Actual Loading Conditions Research Articles

Methodology for ro-ro ship and fleet sizing with application to short sea shipping

ABSTRACTA novel methodology is developed for determining the characteristics of a cargo roll-on/roll-off (ro-ro) ship and the fleet size required for a given short sea shipping route. The ship and required fleet size to satisfy the transportation demand (for each pair of speed and freight rate) are determined using a database of existing cargo ro-ro ships to obtain the main technical characteristics of the most suitable ship. The time charter, voyage costs and revenue are then calculated considering the technical characteristics of each ship. Fuel costs are corrected for the actual ship speed and loading condition. A number of restrictions in the transportation problem are considered leading to the exclusion of unfeasible solutions. The maximum profit over the period of a year is identified among the feasible pairs of speed and freight rate. This general methodology is applied in a case study that considers the route between Leixões (Portugal) and Rotterdam (Netherlands). The study allows the identification of the most suitable ship and fleet sizes for different market penetration levels and quantifies the impact on shipping company profit of changes in parameters such as fuel costs, time charter costs, emission control area, installed propulsion power and stacking factor.

Accurate predictions for optimum design of a T-shaped fin under an actual wet load condition

An effort is made to develop an analytical model for predicting the thermal performance and optimum design parameters of a wet T-shaped fin by considering variable thermal conductivity of the fin material and variable convective heat transfer coefficient. The temperature distribution is obtained by solving the highly non-linear governing equations by employing three different analytical techniques, namely Variational Iteration Method, Adomian Decomposition Method and Differential Transform Method, and validated by that obtained from the Finite Difference Scheme. The optimisation analysis is carried out by employing the Lagrange multiplier technique. A complete multivariable geometric optimisation is executed, where all the geometric parameters are varied simultaneously to establish the optimum condition. Furthermore, the analysis is done for both insulated and convective fin tip conditions and a comparative analysis on the temperature distribution, fin performance and optimum design parameters is presented between these two cases.

Effects of uncertainties in loading conditions of bulk carriers on hull girder still water loads

This paper reports a study on the uncertainties in assessing loading conditions of handy size bulk carriers. Loading conditions and the corresponding hull girder still-water loads are important for the safety of bulk carriers. Unfortunately, statistical studies on this topic remain very few, partly because of the difficulty in fully understanding the impact of loading/unloading operation process and partly because of intrinsic uncertainties in measuring cargo loading conditions data. Three handy-size bulk carriers were investigated and their actual loading conditions, spanning several voyages in 22 months, were collected. Statistical analyses of the collected data resulted in an estimate of the uncertainties in the loading/unloading process. Based on these analyses, probability distribution models for weights in cargo holds, water ballast tanks, fuel tanks as well as consumable tanks are proposed best fitting the collected data; hull girder still water loads statistical distributions are also obtained. It is expected that these analytical models can be used in structural reliability analyses that require the definition of uncertainties of loading conditions and of resulting still water loads.

Vibrational characterization of a human femur bone and its significance in the designing of artificial implants

