Recent production vehicles (VW, Toyota and Ford, for example) have been able to parallel park all by themselves. This technology has unfortunately come about largely by necessity, as standards for driver ability, particularly in the US, have degraded to dangerous levels; however, the technology itself is fantastic and will both improve driving safety and fuel economy in drastic ways in the years to come.
Let’s take a look at one of the most basic parameters necessary in analyzing a structure’s ability to handle bending loads: the moment of inertia.
Remember that a moment is simply the effect a force has on a single point. Consider the scenario of a person placing a wrench on a bolt and applying a force to the end of the wrench handle. Such a force creates a moment about the center of the bolt head.
Now consider the cross-section of the actual wrench handle. By applying a force to the end of the handle, the handle experiences a bending load.
The moment of inertia about an axis of bending indicates its ability to resist such bending. This applies to many stuctures – trusses, beams, boards, etc. Think about a martial artist breaking a wooden board or stack of bricks. Have you ever seen anyone strike the narrow end of a structure standing on end? Of course not – this is because the moment of inertia is far too high around that axis. Rather, the board or bricks are always struck on the flat side where the moment of inertia – the structure’s ability to resist bending – is lowest. Read the rest of this entry »
But the question remains – Are the manufacturers developing electric technology quickly enough? If you asked the pupils at DeLaSalle High School (Kansas City, Missouri), I think the answer would be a resounding “no.” Students from DeLaSalle’s extra-curricular Automotive Design Studio, with the assistance of faculty and undoubtedly some Bridgestone engineers, have developed an electric vehicle with the gasoline efficiency equivalence of 300 miles per gallon. Not too bad for some high-schoolers. It will be interesting to see how automotive technology continues to develop and accelerate. Here are the pictures of DeLaSalle’s electric car, courtesy of ZeroCustoms via Inhabitat.
Have you ever pulled some Stainless Steel (SS) flatware out of the dishwasher only to find some rainbow-colored corrosion spots on them? Or perhaps most of your flatware comes out fine but your knives come out spotted?
There is an explanation. Most SS flatware is marketed in the US using the European designations of 18/10 or 18/8. The first number here represents the percentage of Chromium and the second number represents the percentage of Nickel, so 18/10 contains 18% Chromium and 10% Nickel. The 18/8 is trickier. Some flatware sets can be made entirely of 18/8 (i.e., forks, spoons and knives are all 18/8); however, it is increasingly common to see flatware referred to as 18/8 when the the forks and spoons are actually 18/10 and the knife is 18/0. They just sort of average out the Nickel content and come out with 18/8 even though not a single utensil in the set, strictly speaking, is made out of 18/8. The reason knives are sometimes made of 18/0 is that Nickel softens the alloy and knives need to be harder to keep an edge. The down side is that when you put your flatware in the dishwasher (particularly with certain types of detergent) is could come out with the early signs of corrosion – the iridescent, rainbow-like spots your wife sees and gets upset about. It is especially common on knives. Read the rest of this entry »
This post will not directly address welding but rather will explore some of the relationships between ductile and brittle materials. The significance to welding is that many of the conditions which can cause brittle failure of ductile materials can be introduced by welding.
Some materials are inherently brittle while others are ductile in nature. You should be familiar with these Stress-Strain plots:
Materials are generally considered brittle if they fracture at less then 5% elongation when stressed. A metal’s ductility is largely a function of its microstructure. For example, a steel with a Body Center Cubic (BCC) microstructure (first image, below) is more ductile than a material with a Face Centered Cubic (FCC) microstructure (second image, below). This is because the FCC microstructure is more restrained:
Read more about the binary phase relationship between iron and carbon to understand how the forming of a steel, the cooling rate, percentages of carbon and other factors affect a steel’s microstructure and ductility. Read the rest of this entry »