Novel electro-hydraulic servo testing machine loading pad and heat treatment method thereof

Abstract

The application provides a novel loading pad for an electro-hydraulic servo testing machine and a heat treatment method thereof, and the loading pad is installed at a chuck of the electro-hydraulic servo testing machine, and the loading pad has heat conduction holes which are equal-section through holes penetrating the pad from the side. The application forms the heat conduction holes by adding several equal-section through holes penetrating the pad from the side, and the heat conduction holes increase the heat exchange channels in the loading pad during temperature change, so that the temperature gradient in the heat treatment is reduced, the residual stress in the heat treatment is lower, and the service life of the pad is improved.

Description

Technical Field

[0001] This invention relates to the field of static and fatigue testing equipment, specifically a novel loading pad for an electro-hydraulic servo testing machine and its heat treatment method. Background Technology

[0002] With the increasingly widespread application of new materials and structures in various industrial fields, the demand for mechanical testing of high-strength materials and structures is also gradually increasing. For high-strength materials and structures, such as fiber-reinforced composite specimens, mechanical testing generally requires the use of large-tonnage electro-hydraulic servo testing machines, along with grips and pads that are large in size and weight and have complex shapes. Especially for small-volume, high-load testing machine loading pads, which often have walls of varying thicknesses, heat treatment is difficult. If the loading pads used in testing machines operating under large loads fail, the test will result in a catastrophic accident. Traditional testing machine loading pads are characterized by high material costs, complex heat treatment processes, low production yields, and susceptibility to damage during testing, and can no longer meet the frequent testing needs of new high-strength materials and structures.

[0003] The loading pads used in electro-hydraulic servo testing machines undergo significant internal temperature gradients during heat treatment, requiring rapid heating and cooling. When metallic materials experience high-temperature heating with large temperature gradients, residual stress develops, including residual thermal stress due to uneven deformation and residual phase transformation stress due to different phase transformations. This residual stress, combined with working stresses caused by other loads, leads to secondary deformation and redistribution of residual stress. This not only reduces the structure's stiffness and stability but, under the combined effects of temperature and the medium, severely impacts its fatigue strength, resistance to brittle fracture, and resistance to stress corrosion cracking and high-temperature creep cracking.

[0004] To overcome the tendency of spacers to break during use and to meet the design requirements of thicker spacers, traditional spacers are manufactured using high-strength stainless steel with higher strength, thus reducing the risk of breakage during use. However, traditional spacers using higher-strength steel have several serious drawbacks:

[0005] 1. As the thickness increases, the uneven thickness of traditional pads becomes more prominent, and the thickest part is thicker. During heat treatment, it undergoes a phase transformation process, and the temperature gradients at different locations are different, which makes it easier to generate residual thermal stress and residual phase transformation stress, resulting in a reduced service life and a higher risk of brittle fracture.

[0006] 2. Traditional pad blocks overcome the risk of fracture by increasing material strength. As the load and size increase, the material strength requirement increases, which significantly increases the manufacturing cost.

[0007] Therefore, it is necessary to design a new type of loading pad for electro-hydraulic servo testing machines, which should have a lower temperature gradient during heat treatment, lower residual stress, and a longer service life compared to traditional pads when made of lower-cost materials. Summary of the Invention

[0008] To address the problems of existing technologies, this invention provides a novel loading pad for an electro-hydraulic servo testing machine and its heat treatment method. The heat treatment process results in a lower temperature gradient and lower residual stress, thereby improving the service life of the pad.

[0009] The present invention provides a novel loading pad for an electro-hydraulic servo testing machine, comprising a loading pad installed at the chuck of the electro-hydraulic servo testing machine, wherein the loading pad has heat-conducting holes, which are through holes of equal cross-section that penetrate the pad from the side.

[0010] The location of the heat-conducting hole is:

[0011]

[0012] Where H1 is the maximum height of the pad block, and L r Where W1 is the distance between the deepest part of the clamping surface and the front end surface, W2 is the thickness of the upper end of the pad, and D is the thickness of the lower end of the pad. x D is the distance between the heat conduction hole and the end face of the pad. y This is the distance between the heat-conducting hole and the bottom surface of the pad.

[0013] In a further improvement, there are two heat-conducting holes, one located in the middle of the loading pad and the other located at the bottom of the loading pad.

[0014] The present invention also provides a novel heat treatment method for a loading pad for an electro-hydraulic servo testing machine. Several through holes with equal cross-sections are added to the side of the loading pad to form heat-conducting holes. During the temperature change process, the heat-conducting holes form a heat exchange path inside the loading pad, thereby reducing the temperature gradient during heat treatment.

[0015] The temperature change process includes a heating process and a cooling process.

[0016] During the heating process, the heat conduction holes introduce hot airflow from the external thermal environment of the loading pad through convection, increasing the heat transfer area inside and thus increasing the heating rate inside the loading pad.

