Fatigue test model of T-shaped joint and design and application method thereof

Abstract

The invention relates to a T-shaped joint fatigue test model and a design and application method, the T-shaped joint fatigue test model comprises a test piece and a clamping piece which are matched with each other, the test piece is a T-shaped joint and comprises a stress plate and a force application plate, and the force application plate is divided into a connecting section, a transition section, a first clamping section, a second clamping section, a third clamping section and a fourth clamping section, the clamping piece is connected with the large end of the transition section and is in clamping connection with an external testing machine, the clamping piece is a U-shaped clamping groove and comprises a clamping groove part used for containing the stress plate and a second clamping section located on the closed side of the clamping groove part, and the second clamping section is in clamping connection with the external testing machine. The connector and clamping groove combined device is designed according to the application environment of T-shaped connectors in ship and ocean engineering, and is suitable for simulating the fatigue wear condition in the ocean engineering for testing.

Description

Technical Field

[0001] The invention relates to the technical field, in particular to a fatigue test model of a T-joint and a design and application method thereof. Background Art

[0002] T-type structure refers to the joint formed by the transverse extension of one of the steel plates. It has been widely used in the design of ship and marine engineering structures. Fatigue damage will occur under repeated alternating stress, which may cause a lot of expensive repair work, affecting the service capacity and operating economy of the ship, and also become the starting point of catastrophic damage. The fatigue strength problem of ship structure has been a concern of the ship and marine engineering community for many years.

[0003] There are two main methods for studying fatigue strength problems: SN curve method and fracture mechanics method. Fracture mechanics method is relatively complex and involves many factors. Since each factor contains uncertainty, the final result has great uncertainty or discreteness. Therefore, the SN curve method is still the main method for fatigue strength assessment of ships and marine engineering structures.

[0004] Although the relevant standards or specifications provide fatigue strength assessment methods for hot spot stress and the recommended corresponding SN curves, the hot spot stress cannot take into account the influence of detailed factors such as the local geometric shape and size of the weld toe. The notch stress calculation is very sensitive to the geometric parameters of the weld toe, such as the weld toe angle, radius and weld shape, but it is quite difficult in actual engineering operations. From an engineering practical perspective, in order to consider the fatigue performance of such joints, corresponding fatigue tests need to be carried out. However, the relevant standards / specifications at home and abroad currently do not provide fatigue test methods and test equipment for such joints. Summary of the invention

[0005] Aiming at the fatigue test of T-joint, the applicant provides a fatigue test model of T-joint with reasonable structure and its design and application method.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A fatigue test model of a T-joint, comprising a test piece and a clamping piece matching each other,

[0008] The test piece is a T-type joint, including a force-bearing plate and a force-applying plate. The force-applying plate is divided into:

[0009] The connecting section is vertically welded to the load-bearing plate.

[0010] The transition section connects with the connecting section and its width gradually increases.

[0011] The first clamping section is connected with the large end of the transition section and clamped and connected with the external testing machine.

[0012] The clamping piece is a U-shaped slot, comprising a slot portion for accommodating the force-bearing plate and a second clamping section located on a closed side of the slot portion, and the second clamping section is clamped and connected to an external testing machine.

[0013] As a further improvement of the above technical solution:

[0014] The width of the force-bearing plate of the test piece and the width of the slot portion in the same direction are equal.

[0015] The thickness of the load-bearing plate and the force-applying plate of the test piece are the same.

[0016] The length of the side of the load-bearing plate of the test piece perpendicular to the force-applying plate is an even multiple of the plate thickness.

[0017] The lengths of the connecting section, the transition section and the first clamping section are different, and the length of the first clamping section is the largest.

[0018] Both sides of the transition section are inwardly concave arc walls, and the side edges of the transition section are tangentially connected to the connecting section.

[0019] A design method for a fatigue test model of a T-joint is disclosed. In the production of a T-joint test piece, the welding method, groove form, weld size and bottom welding condition are all carried out in accordance with product process requirements.

[0020] A test method for applying a fatigue test model of a T-joint to a compression-compression fatigue test. The test environment is a normal temperature environment or a low temperature environment. The first clamping section and the second clamping section are respectively installed on a fatigue testing machine. The test piece is continuously pressurized or intermittently pressurized multiple times.

[0021] A test method for applying a fatigue test model of a T-joint to a tension-torsion multi-axial fatigue test. The test environment is a normal temperature environment or a low temperature environment. The first clamping section and the second clamping section are respectively installed on a fatigue testing machine, and the test piece is subjected to continuous or intermittent stretching, pressurization, and torsion.

