Three-dimensional Plate Research Articles

Experimental, analytical and numerical, investigation of peak temperature and cooling rate in butt joint weld of mild steel

PurposeThis paper aims to measure peak temperatures and cooling rates for distinct locations of thermocouples in the butt weld joint of mild steel plates. For experimental measurement of peak temperatures, K-type thermocouples coupled with a data acquisition system were used at predetermined locations. Thereafter, Rosenthal’s analytical models for thin two-dimensional (2D) and thick three-dimensional (3D) plates were adopted to predict peak temperatures for different thermocouple positions. A finite element model (FEM) based on an advanced prescribed temperature approach was adopted to predict time-temperature history for predetermined locations of thermocouples.Design/methodology/approachComparing experimental and Rosenthal analytical models (2D and 3D) findings show that predicted and measured peak temperatures are in close agreement, while cooling rates predicted by analytical models (2D, 3D) show significant variation from measured values. On the other hand, 3D FEM simulation predicted peak temperatures and cooling rates for different thermocouple positions are close to experimental findings.FindingsThe inclusion of filler metal during simulation of welding rightly replicates the real welding situation and improves outcomes of the analysis.Originality/valueThe present study is an original contribution to the field of welding technology.

The Effect of Rectus Abdominis Fatigue on Lower Limb Jumping Performance and Landing Load for Volleyball Players

The aim of this study was to investigate the effects of rectus abdominis (RA) fatigue on the jumping performance and landing loads of volleyball players during countermovement jumps (CMJs) and spike jumps (SPJs). Twelve healthy university volleyball players were evaluated using a three-dimensional motion analysis system, force plates, and surface electromyography (EMG). The lowest center of mass (Min-CoM), maximum jumping height (Max-JH), angles of joints at take-off and landing, joint moment of the lower limbs, and EMG parameters of the RA, erector spinae, and lower limb muscles, when performing the CMJs and SPJs, were recorded before and after a 10 min RA muscle fatigue intervention. After RA fatigue, the Max-JH was significantly reduced, and the lowest Min-CoM was significantly increased. The take-off angles changed significantly at the ankle (SPJ), knee (CMJ), and hip (SPJ), and the plantar flexion torque changed significantly at the SPJ touchdown. The contribution ratio of the feet during SPJs and CMJs changed after fatigue. Temporary RA fatigue decreases the jump height of athletes and causes a change in the landing strategy.

Advancement in measuring the hydraulic conductivity of porous asphalt pavements

The measurement of the in situ hydraulic conductivity of porous asphalt pavements, K, is a matter of practical interest; however, there are cases where current techniques are difficult to use. Several methods are documented in literature, mainly based on permeameters with water as fluid. Using water has its advantages, as it is straightforwardly related to the drainage problem during rain storms, but it also involves some major issues, especially on field studies. For instance, the time necessary to reach the steady state is too long and the necessary amount of water could not be available. In addition, non-repeatability and hysteresis phenomena can occur, also due to air bubbles confined in the porous matrix. In the present paper, we describe a novel test method for measuring K using air at low pressure as fluid. The proposed permeameter was first tested in the laboratory, in order to (i) validate the theoretical relationships between KH2O and Kair, and (ii) define a model to evaluate an equivalent length scale for asphalt pavements, Leq, as a function of the thickness of the porous layer (this is useful when one-dimensional formulations are adopted in the case of three-dimensional plates or in situ measurements). Finally, the protocol and methodology were validated on two sites in Italy (Monza, Milan, and Poviglio, Reggio Emilia) where Kair was measured by the air field permeameter, and compared with KH2O, measured by a standard falling head permeameter. The technique allows the determination of the hydraulic conductivity on the basis of the ratio between pressure difference and flow rate, and of Leq.

