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Aerospace thin-walled parts vibrates during the process of milling due to their characteristics of low rigidity, which influences the machining quality of the workpiece. Based on the characteristics of magnetorheological fluid excitation solidification, a magnetorheological damping fixture is designed to semi-actively suppress the vibration generated during the machining process. This paper simplifies the multi-characteristic structure of aerospace thin-walled parts into rectangular thin plates. In accordance with Kirchhoff G.’s small deflection bending theory of elastic thin-plates and Daramberg’s principle, the differential equations for the transverse vibration of the thin-walled parts are established, which aims to obtain the natural frequency as well as vibration mode function of the thin-walled parts. In consideration of damping characteristics and the external dynamic milling force after the magnetorheological fluid excitation solidification, this paper uses the mode superposition method and an improved dynamic response mathematical model of the magnetorheological damping fixture thin-walled parts system of the linear multiple degrees of freedom, which has different volumes of magnetorheological fluids under forced vibration, was established. The maximum error between the predicted and measured values ​​of the fixture-workpiece system dynamic response of displacement and acceleration is 16.2% and 15.5%, respectively. Finally, this paper verifies the feasibility as well as the effectiveness of the model through dynamics experiment and milling machining experiment.

Designing and installing jigs and fixtures for new products are very costly tasks. In order to rapidly respond to frequent product changes in a manufacturing system, we developed a transformable pin array fixture system including reconfiguration planning software that finds the optimal position for mounting an assembly part and automatically generates a pin height control code. We first classified main fixturing quality factors such as type of contact, distance between a pin and a joining point, and part shape. We then formulate the part positioning problem as an alignment problem between the joining point set and the pin point set in the xy plane in consideration of the fixturing quality factors. A car door trim assembly module was used to verify the proposed method. Finite-element analysis results showed that in a car door trim assembly process such as ultrasonic welding and screwing, relocating an assembly part at the optimal position reduces its deformation.

The assembly process of car body in white (BIW) in body shop is a very important link in the whole vehicle manufacturing process. Hundreds of stamping parts must be located and joined on the correct location of the platform, and the related accuracy influence the performance and quality of the cars. To guarantee the BIW manufacturing accuracy, the dimension control is a critical task in each automobile production line. In Comparison to traditional offline dimension control, this article proposed an event-triggered feedforward predictive control method to realize real-time inline dimension control during BIW assembly process. Experiments based on the actual production data from BMW Brilliance Automotive Ltd. demonstrate this control strategy can significantly improve the final products key point pass rate and decrease the fixture adjustment frequency.

Friction stir welding (FSW), a solid-state joining process, is commonly used to join Aluminum alloys in aerospace, marine, car industry, and numerous industrial applications. Lightweight materials are commonly used in the transport industry to minimize component weight, and thin-walled structures are increasingly being used as energy-absorbing components in the industry. Even though FSW of plates is well established, FSW of pipe is still at the laboratory level. In this work, FSW for 6063 aluminum alloy pipe has been experimented through a novel procedure and it’s flexural and crashworthiness studies are carried out. The attempt of FSW is performed with a unique welding fixture mounted on a traditional milling machine. The crashworthiness test is conducted to analyze the ability of the structure to nullify the life loss during impact and the crash force efficiency of the pipe is identified. It is further analyzed for the flexural test to identify the bending load of welded aluminum alloy pipes. This study also exposes the basic understanding of the FSW procedure and its metallurgical implications of a friction stir welded pipe.

Small scale organizations strive to achieve maximum output with limited availability of resources. An effective plant layout plays a significant role in enhancing the overall productivity and efficiency of an organization. Using a fixture for holding a job ensures accurate alignment and reduces defects in finished components. This paper discusses the implementation of an optimized plant layout and designing a fixture for welding of pipes. The existing plant layout had unused spaces and unscientific arrangements of machines. There was a need for a fixture which would reduce the defects caused due to alignment errors during welding. This could be achieved by the use of a fixture table, supporting unit and clamping unit. The use of weld-fixture reduced the rework from the existing 10% to 5%. The proposed plant layout computed using CRAFT simulation tool reduced the material travel distance. This resulted in the reduction of material handling costs by 15%.

The aim of this study was to compare classical friction (FR) in passive self-ligating brackets (P-SLBs), active self-ligating brackets (A-SLBs) and a traditional twin bracket, in vitro, and to identify the point of initiation of bracket–archwire engagement. Nine bracket systems of 0.022 in slot size were FR tested: 5 P‑SLB systems; 4 A‑SLB systems; and a control group of twin brackets with elastomeric ligatures. Single upper right central incisor brackets were mounted on a custom metal fixture for testing. Straight sections of various round and rectangular nickel–titanium (NiTi) archwires (0.016, 0.018, 0.018 × 0.018, 0.020 × 0.020, 0.016 × 0.022, 0.017 × 0.025, 0.019 × 0.025, and 0.021 × 0.025 in) were ligated to the bracket and peak static FR (cN) was measured with an Instron Universal Testing Machine. Ten unique tests each utilizing a new bracket and new archwire were conducted for each group in the dry state. FR was significantly different between control, P‑SLB and A‑SLB systems (P

Dental implants are fixtures that constitute for the replacements of the root of a missing natural tooth. Dental implant therapy has been widely used for the restoration of partially and fully edentulous patients. The implant literature emphasizes the importance of a passively fitting prosthesis to prevent prosthodontic complications or even loss of fixture integration. Failure to achieve a passively fitting prosthesis and force tightening of superstructure may result in complications such as abutment, framework, and gold screw loosening or fracture. Various materials that can be used for making an implant impression are polyether, polyvinylsiloxane, condensation silicone, polysulfide, irreversible hydrocolloid material, and various others. There are various studies in relation to the accuracy of these impression materials out of which various scientists concluded different results with most studies stating polyether with the maximum amount of dimensional accuracy in comparison to other materials. An accurate implant impression plays a significant role and serves as a starting point in the process of producing good working casts. Thus, the accuracy of impression techniques becomes a significant issue in consideration of passive fit. Reproduction of intraoral relationship of implants through impression procedures is the first step in achieving accurate fit prosthesis. This transference is still complicated by the number, angulation, depth, and position of implants. The advent of computer-aided design/computer-assisted manufacturing technology improved the framework fabrication procedures and has increased the precision of fit of implant prosthesis.

