JPH09291919A - Method for evaluating fastening force of bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating a fastening force of a bolt which method enables a simple evaluation of the fastening force of the bolt with good precision. SOLUTION: A bolt is fastened while applying a compression load P to a bolt. From a torque T which is required for the fastening of the bolt, a friction coefficient between a male screw (1B) of a bolt and a female screw (3A) of a mother material, and a friction coefficient between the bolt head (1A) and the base surface (2A) of the fastening material are determined. A friction loss is determined from a relation between a torque required before the start of the fastening of the bolt and the compression load by fastening the bolt while applying the compression load to the bolt so that the fastening force of the bolt can be simply evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a tightening force of a bolt when tightening a mechanical part or a structural member with the bolt.

[0002]

2. Description of the Related Art A conventional method for evaluating the tightening force of a bolt is a strain gauge embedded in the bolt.

[0003]

The conventional bolt tightening force evaluation method has a problem in terms of price because a special bolt is required. In addition, each bolt requires electrical wiring, which requires a great deal of labor.

An object of the present invention is to provide a method for simply and accurately obtaining the tightening force of a bolt.

[0005]

[Means for Solving the Problems] The bolt (1) is tightened while applying a compressive load P to the bolt, and from the torque T required for tightening, the male screw (1B) of the bolt and the female screw (3) of the base material
A method for evaluating a tightening force of a bolt, which comprises determining a coefficient of friction between the bolt head (1A) and a seat surface (2A) of a material to be tightened.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION When the bolt 1 is screwed in while applying a compressive load P to the bolt 1, until the bolt head (1A) and the seat surface (2A) of the material to be tightened come into contact with each other (FIG. 1), the bolt 1 is screwed in. The required torque T is required for friction between the male screw (1B) of the bolt and the female screw (3A) of the base material.

At this time, the friction coefficient between the male screw (1B) of the bolt and the female screw (3A) of the base material is determined from the relationship between the magnitude P of the compressive load and the magnitude T of the torque required for screwing. can do.

The bolt head (1A) and the seating surface (2) of the material to be tightened
Immediately after contact with (A) (Fig. 2), the male screw (1
B) and the female thread (3A) of the material to be tightened are in a non-contact state for a moment due to the play of the screw (Fig. 3), and the torque T required for screwing is the bolt head (1A) and the material to be tightened. Seat (2
Required for friction with A).

From the relationship between the magnitude P of the compressive load and the magnitude T of the torque required for tightening at this time, the bolt head (1A)
It is possible to determine the friction coefficient between the seating surface (2A) of the tightened material.

From the coefficient of friction between the male thread (1B) of the bolt and the female thread (3A) of the base material and the coefficient of friction between the bolt head (1A) and the seat surface (2A) of the tightened material, After the bolt starts to be tightened, the ratio of the torque required for tightening to be lost due to friction is obtained, the torque required for tightening the bolt is clarified, and the tightening force of the bolt can be evaluated.

[0011]

Example A hexagon bolt of M12, pitch 1.75 metric coarse screw was screwed in at a rotation speed of 30 rpm while applying a compressive load. The bolts, tightened material and base material were all stainless steel. (1) No lubrication between the bolt head and the seat surface of the tightened material, and between the male screw of the bolt and the female thread of the base material, (2) between the bolt head and the seat surface of the tightened material Oil lubrication, no lubrication between the male thread of the bolt and the female thread of the base material, (3) no lubrication between the bolt head and the seat surface of the tightened material,
Oil lubrication between the male thread of the bolt and the female thread of the base material, (4) Oil lubrication between the bolt head and the seat surface of the tightened material, and between the male thread of the bolt and the female thread of the base material, 4 experiments were performed. The base material was fixed to the load cell, tightened in a state where the material to be tightened and the base material were not in contact with each other, and the tightening force by the bolt was tested. The measured value of the tightening force and the predicted value using this evaluation method were in good agreement.

[0012]

When assembling a machine in a factory, oil is applied when the bolts are tightened or the lubrication state changes depending on the situation, and even if the bolts are tightened with the same torque, the tightening force of the bolts greatly differs. When assembling the pressure vessel with bolts, tension exceeding the design value acts on some of the bolts due to the imbalance in the tightening force between the bolts, which may cause damage. In addition, a bolt that receives a fluctuating load has a problem of breaking due to metal fatigue when a tightening force less than designed is applied. According to the method for measuring the tightening force of the bolt of the present invention,
The bolt tightening force in an arbitrary lubrication mode can be easily obtained with high accuracy, and a remarkable effect of solving these problems at once can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram before a bolt head (1A) of this embodiment contacts a seat surface (2A).

FIG. 2 is an explanatory diagram immediately after the bolt head (1A) of the present embodiment comes into contact with the seat surface (2A).

FIG. 3 is an explanatory view showing that the male screw (1B) of the bolt and the female screw (3A) of the base material are in a non-contact state immediately after the bolt head (1A) of this embodiment contacts the seat surface (2A). is there.

[Explanation of symbols]

 1 Bolt 2 Non-tightened material 3 Base material

Claims (1)

[Claims] 1. The bolt is tightened while applying a compressive load to the bolt, and the torque required to tighten the bolt, the coefficient of friction between the male thread of the bolt and the female thread of the base material, and the bearing surface of the bolt head and the tightened material. A method for evaluating the tightening force of a bolt, characterized by determining the coefficient of friction between and.