Special Fixture Research Articles

Design and fabrication of special fixture for different weld configurations of commercial pure Titanium sheet in laser beam welding process

Titanium and its alloys have been used in several areas such as aerospace, automobile, marine and medical industries due to its several superior properties from other materials. In Laser Beam Welding (LBW) process, a variety of advantages such as very narrow heat affected zone, high depth to width ratio, high productivity and low residual stress are obtained. In the present study, trials were conducted in commercial pure titanium (Grade 2) material to ensure feasibility and to make different weld configuration such as lap joint and T joint in Nd: YA G single-sided during the laser beam welding process. Distortion and colorization of the welded joints were avoided by providing firm clamping and uniform shielding gas (99% pure industrial argon) using a custom-made fixtures arrangement. Hence, the quality of weld configurations of the lap joint and T joint are investigated in regard to weld morphology.

Special Fixture Design and Precision Measurement of Automobile Flange Fork

Because of structural features and batch job requirements in automotive manufacturing line of automotive flange fork parts, the high requirement about its parts is made in the aspect of four positioning datum hole position degrees. Therefore, it is necessary to consider special fixture when designing and processing its parts to make sure batch production, and precision measurement to ensure product quality. In the actual processing, three generations of special fixtures for processing and production use are designed to make improvement for processing and contrasting, through the process of design, trial processing, size adjustment, fixture precision measure and adjustment. Special fixture size precision adjustment is completed, through modern precision measurement equipment using three-dimensional coordinate measurement, to satisfy the parts processing quality and requirements. At present, this production technology has reference significance to a certain extent in the manufacturing process of automotive fork similar products.

Improved Stretch Formability of AZ31 Magnesium Thin Sheet by Induced {10–12} Tension Twins

In order to improve the stretch formability of magnesium alloy sheets, {10–12} tension twins were introduced by pre-compression along the rolling (RD) and transverse directions (TD) with 1.6%, 3.3%, and 5.4% strain levels. Subsequent annealing at 473 K was conducted for 6 h to preserve twinning lamellae. In order to avoid bending–buckling, a special fixture for thin sheet compression has been developed. In addition, hemispherical tests were performed at room temperature. The mechanical properties were improved, while the Lankford value (r-value) decreased and the strain hardening exponent (n-value) increased as the pre-compression level increased compared with the as-received sheet. The stretch formability was also improved. The Erichsen value was dramatically improved the most, from 2.83 mm in the as-received to 5.36 mm and 6.78 mm in TD and RD pre-compressed 5.4% Mg specimens, respectively, which increases by 89% and 139%. The stretch formability was enhanced much more with the pre-compression along the RD as compared to the TD.

An automated reconfigurable flexible fixture for aerospace pipeline assembly before welding

In order to improve assembly quality and efficiency, reduce reliance on operators’ experience and skills, and satisfy diversified assembly requirements, an automated reconfigurable and flexible assembly fixture for aerospace pipelines prior to welding is designed and implemented. The developed novel fixture is composed of three systems, namely a configuration system, a control system, and a mechanical system. The mechanical system is the fundamental of the fixture and mainly contains a 3-DOF gantry-hoisting platform and a number of 4-DOF locators, which is served to precisely locate and clamp all the tube joints of a pipeline and then to assemble the pipeline together with corresponding tubes. The configuration system is the core of the fixture and is used for configuring the specific fixture based on the 3D model of a pipeline. Using One-Master Multi-Slave control mode, the control system is able to precisely control the mechanical system in accordance with the configuration information, which covers the location and orientation data of all the locators for positioning and clamping tube joints of a pipeline, automatically generated by the configuration system. At last the experimental and shop-floor validation show that the proposed fixture system can significantly improve the assembly quality and efficiency for a variety of pipelines. In addition to aerospace pipelines, this fixture system is also suitable for pipeline assembly from other industries including shipping, vehicle, etc.

