Calculation difference between test machine pressure and tensile force test

Calculation difference between test machine pressure and tensile force test

As early as the use of ancient springs, Jinan Hengsi Shanda Instrument Co., Ltd.Tension testerThe calculation standards of spring tensile test and pressure test are summarized in detail, and the following are for customers to understand:

The specific design steps for tensile springs and pressure springs are: first, try to select spring material and spring index C according to working conditions, requirements, etc. Since sb is related to d, the diameter d of the spring wire is often assumed in advance. Next, calculate the values ​​of d and n and the corresponding other geometric dimensions. If the obtained results do not match the design conditions, the above process must be repeated. Until a solution that satisfies all constraints is obtained is a feasible solution to this problem. In practical problems, feasible solutions are not available, and it is often necessary to find better solutions from multiple feasible solutions. The task of spring design is to determine the spring wire diameter d, the working circle number n and other geometric dimensions, so that the strength constraints, stiffness constraints and stability constraints can be met. Furthermore, corresponding design indicators (such as volume, weight, vibration stability, etc.) are required to achieve.

A cylindrical spiral compression spring is designed with the cross-section of the spring wire being circular. It is known that small load Fmin=200N, load Fmax=500N, working stroke h=10mm, spring Class II work, the outer diameter of the spring is required to not exceed 28mm, and the ends are tightly polished and flat.

Solution: Trial calculation (1):

(1) Select spring material and allowable stress. Choose C-class carbon spring wire.

According to the requirements of the outer diameter, the primary selection is C=7, and from C=D2/d=(D-d)/d, d=3.5mm, from Table 1, sb=1570MPa, and from Table 2, it is known that [t]=0.41sb=644MPa.

(2) Calculate the spring wire diameter d

From the formula, we get K=1.21

From formula, we get d≥4.1mm

From this we can see that the initial calculated value of d=3.5mm does not meet the strength constraints and should be recalculated.

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