Fastening Force Research Articles

Determination of the best distribution and effective interval using statistical characterization of uncertain variables

Abstract In this paper, an algorithm for estimating the best distribution about data containing uncertainties is proposed. The proposed algorithm combines sequence statistical modeling (SSM) and a method for determining the minimum experimental data. SSM is a method for selecting the best distribution about data using a goodness of fit (GoF) test and a comparison of the likelihood. The method used to determine the minimum experimental data determines the minimum data needed to an estimate the best distribution. The SSM presented herein is a method for selecting a suitable data distribution when considering only a parametric distribution. Thus, in this paper, the SSM was improved in order to select the correct distribution of both parametric and non-parametric distributions simultaneously. In addition, with the existing method for determining the minimum data, the data should be added based on actual experiments when the results data show an insufficient number, and there is a limitation in that the designers cannot broadly identify the data required. To overcome this limitation, SSM and random sampling are applied to the method to determine the minimum data, and thereby, ensure that the designer knows the approximate minimum data needed. To verify the validity of the proposed algorithm, it was applied to a real world case study on determining multiple statistical parameters in the bolt fastening problem. The sequence of verification methods used is as follows: First, the best distribution of the bearing surface and thread friction coefficient estimated by the proposed algorithm and based on a normal distribution are selected as comparison targets. Second, the bearing surface and thread friction coefficient data are sampled within the 95% confidence interval of the two distributions. Third, the reliability of the sampled friction coefficient data are compared using a Monte-Carlo simulation and an equation to calculate the bolt fastening force. In this study, the effectiveness of the proposed algorithm is validated. Highlights The algorithm to determine appropriate probability distribution of data is proposed. The sequential statistical modeling is improved to consider both parametric and non-parametric distribution. The method to determine minimum data is improved to verify sufficiency of data without actual experiments. The effectiveness and validation of the proposed algorithm is verified using the bolt-fastening data.

Design of utility tools and their application for testing mechanical properties of metallic materials

This paper deals with the design of a series of tools which could assist the preparation of samples, the positioning and the measurement to resolve the problems that exist in mechanical properties testing. In order to decrease the operational difficulty and improve the quality of preparation, two kinds of fixtures are made to clamp the hardness sample and be used to grind or polish by the grinder. For the measurement of percentage elongation after fracture and percent reduction of area, a special device is assembled to quickly splice the fractured test pieces. By applying a single transverse fastening force, the efficiency of splicing of the test pieces can be increased substantially and it provides enough operation space for the vernier caliper. To raise the placing efficiency and avoid the dragging of Charpy impact test piece, a special gripping plier is designed to ensure the coincidence of the plane of symmetry of the notch and the swing plane of the striker. By using the supports of testing machine and separating the function of alignment and fixation, the new structure resolves the matters of existing method as unsatisfied placing effect or dragging of the test piece. In order to accurately install the fixtures of electro-hydraulic servo fatigue test system, a set of positioning brackets and plate tool are made to adjust the location of the large base and check the deflection between the fixtures.

Noninvasive blood pressure monitor using strain gauges, a fastening band, and a wrist elasticity model

This paper proposes a novel continuous noninvasive blood pressure estimation method that is based on the variation of wrist skin strain occurring with changes in diastolic and systolic blood pressure. The wrist elasticity model used to estimate blood pressure was constructed according to an ultrasonic probe indentation method used for measuring and calculating the thicknesses and material properties of skin layers. The strain value of the wrist skin was measured using a dual strain sensor to avoid temperature drift. The dual strain sensor was fabricated using a screen-printing process on a polyimide film. To cause the dual strain sensor to indent the skin for ascertaining the depth to measure skin strain, the wristband is driven by a compact ultrasonic linear motor consisting of a piezoelectric slab and a flap clip. The compact ultrasonic linear motor provides an adequate driving distance, which was estimated using the energy method, and a constant holding force used for strain measurement without input power. In blood pressure measurement experiments performed with 30 subjects, the estimation mean error against a validated cuff-type blood pressure monitor was 1.6mmHg at rest for diastolic pressure. The error increased when the subjects exercised, but returned to near the rest value when the subjects rested after exercise. These results showed that the noninvasive blood pressure monitor can estimate blood pressure with a small fastening force. This device can be used for bedridden patients who require continuous blood pressure monitoring.

