Clamping Force Research Articles

Research on Anchorage of GFRP Anchor Bolts and Heads

GFRP is an abbreviation of Glass Fiber Reinforced Polymer. It is an inorganic non-metallic material made of glass fiber reinforced material, synthetic resin as matrix material, and compounded by a certain process. Although the glass fiber reinforced polymer anchor can fundamentally solve the problem of poor corrosion resistance of the steel bar anchor, in the anchor system, the force on the surface layer or the waist beam needs to be transmitted to the shaft through the anchor head. At present, the pull-out strength of domestic GFRP anchors is far away from the tensile strength of GFRP tendons. This may cause the anchorage system of anchors to fail due to anchorage failure, and the tensile strength of GFRP tendons cannot be fully exerted. When ordinary clip-type anchorages are used, there is a huge clamping force on the ribs in the anchorage zone, which may result in the shear failure of ribs.Based on this, this article uses a high-strength impregnated reinforcement material to carry out the tensile failure test of a GFRP anchored anchorage with a diameter of 18cm. The study found that the use of high-strength reinforced concrete can make the GFRP anchor achieve the maximum tensile strength, and with the increase of curing time, the ability of the high-strength reinforcement to limit the displacement of the anchorage end is stronger.

The Structural Design of a High-Performance WBD Brake Disc

ABSTRACT A high performance, newly-developed wire-woven bulk diamond (WBD) ventilated brake disc is introduced to reduce the operating temperatures and mass of conventional brake discs. The use of the highly porous material requires a deeper understanding of the mechanical stresses developed within a brake disc to be developed to improve the disc core strength to withstand the high stresses developed during braking. In this study, experimentally determined solid brake disc stress distribution results, separated into the compressive stresses due to the pad clamping force and the shear stresses due to the applied brake torque, were applied to the reinforcement ofthe WBD core brake disc. The analysis was based on the maximum predicted deceleration conditions of a medium sized truck (Mercedes-Benz Atego). While the WBD core material possessed sufficient strength to withstand the shearing due to the braking torque, the pad clamping load was predicted to cause disc failure. Consequently, straight radial ribs were designed to reinforce the ventilated core, with final rib dimensions of 74x14x2.5 mm, manufactured from mild steel (SAE1006). A total of 10 ribs at 36° intervals were added to reinforce the core, increasing the mass by 0.20 kg compared to the original disc. The newly reinforced WBD brake disc remains lighter than a commercially available pin-finned disc, and is expected to maintain superior thermal performance while possessing the required mechanical strength. Additional keywords: Ventilated disc, mechanical stresses, braking, stress distribution