Tensile properties and failure mechanism of 3D woven composites containing holes of different geometries

The open-hole tension (OHT) properties and failure processes of three-dimensional (3D) woven composite plates with circular, racetrack, and square holes were investigated in this study through experiments and finite element (FE) modeling. Tensile tests were performed on unnotched and notched specimens and measured via digital image correlation (DIC) to record the full-field strain fields, while micro-computed tomography (micro-CT) was employed to obtain the fracture morphologies. To predict the OHT performance, stress concentration factor (SCF), and damage propagation processes of the notched specimens, progressive damage analysis based on the FE model of a macro-meso coupling model was implemented on three open-hole plates. It was found that the OHT strength of 3D woven composites was reduced by approximately 35% compared with that of the unnotched specimen, whereas the modulus remained almost unchanged. The hole shape significantly influenced the strain distributions but had no perceptible effect on the OHT strength. The SCF of the specimen with a circular hole was 36% higher than those cases of the racetrack and square holes. Moreover, the hole-edge stress concentrations were mainly distributed on the warp yarns and became a cause for early failure. The major failure modes near the hole edge were warp breakage and pull-out.

Three-Dimensional Osteosynthesis Plates for the Surgical Treatment of Mandibular Fractures.

Mandible fractures can be treated with different plate systems, that is, miniplates or three-dimensional (3D) plates. This systematic review describes the effectiveness and clinical outcomes of 3D plates used in fractures of the mandible and aims to critically evaluate its risks and benefits. A comprehensive electronic search was conducted without date but with restriction to articles written in English. Studies in humans, including randomized or quasi-randomized controlled trials and retrospective studies, were included. The outcome parameters measured were number of patients, fracture classification, results, follow-up period, postoperative complications, and mean age of patients. Major complications were defined as those needing additional surgical intervention, for example, malocclusion, infection or plate fracture. Accordingly, complications not needing additional surgical intervention were defined as minor (ie, dehiscence, trismus). Guided by the PRISMA statement and the Cochrane Handbook for Systematic Reviews of Interventions, the authors identified 44 publications with a total of 1790 patients. Among the articles selected for the final review, there were 32 reported prospective studies, 12 reported retrospective studies. Regarding the evaluation of quality, 8 studies showed a low value of the risk of bias, 17 a moderate risk, and 19 a high risk. There were statistically significant advantages for 3D plates in mandibular fractures in terms of postoperative complications, for example, wound dehiscences or plate fracture. The 3D plate is an effective treatment modality for mandibular fractures, with low incidence of major complications, decreased length of operation time, and increased stability of osteosynthesis.

Physical–numerical parameters in turbulent simulations of natural convection on three-dimensional square plates

PurposeThis paper aims to study, experimentally validate and select the main physical and numerical parameters of influence in computational numerical simulations to evaluate mean heat flux by natural convection on square flat plates.Design/methodology/approachSeveral numerical models were built to study the influence of physical and numerical parameters about the predictions of the natural convection heat transfer rates on the surface of a flat plate with aspect ratio = 1, in isothermal conditions, turbulent regime and using the free and open-source software OpenFOAM®. The studied parameters were: boundary conditions (using or not using wall functions in properties ε, κ, νt and ω), degree of mesh refinement, refinement layers and turbulence models [κ – ε and κ – ω Shear Stress Transport (SST)]. From the comparison of the values of the mean Nusselt number, obtained from numerical simulations and literature experimental results, the authors evaluated the precision of the studied parameters, validating and selecting the most appropriate to the analyzed problem situation.FindingsThe validation and agreement of the numerical results could be proven with excellent precision from experimental references of the technical scientific literature. More refined meshes with refinement layers were not suitable for the studies developed. The κ – ε and κ – ω SST turbulence models, in meshes without refinement layers, proved to be equivalent. Whether or not to use wall functions in turbulent boundary conditions proved to be irrelevant as to the accuracy of results for the problem situation studied.Practical implicationsUse of the physical and numerical parameters is studied and validated for various applications in natural convection heat transfer of technology and industry areas.Social implicationsUse of free and open-source software as a research tool in the Computational Fluid Dynamics (CFD) area, especially in conditions without large financial resources or state-of-the-art infrastructure.Originality/valueTo the best of the authors’ knowledge, this work is yet not available in existing literature.

