Evaluation of Residual Stresses in PVD Coatings by Means of Strip Substrate Length Variation and Curvature Method of Plate Substrate

The aim of the study was to determine macroscopic residual stresses in Physical Vapor Deposits (PVD) coatings through measurement of the length variation of the strip substrates coated on both sides. The length change of the strip was reduced to the deflection of the middle cross-section of the elastic element and was recorded by four strain gauges. For validating the obtained results, the conventional curvature method was used. As an application, residual stresses in hard AlCrN PVD coatings were investigated. The coatings were nanolayered to achieve better coating toughness for blanking and punching applications. The steel strips and steel plates with two thicknesses were used as the substrate. The values of the compressive residual stresses, determined by both methods for the investigated coatings, were very high (3.3 -3.6 GPa) independent of coating thickness and practically equal within the measurement uncertainty of the method. Good agreement between the experimental results obtained with both methods suggests that the presented method, strip length variation, is applicable for determination of residual stresses in coatings. Compressive stresses in coatings are desirable as they strengthen the coating.

What Walrasian Marxism Can and Cannot Do

In their article “Roemer's ‘General’ Theory of Exploitation is a Special Case: The Limits of Walrasian Marxism,” Devine and Dymski portray me as some sort of Walrasian automaton who believes that phenomena that are not easily modelled using the Walrasian model of perfect competition do not exist. Their criticism of my theory assumes that I was attempting to model capitalism in its entirety, a task that, I agree, I failed to do. I did not propose a theory of accumulation, or of technological change, or of the methods by which capitalists maintain their ideological hegemony over workers, or of the methods by which they extract labor from labor power at the point of production. I was not, in short, trying to write an alternative to Das Kapital. My General Theory of Exploitation and Class (GTEC), as its Introduction explained, was an attempt at understanding the root causes of exploitation and class, so as to better understand how class formation and exploitation might occur in postcapitalist societies. To this end, I adopted a well-known scientific method: strip away many real aspects of the thing under study down to a minimal skeleton and see how many phenomena descriptive of the real thing one can generate. Then add more real aspects of the thing to the model, and see how much more one can generate.