A few weeks ago, I talked about the sore points (decubitus) when patients are lying down. But pressure points do not only occur in old age.
I have been told that there can also be considerable differences in the comfort of wearing a bra.
I learned that the custom of covering and supporting breasts is already 4,500 years old and that today there are many different types of bras.
In the following we will look at a modern variation from a numerical point of view, the so-called underwired bra.
Let us let technical expertise have its say, even if it is thematically difficult.
In the new versions, a support bracket punched from sheet metal is used to support and shape the bust, ensuring that the appearance of the wearer leaves nothing to be desired. When facing inwards, it should not cause any pain due to pressure points. Especially under the armpit it should not pinch. Ideally, the woman should not feel the bra at all, while everything remains in perfect shape even when moving. In the language of the stress engineer, this means that the load on the chest is supported as evenly as possible, as is the case with an elastic bedding. The contact pressure should be constant everywhere. The shape is a matter of taste, but can be quite similar to a waitress in a dirndl.
How can the simulation help here?
Here, too, the experiment should be conducted virtually, at least during the development phase of the wire.
For this we need
- A torso with cup size B (scanned model, let us call her Monika)
- A bra model, also size B
- A suitable FEM simulation software, e.g. Abaqus
- A material model for fat tissue within the tolerance range (14 years to 70 years)
- An experienced stress engineer with a sense for aesthetics
The first problem occurs already during scanning. Our test-breast is a system pre-stressed under its own weight, for which we do not know the boundary conditions (internal stresses). Scanning in weightless space is possible in principle, but at this stage of earthly development it exceeds the existing budget of our customer a bit.
It is therefore an ingenious idea to generate weightlessness in a first load step in which the gravitational vector is directed upwards. All stresses and deformations are now set to 0. And lo and behold, we have the stress-free FEM-breast without the influence of the annoying gravitation.
Now the assembly simulation follows (attaching the bra, pretensioning the straps).
In a further step, the actual loading by the downward directed gravitational vector follows.
Pressure points can now be detected and optimized by means of variant studies of the bra. But this is the less exciting part of the project, which I do not want to go into further.
What can we learn from the project?
The simulation can also help the apparel industry to develop products faster and more efficiently. Fabrics, elastics, interlinings, foams, can all be controlled. Although the test with test wearers has its attractions here, it becomes laborious if new hangers have to be constructed, lasered and subjectively evaluated on the basis of the day-dependent shape and mood of the test subjects with every change in geometry.
How much more convenient for the development engineer is the average contact pressure and the standard deviation along the temple line. Two values that his optimization algorithm understands and to which he can thoughtlessly optimize. Also, the number of webs, width, angle and length are only parameters for which an optimum must be found.
What is on your mind?
Is the jacket too tight (unfortunately I know it too well)? Maybe it will take a few more years before you can have your tailor-made suit fitted to your virtual twin via the Internet. But we are not that far away from that.
If you have any ideas on how you would like to shamelessly use our know-how for your tasks, please contact us. We are looking forward to your inquiry.
Yours Stefan Merkle