[0017] During the cooling process, the heat conduction holes introduce low-temperature cooling fluid from the cold environment outside the loading pad through convection, allowing heat to be transferred out through the heat conduction holes and increasing the cooling rate inside the loading pad.

[0018] For pads with different volumes and clamping surfaces, there are different optimal positions, numbers, and sizes to minimize processing and usage stresses and maximize service life. Thermo-structure interaction numerical calculations and thermal conductivity experiments can establish a functional relationship between the position and number of heat-conducting holes and residual stress. Therefore, the residual stress of the pad can be minimized by designing the position, number, and size of the heat-conducting holes.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The heat-conducting holes on the side of the pad guide the heat exchange, thereby reducing the internal temperature gradient of the pad during heat treatment.

[0021] 2. The low temperature gradient during heat treatment reduces residual stress, lowers the material requirements for the pads, and improves the service life of the pads, thus solving the problem of easy damage to pads in large-volume electro-hydraulic servo testing machines.

[0022] 3. The position of the heat conduction holes can be adjusted according to the actual needs of the pad, so as to realize the targeted life design of pads for different purposes;

[0023] 4. The design of the pad for the electro-hydraulic servo testing machine is universal.

[0024] 5. The structure and materials are simple, making it easy to manufacture and install. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a perspective view of the present invention;

[0027] Figure 2 This is a top view and dimensions of the present invention;

[0028] Figure 3 This is a side view and dimensions of the present invention;

[0029] Figure 4 This is the numerical computation grid of the present invention;

[0030] Figure 5 It is a traditionally invented numerical computing grid;

[0031] Figure 6 This is a numerical calculation cloud map of the temperature field on the surface of the present invention during the heat treatment process;

[0032] Figure 7It is a numerical calculation cloud map of the temperature field on the surface of a traditional invention in the heat treatment process;

[0033] Figure 8 This is a numerical calculation cloud map of the temperature field inside the present invention during the heat treatment process;

[0034] Figure 9 It is a numerical calculation cloud map of the temperature field inside the traditional invention in the heat treatment process;

[0035] Figure 10 This is a comparison of the internal temperature of the present invention with that of a conventional invention;

[0036] In the figure, 1-bottom heat conduction hole, 2-middle heat conduction hole, 3-pin fixing hole, and 4-clamping surface. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] like Figure 1 , Figure 2 , Figure 3 As shown, this invention discloses a loading pad for an electro-hydraulic servo testing machine, which is installed at the chuck of the electro-hydraulic servo testing machine. The loading pad includes a clamping surface 4 and a cross-section, on which a pin fixing hole 3, a bottom heat-conducting hole 1, and a middle heat-conducting hole 2 are provided.

[0039] The heat-conducting hole is a through hole with a uniform cross-section that is open at both ends;

[0040] The electro-hydraulic servo testing machine has a groove for mounting pads at the chuck.

[0041] The heat-conducting holes are located on both sides of the pad. In the heat treatment process, during the heating type process, the heat flows through the heat-conducting holes to form a heating zone inside the pad. During the cooling type process, the cooling medium flows through the heat-conducting holes to form an accelerated heat dissipation zone inside the pad. This reduces the temperature gradient inside the pad during the heat treatment process, reduces residual stress during processing, lowers the requirements for materials, and further improves the service life.

[0042] When the heat-conducting holes are in operation, the temperature gradient within a certain range around them is reduced, and the residual stress is reduced. Several heat-conducting holes are located on the side of the pad, on the same plane as the pin fixing holes. Their position, number, and size are determined by both the processing thermal stress and the operating stress.

[0043] For pads with different volumes and clamping surfaces, there are different optimal positions, numbers, and sizes to minimize processing and usage stresses and maximize service life. Thermo-structure interaction numerical calculations and thermal conductivity experiments can establish a functional relationship between the position and number of heat-conducting holes and residual stress. Therefore, the residual stress of the pad can be minimized by designing the position, number, and size of the heat-conducting holes. This invention provides a method for determining the position of heat-conducting holes based on thermo-structure interaction numerical calculation results, as follows:

[0044]

[0045]

[0046] Figure 2 , Figure 3 This is the geometric model and dimensioning of the present invention, where H1 is the maximum height of the pad, and L... w1 L is the width of the bottom of the pad. r W1 is the distance between the deepest part of the clamping surface and the front end surface, W2 is the thickness of the upper end of the pad, and W3 is the thickness of the lower end of the pad. The values ​​of the above geometric dimensions are listed in Table 1.

[0047] Table 2 lists the relevant dimensions of the heat-conducting holes, where D x1 D is the distance between the bottom heat conduction hole and the end face of the pad. x2 D is the distance between the central heat-conducting hole 3 and the end face of the pad. y1 D is the distance between the bottom heat conduction hole and the bottom surface of the pad. y2 φ1 is the distance between the central heat-conducting hole and the bottom surface of the pad, φ2 is the diameter of the bottom heat-conducting hole, and φ2 is the diameter of the central heat-conducting hole.