Fastener Demands for Sheathing-Braced Cold-Formed Steel Stud Gravity Walls

We explore, in this paper, the demands and behavior on fasteners supplying sheathing-based bracing of gravity loaded cold-formed studs and wall assemblies. The studies are carried out by shell finite element (FE) models, which are compared to analytical solutions and previously completed laboratory tests conducted by the authors. The connection between the sheathing and the stud should be able to develop enough resistance to restrain global buckling of the studs; therefore, special attention has to be given to the demands on these connections for design. Local buckling and stress concentrations may damage some connections and redistribution of forces should be ensured. Classical practice for determining fastener demand - i.e., the 2% rule - may be deficient. An analytical method developed for determining fastener demand is compared to the FE models presented in this paper; the analytical method results in a reasonable prediction of the fastener forces in wall studs.

Study of CAD & Processing Error for End-Gear with Arc Tooth

This paper presents methods for determining the basic geometry of end-gear with arc tooth external diameter, width of tooth, end module, number of teeth, pressure angle, tooth, tooth clearance parameters; at the same time gives the tooth bearing strength calculation method, and the formulas to calculate the tooth shear stress, surface stress and bolt fastening force of equivalent stress is established; finally write the software error simulation analysis.

Finite element modeling of mechanically fastened composite-aluminum joints in aircraft structures

A three-dimensional, solid finite element model of a composite-aluminum single-lap bolted joint with a countersunk titanium fastener is developed. The model includes progressive damage behavior of the composite and a plasticity model for the metals. The response to static loading is compared to experimental results from the literature. It is shown that the model predicts the initiation and the development of the damage well, up to failure load. The model is used to evaluate the local force–displacement responses of a number of single-lap joints installed in a hybrid composite-aluminum wing-like structure. A structural model is made where the fasteners are represented by two-node connector elements which are assigned the force–displacement characteristics determined by local models. The behavior of the wing box is simulated for bending and twisting loads applied together with an increased temperature and the distribution of fastener forces and the progressive fastener failure is studied. It is shown that the fastener forces caused by the temperature difference are of significant magnitude and should be taken into account in the design of hybrid aircraft structures. It is concluded that, the account of the non-linear response of the joints results in a less conservative load distribution at ultimate failure load.

특수가스용기용 밸브의 안전성에 관한 실험적 연구

본 연구에서는 특수가스용기용 밸브의 안전성에 관한 실험적 연구를 수행하였다. 시험용 밸브는 특수가스용기에 부착되었던 것을 무작위로 수거한 것으로 가스누출 및 작동 안전성에 대한 시험을 실시하였다. 실험결과에 의하면, 밸브의 몸체, 나사 체결부, 안전판, 방출구, 스템부, 핸들에서 가스누출 안전성에 영향을 미칠 정도의 크랙, 마모, 부식, 변형이 발생하지 않았다. 다만, 핸들의 페인트 일부가 벗겨지고, PT나사와 몸체에서 녹이 국부적으로 형성되어 있지만, 가스누출 안전성에 영향을 미칠 정도는 아니었다. 또한, 탈거한 밸브에서 가스누출은 발생되지 않았다. 다만, 밸브스템의 영구변형과 오링의 마찰표면 일부에서 손상이 관찰되었다. 따라서, 탈거된 밸브의 가스누출 안전성을 보장하기 위해서 밸브시트와 오링 교체하는 것이 바람직함을 알 수 있다. 또한, 핸들의 조임력을 주기적으로 점검하는 것이 필요함을 알 수 있었다. This paper presents an experimental study on the safety of a valve for a special gas cylinder. The test valves that were randomly dismantled from the special gas cylinder were experimented on the gas leakage and operation safeties. The crack, wear and deformation of the valve body, screw thread, safety disk, vent hole, stem and handle components that may affect to the gas leakage safety of a used valve were not found in this experimental study. A painted handle of a valve was partly stripped from the coated surface, and the surface of PT screw of a used valve body was rusted. But, these paint and rust problems do not affected to the gas leakage safety of used valves. And there was no gas leakage in the dismantled valve, and the permanent deformation and partial scars of a valve stem and O-rings were observed on the rubbing surfaces. Thus, the valve seat and O-rings are recommended to be replaced for a gas leakage safety of a dismantled valve. And it is necessary to repair and inspect handle fastening forces for a safe opening and closing operations of a valve.