Direct Generation of Airy Beams at Designed Fourier Planes Using Integrated Airy Phase Plates

Featuring extraordinarily curved propagation trajectories, self-accelerating Airy beams have stimulated considerable interests from academic research to practical applications. However, generation of high-quality Airy beams using compact optical devices is still highly desirable. Here we present a design of integrated Airy phase plates (IAPPs) with a miniature size (60 μm × 60 μm × 1.1 μm). In addition, a phase-type Fresnel zone plate (FZP) is incorporated in the phase element to further reduce the system dimension, endowing the IAPPs the ability of directly generating Airy beams without introducing a bulky Fourier transform (FT) lens. The fabrication of IAPPs is facilitated by femtosecond direct laser writing (FsDLW), and the experimentally generated Airy beams are in good agreement with the numerical simulations. Furthermore, the flexible fabrication of IAPPs with different focal lengths is demonstrated, which results in the generation of Airy beams at different Fourier planes as desired. Our design strategy and fabrication methodology of the microscale three-dimensional (3D) phase plates can unfold new capacities of Airy beams for miniaturization applications in fiber optics and in on-chip photonics.

Evaluation of 3D Trapezoidal Plates in Open Reduction and Internal Fixation of Subcondylar Fractures of Mandible: A Clinical Trial.

Background Fractures of the mandibular condyle are common and account for 25% to 50% of all fractures of the mandible. Various methods exist for open reduction and internal fixation (ORIF) of condylar fractures. This study was done to explore three-dimensional (3D) plates as a viable option.Aim This study aims to evaluate the effectiveness of 3D trapezoidal plates in open reduction and internal fixation of subcondylar fractures.Materials and methodologyThis was a non-randomized clinical trial conducted on 20 patients who reported at the Department of Oral and Maxillofacial Surgery, Tamil Nadu Government Dental College and Hospital, Chennai, India. The ORIF was done under general anesthesia. A retromandibular transmasseteric approach was used to expose the fracture site, and the fracture was stabilized using 3D titanium trapezoidal plates. Parameters, such as mouth opening, mandibular deviation, occlusion, surgical accessibility, fracture reduction, adaptability, the difference in ramal height, angulation of the fractured condyle, operative time, facial nerve weakness, implant failure, complications, and scar formation were assessed. Statistical analysis was done using Statistical Package for Social Sciences (SPSS), version 21 (IBM SPSS Statistics for Windows, Armonk, NY).Results There was an improvement in mouth opening and occlusion in the immediate postoperative period. The surgical accessibility ranged from good to excellent. The fracture reduction was excellent in 60% of patients and good in 40%. In one patient, there was a transient weakness of the marginal mandibular nerve which recovered by three months. Another patient had a wound infection that subsided within the first postoperative week. None of the patients had a device failure during the six-month follow-up period.Conclusion The trapezoidal 3D plates could be considered as a viable option for treating subcondylar fractures of the mandible in terms of surgical accessibility, stability, ease of device placement, stability of reduced fracture, reduced osteosynthesis material requirement, and minimal damage to the surrounding tissues.

Developing a three-dimensional tangential swirl plate photobioreactor to enhance mass transfer and flashlight effect for microalgal CO2 fixation

A novel three-dimensional tangential swirl plate (TTSP) photobioreactor was proposed to strengthen flow perpendicular to central cross-section between two side walls, resulting in more widespread turbulence for improving microalgal CO2 fixation. The axes of four center-symmetrically arranged nozzles were tangential to a horizontal cylinder to form two staggered vortexes. When angle θ between nozzle axis and central cross-section increased from 0° to 22.1° and then to 40.0°, mixing time and average bubble diameter first decreased to the minimum (16.55 s and 0.57 mm) and then increased. When relative diameter of tangential cylinder d/D increased from 0.11 to 0.34 and then to 0.56, flashlight frequency and light time ratio first increased to the maximum (0.21 Hz and 42.8%) and then decreased. Accordingly, flashlight frequency was 90.9% higher in TTSP photobioreactor than that in two-dimensional jet-aerated tangential swirl plate (JTSP) photobioreactor, leading to an increase in microalgal CO2 fixation rate by 30%.

