Bar Design Research Articles

Correction: Structure design and vibration control of vibration reduction boring bar with variable damping

Correction: Structure design and vibration control of vibration reduction boring bar with variable damping

A Method for Dynamic Kolsky Bar Compression at High Temperatures: Application to Ti-6Al-4V

Abstract An experimental apparatus for measuring the dynamic behavior of materials subjected to strain rates on the order of 10 $$^3$$ 3 s $$^{-1}$$ - 1 and temperatures up to 800°C with a unique triple actuation system is developed in this work. This system is based on the traditional Kolsky (or split-Hopkinson pressure) bar design, with the addition of an external furnace used to heat the specimen to the desired temperature. A synchronized triple pneumatic actuation system is used to control the motion and timing of the the sample, incident, and transmitted bars. The cold contact time (CCT), or the time during which the heated sample is in contact with the room temperature bars before compression, is measured experimentally and carefully controlled to minimize the development of a temperature gradient across the sample and avoid heating of the bars. Experiments are performed in conjunction with ultra high speed imaging and 2D digital image correlation (DIC), as well as high speed thermal imaging. To verify the viability of the proposed system, experiments were conducted on Ti-6Al-4V (wt.%) at temperatures from 25°C up to and 800°C at an average strain rate of approximately 1200 s $$^{-1}$$ - 1 .

Evaluation of Different ZX Tensile Coupon Designs in Additive Manufacturing of Amorphous and Semi-Crystalline Polymer Composites

The layer-by-layer deposition of molten polymer filament in fused deposition modeling (FDM) has evolved as a disruptive technology for building complex parts. This technology has drawbacks such as the anisotropic property of the printed parts resulting in lower strength for parts printed in the vertical Z direction compared with the other two planes. In this manuscript, we attempt to address these challenges as well as the lack of standardization in sample preparation and mechanical testing of the printed parts. The paper focuses on process parameters and design optimization of the ZX build orientation. Type I tensile bars in ZX orientation were printed as per the ASTM D638 standard using two (2B) and four (4B) tensile bar designs. The proposed design reduces material loss and post-processing to extract the test coupons. Printing a type I tensile bar in the ZX orientation is more challenging than type IV and type V due to the increased length of the specimen and changes in additional heat buildup during layer-by-layer deposition. Three different polymer composite systems were studied: fast-crystallizing nanofiller-based high-temperature nylon (HTN), slow-crystallizing nanofiller-based polycyclohexylene diethylene terephthalate glycol-modified (PCTG), and amorphous carbon fiber-filled polyetherimide (PEI-CF). For all the polymer composite systems, the 2B showed the highest strength properties due to the shorter layer time aiding the diffusion in the interlayers. Further, rheological studies and SEM imaging were carried out to understand the influence of the two designs on fracture mechanics and interlayer bonding, providing valuable insights for the field of additive manufacturing and material science.

Structure design and vibration control of vibration reduction boring bar with variable damping

Structure design and vibration control of vibration reduction boring bar with variable damping

Progressive design of the take-up bar within the jet weaving machine for the production of 3D fabrics

Progressive design of the take-up bar within the jet weaving machine for the production of 3D fabrics

A digital-twin driven Split Hopkinson bar layout for the tensile characterization of thin, low impedance, sheet-like materials

The Split Hopkinson or Kolsky bar is one of the most popular devices when it comes to the mechanical characterization of material samples under high strain-rates. While testing of high impedance materials, such as metal alloys, is relatively straight forward, samples with low impedance pose certain challenges. The present work focuses on the detailed implementation of a high strain-rate tensile testing method for thin, low impedance, sheet-like materials by using the Split Hopkinson test principle. In order to find a suitable Split Hopkinson setup a digital twin was created using explicit finite element methods. With the help of the digital twin, the design of the transmission bar and the sample holders including the friction liners were explored. The numerical model indicated, that a hollow transmission bar with a moderate tapering (hollow bar 1.0) is suited for the characterization of low impedance materials over a wide strain-rate range. Furthermore, this setup has to be combined with an asymmetrical sample holder configuration (heavier on the incident side and lighter on the transmission side) and aluminum friction liners to return accurate results. This numerically derived setup was validated against experimental tests on paper, representative of low impedance, sheet-like materials.

