take place and peel off.

Described bonding agent is 502 glue.The design concept that the utility model does not have the material fracture toughness test sample of precrack is: at the compound last layer fragility of detected materials sample body surface thin layer.Utilize the characteristic of sample at first cracking of fragility thin layer in crooked loading procedure, directly " produce " one and split sharp plastic zone on member bodies to be measured surface.So just can determine the loading data of this crackle counterincision point place material according to the yardstick of formed crackle and known external applied load situation in the mechanical performance parameter of known fragility thin layer, the fragility thin layer.On the detected materials surface, produce these under these known conditions and split the required plastic work done in sharp plastic zone by being determined at, and by reasonable method be extrapolated to make material in unilateral stretching experiment, occur in the plastic work done (according to " the single curve principle " in the plasticity) of correspondence during necking down, the critical plastic work done in the time of just can determining this material and in splitting sharp plastic zone, germinate the hole.This critical plasticity energy when just crack tip plastic zone begins to expand in the detected materials.

The utility model does not have the material fracture toughness test sample design science of precrack, simple in structure, make easily, it has improved in the material fracture toughness test the dependent situation of test member yardstick, this sample is implemented simply simultaneously, thereby can reduce testing cost greatly.Because the crackle forward position in the detected materials is to adopt different types of fragility thin layer to be incorporated into indirectly in the detected materials sample body top layer, this just no longer need be in tested material sample body direct precrack.In other words, the essence effect of fragility thin layer is that the crackle that will extend in sample body in the tradition has extended in hollow conversely equivalently.Because the fragility thin layer is thinner, cause to split sharp plastic zone less, therefore this introduce crackle and form the method for splitting sharp plastic zone by the fragility thin layer can solve because the strength of materials is crossed the low excessive problem of sample overall dimension that causes.Make the structured material of any kind of can be used for making the body of sample and realize it is carried out the test of fracture toughness.That is to say that its outstanding value just is to make that adopting three-point bending sample that has the fracture toughness test sample now and those structured materials that compact tensile specimen all can't be measured to become originally can test its fracture toughness K _ICBe worth.

Do not have the formation structure and the principle of work of the material fracture toughness test sample of precrack from described the utility model and be not difficult to infer, adopt the utility model sample, can directly test out the plastic yield merit that forms a crack tip plastic zone.The test parameter of this plastic work done can be scaled the K of at present general material fracture toughness easily according to existing Theory of Fracture Mechanics computing formula _ICAnd J _ICParameter value.Can also infer simultaneously, adopt the utility model sample, for the low material of yield strength, its obtainable detecting information amount is big more, thereby test result is accurate more.Therefore it has formed an excellent complementary relationship technically with the three-point bending and the compact tensile specimen method of testing that pass through at present: adopt the utility model samples to test sensitive inadequately high-strength material for those, can adopt existing sample and method of testing thereof; And, can adopt the utility model sample and method of testing thereof for low-intensity material big with existing sample testing error even that can't implement.

The concrete structure that the utility model does not have the material fracture toughness test sample of precrack is provided by the following drawings and embodiment.

Description of drawings

Fig. 1 does not have the material fracture toughness test sample structural representation of precrack.

Embodiment

Embodiment: the material fracture toughness test sample that can be clear that no precrack from Fig. 1 is by detected materials sample body 1 and be compounded in its surperficial one deck TiC and TiN metallic ceramics fragility thin layer 2, and the thickness of fragility thin layer 2 is 1mm.This fragility thin layer 2 adopts 502 glue to stick on detected materials sample body 1 smooth surface.Described detected materials sample body 1 is a stainless steel material, and it is of a size of 50X10X6mm.

Above content be in conjunction with concrete preferred implementation to further describing that the utility model is done, can not assert that concrete enforcement of the present utility model is confined to these explanations.For the utility model person of an ordinary skill in the technical field; under the prerequisite that does not break away from the utility model design; its framework form can be flexible and changeable; if just make some simple deduction or replace, all should be considered as belonging to the scope of patent protection that the utility model is determined by claims of being submitted to.

Claims

1. material fracture toughness test sample that does not have precrack is characterized in that: it be by ganoid detected materials sample body and be compounded on its smooth surface known its mechanical performance parameter of one deck, that have the higher elasticity modulus, can be in loading procedure at first the fragility thin layer of cracking constitute.

2. the material fracture toughness test sample of no precrack according to claim 1, it is characterized in that: described fragility thin layer is metallic ceramics thin slice or powder metallurgy thin slice.

3. the material fracture toughness test sample of no precrack according to claim 1 and 2, it is characterized in that: described fragility thin slice sticks on detected materials sample body smooth surface by bonding agent.

4. the material fracture toughness test sample of no precrack according to claim 3, it is characterized in that: described bonding agent is 502 glue.