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Tool Life

As suggested by our opening paragraph, there are three possible modes by which a cutting tool can fail in machining:

1.Fracture Failure: This mode of failure occurs when the cutting force at the tool point becomes excessive, causing it to fail suddenly by brittle fracture.

2.Temperature Fracture: This failure occurs when the cutting temperature is too high for the tool material, causing the material at the tool point to soften, which leads to plastic deformation and loss of the sharp edge.

3.Gradual Wear: Gradual wearing of the cutting edge causes loss of tool shape, reduction in cutting efficiency, an acceleration of wearing as the tool becomes heavily worn, and finally tool failure in a manner similar to a temperature failure.

Fracture and temperature failures result in premature loss of cutting tool. These two modes of failure are therefore undesirable. Of the three possible tool failures, gradual wear is preferred because it leads to the longest possible use of the tool, with the associated economic advantage of that longer use.

(Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, Mikell P. Groover, p.552-553)

Stress Intensity Factor

For surface cracked plate under unaxial load, the stress intesity factor correlations for semi-eliptical surface cracks were obtained using finite element methods. For the current analysis, the stress intensity factors were were taken from, which presents the stress intensity factors along the crack front for semi-elirtical surface cracks within the range of 0<=a/c<=1 and for a plate geometry within 0<=a/t<=0.8 under general linear and nonlinear loads. Where a/c is crack aspect ratio and a/t is plate ratio.

(Fatigue and fracture mechanics: 34th volume , Steven R. Daniewicz,J. C. Newman,Karl-Heinz Schwalbe,ASTM Committee E-8 on Fatigue and Fracture,European Structural Integrity Society, p.249)

Hierarchical Production Planning

Hierarchical production planning (HPP) represents an approach and a philosophy towards the organization, planning and scheduling of production activities which has existed both in theory and practice fr several decades. Originally developed as a planning and scheduling approach primarily for production activities, the philosophy of hierarchical production planning has evolved to encompass a broad range of supply chain management activities. Today, one can observe what can broadly be viewed as extensions of the HPP philosophy across activities ranging from production planning and integrated distribution and production planning to supply chain wide inventory management, transportation and warehouse planning and scheduling,sales and marketing planning and so on. In many of these activity areas, understandably no mention or acknowledgement of the hierarchical production planning approach exists. Nevertheless, upon closer inspection, clear similarities in techniques and philosophy exist among the myriad decision-making approaches used today to manage the diverse aspects of the supply chain and those techniques and approaches which embody hierarchical production planning. The common theme of a hierarchical approach towards the management of decision-making activities across the supply chain suggests that there exist benefits and broad learnings to be gained from exploring the hierarchical approaches and techniques utilized today in managing different components of the supply chain.

(Hierarchical Operations and Supply Chain Planning, Tan C. Miller,p.1)

Hardcoating

Hardcoating gives an aluminum surface the hardness of case-hardened steel(Rc 50-60) while maintaining the light weight of aluminum. Hardcoated surfaces may be found in hospitals, schools,factories, in the home, under the sea, and on the moon.

When a permanent dry lubrication is added to the hardcoted surface we find many more uses for it. A hardcoated aluminum prosthetic arm can have its joints permanently lubricated by this process.

Two types of hardcoats are currently available: the older type is formed at low temperature in sulphuric acid; the newer type is formed at room temperature, also in sulphiric acid.

(Modern manufacturing processes , James A. Brown,p.34)