Basic Cycle Research Articles

Combined direct oxy‐combustion and concentrated solar supercritical carbon dioxide power system—Thermo, exergoeconomic, and quadruple optimization analyses

For the global future energy systems, concentrated solar power (CSP) and direct CO2 capture systems are of the most important key technologies, however, each of these systems has shortcomings. This study addresses the solar intermittency and power control complexity of the CSP systems and the substantial energy penalty of the direct oxy-combustion (DOC) supercritical carbon dioxide (sCO2) power systems by integrating both systems. Herein, innovative power cycle configurations that integrate the CSP tower system with DOC sCO2 power cycle are introduced. The configurations include two basic cycles for comparison and validation purposes and three integrated cycles. The basic configurations are: an intercooled sCO2 power cycle driven by DOC system (S1), and a stand-alone basic CSP tower system (S2). The integrated configurations are: CSP/DOC system where the CSP works as a preheater (S3); CSP/DOC system where the CSP works as a reheater (S4); and CSP/DOC system where each system heats part of the working fluid to drive its high-pressure turbine (S5). The hybrid configurations reduce the fuel and the parasitic power consumptions of the basic DOC systems (S1) and reduce the capital cost associated with the conventional CSP systems (S2) by eliminating the need for thermal storage. Over practical ranges of operational parameters, comprehensive thermoeconomic, exergoeconomic, and optimization analyses for the proposed configurations are performed. Compared to the conventional CSP system, the LCOE of the hybrid system is lower by 50%. Among the hybrid configurations, the energetic and exergetic performances of S4 are the best with the lowest LCOE. According to the optimization analysis, S4 has a thermal efficiency of 55.29% at LCOEs of 7.705¢/kWh. S3, S5, S2, and S1 have thermal efficiencies of 52.90%, 48.72%, 45.56%, and 40.54% at LCOE of 7.970, 8.138, 7.864, and 6.351¢/kWh, respectively.

Performance analysis of an ejector-assisted two-stage evaporation single-stage vapor-compression cycle

• An ejector-assisted 2-stage evaporation 1-stage vapor-compression cycle is proposed. • New cycle works for different refrigerants, especially for CO 2 transcritical cycle. • Energy savings depend on reasonable design and variable operating conditions. For actual vapor-compression refrigeration or heat pump systems with variable-temperature heat reservoirs, two-stage evaporation cycle is an efficient way to improve the coefficient of performance (COP). However, its application is limited because the two-stage evaporation cycle requires two individual suction pressures carried out by two cylinders or two compressors. To solve this problem, a two-stage evaporation cycle with a common single-stage compressor is proposed. An ejector is applied to lift the lower evaporation pressure up to the higher evaporation pressure or the compressor suction pressure. A thermodynamic model is developed to analyze its performance. Numerical results indicate that the COP of the novel cycle is 12.1% higher than the ejector cycle, 6.9% higher than the two-stage evaporation cycle and 22.0% higher than the basic refrigeration cycle under rated operating conditions. The exergy analysis indicates that TSEC-E can reduce 49.6% exergy loss of expansion process and 21.5% exergy loss of heat transfer process in evaporators in comparison with the basic refrigeration cycle. Although TSEC-E is applicable with various refrigerants, particularly it is more effective for CO 2 transcritical cycle. Moreover, performance improvement of the novel cycle under variable operating conditions is numerically investigated.

Design of biobased supply chains on a life cycle basis: A bi-objective optimization model and a case study of biobased polyethylene terephthalate (PET)

Bioplastics are considered a sustainable alternative to (partly) substitute fossil-based plastics. Nevertheless, it is still uncertain if the use of biomass for the production of bioplastics can mitigate the environmental impact of fossil-based plastics and simultaneously provide economic benefits. An optimization model is proposed to design biobased supply chain networks that account for economic (total costs) and environmental (greenhouse gas emissions) criteria. Life cycle costing and life cycle assessment were used to evaluate the economic and environmental costs of the biobased polyethylene terephthalate (PET) production using sugar beet and wheat as feedstock. The 100% biobased PET production evidenced higher economic and environmental costs than the 30% biobased PET production. The feedstock selection played a key role, whereas the use of wheat for both 30% and 100% biobased PET had the highest costs and greenhouse gas emissions. It is highlighted that the economic performance of the biobased terephthalic acid (PTA) production, the feedstock selection (sugar beet), and the carbon tax scenario (>100 €/t CO 2 ) are key parameters for designing a sustainable biobased PET supply chain.