[0022] The beneficial effects of the present invention are as follows:

[0023] The joint and slot combination device provided by the present invention is designed for the application environment of T-joints in ships and marine engineering, and is suitable for simulating fatigue wear conditions in marine engineering and conducting tests.

[0024] The invention sets the width of the force plate and the width of the slot of the test piece in the model to be equal, in order to simplify the model. In actual use, most T-joint parts are large-sized structures, especially the actual parts corresponding to the force plate are large. If the actual shape is directly used in the test, on the one hand, it is large and difficult to operate, and on the other hand, it cannot cover all parts with T-joints. Therefore, the simplified model has high generalization.

[0025] The model can be set in multiple groups. The welding method, groove form, weld size and bottom welding condition of the model are all carried out according to the target object to be tested, and can be applied to several example working conditions proposed in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1(a) is a schematic diagram of the weld position of a T-joint.

[0027] FIG. 1( b ) is a schematic diagram of the weld position of another type of T-joint.

[0028] FIG. 2( a ) is a front view showing the dimensions of a test piece of the present invention.

[0029] FIG. 2( b ) is a side view showing the dimensions of a test piece of the present invention.

[0030] Figure 3 It is a three-dimensional diagram of the test piece of the present invention.

[0031] Figure 4 It is a three-dimensional diagram of the clamping member of the present invention.

[0032] Figure 5 It is a schematic diagram of the test piece and the clamping piece combination of the present invention.

[0033] Wherein: 1. Test piece; 2. Clamping piece;

[0034] 101, stress-bearing plate; 102, connecting section; 103, transition section; 104, first clamping section;

[0035] 201, slot portion; 202, second clamping section. DETAILED DESCRIPTION

[0036] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0037] The welding method, groove form, weld size and bottom welding of the T-joint specimen are carried out in accordance with the product process requirements. The simplified form of the weld of the T-joint is shown in Figure 1, which is located at the junction of the load-bearing plate and the connecting section.

[0038] There are currently two main methods used to study fatigue strength problems: the SN curve method and the fracture mechanics method.

[0039] The SN curve method utilizes an abstract "destruction" model to avoid stress analysis of the crack tip field, especially for non-super-thick plates in ship and marine engineering structures, where the life of the fatigue crack initiation stage accounts for the vast majority of the total life.

[0040] The fracture mechanics method can better reflect the scale effect and provide a more accurate remaining life estimation method for a structure with cracks, but the method is relatively complex and involves many factors. Since each factor contains uncertainty, the final result has great uncertainty or discreteness. Therefore, the fatigue strength assessment of ships and marine engineering structures is mainly carried out by the SN curve method.

[0041] Major classification societies such as DNVGL, ABS, BV and CCS have given corresponding SN curve selection principles and methods in the relevant standards or specifications for fatigue strength verification. For example, the DNVGL specification provides the SN curves of typical welding nodes and parent materials for fatigue strength assessment using the nominal stress method, and also provides the SN curve parameters of typical nodes. For fatigue strength assessment using the hot spot stress method, it is recommended to select the D curve for welding nodes and the B1 curve for parent material free edge nodes. The CCS Fatigue Strength Guide provides the hot spot stress method fatigue strength verification method, and the design SN curve selection principle is: for welding nodes, the D curve is used for fatigue strength assessment, and for the free edge of the parent material, the C curve is used for fatigue strength assessment.

[0042] Hot spot stress cannot take into account the influence of detailed factors such as the local geometric shape and size of the weld toe; the notch stress calculation is very sensitive to the geometric parameters of the weld toe, such as the weld toe angle, radius and weld shape, so it is quite difficult in actual engineering operations. From the perspective of engineering practicality, in order to consider the fatigue performance of this type of joint, the present invention provides a fatigue test device for a T-joint, and provides a test method for the device, so as to provide a feasible solution for the fatigue test of the T-joint.

[0043] like Figure 3 and Figure 4 As shown, the fatigue test model of the T-joint of this embodiment includes a test piece 1 and a clamping piece 2 that match each other.

[0044] The test piece 1 is a T-type joint, including a force-bearing plate 101 and a force-applying plate. The force-applying plate is divided into:

[0045] The connecting section 102 is vertically welded to the load-bearing plate 101.

[0046] The transition section 103 is connected to the connecting section 102, and its width gradually increases.

[0047] The first clamping section 104 is connected to the large end of the transition section 103 and is clamped and connected to an external testing machine.

[0048] The clamping member 2 is a U-shaped slot, including a slot portion 201 for accommodating the force-bearing plate 101 and a second clamping section 202 located at a closed side of the slot portion 201 . The second clamping section 202 is clamped and connected to an external testing machine.

