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To define the fatigue crack propagation mode for the prediction and classification of the experimental results based on its evolution mechanism, successive mesoscopic observations of a fatigue process under pure cyclic mode II loading are performed. Thus, damage accumulation, which is considered to be a vacancy accumulation, is found to be a mechanism. The phenomena occur not at the crack tip but ahead of it. Thus, “plastic deformation mode” and “damage accumulation mode” are the terms proposed to represent the fatigue crack propagation modes instead of “tensile mode” and “shear mode,” respectively. Moreover, as a method to classify both the fatigue crack propagation modes using the experimental results, it is proposed to identify the plastic strain in the wake of the crack tip.

This paper proposes a method for determining the mechanical properties (Young's modulus, Poisson's ratio, yield strength, and work hardening factor) of a material at a specific point using an indentation technique that utilizes a specially designed indenter in conjunction with an inverse problem and finite element analyses. The specially designed indenter combines the characteristics of spherical and conical indenters and can be used to produce multiple indentations at a single point. The feasibility of the proposed method for determining the local mechanical properties of a material was confirmed by detailed precision verifications in the ideal case and the worst case.

The interaction of hydrogen with the dislocations in the plastic zone of preexisting cracks (pre-cracks) in engineering components generally degrades the ultimate tensile strength (UTS). Hence, the crack effect coupled with hydrogen-embrittlement (HE) is widely believed to be harmful in engineering applications. However, in this study, the UTS of shallow pre-cracked structures made of interstitial-free (IF) steel, which is a hydrogen-embrittlement sensitive material, may not be wakened in hydrogen environment. Results of cylinder specimens with saturated hydrogen were experimentally and microscope-analytically compared with that of specimens without hydrogen. Then, this anti-common-sense influence of hydrogen was attributed as follows: (1) the crack propagation assisted by hydrogen enhanced localized plasticity (HELP) is stable before the onset of plastic instability because of high fracture instability toughness; and (2) the plastic strain localization at tips of the pre-crack and secondary cracks resists the onset of plastic instability. Additionally, the applicability of such a shallow crack effect coupled with HE presented by this study in engineering applications was discussed.

In this study, in order to define a fatigue crack initiation unit, the relationship between the fatigue crack initiation process and the crystal structure in the pearlitic steel used for railroad rails was examined and fatigue tests, focusing on crack initiation, were performed. The fracture surfaces were analyzed using a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The crystal structure of the pearlitic steel is composed of “pearlitic colonies” that have the same lamellar structure direction and “pearlitic blocks” that have the same ferrite crystal direction. The SEM and EBSD results revealed that the crack initiation depends on the pearlitic colonies. Therefore, we defined the characteristic dimension for fatigue crack initiation as the pearlitic colony size. However, for safety purposes, the pearlitic block size should be considered the engineering definition of the fatigue crack initiation unit, since decreasing the pearlitic block size should cause an improvement in the fatigue limit of pearlitic steel.

The purpose of this study was to develop a compact wearable pneumatic drive unit for a ventricular assist device (VAD). This newly developed drive unit, 20 × 8.5 × 20 cm in size and weighing approximately 1.8 kg, consists of a brushless DC motor, noncircular gears, a crankshaft, a cylinder-piston, and air pressure regulation valves. The driving air pressure is generated by the reciprocating motion of the piston and is controlled by the air pressure regulation valves. The systolic ratio is determined by the noncircular gears, and so is fixed for a given configuration. As a result of an overflow-type mock circulation test, a drive unit with a 44% systolic ratio connected to a Toyobo VAD blood pump with a 70-ml stroke volume achieved a pump output of more than 7 l/min at 100 bpm against a 120 mmHg afterload. Long-term animal tests were also performed using drive units with systolic ratios of 45% and 53% in two Holstein calves weighing 62 kg and 74 kg; the tests were terminated on days 30 and 39, respectively, without any malfunction. The mean aortic pressure, bypass flow, and power consumption for the first calf were maintained at 90 × 13 mmHg, 3.9 × 0.9 l/min, and 12 × 1 W, and those for the second calf were maintained at 88 × 13 mmHg, 5.0 × 0.5 l/min, and 16 × 2 W, respectively. These results indicate that the newly developed drive unit may be used as a wearable pneumatic drive unit for the Toyobo VAD blood pump.

