Allowable Load Assessment in Metal-Composite Double-Lap Joint / Avaliação de Carga Permitida em Junta de Dupla Folga Metal-Composto

This work consists of evaluating the tensile and compression static allowable stress of a hybrid (metal-composite) riveted joint. The analyzed joint is composed by two sheets of 2014 – T6 aluminium alloy and a T300/5208 Graphite/Epoxy quasi-isotropic laminate, which were joined by twelve Lockbolt Swaged Collar rivets titanium alloy Ti–6Al–4V annealed. The joint was analyzed through a computational model developed using the Finite Element Method (FEM), with the fasteners modelled through the Multi - Springs technique. This method was widely used to simulate the mechanical behaviour metal-metal and composite-composite parts of the joint. It is validated comparing its results with analytical results of metallic joints available in the literature. Through this model, both the allowable load and its distribution in the fasteners of the joint were determined. Since the evaluated joint is subjected to double shear and, therefore, has no eccentricities, the presence of secondary bending was not observed, the bearing and bypass loads were the most relevant in evaluating the allowable loads of the joint. The load distribution in the joint and its components’ safety margin was determined, with the laminate being the limiting component of the allowable load.

RANCANG BANGUN KONSTRUKSI BODI PADA AUTOMATIC WELDING CARRIER MACHINE

Manually system welding process still widely used and have a deficiency in it. Which work is accident often occur in it, the unstable arc of fire and quality of welding product still depends on the welder ability. The purpose of this study is to design a portable robotic welding tool equipped MIG(Metal Inert Gas) welding tool to support automation in the welding process. Mobility and work range of tools is supported by light and strong material and designed with relatively small dimensions and equipped leg robotics which is useful to adding work range of the tool in every single welding process. This study using experimentally and simulations methods in body construction and empirical calculation to know relevantly the result and simulation process. And the data obtained after calculating with imposition 98 N, pressure stress on the body is 3334 Pa, which is smaller than the Modulus of Elasticity Aluminum alloy type 5052, moreover, materials used are capable and safe. The riveted joint of the extensions of the body has fracture resistance 2,8 kN and used efficiency of 70% moreover this kind of extensions are efficient to apply on Automatic Welding Carrier Machine’s body.

EFFECT OF THE RIVET-HOLE TOLERANCE ON THE STRESS-SEVERITY FACTOR

This work is focused on a quantitative procedure for estimating the generally unfavourable effects that incorrectly drilled holes, characterized by the initial clearance between a rivet and a hole, have on the fatigue life of riveted joints. The solution is based on an analytical approach using the stress-severity-factor concept. An experimental programme with riveted-joint specimens characterized by low-load transfer factors was realized in the Czech Aerospace Research Centre (VZLU) test lab under constant amplitude loading. The holes for rivet joints with 4-mm diameters were prepared with the clearance in a range of 0.0–0.16 mm. Force-controlled riveting was applied using a constant pressure force to form the driven head. To prevent fretting events between the joined parts, their anodized contact surfaces were lubricated with MOLYKA, plastic grease with molybdenum disulphide and graphite. The experimental data showed that the load-transfer factor and the fatigue life depend on the initial clearance between a rivet and a hole. The presented procedure introduced the hole-filling factor, integrated in the stress-severity-factor concept as a function of the initial clearance between a rivet and a hole.

Progressive Failure Analysis of Composite/aluminum Riveted Joint Subjected to Pull-through Loading

The progressive failure mechanism of composite/aluminum riveted joint subjected to pull-through loading was investigated by experiments and finite element method. The pull-through tests were conducted and its load-displacement responses were analysed. A progressive damage model based on the Hashin-type criteria and zero-thickness cohesive zone method was developed by VUMAT subroutine, which was validated by both open-hole tensile test and three-point bending test. Load-displacement response, failure modes and damage propagation were analysed and compared with the experimental results. Major conclusions: 1) there are 4 obvious characteristic stages on the load-displacement curve: first load take-up stage, damage stage, second load take-up stage and failure stage; 2) relative error of stiffness, first load peak and second load peak between finite element method and experiments were 8.1%, -3.3% and 10.6%, respectively; 3) specimen was mainly broken by rivet-penetration fracture and delamination of plies of the composite laminate; 4) the material within the scope of the rivet head is more dangerous with more serious tensile damages than other regions, especially for 90° plies.