[0049] The width of the force-bearing plate 101 of the test piece 1 and the width of the slot portion 201 in the same direction are equal.

[0050] The thickness of the force-bearing plate 101 and the force-applying plate of the test piece 1 is the same.

[0051] The side length of the force-bearing plate 101 of the test piece 1 perpendicular to the force-applying plate is an even multiple of the plate thickness.

[0052] The lengths of the connecting section 102 , the transition section 103 , and the first clamping section 104 are different, and the length of the first clamping section 104 is the largest.

[0053] Both sides of the transition section 103 are concave arc-shaped walls, and the side edges of the transition section 103 are tangentially connected to the connecting section 102 .

[0054] In the design method of the fatigue test model of the T-joint of this embodiment, in the production of the T-joint specimen, the welding method, groove form, weld size and bottom welding condition are all carried out in accordance with the product process requirements.

[0055] As a set of optional implementation parameters, the present invention provides the following table of test piece dimensions of the T-joint test piece, with reference to FIG. 2 ,

[0056]

[0057] The present embodiment uses a T-joint fatigue test model in a test method for a compression-compression fatigue test. The test environment is a normal temperature environment or a low temperature environment. The first clamping section 104 and the second clamping section 202 are respectively installed on a fatigue testing machine, and the test piece 1 is continuously pressurized or intermittently pressurized multiple times.

[0058] The present embodiment is a test method for applying a fatigue test model of a T-joint to a tension-torsion multi-axis fatigue test. The test environment is a normal temperature environment or a low temperature environment. The first clamping section 104 and the second clamping section 202 are respectively installed on a fatigue testing machine, and the test piece 1 is subjected to continuous or intermittent stretching, pressurization, and torsion.

[0059] The advantages of the present invention also lie in that the main stress-bearing position in the test model, i.e., the position of the weld, is streamlined and reduced, and the structure is simplified without affecting the test results, making the operation more convenient, and there are fewer interference factors in the obtained test results, thereby providing an effective test device and method.

[0060] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A fatigue test model for a T-joint, characterized in that: It comprises a test piece (1) and a clamping piece (2) that match each other, The test piece (1) is a T-shaped joint, comprising a force-bearing plate (101) and a force-applying plate, wherein the force-applying plate is divided into: The connecting section (102) is vertically welded to the load-bearing plate (101). The transition section (103) is connected to the connecting section (102) and its width gradually increases. The first clamping section (104) is connected to the large end of the transition section (103) and is clamped and connected to an external testing machine. The clamping member (2) is a U-shaped slot, comprising a slot portion (201) for accommodating the force-bearing plate (101) and a second clamping section (202) located on a closed side of the slot portion (201). The second clamping section (202) is clamped and connected to an external testing machine.

2. The fatigue test model of the T-joint according to claim 1, characterized in that: The width of the force-bearing plate (101) of the test piece (1) and the width of the slot portion (201) in the same direction are equal.

3. The fatigue test model of the T-joint according to claim 1, characterized in that: The thickness of the force-bearing plate (101) and the force-applying plate of the test piece (1) are the same.

4. The fatigue test model of the T-joint according to claim 3, characterized in that: The side length of the force-bearing plate (101) of the test piece (1) perpendicular to the force-applying plate is an even multiple of the plate thickness.

5. The fatigue test model of the T-joint according to claim 1, characterized in that: The lengths of the connecting section (102), the transition section (103), and the first clamping section (104) are different, and the length of the first clamping section (104) is the largest.

6. The fatigue test model of the T-joint according to claim 1, characterized in that: Both sides of the transition section (103) are inwardly concave arc-shaped walls, and the side edges of the transition section (103) are tangentially connected to the connecting section (102).

7. A method for designing a fatigue test model of a T-joint, characterized in that: In the production of T-joint specimens, the welding method, groove form, weld size and bottom welding conditions are all carried out in accordance with the product process requirements.

8. A test method for applying the fatigue test model of the T-joint according to claim 1 to a compression-compression fatigue test, characterized in that: The test environment is a normal temperature environment or a low temperature environment. The first clamping section (104) and the second clamping section (202) are respectively installed on a fatigue testing machine to continuously pressurize the test piece (1) or intermittently pressurize it multiple times.

9. A test method for applying the fatigue test model of the T-joint according to claim 1 to a tension-torsion multiaxial fatigue test, characterized in that: The test environment is a normal temperature environment or a low temperature environment. The first clamping section (104) and the second clamping section (202) are respectively installed on a fatigue testing machine to perform continuous or intermittent stretching, pressurization, and torsion on the test piece (1).

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