Effect of Plastic Deformation on Compliance Curve Based Crack Closure Measurement

Fatigue crack growth depends heavily on near tip stress-strain behavior controlled by many micromechanical and microstructural factors. Crack closure is widely used to rationalize crack growth behaviour under complex loading conditions. Reliable crack closure measurement is essential for enhanced damage tolerance design and remains a challenge to the industry. This paper focuses on the effect of plastic deformation ahead of a notch/crack on the non-linearity of compliance curves of 6082-T651 aluminium alloy specimens to highlight a potential issue in the conventional compliance curve based crack closure measurement technique. Experimental and numerical simulation results demonstrate that plastic deformation ahead of the notch will introduce non-linear stress-strain behavior in the absence of crack closure. It is proposed that the effect of crack tip plasticity on the non-linearity of the compliance curve be separated to obtain reliable crack closure measurement.

An Investigation of the Vibration Testing Method for Small Diameter Endmills

This paper introduced about the in-process vibration testing method for small diameter endmill. By this method, the natural frequency and modal parameters such as mass, damping, and stiffness of the milling tool can be determined in the milling process. An oscillation of the vibrator is controlled by the function generator to apply the impact force at the appropriate cutting period. The measurement setup can determine the compliance curve by the measurement signals of the exiting force and tool deformation. To evaluate the feasibility of the new method, vibration tests were performed on a square endmill which has the diameter of 4 mm in the milling on brass material. Results of vibration tests show that modal parameters of the specific vibration mode can be determined by the new developed method.

Daily Collection of Self-Reporting Sleep Disturbance Data via a Smartphone App in Breast Cancer Patients Receiving Chemotherapy: A Feasibility Study (Preprint)

BACKGROUND Improvements in mobile telecommunication technologies have enabled clinicians to collect patient-reported outcome (PRO) data more frequently, but there is as yet limited evidence regarding the frequency with which PRO data can be collected via smartphone applications (apps) in breast cancer patients receiving chemotherapy. OBJECTIVE The primary objective of this study was to determine the feasibility of an app for sleep disturbance-related data collection from breast cancer patients receiving chemotherapy. A secondary objective was to identify the variables associated with better compliance in order to identify the optimal subgroups to include in future studies of smartphone-based interventions. METHODS Between March 2013 and July 2013, patients who planned to receive neoadjuvant chemotherapy for breast cancer at Asan Medical Center who had access to a smartphone app were enrolled just before the start of their chemotherapy and asked to self-report their sleep patterns, anxiety severity, and mood status via a smartphone app on a daily basis during the 90-day study period. Push notifications were sent to participants daily at 9 am and 7 pm. Data regarding the patients&#8217; demographics, interval from enrollment to first self-report, baseline Beck&#8217;s Depression Inventory (BDI) score, and health-related quality of life score (as assessed using the EuroQol Five Dimensional [EQ5D-3L] questionnaire) were collected to ascertain the factors associated with compliance with the self-reporting process. RESULTS A total of 30 participants (mean age 45 years, SD 6; range 35-65 years) were analyzed in this study. In total, 2700 daily push notifications were sent to these 30 participants over the 90-day study period via their smartphones, resulting in the collection of 1215 self-reporting sleep-disturbance data items (overall compliance rate=45.0%, 1215/2700). The median value of individual patient-level reporting rates was 41.1% (range 6.7-95.6%). The longitudinal day-level compliance curve fell to 50.0% at day 34 and reached a nadir of 13.3% at day 90. The cumulative longitudinal compliance curve exhibited a steady decrease by about 50% at day 70 and continued to fall to 45% on day 90. Women without any form of employment exhibited the higher compliance rate. There was no association between any of the other patient characteristics (ie, demographics, and BDI and EQ5D-3L scores) and compliance. The mean individual patient-level reporting rate was higher for the subgroup with a 1-day lag time, defined as starting to self-report on the day immediately after enrollment, than for those with a lag of 2 or more days (51.6%, SD 24.0 and 29.6%, SD 25.3, respectively; <i>P</i>=.03). CONCLUSIONS The 90-day longitudinal collection of daily self-reporting sleep-disturbance data via a smartphone app was found to be feasible. Further research should focus on how to sustain compliance with this self-reporting for a longer time and select subpopulations with higher rates of compliance for mobile health care.