This study sought to examine differences in measures of intense periods of physical performance during competitive match-play, between one-match (1 match weeks) and two-match microcycles (2 match week). 1, 3 and 5 min "peak" and mean averages for total distance (TD), high-speed running (HSR) and metabolic power (MP) were analysed for each 15 min period of match-play. Linear mixed models were employed to examine the differences in dependent variables for each method of measurement between the 1 and 2 game microcycles. No differences were reported for "peak" values for all epoch lengths, however, results revealed significantly reduced "average" values, during periods of fixture congestion, for 1, 3 and 5 min epochs for average TD, and 3 min epochs for average HSR towards the end of the match (75-90 min split). There was, however, a trend for the opposite response to occur in the 60-75-min period. The current data suggests that players potentially display altered pacing strategies during periods of fixture congestion, with these observed responses being dependent on sampling method and epoch length.

The spring system is the key component of linear compressor, which is attractive in the field of household refrigeration due to its high efficiency and compact structure. Inspired by the traditional flexure spring, we proposed a novel cylindrical arm spiral spring for linear compressor with a comprehensive consideration on the cost, compactness and performance requirements. The design method of spring was introduced and different performance can be obtained by adjusting the internal radius, external radius, number of turns and wire diameter. The static displacement of spring was modelled by using FEA (Finite Element Analysis) method for various axial and radial force. And a specific fixture was built to measure the spring stiffness to verify the results obtained from FEA simulation. At last, the dynamic test of the linear compressor equipped with the proposed spring was conducted. The experimental results showed that the resonant frequency of linear compressor can meet the design requirements of 78 Hz without gas compressor, indicating that the application of this type of spring in the linear compressor is feasible.

This paper investigates the failure load prediction of anisogrid cylindrical composite lattice structures under axial compression. The failure criterion to predict compressive failure load of lattice structure is developed by using the compression test results of representative subelement specimens including several unit cells. Compression tests of subelement using two different fixture jigs which generate different ratio of bending to compressive stress in the knot region of lattice structures were performed. The critical stress function is introduced from the compression test results and is utilized in failure criterion. The finite element analysis is used to calculate the failure load with the proposed failure criterion and also the buckling load for the full-sized cylindrical lattice structures. The compression failure loads for two different full-sized cylindrical lattice structures agreed well with the predicted failure loads by using the failure criterion proposed in this paper. The results of these studies indicate that the proposed failure criterion for the cylindrical composite lattice structures under compressive load in this work can be applied to the stress analysis and optimization problem in the preliminary design phase.

Objectives. The impression-taking technique is one of the most critical factors that not only prevents the shrinkage caused by polymerization but also enhances the accuracy of implant impressions. Also, choosing the right time of taking impressions after splinting implants is one of the important criteria that affects the impression-taking technique. Accordingly, the present study aimed to evaluate the accuracy of different splint methods for implant impressions made at different times. Methods. In this in vitro study, a two-piece metallic index was prepared, and the patient’s jaw was simulated by placing self-cured acrylic resin in the lower part of the index. Then, two holes were made in the acrylic resin at a specific distance from each other, and the analogs were placed in these holes. Splinting of impression copings was carried out with autopolymerized acrylic resin (GC Pattern resin LS, GC America Inc., USA), and an open tray impression approach was performed. Thirty-six casts in three groups (n = 12) were fabricated from the acrylic model. After scanning the casts, the impression accuracy was compared between the three study groups by measuring the distance between the outer portions of the scan bodies screw-retained on implant analogs inside the cast using the Exocad software (2015.07 version). Group 1: splinting impression copings with autopolymerized acrylic resin and impression making immediately after the setting time (4 minutes); group 2: splinting and impression procedure after 17 minutes with splint sectioning and reconnection; group 3: splinting and impression procedure after 24 hours with splint sectioning and reconnection. The data were analyzed using SPSS 17 using the Kruskal–Wallis test. Results. The mean distance measured in group 1 was 19.14 ± 0.029 mm, which was significantly lower than the main model. The distances were 19.15 ± 0.039 and 19.159 ± 0.33 mm in groups 2 and 3, respectively. These two groups were not significantly different from the main model. Moreover, the mean distance measured in the three impression techniques was similar. Conclusions. There was no significant difference in the measurements between group 2, group 3, and the main model. Therefore, dentists can make an impression after 17 minutes to reduce chair time.

Fixture hardening is the process of choice when thin-walled, carburized gears need to be heat treated with minimal distortion. Only a few publications have studied and described the phenomena taking place in carburized gears during a fixture hardening process. An integrated approach is proposed to improve the design of hardening fixtures and introduce new strategies and instrumentation to better understand and control the process. The proposed approach is to tightly integrate the knowledge in metallurgy, numerical simulation, process control, and machine design areas to mutually compensate and overcome the current limitations in each single area. An instrumented fixture is designed for a reference gear and tested on an industrial quenching press. The signals from the fixture are combined directly with the signals from the quenching press, recorded, and used to validate and improve the numerical simulation models. Metallurgical simulations are used to predict temperature distribution, phase transformations, distortion, and to identify new process strategies.