3D printed indirect bonding trays: transfer accuracy of bar vs shell design in a prospective, randomized clinical trial.

To compare the transfer accuracy of two different indirect bonding (IDB) trays. Digital IDB was performed on a total of 30 patients using one of two designs: shell and bar trays, with 15 patients in each group. Trays were designed with the Appliance Designer software (3Shape A/S, Copenhagen, Denmark). Angular (torque, tip, angulation) and linear (mesiodistal, buccolingual, occlusogingival) differences were compared between the bonded intraoral scans taken immediately after IDB and the virtually bracketed model prepared in Ortho Analyzer software (3Shape A/S) using open source GOM inspect software (GOM GmbH, Braunschweig, Germany). There were no significant differences found between the bar and shell groups. Within the groups, significant tip differences were found between the incisors, canines, and premolars in both groups (P = .0001). Additionally, a statistically significant torque difference was found in the canines and incisors in the shell group. The percentage of values that deviated from the clinical acceptance limit was relatively higher in the bar group. Although there was no statistical difference between groups, the shell tray showed better results according to clinical acceptability limits. This study is important as it is the first clinical study to compare directly printed transfer trays with different designs.

A Biomechanical Comparison of the Back Squat and Hexagonal Barbell Deadlift.

Stahl, CA, Regni, G, Tanguay, J, McElfresh, M, Trihy, E, Diggin, D, and King, DL. A biomechanical comparison of the back squat and hexagonal barbell deadlift. J Strength Cond Res 38(5): 815-824, 2024-Coaches often use different exercises to encourage similar strength adaptations and limit monotony. Anecdotally, the hexagonal barbell deadlift (HBD) exhibits similarities to the back squat (BS). To date, research has not examined the empirical differences between these exercises. This study examined kinematic and kinetic differences between the BS and the HBD across different loads. Sixteen resistance-trained individuals (6 men and 10 women) volunteered to participate. Subjects performed 1-repetition maximum (1RM) testing under BS and HBD conditions. Kinematic and kinetic data were collected during performance of both exercises at submaximal (warm-up sets) and maximal (1RM) loads using a 3D motion capture and force-plate system. Results showed that subjects lifted greater 1RM loads in the HBD relative to the BS (p < 0.05; d = -1.75). Kinematic data indicated that subjects exhibited greater maximum forward lean of the trunk and decreased maximum knee flexion while performing the HBD compared with the BS. The BS resulted in higher maximum extension moments at the hip joint than the HBD. Maximum extension moments at the knee joint showed no difference between the exercises. Data suggest that bar design and position facilitate balanced moment arm length at hip and knee joints during performance of the HBD. By contrast, bar position during performance of the BS increases moment arm length at the hip joint, making it a hip-dominant exercise. The present data have implications for the programming of both exercises. Future research should examine differences in muscle-activation strategies between the 2 exercises.

Applicability of a new composite amusement ride safety device based on acoustic emission monitoring technology

Under the premise of ensuring safety, it is of great significance to realize the lightweight of the non-main load-bearing parts of amusement facilities. The purpose of this study is to study the failure process of a newly designed carbon fiber bumper by using acoustic emission technology. First of all, the design of carbon fiber anti-collision bar can effectively restrain passengers, and its weight is reduced by nearly two-thirds compared to traditional metal materials. Subsequently, the load-bearing capacity of the bumper was tested and acoustic emission monitoring was carried out. The test results show that this new type of combined structure of amusement facility has high reliability, which exceeds the safety factor of 3.5 required by the steel structure of amusement facility. In addition, Renyi entropy was used to select the best window function of short-time Fourier transform, and the frequency domain characteristics of acoustic emission signals of typical damage modes were discussed through appropriately selected windows function. A classifier based on supervised machine learning is established by combining frequency features and acoustic emission feature parameters. Furthermore, the use of classifiers helps to understand the damage behaviour of composite structures.

온라인 마켓의 평점 제공을 위한 시각화 디자인 방식에 따른 소비자 의사결정 편향

This study investigated the biases associated with commonly used bar or star designs for visualizing product or service reviews in online markets. Previous research has shown biases in decision-making when inferring average scores using bar graphs, but it remained unclear whether similar biases exist with star shapes or other visualization designs. Therefore, it is crucial to examine whether the methods of using bar, star, and violin plot designs for product reviews actually induce biases in people's judgment of scores. A total of 257 participants took part in the study, where they were presented with product rating designs created using bar, star, and violin plot methods and asked to make decisions. The results revealed biases in bar and star designs compared to violin plot. This suggests that biases may occur due to human perceptual characteristics even when providing simple average rating designs and indicates that violin plot methods, which provide information on both average and distribution simultaneously, may help reduce biases in specific decision-making tasks.