A study of clamp force detection error in bolt/nut assemblies

A study of clamp force detection error in bolt/nut assemblies

구조파를 이용한 볼트부 축력 비파괴측정 시스템 연구

구조파를 이용한 볼트부 축력 비파괴측정 시스템 연구

Котки різних конструкцій. Інженерний аналіз

Comparative field tests of similar in design ring-spur and gear-spur rollers for soil rolling provide their developers and users with information on the understanding of the design and technological features. The Goal of research – engineering analysis of structures of ring-spur and gear-spur rollers according to the criteria of weight, shape of working surfaces, soil pressure, completeness of compaction, penetrating ability in the range of depth of pre-sowing and surface tillage. Methods and Materials. Engineering analysis involved the study of three types of rollers. The research hypothesis assumed that the combination of weight characteristics of rollers and their geometric shapes of working surfaces in contact with the soil, in statics will provide the inherent properties of each cat (the first stage of research), which will potentially focus on choosing the most acceptable criteria for comparing functional features of rollers. necessary for field research in dynamics (the second stage of research). According to the criteria of static research were selected: penetrating ability (1); soil pressure (2); completeness of compaction of the area (3); direction of clamping forces (4); features of working surfaces (5); the nature of the mounting of solid disks on the shaft (6). Methodologically, the first three criteria required special adaptations (capacities) with the ability to change the height of the soil layer in the range of depths of pre-sowing and sowing tillage. Other criteria were supposed to be carried out by organoleptic evaluation. The study was supposed to be carried out on soil characteristic of the Forest-Steppe zone and homogeneous in fractional composition, to exclude the influence of soil inclusions of different sizes. Evaluation of soil characteristics was performed by thermostatic-weight method, according to the generally accepted method of "cutting ring" [Kaczynski, 1947] with a cylinder volume of 100 cm3. To determine the area of one elementary working surface of the annular disk, the application of a marking grid on its imprint on the surface left in the soil layers hmin, hmid, hmax was used. When determining the pressure on the soil, depending on the height of the treated layer, the marking grid was superimposed on the imprint of several areas of elementary working surfaces, which were fixed on the chord of immersion in the soil of the annular segment. Statistical analysis of experimental data was performed by the method of analysis of variance according to [Dospekhov, 1985] and interpreted by standard computer programs Excel and graphs. Results. According to the physical characteristics (weight and geometric parameters) of the roller combines the proximity of the diameter of the disks, the width of the working surfaces on the edge of the generator, the presence of spurs. The difference lies in the dimensional characteristics that fall on the width of the grip, the presence of aggressive protruding shapes (teeth) in the gear-spur structure. Each roller has an individual layout of elementary work surfaces. This allowed the conditional marking of rollers as "classic", "modernized" and "specialized". The working surfaces of the classic and specialized rollers provide vertical and lateral action of the clamping forces, while the modernized forms them in the vertical direction. These forces for each of the rollers are derived from the orientation of the working surfaces of different configurations (flat narrow, flat wide; a combination of point-focused with trapezoidal). In addition, work surfaces can have a one- or two-level sequence of contact with the soil at a variable depth. It is established that the nature of the attachment of adjacent disks on the shaft can be rigid or movable. Definitions of concepts and their estimation on indicators of pressure, completeness of consolidation, penetrating ability are resulted. Conclusions. According to the indicators of engineering analysis, each of the three rollers is predicted to have its inherent dominant feature for the most effective use in milling, pre-sowing and post-sowing tillage operations. It is determined that the most acceptable criteria for further research in the dynamics of variable speed should be the intensity of crushing lumps, the degree of soil compaction, the intensity of soil compaction, sticking of the working surface of the roller in high humidity, self-cleaning ability. The criteria of further research in dynamics are determined.

Residual Clamping Force for Corroded Tension-Control Bolts

AbstractThis study investigated the residual clamping force for corroded tension-control bolts and the effect of each part on force reduction. A finite-element analysis revealed that bolt head sect...

단슬롯 너트의 형상이 풀림방지 성능에 미치는 영향

In this study, the effect of a single-slot nut’s shape on the anti-loosening performance was investigated. The tightening characteristics of the single-slot nut were analytically estimated. Nonlinear finite element analyses were subsequently conducted for determining the tightening torque corresponding to various values of the slot depth, upper height, and bottom slope. Furthermore, the obtained numerical results were validated by employing a test-rig with a torque wrench and a washer-type load cell. It is found that compared to a normal nut, the tightening torque of the single-slot nut increases by a maximum of 20% at a given clamping force. Additionally, it is observed that the bottom slope is the dominant factor affecting tightening; increasing the bottom slope causes improvement in the tightening torque and the anti-loosening performance.

Optimising open and closed cooling time for hybrid injection moulding of polypropylene with polyamide inserts from multi jet fusion

ABSTRACT To reduce the lead time and costs for developing short run production injection moulding tools the potential of additive manufactured mould inserts is investigated. These hybrid moulds are compared to conventional steel-based moulds, considering mechanical and thermal differences. For part production and insert material, respectively polypropylene and polyamide12 manufactured by Multi Jet Fusion (MJF) are chosen. Moldex3D simulation results show that lower clamping forces and injection pressures are sufficient upon using MJF inserts due to a 20 times lower thermal diffusivity compared to conventional steel, resulting in thinner skin layers and increased solidification times. Practical injection moulding parameters have been optimized by reducing the cooling time with 75 seconds (60%) using forced convectional cooling at 15 °C. Core and cavity inserts show a deviating cooling behaviour linked to the higher amount of insert material and presence of steel. The wear of the mould inserts is minor after producing 360 parts. .