Dynamic behavior of top-hat bonded stiffened composite panels: Experimental characterization

Abstract One of the most applications of stiffened composite panels is the marine application. In this study, a new sandwich structure consists of long E-glass fibers reinforced Balsa composites is evaluated. The use of this material in marine applications for long periods and under different environmental conditions leads to degradation of mechanical properties of structures and the adhesive. Therefore, in order to guarantee the best functioning of structures for long time periods, an experimental characterization procedure is required. For this purpose, the dynamic mechanical behavior of top-hat bonded stiffened composite panels used in marine applications is studied. A special fixture was designed and fabricated for the impact testing of stiffened structures. Manufactured specimens were tested until finale failure and the effect of impact velocities on the load-displacement and strain-displacement behaviors are compared. We have also interested to the effect of impact velocity on the dynamic behavior and damage kinetics.

Experimental study on compressive behavior of I-stiffened CFRP panel using fringe projection profilometry

Digital fringe projection profilometry (FPP) was used to study the mechanical behavior and failure mode of an I-shaped stiffened panel of carbon fiber reinforced polymer (CFRP) composites subjected to axial compression. The fabrication process of the I-type stiffened CFRP panel is described in this paper. A special fixture was designed and fabricated to apply a compressive load to the CFRP panel. Furthermore, strain gauges and the FPP technique were used to monitor the failure process of the panel when compressed. Strain measurement results revealed that a bifurcation phenomenon appeared on the panel surface. Moreover, full-field deflection results indicate that local skin buckling occurs on the stiffened CFRP panel, which can be used to explain the strain bifurcation. Results from the experiment show that the design and fabrication process of the stiffened panel is reasonable and can be used to study the failure mechanism of stiffened CFRP panel.

Principal Stress-Based Equation for Multi-Axial Fatigue Analysis of Preloaded Threaded Fasteners

A novel principal stress-based high cycle fatigue (HCF) model is proposed for preloaded threaded fasteners under cyclic tensile-shear loads. The model uses the fastener principal stress amplitude in order to construct a singular multi-axial S–N curve from the conventional uniaxial S–N curve with zero mean stress of bolt along with some experimental data. An material testing system (MTS) fatigue testing system is used first to generate the fastener preload by applying a direct tensile-shear load using a special fixture. Subsequently, the same system is used for applying combined cyclic tensile-shear loading of the fastener at various levels of mean stress. Results show that for the same level of axial stresses, the multi-axial loading would significantly reduce bolt fatigue life as compared to that of uniaxially loaded bolt. Moreover, only one S–N curve would be able to predict the multi-axial HCF of preloaded threaded fasteners, when the maximum principal stress amplitude is used. Detailed discussion of the proposed model results and test data are provided.

Fracture Toughness Evaluation of S355 Steel Using Circumferentially Notched Round Bars

In engineering applications, steels are commonly used in various areas. The mechanical members are exposed to different loading conditions and this subject can be investigated in fracture mechanics. Fracture toughness (KIC) is the important material property for fracture mechanics. Determination of this properties is possible using a compact tension specimen, a single edge notched bend or three-point loaded bend specimen, which are standardized by different institutions. Researchers underline that these standardized methods are complex, the manufacturing process is difficult, they require special fixtures for loading during the experiment and the test procedures are time consuming. Alternative methods are always being sought by researchers. In this work, two different approaches are investigated for S355 steels. In the first method, a circumferentially cracked round bar was loaded in tensile mode and pulled till failure. Using suitable equations, fracture toughness can be calculated. In the second method, a circumferentially notched bar specimen without fatigue pre-cracking was loaded in a tensile machine. By means of fracture load values, fracture toughness was determined by the proposed equations. It can be stated that these two different approaches for calculating fracture toughness are simple, fast and economical.

Simplification of High Temperature High Pressure Equipment and Technique for Advanced Materials Processing

Combining pressure and temperature for material processing remains a challenge; if combined and applied, the potential is high for advanced material processing. In addition to advanced powder materials processing and syntheses, complicated fabrications such as joining of dissimilar materials for aerospace, pressure assisted sintering are possible with combined high pressure high temperature technique. In this study, a simplified version of high pressure high temperature equipment is designed and built. The new system eliminates/simplifies complicated and costly equipment such as hot isostatic press. The system has capacity to apply maximum gas pressure of 100 MPa and attain temperature up to 1050 °C. In addition, different processing atmospheres (inert, reducing and vacuum) are possible in the system. Special purpose jigs and fixture are designed to accommodate various processes of synthesis, sintering, joining, hot isostatic pressing and densification etc. Sintering of powder compacts and loose powder were carried out to prove the system.