New Computerized Planning Algorithm and Clinical Testing of Optimized Nuss Bar Design for Patients with Pectus Excavatum.

BACKGROUND Computer-aided design (CAD) has been used in the Nuss procedure to determine the bar length and shape. Despite computer aid, the shape and design remain quite intuitive. We tested a new algorithm to determine the optimal bar shape. MATERIAL AND METHODS The normal sterno-vertebral distance was defined on computed tomography (CT) scans of patients without pectus excavatum (PEx) at the same level where the deepest depression was found on CT scans of 97 patients with PEx. Four points were marked on the CT scan of 60 patients with PEx at the deepest deformity: P1: edge of the vertebra; P2: edge of the deformity; P3: the expected contact point of the bar and the rib; and P4: the expected end of the bar. The algorithm generated 3 circles upon these points, and the fusion of the arcs drew the line of the ideal bar. Corrected and normal sterno-vertebral distance values were compared with the Mann-Whitney U test. Ten bars were bent manually guided by a 1: 1 printout of the designed bar and were implanted in 10 adolescents. RESULTS The shortest sterno-vertebral distance was 3 cm below the intermammillary line in PEx patients. The normal mean sterno-vertebral distance at this level was 10.16±1.35 cm in non-PEx patients. The mean virtually corrected sterno-vertebral distance was 10.28±1.27 cm. No significant difference was found (P=0.44). The bars were seamless and were successfully implanted. No bar needed adjustment, the operation time was shorter, and the patient satisfaction score was 9.4/10. CONCLUSIONS With our new algorithm, an optimal Nuss bar can be designed.

Effect of bar designs on peri implant tissues health in implant-supported removable prostheses: a systematic review

Different characteristics of bars (cross-sectional shape, diameter, distal extension etc.) lead to different biomechanical behavior (retention and stress) with implants and peri-implant tissues.Aim: To evaluate the impact of implant-supported removable prostheses bar designs in fully edentulous arch (in the maxilla and/or mandibula), with 4 implants or more, on the peri-implant soft and hard tissues.Two reviewers searched for observational studies, RCT and in vitro studies, published on five main databases and three from the grey literature, without restrictions on November 2023.Of the 3049 selected articles, four met the inclusion criteria. Four RCT evaluated peri-implant health tissues in full edentulous arches with 4 or 6 implants rehabilitated with implant bar overdentures. One prospective study with 5 years follow-up evaluated the success/survival rate of implants and implant bar overdentures. Overall, 261 subjects were enrolled in our systematic review with 1176 implants. Overdentures’ survival rate was 100%. There was a trend that plaque indices and gingival indices were low in all of the studies, however no statistical analysis was done due to the lack of information.Due to the lack of information in the included studies, we cannot confirm if bar characteristics affect the peri-implant tissues health.

Multi-objective optimization design of anti-roll torsion bar using improved beluga whale optimization algorithm

PurposeThis study aims to reduce the redundant weight of the anti-roll torsion bar brought by the traditional empirical design and improving its strength and stiffness.Design/methodology/approachBased on the finite element approach coupled with the improved beluga whale optimization (IBWO) algorithm, a collaborative optimization method is suggested to optimize the design of the anti-roll torsion bar structure and weight. The dimensions and material properties of the torsion bar were defined as random variables, and the torsion bar's mass and strength were investigated using finite elements. Then, chaotic mapping and differential evolution (DE) operators are introduced to improve the beluga whale optimization (BWO) algorithm and run case studies.FindingsThe findings demonstrate that the IBWO has superior solution set distribution uniformity, convergence speed, solution correctness and stability than the BWO. The IBWO algorithm is used to optimize the anti-roll torsion bar design. The error between the optimization and finite element simulation results was less than 1%. The weight of the optimized anti-roll torsion bar was lessened by 4%, the maximum stress was reduced by 35% and the stiffness was increased by 1.9%.Originality/valueThe study provides a methodological reference for the simulation optimization process of the lateral anti-roll torsion bar.