Importance of performance certification for post-installed anchors: An experimental assessment

This study evaluates the pullout performance of ETA-approved and non-ETA-approved post-installed bonded and mechanical torque-controlled expansion anchors found in the Middle East region, and draws conclusions on the role of such performance certifications on ensuring the safe operation of the anchors under various installation and site conditions. Both, the bonded anchors and mechanical expansion anchors were studied with a total of 106 tests, including tests in cracked concrete and elevated temperatures of 60 °C. Results found that ETA-approved anchors retained a larger portion of their reference strength and were more robust at suboptimal site conditions. Non-approved bonded anchors retained just 24% of their reference strength under the common scenario of workers neglecting the cleaning of the drilled holes. Bulk bonding adhesives manually mixed by the user could have critical results if the mixing ratio is not strictly followed and the non-approved mechanical anchors lacked sufficient instructions, had a lower build quality, and could not generate a sufficient clamping force regardless of installation torque.

Microstructure and properties of solid state joints of titanium sheets produced by ultrasonic welding

The results of the study on the microstructure and properties of solid state joints of titanium sheets obtained by ultrasonic welding (USW) with frequency 20 kHz and vibration amplitude 20 μm during 2 and 3 s under a 6 kN clamping force are presented. The thermo-mechanically affected zone is observed along the defect-free weld line (joint). It was found that the length and width of this zone increased with the welding time. In the thermo-mechanically affected zone, a significant grain growth takes place, a change in the texture is observed and maxima near 60° and 90° in the grain boundary misorientation distributions appear. The maximum lap shear failure load of the joints obtained by USW of 2 and 3 s durations are 1998±122 and 2506±226 N, respectively. There is a change in the failure mode from interface debonding after 2 s USW to nugget pull-out for the welding time of 3 s.

A real‐time clamping force measurement eigenvalue for prediction, adjustment, and control of injection product quality

AbstractClamping force is a crucial parameter in injection molding. Improper clamping force setting can result in poor product quality and shorter machine lifespan. The objective of this study was to establish an eigenvalue‐injection clamping force peak value by real‐time clamping force measurement with strain gage sensor for prediction, adjustment, and control of injection product quality. In this study, computer‐aided engineering (CAE) structural analysis technique was used to analyze and verify the points of measurement of the sensor. Next, the molded product was conducted using the following injection molding parameters: V/P switchover point, clamping force, injection speed, melt temperature, mold temperature, packing pressure, and packing time. The relationship between injection clamping force peak value and product quality were examined. The results showed that CAE analysis could successfully predict and provide suitable points for sensor measurement. Comparison of analysis and experiment results revealed that injection clamping force peak value and part weight exhibited identical trends. Finally, the injection clamping force peak value not only could it successfully predict product quality, but also it would achieve the purpose of optimizing and stabilizing the clamping force and part weight.

Experimental and numerical optimization of process parameters for thin wall machining of bearing housings

Bearing Housing is the critical part in Air end assembly of Screw compressor, because it determines the Discharge end clearance (DEC) which in term determine the volumetric and adiabatic efficiency. For setting a DEC in air end assembly, it is important to maintain the shoulder thickness of bearing housing within close tolerance of 10 µm. If not maintained so, metallic shim to be added in assembly process to maintain the clearance. Metallic shim selection for each assembly involves iteration method which is time consuming process. However due to machining constraint the current tolerance which achieved is 100 µm but the requirement is 10microns. If the improvement is done to achieve the required tolerance, DEC setting time can be reduced by eliminating iteration shim setting process. The aim of this project is to achieve the linear & Geometric dimensions within deserved critical tolerance in milling thin wall areas of housings in CNC milling machine by optimizing the process parameters using Design of experiments (DOE) and Finite element analysis (FEA). DOE with cutting parameters using Response surface modeling (RSM) with face centered design is used to obtain the significance level of Cutting speed, feed and Depth of cut. Optimize the tool cutting parameters to minimize the tool and part deflection during machining. FEA is used to reach the optimum clamping area and force to minimize the part deflection & deformation.

Clamping force integrated computer aided tolerancing in composite assembly

Traditional computer aided tolerancing method could not accomplish the tolerancing and variation simulation well in composite assembly. The paper presents a clamping force integrated computer aided tolerancing method for composite assembly. The stochastic variations and the stackup of variations are affected by clamping forces. The clamping force modified probability distribution is used to represent the modification based on the verified FEA model of the composite assembly. The clamping forces are coordinated based on the main deformation mode extracted by the principal component analysis to satisfy the coaxial tolerance requirements of the composite assembly. The assembly of an aircraft composite elevator is considered to illustrate the computational aspects of the proposed methods. The computer aided tolerancing method involving clamping forces outlined in the paper is found to be effective for composite assembly.

