The Effect of Stress Correction on Fracture Point Coordinates in Uniaxial Compression Tests of Cheese

• Published in: Food science & technology Vol. 29; no. 5; pp. 433 - 437
• Main Author: Luginbuhl, W
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1996; Elsevier
• Subjects: Biological and medical sciences; characterization; cheeses; compression; correction factors; Food industries; fracture; Fundamental and applied biological sciences. Psychology; mechanical properties; Milk and cheese industries. Ice creams; strain; stresses; testing; Uniaxial compression; Hard cheese; Semi-hard cheese; Compression test; Quality control; Analytical method
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1006/fstl.1996.0066

The characterization of mechanical properties of hard and semi-hard cheeses by means of uniaxial compression of cylindrical samples is experimentally a simple procedure. However, the evaluation of the compression curves in terms of stress and strain, particularly the determination of the apparent fracture point, is controversial with respect to selection of the appropriate stress representation. Referring to force and displacement as the measurable quantities, it is shown that the application of stress correction induces a shift of the local maximum of the curve. It is derived that this shift is due only to the transformation properties of the correction function with respect to local extrema of the transformed values. Furthermore, the basic assumptions concerning the behaviour of the samples during the test and the validity regime of stress concepts are discussed. It is concluded that both of these aspects do not justify the application of stress correction at large deformations. An operational definition of the apparent fracture point in terms of the unambiguously definable engineering stress avoids the conceptual difficulties of the correction and is therefore advocated.