An overview of implant overdenture attachment systems

Implant-retained overdentures have revolutionized dental prosthetics, addressing the limitations of traditional removable dentures. These overdentures rely on attachment systems to anchor them to dental implants or abutments, improving stability, retention, and functionality. Common attachment systems include locator attachments, bar attachments, magnets, Hader clips, ERA attachments, telescopic crowns, and OT equator attachments. Each offers unique benefits and retention levels. Implant survival rates are influenced by various factors, including attachment type, but overall, attachment choice may not be the primary determinant of implant success. Attachment systems that evenly distribute forces, like bar attachments, contribute to implant stability. Marginal bone loss can affect implant stability and is influenced by attachment systems. Precision attachments, such as telescopic crowns, have shown reduced marginal bone loss in practice. Soft tissue complications, including inflammation and mucositis, vary by attachment but can be managed with proper oral hygiene. Retention, crucial for function, varies with attachment type and implant number. More implants generally improve retention, although it may decrease over time. Bar attachments typically provide superior retention. Maintenance is essential, with some debate over whether bar or stud designs entail more upkeep. Patient satisfaction is high with both bar and ball attachments, while magnets may pose retention issues. The choice of attachment depends on patient needs and clinical factors, with regular follow-up and maintenance essential for long-term success.

Optimization of the mechanical properties of machine tool with steel reinforced mineral concrete

High damping and high static stiffness are essential to improve the static and dynamic characteristics of machine tools. Traditionally, the structural parts of machine tools are usually made of cast iron and steel, which may lead to poor surface finish and inaccurate dimensions of finished products. Therefore, many scholars have investigated other alternatives of structural material for machine tools, such as concrete, polymer concrete and epoxy granite. Although epoxy granite has better damping properties, its structural stiffness (as measured by Young’s modulus) is only 1/3 of the gray cast iron. Thus, this study would introduce several steel bar designs into epoxy granite to improve the static stiffness and quantitatively review the performance by finite element analysis. The results showed that the equivalent static stiffness and natural frequency were about 12 to 20% higher than the structural material of cast iron. Therefore, the proposed finite element model of vertical machining center (VMC) column in epoxy granite could serve as a feasible alternative to achieve higher damping or static stiffness, as it was also more environmentally friendly to the manufacturing process.

A FEM-Based Comparative Study of the Effect of Rotor Bar Designs on the Performance of Squirrel Cage Induction Motors

Induction motors (IM) are the most frequently used type of motor in the industry. The number of rotor slots, bar geometry, and conductivity of bar material have a strong impact on the torque profile and efficiency characteristics of induction motors. This study focused on investigating the effect of different rotor bar designs on motor performance by the finite element method (FEM). The IMs have been designed using the same stator core, winding, and core lengths. The total rotor bar cross-section areas are also fixed throughout all designs. In addition to the change in the number of rotor bars and geometry, the effect of copper and aluminum bar materials on motor performance was also investigated, both for single and double-layered squirrel-cage structures. The results of the study indicate that the starting torque of the motor in a 36/30-slot aluminum single-cage structure was obtained as 96.26 Nm, while the starting torque of a 36/46-slot aluminum double-cage structure was found to be 115.34 Nm. It is also found that the starting torque of the initial design can be increased by up to 19.82% by changing only the rotor bar numbers and material with the same stator and rotor size. The efficiency of the motors was determined as 86.6% for both designs. In addition to efficiency, the output torque ripple has been decreased to 2.63, which equals a 67.32% decrease in the ripple of the initial design. The improved design has an approximately 8 °C lower T2 due to better cooling performance as a result of a higher number of rotor slots.

