Wyniki wyszukiwania - BazTech

1

Mechanical behaviour and phase transition mechanisms of a shape memory alloy by means of a novel analytical model

Carpinteri A., Di Cocco V., Fortese G., Ronchei C., Scorza D., Vantadori S., Zanichelli A., Iacoviello F., Natali S.

Acta Mechanica et Automatica

|

2018

|

Vol. 12, no. 2

105--108

EN

The aim of the present paper is to examine both the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy through cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine and the contents of both austenite and martensite phase are experimentally measured by means of X-Ray diffraction (XRD) analyses. On the basis of such experimental results in terms of martensite content, an analytical model is here formulated to correlate the stress-strain relationship to the phase transition mechanisms. Finally, a validation of the present model by means of experimental data pertaining the stress-strain relationship is performed.

2

Fatigue Crack Propagation in Notched and Unnotched Round Bars

Carpinteri A., Vantadori S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2005

|

z. 79

53-64

3

Theoretical interpretation of size effect in fatigue

Carpinteri A., Landini A., Spagnoli A.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2001

|

Vol. 269, z. 67

67-83

EN

As is well-known, the fatigue strength of materials decreases by increasing the specimen size. Such a decrease can be remarkable when very large structures are considered. An overview of experimental findings and theoretical studies on this phenomenon is presented. Then size effect in fatigue is explained by considering the fractal nature of the reacting cross sections of t structures, that is, the renormalized fatigue strength is represented by a force amplitude acting on I a surface with a fractal dimension lower than 2. This dimensional decrement, which depends on a self-similar weakening of the material ligament, owing to the presence of cracks, defects, voids, etc. (microscopic level), tends to progressively disappear by increasing the structure size (macroscopic level), i.e. the effect of the material microstructure on the fatigue behaviour gradually finishes for relatively large structures (multifractality). Accordingly, two scaling laws for fatigue limit are herein proposed, and some experimental results are examined in order to show how to apply the theoretical approach presented.

4

Critical plane approach for multiaxial fatigue of metals

Carpinteri A., Spagnoli A., Vantadori S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2001

|

Vol. 269, z. 67

47-66

EN

Some common fatigue criteria applicable to generic plane stress states under sinusoidal loading are reviewed with emphasis to those based on the so-called critical plane approach. Then a multiaxial high-cycle fatigue criterion recently proposed by the authors and based on the critical plane approach is discussed. Such a criterion can be applied to the case of sinusoidal plane stress states, and an extension to random loading is presented. According to this criterion, the critical plane orientation is correlated with the averaged principal stress directions deduced through the weight function method. Then the fatigue failure assessment is performed by considering a nonlinear combination of the maximum normal stress and the shear stress amplitude acting on the critical plane. Finally, relevant experimental tests on brittle (hard) metals, related to sinusoidal as well as random plane stress states, are analysed by applying the proposed criterion, together with other common critical plane criteria.