Dimensional and form accuracy of the workpiece can be improved by effective fixture layout design which shows minimum deformation of the workpiece during machining. Flexible fixtures are inevitable in industries owing to high product variety and shortened production time. Hence, an integrated approach is presented to select the optimum position of locating and clamping elements in a flexible fixture that provide good form accuracy. In this approach, a Parametric Finite Element Model (PFEM) is developed using the information about the workpiece, fixture plan and machining condition. PFEM is used to predict the elastic deformation of the workpiece for the fixture layouts generated using a discrete Genetic Algorithm (GA) with mixed integer-discrete variables. The objective is to minimize the maximum deformation of the workpiece by optimizing fixture layouts. The stability of the workpiece and fixture system is ensured by implementing non-negative reaction force constraints in GA. The proposed approach is applied for a prismatic workpiece to carry out pocket milling operation. The significance of this work is to express the flexibility and computational effectiveness of PFEM to accommodate variation in the workpiece, machining condition and fixture plan while designing flexible fixtures. Further, it highlights a significant reduction in search space due to the use of discrete GA and stability constraint as it takes less objective function calculations. An experimental analysis is performed to study the effectiveness of the proposed approach. Therefore, the proposed approach provides a viable solution to the optimization problem in flexible fixtures.

Pipeline leakage and pipeline internal corrosion are two serious threats to pipeline safety operation. In this study, based on the measurement theory of pipeline internal diameter variation and a numerical simulation analysis of existing sensor shortcomings, a novel FBG pipe-fixture sensor is designed and developed to detect pipeline leakage and monitor pipeline internal corrosion simultaneously. A calibration test is conducted, and the test results indicate that the FBG pipe-fixture sensor solves the problem of a large difference between the test values and the theoretical values and eliminates the limitation of measurement range. To validate the actual performance of the sensor, a pipeline leak detection test and a pipeline internal corrosion monitoring test are, respectively, conducted on a steel pipe leak test platform and a steel pipe with different simulated corrosion levels. The test results demonstrate that the FBG pipe-fixture sensor can effectively detect pipe leakage and decrease the localization error of the leakage point to within 1 m. The sensor can also effectively monitor pipe internal corrosion and evaluate the internal corrosion degree with a measurement accuracy of 0.1 mm. The novel FBG pipe-fixture sensor may be a potential sensor for pipeline leak detection and pipeline internal corrosion monitoring.

Orthopaedic surgical cutting instruments are required to generate sufficient forces to penetrate bone tissue while minimising the risk of thermal and mechanical damage to the surrounding environment. This study presents a combined experimental–computational approach to determine relationships between key cutting parameters and overall cutting performance of a polyurethane-based synthetic trabecular bone analogue under orthogonal cutting conditions. An experimental model of orthogonal cutting was developed, whereby an adaptable cutting tool fixture driven by a servo-hydraulic uniaxial test machine was used to carry out cutting tests on Sawbone® trabecular bone analogues. A computational model of the orthogonal cutting process was developed using Abaqus/Explicit, whereby an Isotropic Hardening Crushable Foam elastic-plastic model was used to capture the complex post-yield behaviour of the synthetic trabecular bone. It was found that lower tool rake angles resulted in the formation of larger discontinuous chips and higher cutting forces, while higher rake angles tended to lead to more continuous chip formation and lower cutting forces. The computational modelling framework provided captured features of both chip formation and axial cutting forces over a wide range of cutting parameters when compared with experimental observations. This experimentally based computational modelling framework for orthogonal cutting of trabecular bone analogues has the potential to be applied to more complex three-dimensional cutting processes in the future.

Success or failure of implants depends on the health of the person receiving the treatment, drugs which affect the chances of Osseo integration, and the health of the tissues in the mouth. The amount of stress that will be put on the implant and fixture during normal function is also evaluated. Planning the position and number of implants is key to the long-term health of the prosthetic since biomechanical forces created during chewing can be significant.

The structural behavior and safety of a static load test fixture for a pylon and an external fuel tank of a fixed-wing aircraft currently being developed in South Korea are analyzed. The test loads are calculated via the flight loads applied on the external fuel tank and a whiffletree configuration; subsequently, they are used in the static analysis of the test fixture using the finite element method. Vulnerable components of the test fixture are identified by calculating the von Mises stress, and detailed structural behavior is analyzed. It is confirmed that most components of the test fixture exhibit a factor of safety of 3.0 or greater, which is determined by the calculated von Mises stress and the yield strength of the material. The proposed method is expected to be utilized in the structural integrity evaluation of a static test fixture for the external stores of an aircraft.

In the blade computer numerical control (CNC) machining process, the machining fixture design for each type of blade will be a very difficult task due to the large variety and quantity of blades. This study proposes a computer-aided machining fixture design algorithm and software based on case learning. The three-dimensional model of the case learning blade and the target blade is firstly projected into a cylinder surface based on the projection algorithm, and the cylinder surface is expanded into a two-dimensional plane based on expansion algorithm. Then, the matching machining fixture layout of the target blade relative to the case learning blade is obtained in two-dimensional space by the mesh affine transformation algorithm according to the geometric edge constraints and the matching relationship of the case learning blade and target blade. At last, the inverse transformations of projection and expansion are used to obtain the final fixture layout of the target blade three-dimensional model based on the previous projection and expansion relationship. The special computer-aided fixture design software of near-net shaped blade is developed, and the machining fixture design and CNC machining experiment based on two typical near-net-shaped blades proved that the computer-aided fixture design algorithm based on case learning is feasible and can be used to realize the intelligent design of near-net-shaped blade machining fixture.

Bu çalışmada, helikopter transmisyonunun montajında kullanılacak bir montaj fikstürü tasarlanmış ve Dijital İnsan Modelleme (DHM) yöntemleri kullanılarak ergonomik koşullara uygunluğu analiz edilmiştir. Analizlerde Hızlı Üst Ekstremite Değerlendirmesi (RULA) ve Biyomekanik Hareket Analizleri (BMA) kullanılmıştır. İnsanın ergonomik yeterliliği, iki farklı montaj koşulu için deneysel olarak analiz edilmiştir. Yeniden tasarlanan montaj fikstürü, geleneksel olanlara göre önemli ergonomik avantajlara sahiptir. Analizlere göre L4-L5 lomber vertebra disklerinde oluşan kompresyon yüklemesinde % 79,6, moment yüklemesinde % 94,3 avantaj sağlanmıştır. Sonuç olarak, işçilerin daha rahat ve güvenli bir şekilde çalışması için tasarlanan ergonomik montaj armatürünün amacına uygun olduğu ortaya çıkmıştır., Digital Human Modeling (DHM) is an integral part of computerized engineering studies. In this study, an assembly fixture has been designed that will be used in the assembly of the helicopter transmission and it has been analyzed for compliance of ergonomic conditions using DHM technique. Rapid Upper Limb Assessment (RULA) and Biomechanical Motion Analyses (BMA) were used in the analyses. The ergonomic competence of the human was analyzed empirically for two different assembly conditions. The assembly fixture redesigned has significant ergonomic advantages over the conventional ones. According to the analyses was provided that 79.6 % advantage in compression loading and 94.3 % advantage in moment loading, which occurs on the L4-L5 lumbar vertebra discs. As a result, it was revealed that the ergonomic assembly fixture designed for workers to work in a more comfortable and safe manner was suitable for its purpose.

