BALİSTİK ÇARPMA ETKİSİNİN SONLU ELEMANLAR YÖNTEMİYLE İNCELENMESİ

In this study, dynamic response of exposure to a high-speed impact of Titanium, TI 6%AL4%V and Steel 4340 plates were investigated depending on increasing thickness of plates and the changing impactor geometry using finite element method. The plates were modeled using 200×200 mm size and 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm and 7 mm thickness. The impactor’s material is Steel 4340 and for all analysis it has 350 m/s velocity. Four edges of the plates are fixed and the impact loads applied to center of the plates. Finite element analysis was performed using ANSYS/ Workbench/ Autodyn. As a result, the relation between displacement - thickness and damped energy – thickness are given in graphics.Bu çalışmada yüksek hızlı darbeye maruz Titanyum, TI 6%AL4%V ve Çelik 4340 levhalarının artan levha kalınlığı ve değişen vurucu geometrisine bağlı olarak dinamik cevabı sonlu elemanlar yöntemi kullanılarak araştırılmıştır. Darbe uygulanacak levhalar 200×200 mm ebatlarında ve 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm ve 7 mm kalınlık değerlerine sahip olacak şekilde modellenmiştir. Vurucu malzemesi olarak Çelik 4340 seçilmiş olup bütün analizler 350 m/s’lik çarpma hızlarında gerçekleştirilmiştir. Kullanılan levhalar dört kenarından ankastre olarak mesnetlenmiş ve darbe levhanın merkezine gelecek şekilde uygulanmıştır. Sonlu elemanlar analizi ANSYS/Workbench programı Autodyn modülü ile yapılmış; yer değiştirme-kalınlık ve sönümlenen enerji-kalınlık değişimleri grafikler halinde karşılaştırmalı olarak verilmiştir

Yapıştırıcı Ile Birleştirilmiş Alüminyum Tek Bindirme Bağlantıların Düşük Hızlı Eğilme Darbe Davranışının İncelenmesi

Konferans Bildirisi-- İstanbul Teknik Üniversitesi, Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2017Conference Paper -- İstanbul Technical University, Theoretical and Applied Mechanical Turkish National Committee, 2017Bu çalışmada yapıştırıcı ile birleştirilmiş tek bindirme bağlantıların düşük hızlı eğilme darbesi altındaki davranışları dinamik sonlu elemanlar analizi ile incelenmiştir. Sonlu elemanlar analizleri ABAQUS/Explicit sonlu elemanlar paket programı ile yapılmıştır. Bindirme bağlantısını oluşturan yapışan malzemelerin sonlu elemanlar modelinde Al 6061-T6, yapıştırıcı modelinde ise Araldite 2015’ e ait mekanik özellikler kullanılmıştır. Yapıştırıcı yapışan ara yüzeyi gerçek şartlara uygunluk sağlamak amacıyla kohezif bölge modeli kullanılarak modellenmiştir. Ara yüzeyler arasında kalan yapıştırıcı orta bölgesi ve yapışan malzemeler ise elasto-plastik malzeme modeli ile modellenmiştir. Bindirme boyu (25 ve 40 mm) ve darbe enerjisi (3 ve 11 J) değişimlerinin bağlantının darbe davranışına olan etkisi incelenmiştir. Çalışmanın sonunda bağlantılara ait temas kuvveti-zaman ve temas kuvveti-yer değiştirme grafikleri sunularak bağlantı tipleri değişken parametrelere göre karşılaştırılmıştır.In this study, the behaviors of adhesive-bonded single lap joints under low-speed bending impact were investigated by dynamic finite element analysis. Finite element analyses were performed with ABAQUS/Explicit finite element software. The mechanical properties of Al 6061-T6 were used in the finite element model of the adherend materials, and mechanical properties of Araldite 2015 were used in the adhesive finite element model. The adhesive-adherend interface was modeled using the cohesive zone model to be compatible with the actual conditions. The middle region of the adhesive between the interfaces and the adherend materials were modeled by the elasto-plastic material model. The influence of the overlap length (25 and 40 mm) and impact energy (3 and 11 J) changes on impact behavior was investigated. At the end of the study, contact force-time and contact force-displacement graphs of the joints were presented, and the joint types were compared according to the variable parameters

