Half Immersion Research Articles

Effects of cooling thermal shock on the P-wave velocity of granite and its microstructure analysis under immersion in water, half immersion in water, and near-water cooling conditions

Effects of cooling thermal shock on the P-wave velocity of granite and its microstructure analysis under immersion in water, half immersion in water, and near-water cooling conditions

Influence mechanisms under different immersion methods and different strengths of concrete in corrosive environments, and verification via long‐term field test

AbstractThis paper is to study the influence of sulphate corrosion on the mechanical behaviors of concrete, especially concrete corrosion under actual corrosion environment. This study investigated different immersion methods for concrete in a corrosion environment, and different strengths of concrete specimens with contents of sodium sulphate and magnesium chloride of 10.36% and 12.00%, respectively. Strength tests were performed on the specimens for the different immersion methods of full immersion, half‐immersion, and dry‐wet cycles, and with different strengths for the concrete of C20, C35, and C50. To study the internal mechanisms of the corrosion of concrete with different immersion methods and different strengths, a microscopic pore structure test was conducted. The field tests were performed after 12 years to evaluate the long term performance of the concrete under the actual environmental conditions. The test results show that full immersion mainly led to chemical corrosion, half immersion led to double damage from salt crystallization and chemical corrosion, and dry‐wet cycles accelerated the corrosions of the salt crystallization and chemical corrosion. The higher the strength of concrete, the better its resistance to the sulphate corrosion. In comparison with the strength of the concrete before corrosion, field test results show that the strength of uncorroded concrete after 12 years is increased by 9.5% and the strength of corroded concrete after 12 years is reduced by 56.2%. The results of the strength tests and pore structure tests show that sulphate has a significant impact on concrete strength after 12 years of field tests. This study will contribute to improve long‐term performance of the concrete, provide guidance for concrete structure design in corroded areas, and suggested that increasing attention should be paid to the effects of sulphate on concrete performance.

Research on the Corrosion/Permeability/Frost Resistance of Concrete by Experimental and Microscopic Mechanisms Under Different Water\u2013Binder Ratios

To study the influence of different water–binder ratios on the corrosion, permeability, and freezing properties of concrete, we produced different strengths of concrete with respective water–binder ratios of 0.32, 0.38, 0.50, and 0.66. The corrosion resistance of the concrete was studied via three corrosion methods: full immersion, half immersion, and dry and wet cycles. The impermeability and frost resistance of concrete with different water–binder ratios were tested and analyzed. The test results show that the corrosion modes in order from strong to weak were dry and wet cycles, half soaking, and full soaking. The relative dynamic elasticity modulus and freeze–thaw index were used to evaluate the frost resistance of concrete based on the analysis of three indices of frost resistance. To study the internal mechanism of corrosion of concrete with different water–binder ratios, microscopic pore structure testing of the concrete was conducted using a Micromeritics AutoPore IV 9500 Series instrument. The porosimeter studies show that the smaller the water–binder ratio, the more small pores and the denser the concrete. The smaller the water–binder ratio, the higher the strength and the better the corrosion, permeability, and frost resistance.

Ingestion of caffeine links dopamine and 5-hydroxytryptamine release during half immersion in 42°C hot water in a humans.

The aim of this study was to investigate the serum serotonin, prolactin, and plasma dopamine levels in humans with and without caffeine ingestion during and after passive heat loading (half immersion in 42°C hot water). Thirty male volunteers participated in the randomized experiment (control group, n=15 vs. caffeine ingestion group, n=15, 3 mg/kg). After 60 min, passive heat loading was conducted for 30 min. Blood samples were collected and assessed for serum serotonin, dopamine and prolactin with and without caffeine during and after passive heat loading. Serum serotonin was significantly lower in the caffeine ingestion group compared to the control group after passive heat loading for 30 min (Post) (P<0.05) and also after 60 min of resting (P<0.01). Dopamine and prolactin were significantly higher in the caffeine ingestion group than in the control group at the Post time point (P<0.001). In conclusion, 3-mg/kg caffeine ingestion prior to passive heat loading can alter central serotonergic and dopaminergic activity, which may contribute to reduced central fatigue and subsequently, to reduced general fatigue. Prolactin responses during passive heat loading were also significantly related to caffeine ingestion in this study. However, the inhibitory effects of dopamine on prolactin by caffeine remain to be elucidated.

