Today, we are going to discuss the "List of safety factor guidelines for use in mechanical designHere is a note about "The
In designing the machine,Strength Analysis and perform the following,The designers decide how much safety factor the machine should have for the expected load.However, there is a safety factor that can be used as a guideline for each condition.Today, I will note the general safety factor that can be used as a guide, as well as the process for defining and setting the safety factor that novice designers should be aware of.
Definition of Safety Factor and Setting Process
The definition of the safety factor in machines is simplyRatio of the load (value) that actually stops working to the design value The first two are the following.
(1) Flow of safety factor setting (for beginners in design)
Note the process of setting the safety factor.
The subject matter is destroyed orIt is not possible to know exactly when it will stop working properly or the load at that time.Therefore, we designers set the maximum anticipated load and design the equipment and structure with a factor of safety.There are two important things to consider when calculating that safety factor.
- How accurately do you know the status of the object?
- Is the assumed load appropriate when looking at the safety factor?
That is to say.
The first point,How accurately do you know the status of the object? But, for example.The amount of information obtained from manual calculations and CAE (computer simulation) is different.
- CAE calculations are more accurate than manual calculations in terms of stress loading.
- Center of mass can be calculated more accurately by CAD than by hand calculation.
The first important point is to know as much as possible about the situation of the object for which the safety factor is to be set.
Second, the second point.Is the assumed load appropriate when looking at the safety factor? We will look at the following. Our designers will basically set up the following
- For single materialhas a general safety factor based on the environment (static, repetitive, etc.)
- For drive systems has a safety factor that takes into account unexpected loads
- Other cases sets the empirical safety factor
Like this,The process of understanding the condition of the object and setting the safety factor for the assumed load. Therefore, it is not a good idea to set a safety factor of 100 times for all of them.
(2) Two safety ratio guidelines
There are two general guidelines for setting the safety factor.
- Safety to function ratio
- Safety factor for materials
It is.
(1) Safety factor for function
A machine is a single object composed of a number of elements.To determine the safety factor of a machine, it is important to understand the function of the target object in the overall machine and to determine the degree of failure.It is.
Quote: Define the function to be fulfilled in the machine.
Determine the safety factor according to the damage that would occur if the function were to stop functioning. Taking a large safety factor for a part that will not be affected even if it breaks down will only increase costs and is wasteful.
(1) If that function is broken, it will lead to a serious disaster. 5 or more is expected.
If that function is broken, the machine will be totally damaged and the line will be stopped.
If that function breaks, the machine will stop and the line will pause. 1.5 or higher is expected.
If that function is broken, it will stop safely with minimum functionality. 1.2 or higher is expected.
(5) If the function is broken, the alternative function will work. 1.1 or higher is expected.
(6) It does not matter if that function is broken. 1.0.
(7) The area to be destroyed as a priority when there is a problem. It should be the smallest compared to other areas.
The above is summarized in a very understandable way.This is the safety factor expected from the degree to which a failure occurs.
Typical examples include drive systems, stoppers, etc.If a function breaks down, it can lead to a serious disaster, it is necessary to take a larger safety factor. This is understood to be the case.However, the above is a safety factor against breakdown of functionality, which is in addition to the above.Is it a manual analysis? and ... andDid you perform a CAE analysis? It is necessary to vary the degree in such areas as
Considering these factors, the final configuration is as follows
(ii) Safety factor for materials
The general safety factor for materials is shown below. This information is widely used.
When determining the safety factor for a material, if there are no actual results, the above should be used as a guide or reference. If there are actual results or test results, the safety factor should be set based on that information.
Finally.
The safety factor is a design indicator to avoid the worst-case scenario. Ideally, the safety factor should be kept as large as is appropriate for the cost and volume of the equipment, but it is important to
- Ensure that the current situation is properly understood (using CAE and CAD)
- Don't make a mistake or forget where to evaluate.
- Do not make the mistake of using the wrong method of evaluation.
I think these three are important in setting the safety factor.
Sources (list)
In addition, the following sources were used for this memo (thanks)
Download Table
That's it.
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Basic calculations
This section contains notes on the basic calculations for mechanical design that I use in my practice. The articles with calculations and the calculations are revised as needed, so please use the latest version when using them. If you have any questions, please feel free to contact me.
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