A method for designing a connection thread resistant to complex sea condition cycles and impact stresses

Abstract

The application discloses a connecting thread design method resistant to complex sea condition cycle and impact stress, comprising the following steps: establishing a model of a mechanical device, determining thread distribution, and giving the number of common threads and hinge hole threads; determining axial load and tangential load borne by the device; determining yield strength of material allowable according to the characteristics of selected material; calculating shear resistance contribution coefficient of common threads; calculating thread dangerous section; and selecting thread size. The application combines three types of formulae, i.e. isolated shear checking calculation, tensile checking calculation and compression checking calculation in thread strength checking in a mechanical design manual, through a coupling formula, so that the matching of thread specification and shipborne use environment requirement can be quickly and effectively solved. The application is suitable for the calculation of thread connection strength of marine equipment.

Description

Technical Field

[0001] This invention belongs to the field of structural design of shipborne electronic information systems. Background Technology

[0002] Threaded connections are widely used in mechanical devices due to their advantages such as low cost, easy assembly and disassembly, and high connecting force. Thread strength verification typically follows methods recommended in mechanical design manuals, calculating the critical section of the thread for axial, tangential, bending, and impact loads. This process is time-consuming and prone to overlooking certain loads. Threads designed to withstand complex marine conditions do not bear loads from a single source but often experience multiple superimposed loads, including wind loads, inertial loads, gravity loads, cyclic stresses, and impact loads. Ignoring the thread's loading state under multiple loads often leads to a mismatch between thread specifications and actual requirements. This can result in either over-designed reliability or undersized threads, leading to loosening, breakage, and economic losses during use. Summary of the Invention

[0003] To address the issue of matching thread specifications with the requirements of marine operating environments, prevent over-design leading to increased equipment weight, and avoid equipment damage accidents caused by neglecting certain loads, this invention proposes a connection thread design method that can withstand complex sea conditions and impact stresses.

[0004] To achieve the above-mentioned technical objectives, the technical solution of the present invention includes:

[0005] 1. Establish a model of the mechanical device, determine the thread distribution, and specify the number of ordinary threads and reamed hole threads;

[0006] 2. Determine the axial and tangential loads that the device will bear;

[0007] 3. Determine the allowable yield strength of the material based on its characteristics;

[0008] 4. Calculate the shear contribution coefficient of ordinary thread;

[0009] 5. Calculate the critical section of the thread;

[0010] 6. Select the thread size.

[0011] Furthermore, the shear contribution coefficient λ of the ordinary thread includes:

[0012]

[0013] Where C1 = 1.656S1, C2 = 1.656S2, and Z1 and Z2 are the number of ordinary threads and reamed hole threads; F R FQ S1 and S2 are the tangential and axial loads borne by the connecting threads; S1 and S2 are the safety factors for tensile stress and shear stress, respectively.

[0014] Furthermore, the formula for determining the critical section of the thread includes:

[0015]

[0016] Among them, K f σ is the reliability coefficient of the friction coefficient, where μ is the friction coefficient; s It is the yield strength of the material.

[0017] Based on the calculated critical section d of the thread, select a suitable thread size from the preferred thread series.

[0018] This invention organically combines the three isolated shear strength verification calculations, tensile strength verification calculations, and compressive strength verification calculations in the thread strength verification of mechanical design manuals through a coupling formula. It can quickly and effectively solve the matching problem between thread specifications and the environmental requirements of marine equipment, avoiding both the increase in equipment weight due to over-design and the equipment damage accident caused by ignoring certain loads. Attached Figure Description

[0019] Figure 1 Flowchart for the design of connection threads to withstand complex sea conditions;

[0020] Figure 2 This is the design diagram of the antenna for this example;

[0021] Figure 3 Design drawing for a standard connection thread;

[0022] Figure 4 Design drawing for threaded connection of reamed hole.

[0023] As shown in the figure: 1. Reamed hole connection thread assembly, 2. Ordinary connection thread assembly, 3. Equipment of an electronic information system, 4. Skeleton. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0025] Figure 2 The diagram shows the design drawings of a preferred embodiment of the antenna of this invention. The antenna is flange-mounted onto a frame and rotates in azimuth along with the frame. This antenna is an open-air marine device; while rotating in azimuth, it must withstand wind loads and participate in the swaying and heaving motions along with the vessel.

[0026] To obtain a thread specification that matches the requirements of the shipboard operating environment, the preferred embodiment of the present invention includes the following steps:

[0027] Step 1: The mounting flange of the antenna in this example is designed with 22 ordinary threaded through holes (Z1=22) and 4 reamed threaded through holes (Z2=4).

[0028] Step 2: Convert the cyclic stresses and impact loads borne by the antenna, such as wind load, inertial load, rotational load, and gravity load, into forces in two directions: axial force F along the thread axis. Q =341901N, tangential force F along the radial direction of the thread R =275276N.

[0029] Step 3: Determine the shear contribution coefficient of ordinary thread as follows: According to the formula C1 = 1.656S1 and C2 = 1.274S2 are determined. Where S1 and S2 are the safety factors for tensile stress and shear stress, respectively. Preferably, S1 = 1.2 to 1.5, and in this example, 1.5 is taken, and S2 = 2.5.

[0030] Step 4: According to the formula Determine the critical section of the thread. Wherein, K... f =1.2; μ=0.1; σ s =865MPa.

[0031] Step 5: Calculate d≥18.3mm, and select 20mm thread as the design value from the preferred thread series.

Claims

1. A method for designing connecting threads that can withstand complex marine cycling and impact stress, characterized in that: Step 1: Build a model of the mechanical device, determine the thread distribution, and specify the number of ordinary threads and reamed hole threads; Step 2: Determine the axial and tangential loads that the device will bear; Step 3: Determine the allowable yield strength of the material based on its properties. ; Step 4: Calculate the shear contribution coefficient of ordinary thread, wherein the shear contribution coefficient of ordinary thread... The determination includes: ； in ; This represents the number of standard threads. The number of threads in the reamed hole; The tangential load borne by the connecting thread. The axial load borne by the connecting thread; The safety factor for tensile stress, The safety factor is the shear stress. It is the reliability coefficient of the friction coefficient. It is the coefficient of friction; Step 5: Calculate the critical section of the thread. The determination of the critical section d includes: ； Step 6: Select the thread size.

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