Cycle analysis of Directed Acyclic Graphs

In this paper, we employ the decomposition of a directed network as an undirected graph plus its associated node meta-data to characterise the cyclic structure found in directed networks by finding a Minimal Cycle Basis of the undirected graph and augmenting its components with direction information. We show that only four classes of directed cycles exist, and that they can be fully distinguished by the organisation and number of source–sink node pairs and their antichain structure. We are particularly interested in Directed Acyclic Graphs and introduce a set of metrics that characterise the Minimal Cycle Basis using the Directed Acyclic Graphs meta-data information. In particular, we numerically show that transitive reduction stabilises the properties of Minimal Cycle Bases measured by the metrics we introduced while retaining key properties of the Directed Acyclic Graph. This makes the metrics a consistent characterisation of Directed Acyclic Graphs and the systems they represent. We measure the characteristics of the Minimal Cycle Bases of four models of transitively reduced Directed Acyclic Graphs and show that the metrics introduced are able to distinguish the models and are sensitive to their generating mechanisms.

Influence of mixed fibers on fly ash based geopolymer resistance against freeze-thaw cycles

The freeze-thaw cycle is one of significant indexes to evaluate the durability of the geopolymer. In this study, experimental research was employed to characterize the freeze-thaw behavior of mixed fiber-reinforced geopolymer mortars. Modified multi-walled carbon nanotubes (MWCNTs) with mass fractions of 0.05%, 0.10% and 0.15% and PVA fibers with volume fractions of 1.50%, 2.00% and 2.5% were used as the experimental parameters. The geopolymer mortar without modified MWCNTs and PVA fibers was used as the control. Visual inspection, relative dynamic elasticity modulus and mass loss were adopted to evaluate the resistance against freeze-thaw cycles of mixed fiber reinforced geopolymer mortars. The freeze-thaw damage model was built on the basis of the freeze-thaw cycles and the relative dynamic elasticity modulus. In addition, the pore structure characteristics and the micro-morphology were characterized by means of mercury intrusion porosimetry (MIP) and field emission scanning electron microscopy (FESEM). The experimental results show that the control geopolymer mortar is destroyed in 50 freeze-thaw cycles, while the mixed fiber reinforced geopolymer mortar incorporated with 0.10% modified MWCNTs and 2.00% PVA fibers can withstand 175 freeze-thaw cycles. Meanwhile, the mechanism of freeze-thaw failure and improvement of geopolymer mortars were revealed from microscopic and mesoscopic aspects. The MIP analysis can well establish that the utilization of modified MWCNTs and PVA fibers is an effective way to decrease the porosity of geopolymer mortars. The nano-nucleation effect, nano-filling effect, crack arrest effect and mechanical interlocking effect of modified MWCNTs make geopolymer mortars denser, decreasing the percentage of the capillary pore. The mechanical interlocking effect of PVA fibers ounterbalances the internal stress, which is caused by freezing the water.

Semi-empirical analysis of HFC supermarket refrigeration retrofit with advanced configurations from energy, environmental, and economic perspectives

F-gas phase-down schedules will remove most of the HFCs (hydrofluorocarbons) used in refrigeration systems in the short term. Besides refrigerant substitution, configuration modifications can be considered in existing installations to increase energy efficiency. Basic cycle, direct injection, economiser, parallel compression, and cascade configurations with internal heat exchanger have been proposed to increase the energy efficiency of a supermarket refrigeration system when replacing R-404A with R-449A at low and medium temperatures. Both systems are based on indirect expansion and are equipped with a subcooler. Their regular operation was recorded using R-404A and R-449A during a representative period. Then, a semi-empirical approach is followed to determine R-449A energy performance with each proposed configuration. Only parallel compression (PC) and basic cycle with internal heat exchanger (IHX) benefit energy performance, highlighting the medium temperature (MT) system. However, this benefit is not extended to the environmental analysis because the R-449A charge in PC significantly increases. Moreover, additional PC components extend the expected payback period, and a drop-in replacement is financially more interesting. Therefore, using R-449A with minor modifications in the MT and LT R-404A refrigeration system decreases 52% and 60% carbon footprint, respectively. The payback period of this action is below one year in both circuits. This study provides a semi-empirical methodology for existing systems to predict alternative refrigerants' energy performance.