Solution-Based One-Step Preparation of Three-Dimensional Self-Assembled Octadecyl Silica Nanosquare Plate and Microlamella Structures for Superhydrophobic and Icephobic Surfaces.

Icephobic surfaces have gained immense attention owing to their significant roles in decreasing the energy consumption of refrigerators and in improving safety issues by preventing the formation of ice on them. Superhydrophobic surfaces incorporating micro- or nanoscale roughness and hydrophobic functional groups have been shown to prevent ice accumulation. Herein, we report a simple, low-cost, and solution-based one-step process for the production of superhydrophobic surfaces with three-dimensional (3D) self-assembled structures. The controlled hydrolysis and polycondensation of n-octadecyltrichlorosilane (OTS-Cl) in an acetone solution produced a highly uniform superhydrophobic surface on various substrates such as glass, metals, and polymers without the limitation of the surface curvature structure. The as-prepared 3D self-assembled surface exhibited a very high contact angle of 161.7° and a low contact hysteresis of 1.47°. The solvent type, H2O content in acetone, and carbon chain length of the silane compound were critical in the formation of self-assembled nanostructures. The thickness of the superhydrophobic 3D self-assembled structure could be varied by controlling the surface properties of the glass substrate. In addition, a novel octadecyl silica nanosquare plate structure was formed as an intermediate for the microlamella structure. The water drop impact experiments on the 3D self-assembled superhydrophobic glass substrates at low temperatures (T < -25 °C) showed that the as-prepared superhydrophobic glass possessed a high impalement threshold for water contact, resulting in excellent and stable icephobic properties. The preparation method proposed in this study is scalable and can be used on a flat glass surface or in a glass vial inside a glass tube. Moreover, it can be applied to various substrates such as metals and polyurethane surfaces with curvature. Therefore, the solution-based self-assembly method proposed in this study is a promising approach to produce superhydrophobic and icephobic surfaces on a wide range of substrates regardless of their structure and properties.

A high-fidelity numerical study on the propulsive performance of pitching flexible plates

In this paper, we numerically investigate the propulsive performance of three-dimensional pitching flexible plates with varying flexibility and trailing edge shapes. We employ our recently developed body-conforming fluid-structure interaction solver for our high-fidelity numerical study. To eliminate the effect of other geometric parameters, only the trailing edge angle is varied from 45° (concave plate), 90° (rectangular plate) to 135° (convex plate) while maintaining the constant area of the flexible plate. For a wide range of flexibility, three distinctive flapping motion regimes are classified based on the variation of the flapping dynamics: (i) low bending stiffness KBlow, (ii) moderate bending stiffness KBmoderate near resonance, and (iii) high bending stiffness KBhigh. We examine the impact of the frequency ratio f* defined as the ratio of the natural frequency of the flexible plate to the actuated pitching frequency. Through our numerical simulations, we find that the global maximum mean thrust occurs near f*≈1 corresponding to the resonance condition. However, the optimal propulsive efficiency is achieved around f* = 1.54 instead of the resonance condition. While the convex plate with low and high bending stiffness values shows the best performance, the rectangular plate with moderate KBmoderate is the most efficient propulsion configuration. To examine the flow features and the correlated structural motions, we employ the sparsity-promoting dynamic mode decomposition. We find that the passive deformation induced by the flexibility effect can help in redistributing the pressure gradient, thus, improving the efficiency and the thrust production. A momentum-based thrust evaluation approach is adopted to link the temporal and spatial evolution of the vortical structures with the time-dependent thrust. When the vortices detach from the trailing edge, the instantaneous thrust shows the largest values due to the strong momentum change and convection process. Moderate flexibility and convex shape help to transfer momentum to the fluid, thereby improving the thrust generation and promoting the transition from drag to thrust. The increase in the trailing edge angle can broaden the range of flexibility that produces positive mean thrust. The role of added mass effect on the thrust generation is quantified for different pitching plates and the bending stiffness. These findings are of great significance to the optimal design of propulsion systems with flexible wings.