Evaluation of Mode-I Fracture Toughness for Composite Laminate-Epoxy-Glass Fiber

The conventional materials fail to meet the requirements of high technology applications like space. Applications. In order to meet the requirements like high temperature and wear resistances new materials are being searched. The composite materials are the best alternative for those applications. The applications of composite materials have recently increased because of high strength/stiffness for lower weight, superior fatigue characteristics, facility to change fiber orientations, etc. At the same time, these materials pose new problems such as inter ply cracking, inter laminar de-lamination and fiber cracking. Composite materials failure can be reduced by increasing fracture toughness. Our aim is to evaluate the fracture toughness of glass fiber/epoxy composites. Composites were prepared with glass fiber reinforced with epoxy based polymer. The fracture toughness of the specimen was employed to conduct mode-I fracture test using special loading fixtures as per ASTM standards of DCB5528 specimen.

洗い落し式便器用特殊器具排出管の特性に関する研究 （その2）封水損失に及ぼす影響

洗い落し式便器用特殊器具排出管の特性に関する研究 （その2）封水損失に及ぼす影響

洗い落し式便器用特殊器具排出管の特性に関する研究 （その3）汚物排出・搬送性能

洗い落し式便器用特殊器具排出管の特性に関する研究 （その3）汚物排出・搬送性能

Experimental and numerical investigation of the strain rate-dependent compression behaviour of a carbon-epoxy structure

The usage of fibre-reinforced composites in automotive body structures is still a rarity. The main goal in body structure development is to design lightweight structures as cost-efficient as possible. This research contributes to the approach of maximal material usage by considering the strength increase of a carbon-epoxy laminate with increasing strain rate. The objective was to substantiate the well-known material characteristic’s strain rate dependency from a coupon level to realistic body structure component – experimentally and numerically. Hence, a special compression fixture was developed to obtain all necessary characteristic values of the investigated T700S DT120 prepreg system. The rectangular coupon specimens were loaded with quasi-static to intermediate strain rates (2×10-4 to 70s-1). A second compression fixture was developed to axial load omega cross-sectional specimens with strain rates from 2×10-4 to 5s-1. The experimental tests showed a significant increase of +23% and +21% in compression strength for rectangular coupon specimens and omega cross-sectional components, respectively. Furthermore, the numerical simulation showed the same increase in strength of +21% for omega cross-sectional components. This work has proven the necessity of considering the strain rate dependency of a composite material to accurately predict the maximum load capacity of a structure during a dynamic load event like a crash.

RETRACTED ARTICLE: Assembly sequence planning method based on particle swarm algorithm

In the paper, PSO algorithm is used to solve the assembly sequence planning problem. According to the analysis and extraction of fixture assembly information, a complete and correct fixture assembly model is established in which PSO algorithm is introduced, including assembly direction matrix, interference matrix, sequence-relation matrix, etc. Taking shorten the assembly time as the optimization goal, the feasible assembly sequences for specific fixture are obtained using PSO algorithm and the optimal assembly sequence is found. The influence of main factors on PSO algorithm is analyzed. With the increase of population, the chance to find the optimal solution increases. When $$\upomega $$ and $$\hbox {c}_{1}$$ increase and $$\hbox {c}_{2}$$ decreases, it is good for global searches of the PSO algorithm. When $$\upomega $$ and $$\hbox {c}_{1}$$ decrease, and $$\hbox {c}_{2}$$ increases, it is good for local searches of the PSO algorithm. In practical applications, the factors should be adjusted according to specific problems.

