Withstanding High Levels of Stress
Although plastics are not as hard or rigid as metal, plastic components can withstand relatively high levels of stress if they are specifically designed to do so. To ensure that the material remains reliable for its entire service life, researchers at Bosch use real-life testing procedures and computer simulations to analyze its behavior.
While working on the facade of a house, a workman accidentally drops a battery-powered screwdriver. The hard impact on the tiled floor puts the tool under severe stress. But – as the customer would expect – the screwdriver isn’t damaged in any way. Situations like the one just described are being reproduced in the Bosch research laboratories, using real-life experiments with video recordings of the falling tool and virtual computer simulations. By comparing the real and the virtual images, the researchers can match the simulation models to the real-life processes. And as a result, the simulation can also depict the distribution of stresses and strains in the plastic material, which provides information on weak points in the tool’s design.
The engineers can then strengthen areas in the material that are particularly subjected to stress or make other changes in order to optimize the component’s design. The aim is to optimize a new model’s design early, during the concept phase, making it possible to avoid costly and time-consuming modifications later on. If the impact tests are not conducted until a product has been fully developed, the follow-up costs can be very high indeed if the component fails to measure up.
The researchers at Bosch “cast” their knowledge of materials into physical laws that are then tested and implemented in finite-element software that calculates the component’s deformations when it is subjected to stress. Some of the process steps can only be performed with large amounts of computing power, while others only require the researchers’ expertise and some paper and a pencil.
This was the case, for example, when a low-pressure valve was optimized for a diesel common-rail direct injection system. Knowledge of plastic material behavior, and transferring this knowledge to the component, is accumulated Bosch know-how that enables the creation of a preliminary design. By simulating the strength of the overall design when subjected to pulsating stresses, the researchers found out that it could be manufactured in plastic using an inexpensive, standard injection-molding process. There was therefore no need to a design a back-up solution made of metal. By rounding part of the valve and providing it with additional reinforcements, the component was able to withstand prevailing interior pressures of 10 bars and peak-values of up to 20 bars.
The engineers can then strengthen areas in the material that are particularly subjected to stress or make other changes in order to optimize the component’s design. The aim is to optimize a new model’s design early, during the concept phase, making it possible to avoid costly and time-consuming modifications later on. If the impact tests are not conducted until a product has been fully developed, the follow-up costs can be very high indeed if the component fails to measure up.
The researchers at Bosch “cast” their knowledge of materials into physical laws that are then tested and implemented in finite-element software that calculates the component’s deformations when it is subjected to stress. Some of the process steps can only be performed with large amounts of computing power, while others only require the researchers’ expertise and some paper and a pencil.
This was the case, for example, when a low-pressure valve was optimized for a diesel common-rail direct injection system. Knowledge of plastic material behavior, and transferring this knowledge to the component, is accumulated Bosch know-how that enables the creation of a preliminary design. By simulating the strength of the overall design when subjected to pulsating stresses, the researchers found out that it could be manufactured in plastic using an inexpensive, standard injection-molding process. There was therefore no need to a design a back-up solution made of metal. By rounding part of the valve and providing it with additional reinforcements, the component was able to withstand prevailing interior pressures of 10 bars and peak-values of up to 20 bars.
Drop testing a power screwdriver: The plastic housing and interior components bend upon impact. The researchers compare experiments with the results from computer simulations (superimposed on the lower screwdriver).
