Jerzy Kaniowski

Experimental and Numerical Study of Strain Progress During and After Riveting Process for Brazier Rivet and Rivet with Compensator - Squeezing Force and Rivet Type Effect

Experimental and Numerical Study of Strain Progress During and After Riveting Process for Brazier Rivet and Rivet with Compensator - Squeezing Force and Rivet Type Effect The paper presents the experimental and numerical investigation of the stress and strain field around the rivet after the riveting process. The measurements were carried out with the X-ray diffractometer and strain gauges on the sheet surface near the driven head. The axisymmetric and 3D FEM analyses of the riveting process were performed. The article presents experimental and numerical results for two types of the brazier rivets used in the Polish aerospace industry; the normal rivet (BN-70/1121-06) and the rivet with a compensator (OST 1 34040-79 1). Bare sheets made from 2024 T3 aluminium alloy with the nominal thickness of 1,27 mm and rivets with the diameter of 3 mm and 3,5 mm made from Polish aluminium alloy PA25 were used. The measurements were compared with the FEM calculations. The influence of squeezing force as well as the rivet type on stress and the strain system was investigated.

Experimental and Numerical Study of Stress and Strain Field around the Rivet

The paper deals with determination of stress and strain field induced during riveting and FEM modelling of this process. Stress and strain measurements during riveting allow for better understanding the phenomena that occur during this process and to determining stress and strain field which exists in the joint after riveting. The results will be also used for validation of FEM models.

Methodology of Residual Stress Measurements for Rivet Joints

Methodology of Residual Stress Measurements for Rivet Joints The methods and good practice in XRD measurements are presented in this paper. The paper concerns the specimens made of 2024-T3 aluminium alloy plates joint together by rivets. The presented methodology can by divided into two parts: (1) general rules of XRD measurements on 2024-T3 aluminium alloy - choosing the diffraction angle, time of exposure on X-ray radiation, diameter of X-ray spot, etc. and (2) rules applied to riveted specimens - geometrical analysis of the specimen and movements of the goniometer which allow to obtain proper results of stress measurement. Short information about theoretical bases and influence of protective layers on XRD measurement is also included. In the end of the paper the additional equipment called the slit is presented, which allow to perform measurements on flat and cylindrical surfaces with higher resolution.

Methods for Global and Local FEM Analysis of Riveted Joint on the Example of the PZL M28 Skytruck Aircraft

Methods for Global and Local FEM Analysis of Riveted Joint on the Example of the PZL M28 Skytruck Aircraft The paper considers some aspects of FEM modeling of riveted joints with application of shell elements and submodeling technique. Presented works were carried out within Eureka project No. E!3496 called IMPERJA. The goal of the IMPERJA project is to increase the fatigue life of riveted joints. The project assumed FEM modeling of the operating aircrafts structure at three different complexity levels, namely considering the complete structure, a structural detail and a single riveted joint. The paper presents analyses of various rivet models and calculations of a structure and a riveted joint. In the first part examples of various rivet models were presented and usefulness of them was discussed. Influence of the following simplification was analyzed; • neglecting of rivets in a model (elements are jointed continuously) • rivet as a rigid element (MPC) • neglecting of contact phenomenon • neglecting of secondary bending. The basis of the analysis was the asymmetric butt joint model with 14 rivets. The model which took into account secondary bending and contact phenomenon was analyzed as well. In the second part, the example of analysis of riveted joint on a lower skin of the PZL M28 Skytruck aircraft wing was presented. A submodeling technique was used there. At first, part of the wing model, was built. It includes 7 ribs and 6 bulkheads between them. Boundary conditions were taken on a basis of operation data. Presence of rivets was neglected. The Linear material model was used. The purpose of this calculation was to gain accurate boundary conditions for the model of riveted joint on the middle rib. Next a shell model of chosen area was build. Boundary conditions were set on a basis of result from previous analysis. Because of large stiffness difference between part models (part of wing and riveted joint) forces, instead of displacements, were used, as boundary conditions. The nonlinear model of material was used. A contact effect, secondary bending and residual stresses were taken into account. Results from this analysis are planned to be used as boundary conditions in a calculation of single rivet with solid detailed model. The presented method allows analyzing phenomena that appear around a rivet in a real structure, during operation. Analyses were performed with MSC PATRAN and NASTRAN software.

Experimental and Numerical Study of NACA and Conventional Riveting Procedure

Abstract Fatigue behaviour is one of the most important properties of modern airplanes and rivets influence it strongly. According to the literature, the NACA riveting offers a multiple increase in the fatigue life of joints. The aim of this paper is to investigate the benefits offered by the NACA riveting procedure with respect to the residual stress and strain distribution after riveting as well as rivet hole expansion. Experimental and numerical approaches were adopted. The conventional riveting with both the universal and countersunk rivets was compared with the NACA riveting. The countersunk angle and depth in the case of the NACA riveting was modified somewhat relative to the values met in the literature. For these three cases, strain gauge measurements during riveting, hole expansion measurements and FE calculations were performed. The hole expansion measurement with the use of Computer Tomography(CT) was proposed. Only the FE calculations unambiguously indicate better fatigue properties of the NACA riveting. The proposed method of hole expansion measurement requires further research to increase its accuracy.