Stability of a three-dimensional plate made of a nonlinear viscoelastic material under superimposed finite deformations

In this paper, the stability of a three-dimensional plate made of a nonlinear viscoelastic material under finite perturbations is considered. A fairly broad computational experiment has been performed. The permissible boundaries of the region with respect to the final, initial perturbations are established for the given parameters of loading and structures. Finite sequences of bifurcation points are constructed, which confirm, in contrast to stability under small perturbations, the existence of a sequence of stable equilibrium states. New phenomena and characteristic effects are established.

Effects of Different Assistive Seats on Ability of Elderly in Sit-To-Stand and Back-To-Sit Movements.

The ability to perform sit-to-stand (STS) and back-to-sit (BTS) movements is important for the elderly to live independently and maintain a reasonable quality of life. Accordingly, this study investigated the STS and BTS motions of 28 healthy older adults (16 male and 12 female) under three different seat conditions, namely nonassisted, self-designed lifting seat, and UpLift seat. The biomechanical data were acquired using a three-dimensional (3D) motion analysis system and force plates, and were examined by one-way repeated-measures ANOVA to investigate the effects of the different seat conditions on the joint angle, joint moments, and movement duration time (α = 0.05). No significant difference was observed in the STS duration among the three test conditions. However, the BTS duration was significantly increased in the UpLift seat condition. Moreover, the peak flexion angle of the hip during STS motion was also significantly higher in the UpLift condition. For both motions (STS and BTS), the lifting seats significantly decreased the knee and hip joint moments, but significantly increased the ankle joint moment. Moreover, compared to the nonassistive seat, both assistive lifting seats required a greater ankle joint strength to complete the STS and BTS motions.

Lower extremity muscle contributions to ACL loading during a stop-jump task

Landing is considered a high-risk movement, especially landings from a stop-jump task, as they are often associated with lower extremity injuries, such as anterior cruciate ligament injuries (ACL). Females demonstrate lower extremity landing mechanics that often place them at a larger risk of injury compared to their male counterparts. While efforts have been made to understand lower extremity mechanics during stop-jump landings, little is known regarding the musculature function during these tasks and how they may influence ACL loading. Understanding lower extremity muscle contributions to ACL loading (FACL) may give insight to improving injury prevention protocols. Ten healthy, recreationally active females completed five trials of an unanticipated stop-jump task. Right leg kinematics, kinetics, and electromyography data were collected with three-dimensional motion capture, force plates, and electromyography sensors, respectively. Modified musculoskeletal models were scaled based on participant-specific anthropometrics, and muscle forces were obtained using static optimization. An induced acceleration analysis combined with a previously established mathematical ACL loading model was used to calculate lower extremity muscle contribution to FACL. The vastus lateralis, vastus intermedius, vastus medials, biceps femoris long head, semimembranosus, and soleus were found to be the primary contributors to FACL, with the vastus lateralis being the largest contributor. These data suggest that muscles traditionally known as ACL unloaders may in certain conditions load the ACL. These results also suggest that future injury prevention protocols should target muscles specifically to mitigate the influence the vastus lateralis has on ACL loading.

