A Method of Determining the Equivalent Static Load of Shock Load

An impact load and static load technology, applied in the direction of elasticity test, machine/structural component test, force/torque/work measuring instrument, etc., can solve the problems of excessive safety factor, lack of theoretical basis, conservative design, etc. The theoretical basis is sufficient, the application scope is wide, and the effect of improving the authenticity

Active Publication Date: 2019-12-24
XIAN AIRCRAFT DESIGN INST OF AVIATION IND OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantage is that this method lacks a rigorous theoretical basis, and the solution formula of the dynamic scaling coefficient adopts approximate values, and all of them are greater than 1
Therefore, the equivalent static load obtained by using this method is always greater than the peak value of the impact load, which makes the safety factor too large, resulting in a conservative design

Method used

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  • A Method of Determining the Equivalent Static Load of Shock Load
  • A Method of Determining the Equivalent Static Load of Shock Load
  • A Method of Determining the Equivalent Static Load of Shock Load

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0094] Taking a beam structure as an example, the implementation process of determining the equivalent static load of impact load based on this method is explained.

[0095] 1. Establish the finite element model of the beam structure

[0096] Figure 6 A schematic diagram of a beam structure is shown. The beam is 2m long and forms an included angle of 45o with the negative direction of the OY axis. The cross section is a straight ring with an outer diameter of 0.05m and an inner diameter of 0.04m. The material is alloy steel, the elastic modulus of the material is 200GPa, the Poisson's ratio is 0.3, and the density is 7800kg / m 3 . A linear spring is arranged at 1 / 10 of the end of the beam close to the origin O, which only provides stiffness in the Y direction and is used to adjust the bending frequency of the beam around the OZ axis. The finite element model of the structure is established by MSC.PATRAN.

[0097] 2. Calculate the natural frequency of the finite element mo...

Embodiment 2

[0115] Taking the water load measurement test of ditching on a scale model of a certain type of aircraft as an example, the process of determining the equivalent static pressure of ditching based on this method is illustrated.

[0116] 1. Determine P and T D

[0117] Figure 8 The pressure time history of a certain place on the fuselage obtained from the test side is shown. It can be seen that the first impact pressure peak value P=900kPa. according to Figure 5 The method shown to determine T E = 0.006s, therefore, the duration T D =2.5T E = 0.015s.

[0118] 2. Determine f n

[0119] According to the aircraft ground resonance test, the first-order natural frequency of the fuselage can be obtained as 9Hz, so f n = 9Hz.

[0120] 3. Calculate the dynamic scaling factor λ

[0121] dimensionless parameter f n T D =0.848, the dynamic scaling coefficient λ=0.415 obtained according to formula (20).

[0122] 4. Calculation of equivalent static pressure

[0123] Equival...

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Abstract

The invention belongs to the structure and equipment impact resistance design technology field and relates to a method of determining an impact-load equivalent static load. The method comprises the following steps of step1, according to the following formula which is defined in the description, calculating a dynamic scaling coefficient lambda, wherein TD is duration of an impact load, and fn is a fundamental frequency of a structure to be impacted; and step2, according to the following formula, calculating an equivalent static load Ps of the impact load, wherein the formula is Ps=lambda P, and the P is a peak value of the impact load. A lambda value acquired through calculation in the scheme can be greater than and less than 1 according to a change of TDfn, which is really equivalent to the impact load, and a truth degree of the equivalent static load is increased.

Description

technical field [0001] The invention belongs to the technical field of anti-impact design of structures and equipment, and relates to a method for determining the equivalent static load of an impact load. Background technique [0002] The equivalent static load refers to the equivalent static load for equipment and structures that are inconvenient or even impossible to directly perform impact simulation or test, so as to provide input for equivalent static simulation or test of impact. [0003] The document "Structural Design Method Under Impact Load" (Missile and Space Launch Technology, Issue 3, 2007: 33-37) gives a formula for determining the equivalent static load of impact load: [0004] [0005] In the formula: T D is the impact load duration; ω n is the natural circular frequency of the system; λ is the dynamic scaling factor, defined as the equivalent static load P s Ratio to the peak value P of the shock load: [0006] [0007] When the natural circular fr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01L5/00G01M5/00
CPCG01L5/0052G01M5/0075
Inventor 张玉杰冯震宙黄超广
Owner XIAN AIRCRAFT DESIGN INST OF AVIATION IND OF CHINA
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