Prediction of Bending Creep Behavior of Rice Hull Flour/Polypropylene Composite

The creep behaviors of rice hull flour/PP composite under different stress levels were studied through bending test. The results show that the bending creep behaviors of rice hull flour/PP composite have obviously correlation to the stress levels. Based on the time-temperature-stress equivalence principle and 15% stress level as a reference, the creep compliance master curve of 15% stress level was constructed by horizontally shift the creep compliance curve of other stress levels, which can predict the creep behavior of rice hull flour/PP composite at the 15% stress level.

Modeling and Prediction of Creep Behavior of Polypropylene Packaging Belt

The short term tensile creep behaviors of polypropylene (PP) packaging belt under different stresses levels were studied through tensile creep test. The four-element model was applied to simulate the creep behaviors of the PP packaging belt. The results show that four-element model can be used to simulate the short time creep of PP packaging belt. The tensile creep behaviors of PP packaging belt have obviously correlation to the stress levels. The instantaneous elastic coefficient, delayed elastic coefficient and glutinous coefficient in Maxell model show a decreasing tendency with the increase of stress level. Based on the time-temperature-stress equivalence principle and take 15% stress level as a reference, the creep compliance master curve of 15% stress level was constructed by horizontal shift of the creep compliance curve of other stress levels, which can predict the creep behavior of PP packaging belt at the 15% stress level.

A dynamic nonlinear relationship between the static and pulsatile components of intracranial pressure in patients with subarachnoid hemorrhage

Object In the search for optimal monitoring and predictive tools in neurocritical care, the relationship of the pulsatile component of intracranial pressure (ICP) and the pressure itself has long been of great interest. Higher pressure often correlates with a higher pulsatile response to the heartbeat, interpreted as a type of compliance curve. Various mathematical approaches have been used, but regardless of the formula used, it is implicitly assumed that a reproducible curve exists. The authors investigated the stability of the correlation between static and pulsatile ICPs in patients with subarachnoid hemorrhage (SAH) who were observed for several hours by using data sets large enough to allow such calculations to be made. Methods The ICP recordings were obtained in 39 patients with SAH and were parsed into 6-second time windows (1,998,944 windows in 197 recordings). The ICP parameters were computed for each window as follows: static ICP was defined as the mean ICP, and pulsatile ICP was characterized by mean ICP wave amplitude, rise time, and rise time coefficient. Results The mean ICP and ICP wave amplitudes were simultaneously high or low (the expected correlation) in only ~ 60% of observations. Furthermore, static and pulsatile ICP correlated well only over short intervals; the degree of correlation weakened over periods of hours and was inconsistent across patients and within individual patients over time. Decorrelation originated with abrupt shifting and gradual drifting of mean ICP and ICP wave amplitude over several hours. Conclusions The relationship between the static and pulsatile components of ICPs changes over time. It evolves, even in individual patients, over a number of hours. This can be one reason the observation of high pulsatile ICP (indicative of reduced intracranial compliance) despite normal mean ICP that is seen in some patients with SAH. The meaning and potential clinical usefulness of such changes in the curves is uncertain, but it implies that clinical events result not only from moving further out on a compliance curve; in practice, the curve, and the biological system that underlies the curve, may itself change.

Physical Aging and Creep Behavior of Poly(Methyl Methacrylate)

In this work, the physical aging and its effect on nonlinear creep behavior of poly(methyl methacrylate) are presented. After annealing above Tg to release the previous thermal and stress history, the samples were quenched to 60oC, aged for various times, and were then tested at three different stress levels (22MPa, 26MPa and 30MPa) at room temperature of 27oC. At each stress level, the creep strain was converted to compliance and measured as a function of test time and aging time. The test results show that higher stress accelerates creep rate of the material while physical aging plays a reverse role. The time-aging time superposition is applicable to build a master creep compliance curve at each stress level, and it is demonstrated that the shift rate deceases with increasing stress. Moreover, based on the time-stress superposition principle, a unified master curve was constructed by further shifting the sub-master curves at 30MPa and 26 MPa to a reference stress level of 22MPa.