Topological Design of Freely Vibrating Bi-Material Structures to Achieve the Maximum Band Gap Centering at a Specified Frequency

AbstractThe topological design of structures to avoid vibration resonance for a certain external excitation frequency is often desired. This paper considers the topology optimization of freely vibrating bi-material structures with fixed/varying attached mass positions, targeting at maximizing the frequency band gap centering at a specified frequency. A band gap measure index is proposed to measure the size of the band gap with a specified center frequency. Aiming at maximizing this measure index, the topology optimization problem is formulated on the basis of the material-field series-expansion (MFSE) method, which greatly reduces the number of design variables and at the same time keeps the capability to describe relatively complex structural topologies with clear boundaries. As the considered optimization problem is highly non-linear and may yield multiple local minima, a sequential Kriging-based optimization solution strategy is employed to effectively solve the optimization problem. This solution strategy exhibits a relatively strong global search capability and requires no sensitivity information. With the present topology optimization model and the gradient-free algorithm, relative large band gaps with specified center frequencies have been obtained for two-dimensional (2D) beams and three-dimensional (3D) plates, without specifying the frequency orders between which the desired band gap occurs in prior.

The influence of bone quality on radiological outcome in 50 consecutive acetabular fractures treated with a pre-contoured anatomic suprapectineal plate

PurposeTo investigate the range of indications of an anatomical-preshaped three-dimensional suprapectineal plate and to assess the impact of the bone mass density on radiologic outcomes in different types of acetabular fractures.Patients and methodsA consecutive case series of 50 acetabular fractures (patient age 69 ± 23 years) treated with suprapectineal anatomic plates were analyzed in a retrospective study. The analysis included: Mechanism of injury, fracture pattern, surgical approach, need for additional total hip arthroplasty, intra- or postoperative complications, as well as bone mass density and radiological outcome on postoperative computed tomography.ResultsMost frequently, anterior column fracture patterns with and without hemitransverse components as well as associated two column fractures were encountered. The anterior intrapelvic approach (AIP) was used in 98% (49/50) of the cases as primary approach with additional utilization of the first window of the ilioinguinal approach in 13/50 cases (26%). Determination of bone density revealed impaired bone quality in 70% (31/44). Postoperative steps and gaps were significantly greater in this subgroup (p < 0.05). Fracture reduction quality for postoperative steps revealed anatomic results in 92% if the bone quality was normal and in 46% if impaired (p < 0.05). In seven cases (14%), the plate was utilized in combination with acute primary arthroplasty.ConclusionA preshaped suprapectineal plate provides good radiological outcomes in a variety of indications in a predominantly geriatric cohort. Impaired bone quality has a significantly higher risk of poor reduction results. In cases with extensive joint destruction, the combination with total hip arthroplasty was a valuable option.

Closed-form solutions for the free vibrations of three-dimensional orthotropic rectangular plates

In the vibration analysis of plates, the three-dimensional (3-D) elasticity theory provides more accurate modes and frequencies than all the two-dimensional (2-D) plate theories. In this work, the extended separation-of-variable method proposed by the present authors (Xing Y, Wang Z. An extended separation-of-variable method for the free vibration of orthotropic rectangular thin plates. Int J Mech Sci 2020;182:105739) is developed to solve the vibrating problem of orthotropic plates based on the 3-D elasticity theory. In this method, the mode functions are in an explicit separation-of-variable form, and the frequencies corresponding to eigenfunctions in three spatial directions are mathematically independent of each other. The closed-form analytical eigensolutions satisfy the Rayleigh's principle exactly. This method can deal with all homogeneous boundary conditions. For plates with at least two pairs of parallel surfaces simply supported, the eigensolutions satisfy the differential governing equation exactly as the well-known Levy types of exact solutions. Numerical experiments validate the accuracy of the present solutions. The effects of plate thickness, shear correctness factor and material properties on the accuracy of the 2-D plate theories are investigated.