The effect of shear-affected zone (SAZ), with a stress-concentration source induced by the punching process, on tensile properties was investigated. Tests using honed specimens (which have the same shapes and stress-concentration without any SAZ) and smooth specimens were conducted to compare the effect with that of the punched specimens. Dual-phase steel, which has a high work-hardening ability and low yield strength, and precipitation-hardened steel, which has a low work-hardening ability and high yield strength, were used in the tests. Materials with two tensile strength grades were prepared from both types of steel. Only the precipitation-hardened steel with higher strength grade punched specimen showed a brittle fracture with extremely short fracture-elongation, whereas the other specimens showed a ductile fracture. The fracture surface analysis revealed that cracks initiated in the maximum shear stress plane of the SAZ under tensile loading at first. We call the crack “shear crack.” The steel which showed brittle fracture used in this study easily exhibited plastic-strain localization compared with the other steels. If the shear crack is sharp, then the transition from ductile to brittle failure tends to occur. Furthermore, the strength characteristics of the punched specimen depend on the crack length dependency of the strength resistance and the failure phenomenon of the original material.

The annual survey of the Japanese Society for Dialysis Therapy Renal Data Registry (JRDR) was sent to 4458 dialysis facilities at the end of 2018; among these facilities, 4402 facilities (98.7%) responded to the facility questionnaire, and 4222 (94.7%) responded to the patient questionnaire. The number of chronic dialysis patients in Japan continues to increase every year; as of the end of 2018, it had reached 339,841 patients, representing 2688 patients per million population. Among the prevalent dialysis patients, the mean age was 68.75 years, and diabetic nephropathy was the most common primary disease among the prevalent dialysis patients (39.0%), followed by chronic glomerulonephritis (26.8%) and nephrosclerosis (10.8%). The number of incident dialysis patients was 40,468, and a reduction by 491 from 2017. The mean age of the incident dialysis patients was 69.99 years old. Diabetic nephropathy was also the most common primary disease (42.3%), representing a 0.2 percent point reduction from 2017. The distribution of diabetic nephropathy appears to have reached a plateau. The number of deceased patients during 2018 was 33,863, and the crude annual death rate was 10.0%. Heart failure was the most common cause of death (23.5%), followed by infection (21.3%) and malignant tumor (8.4%); these causes were similar to those for 2017. The number of patients receiving hemodiafiltration has been increasing since 2012, reaching 125,793 or 37.0% of all dialysis patients at the end of 2018. The number of patients receiving peritoneal dialysis has been gradually increasing since 2017, reaching 9445, and 19.7% of these patients were treated using a combination of peritoneal dialysis and hemodialysis or hemodiafiltration. The proportion of patients receiving combination therapy has remained at around 20% of all peritoneal dialysis patients. The number of patients undergoing home hemodialysis was 720, representing an increase of 36 patients from 2017. The 2018 JRDR survey included several topics such as the present status of the patient kinetics of chronic dialysis patients at the end of 2018, water treatment and hemodiafiltration, peritoneal dialysis, treatments for diabetes, mental and physical conditions, and the present status of viral hepatitis. In this paper, we describe the patient and facility kinetics. Trial registration The JRDR was approved by the ethics committee of the JSDT (approval number 1-3) and was registered in the “University hospital Medical Information Network (UMIN) Clinical Trials Registry” under the clinical trial ID of UMIN000018641 on August 8, 2015: (Accessed June 2, 2020)

We describe a case in which an axillary Impella 5.0, stuck in an area of calcification in the right subclavian artery, could not be retrieved in the usual manner. However, it was successfully removed using a long 22-Fr sheath and snaring catheter by means of the trans-femoral artery. Device retrieval using the trans-femoral artery snare technique is considered a valid option for removing the Impella device in patients who exhibit this complication.