Rolling of a transport barge in irregular seas, a comparison of motion analyses and model tests

With sea transport of heavy objects in focus, model tests of a barge in irregular waves have been performed. Securing the transported object to the deck of the barge is of vital importance, and an optimum load level to be used in the structural design is desirable. The aim is to investigate methods for predictions of barge roll motion and related sea fastening forces. Response from linear and non-linear numerical analyses is compared with results of model tests. It is found that the numerical analyses give slightly conservative results, and that the nonlinear time-domain analyses gives only marginally more accurate results than the linear frequency domain method.

Design of New Fixture for Standardized Cutter

In view of present situation that fixture for standardized cutter can install only one specification of standardized cutter and center height of cutter blade must be calibrated by gaskets, a new-style multi-functional fixture was designed which can clamp various specifications of standardized cutters and be adjusted more precisely and easily by screws. The main design contents include general structure of fixture, installation space of cutter, harford vertical adjusting mechanism, cutter lateral fastening and screwdown column; lateral fastening force, screwdown clamping force and tighten torque of different specifications of cutters are calculated afterwards. It has been proven by practices that the new fixture has good effects and meets demand of production well.

Investigation of a concrete railway sleeper failed by ice expansion

We investigated a conical crack formed near a fastening bolt of a concrete railway sleeper in a slab track system. The crack initiated from the bottom of the sleeper and penetrated the sleeper completely forming a conical shape. To study the reason for this and to examine the failure mechanism, we used a three dimensional finite element method and a series of experimental programs. The result of the numerical simulation was verified with the experimental data. From this study, we concluded that the conical crack was caused by the volume expansion of the freezing water leaking into the plastic insert of the fastener hole. The effect of location of the frozen insert holes, initial fastening force and compressive strength of concrete on the freezing force was also studied in this study.

Does Competitive Strategy Protect Companies from Intellectual Property Free Riding?

Companies with a distinct competitive strategy are attractive targets for free riding of intellectual property (IP) as copying their products either provides high margins (differentiation) or opens large markets (cost leadership). However, a clever combination of a competitive strategy with a suitable IP strategy and management can protect a company from IP free riding. Our findings suggest that cost leaders should use legal protection methods and ensure the enforcement of these methods. Differentiators should keep their knowledge and technology secret so as to mitigate the imitation enabling effect of technical intellectual property rights (IPR). Trademarks and registered designs are effective tools for companies of both competitive strategies. Policy should improve the effectiveness of IPR regimes allowing easy and fast enforcement of patents.

S116023 ねじの摩擦係数の簡易測定法 : 摩擦係数とトルク係数の評価

Although giving proper fastening force to the screw fastener of a machine part is important, it is not easy to determine it. Therefore, there are several the fastener control methods and an especially comparatively easy torque method is mostly used among them. The torque method is affected by the friction of a contact part, and fastener is performed using the torque coefficient as an index. In this report, the equipment which doesn't depend on an expensive fastener testing machine is devised and made. Then the coefficient of friction of a thread face and bearing surface part, which governs a torque coefficient, is measured and calculated.

J045013 金属・CFRP平板ボルト継手の初期締結力がCFRP面接触部の滑り及び内部応力へ与える影響

J045013 金属・CFRP平板ボルト継手の初期締結力がCFRP面接触部の滑り及び内部応力へ与える影響

Fretting Fatigue Behavior of Riveted Al 6XXX Components

The riveting is widely used for fitting together two or more elements of structure in the same or different materials. In these assemblies the stress field is complex, we have to consider the effect of the geometrical discontinuity, the contact, the tightening, the material properties and the applied load. The current work focus on the study of fretting fatigue crack formation in common 6XXX aluminum alloys, used in land transportation equipments, and uncovering characteristic origins of crack by experimental and numerical methods based on multi-axial fatigue life models. 3D finite element models were validated by the experimental results obtained with strain gauges. The influences of the contact friction coefficient at the fretting surface, the fastening forces and the remote stress applied in the fretting fatigue experiments on the crack origins are discussed by the comparison of the different numerical results.