Multi-stage mechanical behavior and failure mechanism analysis of CFRP/Al single-lap bolted joints with different seawater ageing conditions

This paper aims to investigate the mechanical response behavior of CFRP/Al single-lap bolted joints in marine environment. The joints with four interference fit sizes (0%, 0.42%, 2.14% and 3.02%) were prepared, and fully and half immersed in 3.5% sodium chloride solution with a controlled temperature of 30 °C for four months. Single-lap bearing tests were carried out to evaluate the mechanical behavior and failure mode of the CFRP/Al bolted joints after seawater ageing. Scanning electron microscope (SEM) was used to analyze the environmental damage and failure mechanism of structures. The results show that the critical load-bearing capacity and the maximum friction force at the overlap gradually decreased with the increasing of ageing time, and it was more serious in half immersion ageing environment compared with full immersion. The interference fit significantly improved the mechanical properties of joints, especially for 2.14% interference fit. Environmental damage such as pitting, delamination and fiber-matrix interface debonding was all aggravated with the increasing ageing time but suppressed by interference fit. In addition, the failure modes of structures were bearing failure and shear-out failure of CFRP, and the failure mechanism was delamination for unaged structures, the interlayer shear damage for aged structures.

Deterioration of the FRP-to-concrete interface subject to moisture ingress: Effects of conditioning methods and silane treatment

Fiber reinforced plastics (FRP) composites have emerged as one popular material in retrofitting/rehabilitation of concrete structural members in last decades. The long-term durability of the FRP-to-concrete interface in aggressive environments plays a critical role in the success of this technique. An experimental program has been carried out in this study to examine the effect of moisture on the deterioration of the FRP-to-concrete interface. In addition to conditioning the specimens through fully submerging the specimens in water, a new method to condition the specimen through submerging only the bottom half of the specimen in water was used in this study. Testing results suggest that the fracture toughness of the FRP-to-concrete interface conditioned through half immersion is significantly higher than that of the interface conditioned through full immersion. Three possible responsible mechanisms have been identified: different moisture distributions along the epoxy–concrete interface induced by conditioning methods, faster moisture diffusion through the epoxy–concrete interface, and hygroscopic swelling stress induced by the swelling of the epoxy after absorbing moisture. The significant effect of the conditioning method on the durability of the FRP-to-concrete interface makes us postulate that the laboratory testing based on full immersion of the specimen in water could exaggerate the deterioration of the interface induced by the moisture in real applications, in which the interface is exposed to air, rather than water. In such a case, neither the moisture diffusion along the epoxy–concrete interface nor the swelling of the interface is as significant as in the case of full immersion in water used in the laboratory testing. In addition, this study also evaluated the potential of silane coupling agent on enhancing the durability of the FRP-to-concrete interface in moisture conditions.

3-D finite element process simulation of micro-end milling Ti-6Al-4V titanium alloy: Experimental validations on chip flow and tool wear

Finite element (FE) simulation of machining can be used as a replacement or a supplementary to the physical experiment allowing an analysis to be performed at a lower cost. Besides, FE simulation can offer predictions of process variables which are difficult to obtain by experiment. This paper provides investigations on 3-D FE modeling and simulation of micro-end milling process for Ti-6Al-4V titanium alloy. 3-D FE models proposed for full-immersion, half immersion up and down milling are utilized to study the influence of increasing tool edge radius due to wear on the process performance of micro-end milling. Predicted 3-D chip flow and shapes are compared against the experiments which provided reasonably good agreements. Tool wear along the micro-end milling tool is predicted and validated with experiments. The results of this study indicated that tool wear has a significant impact to the cutting force, cutting temperature, tool wear rate, chip flow and burr formation. In addition, a comparison of 3-D and 2-D FE simulations is provided giving a better understanding of utilizing their predictions.

Caffeine links dopamine and serotonin release during passive heat loading

Caffeine links dopamine and serotonin release during passive heat loading

Passive heat loading links lipolysis and regulation of fibroblast growth factor-21 in humans