Wire electric discharge machining (WEDM) is nonconventional machining that provides machining solutions irrespective of the material hardness. In the present study, a simple profile was machined on Microfer 4722 at different slant angles using to know the effect of machining parameters. A unique method of obtaining taper components was employed by slant type taper fixture to avoid the disadvantages of the conventional method. The profiling speed, profile roughness, profiling error (Corner error), recast layer thickness, micro-hardness, microstructural and metallurgical changes of the machined component were investigated. As the taper of the component increases the profile roughness, corner error increases although profiling speed decreases. It is observed that recast layer thickness decreases as the taper of the component increases. A contrasting phenomenon is observed in the case of hardness at the WEDM surface. The metallurgical changes like the addition of Cu, Zn and O in the nickel-based alloy after machining from WEDM at different slant angles are highlighted. It is observed that residual stress decreased as the slant angles increased from 0° to 30° during slant type profiling.

Mixed-mode I–II crack-based fatigue crack propagation (FCPI–II) usually occurs in engineering structures; however, no theoretical formula or effective compliance test methods have been established for FCPI–II to date. For mixed-mode I–II flawed components, based on the principle of mean-value energy equivalence, we propose a theoretical method to describe the relationship between material elastic parameters, geometrical dimensions, load (or displacement), and energy. Based on the maximum circumferential stress criterion, we propose a uniform compliance model for compact tensile shear (CTS) specimens with horizontal cracks deflecting and propagating (flat-folding propagation) under different loading angles, geometries, and materials. Along with an innovative design of the fixture of CTS specimens used for FCPI–II tests, we develop a new compliance-based testing method for FCPI–II. For the 30Cr2Ni4MoV rotor steel, the FCP rates of mode I, mode II, and mixed-mode I–II cracks were obtained via FCP tests using compact tension, Arcan, and CTS specimens, respectively. The obtained da/dN versus ΔJ curves of the FCP rates are close. The loading angle α and dimensionless initial crack length a0/W demonstrated negligible effects on the FCP rates. Hence, the FCP rates of mode I crack can be used to predict the residual life of structural crack propagation.

It is very prone to cause large-amplitude cutting vibrations, or even regenerative chatter, when milling thin-walled workpiece due to its low dynamic stiffness. The utilization of fixture support is one of the most effective measures to mitigate vibrations and improve stability limits, which has gained more and more attention. However, the dynamics model of the tool-workpiece-fixture system and the influence of fixture support force have not been fully developed. In this paper, a pneumatic fixture is designed and used to exert controllable support force on the thin-walled workpiece by precisely tunning the air pressure. The position-dependent modal parameters of the thin-walled workpiece under different fixture support forces are identified by combining experimental modal test and finite element analysis. The milling dynamics is then modeled into a delay differential equation with position-dependent coefficients. On this basis, the three-dimensional stability lobe diagrams (SLDs) are obtained in the parameter space of tool path, spindle speed, and axial depth of cut. Both stable and chatter cutting tests are performed to verify the predicted SLDs, and the cutting signals under different fixture support forces are compared in detail. Experimental results reveal that the proposed model can accurately predict the chatter stability of thin-walled workpiece with fixture support, and the stability limit can be successfully improved by tunning the support force. Some important conclusions on the influence of fixture support forces are also drawn based on detailed simulation and experimental analyses.

Over-the-air (OTA) measurement is mandatory for 5G mm-wave wireless devices. The compact antenna test range (CATR) is the baseline method in the current version of TR 38.810 in 3rd generation partnership project (3GPP) and cellular telecommunications industry association (CTIA) millimeter-wave (mm-Wave) test plan. For CATR, both amplitude and phase variations inside the quiet zone (QZ) could affect the final OTA results significantly and hence need to be characterized carefully. Especially in the phase validation of QZ, even slight misalignments between sampling plane and incident plane wavefront due to the limited precision of the positioner or tolerance in antenna fixture could result in large phase variations, which is not the true phase property of QZ. This letter presents a method to remove the effect of the angular error due to misalignment when measuring the phase variation inside QZ. By adopting the proposed method to the measured phase data, any angular error due to misalignment with respect to the incident plane wavefront will be eliminated mathematically, leaving the true phase variations of QZ only. In the meanwhile, the proposed method can alleviate the requirements of fixture manufacture and alignment precision and reduce the test cost.

Due to the low rigidity, the milling process of cantilever thin-walled structure (CTWS) inevitably generates machining-induced deformation, ultimately resulting in poor surface quality and thickness accuracy. In this paper, to avoid these issues, a novel and green ice-based fixture (IBF) is innovatively proposed to hold CTWS firmly to suppress machining deformation during the whole processing. Firstly, a stair-step model is established to express machining-induced deformation of CTWS with/without IBF. Next, IBF is designed to clamp CTWS steadily. Secondly, finite element model (FEM) for CTWS is utilized to simulate milling deformation with/without IBF to reflect the effect of IBF on eliminating CTWS deformation. Finally, the experiment of CTWS milling is carried out, and the experiment results show that IBF can achieve a reliable and stable holding for CTWS, and hence suppress machining-induced deformation and improve thickness accuracy. In this paper, research on IBF for CTWS processing provides reference and guidance for the application and promotion of IBF in industry.