A simulation-based approach for assessment of injection moulded part quality made of recycled olefins

To produce plastic parts of high geometrical quality and dimensional stability through injection moulding process there are several key variables that must be considered. These include processing parameters such as packing time, cooling time, packing pressure, melt temperature, mould temperature and the intrinsic melt flow characteristics of polymeric materials used to produce the part. The challenge of producing high quality part is further compounded if the input polymer material is of reclaimed waste streams with inherent inconsistency in their nature. In this work, significant number of simulation-based studies are conducted using Autodesk Moldflow software to delineate the contributing issues pertinent to the part quality and achieve topological optimization by reducing critical parameters of shrinkage and warpage while ensuring overall cycle time viable for industrial production rates. Key simulation variables were obtained through experimental characterization of flow and thermal properties of the recycled olefin plastics. Different gate locations were simulated, and the best gate locations were selected for a two-gate system. These gates were provided with gate valve controllers for controlling the polymer flow to create cascaded injection moulding scenarios. Such scenarios were iterated with the objective of reducing the pressure required for cavity filling and thereby reducing the clamp force required. Optimized melt and mold temperatures of 245 °C, 20 °C were used for all the simulations performed. The result obtained from the most optimized simulation showed an average cycle time of 10.42 secs, volumetric shrinkage of 5.08%, warpage of 1.05 mm and clamp force of 79.81 tonne would be required to produce a part of 200 mm*100 mm*1.5 mm dimensions. Following a cascaded injection setup, it was shown that the clamp force could be reduced by 60.57%.

Fatigue tests and calibrated fracture mechanics approach for historical riveted steel girders

For historical riveted steel railway bridges fatigue assessment and calculation of the remaining fatigue life based on SN-curves is a big challenge, due to missing traffic data of the past and often unsatisfactory conservative results (no remaining fatigue life, but no fatigue cracks detected). As an alternative, a fracture mechanics approach based on the assumption of an initial crack length and an analysis of the stable crack growth behaviour seems helpful.Within a research project, four dismounted girders of the carriageway of an old steel lattice girder bridge (year of construction: 1908, end of service life: 2018) were used for specific fatigue tests in the laboratory. Starting from artificial notches, initial cracks at the critical positions at the rivet holes of riveted girders were induced and the development of the crack fronts was measured, simulating rivets with and without clamping force. First, the scope and execution of these fatigue tests are presented in the paper, completed by a comprehensive evaluation of the development of the crack fronts. Then a simple fracture mechanics model is presented and calibrated based on the test data. With this model the remaining fatigue life of riveted girders, with high fatigue pre-damage, can be determined for the borderline cases either without or with high clamping forces in the rivets.

Axial load distribution and self-loosening behavior of bolted joints subjected to torsional excitation

Axial load distribution and self-loosening behavior of bolted joints were numerically studied in this work. Finite element (FE) models with fine mesh threads were generated by analyzing the clearance of different thread fit qualities and thread profiles of MJ and Spiralock internal threads. By changing the thread clearance value, thread profile, engagement length, pitch value, and friction coefficients, their effects on axial load distribution, loosening behavior, and the dynamic response of bolted joints were explored with accurate three-dimensional FE models. In addition, experiments were conducted to investigate the dynamic response of bolted structures. Numerical results agreed with the theoretical results. For varying friction coefficients between the contact threads and between the bolt head and the bearing surfaces, the clamping force of bolted joints excited by torsional load changed in three cases: continuously decreasing, initially decreasing and then remaining constant, and initially decreasing and then fluctuating. Agreement was achieved by comparing between hysteresis loops generated by numerical and experimental methods.