Designing access for adrenalectomy using computer-tomographic 3D modeling

Introduction. In the literature, the insufficient attention is paid to preoperative planning of access to adrenal masses using modern computed tomographic navigation capabilities. The purpose. To demonstrate the possibilities of designing a safe access for adrenalectomy with the appliation of three-dimensional printed models based on the integral assessment of preoperative computed tomographic data.Materials and methods. The possibilities of preoperative design of access for adrenalectomy were studied in 362 patients with adrenal tumors, for whom computed tomography was performed on an Aquillion 64 (Toshiba, Japan).Results. Reliable anthropometric (BMI, body shape) and CT criteria for designing surgical access to the right and left NP were determined. Three patients with a borderline number of risk criteria for the development of vascular complications associated with technical difficulties of adrenalectomy (for the right AP, ≥4, for the left AP, ≥3) underwent CT-segmentation of images followed by the creation of three-dimensional plates — a model of the AP tumor with adjacent organs and vessels.Conclusion. Preoperative computed tomographic access design, taking into account the criteria of the risk of complications and the application of three-dimensional printed models, make it possible to reasonably use endoscopic and open adrenalectomy options, significantly improving the immediate results of patient treatment.

Characteristics of Eight Irish Dance LandingsConsiderations for Training and Overuse Injury Prevention.

Irish dance has evolved in aesthetics that lead to greater physical demands on dancers' bodies. Irish dancers must land from difficult moves without letting their knees bend or heels touch the ground, causing large forces to be absorbed by the body. The majority of injuries incurred by Irish dancers are due to overuse (79.6%). The purpose of this study was to determine loads on the body of female Irish dancers, including peak force, rise rate of force, and impulse, in eight common Irish hard shoe and soft shoe dance movements. It was hypothesized that these movements would produce different ground reac- tion force (GRF) characteristics. Sixteen female Irish dancers were recruited from the three highest competitive levels. Each performed a warm-up, reviewed the eight movements, and then performed each movement three times on a force plate, four in soft shoes and four in hard shoes. Ground reaction forces were measured using a three-dimensional force plate recording at 1,000 Hz. Peak force, rise rate, and vertical impulse were calculated. Peak forces normalized by each dancer's body weight for each of these variables were significantly different between move- ments and shoe types [F(15, 15)= 65.4, p < 0.01; F(15, 15) = 65.0, p < 0.01; and F(15, 15) = 67.4, p < 0.01, respectively]. The variable years of experience was not correlated with peak force, rise rate, or impulse (p > 0.40). It is concluded that there was a large range in GRF characteristics among the eight movements studied. Understanding the force of each dance step will allow instructors to develop training routines that help dancers adapt gradually to the high forces experienced in Irish dance training and competitions, thereby limiting the potential for overuse injuries.

Larger hip external rotation motion is associated with larger knee abduction and internal rotation motions during a drop vertical jump

ABSTRACT Associations among hip motions, knee abduction and internal rotation motion during a drop vertical jump (DVJ), which increases the risk of anterior cruciate ligament injury, remain unclear. The purpose of this study was to examine associations among knee abduction, internal rotation and hip joint motions during a DVJ. Fifty-seven young female participants performed a DVJ from a 30-cm height. Hip and knee kinematics and kinetics were analysed using a three-dimensional motion analysis system and force plates. Multiple regression analysis showed that peak knee abduction angle was negatively associated with knee internal rotation and hip internal rotation excursions from initial contact (IC) to peak knee flexion, and positively associated with peak knee abduction moment (R2 = 0.465, P< 0.001). Peak knee internal rotation angle was negatively associated with the hip flexion excursion from IC to peak knee flexion and peak hip adduction moment (R2 = 0.194, P= 0.001). In addition, hip internal rotation excursion was negatively associated with knee abduction and internal rotation excursion from IC to 50 ms after IC. To avoid a large knee abduction and internal rotation motion during jump-landing training, it might be beneficial to provide landing instructions to avoid a large hip external rotation motion.