Improving spur gear microgeometry and surface finish by AFF process

ABSTRACTThis paper describes improving microgeometry and surface finish of spur gears by abrasive flow finishing (AFF) by experimentally identifying optimum values of finishing time and AFF medium viscosity. An experimental apparatus was developed for gear finishing by AFF using a medium of silicon carbide as abrasives, silly putty and silicone oil as blending agents. A special fixture was developed comprising of two metalon cylindrical disks having circumferential holes for back and forth movements of AFF medium between two adjacent flanks of 20MnCr5 alloy steel spur gear teeth. Twenty experiments were conducted varying AFF medium viscosity at four levels and finishing time at five levels to study their influence on error reduction in total profile, total lead, total pitch, runout, and average surface roughness. Results showed considerable reduction in the microgeometry deviation and surface roughness with AFF medium viscosity increase and existence of optimum finishing time for attaining maximum improvement in microgeometry and surface finish. Consequently, 25 min and 135 kPa. s were identified as optimum values and corresponding gear’s microgeometry and microstructure were studied. It revealed that AFF-finished gear flank surfaces are free from cracks, cutter marks, thermal distortions. This proves AFF as economical and productive alternative for gear finishing.

ADHESION OF BIOCOMPATIBLE TiNb COATING

Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering). Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.

Experimental and numerical determination of critical stress intensity factor of aluminum curved thin sheets under tensile stress

We determined the fracture toughness of aluminum curved thin sheets using tensile stress tests and finite element method. We applied Linear elastic fracture mechanics (LEFM) and Feddersen procedure to evaluate stress intensity factor of the samples with central wire-cut cracks and fatigue cracks with different lengths to investigate the notch radius effect. Special fixture design was utilized to establish uniform stress distribution at the crack zone. Less than 9 % difference was found between the wire-cut and the fatigue cracked samples. Since generating central fatigue crack with different lengths required so much effort, wire-cut cracked samples were used to determine critical stress intensity factor. Finite element analysis was also performed on one-quarter of the specimen using both the singular Borsum elements and the regular isoparametric elements to further investigate fracture toughness of the samples. It was observed that the singular elements presented better results than the isoparametric ones. A slight difference was also found between the results obtained from finite element method using singular elements and the experimental results.

A Study on a Composite Laminate Pull-through Joint

In this paper, composite laminate pull-through resistance was analyzed using the FEM method and compared with test results. 2D and 3D simplified FEM models, a nonlinear analysis, and a progressive failure analysis utilizing three composite laminate failure theories Maximum Stress, Maximum Strain, and Tsai-Wu were used to predict the FEM results with the test results. The load and boundary conditions of the test were applied to the FEM to simulate the test. A composite laminate pull-through test (ASTM D7332 Proc. B) was designed with a special fixture to collect more precise data. The test results were compared with the FEM analysis results.

Experimental study on the fracture capacity and fatigue life reduction of the tensioned cracked plate due to the local buckling

Using a special fixture, the effect of symmetric, and for the first time, anti-symmetric buckling on the fracture and fatigue behaviour of tension cracked plates was studied experimentally. A subroutine was also developed in ABAQUS environment to model the fatigue crack growth in presence of the buckling. Results showed that the buckling can reduce the fracture capacity and the fatigue life by 35% and 59% respectively. The anti-symmetric buckling has more effect on the fracture capacity loss due to mix mode of I-III but it has an opposite effect on the fatigue crack growth due to the sliding crack closure.

Design of a Machine for Assembling the Buffer Components in the Concealed Hinge

This paper introduces the structure design of an assembling machine for the buffer components in the concealed hinge. In view of modular design, the machine consists of several modules: the framework module, delivering module, controlling module, station changing module, riveting module, riveting workbench module, unloading module and so on. These modules are arranged in assembly line. We also designed a special clamping fixture to assist locating four preparing assembled components accurately. The whole machine is controlled by a PLC(programmable logic controller) or a SCM(single chip microcomputer), to enable automatic assembly, including locating the preparing assembled components, delivering flat head rivets, riveting, and changing stations and so on. Moreover, the machine can be operated by one worker to save labor, and the operating parameters can be adjusted.