Experimental Investigation of Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints

Determining the impact behavior of adhesive joints allows the designing of high-strength joints. Therefore, the dynamic behavior of adhesive joints has recently become a trending research topic. The study aims to examine the impact behavior and damage mechanism of the adhesively bonded composite joints, taking into account different impact angles. The mechanical behavior of adhesively bonded glass-fiber reinforced laminated composite single-lap joints under bending impact load was experimentally determined via a drop weight impact test machine. The effects of impact angle (theta = 0 degrees, 10 degrees, 20 degrees, 30 degrees), fiber angle (phi = 0 degrees, 45 degrees, 90 degrees), and overlap length (b = 25, 40 mm) on the impact behavior of the joints were investigated. These parameters were determined to affect the impact behavior of the joint and the damage characterization. The highest contact force occurred in the joints with 0 degrees fiber angle having the highest bending strength, and the lowest contact force occurred in the joints with 90 degrees fiber angle having the lowest bending strength. Due to the increase in the impact angle, the maximum contact force value in the joints decreased, while the total contact time increased. The increase in overlap length had little effect on the maximum contact force and total contact time, and the vertical displacement decreased due to the increasing bending stiffness. The unbalanced joint with 45 degrees fiber angle was forced to rotate around its axis due to in-plane unbalanced shear stress distributions induced by the bending impact load. The unbalanced shear stress distribution caused shear damage at the fiber-matrix interface and the top composite-adhesive interfaces. In joints with 0 degrees fiber angle, the impact energy was mostly met with adhesive damage, while the composite adherend was damaged as a result of increased shear stresses in the matrix region for the joints with 90 degrees fiber angle

Finite Element Analysis of Low-Speed Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints

The development of a realistic numerical model that predicts the impact behavior of adhesively bonded composite joints is important for many industrial sectors such as automotive, aerospace, and marine. In this study, it was aimed to develop a numerical model that can predict the low-velocity oblique impact behavior of composite single-lap joints close to the experimental results. The validation of the proposed numerical model was carried out with the results of the previously experimentally tested joints. In explicit finite element analysis, the orthotropic material model and Hashin’s damage criterion were used in the numerical model of composite adherends. The adhesive region was divided into three different regions. The cohesive zone model (CZM) was used to determine the damage initiation and propagation in the upper and lower interface regions of adhesive. The middle region of the adhesive between the two cohesive interfaces was modeled with an elastic–plastic material model to reflect the plastic material behavior of the adhesive in the analysis. The effects of impact angle, fiber orientation, and overlap length on adhesive damage initiation and propagation were investigated in detail. There is a good agreement between the numerical and experimental results, considering the contact force-time variations and composite and adhesive damage. The impact angle and fiber angle had a significant effect on the impact behavior of the composite joints and the adhesive damage initiation and propagation. The increase in impact angle and fiber angle caused a decrease in the maximum contact force value. Adhesive damage propagation patterns varied according to the composite fiber orientation. In addition, since the shear toughness of the adhesive is higher than its tensile toughness, the amount of adhesive damage and damage propagation rate decreased as the impact angle increased

Loading-rate effect on tensile and bending strength of 3D-printed polylactic acid adhesively bonded joints