In the field of aviation and astronautics, large complex surface parts such as aircraft cabin cover are complex, varying in model, and produced in small batch. In order to reduce fixture cost and improve production efficiency, a variable multipoint and multi-DOF supporting fixture is designed. The coordinate system of the complex structure fixture is defined, and the kinematics of the multibody structures driven by air cylinders are modeled according to the topological principle. With the help of this data structure, fast and optimal search for clamping state can be realized. With the dichotomy method, the driving amount of the electric cylinder of the suction cups and the two rotation angles of two rotation axes at the end of the linkages are solved accurately. Based on the digital twin simulation method, the precise clamping motion of flexible fixture is calculated for an aircraft cockpit cover with a software developed by the authors in C++ language on the Visual studio platform. The distance between the clamping point and the surface was verified with a laser tracker. Finally, the practical experiment of a real cockpit cover clamping proves the practicability and effectiveness of the proposed method.

The final machining quality will be adversely affected when the workpiece position held in a fixture is not consistent with the expected position. Predicting and compensating for workpiece position errors can improve machining accuracy. However, most predicting methods neglect the effects of locating surface microtopography, surface profile error, and deviation of applied clamping force on workpiece position error, which will easily lead to a poor prediction result of the low-rigidity workpiece position. Therefore, a comprehensive position prediction model is developed to predict the position error of a large thin-walled box-shaped workpiece in the type of fixture with one locating surface and two pins, in which the above three error sources are considered. In this paper, the fractal geometry theory is used to identify the microtopography of the contact surface, and the equivalent stiffness between the fixture locating plane and the workpiece datum plane is estimated to get the relationship between the clamping force and the inclined angle of the workpiece caused by contact deformation. According to the obtained relationship, an estimation model based on the measured data of some key sampling points on the workpiece is presented to calculate the deviation between the machining surface and its nominal envelope surface. Finally, the proposed position prediction model is validated by the finite element simulation. The verification results show that the proposed method is effective and practicable, which can be used to predict and compensate for the machining position error of the low-rigidity workpiece.

Many mechanical parts used for various purposes, including medicine and information communication, have complicated and thin shapes owing to their functions and designs. To machine thin parts with high accuracy, it is necessary to reduce the cutting force induced on the workpiece or clamp the workpiece in an optimal manner. In this study, a support method capable of supporting the strength by using a magnetic elastomer is proposed. To test the effectiveness of the proposed support method, the use of the approach when applying a magnetic elastomer was compared with a method using a core, the low-melting point alloy, the low-melting point alloy and the elastomer. The effectiveness of the proposed method was clarified experimentally.

In this article, the effect of vibration and cooling media on the friction stir welding of 5083Al alloy is investigated. The vibration was introduced by the motor into the fixture inserted under the workpiece while a cooling media (water and lubrication oil) flowed into a canal in the fixture beneath the weld path. A constant rotation speed of 1250 r/min and a traveling speed of 90 mm/min were used for all the welding conditions. The thermal analysis measured by several thermocouples indicated that friction stir vibration welding (FSVW) provided maximum temperature distribution in the workpiece, while friction stir welding with the water cooling exhibited the lowest temperature value. The microstructure observations were conducted by optical microscope, scanning electron microscopy, and transmission electron microscopy. The results indicated substantial grain refinement when vibration and water cooling were simultaneously applied during the friction stir welding process. The hardness values increased from 50 to around 78 (Hv) for friction stir welding and FSVW with water systems, respectively. The joint efficiency (the ratio of the joint strength to the base metal strength) of the joint fabricated by FSVW with water cooling was around 87%, while this quantity was about 66% for the friction stir welding joint. Fracture analysis indicated more ductile behaviors for the samples fabricated by FSVW with the coolant systems. Furthermore, the joint fabricated by FSVW with water cooling exhibited the best wear resistance among all the samples in a pin-on-disk wear test.

Single-point incremental forming (SPIF) is a flexible and affordable process suitable for small-batch customized productions. Typically, metal alloys with a high strength-to-weight ratio exhibit a low formability at room temperature. The feasibility of conducting the SPIF process on these alloys at high temperatures is in demand. In this study, the SPIF process of the AA6061 aluminum alloy sheet at the temperature range of 25–400 °C is experimentally and numerically investigated. In this regard, a fixture was designed and fabricated to perform the SPIF process using heating cartridges for warming up the sheet metal homogenously. The effect of the temperature, the vertical pitch, the feed rate, and the lubrication type on the formability of the AA6061 sheet in SPIF of a truncated cone was studied. According to the results, by increasing the forming temperature from 25 to 400 °C, the formability of the truncated cone with the wall angle of 60° is improved by 528%. Moreover, using an appropriate combination of the process parameters, a truncated cone with a wall angle of 65° can be successfully formed up to the forming depth of 44 mm with a formability enhancement of 642% compared to the cold SPIF. For further understanding of the mechanics behind this improvement, the influence of the temperature on the formability was numerically studied. It was observed that the vertical pitch and the lubrication type have a significant interaction effect on the maximum achievable forming depth and the surface finish. It was also concluded that the effect of the feed rate on the formability is negligible for the considered range of the process parameters.

Purpose Acrylonitrile butadiene styrene (ABS), as a light and high strength thermoplastic polymer, has found extensive applications in different industries. Fused filament fabrication, known as three-dimensional (3D) printing technique is considered a rapid prototyping technique that is frequently applied for production of samples of ABS material. Therefore, the purpose of this study is to investigate the mechanical and fracture behavior of such materials and the techniques to improve such properties. Design/methodology/approach Experimental and numerical analyses have been conducted to investigate the effects of internal architecture and chopped carbon fiber (CF) fillers on the mechanical properties and mixed mode fracture behavior of the ABS samples made by 3D printing technique. Four different filling types at 70% filling ratios have been used to produce tensile and special fracture test samples with pure and CF filled ABS filaments (CF-ABS) using 3D process. A special fixture has been developed to apply mixed mode loading on fracture samples, and finite element analyses have been conducted to determine the geometric function of such samples at different loading angles. Findings It has been determined that the printing pattern has a significant effect on the mechanical properties of the sample. The addition of 15% CF to pure ABS resulted in a significant increase in tensile strength of 46.02% for line filling type and 15.04% for hexagon filling type. It has been determined that as the loading angle increases from 0° to 90°, the KIC value decreases. The addition of 15% CF increased the KIC values for hexagonal and line filling type by 64.14% and 12.5%, respectively. Originality/value The damage that will occur in ABS samples produced in 3D printers depends on the type, amount, filling speed, filling type, filling ratio, filling direction and mechanical properties of the additives. All these features are clearly dependent on the production method. Even if the same additive is used, the production method difference shows different microstructural parameters, especially different mechanical properties.