PurposeBeing an interdisciplinary research area, biomechanics has gained interest among researchers. Biomechanics deals with integration of mechanical phenomenon with the structural and functional aspects of biological systems. Biological systems being very much complex provide a very intricate platform for their analysis. In case of damages created by accidents or sport malfunctions, artificial implants are used for the replacement of bones. These implants may cause incompatibility with the human body, depending on their design and characterization. So, this research aims to analyze the vibrational characteristics of a human femur bone and to predict the safe ranges of frequencies of operation.Design/methodology/approachThe current research is aimed at vibrational characterization of a human femur bone. The model of the femur bone is prepared using SOLIDWORKS software. The material properties of the femur are collected from the available literature and provided with the CAD model. The model is imported to the ANSYS software. Loading patterns as applied on the human body are also applied to the prepared model. Suitable boundary conditions are chosen for normal sitting and standing positions. The natural frequencies of the femur bone and other vibrational parameters are found out.FindingsThe first data obtained from the ANSYS software are the natural frequencies and mode shapes of vibration. Other data include the stress distributions, strain distributions, deformation patterns and potential zones of damage. The frequencies and mode shapes enable the safe ranges of human operation and the frequency range to be followed in the designing of implants. The stress distributions enable to know the potential zones of damage so that those areas can be given focus during strength considerations.Research limitations/implicationsThe current investigations take into account only normal sitting and walking conditions. This work can be included under static loadings. This can also be extended toward dynamic loading conditions. In the dynamic loading, walking and running conditions can be taken into account. This work focuses on the safe designing of the artificial implants and their compatibility with the human body. This can also be extended toward role of dynamic forces in the damaged bone formation and the role of implant’s characteristics for healing of bones.Practical implicationsBone damage and ligament fracture are common nowadays due to increasing number of accidents, which may be vehicular or sports. In case of any damage to the skeletal parts, some artificial implant is used to support the damaged part and to help in the process of healing. The designing of the implants must be compatible with the human body. The natural frequencies and mode shapes give an idea that the vibrational parameters of the implant material must fall in the same range as the actual bone. The stress distribution and potential zone damage emphasize on strength considerations.Originality/valueThe current method is a novel approach toward implant designing. Here an analysis of vibrational parameters of the human femur bone is performed. Those parameters include natural frequencies, mode shapes, principal normal stress distributions, principal shear stress distributions, maximum shear elastic strains and total deformation. These parameters reflect an idea about behavior of the femur bone under actual loading conditions. This analysis enables an implant designer to focus on material properties and strength considerations of the implants which are to be used in case of bone damage.

Fracture Response of Girth-Welded Pipeline With Canoe Shape Embedded Crack Subjected to Large Plastic Deformation

Long-distance offshore pipelines always suffer large plastic deformation during installation and operation. Accompanied by high internal pressure, potential flaws are found to initiate from the girth welds, and this brings a significant challenge to the structural integrity of the pipelines. The currently used procedures for fracture assessment of pipelines are usually stress based, which are unsuitable for application to cracked pipeline subjected to large plastic deformation. Therefore, the aim of this paper is to investigate the fracture assessment of pipeline subjected to large plastic deformation and identify and understand the critical parameters influencing the fracture responses under actual loading conditions. The evolution of crack tip opening displacement (CTOD) of a pipeline segment with an embedded canoe shape crack located in the middle of the girth weld is investigated under pure bending and biaxial loading through 3D elastic–plastic finite-element simulations. The effects of crack width, crack length, pipeline thickness, material hardening, and internal pressure on fracture response are discussed. Finally, a strain-based failure assessment diagram (FAD) is developed, and comparison between fracture assessment by BS7910:2013 and finite-element simulations concludes that the former produces conservative predictions for deep crack.

Effects of loading modes on reliability of cracked structures using FORM and MCS

Studying the reliability of cracked structures under different types of failure modes such as a mixture of Mode I and Mode II loadings has been of great importance in many applications. The purpose of this study is to evaluate the effects of different modes of loading, i.e. pure Mode I, pure Mode II and Mixed mode I/II loadings on the reliability of cracked structures via three typical case studies including 1st: through crack in a very wide plate, 2nd: cracked pressurized fuselage and 3rd: cracked fastener holes under actual geometries and loading conditions using the FORM, the fracture toughness and the equivalent SIF for Mixed mode I/II loading which is extracted by the Energy release rate model 1. The MCS was used to check the accuracy of the FORM. It was found that the failure probability decreases significantly as the loading mode changes from the pure Mode I to pure Mode II. This means that the reliability in the Mixed mode I/II loading is higher than that of pure Mode I and smaller than for pure Mode II. Also, it was concluded that the failure probability decreases with increasing of the angle of crack for the Mixed mode I/II loading conditions. The results indicated that the angle of crack and the applied stress are the two variables which have the most significant influence on the reliability.