Comparison of Selected Rivet and Riveting Instructions

Abstract Sheet metal parts are widely used in airframes. Most sheet metal parts used in aircraft assembly are joined using rivets. A number of riveting parameters directly influence fatigue properties of a structure. These include a rivet length, driven head diameter, tolerance of a rivet hole and a rivet shank diameter, and a protective layer among others. Unfavourable selection or change of these parameters can lead to stress concentrations and early crack nucleation. Crack growth can cause failure of a whole structure. The selection of the riveting process parameters is usually described in a company’s internal instruction (process specifications). Some parameters can be defined in an aircrafts technical specifications. Riveting instructions among other production documentation are part of a companys closely guarded know-how. The author obtained access to two riveting instructions used in Poland and three such documents used in western Europe. The author was permitted to publish the comparison of the parameters from these documents but he is not supposed to reveal any other information. For the reasons stated above, the following cryptonyms were used in the article: Poland-1, Poland-2, West-1, West-2 and West-3. The quality of a joint also depends on rivets parameters that are defined in rivets standards. For this reason, selected rivets defined in the Polish and Russian industry standards as well as western standards are compared in this paper. Tolerances of a rivet and a hole diameter, clearances between a rivet and a hole, rivet lengths anticipated for driven head formation as well as driven head dimensions are taken into account.

Calculation and Experimental Verification of Residual Stresses in Riveted Joints Used in an Airframe

Calculation and Experimental Verification of Residual Stresses in Riveted Joints Used in an Airframe This paper presents diffraction measurements of residual stresses around the rivet, formed during the riveting process. The measurements were made with the XSTRESS-3000 diffractometer, manufactured by Stresstech Oy. The measurements were carried out on specimens made of bare sheet 2024-T3 alloy, (standard AMS-QQ-250 / 4). The measurement results were compared with the FEM simulation results. The work was performed under the EUREKA IMPERIA project E! 3496.

Analysis of the Local Phenomena during Riveting Process

The riveting still remains the most popular and basic method of joining metal parts in airframes. At the same time, the rivets are critical from the fatigue point of view. The paper presents the selected investigations of local phenomena during the riveting process. At the beginning, some results from the literature, concerned on the riveting process influence on fatigue of the three-row lap joint were shown. The analysis of these results leads to the conclusion that the increase in fatigue life caused by higher riveting force is so high that the more beneficial residual stress cannot be the only explanation, but the new phenomena in riveting process occurs and it is a reason of huge increase in fatigue life. The working hypothesis has been assumed that during the riveting process adhesive joint (called cold welding) were formed between the rivet shank and the sheets. Several microstructure tests were conducted in order to verify this hypothesis. The tests include riveting the specimens for various configurations and analyses of the microsection of selected specimens with the use of optical and scanning electron microscope. In the case of several specimens the punctual and linear welding between rivet shank and sheets were observed. The paper presents the investigation and selected results. The authors are going to continue presented researches.

Local Phenomena During Riveting Process

Abstract The paper presents experimental and numerical study of the local phenomena during the riveting process. It is commonly accepted that technological factors of the riveting process has a strong influence on the fatigue life of riveted joints. The authors analysed the papers concerned the experimental researches of the riveting force influence on fatigue life. The magnitude of the life increase caused by the riveting force increase suggests the authors that this is not only the result of beneficial stress system but the change of the joint formation mechanism has taken place. This was an inspiration to undertake more detailed researches of the riveting process. The strain progress during the riveting process has been experimentally investigated for four types of aluminium rivets used in airframes. Measurements confirm very high strains near the driven head. For some types of rivets the reversal strain signal has been recorded. Several FE model has been use to investigate the riveting process. The axisymmetric and solid models were used. The agreement of experimental and numerical results in some cases were good, in other cases the numerical models demand further development. In any calculations, the reversal strain effect has not been obtained, This suggest that it is result of the phenomenon which has not been taken into account in numerical modelling. The working hypothesis has been assumed that during the riveting process adhesive joints (called cold welding) were formed and destroyed during the process, what was the reason of the observed reversal strain signal. The authors are going to continue this investigation.

Analysis of the Quasi-Static Riveting Process for 90° Countersunk Rivet

Riveting is the most commonly used method of joining sheet metal components of the aircraft structure. The riveted joints are critical areas of the aircraft structure due to severe stress concentrations and effects such as fretting and secondary bending. The most spectacular and wellknown evident of this was the accident of Boeing B737 of Aloha Airline in 1988, when during the flight at altitude of 7300 m a large part of fuselage skin was removed due to explosive decompression. The investigation showed that the reason for this accident was widespread fatigue damage of riveted joints. This accident was an impulse for establishing many research programs around the world focused on fatigue of riveted joints. In the Netherlands, the University of Technology in Delft was one of active centres where fatigue of riveted joints was a subject of numerous investigations and PhD dissertations, among other the one presented by R.P.G. Müller [1]. He showed that there is strong correlation between riveting force and fatigue life of riveted joints. In the case of three-rows riveted joints assembled with the squeezing force value (driven head dimension) according to the industrial manual fatigue life varied between 39 630 cycles for minimum and 95 200 for nominal squeezing force values. For high squeezing force fatigue life of joint was 446 413 (fig. 1).