Crashworthiness design of GFRP bar reinforced concrete bridge pier subjected to truck collision

This study investigates the failure behavior and post-impact damage of glass fiber reinforced polymer (GFRP) bar reinforced bridge pier under truck collision. The finite element model of a benchmark bridge with its pier reinforced with GFRP bars collided by a medium truck is established using LS-DYNA. The effectiveness of adopted material models and contact algorithm is verified by comparing the experimental and numerical observations of scaled GFRP reinforced concrete columns under horizontal impact loading. The failure analysis results show that the post-impact damage of the composite pier can be classified into four levels, and the shear force at pier bottom is a reasonable index that can represent the dynamic shear capacity of the composite pier. Besides, the influence of design variables on the dynamic shear capacity of the bridge pier is clarified, and a closed-form formula is proposed to predict the dynamic shear capacity based on response surface methodology. Furthermore, kinetic energy-based damage index and damage evaluation approach are developed to forecast the post-impact damage levels of the composite bridge pier. Finally, combining the post-impact performance objectives and damage evaluation approach, a performance-based crashworthiness design framework is developed and validated to provide a basic reference for design consideration of GFRP reinforced concrete bridge pier.

Design and Analysis of Anti-Roll Bar in Formula Vehicle

Abstract: This study explains a coherent flow for designing, analyzing, and testing a tuneable anti-roll bar system for a formula student race-car. The design process starts with the analytical calculation for roll stiffness using constraining parameters such as CG (Centre of Gravity) height, total mass, and weight distribution in conjunction with suspension geometry. Then, the material selection for the design i.e., Aluminium 7075 T6 is made based on parameters such as density and modulus of rigidity. A MATLAB program is used to iterate defection vs load for different stiffness and shaft diameter values. This is then checked with kinematic defection values in FUSION 360s geometry. To validate with the material defection, finite element analysis is performed on ANSYS workbench. Manufacturing accuracy for the job is checked using both static analysis in lab settings and using sensors on vehicles during ontrack testing. The error percentage is found to be 4% between the target stiffness and the one obtained from static testing. Parameters such as moment arm length, shaft diameter and length, and defection were determined and validated. This paper shows the importance of an anti-roll bar device to tune the roll stiffness of the car without interfering with the ride stiffness.

Heat‐sealing and microscopic evaluation of paper‐based coated materials using various seal bar geometries in vertical form fill seal machine

AbstractWith the growing emphasis on minimization of global plastic waste, flexible fibre‐based packaging has gained significant interest over the past few years. Heat‐sealing technology is commonly applied for vertical form‐fill‐seal machine to provide tight closure of packages for maintaining food quality and shelf life. Several different seal bar geometries and adequate heat‐seal parameters are required to improve the seal tightness of the packages. This study aims to compare the heat sealability of thermoplastic film (OPP/PE) and paper‐based materials in vertical form‐fill‐seal machine using various seal bar profiles. The investigation includes seal strength measurement, understanding the causes of leak formation, seal tightness and inspection of the seal using scanning electron microscopy. Results reveal that OPP/PE material has exceptional seal strength and leakproof ability compared with paper‐based materials. However, it has limited operating window because the material shrinks and coarsens at approximately 140°C. Sealing temperature and dwell time are found to be the major factors affecting the seal strength of paper‐based material. Results reveal the PE‐coated papers exhibit nearly twice the seal strength compared with the dispersion‐coated paper. It was difficult to achieve good hot‐tack values with dispersion‐coated paper. During testing, all the paper‐based materials experience delamination and fibre tear, and its severity increases with the increasing material grammage. As plateau temperature is reached, the fibre delamination remains relatively constant. The serrated geometry of seal bar design plays a significant role in providing a satisfactory airtight seal, particularly around the pouch's layer jump. However, flat seal bar designs are not recommended for gas tight applications for paper‐based materials.

Truss imperfections in the design of bar and diaphragm bracing systems

In the article three variants of roof bracing were considered: bar bracing, diaphragm bracing and the combination of bar and diaphragm bracing. Different analytical and numerical ways of taking into account the imperfections of the truss girder were compared. The entire 3D model of the roof (shell and beam elements with the eccentricities taken into account) was analysed numerically. Selected stressed-skin aspects were considered. Stabilizing forces in the purlins and forces in bracing elements (bar and/or diaphragm bracing, connections) were observed. The importance of the imperfection issues (e.g. shape of the imperfection, method of including imperfection, wind forces) was evaluated numerically to indicate the key points in the design procedure. The biggest forces in purlins occurred for “nonstandard” shape of the imperfection. On the other hand, in case of bracing elements, when wind forces were taken into consideration, “standard” approach of including the imperfection was safe approximation. Moreover, the diaphragm took over significant part of the bracing forces, however the distribution of the forces depended strongly on the flexibility of the bracing and purlin/truss connection.