Combined effect of cup abduction and anteversion angles on long-term wear evolution of PCD-on-PCD hip bearing couple

This paper presents a three-dimensional (3D) finite element (FE) modelling for the estimation of wear evolution on the acetabulum cup against the femoral head for the combinations of different abduction angle (35°, 45° and 55°) and anteversion angle (0°, 10°, 20°, 30° and 40°) for PCD-on-PCD hip bearing components. By implementing the actual physiological hip gait loading conditions and the rotational movement of a normal walking cycle in the FE model, the contact pressure and the sliding distance were calculated to predict the wear. The cup surface was updated in a suitable interval of gait cycles for the estimation of wear. Wear was simulated for 20 years implant's life in a human body. Simulation results showed that higher abduction angle and lower anteversion angle result in the least linear and volumetric wear as compared to other conditions considered.

Combined effect of cup abduction and anteversion angles on long-term wear evolution of PCD-on-PCD hip bearing couple

This paper presents a three-dimensional (3D) finite element (FE) modelling for the estimation of wear evolution on the acetabulum cup against the femoral head for the combinations of different abduction angle (35°, 45° and 55°) and anteversion angle (0°, 10°, 20°, 30° and 40°) for PCD-on-PCD hip bearing components. By implementing the actual physiological hip gait loading conditions and the rotational movement of a normal walking cycle in the FE model, the contact pressure and the sliding distance were calculated to predict the wear. The cup surface was updated in a suitable interval of gait cycles for the estimation of wear. Wear was simulated for 20 years implant's life in a human body. Simulation results showed that higher abduction angle and lower anteversion angle result in the least linear and volumetric wear as compared to other conditions considered.

Online residual useful life prediction of large-size slewing bearings—A data fusion method

To decrease breakdown time and improve machine operation reliability, accurate residual useful life (RUL) prediction has been playing a critical role in condition based monitoring. A data fusion method was proposed to achieve online RUL prediction of slewing bearings, which consisted of a reliability based RUL prediction model and a data driven failure rate (FR) estimation model. Firstly, an RUL prediction model was developed based on modified Weibull distribution to build the relationship between RUL and FR. Secondly, principal component analysis (PCA) was introduced to process multi-dimensional life-cycle vibration signals, and continuous squared prediction error (CSPE) and its time-domain features were employed as equipment performance degradation features. Afterwards, an FR estimation model was established on basis of the degradation features and relevant FRs using simplified fuzzy adaptive resonance theory map (SFAM) neural network. Consequently, real-time FR of equipment can be obtained through FR estimation model, and then accurate RUL can be calculated through the RUL prediction model. Results of a slewing bearing life test show that CSPE is an effective indicator of performance degradation process of slewing bearings, and that by combining actual load condition and real-time monitored data, the calculation time is reduced by 87.3% and the accuracy is increased by 0.11%, which provides a potential for online RUL prediction of slewing bearings and other various machineries.

Numerical and Experimental Analysis of Aircraft Wing Subjected to Fatigue Loading

This study deals with the aircraft wing analysis (numerical and experimental) which subjected to fatigue loading in order to analyze the aircraft wing numerically by using ANSYS 15.0 software and experimentally by using loading programs which effect on fatigue test specimens at laboratory to estimate life of used metal (aluminum alloy 7075-T651) the wing metal and compare between numerical and experimental work, as well as to formulate an experimental mathematical model which may find safe estimate for metals and most common alloys that are used to build aircraft wing at certain conditions. In experimental work, a (34) specimen of (aluminum alloy 7075-T651) were tested using alternating bending fatigue machine rig. The test results are ; (18) Specimen to establish the (S-N) curve and endurance limit and the other specimens used for variable amplitude tests were represented by loading programs which represents actual flight conditions. Also it has been obtained the safe fatigue curves which are described by mathematical formulas. ANSYS results show convergence with experimental results about cumulative fatigue damage (D), a mathematical model is proposed to estimate the life; this model gives good results in case of actual loading programs. Also, Miner and Marsh rules are applied to the specimens and compared with the proposal mathematical model in order to estimate the life of the wing material under actual flight loading conditions, comparing results show that it is possible to depend on present mathematical model than Miner and Marsh theories because the proposal mathematical model shows safe and good results compared with experimental work results.
 

