Results of an experimental investigation of damage due to prior fatigue of metallic materials through static and cyclic Small Punch Test (SPT) is presented in this paper. Monotonic small punch tests were performed on virgin specimens of copper, brass, and stainless steel (SS-304) as well as on fatigue damaged copper samples to understand the effect of prior damage on tensile properties. It is observed that, the slope of initial linear portion of load-displacement response when normalized by initial thickness of the SPT specimen is proportional to the elastic modulus. Damage fraction estimated based on conventional damage theories was found to correlate reasonably with the data derived from static small punch testing. Fatigue response of materials was evaluated through a novel cyclic small punch testing under global compression-compression loading. Variation of punch displacement and hysteresis energy was monitored as a function of the number of cycles. Distinct change in punch displacement, cumulative hysteresis energy, was observed prior to complete failure of specimen. An empirical equation relating to the level of damage and hysteresis energy during cyclic SPT is proposed. Copyright © 2014 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

Raghu V. Prakash

Department of Mechanical Engineering

Bone cement

Copper

Fracture

hysteresis

materials testing

Metallic glass

Stainless steel

COMPRESSION LOADING

Empirical equations

Experimental investigations

HYSTERESIS ENERGIES

LOAD-DISPLACEMENT RESPONSE

PUNCH DISPLACEMENT

SMALL PUNCH TEST

Small punch testing

Fatigue damage

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

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IIT Madras

Evaluation of Damage in Materials Due to Fatigue Cycling Through Static and Cyclic Small Punch Testing

ASTM Special Technical Publication

Small specimen test techniques are suitable for assessing the current mechanical properties of in-service components using small volume samples compared to conventional tests. Small punch test is a reliable test method for predicting the post-yield response. The effect of lubrication of the punch-specimen interface on the load–displacement response and strain distribution in the specimen is presented here. Lubricating the punch-specimen interface reduces the ultimate load and also moves the failure site closer to the pole of the punch. It is found that the loading slope changes as a function of displacement. However, its effect on the plastic properties like strength coefficient and strain hardening exponent was considerably less (~6 % with respect to dry condition). Interrupted tests were conducted at different fractions of ultimate load which revealed that the peak strain was greater in dry condition than the lubricated case. © 2015, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

Influence of Friction on the Response of Small Punch Test

Fatigue properties of materials is an important input while estimating the residual life of critical components. Fatigue data (stress vs. cycles or strain vs. cycles or fatigue crack growth rate data) are used to predict the residual life. One of the shortcomings of this method is that it relies on data generated from virgin material or surveilance coupons which have been exposed to the harsh environment over a period of time. Often the quantity of material available for fatigue data is small and being probabilistic in nature, fatigue data requires multiple specimens to be tested at any given stress/strain levels. This has prompted us to develop test procedures to determine the fatigue data of materials from small volume of material. In this paper, we present the results of cyclic ball indentation test method as well as cyclic small punch test method that is used to generate the fatigue data at different stress levels. There are several fine details relating to these test technique - viz., establishing a equivalent damage criteria for failure life with standard LCF/HCF test specimens. Apart from this, several variables that influence the testing process needs to be considered. This paper briefly reviews the viability of using miniature specimen test techniques, particularly cyclic ball indentation and cyclic small punch testing for extracting the fatigue data, based on the author's previous work. It is shown that, both the test techniques are capable of detecting and quantifying the prior fatigue damage in the materials. Copyright © 2015 by ASME.

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

Evaluation of fatigue data through miniature specimen test techniques

Small specimen testing has become popular in the recent times, due to the need for material property evaluation using limited volume samples available from processing techniques, scoop extraction of materials. There are several methods of direct and in-direct mechanical property evaluation such as: automated ball indentation, miniature tensile testing, small punch testing, shear punch testing and miniature specimen impact testing. Most of these techniques provide a correlation with standard specimen test data through empirical relationships. This paper summarizes work done at the author's Institution during the last decade on small specimen testing, with specific reference to spherical ball indentation (both static as well as cyclic indentation), shear punch and small punch testing on a number of metallic materials. Specific examples of how the material degradation due to prior damage (plastic deformation, fatigue, creep) are discussed. Copyright © 2014 by ASME.

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

A decade of experience with small specimen testing to evaluate mechanical properties of materials

Evaluation of damage in materials due to fatigue cycling through static and cyclic small punch testing

Journal	Data powered by TypesetASTM Special Technical Publication
Publisher	Data powered by TypesetASTM International
ISSN	00660558
Impact Factor	No
Open Access	No
Citation Style	unsrt