Welcome to the Hive! Honey Bee 4-H Project Book

The purpose of this publication is to provide a 4-H project book that discusses honey bees and their importance to our nation’s agriculture. The intent is to introduce the world of honey bees to youth ages 8 to 12, with or without any previous beekeeping background or knowledge. This book consists of six sections that familiarize youth with the honey bee’s basic anatomy and life cycle, the three members of the honey bee colony, their roles and responsibilities, and colony communication. Each section has been designed to give youth a brief introduction to a topic and offers activities building on that topic. Written by Megan Hammond, Amy T. Vu, Mary Bammer, Emily Helton, Karen Henry, Jessica Sullivan, and James D. Ellis; 56 pp.https://edis.ifas.ufl.edu/4h419

Quantitative goals for research output and scholarly impact to enhance basic science R01 grant renewal for cardiothoracic surgeons

ObjectivesCardiothoracic (CT) surgeons with National Institutes of Health (NIH) R01 funding face a highly competitive renewal process. The factors that contribute to successful grant renewal for CT surgeons remain poorly defined. We hypothesized that renewed basic science grants are associated with high research output and scholarly impact during the preceding award cycle. MethodsUsing a database of academic CT surgeons (n = 992) at accredited training institutions in 2018, we identified basic science R01 grants awarded to CT surgeon principal investigators since 1985. Data for each award were obtained from publicly available online sources. Scholarly impact was evaluated using the NIH-validated relative citation ratio (RCR), defined as an article's citation rate divided by that of R01-funded publications in the same field. Continuous data are presented as medians and analyzed using the Mann–Whitney test. ResultsWe identified 102 basic science R01 award cycles, including 33 that were renewed (32.4%). Renewed and nonrenewed awards had a similar start year and funding period. Principal investigators of renewed versus nonrenewed awards were similar in surgical subspecialty, research training, attending experience, academic rank, and previous NIH funding. Renewed awards produced more publications per year over the funding cycle (3.4 vs 1.5; P = .0010) and exhibited a greater median RCR during the funding cycle (0.84 vs 0.66; P = .0183). ConclusionsCT surgery basic science R01 grants are associated with high research output and scholarly impact. At the 50th percentile among renewed grants, CT surgeons published 3.4 funded manuscripts per year with a median RCR of 0.84 during the previous award cycle.

Structural basis for client engagement and chaperone cycling by human mitochondrial Hsp60

The mitochondrial (mt) molecular chaperone Hsp60 is critical in proteostasis by catalyzing ATP-dependent folding of mitochondrial proteins. In a manner analogous to bacterial GroELS, mtHsp60 is proposed to function by enclosing unfolded ‘client’ proteins in its central chamber, formed in part by its co-chaperone mtHsp10, allowing them to fold without interference from other cellular components. Mutations in mtHsp60 cause severe neurodegenerative diseases termed hereditary spastic paraplegias, and mtHsp60 expression is upregulated in a subset of cancers, making this chaperone a significant therapeutic target.

Experimental investigation on an R290-based organic Rankine cycle utilizing cold energy of liquid nitrogen

Organic Rankine cycle (ORC) has been widely used to utilize low-grade waste heat from low, medium, and high-temperature heat sources. Meanwhile, the research of the ORC operates in the cryogenic temperature has also attracted much attention due to the increasing requirement of liquid natural gas (LNG). However, there is still a lack of experimental research on the cryogenic ORC. In this paper, the experimental study of a cryogenic ORC using a semi-hermetic scroll expander and propane (R290) has been investigated. Liquid nitrogen is used as the cryogenic cold source in this system while the circulation water is used to simulate the low-grade waste heat. The system performance of utilizing the cold energy of the liquid nitrogen and thermal energy of the circulation water has been investigated. First, the effects of the evaporation pressure and pressure drop on system performance are examined. Moreover, the system performance between the regenerative organic Rankine cycle (RORC) and basic organic Rankine cycle (BORC) has been compared. The experimental results indicate that evaporation pressure has a significant effect on system performance, and different optimum evaporation pressure will be obtained under different liquid nitrogen mass flow rates. The maximum electrical power 673.59 W, system thermal efficiency 6.78%, and cold energy utilization efficiency 12.32% can be obtained, while the evaporation pressure and liquid nitrogen mass flow rate are 1.36 MPa and 120 kg/h, respectively. What’s more, the results also indicate that the pressure drop exhibits a high sensitivity on system performance, and there is a clear linear proportional relationship between pressure drop and electrical power. Furthermore, the comparison results show that RORC has a better system performance than BORC. The experimental results provide design and optimal operation strategy for the cryogenic organic Rankine cycle.

