0


EDITOR'S NOTE

J. Eng. Mater. Technol. 2002;124(4):389. doi:10.1115/1.1499725.
FREE TO VIEW
Commentary by Dr. Valentin Fuster

TECHNICAL PAPERS

J. Eng. Mater. Technol. 2002;124(4):390-396. doi:10.1115/1.1494449.

Shape memory alloy TiNi fiber epoxy resin composite (SMA-FEC) was developed and the active reinforcement effect of the material was investigated by strain gauge measurement and photoelastic method. In this paper material processing of the SMA-FEC and mechanical testing results are described. The recovery stress-strain at various ambient temperatures by means of strain gauges are reported. A typical shrinkage of the SMA-FEC was recognized with increasing temperature above the inverse transformation temperature Af of embedded SMA TiNi fiber, and it depended on the fiber volume fraction (Vf) as well as prestrain value. The validity of the composite using the photoelastic model was discussed in detail. By adjusting the fiber volume fraction and prestrain, one can obtain expected elastic modulus and stress fringes value to conduct photoelastic experiment with SMA-FEC as model material. The active reinforcement of the SMA-FEC smart composite was reconfirmed visually from the change of the photoelastic fringe patterns of the specimen by heating at various temperatures.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):397-401. doi:10.1115/1.1495001.

The two-way shape memory effect (TWSME), has been studied in a near-equiatomic NiTi commercial alloy. Two bending training methods have been applied on NiTi wires. One is based on the martensite deformation and the other on thermal cycling under constant bending curvature. The efficiency of each method has been evaluated with better results of TWSME in the martensite deformation method. Finite element simulation has been performed on wires, in the pure bending mode, in order to calculate the maximum tensile strain in the transversal section of the wire. These simulations have allowed us to compare our results with the TWSME data obtained in prior studies under the tensile mode.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):402-411. doi:10.1115/1.1494450.

Many theoretical studies have been made to describe multiaxial ratchetting and most of them have been concentrated on the location of the yield domain, not on its shape. In this paper, we introduce nonlinear kinematic constitutive equations consistent with ratchetting modeling into the distortional model of subsequent yield surfaces proposed by Kurtyka, T., and Zyczkowski, M. We use an efficient polycrystalline model to simulate complex tests including yield surface detections in order to get some reference predictions to use in the development of the constitutive laws introduced into the distortional model. The distortional model is thus qualitatively identified with the polycrystalline model and then quantitatively identified with the experimental results on a type 316L stainless steel. It gives promising results.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):412-420. doi:10.1115/1.1491575.

Large deformation failures of aluminum honeycomb materials in dynamic compression, static shear and static tearing are characterized in this comprehensive experimental study. Two low density honeycomb materials that make up the Offset Deformable Barrier (ODB) used in vehicle crash test were tested. Material characterization methods, including one for studying material tearing, have been developed. The honeycomb material data under large deformation, including complete curves of compression and shear stress-strain relations in the three principal directions, are presented and analyzed. Honeycomb material tearing strength, defined as tearing force per unit tearing length, is introduced. Strain-rate dependence of honeycomb materials under dynamic loading is investigated. Local failure mechanisms of honeycombs in compression, shear, and indentation punch tests and their relations with the bulk properties of the materials are studied in detail. The results of this research may be used to improve the material fidelity of finite element simulations of the ODB.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):421-427. doi:10.1115/1.1417486.

A method for determination of minimum sample size required to estimate the fatigue life has been presented. No functional relationship between stress and fatigue life other than log normal and Weibull distribution function of fatigue life has been assumed. The method is based on the analysis of the variance of error which arises due to scattered nature of the fatigue life data. An example of the application of the presented method is also given.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):428-433. doi:10.1115/1.1417981.

In the present work an experimental method is developed for residual stress evaluation in medium thick plates. On the basis of the incremental hole-drilling technique, a method to resolve the in-plane residual stresses through the plate thickness is given. An analysis of the hole-drilling configuration is carried out, resulting in a configuration which optimizes the stress calculation accuracy. Moreover, it is estimated that conventional milling can be applied without affecting the accuracy of the method. Finally, the results of a comprehensive stress calculation error analysis are presented.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):434-439. doi:10.1115/1.1493805.

For a perforated sheet with circular holes, used in shadow masks, the diameter of the circular hole varies through the thickness, and the nonuniform circular holes are arranged in a triangular pattern. In order to simplify the analysis, a perforated sheet with equivalent circular holes of uniform diameter is proposed such that its plastic behavior is similar to that with the given nonuniform circular holes. In this study, a yield criterion is discussed for the perforated sheet with uniform circular holes by employing an equivalent continuum approach, which is then applied to examine the plastic deformation of the perforated sheet with nonuniform circular holes. The analytical results predicted by the theory, including those for the apparent yield stresses and strain ratios, are verified by the results obtained from the finite element analysis and also from experiments.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 2002;124(4):440-450. doi:10.1115/1.1494093.

Cohesive Zone Models (CZMs) are being increasingly used to simulate fracture and fragmentation processes in metallic, polymeric, and ceramic materials and their composites. Instead of an infinitely sharp crack envisaged in fracture mechanics, CZM presupposes the presence of a fracture process zone where the energy is transferred from external work both in the forward and the wake regions of the propagating crack. In this paper, we examine how the external work flows as recoverable elastic strain energy, inelastic strain energy, and cohesive energy, the latter encompassing the work of fracture and other energy consuming mechanisms within the fracture process zone. It is clearly shown that the plastic energy in the material surrounding the crack is not accounted in the cohesive energy. Thus cohesive zone energy encompasses all the inelastic energy e.g., energy required for grainbridging, cavitation, internal sliding, surface energy but excludes any form of inelastic strain energy in the bounding material.

Commentary by Dr. Valentin Fuster

ERRATUM

J. Eng. Mater. Technol. 2002;124(4):451. doi:10.1115/1.1511521.
FREE TO VIEW

 Arcan specimen with location of friction stir weld. Thickness≈6.3 mm after light machining of surfaces.

Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In