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kenzo_yamamoto9-Granite
9-Granite
January 19, 2017
Question

I am interested in the analysis of the screw.

  • January 19, 2017
  • 2 replies
  • 1607 views

I am a 70 year-old engineer.
At present, I am interested in the analysis of the screw.
Because, I have the doubt that why the wheel bolt of the large truck is broken.
According to the analysis of myself, I came to the following conclusion.
That is, there is a problem in the thing with very short bolt length.
The bolt length is length from the seat surface of the bolt to the 1st pile of Nut’

s.
Therefore, I inquired to the expert about this estimation, but I have not got in the

answer which is appropriate for now.
Moreover, there are individual standards such as the screw, the bolt and Nut, but I

feels that there is not a standard about the application.
Therefore, I have thought that I posted a message to this place and I would like to

hear an opinion.

Question 1
Let me know if there is a standard about the way of using to the bolt and Nut.
( Ex. ) The company design standard :
It is necessary that the bolt length is longer than half of the bolt diameter size.

Question 2
According to my analysis, the problem occurs when bolt length is short extremely.
That is, the screw is easy to loosen.
Also, if the screw loosens once, it develop into the fatigue destruction.
Then, the wheel bolt broke.
I want to ask the opinion about my reasoning.


Question 3
Let me know if there is literature which was analyzed about the screw.
For the literature on the recent screw in Japan, there are the literature of FEM

(Ansys)analysis about the looseness of the screw.
Let me know if there is literature which was analyzed in Nastran of PTC.

2 replies

Chris3
Chris321-Topaz I
21-Topaz I
January 20, 2017

There are entire books written on bolted joint analysis. It is impossible to answer your questions here in a couple of sentences. There are many variables such as the stiffness of the members you are clamping, the external loading, what lubrication is being applied, how many loading cycles there are ... etc.

Too answer your last question, yes PTC software can perform bolted joint analysis.

I would suggest reading through the following links as a starter:

NASA 5020 Bolted Joint Analysis

Using Fasteners in Creo Simulate

Other was to simulate bolted joints in Simulate

An Introduction to the Design and Behavior of Bolted Joints

T
TomD.inPDX17-Peridot
17-Peridot
January 20, 2017

There are some very obvious issues with short bolts but ultimately, it depends on the interface.

The most glaring issue with a short bolt over a long one is engagement.

In industry, a bolt only needs 3 complete threads in its mate.

Using that, a short bolt has much greater strain influence than a bolt that is significantly longer.

This requires a little faith to understand, but if you think about it as the location of the -head- of the bolt,

you will see that a shorter bolt is gyrated much more if the hub were to be loose (including plastic deformation).

Longer engagements in the mating threads reduces the available angle that the screw can gyrate.

However, you have to weigh this with stiction on the mounting flange.  This is what reduces sheer at the threaded interface.

A more interesting question is, what is the margin provided by the manufacturer.

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