| FoamTech |
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| Written by Administrator |
| Saturday, 20 June 2009 23:58 |
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FOAMTECH REFERENCES OTHER REFERENCES Is there Empirical Evidence to show ?
For those of us who are professional engineers, US has a technical automotive professional community known as SAE (Society of Automobile Engineers). Basically it's a society that was created in the 1900s in the US to ensure all the engineering know-hows, R&D work performed are recognized and documented etc …. SAE has since evolved to cover the automotive, aeronautical, aerospace and motorsports industries as well. Some many months ago, I borrowed a copy of a SAE Technical Paper ref. 1999-01-1785 "Effect of Polyurethane Structural Foam on Vehicle Stiffness" - This technical paper was lodge in 1999 by Daimler Chrysler. Basically they insert automotive foaming a Mercedes and Chrysler SUV to study on the effects of AF treatment on structural rigidity / integrity as well as vehicle stability etc and used different foam density as well. The scientific method used to study this is called "modal frequency" behavior by placing at different structural points and different foam densities to study the structural integrity of the body chassis and measuring the natural frequency of the body under various test conditions. http://www.sae.org/technical/papers/1999-01-1785 Stability and structural integrity are extremely important in the design of a vehicle. Structural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and structural benefits. This study involves modal testing and finite element analysis on a sports utility vehicle to understand the effect of structural foam on modal behavior. The modal analysis studies are performed on this vehicle to investigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam density and placement in the body influences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the sensitive joints in the body structure and to minimize the number of design variables in the DOE study. Daimler Chrysler Report Findings (doc ref. 1999-01-1785) Before I start this is the physics explanation to it "Natural Frequency of a body is square root of stiffness of the body over mass of the body." The higher the natural frequency, the stiffer is the body. The mathematical formula is as follow - Fn = (K/m)^(1/2) , where K = stiffness coefficient of the body, m = mass of the body & Fn is natural frequency Abstracts of the Report : Stability and structural integrity are extremely important in the design of a vehicle. Structural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and structural benefits. This study involves modal testing and finite element analysis on a Sport utility vehicle to understand the effect of structural foam on modal behavior. The modal analysis studies are performed on this vehicle to investigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam's density and placement in the body influences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the sensitive joints in the body structure and to minimize the number of design variables in the DOE Study The most sensitive area of the body were found to be the A-pillar, the D-pillar and their joints. With structural foam injected into this sensitive areas, the vehicle body was significantly stiffened, as shown by the increase in modal frequencies. The 1st torsional mode was most effected with an increase of 29.1% in modal frequency. The design sensitivity analysis and design of experiments described here, can be used to identify the sensitive ares of the body structure. This results are useful in the determining the best application locations for structural foam. Here are some scanned sections of the said report...   If u are still interested, there are other SAE papers. Here are the links if you want to find out why AF treatment is not used on normal production lines... http://commercialvehicle.sae.org/technical/papers/2003-01-1569 http://commercialvehicle.sae.org/technical/papers/1999-01-0586 http://www.sae.org/automag/globalview_03-00/04.htm http://www.patentstorm.us/patents/7160491-description.html
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| Last Updated on Sunday, 21 June 2009 16:25 |