The paper analyzes the structure of technological fixtures for the positioning and fixing of large-sized thin-walled pyroceram shells as a factor affecting the dynamic characteristics of the grinding system. The solution to the problem of ensuring the dynamic stability of the «mandrel-workpiece» subsystem is necessary to increase the efficiency of shell machining in present conditions. Studying the vibrations frequency spectrum of the technological system during grinding has made it possible to determine their sources. The magnitude and frequency of vibrations depend on the mandrel structure - the clamping fixture. The study results are the requirements for a new mandrel structure, considering the dynamic stability of the technological system. Для забезпечення точності обробки та якості поверхні тонкостінних великогабаритних оболонок з ситалу на операціях алмазного шліфування необхідно підвищувати динамічну стійкість технологічної системи. На динамічну стійкість технологічної системи впливають як характеристики процесу різання, так і динамічні характеристики її елементів. Заготовка – тонкостінна оболонка є нетехнологічним елементом. Стінці заготовки не вистачає статичної жорсткості та динамічної стійкості під впливом на неї сил закріплення у пристосуванні та різання. Рівень коливань стінки оболонки під час обробки залежить від геометрії заготовки, режиму різання та конструкції технологічної оснастки – затискної оправки, яка впливає на власні коливання стінки заготовки. Складність забезпечення точності установки заготовки на операціях механічної обробки пов'язана з низькою точністю її базових поверхонь, похибками форми і розташування внутрішньої поверхні заготовки щодо зовнішньої. Дослідження частотного спектра коливань технологічної системи під час шліфування у виробничих умовах дозволило визначити джерела їх виникнення. Було виявлено, що нижча власна частота коливань підсистеми «оправка-заготовка» в діапазоні від 50 до 200 Гц негативно впливає на вимушені коливання в технологічній системі. Власна нижча частота оболонки (до 1000 Гц) впливає на появу та рівень параметричних коливань її стінки. За допомогою методів комп’ютерного моделювання виконано оцінку впливу існуючих та віртуальних, з необхідними ознаками, конструкцій пристосувань - оправок на рівень вібрацій у системі. Всього було оцінено чотири конструкції оправок та сім варіантів їх реалізації на операції зовнішнього шліфування тонкостінної оболонки. Дослідження показали, що в конструкції оправки, яка забезпечить динамічну стійкість технологічної системи і задану точність обробки, необхідно забезпечити: наявність двох опор для фіксації профілю заготовки оболонки по всій контактній поверхні без зазорів; базування по торцевій поверхні; наявність схеми установки заготовки, яка дозволить виконати обробку її повного профілю. Існуючі конструкції оправок повністю не задовольняють переліченим вимогам, тому є необхідність у розробці нової прогресивної конструкції оправки.

Today, an artificial tooth root called a dental implant is used to replace lost tooth function. Treatment with dental implants is considered an effective and safe method. However, in some cases, the use of dental implants had some failures. The success of dental implants is influenced by several biomechanical factors such as loading type, used material properties, shape and geometry of implants, quality and quantity of bone around implants, surgical method, lack of rapid and proper implant surface's integration with the jaw bone, etc. The main purpose of functional design is to investigate and control the stress distribution on dental implants to optimize their performance. Finite element analysis allows researchers to predict the stress distribution in the bone implant without the risk and cost of implant placement. In this study, the stresses created in the 3A.P.H.5 dental implant's titanium fixture and screw due to the change in abutment angles tolerance have been investigated. The results show that although the fixture and the screw's load and conditions are the same in different cases, the change of the abutment angle and the change in the stress amount also made a difference in the location of maximum stress. The 21-degree abutment puts the fixture in a more critical condition and increases the chance of early plasticization compared to other states. The results also showed that increasing the abutment angle to 24 degrees reduces the stress in the screw, but decreasing the angle to 21 degrees leads to increased screw stress and brings it closer to the fracture.

The surface residual stress significantly influences the performance of gears. The residual stresses of different grinding positions on the gear surface are different. Focusing on the gear profile grinding process, the residual stress distribution of gear tooth flank is investigated. To measure the residual stress of gear tooth accurately, a specific measurement method, including adjustment angle calculation model and alignment fixture, is carried out. The measured results with the proposed method are much better, and differences of residual stresses among measured positions are discussed. Then, considering the variation of chip geometry, a gear grinding model is proposed to analyze the residual stress distribution of gear tooth flank. The changing trend of the section area of the cutting chip calculated by the proposed grinding model matches the changing trend of measured results of the residual stress distribution. Finally, experiments are conducted, and the grinding model is verified from the perspective of cutting parameters.

Textural properties of a food not only influence consumers' sensory preference of the product but also more importantly influence the strategy of food oral manipulation. Availability of reliable instrumental techniques has always been sought by food industry for proper assessment of food texture both in lab and online quality control. In this work a set of ball back extrusion (BBE) geometries with various ball/cup diameters (38/40, 35/40, 31.5/40, 24.5/28, all in mm) have been assessed as a fixture of a standard texture analyzer for flowability and consistency test of fluid foods. The feasibility of the new design has been tested against plate back extrusion (PBE), a current standard, for a set of fluid food materials (3 near Newtonians and 2 non-Newtonians). Pressing force and apparent maximum stress were used to quantify the flowability of fluid materials. It was observed that both techniques were able to reflect the rheological nature of the samples and were able to distinguish flowability for both Newtonian and Non-Newtonian fluids. However, the new design shows advantages against the plate back extrusion with much improved stability. Results show that BBE could replace the conventional plate-back extrusion to evaluate the flow properties of fluid foods in an industrial environment. The geometries of 35/40 or 24.5/28 ball/cup diameters (aspect ratio 0.875) were shown to give most satisfactory performance. The device is specifically suitable for texture classification of fluid foods for dysphagia management.