There is relativley little information on the serum biomarkers of heat stress. Therefore, the goal of this study was to verify the effect of passive heat loading (PHL) on the expression of fibroblast growth factor-21 (FGF21) and free fatty acids (FFAs). Four PHL protocols based on intensity (39°C vs. 43°C, leg immersion, 30min) and type (leg vs. half immersion, 42°C, 30min) were used. Each protocol was applied on a 2day cycle to 12 healthy adult males (age, 22.4±2.9 years; height, 174.1±4.6cm; weight, 71.3±5.6kg; body mass index, 23.1±3.0). The subjects were categorized into two groups according to the study design (randomized, with a parallel trial). Body temperature, FGF21 and FFAs were determined prior to PHL, immediately and 60min after PHL. Body temperature was significant higher (43°C) than the 39°C measured under identical PHL type (leg immersion). PHL was effective for the expression of FGF21 and for lipolysis. The quantitative levels of FGF21 and FFA increased with increasing temperature (39°C<42°C<43°C). A significant difference in the quantitative levels of FGF21 and FFAs was also evident based on the type of PHL (leg<half immersion) even when PHL was applied at the same temperature (42°C). In conclusion, PHL was effective for expressing FGF21 and for lipolysis. Therefore, PHL may be expected to help in the reduction of body fat. Additionally, when the identical type (leg immersion) of PHL is applied, a loading temperature of 43°C is more effective for expressing FGF21 and for lipolysis than temperatures of 39°C and 42°C, and half immersion is more effective than leg immersion at 42°C.

비절삭저항 상수 변화에 따른 절삭력 분석

ABSTRACT Considering the run-out effect and cutting force coefficients, the cutting force profile of half immersion end-milling was analyzed in detail. The effects of three specific cutting-force coefficients and three edge-force coefficientsare verified. Through a detailed investigation, it is proved that the radial cutting force coefficients and arethe major factors which increase the cutting forces Fx and Fy in end-milling. However, the axial cutting force coefficients have no influence on the force Fx and Fy changes in end-milling. Also, the analyzed end-milling force model shows good consistency with the actual measured force with regard to Fx and Fy. Thus, this model can be used for the prediction ofthe force history in end-milling with run-out,and it incurs a different force history with different start and exit immersion anglesas well as holding effects. Key Words : Force modelling(절삭력모델링), Immersion angle(물림각), Run-out(런아웃), Cutting force coefficient(절 삭력상수), Edge force coefficient(모서리절삭력상수)

Corrosion of Reinforced Concrete in Accelerated Tests

In order to study the correlation between accelerated corrosion and natural corrosion, reinforced surface morphology, steel potentials and corrosion quality were investigated by using full immersion and half immersion in this paper. The results showed that the effort of half immersion accelerated corrosion was similar to natural corrosion, and each of the tendencies of potential change was same, but the mechanisms of corrosion were different. The degree of steel corrosion, estimated by Faraday’s law, was slightly higher than the level of actual corrosion.

Improved dynamic cutting force model in ball-end milling. Part I: theoretical modelling and experimental calibration

An accurate cutting force model of ball-end milling is essential for precision prediction and compensation of tool deflection that dominantly determines the dimensional accuracy of the machined surface. This paper presents an improved theoretical dynamic cutting force model for ball-end milling. The three-dimensional instantaneous cutting forces acting on a single flute of a helical ball-end mill are integrated from the differential cutting force components on sliced elements of the flute along the cutter-axis direction. The size effect of undeformed chip thickness and the influence of the effective rake angle are considered in the formulation of the differential cutting forces based on the theory of oblique cutting. A set of half immersion slot milling tests is performed with a one-tooth solid carbide helical ball-end mill for the calibration of the cutting force coefficients. The recorded dynamic cutting forces are averaged to fit the theoretical model and yield the cutting force coefficients. The measured and simulated dynamic cutting forces are compared using the experimental calibrated cutting force coefficients, and there is a reasonable agreement. A further experimental verification of the dynamic cutting force model will be presented in a follow-up paper.

A Control System for Chatter Avoidance by Ramping the Spindle Speed

This paper presents a new control system for chatter avoidance in milling. The control system monitors the cutting process using a statistical indicator named the R-value which is computed from the cutting force signal. When chatter is detected, the control system ramps the spindle speed in search of a speed at which chatter ceases. The system does not involve time consuming computations and therefore is suitable for on-line implementation. Also, it does not interrupt the cutting process by halting the feedrate or the spindle speed. Simulations showed that the control system has a significant chatter avoidance potential in the high speed range, and also for partial and full immersion cuts. The system was implemented successfully to avoid chatter in slotting and half immersion down milling.

Machining Chatter of End Mills With Unequal Modes

This paper further investigates the effect of reducing the contribution of the mode coupling mechanism to machining chatter. This reduction was achieved in a previous investigation by making the cutting tool more compliant in one direction. Thus, in particular, the objective of the present work was to study the effect of varying the orientation angle between the flexible mode and the leading edge of the first cutting tooth. The study covered slotting and half immersion, up and down milling. The modified cutters, irrespective of the orientation angle, are shown to outperform the regular cutter in slotting over a wide speed range. This angle is found to have a very strong effect in half immersion. The study is conducted using both computer simulation and cutting tests using aluminum.