The development and preliminary testing of an instrument for assessing fatigue self-management outcomes in patients with advanced cancer

Background: Fatigue is one of the most distressing and commonly experienced symptoms in patients with advanced cancer. Although the self-management (SM) of cancer-related symptoms has received increasing attention, no research instrument assessing fatigue SM outcomes for patients with advanced cancer is available. Objectives: to describe the development and preliminary testing of an interviewer administered instrument for assessing the frequency, and perceived levels of effectiveness and self-efficacy associated with fatigue SM behaviors in patients with advanced cancer. Methods: The development and testing of the Self-efficacy in Managing Symptoms Scale- Fatigue Subscale for Patients with Advanced Cancer (SMSFS-A) involved a number of procedures: item-generation using a comprehensive literature review and semi-structured interviews, content validity evaluation using expert panel reviews, and face validity and test-retest reliability evaluation using pilot testing. Results: Initially, 23 items (22 specific behaviors with one global item) were generated from the literature review and semi-structured interviews. After two rounds of expert panel review, the final scale was reduced to 17 items (16 behaviors with one global item). Participants in the pilot test (n=10) confirmed that the questions in this scale were clear and easy to understand. Bland-Altman analysis showed agreement of results over a one-week interval. Conclusions: The SMSFS-A items were generated using multiple sources. This tool demonstrated preliminary validity and reliability. Implications for practice: The SMSFS-A has the potential to be used for clinical and research purposes. Nurses can use this instrument for collecting data to inform the initiation of appropriate fatigue SM support for this population.

Ultrasonic performance of the PVDF thin film sensors under thermal fatigue

In the present work, the ultrasonic strain sensing performance of the large area PVDF thin film subjected to the thermal fatigue is studied. The PVDF thin film is prepared using hot press and the piezoelectric phase (beta-phase) has been achieved by thermo-mechanical treatment and poling under DC field. The sensors used in aircrafts for structural health monitoring applications are likely to be subjected to a wide range of temperature fluctuations which may create thermal fatigue in both aircraft structures and in the sensors. Thus, the sensitivity of the PVDF sensors for thermal fatigue needs to be studied for its effective implementation in the structural health monitoring applications. In present work, the fabricated films have been subjected to certain number of thermal cycles which serve as thermal fatigue and are further tested for ultrasonic strain sensitivity at various different frequencies. The PVDF sensor is bonded on the beam specimen at one end and the ultrasonic guided waves are launched with a piezoelectric wafer bonded on another end of the beam. Sensitivity of PVDF sensor in terms of voltage is obtained for increasing number of thermal cycles. Sensitivity variation is studied at various different extent of thermal fatigue. The variation of the sensor sensitivity with frequency due to thermal fatigue at different temperatures is also investigated. The present investigation shows an appropriate temperature range for the application of the PVDF sensors in structural health monitoring.

Strength and fatigue life evaluation of composite laminate with embedded sensors

Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and non-invasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

Cement mantle fatigue failure in total hip replacement: Experimental and computational testing

One possible loosening mechanism of the femoral component in total hip replacement is fatigue cracking of the cement mantle. A computational method capable of simulating this process may therefore be a useful tool in the preclinical evaluation of prospective implants. In this study, we investigated the ability of a computational method to predict fatigue cracking in experimental models of the implanted femur construct. Experimental specimens were fabricated such that cement mantle visualisation was possible throughout the test. Two different implant surface finishes were considered: grit blasted and polished. Loading was applied to represent level gait for two million cycles. Computational (finite element) models were generated to the same geometry as the experimental specimens, with residual stress and porosity simulated in the cement mantle. Cement fatigue and creep were modelled over a simulated two million cycles. For the polished stem surface finish, the predicted fracture locations in the finite element models closely matched those on the experimental specimens, and the recorded stem displacements were also comparable. For the grit blasted stem surface finish, no cement mantle fractures were predicted by the computational method, which was again in agreement with the experimental results. It was concluded that the computational method was capable of predicting cement mantle fracture and subsequent stem displacement for the structure considered. (C) 2006 Elsevier Ltd. All rights reserved.

Fatigue Life Assessment and Static Testing of Structural GFRP Tubes Based on Coupon Tests

Fiber-reinforced polymer (FRP) hollow tubes are used in structural applications, such as utility poles and pipelines. Concrete-filled FRP tubes (CFFTs) are also used as piles and bridge piers. Applications such as poles and marine piles are typically governed by cyclic bending. In this paper, the fatigue behavior of glass-FRP filament-wound tubes is studied using coupons cut from the tubes. Several coupon configurations were first examined in 24 tension and five compression monotonic loading tests. Fatigue tests were then conducted on 81 coupons to examine several parameters; namely, loading frequency as well as maximum-to-ultimate (max ult) and minimum-to-maximum (min max) stress ratios, including tension tension and tension compression, to simulate reversed bending. The study demonstrated the sensitivity of test results and failure mode to coupon configuration. The presence of compression loads reduced fatigue life, while increasing load frequency increased fatigue life. Stiffness degradation behavior was also established. To achieve at least one million cycles, it is recommended to limit (max ult) to 0.25. Models were used to simulate stiffness degradation and fatigue life curve of the tube. Fatigue life predictions of large CFFT beams showed good correlation with experimental results. © 2008 ASCE.