Peel tests are frequently used to perform measurements of adhesive strength for pressure sensitive adhesive (PSA) tapes. Current lab methodologies for 90° peel tests translate the model substrate orthogonally to the peel direction in order to maintain the peel angle, precluding testing from immovable substrates. It was our objective to develop a peel fixture capable of testing temporary pavement marking (TPM) tapes and other PSA tapes from immovable substrates such as roadways surfaces. We present a modular peel fixture for conducting peel experiments directly on immovable substrates. The fixture was validated through a series of peel tests on consumer tapes to reproduce the linear width dependence and viscoelastic rate dependence found in traditional peeling setups. To test the capabilities of the fixture, a series of peel tests were conducted with various tapes on controlled surfaces, and a commercial tape on various immovable substrates. We demonstrate the ability of our fixture to reproduce results reported for traditional peel tests from literature. In addition, we were able to conduct peel tests directly on immovable substrates such as the benchtop. This fixture shows potential for both traditional peeling tests, and for use in in-situ peel experiments from substrates relevant to the end application of the PSA tape.

Tapping is one of the processes that most requires attention in the industry, due to the stage in which it occurs and its characteristics. In the case of tapping, it is common to use components and equipment with less rigidity, which compromises the dynamic behavior in several situations and can lead to process distortion or failure. The objective of this paper is to study the dynamic behavior of tapping in relation to several characteristics of the process. The dynamic behavior of the force signal was used to evaluate the process, varying the cutting parameters and the clamping system of the workpiece. The experimental results indicate that the floating system did not present a good dynamic behavior at high cutting speeds, this greater application of vibration is due to the resonance due to the combination of oscillations under forced and natural vibration. The natural frequency of the floating fixture system influenced the behavior of the axial forces. The increase in cutting speed resulted in a direct increase in the axial force vibrations as its frequency came close to the natural frequency of the system. Through dynamic analysis of the axial force signal observed the dynamic characteristics of the process and the machine tool. This allowed the dynamic evaluation of the system through the measurement of force signals generated in the threading process.

PurposeThis paper highlights a crucial public safety issue due to falling objects from tall residential buildings in Singapore. A systematic façade inspection regime and a system of evaluation of severity for the detection and assessment of potential falling objects from tall buildings are presented.Design/methodology/approachThe research uses qualitative case study approach with 450 tall residential buildings sampled for the study. The common materials, elements, components with high risk of falling objects, the nature and type of the falling, the critical factors affecting the falling, the respective level of severity, and the effectiveness of various diagnostic techniques and protocols, are summarised.FindingsFaçade for tall residential buildings in Singapore comprises mainly cementitious materials cast in situ or precast, with fixtures and architectural features, all of which have potential of falling. The common anomalies arising from each material and fixture/features are identified, the causes evaluated and their implications to future design, construction and maintenance analysed.Originality/valueThis study provides original and significant information to a crucial public safety issue, setting design and construction criteria that will serve as a benchmark for new and existing facades, applicable to all cities dominated by tall buildings. The paper presents original figures, checklists and guides as a basis for readers' consideration to use according to their respective unique conditions.

Minimally invasive surgery has become the primary treatment of spine disease. It depends on high-precision medical image as guidance. Ultrasound imaging is expected to replace X-ray fluoroscopy as a golden standard scheme of minimally invasive spinal surgeries. Researchers make effort to develop ultrasound imaging for the process of navigation, taking its distinctive advantages of user-friendly and radiation-free. However, it is greatly affected by the contact force and incident angle of the probe, which depends a lot on experienced sonographers. To this end, a flexible ultrasound scanning system (FUSS) is proposed to automatically image the human spine. In mechanics, a flexible fixture, fixed on the end joint of robotic arm, is designed to ensure the ultrasound probe to be pressed against the dorsal skin. Besides, decoupled control strategy is presented which decouples trajectory planning task and force control task into separate joint space. By this means, the possibility of accidental damage could be minimized. Phantom experiments were carried out to validate the hysteresis characteristic of flexible fixture, the capacity to resisting impact, the performance of control system and the quality of reconstruction image. These results show that our system has high safety performance and could keep the probe force stable within the range of 1 N to obtain better reconstruction image than freehand scanning. In summary, it has a great potential on navigation of spine surgery.

Measuring and evaluating the geometric error of a linear axis periodically, is an essential operation in the day-to-day usage of a machine tool. In this paper, a system consisting of a novel one-dimension probe and a ball array is developed to fast estimate the geometric error a linear axis from the ball center deviations in three dimensions. The proposed 1D probe is assembled by an inductance micrometer and a simple fixture. Five measuring positions on the ball surface are selected to recognize the ball center offset caused by the geometric error. Then, an identification model is established to recognize the error at the ball center in the array. Moreover, a correction method is proposed to eliminate the installation error. It applies the least square method to form the virtual baseline by the measured ball centers, in order to eliminate the effect that resulted from the inaccuracy and the misalignment of the ball array during the manufacturing and setting, respectively. Then, the remaining part of the measured results is applied to evaluate the geometric error of the measured linear axis, including one positioning error and two straightness errors. Finally, a prototype system is developed to verify the correctness of the proposed 1D probe, while a measurement experiment is conducted on a machining center to verify the validity of the proposed method. The results indicate that the maximum absolute error among one positioning error and two straightness errors reach to 2.1 μm, 2.3 μm, and 1.6 μm, respectively, while the root mean square error, and the average absolute error are no more than 2.0 μm, when comparing with the results from the laser interferometer.