Experimental Setup and Methodology to Carryout Fatigue Testing of Spiral Bevel Gears Used in Differential Gear Box Using NVH Approach

Currently the fatigue testing of bevel gears are being done by using non rotating type of fixtures that applies fatigue load on a single tooth, which does not resemble the actual loading condition in an automotive differential gear box. This paper discusses the experimental setup with the noise and vibration analysis approach to determine the signature of failures of spiral bevel gears. The proposed experimental setup seems promising for further research and development in the fatigue testing of spiral bevel gears. The Crown pinion and wheel assembly is used for the testing. The pinion is connected to the electric 3 phase AC motor of 75HP with a suitable coupling and the crown wheel is mounted on the half axle shaft, which in turn is connected to an electric dynamometer. The speed/torque of electric motor and the load applied by the dynamometer can be varied. The acoustic sensor is mounted near the differential gear box and the accelerometers are mounted on the Pinion bearing, Crown wheel bearing and the half axle bearing. A four channel data acquisition system is used to log data in time domain (raw data) by three accelerometers and an acoustic sensor. The variations of sound pressure(dB) v/s time, sound Pressure(FFT-(RMS)) amplitude v/s Frequency, Acceleration v/s Time, Octave analysis i.e., Band power v/s Frequency, Noise spectrum Power v/s Frequency, Histogram, Power density v/s Time can be obtained. These data are then used to plot vibration and SPP levels in frequency domain to develop the noise and vibration signature of that crown pinion for given cycles of operation. The tests on Bevel pinion and gear set were performed in the BEC, Bagalkot NVH lab facility. The gear set run successfully at double the rated torque for 30 million pinion cycles. And the signature of pinion failure was obtained. The results demonstrated the suitability of using the given bevel crown pinion and gears set for specified speed, high load application in differential gear box of an automobile.

Real-Time Adaption of Dead Time for Single-Phase Autoreclosing

An approach for a real-time adaption of the dead time for autoreclosing on high-voltage lines was proposed. The objective was the optimal adaption of the dead time of a currently running single-phase autoreclosing cycle by calculating the secondary arc current based on measurements. The algorithms for optimization were performed for real-time applications. For this purpose, the fault location plus the load currents of the parallel nonfaulty conductors were measured. The measurement and the calculation of the dead time took place during the fault and the dead-time period. In this way, an optimized dead-time setting with regard to the actual fault location and loading conditions were achieved. This approach results in an online determination of the minimum necessary dead time of a successful reclosing under consideration of the fault location and prevailing loading conditions. Analytical calculations and numerical examples as well as high-voltage field tests verified the results.

Investigation of push-out delamination using cohesive zone modelling and acoustic emission technique

Push-out delamination is a serious concern in the drilling of fibre-reinforced composite materials. This damage occurs as the drill reaches the exit side of the material and can reduce the strength and stiffness of the structure. In this paper, a three-point bending test is performed on glass/epoxy-laminated composites to simulate the push-out delamination induced by thrust force during drilling. Cohesive zone modelling and acoustic emission monitoring are utilized to investigate the push-out delamination. Initially, double cantilever beam and end-notched flexure tests were performed to calibrate the cohesive zone modelling model. Following that, the actual loading condition is simulated using cohesive zone modelling-based finite element modelling. Energy of the acoustic emission signals is also used to detect the initiation of the delamination. The results obtained from cohesive zone modelling and acoustic emission showed that the applied methods can be used to understand and predict the initiation of push-out delamination and its progression. Finally, it is concluded that the proposed cohesive zone modelling and acoustic emission techniques can be used in the design stage as well as during the drilling process of laminated composite structures to avoid delamination.