Variable mixed-mode delamination in composite laminates under fatigue conditions: testing & analysis

La majoria de les fallades en elements estructurals són degudes a càrrega per fatiga. En conseqüència, la fatiga mecànica és un factor clau per al disseny d'elements mecànics. En el cas de materials compòsits laminats, el procés de fallada per fatiga inclou diferents mecanismes de dany que resulten en la degradació del material. Un dels mecanismes de dany més importants és la delaminació entre capes del laminat. En el cas de components aeronàutics, les plaques de composit estan exposades a impactes i les delaminacions apareixen facilment en un laminat després d'un impacte. Molts components fets de compòsit tenen formes corbes, superposició de capes i capes amb diferents orientacions que fan que la delaminació es propagui en un mode mixt que depen de la grandària de la delaminació. És a dir, les delaminacions generalment es propaguen en mode mixt variable. És per això que és important desenvolupar nous mètodes per caracteritzar el creixement subcrític en mode mixt per fatiga de les delaminacions. El principal objectiu d'aquest treball és la caracterització del creixement en mode mixt variable de les delaminacions en compòsits laminats per efecte de càrregues a fatiga. Amb aquest fi, es proposa un nou model per al creixement per fatiga de la delaminació en mode mixt. Contràriament als models ja existents, el model que es proposa es formula d'acord a la variació no-monotònica dels paràmetres de propagació amb el mode mixt observada en diferents resultats experimentals. A més, es du a terme un anàlisi de l'assaig mixed-mode end load split (MMELS), la característica més important del qual és la variació del mode mixt a mesura que la delaminació creix. Per a aquest anàlisi, es tenen em compte dos mètodes teòrics presents en la literatura. No obstant, les expressions resultants per l'assaig MMELS no són equivalents i les diferències entre els dos mètodes poden ser importants, fins a 50 vegades. Per aquest motiu, en aquest treball es porta a terme un anàlisi alternatiu més acurat del MMELS per tal d'establir una comparació. Aquest anàlisi alternatiu es basa en el mètode dels elements finits i virtual crack closure technique (VCCT). D'aquest anàlisi en resulten importants aspectes a considerar per a la bona caracterització de materials utilitzant l'assaig MMELS. Durant l'estudi s'ha dissenyat i construït un utillatge per l'assaig MMELS. Per a la caracterització experimental de la propagació per fatiga de delaminacions en mode mixt variable s'utilitzen diferents provetes de laminats carboni/epoxy essencialment unidireccionals. També es du a terme un anàlisi fractogràfic d'algunes de les superfícies de fractura per delaminació. Els resultats experimentals són comparats amb les prediccions del model proposat per la propagació per fatiga d'esquerdes interlaminars.

Ultrasonic non-destructive testing of plate-like structures using piezoelectric array transducers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Application study of ultrasonic nondestructive inspection for tire compliance testing. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Modern installation for testing of large assemblies under static and fatigue loading. Description of installation at Fritz Engineering laboratory, Lehigh University, Bethlehem, Pennsylvania,

"Not for publication."

Testing the reliability of a new ultrasonic cardiac output monitor, the USCOM, by using aortic flowprobes in anesthetized dogs

We have used an animal model to test the reliability of a new portable continuous-wave Doppler ultrasonic cardiac output monitor, the USCOM. In six anesthetized dogs, cardiac output was measured with a high-precision transit time ultrasonic flowprobe placed on the ascending aorta. The dogs' cardiac output was increased with a dopamine infusion (0-15 mug (.) kg(-1) (.) min(-1)). Simultaneous flowprobe and USCOM cardiac output measurements were made. Up to 64 pairs of readings were collected from each dog. Data were compared by using the Bland and Altman plot method and Lin's concordance correlation coefficient. A total of 319 sets of paired readings were collected. The mean (+/-SD) cardiac output was 2.62 +/- 1.04 L/min, and readings ranged from 0.79 to 5.73 L/min. The mean bias between the 2 sets of readings was -0.01 L/min, with limits of agreement (95% confidence intervals) of -0.34 to 0.31 L/min. This represents a 13% error. In five of six dogs, there was a high degree of concordance, or agreement, between the 2 methods, with coefficients >0.9. The USCOM provided reliable measurements of cardiac output over a wide range of values. Clinical trials are needed to validate the device in humans.

Size effects on tensile and fatigue behaviour of polycrystalline metal foils at the micrometer scale

Tensile and fatigue properties of as-rolled and annealed polycrystalline Cu foils with different thicknesses at the micrometer scale were investigated. Uniaxial tensile testing results showed that with decreasing foil thickness the uniform elongation decreases for both as-rolled and annealed foils, whereas the yield strength and ultimate tensile strength increase for as-rolled foils, but decrease for the annealed foils. For both the as-rolled or annealed foils, bending fatigue resistance decreases with decreasing the foil thickness. Deformation and fatigue damage behaviour of the free-standing foils were characterised as a function of foil thickness. In addition, the fatigue strength of various small-scale Cu foils was compared to understand they physical mechanisms of size effects on mechanical properties of the metallic material at micrometer scales.