Performance investigation and optimization of the magnetic refrigeration cycle with two-stage magnetization and demagnetization

Recently, room-temperature magnetic refrigeration (MR) has attracted immense attention as a prospective substitute for vapor-compression refrigeration. The greatest obstacles faced by existing room-temperature MR prototypes are their inadequate cooling capacity, small temperature span, and low efficiency. A potential solution to these issues could include constructing new MR cycles based on regeneration. Therefore, in this paper, we constructed a few potentially efficient two-stage MR thermodynamic cycles. The thermodynamic model of the two-stage MR cycle was established to evaluate its cyclic performance. The performances of different two-stage MR cycles were investigated, and compared with that of the basic MR cycle. The results revealed that the two-stage MR cycles always performed better than the basic MR cycle, on account of the increased cooling capacity, and the reduced magnetic work. Moreover, it was found that the two-stage MR cycle with two-stage magnetization and demagnetization was the optimal configuration. Therefore, further investigation was conducted on the performance of the optimal two-stage MR cycle. The effects of certain key parameters (such as, the intermediate magnetic field, and the cold- and hot-end operating temperatures) on the cyclic performance were carefully analyzed. It was observed that when the operating temperature was between 280 K and 310 K, a magnetic field ratio between 0.371 and 0.492 was optimal for achieving the best cyclic performance. Maximum thermodynamic perfection of approximately 0.635 was obtained, which was 27.55% greater than that of the basic MR cycle. Furthermore, we investigated the influence of adiabatic irreversibility on the cyclic performance. The results demonstrated that when adiabatic irreversibility factors ranged between 0.9 and 1, the two-stage MR cycle consistently performed better than the basic MR cycle. Thus, this paper can provide a theoretical direction for the design and optimization of efficient room-temperature magnetic refrigerators employing new thermodynamic cycles.

Life cycle of the tick Ixodes ricinus (L.) (Acari: Ixodidae) in the North-West of Russia

The characters of the life cycle and demographic processes of Ixodes ricinus (L., 1758), (Acari: Ixodidae) populations in the North-West of Russia were studied using methods of the long-term observations of ticks in insets in the natural biotopes (2013–2018). It was found that in the North-West of Russia, I. ricinus had a long period of seasonal activity (from April until October) and a long calendar age. Larvae, nymphs, as well as adults of both sexes can remain active for up to 12–15 months when they meet with appropriate host and feed successfully. Up to 9±0.8% of adults can overwinter twice and remain active until the end of June of the third year of their life (23 months). The I. ricinus tick at every developmental stage forms a certain sub-group of population in August–September. Due to the highly prolonged life the larvae, nymphs and females of I. ricinus are able to feed, and the females can lay eggs during their entire active period from April till October. At the same time, larvae and nymphs that feed from April to June molt in the year of feeding, and their development proceeds according to a three-year scenario. The females feeding from April to June can produce offspring during the same season, thus forming a 3-year developmental cycle. By contrast, all individuals (larvae, nymphs and females) feeding from July to October molt to the next stage in August–September of the following year. Females feeding in July–September can lay eggs both in the year of feeding and after winter diapause. This leads to an increase in the duration of the basic 3-year developmental cycle and its complexity. If the ticks molted the next year after feeding only once in the life cycle, the whole life cycle would increase by a year. If they did it in every developmental stage, then the life cycle would increase by three years. Thus, the total duration of development of ticks of one generation may last from 3 to 6 years. Some adult ticks (not more than 9±0.8% in the population) can remain active until the end of June of the seventh season.

Multiparametric optimization of a reheated organic Rankine cycle for waste heat recovery based repowering of a degraded combined cycle gas turbine power plant

