Smokey once told me that when Chevrolet first asked him to evaluate the then-new, 265-inch small-block Chevy engine for racing purposes, he told them he'd first need to "break everything that was breakable" in order to figure out what needed fixing or redesigning to make the engine live in a racing environment. They agreed, he did and history began to unfold. But I also know that in the process of pursuing this approach, he applied many of the basics found in the fundamentals of analyzing materials, their properties and characteristic qualities. Because this is an area not often covered in publications like CT, we thought it time to share a few of these basics, inasmuch as more and more technologies are trickling down from the aerospace community into motorsports. So buckle up for a slightly different type of ride this month.
In its broadest sense, the subject deals with what we'll categorize as a study of the "strength of materials." We will briefly examine such topics as stress, strain, elasticity, elongation, tension and compression, among other related fundamental conditions. And on the chance you're already wondering why any of this may be of value to a race engine builder or parts modifier, let's just say that unless you have a sense for how parts (as built or, in particular, as modified) could have their durability decreased or improved upon, you may be working in the dark, so to speak. Perhaps more importantly, if you are to understand why certain contemporary methods derived from aerospace (for example) are applicable to racing parts, knowing how they may improve parts performance and life requires some background in the analysis of materials. That should be a sufficient preamble. Let's now get to the business at hand.
By definition, stress is a force applied by one body on another (often external to the body in stress) or by one body on another. If it is the second of these conditions, the result is called an internal stress. If there is some degree of dimensional change in a body upon which stress is applied, this change is called deformation or strain.
Now let's consider that a stress is applied to a body, deformation occurs and (upon removal of the force of stress), the body returns to its original dimensions. In this case, the body would be considered perfectly elastic. In reality, it's safe to say that few if any materials are perfectly elastic, the result of several conditions that can affect the ability of a material to be deformed and then return to its original dimensions. Material type, extent and frequency of repeated loads, operating temperatures, conditions determined by heat treatment or other processes affecting structural properties (where applicable) and related factors can play into the scenario.
In addition, it's possible to exceed the elastic limit of a material; e.g., its ability to resist permanent deformation is removed and a new set of dimensions result after all external stresses are removed. Let's take this notion one step further.
Suppose we are applying an incremental stress to a material in a way that is proportionally close to the increased amount of deformation. These conditions define working within the material's proportional elastic limit. However, if a certain limit to the applied stress is exceeded, the resulting deformation of the material is not proportional to the stress being applied and the proportional elastic limit is exceeded. This notion is important because it can be applied to such engine components as connecting rods and crankshafts; rods in particular. And, as you might expect, temperature can affect certain structural properties of materials, often times having a corresponding impact on how stresses are developed and promoted.
What is important at this point is to understand that there is a vast range of conditions that can affect how certain materials respond to their environments and, consequently, can endure their intended environments. We mentioned some of the basic conditions and considerations purely as an introduction to the field of studies involved not only in the selection of materials for specific applications but to emphasize that there is also a span of processes developed and applied that will extend a given material's use life. Specifically how improvements can be made to increase stress or impact resistance, ways to extend elastic limits and methods by which load cycle degree and frequency can be applied with minimum parts damage or shortening of use life are all parts of making improved products, particularly within the motorsports community.
Now, long story short and based upon the demands often placed on racing products, there are ongoing explorations for material conditioning methods outside those traditionally used in racing. The aerospace industry is a fertile ground for such technologies that also include those associated with the coatings industry. And, in fact, some of these coatings technologies are aimed at being supplemental to techniques applied to the structural integrity of coated products. There are also new and emerging methods that deal with both internal and surface modifications intended to extend product life.
Boiling all this down to a more practical and less theoretical level, for those of us who still enjoy turning wrenches, CT was recently made aware of a new surface finishing process that appears on the verge of having a beneficial effect on the racing community. According to reliable sources, the process is already being successfully applied to extending the longevity of connecting rods and it appears other applications are currently being investigated. It's not often that the readers of this little column are able to derive some insight about new and emerging processes or products that might have a favorable impact on their particular involvement in the circle track racing community. There's a distinct possibility that the technique you'll soon see described on the pages of this magazine could fall into that category. If I have a personal regret at this point, it's only that old Smoke isn't around to register his comments. There is little doubt in my mind that if he were, we'd all get an ear-full about his views on its pros and cons. Watch for an upcoming issue of CT for the full low-down.