CAFÉ stands for Corporate Average Fuel Economy-- the average miles per gallon on an OEM’s passenger cars and trucks. The standards for passenger vehicles will rise from the national current 27.5 mpg to 35.7 mpg by 2015, while light trucks will go from 23.5 mpg to 28.6 mpg. My next question is how will the OEMs accomplish these figures? Car and trucks will be lighter and smaller, with a greater use of aluminum, plastics, carbon fiber, magnesium and advanced high strength steels (60 percent of all steel in today’s vehicles is AHSS). These exotic materials are the reason that fuel economy will impact body shops.
Aluminum is being used on virtually all makes and models built today, not only on upscale import sports cars. The hood on a Toyota Prius for example is made from aluminum. You will need to invest in new tools and training to work with increasing use of this metal.
Even with an increase in the use of aluminum, the percent of usage is relatively small compared to the use of Advanced High Strength Steels. Steels (AHSS) will pose the biggest problems for repairers and we need to look at the challenges for these steels. The first area is we need to understand is the effect of heat on metal.
Heat applied to mild steel will increase its strength (once it cools). Heat applied to high strength steels will decrease its strength. Heat applied to ultra high strength steels (UHSS) will destroy the steel. Remember these facts.
A couple of other facts that you need to remember: There are two types of energy behavior that we need to recognize when dealing with today’s vehicles. The first one is energy absorption. This is the process of dissipating the energy by the deformation of the part. As the part collapses, energy is lost as it travels from front to back or back to front. This deformation is accomplished by use of laser welds (different thicknesses of metal or different metals attached together with laser welds), collapse zones and reinforcements. Most of the metal on today’s vehicles utilizes high strength steel with MPa (a megapascal is a unit of pressure, which here is a measure of stiffness or tensile strength of materials) ratings between 440 and 590. The second type of energy behavior that we deal with is energy transfer.
The design of energy transfer is to move the energy away from the impact without it deforming. This is accomplished by making the part extremely strong. Many OEMs utilizes ultra high strength steels in the cabin reinforcements (“A” pillar reinforcement, “B” pillar reinforcement and roof and rocker reinforcements). The MPa ratings are 600 and above with some metals reaching over 1400 MPa’s for these metals. You ask the question why are they using these super metals. The answer is simple. The government and Insurance Institute for Highway Safety demanded it. Let’s look at Federal Motor Vehicle Safety Standard 216A.
By the model year the government wanted a 2 ½ times gross vehicle weight to be placed at the “B” pillar, but the IIHS wanted 3 times and by model year 2012, 4 times. What happened was most manufacturers were able to meet the 2012 standards in 2009 and those vehicles received a 5 star rating.
We now need to look at heat and its affect on these metals.
I am going to heat the metal with an induction heater and monitor the temperature with a non contact thermometer. I will take a before and after reading with an instrument to test the strength of steels.
The next part to be tested was a “B” pillar reinforcement from a Volvo XC90. The part is constructed of advanced steel alloyed with boron.
I want to end this with a couple of thoughts.
You will need to invest in an inverter 3 phase spot welders.
You will need to invest in obtaining data for all structural repairs.
You will need to invest in Training,
You will need to invest to be competitive and safe.