Additive manufacturing provides the production of many machine parts and components with complex geometries. The adhesive bonding technique can be alternative method for joining parts produced with additive manufacturing. This experimental study investigates the applicability of the adhesive bonding technique for PLA (polylactic acid) adherends produced with additive manufacturing and especially the effects of loading rate on the strength of 3D-printed PLA adhesive single-lap joints under tensile, three-point bending (with shear) and four-point bending (no shear effect) loadings. Both PLA and adhesive tensile test specimens exhibited a better strength but lower failure strain with increasing loading rate. PLA had better mechanical behaviour in the raster orientation than those in the layer-build direction. The strength of adhesive single-lap joints improved slightly with increasing loading rate for the tensile and three-point bending tests whilst a decrease of strength and an improvement of bending stiffness were observed for the four-point bending test. Failure initiated at the free edge of the top adherend-adhesive interface for all tests, and propagated along this interface for both bending tests whilst a sudden through-the-thickness failure of top adherend occurred for tensile load after a small interfacial damage propagation. The failure propagation appeared in a wavy form for the three-point bending test whilst it was along the top adherend-adhesive interface for the four-point bending test. Digital Image Correlation (DIC) method for tensile tests showed that the peeling and shear strains were more critical and concentrated around both free edges of adherend-adhesive interfaces; thus, at the right free edge of the top adherend-adhesive interface and at the left free edge of the bottom adherend-adhesive interface

Low-speed bending impact behaviour of adhesively bonded dissimilar single-lap joints

This study investigates the low-speed bending impact behaviour of adhesively bonded dissimilar single-lap joints and the effects of both strength and plastic deformation capability of adherend material on adhesive failure. Dissimilar adhesive single-lap joint specimens, such as Al 2024-T3 (top adherend)-Al 5754-0 (bottom) and Al 5754-0 (top)-Al 2024-T3 (bottom), were tested at two impact energy levels (3 and 11 J) for two overlap lengths (25 and 40 mm). The progressive failure analysis of the adhesive layer was also conducted by the non-linear explicit finite element method. The adhesive layer was modelled with a 3D cohesive layer along with the upper and lower adhesive interfaces and a non-linear continuum adhesive region between two cohesive layers. The continuum adhesive region had elasto-plastic adhesive properties whilst the cohesive layers obeyed 3D cohesive rules. The experimental and predicted contact force-time, contact force-displacement diagrams, axial separation lengths of the failed adhesive region, permanent deflection of the bonded region, fracture surfaces were in good agreement. The strength and plastic deformation capability of adherend materials and impact energy levels affected the progressive adhesive failure behaviour. The proposed finite element model was successful reasonably in predicting the initiation and propagation of the adhesive failure

Low-Speed Oblique Impact Response of Adhesively Bonded Dissimilar Single-Lap Joints

© 2022 American Society of Civil Engineers.Adhesively bonded joints are widely preferred for joining similar and dissimilar materials due to the mechanical advantages they provide. As the demand for the adhesively bonded method increases, it is necessary to determine the behavior of joints under impact loads for joint design. The aim of this study was to investigate the low-speed oblique impact behavior of dissimilar single-lap joints and the effect of plastic deformation ability and strength of the adherends [(Top) Al 2024-T3-(Bottom) Al 5754-0, (Top) Al 5754-0-(Bottom) Al 2024-T3], overlap lengths (25, 40 mm), and impact energy (3, 11 J) on adhesive damage. The behavior of the joints determined by the numerical model under low-speed oblique impact was compared with experimental results. Considering the contact force-time, contact force-displacement, and adhesive damage, the numerical model was reasonably compatible with the experimental results. The damage initiation and propagation in the adhesive layer were determined by three-dimensional explicit finite-element analysis. In order to obtain suitability for the damage mechanism by observing the experimental bonding damage surfaces, the adhesive region was divided into three zones, the upper and lower adhesive interfaces and a middle adhesive layer between them. The different strength and plastic deformation ability of the adherends had a significant effect on the adhesive damage initiation and propagation. In the case of high strength and low deformation ability of the adherend material (Al 2024-T3) contacting with the impactor, a reduction of the adhesive damage occurred due to the deformation of the adherend material (bottom adherend) with low strength and high deformation capability. The oblique impact load and the different mechanical properties of the adherends greatly affected the adhesive damage initiation and propagation of single-lap joints