The study has conducted multiparametric optimization of a newly modified double stage reheated organic Rankine cycle configuration for the objective function of specific work output and its comparison with other conventional configurations of the organic Rankine cycle for the waste heat recovery-based repowering of a degraded combined cycle gas turbine power plant using R245fa, R113, and R141b as the working fluids. Thermodynamic performance of the triple cycle formed by integrating each organic Rankine cycle configuration with the combined cycle gas turbine unit is assessed in terms of repowering, specific fuel consumption and specific water consumption along with the associated greenhouse gas emissions. 24-hour performance variation of the combined cycle gas turbine unit has been incorporated in the analysis. It is found that the double stage reheated organic Rankine cycle configuration has outperformed other configurations in terms of thermodynamic performance. Triple cycle for the double stage reheated organic Rankine cycle has resulted in an average of 1.37% increase in net power output for the working fluid R141b, equivalent to 5.10 MW of additional power output. The thermal efficiency of the triple cycle for double stage reheated organic Rankine cycle has increased by 1.40%, whereas the specific fuel consumption and specific water consumption have reduced by 1.28% and 3.35%, respectively using R141b as the working fluid. The highest waste heat recovery potential is exhibited by the integrated basic organic Rankine cycle configuration for the working fluid R245fa, recovering 30,840 kW of waste heat, equivalent to the burning of 2467.2 kg/hr of CH4 and 6784.7 kg/hr CO2 emissions.

Analysis of USAID/Georgia Supported Basic Education Program First Cycle Implementation

The article highlights Akaki Tsereteli State University's involvement and participation in wide school reforms to establish student-centered education in Georgia. School educational reform cannot proceed and succeed without the direct involvement of the universities which carry out teacher preparation programs. Unequivocally, there should be close cooperation and collaboration between these two institutions to reach the desirable and targeted outcomes. The purpose of the article was to present the results of the survey, which was intended to assess the effectiveness of training conducted by the university trainers during the first phase of the new school reform in Georgia which focused on achieving student-centered learning. The selected trainers from the eight partnering universities were supposed to cover 2075 schools throughout Georgia (373 schools in Imereti Region) to train leader teachers and help the institution to develop new instructional methods, more specifically, to develop a school curriculum based on constructivist educational principles and apply it into practice. The survey findings assisted Pedagogical faculty in identifying existing curriculum gaps and discrepancies and taking measures to bridge them by modifying and supplementing them with the necessary content.

Prevalence of common mental disorders among medical students during the Covid-19 pandemic

Abstract: Introduction: Common mental disorders (CMD) have been frequently identified among university students in the health area, especially in Medicine. It is believed that characteristics inherent to the course have a potential influence on the student’s mental health. When adding the pandemic context, with its inherent social restrictions, the psychological determinants related to the unknown pathology and the fear of the rapid spread of the new coronavirus, there is the possibility of increasing the risk factors for psychological distress in this population. Objective: To estimate the prevalence of CMD among medical students during the COVID-19 pandemic, analyzing its main determinants in the academic, social and economic spheres. Method: Cross-sectional study, carried out with 388 medical students in Salvador/BA., Data on sociodemographic and academic aspects, life habits, comorbidities and symptoms of non-psychotic disorders were collected using the Google Forms platform, measured by the Self-Reporting Questionnaire (SRQ-20). Results: The prevalence of CMD was 39.7% among medical students, with 47.4% in the basic cycle, 40.3% in the clinical cycle and 12.3% in the internship period. Among the factors associated with the emergence of CMD are sedentary lifestyle, smoking, use of substances that enhance academic performance, dissatisfaction with one’s academic performance, poor sleep quality, lack of appetite, frequent headaches, poor digestion, suicidal ideation and sadness. There was a higher rate of non-psychotic mental disorders among women, with no difference regarding the academic cycle and the administrative type of the educational institution. Conclusion: During the COVID-19 pandemic, a significant prevalence of CMD was demonstrated among female, white, single medical students who live with family members and do not have their own income. Although studies suggest an increase in the prevalence among university students at the present time, the data from the present study remain in agreement with the literature data prior to the pandemic, showing that the medical course itself is the main risk factor for higher rates of CMD in this population. However, further studies on the long-term impact of the pandemic on the mental health of university students are still necessary.

Prevalence of common mental disorders among medical students during the Covid-19 pandemic