[0048] Table 1

[0049]

[0050] Table 2

[0051]

[0052] The numerical model is as follows:

[0053] The processing and performance analysis of the loading pad for the novel electro-hydraulic servo testing machine of this invention were conducted using the structural finite element numerical method. The residual processing performance was calculated using a thermo-solid coupling numerical calculation method, and the elastoplastic structural finite element method was used for analysis. A three-dimensional numerical calculation model was established based on the geometric model. Figure 4 The numerical calculation grid for the loading pad block used in the electro-hydraulic servo testing machine of this invention is provided. Figure 5 The numerical computation grid of the traditional invention is presented.

[0054] The numerical model uses either Q3D10MT or DC3D10 meshes with a mesh size of 121858. The surface of the pad is defined as surface convection heat transfer, the ambient temperature is 600℃, and the initial temperature of the pad is defined as 25℃.

[0055] The calculation and analysis results are as follows:

[0056] To compare and analyze the novel loading pad design for the electro-hydraulic servo testing machine, which features lower residual stress and higher fatigue life, a heat transfer analysis of a conventional loading pad for the electro-hydraulic servo testing machine was also conducted. The conventional loading pad for the electro-hydraulic servo testing machine lacks heat-conducting holes in the calculation model, but otherwise shares the same geometric and computational parameters as the novel loading pad. The calculation results show that, under the same specified surface heat convection exchange coefficient and ambient temperature, and using unsteady-state heat transfer calculations, the lowest temperature of the conventional invention is 383.4℃, and the maximum temperature difference is 201.4℃, while the lowest temperature of the present invention is 479.8℃, and the maximum temperature difference is 105.4℃. Figure 6 and Figure 8 The surface temperature and internal temperature during the heat treatment process of this invention are given. Figure 7 and Figure 9 The surface and internal temperatures during heat treatment of traditional inventions are given for comparison. Figure 6 and Figure 7 The surface temperature of this invention is slightly higher than that of conventional inventions; in comparison... Figure 8 and Figure 9 The internal temperature of this invention is significantly higher than that of traditional inventions. Figure 10 This comparison examines the internal temperatures of the present invention and conventional inventions. The comparison reveals that the internal and surface temperatures of the present invention are significantly higher than those of conventional inventions, with a particularly noticeable increase in internal temperature and a significant decrease in local temperature gradients. Therefore, based on the temperature field distribution characteristics and numerical values, it can be qualitatively concluded that the residual stress after heat treatment in the present invention is significantly lower than that in conventional inventions. This greatly reduces the difficulty of heat treatment, simplifies the selection of pad materials, and simultaneously improves the service life of the pads.

[0057] The novel loading pad for the electro-hydraulic servo testing machine of this invention has strong versatility. The above content is only an illustration of the specific implementation of this invention through a typical numerical calculation example. The position, number and diameter of the heat conduction holes can also be adjusted according to actual needs to achieve active design of heat conduction efficiency and solve the problems of large residual stress and easy breakage in use of traditional inventions under various sizes.

[0058] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A heat treatment method for a loading pad used in a novel electro-hydraulic servo testing machine, characterized in that: A loading pad is installed at the chuck of the electro-hydraulic servo testing machine. Several through holes with equal cross-sections are added to the side of the loading pad to form heat-conducting holes. These holes create heat exchange pathways within the loading pad during temperature changes, thereby reducing the temperature gradient during heat treatment. The locations of the heat-conducting holes are as follows: ； in, H 1 represents the maximum height of the pad block. L r The distance between the deepest point of the clamping surface and the front end surface. W 1 represents the thickness of the upper part of the pad. W 2 represents the thickness of the lower end of the pad. D x This is the distance between the heat-conducting hole and the end face of the pad. D y This is the distance between the heat-conducting hole and the bottom surface of the pad.

2. The heat treatment method for the loading pad of the novel electro-hydraulic servo testing machine according to claim 1, characterized in that: The temperature change process includes a heating process and a cooling process.

3. The heat treatment method for the loading pad of the novel electro-hydraulic servo testing machine according to claim 2, characterized in that: During the heating process, the heat conduction holes introduce hot airflow from the external thermal environment of the loading pad through convection, increasing the heat transfer area inside and thus increasing the heating rate inside the loading pad.

4. The heat treatment method for the loading pad of the novel electro-hydraulic servo testing machine according to claim 2, characterized in that: During the cooling process, the heat conduction holes introduce low-temperature cooling fluid from the cold environment outside the loading pad through convection, so that heat is transferred out from the heat conduction holes and the cooling rate inside the loading pad is increased.

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