A Fundamental Study on Static Strength Improvement of CFRP Bolted Joints by Increasing Friction Force

The bolted joint is a common assembling method for carbon fiber reinforced plastic (CFRP) members. However, cracks or plastic deformation can occur around bolt holes of CFRP members even when employing low fastening forces. As a result, CFRP failure occurs around bolt holes because of bearing forces, and the strength of a CFRP joint is reduced. To address this problem, we change the configurations of washers and insert a thin sheet having a high friction coefficient between CFRP members. In friction coefficient measurements, the insertion of sandpaper was found to be the most suitable method for increasing friction forces at the interface between CFRP members. Three-dimensional finite element method analyses were conducted to investigate the effect of washer configurations in terms of the maximum allowable fastening force and the joint strength. From these analyses, the cone washer was found to be the most effective design for increasing the joint strength. In the full model analyses, the failure strengths of proposed CFRP bolted joints were higher than those of normal CFRP bolted joints. The verification tests for the proposed joint were conducted according to ASTM D5961. It was observed that the load at failure for the proposed bolted joint was about 45 % greater than that for the conventional joint.

J0405-1-5 軸力増加と摩擦係数増加によるCFRPボルト継手の静的強度向上に関する研究(知的材料・構造システム(1) 複合材料関連)

One of the major fastening methods for the CFRP members used in aircrafts is bolted joint. CFRP bolted joints, although, have the problem that damages are occurred around bolt holes of CFRP, even by the tightening with low fastening force. As a result, the fastening force of conventional CFRP bolted joints is very low, and these strengths become decreased. In order to improve this weakness, configurations of the washers are changed in this study to increase the fastening force without CFRP damage, and thin sheet with high friction coefficient is sandwiched between CFRP members in this study to improve the friction force. In the validation testing, the failure strength of the proposal CFRP bolted joint become higher than normal CFRP bolted joints.

ＭＯ型フランジの加速器ビームダクトへの応用

The MO-type vacuum flange, which can provide a gapless connection between flanges, was studied experimentally aiming to apply it to the beam duct of high-current accelerators. A test flange showed a good vacuum sealing property although the flange had a complex aperture, that is, a combination of a circle and a rectangle. The vacuum sealing was successfully achieved with a reasonable fastening force, and was kept even after a baking at 250°C for 24 hours. The structural analysis well reproduced the observed deformation of flange, and utilized to optimize the flange structure. The MO-type vacuum flange was found to be a promising one for the connection flanges of the beam duct with a complicated aperture in the future accelerators.

Pre-Step and Post-Step Deformation Schemes for Fastening Band-Shaped Twisted Cloth

We have developed a simulation program that presents the process of fastening band-shaped cloth objects. These objects are twisted in 3D space to mimic the movements of tying garments such as Kimono sash. Even using extensive collision handling, this simulation is tough. The difficulty lies in the complex object contacts: The movements of different parts of a long contiguous deformable object conflict with each other causing numerous collisions during fastening process; Such collisions cause implausible deformations; Moreover, the collisions in different angles are prone to fatal penetrations that are not simple to remove. We propose three schemes to solve these problems. One is a pre-step mechanical scheme for calculating fastening force to move the object smoothly. Other two are a post-step geometrical correction scheme to smooth deformations and a set of schemes to remove penetrations. These schemes proved to enable robust and visually realistic simulations with low cost.

1120 光ファイバセンサによるボルトの軸力計測法

A method for monitoring fastening force-by using a bolt embedded with an optical-fiber sensor (FBG)-has been developed. This method uses the shift of the optical fiber's wavelength that occurs when the metal bolt is subjected to a fastening force. In this study, it was first found that the strain measured by the FBG sensor depends on the adhesive strength of the interface between the optical fiber and the bolt. Secondly, it was found that the adhesive strength can be varied by changing the bore size. To measure the adhesive strength, loading tests were performed on several bolts. Lastly, by estimating a correction factor for the output of the FBG sensor, the actual strain in the bolt could be measured.

Design and analysis of mechanically fastened composite joints and repairs

In this paper, a boundary element formulation is developed to analyze mechanically bolted composite joints and repairs. Boundary equations are formulated for all the member panels of the composite joints/repairs. These equations are solved together with the fastener equations to get the resultant contact forces for all the fasteners involved. The fasteners are modeled as 1-D springs that are governed by linear relationships between the fastener forces and the displacements of member panels at the respective fastener centers. After obtaining the fastener forces from the so-called global analysis, detailed stress analyses are conducted for regions around individual fasteners. The stress distributions around fastener holes are then used to evaluate the margin of safety of the composite panels. The numerical predictions on the fastener forces, failure modes and failure loads of two composite joints using this method agree very well with experimental results. The boundary element formulation presented here is especially suitable for design and analysis of aircraft battle damage repairs where time and facility availability is the prime concern.