Abstract: Introduction: Common mental disorders (CMD) have been frequently identified among university students in the health area, especially in Medicine. It is believed that characteristics inherent to the course have a potential influence on the student’s mental health. When adding the pandemic context, with its inherent social restrictions, the psychological determinants related to the unknown pathology and the fear of the rapid spread of the new coronavirus, there is the possibility of increasing the risk factors for psychological distress in this population. Objective: To estimate the prevalence of CMD among medical students during the COVID-19 pandemic, analyzing its main determinants in the academic, social and economic spheres. Method: Cross-sectional study, carried out with 388 medical students in Salvador/BA., Data on sociodemographic and academic aspects, life habits, comorbidities and symptoms of non-psychotic disorders were collected using the Google Forms platform, measured by the Self-Reporting Questionnaire (SRQ-20). Results: The prevalence of CMD was 39.7% among medical students, with 47.4% in the basic cycle, 40.3% in the clinical cycle and 12.3% in the internship period. Among the factors associated with the emergence of CMD are sedentary lifestyle, smoking, use of substances that enhance academic performance, dissatisfaction with one’s academic performance, poor sleep quality, lack of appetite, frequent headaches, poor digestion, suicidal ideation and sadness. There was a higher rate of non-psychotic mental disorders among women, with no difference regarding the academic cycle and the administrative type of the educational institution. Conclusion: During the COVID-19 pandemic, a significant prevalence of CMD was demonstrated among female, white, single medical students who live with family members and do not have their own income. Although studies suggest an increase in the prevalence among university students at the present time, the data from the present study remain in agreement with the literature data prior to the pandemic, showing that the medical course itself is the main risk factor for higher rates of CMD in this population. However, further studies on the long-term impact of the pandemic on the mental health of university students are still necessary.

Design of a hydrogen-powered bicycle for sustainable mobility

Hydrogen-powered vehicles are emerging as a key source for a clean and sustainable mobility scenario. In particular, hydrogen technologies have a great potential for light mobility in urban areas, where traffic congestion may cause very high levels of local pollution. In this context, hybrid fuel cell/battery vehicles represent a promising solution, since they allow for extended driving range and short recharge time, which are two of the major concerns related to electric propulsion, in general. In this work, a new plug-in fuel cell electric bicycle concept is presented, where the on-board energy storage is realized by means of an innovative system integrating a battery pack with a metal hydride hydrogen tank. This solution allows to achieve very high performance in terms of riding range, which are unattainable with traditional battery electric bicycles. In particular, the hybrid energy storage system is conceived to provide an optimal thermal management of the two integrated components. The proposed design is developed on the basis of typical duty cycles acquired during on-road measurements. A prototype of the bicycle is then realized and bench-tested in order to assess design consistency and to evaluate its performances. The results show that the riding range of the new hydrogen-fuelled bicycle is about three times higher than the one for a similar electric bicycle.

Energy and exergy analyses of a cryogenic reverse Brayton cycle with waste heat recovery

In a typical reverse Brayton cycle (RBC), a great amount of compression heat is just wasted, for which there are two different temperature levels. The basic organic Rankine cycle (ORC) and the regenerative ORC with improvement were then applied to recover waste heat. Considering that the waste gas after ORC was reused, the total exergy efficiency was defined to evaluate different cycles. A simulation method was conducted to predict cycle performances and the coupling between RBC and ORC was clarified. The feasibility of replacing the after cooler with the evaporator was analysed. Compared with the typical RBC, a relative improvement of 18.2% was achieved for COP in the combined system and the cooling exergy efficiency was increased by 16.8%. The correspondence of the total exergy efficiency and the COP of whole system exited in different cycle layouts. Proper organisation of the RBC with ORC could promote the energy efficiency.

Monitoring the high-speed engine application using ferro magnetic system

The business focuses on high velocity machine innovation with charged rotor frameworks. Various control hardware and exact movement sensors are fundamental when searching for elite execution machines. It is significant that basic modern cycles have a remote observing framework that can give estimation information to examination. This paper proposes an Internet of Things (IoT) - based following idea for a fast machine with an attractive current rotor framework that utilizations estimated rotor position information for conclusion. The unevenness of the rotor framework is observed with a blend of Walsh- Hadamard Fourier change (FWFT) and the handled information is put away in the cloud.

The influence of tool traverse speed on the low cycle fatigue properties of AZ31 friction stir welded joints

This paper describes the basic low cycle fatigue properties of AZ31 friction stir welded joints obtained by different welding velocities: 150, 300, 600, and 900 mm/min with the constant value of 1600 rpm tool rotation speed. The performed LCF tests at various strain amplitudes: 0.25, 0.35, 0.5 (for R=-1) together with fractography analysis allowed to state that the value of welding velocity has no significant impact on the LCF behavior of AZ31 FSW in the investigated range. The tests also revealed that the AZ31 FSW joint is characterized by three stages of fatigue life: a very short period of cyclic hardening (up to 100 cycles), cyclic stabilization, and a relatively long period of cyclic softening until failure. All joints are free of imperfections and tend to fail in the heat-affected zones.