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SO-Technology

Welcome to my homepage of SO-technology!

In this homepage, various information on tightening technology,

lecture for strength of material and the strength evaluation technology of a structure

is offered.

Moreover, I do guidance of consulting and technical seminar

about those technology.

Tightening Technology

(Optimum tightening on bolted joints and the prevention technology for self-loosening and breakage)

Bolted Joint (screw thread) is used in many industrrial commodities, such as cars, construction machinery, industrial trucks, general machinery, electrical machinery, and electrical devices, airplanes, and plant equipment, and has played an important role as the machine part. The spiral function was utilized in pumping technology and dyeing technology back in 6-4th century B.C. And the pursuit of a screw princple had also started. In spite of its over 2000 years' long history as the machine element, trouble such as poor bolting, self-loosening and insufficient strength occur even today.

Why does the bolted joints(screw) trouble still occur?

Why does it continue to be considered machine parts requiring

special attention?


Because it has problems as shown below.

(1) It is always used at high stress. It is subjected to vibration

and repeated external force.



(2) Although high iniial axial tension (clamping force) is needed.

There is no simple tool. therefore, calribrated wrench method

must be used in general.



(3) Ther are many kinds of bolts/screws (coarse/fine screw

thread, strength grade classification, etc.).



(4) Breakage of screw threads and damage through defomation


(cross-sectional reduction) may be caused by tightening work.


(5) High stress concentration areas exist in the underhead fillet


part and a threaded portion, etc.




(6) Fatigue breakage, hydogen embrittlement, etc. occur during machine operation.



(7) Self-loosening easily occur due to the spiral shape and is

influenced by depression of bearing surface.




(8) many bolted joints are used in one product.

If interested, please send e-mail to me without reserve

as is shown below.


hare-lab@ivy.ocn.ne.jp

Hareyama's Paper

Author : Soichi Hareyama , Dr.Eng

Menber of Tokyo Metropoltan University

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