Static and fatigue behaviours of a bolted GFRP/steel double lap joint

To provide a safe and reliable connection using bolts for glass fibre-reinforced polymer (GFRP)/metal hybrid structures in civil engineering, the static and fatigue behaviours of a bolted GFRP/steel double-lap joint (DLJ) with a clamping force of 10 N m were investigated experimentally under monotonic tensile loading and repetitive tensile loading with a load ratio of R = 0.1, respectively. The dominant failure modes, fatigue life and stiffness degradation law were obtained for the bolted DLJ. The fatigue damage evolution of the bolted DLJ was also clarified. The F–N curve and a non-linear stiffness degradation model were obtained from the experimental results for the bolted GFRP/steel DLJ. Finally, a comparison between the fatigue behaviour of the bolted GFRP/steel DLJ and that of a GFRP/GFRP DLJ was performed to identify the differences. The results indicated that the stiffness degradation law of the bolted GFRP/steel DLJ could be accurately characterized by the non-linear stiffness degradation model. The GFRP/steel DLJ exhibited a longer fatigue life than the GFRP/GFRP DLJ because the compressive stresses in the inner surface of the bolt-hole of the outer GFRP laminates were much smaller in the bolted GFRP/GFRP joint than the bolted GFRP/GFPR DLJ under the same applied maximum load. The stiffness degradation rate of the GFRP/steel DLJ under fatigue loading was almost the same as that of the GFRP/GFRP DLJ during their service lives.

Experimental Investigation of Hysteretic Performance of Self-Centering Glulam Beam-to-Column Joint with Friction Dampers

In this study, friction dampers (FDs) were placed at the top and bottom of a post-tensioned (PT) self-centering glulam (SCG) beam-to-column joint to dissipate earthquake energy. PT tendons were installed in two externally elongated slots at the centroid of the beam to provide the system with self-centering capacity so that the system can return to its original position after an earthquake. Theoretical and experimental analyses of the beam-to-column joint were performed to investigate the effects of various design parameters, such as the total clamping forces applied to the FDs and initial forces of the PT tendons, on the hysteretic performance of the FD-SCG joint under cyclic loading. During the tests, the backbone members (glulam beam and column) and main connecting members (PT tendons and FDs) were measured to always be within the elastic limit range. Both the theoretical and experimental results indicated that under low initial PT forces and clamping forces, the energy is dissipated primarily by FDs; in contrast, under high PT forces and clamping forces, some energy is dissipated by the glulam materials, owing to the occurrence of minor local damage in the specimen, in the direction perpendicular to the grain. Moreover, the FD-SCG joint can be suitably designed to achieve the desired stiffness, load capacity, self-centering ability, energy dissipation capability, and expected overall system response.

Functional Safety for Developing of Mechatronic Systems - Electric Parking Brake Case Study

The electric parking brake (EPB) system as the complex mechatronic system consists of the actuators that generate the clamping force necessary to hold the vehicle safe, the conventional calipers that convert clamp force into brake torque, electronic hardware with the Electronic Control Unit (ECU), cable harness and switches and especially the control software providing the functions that the driver will experience. Like most of the modern automotive components, the EPB is equipped with embedded electronic systems that include ECU, electronic sensors, signals, bus systems, and coding. Due to the complex application in electrical, electronics and programmable electronics, the need to carry out detailed safety analyses that are focused on the potential risk of malfunction is crucial for automotive systems. This paper describes a possible division of the EPB sub-functions between the supplier the wheel brakes and the supplier which supplying the ECU. Functional safety must be a guarantee with concerning the overall vehicle system. Functional safety is according to the requirements of the ISO 26262 standard and in the context of this paper relates solely to the E/E components (electrical and/or electronic) of the EPB. This paper covers the hazard analysis and risk assessment relevant to the EPB control software, and the derived allocation of ASIL risk levels to the EPB software elements of the functional architecture of the EPB.

FEATURES OF HIGH-SPEED THE SUPER-FINISHING DISCS CERAMIC

The possibility of providing high performance of super-finishing of ceramics based on the analysis of the processes of super-finishing of metal products is proved. For conducting experimental studies, a special installation has been developed, including a sharpening machine and a device for superfinishing. For such processing conditions, the necessity of using a low-rigidity technological system is justified. Discs made of ceramic materials of various machinability with diamond bars were super-finished at a cutting speed of up to 9.1 m/s and a clamping force of up to 90 N. Experimental data on the change in the value of cut allowance on the duration of treatment, the impact speed super-finishing of ceramic disks and grit sizes of diamond bars on the magnitude and rate of stock removal, roughness and waviness of machined surfaces and consumption of the tool. The results of super finishing of ceramic materials with processing of metal products are compared.