Experimental Tests on Composite Steel-Concrete Truss Beams

This paper reports the results of an experimental campaign conducted on a set of eight composite beams made of prefabricated steel trusses encased in structural concrete. The test setup is organized in such a way to apply an evenly distributed load on the beam, so to simulate the actual loading condition in real buildings. This is also to avoid the formation of peculiar and unusual shear resisting mechanisms occurring in three or four-point bending tests. The experimental results are presented in terms of force-displacement graphs and also in terms of stress-strain diagrams in the steel members. The outcome of this study highlights that Composite Truss Beams (CTBs) have an effective performance in the shear resisting mechanism, showing a capacity higher than that estimated through the current capacity equations given by Codes.

Development of a Program-Loading Spectrum for the Accelerated Durability Test of Lower Control Arm

Abstract This study aims to develop a program-loading spectrum for the accelerated durability test of automotive components, with the lower control arm of a suspension as an example. Spectrum development is divided into three parts, namely, load spectrum acquisition, spectrum preprocessing, and program-loading spectrum development. Based on the strengthening property of structural low-amplitude loads under constant and random loadings, a program-loading spectrum-development method considering the strengthening effect of low-amplitude loads (SLAL) below the fatigue limit is proposed. Meanwhile, an equivalent strengthening methodology is considered during spectrum development. The number of loading cycles is decreased, and the bench test time is notably reduced by adjusting strengthening loads to the most effective level. The bench test proved that the influence of SLAL during spectrum development can simulate actual load conditions more effectively and precisely. Thus, this method can accurately predict fatigue failure from the durability test and can efficiently reduce durability test time.

Modulus Parameter Analysis and Calculation of Steel Deck Asphalt Pavement Material <sup></sup>

The numerical analysis model and analytic formula, concerning flexural-tensile composite modulus of steel deck paving materials, were established with five-point loading composite beams, in order to explore the modulus value of steel deck paving materials. Regarding the three typical asphalt pavement material such as SMA10, GA10 and EA10, the composite modulus of paving material was calculated by analyzing stepwise loading data, and a universal flexural-tensile composite modulus range is proposed: SMA10 is 500 ~ 550MPa, GA10 is 500 ~ 600MPa, EA10 is 650 ~ 700MPa. The results show good agreement between the modulus of the numerical analysis method and analytical formula method. The proposed analytical formulas can calculate the flexural-tensile composite modulus more easily according to the actual load conditions, and the modulus value played a significant role in guiding the design and mechanical analysis of steel deck pavement system.

연속 주름구조를 가진 전열판의 기계적 건전성 확보를 위한 형상 설계 및 제작

A thin sheet of metal with corrugated structures has been utilized in various devices: heat exchangers, separators in fuel cells, and many others. However, it is not easy to fabricate thin corrugated structures using a single-step stamping process due to their geometrical complexity. To solve this problem, firstly, a plate type heat exchanger was redesigned to attain the optimal value of aspect ratio and the optimal shape of corrugated structures for the actual loading conditions. A forming analysis of the corrugated plate was then carried out to determine the process parameters. From this work, the optimal value of aspect ratio was found to be 4.6. In addition, the process parameters of heat exchanger forming were optimized using the optimal value of aspect ratio, and the analytical results were evaluated through experiments. The results obtained indicated good agreements between them.

Effect of air plasma treatment on mechanical properties of bioactive composites for medical application: Composite preparation and characterization

The aim of this study was to fabricate unidirectional bio-glass fibers (BGF) (13-93)-reinforced polylactic acid (PLA) composites with improved mechanical properties for a bone plate to heal the weight-bearing long-bone fractures. Various exposure times of air plasma (30, 60, 90 and 120s) on BGF fibers were studied, and the most suitable conditions were determined for the fabrication of the BGF/PLA composite. Mechanical properties, microscopic characteristics, in vitro degradation and the bioactivity of the BGF/PLA composites were evaluated. Fatigue life of 30s plasma treated composites completed 1 million cycles when actual loading conditions (10–20% body weight) were used. 30s plasma treated specimens showed increase in tensile strength, flexural strength and interlaminar shear strength as 31%, 13.5% and 33%, respectively. The SEM image of fractured surface of 30s plasma treated composite suggested that the failure was shifted to the PLA which is evidence of superior bonding between fiber and PLA matrix. Moreover, a bone-like calcium-phosphate layer was precipitated on the surface of degraded composite that is essential for bone healing.