In order to decorate the night view for cities, installing lighting fixtures on stay cables of existing cable-stayed bridges is an effective choice, but the aerodynamic characteristics of the stay cables will change significantly. This paper presents a study on the galloping stability of the stay cables equipped with lighting fixtures. The static aerodynamic coefficients were computed using computational fluid dynamics (CFD) simulations, and the reason for the negative slope of the lift coefficient was discussed based on the changes in pressure distributions and flow field characteristics. Wind tunnel tests were further carried out to verify the numerical results. The possible galloping instability intervals for the stay cables with lighting fixtures were calculated. The results show that the existence of lighting fixtures has significant effects on the aerodynamic performance of stay cables. The slope of the lift coefficient becomes negative within several intervals of angles of attack, which indicates the possible galloping instability. The sudden decrease in the lift coefficient is mainly related to the vortex which covers the concave between the lighting fixture and the stay cable and makes the separated flow cannot reattach.

With the miniaturization of the components, micro-fabrication has gained significant attention for the application in micro-devices. The current work aims to weld dissimilar austenitic stainless steels with different thickness (average ~ 700 µm) by downscaling the traditional arc-based joining process. Micro-plasma arc welding (µ-PAW) with less than 15 A current is used to fabricate the weld joints at different heat input, which can be reviewed as a substitute for laser and electron beam welding process in terms of cost-effectiveness. The welding fixture employed to hold the small workpiece contributes significantly to achieve the complete establishment of the µ-PAW process. A low amount of heat input leads to reduced dendritic and secondary dendritic arm spacing, which increases the joint efficiency up to ~ 115%. A high value of heat input changes the mode of failure from ductile to mixed mode due to micro/macro-voids’ existence, decreases the corrosion resistance due to chromium depletion from 25 to 17 wt.%, and increases the number and size of the pores. A finite element-based computational model is also employed to presume the geometrical dimensions of the weld joint that agree well with the experimentally determined values with a maximum error of 9%.

The molybdenum cup and molybdenum pin, which are the main materials of the molybdenum electrode used for the LCD BLU CCFL electrode, have not been developed in Korea and imported from Japan. In this paper, especially, research on prototype manufacturing and CAE analysis is performed to develop a molybdenum pin. In this research, to develop the manufacturing technology of molybdenum pin used for CCFL electrode of LCD BLU, development of linear processing technology, development of molybdenum wire surface treatment technology, development of wire cutting technology, production of molybdenum pin, design and fabrication of JIG and Fixture for inspection, molybdenum pin prototyping and analysis, and development of 100% molybdenum pin inspection technology. The development of molybdenum pins developed through this research can overcome Japan's technological level, which depends entirely on imports from Japan, and it is thought that the development will have a significant impact on the overall industry using molybdenum pins.

Purpose Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density. Design/methodology/approach Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser. Findings Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field. Originality/value A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.

Fixture design is one of the main factors which affect the final product quality. Proper design of fixture plays an important role in ensuring the required tolerance of the product. Proper placement of locators is one of the prominent factors in fixture design. Locators are elastic: they deform under clamping and machining forces causing rigid body displacement of the workpiece which in turn affects the part quality. In this article, a 3-2-1 type of fixturing system having elastic locators around a considerably rigid rectangular workpiece is considered. A genetic algorithm is proposed, which uses a fitness function that evaluates the positioning error of the workpiece under external forces and torque. Among several variables, 12 variables, which define the placement of locators, are chosen to be optimized while minimizing the positioning error of the workpiece at the point of action of machining force. The proposed algorithm optimizes the 12 interlinked variables, within the specified region, for machining force and torque at a single point. However, when the cutting tool moves to any other point on the workpiece, it is observed that either the workpiece loses its contact with any one of the locators or the positioning error increases by a large value. To overcome this issue, the proposed algorithm is further modified for placement optimization to cater for multi-point machining, and the isostatism of the workpiece is ensured by checking the magnitude and direction of displacement (of what?) at each point of workpiece-locator contact. Finally, the original and modified GA algorithms are explained through a case study where the single point optimized placement shows loss of contact when machining force is applied at other points. The placement optimized from the modified algorithm shows that the isostatism of the workpiece remains intact while all four positioning errors are converged towards the same value. The results obtained from the proposed and modified algorithm are verified using ANSYS simulation.

The determination of mechanical and fracture properties of anisotropic tubular materials along hoop direction needs the use of the ring hoop tensile test, for which, the obtained results are deceived by the effect of friction between the ring sample and the D-shaped block mandrel. Commonly, lubricants are applied to reduce the friction, which are inefficient in some specific cases; despite of that, it was noticed that scarce works have focused on the development of new mechanical mandrel designs or trying to improve the current ones to resolve the friction concern. The aim of this research is to correctly address the friction issue between the ring sample and the fixture mandrel to significantly reduce its effect on the ring hoop tensile test results without using any kind of lubricants. New mechanical design of D-shaped block mandrels are developed to carry out ring hoop tensile tests to simply characterize the mechanical behaviour of tubular materials. New mechanical D-shaped block mandrels were designed, manufactured and used to carry out experimental ring hoop tensile tests. An inverse identification method based on an artificial neural network trained by finite element simulation responses, was developed to efficiently segregate the flow stress curve from the influence of the friction, inherent in the global force-displacement curve for the classical ring hoop tensile test. The experimental force – displacement curves using five mandrel-types are established and quantitatively compared on the base of their ability to reduce the friction issue. The analysis of the finite element simulations, related to the investigation of the influence of the friction on the ring hoop tensile test results, shows that one of the new developed mandrels reduces the friction coefficient by about 10 times compared to that identified using the classical D-shaped block mandrel. It has been found that, the finite element simulation of ring hoop tensile test using the identified material parameters matches the experimental results. This investigation provides a useful fixture mandrel, which is able to drastically reduce the friction without resort to any lubricants to just determine the material flow stress curve using ring hoop tensile test, regardless the friction level between the sample and mandrel.