Alteration of Stress Distribution Patterns in Symptomatic Valgus Instability of the Elbow in Baseball Players

Background: Repetitive valgus stress applied during a throwing motion can lead to various elbow disturbances, including ulnar collateral ligament (UCL) injury. Subchondral bone density reportedly reflects the cumulative force on a joint surface under actual loading conditions. Purpose: (1) To evaluate the distribution of subchondral bone density across the elbow joint in asymptomatic baseball pitchers and symptomatic valgus instability pitchers and (2) to clarify the alterations in stress distribution pattern associated with symptomatic UCL insufficiency pitching activities. Study Design: Controlled laboratory study. Methods: Computed tomography (CT) imaging data were collected from the dominant-side elbow of 7 nonathletic volunteers (controls), 12 asymptomatic pitchers (asymptomatic group), and 12 symptomatic valgus instability pitchers with UCL insufficiency (symptomatic group). Bone mineral density across the elbow joint was measured with CT osteoabsorptiometry. A 2-dimensional mapping model was divided into 4 areas of the distal end of the humerus and 5 areas of the ulna with the radial head. The locations and percentages of high-density areas on the articular surface were quantitatively analyzed. Results: High-density areas in the asymptomatic and symptomatic groups were found in the anterolateral and posteromedial parts of the humerus and in the radial head, posteromedial to the ulna. The high-density areas in the anterior and posteromedial of the humerus, the radial head, and the posteromedial part of the ulna in the controls were smaller than those in the baseball group. In the symptomatic group, the percentages of high-density areas in the anterolateral part of the humerus (mean, 36.3%; 95% CI, 31.9%-40.7%) and the anterolateral part of the ulna (mean, 31.7%; 95% CI, 24.3%-39.1) were significantly greater than those in the asymptomatic group (P = .047 and P < .0001, respectively). Conclusion: Symptomatic UCL insufficiency was associated with characteristic high-stress distribution patterns on the anterolateral part of the capitellum and the anterolateral part of the ulna. The current results indicate that symptomatic UCL insufficiency produces excessive and cumulative stress in the elbow joint. Clinical Relevance: The information obtained from the CT images can useful for early detection of overstress conditions of the elbow joint.

Evaluation of Structural Behavior of Precast Prestressed Concrete Pavement with Finite Element Analysis

A full-scale precast prestressed concrete pavement (PPCP) system was constructed and evaluated under actual traffic load conditions to develop the design guideline under Florida conditions. This test section showed good load transfer efficiency and riding quality. However, information was lacking about its structural response and potential performance. A three-dimensional finite element model was developed for stress analysis of PPCP under critical loading conditions. The developed three-dimensional model was calibrated by using deflection data obtained with a falling weight deflectometer. The model was used to perform a parametric analysis to determine the effects of critical loading location, concrete modulus, coefficient of thermal expansion of concrete, loss of prestress force, and subgrade stiffness under typical Florida conditions. Results of the parametric study indicate that the maximum stresses in the concrete increased significantly as the concrete modulus and coefficient thermal expansion increased. Because of the increase in flexural strength associated with the increase in elastic modulus of the concrete, an increase in elastic modulus of the concrete results in a decrease in the computed stress-to-strength ratio under critical load–temperature conditions. The PPCP system that was evaluated appeared to have a good predicted pavement performance with a computed stress-to-strength ratio of less than 0.5, with up to an additional loss of 20% of prestress force in the longitudinal and transverse directions. Variations in the base and subbase properties were found to have a minimal effect on the maximum induced stresses in concrete. This finding indicates that the PPCP system is appropriate for a wide variety of subbase and subgrade conditions.